Heat Treatment of Metals

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Development outline 2035 of China heat treatment

Heat Treatment of Metals 2025, 50 (1): 1-5.

Abstract （76）

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Microstructure of 11%Cr ferritic/martensitic steel in normally heat-treated state before and after irradiation

Wo Jianxing, Shen Yinzhong

Heat Treatment of Metals 2025, 50 (1): 6-11. doi:10.13251/j.issn.0254-6051.2025.01.001

Abstract （109）

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The microstructure of 11%Cr ferritic/martensitic steel in the normally heat-treated state before and after irradiation was experimentally studied by using transmission electron microscopy and energy dispersive spectroscopy. The results show that the primary microstructure of the 11%Cr ferritic/martensitic steel before and after irradiation consists of tempered martensitic along with a small amount of δ-ferrite. Before irradiation, a small amount of precipitates with a relatively small size are present at martensite boundaries and within martensite laths. Some irregular, blocky, large black particles are present at the interface of δ-ferrite and matrix. There are no precipitates within δ-ferrite grains. After irradiation, a large number of rod-like and blocky precipitates appear at the boundaries and interior of the martensitic lath, while the number and size of precipitates significantly increase compared to that before irradiation. The number of irregular blocky black particles at the interface of δ-ferrite and matrix increase compared to that before irradiation. Inside the δ-ferrite, a large number of blocky and needle-like precipitates are formed which may be Cr-rich nitrides, Cr-rich carbonitrides and Fe-W type precipitates. After irradiation, the precipitates inside the martensitic laths are Cr-rich M₂₃C₆ phase. Compared with the Cr-rich M₂₃C₆ phase before irradiation, the Cr and Ta contents in the M₂₃C₆ phase slightly decrease, while the Fe and Nd contents slightly increase after irradiation. However, overall, the changes in the average metal element composition of the Cr-rich M₂₃C₆ phase are relatively small.

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Microstructure and properties of high-strength corrosion-resistant Fe-based medium entropy alloys

Dai Chunduo, Li Jiangwen, Guo Chengyu, Zhang Yong, Sun Meihui, Li Tianyi, Gong Li, Pan Yue

Heat Treatment of Metals 2025, 50 (1): 12-21. doi:10.13251/j.issn.0254-6051.2025.01.002

Abstract （68）

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Using Python language to edit Thermal-Calc instructions for efficient calculation of alloy phase composition, two iron-based medium entropy alloys with L2₁ precipitation ratio greater than 15% were obtained according to design principles. Adopting large deformation cold rolling combined with medium temperature aging process for microstructure control to achieve excellent strength plasticity matching. The results show that the tensile strength and elongation of No.1 alloy are 1592 MPa and 17.50%, respectively, while that of No.2 alloy are 1682 MPa and 13.50%, respectively. At the same time, both the alloys form stable passivation films in a 3.5wt% NaCl solution, with a pitting potential close to 0 V(vs SCE) and good corrosion resistance. The main matrix phase of the two alloys is FCC solid solution, with a small amount of BCC phase. The combination of large deformation cold rolling and medium temperature aging results in the alloy having an incomplete recovery of fine grain structure, accompanied by the formation of multiphase and multi-scale precipitation phases, which form a soft and hard coordination with the FCC matrix to improve the strength and plasticity of the alloy. The combined effect of precipitation strengthening, dislocation strengthening and grain refinement strengthening enhances the strength of alloys. The high plasticity of the alloy is due to the relief of stress concentration during medium temperature aging. The good plasticity of the FCC matrix can effectively slow down the formation and propagation of cracks. In addition, the low mismatch between Heusler_L2₁ phase and the matrix can also slow down the formation of microcracks at the phase boundary, allowing the two medium entropy alloys to maintain high plasticity.

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Research progress of κ-carbide in Fe-Mn-Al-C low density steels

Li Changhao, Liu Zhi, Zhang Xiaofeng, Yang Yong, Zhou Huasheng, Zhao Xinlei

Heat Treatment of Metals 2025, 50 (1): 22-30. doi:10.13251/j.issn.0254-6051.2025.01.003

Abstract （69）

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As a new generation of automotive steel, the Fe-Mn-Al-C system low-density steel is a potential material for future automotive light-weighting research due to its advantages of high strength, low density, and good plasticity and toughness. As a result of κ-carbide affect the comprehensive mechanical properties of the steel, the characteristics and formation mechanism of κ-carbides in Fe-Mn-Al-C low-density steels and the effect of differences in the content of alloying elements on κ-carbides were expounded, and the effect of solution and aging treatments on κ-carbides and the effect of κ-carbides on the toughening mechanism were described in detail. It is concluded that the mass fraction of Al and Mn in Fe-Mn-Al-C steel should be reasonably controlled to provide driving force for κ-carbide precipitation, and the solution treatment temperature should be 900-1100 ℃, after which the aging should be carried out in the range of 450-600 ℃, and the aging time should be 1-2 h, to avoid the precipitation of coarse κ-carbides at the grain boundaries to deteriorate the material properties.

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Effect of heating time on surface oxidation and decarburization of 60Cr13 stainless steel cutting tools

Ji Xianbin, Pan Jixiang, Li Zhaoguo, Wei Haixia, Qian Zhangxin

Heat Treatment of Metals 2025, 50 (1): 31-35. doi:10.13251/j.issn.0254-6051.2025.01.004

Abstract （57）

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Effect of different heating time (20, 40 min) on surface oxidation and decarburization of 60Cr13 stainless steel cutting tools at 1050 ℃ was studied. The results show that at heating temperature of 1050 ℃, a longer holding time results in severe internal oxidation and grain boundary oxidation on the surface of the 60Cr13 stainless steel cutting tools, with an oxide layer thickness of 15-17 μm. In addition, extending the heating time intensifies the oxidation reaction in high-temperature environments, the oxygen continuously diffuses into the interior of the steel, while the carbon atoms in steel migrate outward. Due to the diffusion rate of carbon atoms exceeding the oxidation rate, the surface decarburization process is intensified, reducing the carbon content in the surface layer, resulting in a decrease in the surface hardness of the 60Cr13 stainless steel cutting tools.

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Effect of vanadium on microstructure and properties of hypereutectoid tool steel

Yang Yu, Wang Tianxiao, Ai Chengshen, Xu Cheng

Heat Treatment of Metals 2025, 50 (1): 36-41. doi:10.13251/j.issn.0254-6051.2025.01.005

Abstract （44）

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In order to study the role of vanadium in hypereutectoid tool steels, microstructure observation, mechanical property test, heat treatment test and abrasive wear test were used to compare and analyze the microstructure and properties of the two hypereutectoid tool steels with and without vanadium after hot rolling and heat treatment. The results show that under the same hot rolling process condition, fine VC particles with a diameter of not more than 10 nm are precipitated in the V-containing steel, the colony size of the pearlite are smaller and with finer lamellar spacing, the yield strength, tensile strength and hardness are 116 MPa, 179 MPa and 3.2 HRC higher than those of the V-free steel, respectively. When tempered at temperatures below 550 ℃, with the increase of tempering temperature, the hardness of the two tested steels gradually decreases and the wear rate gradually increases. Under the same heat treatment process conditions, the hardness of V-containing steel is higher, the wear rate is smaller, and the tempering resistance is better. The tempered hardness at 450 ℃ still reaches more than 53 HRC, and the wear rate is less than 23 mg·km^-1. Tempering at 500 ℃ is a turning point in the deterioration of wear resistance of the V-containing steel. When tempered at 500 ℃ and above, VC particles with a size of above 100 nm precipitate in the V-containing steel, resulting in a significant increase in wear rate and deterioration of wear resistance.

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Magnetic properties and interaction of nanocomposite Nd₂Fe₁₄B/PrCo₅ melt-spun ribbons

Bo Yu, Zuo Jianhua, Wang Hao, Lu Wei

Heat Treatment of Metals 2025, 50 (1): 42-46. doi:10.13251/j.issn.0254-6051.2025.01.006

Abstract （30）

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The nanocomposite Nd₂Fe₁₄B/PrCo₅ melt-spun ribbons were prepared by induction melting and melt-spinning technique, and the effect of PrCo₅ addition on the phase structure, magnetic properties and exchange coupling was investigated. The XRD test results indicate that the ribbons has dual hard magnetic phases of Nd₂Fe₁₄B and PrCo₅, and no oxidation or formation of new phases occur during the preparation process. The content of PrCo₅ has an obvious effect on magnetic properties, and the appropriate addition of PrCo₅ can help improve coercivity. However, the remanent and maximum magnetic energy product decrease with the increase of PrCo₅ content. Research on the recoil loops shows that the "opening" phenomenon of the recoil loops is related to the content of PrCo₅, and the δ_M curve test shows that there is a strong exchange coupling effect in the Nd₂Fe₁₄B/PrCo₅ ribbons. Comprehensive analysis shows that optimal magnetic properties of the nanocomposite Nd₂Fe₁₄B/PrCo₅ ribbons can be obtained at 12%PrCo₅ content, with remanent M_r of 8.73 kGs, coercive H_cj of 11.03 kOe, and the maximum magnetic energy product (BH)_Max of 15.83 MGOe.

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Effect of rare element Ce on microstructure and mechanical properties of 32MnMoNiCu cast steel

Li Jianguo, Jia Dongsheng, Zhao Yinhu, Liu Yubao, Wang Xu, Zhao Leicheng, Lan Yueguang

Heat Treatment of Metals 2025, 50 (1): 47-52. doi:10.13251/j.issn.0254-6051.2025.01.007

Abstract （32）

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By adding rare earth cerium iron alloy in the 32MnMoNiCu cast steel, the effect of rare earth Ce on microstructure and mechanical properties of the cast steel was investigated by using scanning electron microscopy observation, tensile and impact testing methods. The results show that rare earth Ce can refine the ferrite phase, transform inclusions shape from long strip into nodular, and decrease the size of inclusions. Rare earth Ce mainly exists in the form of CeAlO₃, and does not react with MnS inclusions. Precipitation strengthening and fine-grained strengthening which are caused by rare earth Ce in the cast steel result in 12.3% and 23.4% increase in tensile strength and yield strength, respectively. However, the increase fraction of lath ferrite by adding rare earth Ce result in 11.1% and 7.4% decrease in elongation and impact absorbed energy, respectively.

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Hot deformation behavior of TiAl-V-Cr alloy near-α phase region

Liu Hongwu, Gao Fan, Feng Xiangzheng, Li Zhenxi, Dai Songyan, Wang Qingfeng

Heat Treatment of Metals 2025, 50 (1): 53-57. doi:10.13251/j.issn.0254-6051.2025.01.008

Abstract （36）

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Hot deformation behavior and microstructure evolution of Ti-44Al-5V-1Cr alloy deformed near the α-phase region (at 1250 ℃) under different conditions as various initial microstructure, strain rates and deformation were investigated by means of thermophysical simulation, SEM, EBSD and OM characterization. The results show that when the deformation temperature is 1250 ℃, the difference of flow stress variations in initial microstructure of the alloy under identical deformation rate are smaller. However, under the same microstructural condition, the strain rate has a relatively significant effect on the flow stress. As the strain rate decreases, the flow stress decreases noticeably. When the alloy is deformed near the α-phase region, the dynamic recrystallization of α phase is dominant, and the dynamic recovery is supplemented, while the β phase effectively suppresses the growth of α grains. In addition, increasing the deformation can facilitate the refinement of α grain size. After extrusion at 1250 ℃ with a high extrusion ratio, the alloy achieves a fine and uniform fully lamellar structure with average lamellar colony sizes of 12-23 μm.

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Determination and analysis of SHCCT curve of EH36 steel for offshore platform

Wang Chengming, Bai Lijuan, Song Yue, Liu Lijun, Gu Xiurui, Li Huimin

Heat Treatment of Metals 2025, 50 (1): 58-62. doi:10.13251/j.issn.0254-6051.2025.01.009

Abstract （35）

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Offshore platform steel EH36 was taken as the research object, and the welding process of the tested steel was simulated by DIL805L quenching dilatometer. The SHCCT curve of the tested steel was established by means of thermal expansion method combined with metallography method and Vickers hardness test, and the influence of different cooling rates on the microstructure transformation law of the welding heat affected zone was studied. The results show that in the whole cooling rate range, there are four types of microstructure transformation in the HAZ of the tested steel: ferrite+pearlite, ferrite+pearlite+bainite, bainite and martensite+bainite, and the hardness value increases from 164 HV10 to 277 HV10 with the increase of cooling rate. When the cooling rate is lower than 5 ℃/s, the hardness of the HAZ of the tested steel is lower than that of the base metal. In order to ensure that the tested steel obtains good welding joint properties, the cooling rate should be controlled in the range of 10-20 ℃/s (that is, the t_8/5 time is controlled in the range of 15-30 s).

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Microstructure transformation of SCM415H steel for high strength automotive fasteners

Chu Feng, Li Zhanwei, Yu Xuesen, Zhang Jiming

Heat Treatment of Metals 2025, 50 (1): 63-67. doi:10.13251/j.issn.0254-6051.2025.01.010

Abstract （31）

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The phase transformation characteristics of the SCM415H steel for automotive fasteners were studied by thermal simulation. The cooling rate of 0.25 ℃/s produces a microstructure of ferrite and pearlite, while the bainite and martensite occurs with the cooling rate reaches 0.5 ℃/s. The cooling rate of 5 ℃/s results in a microstructure of mainly martensite and bainite, and that of 15 ℃/s or above results in a microstructure of mainly martensite. The pearlitic transformation temperature is 700-575 ℃ during isothermal conditions. The nose tip temperature is about 660 ℃, and completion time of the phase transformation is about 428 s. Based on the tested results, the steel wires with a diameter of 24 mm were successfully produced, and then grade 10.9 automobile fasteners were successfully produced after one spheroidizing annealing and two drawing processes.

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Effect of continuous annealing hot-dip galvanizing process on microstructure and properties of a niobium-containing DP780 steel

Ren Yupeng, Zhang Hesong, Li Shengci, Liu Weipeng, Fu Yujing

Heat Treatment of Metals 2025, 50 (1): 68-74. doi:10.13251/j.issn.0254-6051.2025.01.011

Abstract （38）

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Continuous annealing hot-dip galvanizing process of a 780 MPa grade dual phase (DP) steel was studied by using hot-dip galvanizing simulation testing machine. Effects of four different heat treatment processes as direct quenching, quenching after slow cooling, post-galvanized martensite process and pre-galvanized martensite process on the microstructure and tensile properties of the steel were compared and analyzed. The results show that the slow cooling process after heating in the two-phase region can improve the hardenability of the untransformed austenite and obtain stable island-like martensite. A small amount of tempered martensite is obtained by the pre-galvanized martensite process. The Nb can improve the tempering stability of martensite and improve the mechanical properties of hot-dip galvanized DP steel. There is no significant change in precipitated phases of the steel after the post-galvanized martensite process and the pre-galvanized martensite process, the Nb-rich precipitates are prone to heterogeneous nucleation and precipitation at the interface of TiN precipitated firstly. The tensile strength of the DP steel obtained by the pre-galvanized martensite process is 867 MPa, and the elongation is 21.3%, which is close to the tensile strength (878 MPa) and elongation (24.0%) of the post-galvanized martensite process. However, the yield strength of the DP steel obtained by the pre-galvanized martensite process (564 MPa) is significantly reduced compared to the post-galvanized martensite (611 MPa). Therefore, the pre-galvanized martensite process can effectively reduce the yield ratio and improve the formability of the dual phase steel while ensuring its strength and plasticity.

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Effect of heat treatment on mechanical properties and fatigue properties of 51CrMnV spring steel

Huang Weiming, Zhou Haian, Zhao Qiuhong, Xu Wenbing, Yu Xinhong, Feng Yisheng, Zhang Yunshan, Zhao Ertuan

Heat Treatment of Metals 2025, 50 (1): 75-80. doi:10.13251/j.issn.0254-6051.2025.01.012

Abstract （46）

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Microstructure, mechanical properties, and fatigue property of 51CrMnV spring steel under the processes of 900 ℃×30 min quenching+450 ℃×90 min tempering and 900 ℃×30 min+350 ℃×30 min isothermal quenching were investigated by using optical microscopy (OM), scanning electron microscopy (SEM), universal tensile tester, impact tester, and fatigue tester. The results show that after quenching and tempering, the microstructure of the 51CrMnV steel consists of tempered martensite, and after isothermal quenching, the microstructure consists of bainite, martensite and retained austenite. Compared with quenching and tempering, the mechanical properties and fatigue properties of the 51CrMnV steel treated with isothermal quenching are better, with an increase in tensile strength of 53.6 MPa, elongation of 3.1%, impact absorbed energy of 7.3 J, and fatigue limit of 25 MPa.

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Effect of cryogenic treatment on microstructure and properties of nuclear grade low carbon steel

Xu Ke, Hu Minglei, Zhang Wei, Hu Bin, Li Dongsheng, Liu Rencai

Heat Treatment of Metals 2025, 50 (1): 81-87. doi:10.13251/j.issn.0254-6051.2025.01.013

Abstract （42）

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In order to study the effect of cryogenic treatment on mechanical properties and microstructure evolution of nuclear grade mild steel, the mechanical properties and microstructure of 20 steel after different heat treatments were characterized by means of microhardness tester, XRD, SEM and TEM. The results show that the tempering treatment promotes the transformation of partial retained austenite into martensite and the precipitation of carbon atoms leading to martensite refinement, resulting in an increase in hardness from 468.5 HV0.1 of the quenched steel to 480.3 HV0.1 of the tempered steel. The cryogenic treatment promotes the transformation of the retained austenite into fine lath martensite in the tested steel, and at the same time, the cryogenic treatment causes lattice distortion in the martensite, which leads to the increase of stresses and defects such as dislocations in the microstructure, which in turn promotes the precipitation of carbon atoms in the martensite, leading to the enhancement of precipitation strengthening, resulting in the increase of hardness of the tested steel to 495.3 HV0.1 after quenching-cryogenic-tempering treatment.

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Effects of quenching and tempering temperature on microstructure and mechanical properties of Cr-Mo wear-resistant steel

Li Zhongbo, Hu Haijiang, He Ping, Ren Ke, Yuan Qing, Wu Run

Heat Treatment of Metals 2025, 50 (1): 88-96. doi:10.13251/j.issn.0254-6051.2025.01.014

Abstract （45）

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Effects of quenching temperature and low temperature tempering temperature on microstructure and mechanical properties of a Cr-Mo wear-resistant steel were investigated. The results show that the lath of tempering martensite of the tested steel after tempering is coarsened with the increase of quenching temperature, leading to the decrease of the strength, ductility and toughness. The hardness of the steel after quenching at 1060 ℃ and tempering is higher than that of quenching at 860 ℃ and tempering, which is due to the higher solution strengthening caused by more solution element during quenching isothermal stage. When the quenching temperature is 860 ℃, the strength and toughness first increase and then decreases with the increase of tempering temperature. The optimal tensile strength and impact absorbed energy at -40 ℃ are obtained when tempered at 200 ℃, which are 1607 MPa and 43.9 J, respectively, while the product of strength and elongation decreases to the lowest grade when tempered at 280 ℃. With the tempering temperature further increasing, the strength and toughness increase slightly. When the quenching temperature is 1060 ℃, the strength gradually decreases with the tempering temperature increasing, while the toughness first decreases and then has a little increment. The optimal tensile strength and impact absorbed energy at -40 ℃ are obtained when tempered at 160 ℃, which are 1494 MPa and 45.4 J, respectively.

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Microstructure and mechanical properties of ZL205A aluminum alloy aged under pulsed magnetic field

Zhang Ying, Ma Yonglin, Liu Yongzhen, Xing Shuqing

Heat Treatment of Metals 2025, 50 (1): 97-102. doi:10.13251/j.issn.0254-6051.2025.01.015

Abstract （38）

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Effect of aging under pulsed magnetic field on microstructure and mechanical properties of ZL205A aluminum alloy was studied by means of scanning electron microscope, X-ray diffractometer and universal testing machine. The results show that the pulsed magnetic field increases the vacancy formation energy ΔS_V during the aging process of the ZL205A aluminum alloy, and the atomic diffusion is easier, which leads to the appearance of uniform and fine precipitation phases in the matrix after aging. After the pulsed magnetic field aging treatment (195 ℃×4 h), the tensile strength and elongation are 408 MPa and 11%, respectively. Compared with the conventional aging treatment (155 ℃×9 h) in a factory, the tensile strength is basically the same, the elongation is 64% higher and the aging time is 55% shorter.

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Effect of QLT heat treatment on microstructure and mechanical properties of oil casing steel

Liu Wenyue, Li Tianyi, An Tao, Li Jiangwen, Yang Bowei, Xie Degang

Heat Treatment of Metals 2025, 50 (1): 103-109. doi:10.13251/j.issn.0254-6051.2025.01.016

Abstract （35）

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Microstructure and mechanical properties of a high strength oil casing steel under different heat treatment conditions as hot rolling, quenching at 860 ℃, and quenching at 860 ℃+quenching at two phase region of 800 ℃+tempering at 200 ℃ and 660 ℃(QTL), respectively, were analyzed, and the relationship between microstructure and mechanical properties of the steel after low temperature QLT and high temperature QLT treatment was studied by means of EBSD and TEM. The results show that the microstructure of the hot-rolled steel is granular bainite+pearlite+a small amount of polygonal ferrite. After quenching at 860 ℃, the microstructure consists of lath martensite and a small amount of bainite. After low temperature QLT treatment, the microstructure transforms into tempered martensite and ferrite, the yield strength is 936 MPa, the tensile strength is 1260 MPa, the yield ratio is 0.74, and the impact absorbed energy at 0 ℃ is 40 J, meanwhile, the proportion of LAGB is 34.9%, the dislocation tensity of GND is 10.2×10¹⁴ m^-2, and the equivalent grain size is 1.43 μm. After high temperature QLT treatment, the microstructure transforms into tempered sorbite and ferrite, yield plateau appears in the stress-strain curve, the yield strength is 833 MPa, the tensile strength is 912 MPa, the yield ratio is 0.91, the impact absorbed energy at 0 ℃ increases to 93 J, all of which show best strength and toughness matching, however, the proportion of LAGB decreases to 30.9%, the dislocation density of GND decreases to 9.6×10¹⁴ m^-2, the equivalent grain size decreases to 1.39 μm, which makes the strength of the tested steel decrease and the plasticity increase.

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Effect of quenching process on microstructure and properties of a 500 MPa grade hot-rolled offshore engineering steel

Tuo Chende, Gao Qing, Zhang Yongwei, Shi Shuhua, Feng Zan

Heat Treatment of Metals 2025, 50 (1): 110-118. doi:10.13251/j.issn.0254-6051.2025.01.017

Abstract （36）

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In order to study the main factors affecting the microstructure and low temperature toughness of a 500 MPa grade offshore engineering steel, quenching and tempering process was carried out to explore the effect of quenching temperature on microstructure and mechanical properties of the as-hot-rolled tested steel, and to identify the propagation mechanism of cracks in different microstructure. The results show that the microstructure is dominated by ferrite and martensite after subcritical quenching at 800 ℃ and 850 ℃, and with the increase of quenching temperature, the volume fraction of ferrite decreases. After higher temperature quenching at 910-1010 ℃, the microstructure is completely composed of lath martensite, and the size of martensitic lath increases with the increase of quenching temperature, resulting in the increases of strength, and the decrease of low temperature toughness and uniform elongation. The best heat treatment process for the tested steel to obtain the best strength and toughness is quenching at 910-960 ℃ and tempering at 500 ℃. Most of the cracks in the tested steel originate at the interface of the soft and hard phases in the tempered microstructure, propagate in straight line along the interface between ferrite grains and martensitic laths, and end at the prior austenite grain boundary. The increase of the proportion of large angle grain boundary is helpful to improve the low temperature toughness of the tested steel.

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Effect of intercritical quenching temperature on microstructure and properties of Cr-Mn-Si low alloy steel

Gao Xin, Li Mingdong, Su Jie, Jiang Qingwei, Xia Shihong, Zhang Yongqiang, Ning Jing

Heat Treatment of Metals 2025, 50 (1): 119-125. doi:10.13251/j.issn.0254-6051.2025.01.018

Abstract （33）

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Effects of intercritical quenching temperature on the microstructure and mechanical properties of Cr-Mn-Si low-alloy ultra-high strength steel were investigated by using optical microscope (OM), scanning electron microscope (SEM), tensile tester and impact tester. The results show that when the tested steel is quenched within 790-850 ℃, the carbides gradually dissolve, the ferrite content decreases, the martensite content increases and the strength increases with the increase of quenching temperature within 790-820 ℃. When the quenching temperature is 830 ℃, the ferrite basically disappears, and the strength reaches the peak. When the quenching temperature is ≥850 ℃, the carbides disappear, and the microstructure is mainly composed of martensite+retained austenite, the strength and toughness basically remain unchanged. The best mechanical properties of the tested steel can be obtained by quenching at 850 ℃+tempering at 230 ℃ with the tensile strength of 1770 MPa, yield strength of 1447 MPa, elongation after fraction of 12%, reduction of area of 53% and impact absorbed energy of 71 J.

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Corrosion behavior of a vacuum die-cast aluminum alloy strengthened by cryogenic-solution-aging treatment

Li Zhiqiang, Liu Guanglei, Ding Ran, Xu Fuhai, Tao Cheng, Liu Haixia, Cheng Xiaonong

Heat Treatment of Metals 2025, 50 (1): 126-132. doi:10.13251/j.issn.0254-6051.2025.01.019

Abstract （32）

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Effect of cryogenic-solution-aging treatment on microstructure and mechanical properties of a vacuum die-cast aluminium alloy and its corrosion behavior after immersion in 3.5%NaCl solution for different time were studied. The results show that the cryogenic-solution-aging treatment can effectively improve the mechanical properties of the vacuum die-cast alloy, and the tensile strength is increased from 184.8 MPa to 249.5 MPa, the hardness is increased from 90.3 HV0.1 to 124.6 HV0.1, and the elongation is increased from 6.3% to 7.7%. The cryogenic-solution-aging treatment promotes the α-Al phase, Si phase and Al₅FeSi phase in the aluminum alloy to become fine and distribute evenly, which is conducive to the formation of a denser and more uniform passivation layer during immersion, indirectly hindering the invasion of chloride ions into the internal structure of the aluminum alloy. Compared with the as-cast aluminum alloy, the corrosion progress of cryogenic-solution-aging treated alloy is slow, and the corrosion resistance is significantly improved.

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Effect of aging treatment on properties of graphene/Al-Zn-Mg-Cu alloy composites

Hao Ying, Wang Mingwei

Heat Treatment of Metals 2025, 50 (1): 133-139. doi:10.13251/j.issn.0254-6051.2025.01.020

Abstract （36）

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Al-Zn-Mg-Cu matrix composites reinforced with 0.5wt% GNPs were prepared by vacuum hot pressing sintering and hot extrusion process with Al-Zn-Mg-Cu alloy powder as matrix and graphene as reinforcing phase. The effect of aging treatment on the properties of composites and the strengthening mechanism of graphene on the Al-Zn-Mg-Cu matrix were studied. The results show that the mechanical properties of the composites are the best after aging at 120 ℃ for 24 h, and the tensile strength reaches 505.92 MPa. From the microscopic characterization, it can be seen that the black block second phase in the composite material is the most, mainly graphene and a small amount of precipitated phase after aging at 120 ℃ for 24 h. The reinforced phase graphene is dispersed at the grain boundary of the large grain, which can pin the grain boundary and reduce the merging of the subgrain boundaries, thus hindering the dislocation movement. The MgZn₂ and Mg₂Si phases in the composites aged at 120 ℃ for 24 h are the most. The addition of graphene is also beneficial to the precipitation of the second phase, which is easier to pin the grain boundary and improve the mechanical properties.

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Microstructure and properties of tinplate with different nitrogen contents after continuous annealing

Lan Haotian, Song Yifeng, Yue Chongxiang, Yang Jiawei

Heat Treatment of Metals 2025, 50 (1): 140-145. doi:10.13251/j.issn.0254-6051.2025.01.021

Abstract （25）

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Continuous annealing tests were conducted on tinplate with different nitrogen contents at different temperatures (595-710 ℃) using a continuous annealing testing machine. The microstructure, grain size, hardness, and tensile properties of the annealed tinplate were analyzed. The results show that the increase in nitrogen content raises the recrystallization temperature of the tinplate, while also refines grain size and inhabits grain growth. The hardness and strength of tinplate with higher nitrogen content are both higher than those with lower nitrogen content. The main nitrogen precipitates are dispersed rectangular TiN and AlN, which increase with the increase of nitrogen content. When the annealing temperature is raised to above 690 ℃, the lamellar pearlite in tinplate with different nitrogen contents is distributed along grain boundaries, replacing the granular pearlite distributed along the rolling direction. Based on the experimental results, controlling the continuous annealing temperature for the production of high-hardness tinplate in the industrial production within the range of 645-660 ℃ can reduce the hardness fluctuation and improve the canning efficiency.

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Effect of continuous annealing temperature on microstructure and properties of cold-rolled ultra-low carbon steel containing titanium

Ma Guangzong, Gu Tian, Wang Shuhua, Jiang Jiawei, Sun Lu, Wang Nai

Heat Treatment of Metals 2025, 50 (1): 146-149. doi:10.13251/j.issn.0254-6051.2025.01.022

Abstract （30）

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Effect of continuous annealing temperature on tensile properties, hydrogen permeability, microstructure and precipitates of Ti-containing ultra-low carbon steel was studied. The results show that with the increase of annealing temperature, the strength of the tested steel decreases gradually, the formability and hydrogen permeability increase gradually, the average grain size increases gradually, and the proportion of small size precipitates within 50 nm increases obviously. When the annealing temperature is 830 ℃, the tensile strength is 290 MPa, the yield strength is 130 MPa, the elongation is 46.5%, the n value is 0.25, the r value is 3.0, the hydrogen permeation time is 12.0 min, and the average grain diameter is 14.3 μm, showing the best of formability and hydrogen permeation performance.

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Effect of solution and aging treatment on microstructure of N03360 Ni-Be alloy

Liu Song, Liu Tao

Heat Treatment of Metals 2025, 50 (1): 150-154. doi:10.13251/j.issn.0254-6051.2025.01.023

Abstract （23）

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Effects of solution treatment temperature (1030-1190 ℃), aging temperature (460-530 ℃), and holding time (0.5-2 h) on the microstructure of N03360 Ni-Be alloy with Ti addition were studied by optical microscope and microhardness tester. The results show that the grain size of the N03360 alloy tends to increase when the solution treatment temperature exceeds 1100 ℃. When the temperature exceeds 1170 ℃, it will cause overburning, local grain boundary melting and NiBe compounds agglomeration. The rich-Be phase generated during the discontinuous precipitation process of the N03360 alloy at the grain boundaries will reduce the hardness. The higher the solution treatment temperature is, the more violent the discontinuous dissolving process will be. If the aging temperature is too high or the holding time is too long, the discontinuous dissolving process at the grain boundaries of the N03360 alloy will be out of control.

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Comparison of microstructure and properties of surfacing layer on pinch roller produced by different materials after annealing treatment

Teng Hongyin, Wang Yinjun, Wu Suotuan

Heat Treatment of Metals 2025, 50 (1): 155-161. doi:10.13251/j.issn.0254-6051.2025.01.024

Abstract （22）

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In order to improve the properties of the pinch roller and extend its service life, the current Delstain-442 welding wire and the proposed Multipass-249 and Multipass-224HC welding wires were studied. The microstructure and properties changes of the surfacing layers prepared by the three types of welding wires after annealing at 500 ℃ and 540 ℃ were compared. The results indicate that after annealing, the retained austenite in the three types of surfacing layers transformed into martensite, and the transformation of the Delstain-442 layer is more complete. The Multipass-249 layer annealed at 540 ℃ has better toughness, more stable microstructure, and better high-temperature wear resistance. The Delstain-442 layer annealed at 540 ℃ can also achieve better high-temperature hardness and high-temperature wear resistance. The Multipass-224HC layer has higher brittleness, while obtains good wear resistance after annealing at both the temperatures, where the wear rate is reduced by one order of magnitude compared to that of the Delstain-442. The comprehensive properties of the Multipass-249 layer annealed at 540 ℃ are good, but due to doubts about its impact toughness, further verification is needed to determine whether it can replace the Delstain-442.

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Effect of annealing temperature on corrosion resistance of aluminum/titanium/steel explosive clad plate

Sun Hao, Li Nannan, Zhu Lei

Heat Treatment of Metals 2025, 50 (1): 162-168. doi:10.13251/j.issn.0254-6051.2025.01.025

Abstract （34）

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Effect of annealing temperature on the corrosion resistance of 1060Al/TA2/CCSB steel explosive clad plate in artificial seawater was studied by natural immersion method, corrosion electrochemical method and micro-electrochemical test. The results show that pitting corrosion mainly occurs in the explosive clad plate in the artificial seawater solution. With the increase of annealing temperature, the corrosion resistance of the explosive clad plate changes. When annealing at 350 ℃, the radius of the AC impedance spectrum is the largest, the passivation zone appears in the polarization curve, the current density is the lowest, the potential difference between the two bonding interfaces of 1060Al/TA2 and TA2/CCSB steel is the smallest, and the explosive clad plate has the best corrosion resistance. The micro-electrochemical test results show that the TA2/CCSB steel interface has better corrosion resistance. Therefore, the corrosion resistance of the composite plate is improved after annealing treatment.

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Inheritance and refinement of coarse grains in hot forging rings of a Cr-Ni-Mo-Ti maraging stainless steel

Ding Yali, Gao Qi, Wang Ao

Heat Treatment of Metals 2025, 50 (1): 169-172. doi:10.13251/j.issn.0254-6051.2025.01.026

Abstract （27）

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In order to solve the problem of coarse grains remained in hot forging rings of a Cr-Ni-Mo-Ti maraging stainless steel, the temperature range of inheriting of forged coarse grains was investigated, and the recrystallization temperature for grain size refinement was determined. Moreover, the effect of repeated solution treatment on the grain size refinement and mechanical properties was determined. The results show that the forged coarse grains are inherited in a wide temperature range above Af of the steel. After solution treatment near 950 ℃, the austenite grains with completely closed grain boundaries and obvious refinement are formed, indicating that the recrystallization temperature T_re is approximately equal to 950 ℃, moreover, further increasing the solution temperature leads to grain growth. Repeated heating and cooling slightly below 950 ℃ lead to large grain boundary migration and forming the fine grain with open boundries. The repeated heating and cooling at 950 ℃ can still fine the grains, while the effect is weakened with the further increase of temprature, untill the effect vanish at 1050 ℃. The grain refinement by repeated heating and cooling at 875 ℃ significantly improves the impact properties, but the tensile strength and yield strength decrease, showing that the strength decreases with the grain refinement. The strength and toughness when heating and cooling once at 925, 975 ℃ (near T_re) are close to those of repeated heating and cooling for 3 cycles at 875 ℃, while the grains are slightly refined with the increase of repeated heating and cooling times, and there is no significant change in mechanical properties.

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Isothermal quenching phase transformation characteristics and mechanical properties of 300M steel

Zhao Xiaoyu, Zhang Zheng, Yang Huijun, Shi Xiaohui, Zhang Min, Qiao Junwei

Heat Treatment of Metals 2025, 50 (1): 173-179. doi:10.13251/j.issn.0254-6051.2025.01.027

Abstract （31）

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Effect of isothermal quenching process at 240-320 ℃ near Ms on the phase transformation characteristics and mechanical properties of 300M steel was studied by means of thermal dilatometer, color metallography, scanning electron microscopy and transmission electron microscopy. The results show that the isothermal quenching below Ms result in athermal martensite produces first and the incubation period of bainite transformation shortened of the 300M steel. Compared with the isothermal quenching process at 320 ℃ above Ms, the isothermal quenching process at 260 ℃ below Ms makes the retained austenite transform from blocky M/A islands to film between bainite laths, the average width of bainite lath decreases, the tensile strength increases from 1550 MPa to 1930 MPa and the total elongation increases from 7.7% to 9.2%, showing that the strength and plasticity increase simultaneously.

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Effect of tempering on microstructure and properties of air cooled bainite steel containing rare earth for oil casing

Han Qiang, Gao Zhimin, Jia Xin, Li Tao, Sun Zhaoqi, Dai Congwei

Heat Treatment of Metals 2025, 50 (1): 180-186. doi:10.13251/j.issn.0254-6051.2025.01.028

Abstract （29）

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Effects of addition of rare earth Ce and tempering process on microstructure, precipitation behavior of the second phase and hardness of air-cooled bainite steel for oil casing were compared and studied. The phase transition points of the rare earth and non-rare earth bainite steels were determined by thermal dilatometer, the microstructure and the second phase after tempering were observed and analyzed by using metallographic microscope and TEM, the precipitation behavior of the second phase was simulated by thermodynamic calculation software, and the hardness of the tested steels was tested by using Rockwell hardness tester. The results show that after tempering at 200, 450 and 650 ℃, respectively, for different time, the microstructure of the non-rare earth bainite steel is tempered martensite, tempered troostite and tempered sorbite, respectively, however, the microstructure of the rare earth bainite steel is tempered martensite, tempered troostite and tempered troostite+tempered sorbite, respectively. When tempered at 650 ℃ for 60 min, the second phases in the bainite steels are (Fe, Cr)₃C and Cr₂₃C₆ carbides. With the increase of tempering temperature and time, the hardness of the rare earth and non-rare earth bainite steel decreases overall, while the secondary hardening phenomenon is found when tempered at 450 ℃ for 120 min, and the hardness of the rare earth bainite steel is higher than that of the non-rare earth bainite steel. In conclusion, the addition of rare earth Ce can increase the temperature of the phase transition point, delay the pearlite transformation and improve the hardness of bainite steel.

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Microstructure and mechanical properties of 9Cr heat-resistant steel strengthened by TiC nanoparticles

Zhu Xiaolong, Wang Zhenghui, Wang Wenyan, Xie Jingpei, Diao Xiaogang, Zhang Feiyang

Heat Treatment of Metals 2025, 50 (1): 187-194. doi:10.13251/j.issn.0254-6051.2025.01.029

Abstract （34）

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In order to improve the high temperature strength of heat-resistant steel for steam turbine, 9Cr heat-resistant steels with different contents of TiC nanoparticles (mass fraction of 0%, 0.01%, 0.05% and 0.1%) were prepared. The microstructure of the tested steel with 0.01%TiC nanoparticles was analyzed by using high temperature laser scanning confocal microscopy (LSCM), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanical properties were studied by tensile and impact tests. The results show that the addition of TiC nanoparticles can significantly enhance the high-temperature strength at 600 ℃ of the 9Cr heat-resistant steel, and when the addition amount is 0.01%, the maximum tensile strength is 356 MPa, and the strain at fracture is 38%. The martensite structure is obtained for the tested steel with 0.01% TiC nanoparticles under air-cooling conditions, the second-phase carbide category is M₆C, and the distribution of TiC nanoparticles in the grains plays a role in dispersive strengthening. The tested steel with an addition of 0.01%TiC nanoparticles has excellent comprehensive mechanical properties after annealing at 1040 ℃+normalizing at 990 ℃+tempering at 740 ℃, with the hardness, tensile strength, yield strength, elongation and reduction of area of 177 HBS, 734 MPa, 538 MPa, 15.45% and 31.15%, respectively, and a large number of dimples are observed in the tensile fracture, indicating ductile fracture. The impact absorbed energy at room temperature is 116 J, and the ductile-brittle transition temperature FATT₅₀ is -15 ℃.

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Effect of nitrogen on microstructure and mechanical properties of cold-rolled 022Cr18Ni8N metastable austenitic stainless steel

Liu Jinrun, Lang Yuping, Chen Haitao, Feng Hanqiu, Gao Zhijun, Zhang Zhengfu

Heat Treatment of Metals 2025, 50 (1): 195-200. doi:10.13251/j.issn.0254-6051.2025.01.030

Abstract （22）

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Microstructure chang of metastable austenitic stainless steel 022Cr18Ni8N with varying nitrogen contents (0%, 0.02%, 0.05% and 0.14%) before and after cold rolling was investigated, and the effect of nitrogen on the microstructure and properties was characterized by using OM, EBSD, XRD, and room temperature tensile tests.The results indicate that nitrogen can improve the stability of austenite of the tested steel and reduce the formation of deformation induced martensite during cold deformation. The strain-induced martensite nucleates at the intersections of deformation bands, within solitary deformation bands, and at the intersections of deformation bands and grain boundaries. An appropriate nitrogen content endows metastable austenitic stainless steel with enhanced comprehensive mechanical properties through the regulation of two strengthening mechanisms, namely phase transformation strengthening and solution strengthening.

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Effect of grain size on 650 ℃ tensile properties of GH4720Li nickel-based alloy

Guo Jing, Wen Xiaocan, Wang Qiang, He Xin, Lü Shaomin, Xie Xingfei, Qu Jinglong, Du Jinhui

Heat Treatment of Metals 2025, 50 (1): 201-205. doi:10.13251/j.issn.0254-6051.2025.01.031

Abstract （34）

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GH4720Li alloy bars were solid solution treated at different temperatures of 1100, 1090, 1080, and 1070 ℃ to obtain four different microstructure with average grain sizes of 24, 18, 15 and 3-5 μm, respectively. The effect of grain size on the high-temperature tensile properties of the alloy at 650 ℃ was investigated. The results show that with the reduction of grain size, the 650 ℃ strength of the GH4720Li alloy increases, accompanied by a decrease in plasticity. When the grain size is further reduced to 3-5 μm, the plasticity begins to increase, and at this time, the alloy exhibits the optimal comprehensive tensile properties at 650 ℃. This is attributed to the pinning effect of primary γ′ strengthening relative to grain boundary, resulting in a fine grain structure that not only provides a large number of grain boundaries and improves strength, but also disperses plastic deformation, reduces stress concentration, and improves plasticity. Simultaneously, an appropriate amount of secondary and tertiary γ′ strengthen phase can further ensure the strength of the alloy.

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Effect of aging temperature on intergranular corrosion susceptibility of 7055 aluminum alloy

Zhu Cong, Wang Zhixiu, Wang Ye, Li Hai

Heat Treatment of Metals 2025, 50 (1): 206-212. doi:10.13251/j.issn.0254-6051.2025.01.032

Abstract （26）

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Effect of aging temperature (150, 180, 210 ℃) on intergranular corrosion susceptibility of 7055 aluminum alloy was studied by means of optical microscope (OM), transmission electron microscope(TEM), hardness test and intergranular corrosion test. The results show that under the same hardness condition, intergranular corrosion occurs in the under-aged alloy, while pitting corrosion occurs in the peak-aged and over-aged alloys. With the increase of aging temperature and time, the intergranular corrosion susceptibility of the alloy decreases and the corrosion morphology changes from intergranular corrosion to pitting corrosion. With the aging temperature increasing from 150 ℃ to 210 ℃, the grain boundary precipitates (GBPs) change from continuous distribution to discontinuous distribution, the Cu content in GBPs increases from 3.82% to 5.02%, and the width of precipitate free zones (PFZs) increases from 37 nm to 55 nm. The change of intergranular corrosion susceptibility of the alloy is due to the combined effect of coarsening and discontinuous distribution of GBPs, the broadening of PFZs, and the segregation of Cu element in GBPs.

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Effect of cooling temperature on microstructure and mechanical properties of a hot-rolled dual-phase steel

Wang Cheng, Liu Yajun, Chen Zhihui, Tong Shankang, Gan Xiaolong

Heat Treatment of Metals 2025, 50 (1): 213-218. doi:10.13251/j.issn.0254-6051.2025.01.033

Abstract （30）

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Based on the process of thin slab continuous casting and rolling, the effect of various cooling temperatures after hot rolling on the microstructure and properties of a hot-rolled dual-phase steel was studied by using optical microscope, universal tensile machine, microhardness tester, and X-ray diffractometer. The results show that the yield strength and tensile strength first decrease and then increase, while the total elongation gradually decreases with the cooling temperature increases from 640 ℃ to 720 ℃. In addition, the hardness decreases first and then increases with the increase of cooling temperature, which is consistent with the trend of strength changes, indicating that higher strength and hardness can be obtained after cooling at 720 ℃. The grain size of ferrite first increases and then decreases with the increase of increasing cooling temperature, and the martensite content gradually increases. It is shown from the calculation according to the strengthening mechanism of the dual-phase steel that the difference in strength of the specimens under different cooling temperatures is mainly due to the differences in grain refinement strengthening, transformation strengthening and dislocation strengthening, among which the grain refinement strengthening and dislocation strengthening are the main mechanisms, and the theoretical strength calculation results are in agreement with the experimental results.

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Effect of peak aging on compression properties of 7075 aluminum alloy produced by spray forming and extrusion

Li Yangyang, Yu Xinran, Meng Tao, Zhong Jiawen, Zhang Yaocheng

Heat Treatment of Metals 2025, 50 (1): 219-223. doi:10.13251/j.issn.0254-6051.2025.01.034

Abstract （31）

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Solution+peak aging treatment (470 ℃× 2 h, water cooling, 120 ℃× 24 h, air cooling) was carried out on spray formed and extruded 7075 aluminum alloy, and microstructure and compressive properties of the alloy were characterized. The results show that the microstructure of the alloy consists of aluminum matrix and coarse rod-shape η(MgZn₂) phase distributed along the extrusion direction. After solution and peak aging treatment, the recrystallization occurs and the recrystallized grain size is 20-30 μm, and a large number of nanoscale strengthening phases η′(MgZn₂) and GP zones are precipitated. The compressive stress of the alloy slowly increases with the increase of strain. The compressive strength and compressive stress of the spray formed and extruded and peak aged alloy (at a compressive strain of 0.5) are 475.8-540.6 MPa and 700.1-807.7 MPa, respectively. The nanoscale strengthening phase in peak aged alloy inhibits dislocation movement, significantly improving the compression properties of the alloy. The compressive stress of the alloys in two states at room temperature is insensitive to the quasi-static strain rate. The fracture mechanism of the spray formed and extruded alloy is a mixed mode of transgranular fracture and intergranular fracture, and the peak aged alloy shows an intergranular fracture. The key to ensuring the ultra-high strength and overcoming the poor plasticity of the 7075 aluminum alloy is the uniform microstructure and the supersaturated solid solution obtained by spray forming and extrusion, and the fine recrystallized grains obtained by the solution and peak aging treatment.

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Effect of annealing time on microstructure and texture of cold-rolled 1.0%Si non-oriented silicon steel

Guo Han, Xuan Dongpo, Xu Ning, Dong Linshuo, Zhang Jian, Li Zhijian, Liu Xuming

Heat Treatment of Metals 2025, 50 (1): 224-229. doi:10.13251/j.issn.0254-6051.2025.01.035

Abstract （25）

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Effect of different annealing time at 850 ℃ on the microstructure and texture of 1.0%Si non-oriented silicon steel cold-rolled sheets was investigated by means of characterization techniques such as EBSD and XRD. The results indicate that the cold-rolled sheets undergo recrystallization when annealed at 850 ℃ for 90 s. The texture type transforms from strong α and rotated cube texture {001}<110> to γ texture {111}<112> and α^* texture. When annealed from 90 s to 180 s, the grain size gradually increases, with the average grain size growing from 14.2 μm to 21.3 μm. The α^* texture and rotated cube texture {001}<120> strengthen gradually, the magnetic induction B₅₀₀₀ increases from 1.55 T to 1.63 T, and the iron loss P_1.5/50 decreases from 4.213 W/kg to 3.832 W/kg.

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Characterization of microstructure of P92 heat-resistant steel elbow during high-temperature creep rupture process

Peng Xingna, Cong Xiangzhou, Peng Xiankuan, Tu Dejun, Qiao Yaxia

Heat Treatment of Metals 2025, 50 (1): 230-235. doi:10.13251/j.issn.0254-6051.2025.01.036

Abstract （27）

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Microstructure transformation of the clamping section (aging), deformation section (creep), and necking position (rupture) of P92 steel elbows during creep rupture at 630 ℃ and different stresses (175, 140, 130, and 100 MPa) was studied by using scanning electron microscopy, transmission electron microscopy, EBSD, etc. The results indicate that strain-induced precipitation coarsening occurs in the P92 steel elbows under creep conditions. After long-term aging, the morphology of the P92 steel changes from martensite lath to edge dislocation. The cracks near the rupture of the P92 steel initially expand into elliptical holes. After the Laves phase precipitates, the grain boundary strength decreases compared to the early stage, and the cracks transform into wedge and flower shapes.

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Optimization of induction heating process for ball screw based on finite element analysis

Li Mingzhe, Chen Baofeng, Zhang Wenliang, Sun Lizhuang, Zhang Lun, Liu Junjie

Heat Treatment of Metals 2025, 50 (1): 236-242. doi:10.13251/j.issn.0254-6051.2025.01.037

Abstract （29）

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In order to optimize the induction heating process of ball screw and improve the uniformity of its surface temperature distribution, thereby improving its manufacturing precision and performance, a finite element model was constructed by means of electromagnetic simulation software to analyze the influence of different process parameters on the surface temperature distribution of the ball screw during both static and dynamic induction heating. The results show that an excessively small internal diameter of the induction coil results in a narrow gap between the workpiece and the coil, which can easily lead to overheating of the workpiece surface. Conversely, an excessively large internal diameter results in a wide gap, reducing heating efficiency and resulting in a shallow heating layer. Therefore, selecting an induction coil with an appropriate internal diameter is essential for ensuring the quality of heating. The double-turn coil demonstrates superior performance in terms of heating efficiency and temperature uniformity. Employing high voltage and an appropriate current frequency can improve heating efficiency and control the depth of heating layer. For dynamic heating, a scanning speed of 6-10 mm/s is recommended to achieve a balance between heating efficiency and process stability.

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Numerical calculation of convective heat transfer coefficient and quenching simulation of 2195 Al-Li alloy hemispherical shell

Song Kejin, Du Yue, Fu Xuesong, Kang Li, Du Baoxian, Zhou Wenlong

Heat Treatment of Metals 2025, 50 (1): 243-249. doi:10.13251/j.issn.0254-6051.2025.01.038

Abstract （25）

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By combining analytical and numerical methods, the convective heat transfer coefficient of 2195 aluminum lithium alloy hemispherical shell was approximately calculated, and the variation law of convective heat transfer coefficient with temperature under air cooling and water cooling conditions was analyzed. Using ABAQUS finite element simulation software, a thermo-mechanical coupling model was constructed, and the quenching process of the 2195 aluminum lithium alloy hemispherical shells with diameters of ø200 mm and ø100 mm was simulated by finite element method, and the stress and strain laws during the quenching process were analyzed. The results show that during the water cooling process, the heat transfer coefficient of the aluminum lithium alloy hemispherical shell increases first and then decreases with the surface temperature of the workpiece from low to high, and the peak point appears at around 175 ℃. During the air cooling process, the convective heat transfer coefficient increases with the increase of workpiece temperature. The simulation results of the quenching process indicate that stress concentration occurs at the mouth of the hemispherical shell, and plastic strain mainly occurs at the surface of the hemispherical shell mouth. The stress and strain distribution patterns of hemispherical shells with different sizes after cooling at different inlet water temperatures are similar.

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Modeling and numerical simulation of heating process for roller hearth furnace with radiant tube heating

Kong Haoran, Pang Yuhua, Gao Qiang, Li He, Sun Qi

Heat Treatment of Metals 2025, 50 (1): 250-254. doi:10.13251/j.issn.0254-6051.2025.01.039

Abstract （25）

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In order to study the heating characteristics of steel plate in the heating furnace during heating process, a high-precision computational fluid dynamics (CFD) model of the heating furnace was established by using FLUENT based on a roller hearth furnace with radiant tube heating. The heating process of the steel plate, heating temperature of 873.5 K and heating time of 135 min, was numerically simulated, and the simulation results were experimentally verified. The simulation results show that the temperature of the steel plate in heating stage rises rapidly, with a higher surface temperature, but the overall temperature of the steel plate does not show significant differences, indicating that the overall heat transfer of the steel plate is relatively uniform. The comparison between the CFD heating model results and the experimental results shows that the maximum error in the average temperature of the steel plate is only 5 K, with an error of less than 1%, indicating good consistency between the experiment and simulation.

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Prediction of properties and mechanism of Cu-Ni-Co-Si alloys based on machine learning and genetic algorithm

Zhang Yingfan, Chen Huiqin, Dang Shue, Chen Juan, Xu Quan, Fang Xiaotian, Shi Tenglong, Dai Yunyun

Heat Treatment of Metals 2025, 50 (1): 255-265. doi:10.13251/j.issn.0254-6051.2025.01.040

Abstract （37）

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Application of machine learning in materials research is extensive. However, the task of designing alloys based on many composition and process factors remains a significant difficulty. A machine learning approach to develop alloys by considering the physicochemical qualities, composition, and process of the material was proposed. The property prediction of the Cu-Ni-Co-Si alloy was then optimized by using a genetic algorithm. The recursive elimination method was employed to investigate the potential correlation between the characteristics and alloy properties. The results show that the primary factors influencing the hardness and conductivity characteristics of the alloys are the aging treatment and cold rolling deformation. Furthermore, the physicochemical properties primarily influence the conductivity of the alloy by impacting the density of free electrons and the free path of free electron migration. It affects the hardness of the alloy by exerting influence on solution strengthening and dislocation strengthening.

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Machine learning to predict effect of annealing temperature and time on mechanical properties of SUS321 stainless steel

Wang Huanhuan, Lu Sujun, Li Yuan, Xu Ning, Zhu Tingxian, Wang Xu, Wei Ning, Wu Dali, Peng Weizhong

Heat Treatment of Metals 2025, 50 (1): 266-271. doi:10.13251/j.issn.0254-6051.2025.01.041

Abstract （24）

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In order to reveal the complex relationship between mechanical properties and heat treatment process of SUS321 stainless steel, a prediction model between annealing temperature, annealing time and mechanical properties of the SUS321 stainless steel was established by machine learning method based on random forest model. The results show that the prediction validity parameter R² of the model for the tensile strength, yield strength and elongation of the SUS321 stainless steel exceeds 0.8, showing a good prediction effect. The analysis based on partial dependence plots and individual conditional expectation plots shows that with the increase of annealing temperature and annealing time, the tensile strength and yield strength of the SUS321 stainless steel decrease, while the elongation increases, and the annealing temperature is the main feature parameter.

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In-situ three-dimensional morphological characterization and statistical quantification of inclusions in steels

Yan Chunlian, Qi Qige, Ju Xinhua, Qin Hancheng, Yang Rui, Cui Guibin

Heat Treatment of Metals 2025, 50 (1): 272-281. doi:10.13251/j.issn.0254-6051.2025.01.042

Abstract （27）

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Three-dimensional morphological characterization and automatic statistical quantification of typical inclusions such as large-size Al₂O_3,MnS, conventional oxysulfides and nitrides were conducted in the ultra-low carbon steel, free cutting steel, pipeline steel and spring steel by using electrolytic etching and automated inclusion analysis technique. The in-situ electrolytic etching mechanism and the effects of electrolytic experimental parameters and analysis parameters of scanning electron microscope on the three-dimensional characterization of inclusions were discussed. The results show that different inclusions in the tested steels appear to be protruded on the flat matrix by controlling the electrolytic parameters of the constant potential electrolytic etching of the steel specimens, and then the real three-dimensional morphologies of the inclusions can be observed by the scanning electron microscope, and the inclusions in a certain area can be quantified statistically. When the electrolytic voltage increases or the electrolytic time prolongs properly, the etching of the electrolyte on the matrix increases accordingly, which is beneficial to the more exposure of the inclusions. However, the pearlite, bainite and martensite microstructures of the steel matrix are easy to cause serious interference to the statistical quantitative results of inclusions, therefore some measures such as the filtration of matrix composition or inhibiting the appearance of matrix structure can be taken to prevent its unfavorable effects. Scanning electron microscope parameters such as magnification, image mode, image contrast and inclusion gray threshold also have an important influence on the three-dimensional statistical quantification of inclusions, therefore these parameters should be set appropriately to ensure that inclusions are accurately identified and quantified. The in-situ electrolysis method can quickly obtain the in-situ three-dimensional morphology of non-metallic inclusions in the steels, and realize the automatic statistical quantification of inclusions in the steels with different matrix microstructures. Compared with the two-dimensional analysis, the three-dimensional morphology of inclusions obtained by the in-situ electrolysis method is more complete, and the statistical quantitative data of the inclusions obtained from a certain depth area of the steel specimens are more representative.

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Causes analysis of induction hardening cracks in grey cast iron for high-end CNC machine tool guide rails

Yan Haoming, Yu Penghan, Yu Xingfu

Heat Treatment of Metals 2025, 50 (1): 282-286. doi:10.13251/j.issn.0254-6051.2025.01.043

Abstract （28）

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Effect of induction hardening on the microstructure, hardness, and hardened layer thickness was analyzed of a high-end CNC machine tool guide rail formed by HT300. The causes of cracks during the quenching process were also analyzed. The results show that after intermediate frequency induction hardening, the surface hardness of the machine tool integrated guide rail of cast iron HT300 can reach over 700 HV (60 HRC), and the depth of the harded layer can reach 5.5 mm. After induction hardening heat treatment, the surface layer of the cast iron guide rail mainly forms cryptocrystalline martensite, the transition layer mainly consists of martensite+pearlite structure, and the core is mainly composed of pearlite structure. Crack analysis shows that the graphite in cast iron is mainly E-type graphite, and the phosphorus eutectic structure present in the cast iron dissolves and precipitates during quenching, reducing the surface strength of the cast iron. After deep layer induction hardening, the tensile stress formed on the surface layer exceeds the strength of the cast iron, which is the main reason for the cracking of the cast iron during quenching. The cracking source is located on the surface, and the cracking location is mostly in the phosphorus eutectic region.

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Analysis of bare defects in alloyed hot dip galvanized DP980GA steel strip

Liu Xueliang, Zeng Songsheng, Long Xukai, Xiao Bing, Zeng Weimin, Cheng Yuqiang

Heat Treatment of Metals 2025, 50 (1): 287-291. doi:10.13251/j.issn.0254-6051.2025.01.044

Abstract （19）

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Causes of surface bare defects of alloyed galvanized DP980GA strip were analyzed by means of macro and micro morphology observation and composition analysis. The results show that a large number of manganese oxide and iron oxide particles are found inside the plating pit, and a small amount of alumina and chromium oxide are also found, which is due to the enrichment and selective oxidation of manganese on the surface of the steel strip in the continuous annealing furnace, and the aluminothermic replacement reaction in the zinc pot is incomplete, thus reducing the wettability of the strip surface and causing the bare defects. It is suggested that through moderately reducing the dew point temperature of the heating section in the continuous annealing furnace to reduce the manganese oxide film formed by selective oxidation on the surface and its thickness, and moderately increasing the Al content in the zinc pot to promote the aluminothermic replacement reaction, the manganese oxide on the surface of the strip can be fully replaced by alumina and sunk into the zinc pot, thereby the wettability of the strip surface can be improved and the problem of surface bare defects can be solved.

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Fracture failure analysis of 20CrMoH alloy steel reducer bevel gear shaft

Li Bing, Xu Feiyue, Zhang Peng, Xing junfeng, Tang Zhengqun

Heat Treatment of Metals 2025, 50 (1): 292-298. doi:10.13251/j.issn.0254-6051.2025.01.045

Abstract （31）

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In response to the problem of fracture of 20CrMoH alloy steel reducer bevel gear shaft during installation and tightening, the macroscopic morphology, microstructure, and hardness of the fracture specimen were tested and analyzed using optical microscopy, microhardness tester, scanning electron microscopy, and other detection methods to identify the cause of the fracture. The results show that the cracks in the 20CrMoH steel bevel gear shaft originate from poor machining of the thread start stop groove, with multiple points of fracture and severe wear in the source area. Subsequently, under the action of bending shear stress, the cracks propagate along the carburized transition layer and fracture, with the fracture morphology showing intergranular features. The chemical composition and hardness of the parts basically meet the requirements, but there is a significant variation in hardness at the core of the parts. Overall, the parts exhibit characteristics of high stress overload fracture, which is caused by stress concentration due to poor machining tool marks and material conditions, leading to the fracture. It is recommended to investigate the stress state during tightening and improve the heat treatment process conditions to reduce the depth of the induction annealing layer and narrow down the heat affected zone.

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Microstructure and properties of ion nitriding/PVD composite modified layer on 316L stainless steel

Cao Chi, Zhang Xiang, Chen Zhilin, Chen Dongsheng, Zhang Zhuo

Heat Treatment of Metals 2025, 50 (1): 299-307. doi:10.13251/j.issn.0254-6051.2025.01.046

Abstract （36）

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To improve the surface hardness, wear resistance, and corrosion resistance of stainless steel, the effects of single ion nitriding and ion nitriding/physical vapor deposition (PVD) composite treatments on the microstructure, hardness and tribological and corrosion properties of 316L austenitic stainless steel were studied. The results show that the specimen treated by single ion nitriding forms a high-nitrogen hardened layer with a thickness of about 20 μm and hardness of about 802 HV0.05. The specimen treated by nitriding/PVD composite treatment forms a modified layer with a thickness of about 25 μm and nanohardness of about 29 GPa. Both processes form the γ_N phase, and the amorphous film formed on the surface of the nitriding/PVD composite treated specimen does not affect the phase of the intermediate layer. Compared to that of the substrate steel, the friction coefficients of the single nitrided specimen decrease to 0.520 and 0.311 under dry friction and corrosive friction conditions, respectively, while that of the nitriding/PVD composite treated specimen decrease to 0.074 and 0.119, respectively. The self-corrosion current density of the single nitrided and the nitriding/PVD composite treated specimens decrease from 4.602×10^-8 A/cm² to 4.084×10^-8 A/cm² and 3.318×10^-8 A/cm², respectively, and the self-corrosion potentials increase from -0.213 V to -0.195 V and -0.182 V, respectively. Comprehensively, the composite treatment can significantly improve the surface hardness, wear resistance, and corrosion resistance of the 316L austenitic stainless steel.

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Development of induction heat treatment technology and equipment for key components of machine tool

Li Xianjun, Jiang Chao, Zhang Minghao, Zhang Wenliang, Sun Lizhuang

Heat Treatment of Metals 2025, 50 (1): 308-316. doi:10.13251/j.issn.0254-6051.2025.01.047

Abstract （27）

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Induction heat treatment technology and its application in key components of machine tool were summarized from the two aspects of induction heat treatment technology and equipment, the specific induction heat treatment process and equipment design for spindle, ball screw and guideway of the machine tool were introduced, and the prospects for future promotion were prospected.

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Effect of centrifugal barrel finishing/QPQ combined treatment on wear resistance of titanium alloy

YanYuan, Li Xiuhong, Li Qihang, Wang Delong, Li Wenhui

Heat Treatment of Metals 2025, 50 (1): 317-324. doi:10.13251/j.issn.0254-6051.2025.01.048

Abstract （16）

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Aiming at the high surface requirement when applying QPQ treatment to improve titanium alloy surface properties, centrifugal barrel finishing before QPQ treatment was carried out. The effect of centrifugal barrel finishing/QPQ combined treatment on the surface morphology, phase composition, microhardness and wear resistance of TC4 titanium alloy were studied by means of XRD, SEM, ultra-depth of field optical microscope, white light interferometer, roughness meter, micro-Vickers hardness tester and friction and wear tester. The results show that more uniform titanium nitrides and oxides are formed on the surface of TC4 titanium alloy after centrifugal barrel finishing composite QPQ treatment, and the surface quality is improved as the surface roughness Ra decreases by 35.7% than that of only grinding, the microhardness increases by 42.74%, the average friction coefficient decreases by 6.56%, the wear rate decreases by 38.89%, and the wear scar depth decreases by 49.81%, indicating that the wear resistance increased significantly.

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Friction properties of H13 steel nitrocarburizing-modified by hollow cathode plasma source

Liao Yongfa, Shang Yong, Li Yang, Liu Zhongli, Jiang Mingquan, Zhou Zelong, Gao Yue

Heat Treatment of Metals 2025, 50 (1): 325-331. doi:10.13251/j.issn.0254-6051.2025.01.049

Abstract （24）

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To improve the hardness and wear resistance of H13 steel, surface treatment of H13 steel was carried out by hollow cathode ion discharge nitrocarburizing (520, 530 and 540 ℃ for 5 h), and the microstructure, hardness and friction and wear properties of the H13 after nitrocarburizing were analyzed. The results show that an iron-nitride compound diffusion layer is formed on the surface of the H13 steel after nitrocarburizing, which results in significantly improvement of the hardness and wear resistance. The surface hardness of the specimen after nitrocarburizing at 530 ℃ is the highest, which is 999.3 HV0.1, 120% higher than that of the specimen after quenching and tempering, and the depth of the hardening layer is about 175 μm based on the measurement of hardness gradient. The friction and wear test under oil lubrication condition shows that the wear volume of the specimen after nitrocarburizing at 540 ℃ is 83% lower than that of the specimen after quenching and tempering.

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Influence of diffusion regimes on duplex platinum-aluminum coating on nickel based superalloy

Si Yan, Wu Yeqiong, Chao Guotao, Li Jie, Huang Xuanxuan, Guo Shuangquan, Li Shuguang

Heat Treatment of Metals 2025, 50 (1): 332-336. doi:10.13251/j.issn.0254-6051.2025.01.050

Abstract （23）

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The duplex platinum-aluminum coatings were prepared by electroplating platinum, vacuum diffusion and embedded aluminization. Effects of different diffusion and annealing treatments on the thickness, element content and hardness of the duplex platinum-aluminum coatings were studied. The results show that the Pt content of the outer layer decreases with the increase of diffusion temperature, the Al content slowly increases with the increase of diffusion temperature, the hardness of the outer layer of the coatings slowly decreases with the increase of diffusion temperature, and the hardness of the middle layer does not change much. At the same time, adding annealing treatment after coating preparation can reduce the hardness of the outer layer of the duplex platinum-aluminum coatings and decrease the brittleness of the coatings.

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Necessity and designation of integrated application elective course for metal-related majors——“Materials Engineering and Performance” elective course

Xiong Zhiping, Wang Yingchun, Cheng Xingwang

Heat Treatment of Metals 2025, 50 (1): 337-340. doi:10.13251/j.issn.0254-6051.2025.01.051

Abstract （25）

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The existing curriculum system for metal-related majors provides students with perfectly solid training in both theoretical knowledge and practical skills. However, it is difficult for students to integrate the knowledge points scattering across different courses into a complete knowledge system. This indicates that there is still a lack of an integrated application course that enables students to flexibly apply all their professional knowledge. Therefore, the elective course "Materials Engineering and Performance" has been designed. It covers microstructure control, strengthening mechanisms, and ductility and toughness mechanisms, which helps students to integrate the theoretical knowledge of materials science. Importantly, it can cultivate their ability to design new metal materials. Thus, this course will enable students to effectively address practical issues in the fields of science and engineering.

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Creep property and microstructure evolution at 700 ℃ of a novel Fe-Ni based superalloy

Jiao Chunhui, Pan Yanjun, Li Shengzhi, Bai Du, Li Bei, Deng Ge, Jia Xiaoshuai

Heat Treatment of Metals 2025, 50 (2): 1-7. doi:10.13251/j.issn.0254-6051.2025.02.001

Abstract （90）

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A novel Fe-Ni-based superalloy, intended for ultra-supercritical thermal power generating units, was evaluated under constant load conditions at 700 ℃ with varying stress levels of 250 MPa and 200 MPa. The service limit and creep life of the alloy were predicted, and the microstructure evolution during creep was analyzed. The results indicate that the creep life of the alloy at 700 ℃/250 MPa and 700 ℃/200 MPa is 2378 h and 12 716 h, respectively. Based on the Larson-Miller equation, the alloy can withstand stresses of approximately 152 MPa after 100 000 h and 134 MPa after 260 000 h at 700 ℃, fully meeting the service requirements (stress of 35 MPa, creep life of 100 000 h). Microstructure analysis reveals that high-density dislocations are distributed in the 700 ℃/250 MPa specimen, whereas fewer dislocations are observed in the 700 ℃/200 MPa specimen. The MC carbides with larger size within the grains predominantly exhibit blocky or rod-like morphologies, with faster growth rates under higher stress conditions. The smaller M₂₃C₆ carbides at grain boundaries precipitate primarily in chain form, and their width increases with prolonged creep exposure. The γ′ phase within the grains remains spherical but undergoes coarsening during creep. Notably, some grain boundary γ′ phases exhibit abnormal growth, forming PFZs/DCZs, which adversely affect the alloy's high-temperature creep performance.

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Hot deformation behavior of Inconel617 alloy

Ding Zuojun, Ren Wenhao, Zhang Guo, Zheng Yue, He Xikou

Heat Treatment of Metals 2025, 50 (2): 8-14. doi:10.13251/j.issn.0254-6051.2025.02.002

Abstract （35）

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Hot compression simulation tests of Inconel617 alloy were carried out using Gleeble-3800 thermal simulation test machine in the range of deformation temperature of 950-1200 ℃ and strain rate of 0.001-1 s^-1. The hot deformation behavior under different deformation conditions were analyzed. The results show that the Inconel617 alloy exhibits obvious work hardening characteristics at the initial stage of deformation. As the strain increases, the flow stress increases to the peak value and then gradually decreases, showing dynamic softening dominated by dynamic recrystallization. The hot deformation constitutive equation of the Inconel617 is constructed based on the Arrhenius model modified by the hyperbolic sine function. The hot deformation activation energy Q is 418.4 kJ/mol. The hot working map of the Inconel617 alloy is constructed, and the appropriate hot working range is determined: deformation temperature of 1080-1170 ℃, strain rate of 0.012-1 s^-1.

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Creep rupture property at 550 ℃ and microstructure evolution of 316H stainless steel forging for generation IV reactor

Zhang Zhifeng, Zhao Jiqing, Wang Xiaofang, Wang Yunhai, Yang Gang

Heat Treatment of Metals 2025, 50 (2): 15-22. doi:10.13251/j.issn.0254-6051.2025.02.003

Abstract （28）

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Creep rupture strength of 316H stainless steel forging was tested by rupture test machines at 550 ℃, and the fracture morphology and microstructure of the fracture specimens were analyzed by optical electron microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results indicate that the 316H stainless steel forging has high creep rupture strength at 550 ℃, the creep rupture stress after 10 000 h determined through the isothermal extrapolation method is 314 MPa, which significantly exceeds the ASME design criteria. The fracture morphology of the 316H stainless steel forging consists of both dimple and intergranular fracture patterns. As the fracture duration increases, the proportion of intergranular fracture progressively rises, and the origin of the fractures transitions from non-metallic inclusions into second-phase particles at the grain boundaries. The 316H steel forging displays good structural stability throughout the 550 ℃ rupture test. As the applied stress reduces and fracture duration extends, the grain size progressively increases, the grain boundary area diminishes, and only a small amount of M₂₃C₆ and σ phases are precipitated at the grain boundaries

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Influence of Mn on high-temperature mechanical properties of low Ni duplex stainless steel

Yang Yuheng, He Jianguo, Song Zhigang, Feng Han, Lü Jiesheng, Wu Xiaohan, Gu Yang, Zhu Yuliang

Heat Treatment of Metals 2025, 50 (2): 23-28. doi:10.13251/j.issn.0254-6051.2025.02.004

Abstract （20）

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High-temperature tensile tests were conducted on 17Cr-2Ni-2Mo-0.2N-xMn (x=2, 3, 4) duplex stainless steel at 900-1300 ℃ and 1 s^-1, and thermal compression tests were conducted with 50%, 60%, and 70% deformation at 900-1300 ℃ and 1 s^-1, respectively, to investigate the effect of Mn content on its high-temperature mechanical properties. The results indicate that at a deformation temperature of 900 ℃, ferrite undergoes dynamic recrystallization, while austenite only undergoes partial dynamic recrystallization. At a deformation temperature of 1200 ℃, ferrite mainly undergoes dynamic recovery, while austenite undergoes dynamic recrystallization. All specimens exhibit varying degrees of dynamic recovery or dynamic recrystallization during high-temperature deformation, with secondary hardening occurring in the final stage of the thermal compression test. In the thermal compression test, when the Mn content increases from 2% to 4%, the dynamic recrystallization behavior of 17Cr duplex stainless steel first intensifies and then slows down in the temperature range of 900-1100 ℃. However, at deformation temperatures of 1200 ℃ and higher, the effect of Mn content on the dynamic recrystallization behavior is relatively small. At the temperature range of 1150-1200 ℃, the thermal tensile deformation resistance decreases initially and then increases with the rise of manganese content, with 3% manganese providing the best hot working performance.

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Microstructure and hot deformation behavior of U-50%Zr alloy for nuclear fuel

Li Yanfeng, Guo Hong, Li Mingyang, Hu Bingkun, Liu Jiancheng

Heat Treatment of Metals 2025, 50 (2): 29-35. doi:10.13251/j.issn.0254-6051.2025.02.005

Abstract （25）

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U-50%Zr alloy for nuclear fuel was prepared by high-frequency induction melting, and its microstructure and phase constituent were analyzed using metallographic microscope and X-ray diffractometer. The Gleeble-3800 thermal simulation test machine was used to conduct hot compression tests at different deformation temperatures (500, 550 and 600 ℃) and strain rates (0.01 s, 0.1 and 1 s^-1) to investigate its hot deformation behavior. The results show that, except for a deformation temperature of 600 ℃ and a strain rate of 0.01 s^-1, the U-50%Zr alloy exhibits significant work hardening characteristics under other deformation conditions. At the same strain rate, the peak stress decreases with the increase of deformation temperature, especially at 600 ℃, where the peak stress decreases significantly compared to 500 ℃ and 550 ℃. At the same deformation temperature, the peak stress increases with the increase of strain rate. After hot deformation, no phase transformation occurs in the microstructure, all of which are δ-UZr₂ phase. As the hot deformation temperature increases, the grain size of the alloy initially remains basically unchanged and then increases. At 500 ℃ and 550 ℃, the grain size is around 250 μm, and at 600 ℃, the grain size significantly increases to 493 μm. Based on peak stress, the constitutive equation of U-50%Zr alloy is established using the hyperbolic sine function Arrhenius model and temperature compensation factor Z parameter, with a hot deformation activation energy Q=694.9 kJ/mol. A hot working map is constructed using DMM dynamic material model, and the appropriate processing range is determined as follows: deformation temperature above 540 ℃, strain rate between 0.01 s^-1 and 1 s^-1.

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High-temperature fatigue property of 30Cr1Mo1V rotor steel at 540 ℃

Na Risu, Zhang Yuetao, Zhang Shuo, Meng Weiran, Wang Xiao

Heat Treatment of Metals 2025, 50 (2): 36-42. doi:10.13251/j.issn.0254-6051.2025.02.006

Abstract （22）

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High-temperature fatigue tests were conducted on 30Cr1Mo1V steel under different stresses (450$\rightleftharpoons$0, 400$\rightleftharpoons$0, 350$\rightleftharpoons$0, 350$\rightleftharpoons$233, 350$\rightleftharpoons$175 MPa) at 540 ℃. The results indicate that the fatigue life of the 30Cr1Mo1V steel decreases rapidly as the peak stress exceeds 350 MPa. Under a stress of 350 MPa, the ferrite does not change too much, which maintains the initial polygon-like shape, and the ultimate failure feature of the steel is fatigue cracking. Nevertheless, when the stress rises to 400 MPa, the ferrite deforms remarkably and shows a wrinkled river-like shape after fatigue failure, meanwhile, the pores also appears at the intersection location of the ferrite bands. In addition, subjecting the long-term high stress level like at 350$\rightleftharpoons$233 MPa and 350$\rightleftharpoons$175 MPa are harmful to the fatigue life of the 30Cr1Mo1V steel, as continuous stress can significantly increase the number of fatigue pores inside the material. In summary, the 30Cr1Mo1V steel is relatively safe under service conditions of 540 ℃/350 MPa, with a fatigue life of 12 887 cycles, and a one-time attrition rate of approximately 0.007 76% which is less than the requirement of 0.01%.

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Influence of martensitic multi-level structure and TiN inclusions on fracture toughness of 20CrMnTi steel

Long Shaolei, Zhu Dandan, Luo Xianglan, Yi Yanliang, Yang Ming, Lu Yemao, Liang Yilong

Heat Treatment of Metals 2025, 50 (2): 43-51. doi:10.13251/j.issn.0254-6051.2025.02.007

Abstract （17）

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Fracture toughness (K_IC) of 20CrMnTi steel was tested by using three-point bending specimens, and it was found that the value of K_IC decreases with grain coarsening, which contradicts the relationship between the K_IC and the grain size of other low carbon lath martensitic steels. Based on this, the fracture behavior of the 20CrMnTi steel was analyzed by means of OM, EBSD, SEM and thermodynamic model, fracture mechanics model. The results show that the relationship between the multi-level microstructure of the 20CrMnTi steel and K_IC established based on the Hall-Petch equation reveals that the martensitic lath block is the effective grain for fracture toughness. Still, the fracture morphology analysis reveals that the effective grains in the coarse or fine grain states of the 20CrMnTi steel are different. Further analysis reveals the presence of a certain number of irregular TiN inclusions on the fracture, and thermodynamic calculations show that the TiN inclusions are formed in the liquid-phase region with coarse size, which can easily lead to crack initiation. The crack propagation is analyzed with the help of SEM and fracture mechanics calculations, revealing that the crack propagation in the fine grain state of the 20CrMnTi steel is zigzagging and cross-cutting the lath martensite packet, which leads to a better fracture toughness, whereas the crack path in the coarse grain state is straight and shows a poor toughness. Therefore, the formation of TiN inclusions is the key factor leading to the abrupt change in fracture toughness of the 20CrMnTi steel, and the results of this study are of great significance in guiding the preparation of the high-performance 20CrMnTi steel.

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Microstructure refinement and properties of as-cast Ti-6Al-4V titanium alloy

Sun Hao, Meng Xun

Heat Treatment of Metals 2025, 50 (2): 52-60. doi:10.13251/j.issn.0254-6051.2025.02.008

Abstract （22）

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Microstructure of the as-cast Ti-6Al-4V titanium alloy was refined by deformation combined with heat treatment. Firstly, the as-cast Ti-6Al-4V titanium alloy was subjected to solution treatment at 1100 ℃ and water cooling to transform the microstructure into martensite. Then, the microstructure was refined by repeated rolling at 750 ℃. The results show that the principles of microstructure refinement are the deformation twinning, dislocation rearrangement, crystal rotation and discontinuous dynamic recrystallization.Through tensile test, it is found that compared to the as-cast Ti-6Al-4V titanium alloy, the alloy treated with microstructure refinement has a better strength-plasticity matching relationship. The improvement of alloy strength is the result of the combined effect of fine grain strengthening and dislocation strengthening. The improvement of plasticity is due to the formation of a plastic zone at the crack tip during crack initiation and propagation, which hinders crack propagation and enhances the plasticity of the material. In addition, dislocations can complete slip transmission between the α and β phases, which can better coordinate the deformation between the α and β phases and further enhance the plasticity of the material.

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Effect of Zr element on microstructure and properties of Cu-6Ni-3Ti alloy

Jing Qingxiu, Yang Xueqing, Wei Dandan, Wei Miao, Huang Xiaodong

Heat Treatment of Metals 2025, 50 (2): 61-68. doi:10.13251/j.issn.0254-6051.2025.02.009

Abstract （20）

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Effect of Zr content on the microstructure, mechanical properties and electrical conductivity of Cu-6Ni-3Ti-xZr alloy was investigated. The results show that zirconium elements mainly segregate at grain boundaries during solidification, forming zirconium-rich atomic clusters, slowing down the grain growth and inhibiting dendritic segregation. During the aging process, zirconium accumulates around the precipitated phases of the alloy, inhibiting the growth of the precipitated phases, and improving the hardness and its resistance to softening. When the content of zirconium elements is increased, Cu₄Zr is formed in the Cu-6Ni-3Ti-0.5Zr alloy. After aging at 450 ℃ for 2 h, the Cu-6Ni-3Ti-0.3Zr alloy has best mechanical and electrical properties, with tensile strength of 807 MPa, hardness of 230 HV2, electrical conductivity of 50%IACS.

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Analysis of continuous cooling transformation of 4Cr13 steel for plastic mold

Zhao Zhengrong, Zhang Yunfei, Zhao Yingli, Fan Mingqiang, Bai Lijuan, Liu Lijun

Heat Treatment of Metals 2025, 50 (2): 69-73. doi:10.13251/j.issn.0254-6051.2025.02.010

Abstract （21）

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4Cr13 steel for plastic mold was prepared by vacuum induction furnace, its phase transition points and continuous cooling transformation (CCT) curve were measured by using a DIL805A quenching thermal dilatometer, and its continuous transformation process was analyzed by combining microstructure observation and hardness test. The results show that the phase transition points of the tested 4Cr13 steel are Ac₁=857 ℃, Ac₃=937 ℃, and there are only pearlite transformation zone and martensite transformation zone on the CCT curve. The 4Cr13 steel has a good hardenability, and the martensitic transformation temperature range is 67-397 ℃.When the cooling rate is 0.01-0.05 ℃/s, the main product of phase transformation of the 4Cr13 steel is pearlite, and the hardness is low, which is 172-193 HV. When the cooling rate is 0.1-1 ℃/s, the microstructure is martensite and retained austenite, and the hardness is increased to 528-688 HV. When the cooling rate is ≥1 ℃/s, the martensitic transformation is completely finished.

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CCT and TTT curves of a carbide-free bainitic steel

Yang Siyuan, Li Aiguo, Luo Ping, Zhang Wenliang, Li Xianjun, Zhang Minghao, An Weicheng, Wang Kaize

Heat Treatment of Metals 2025, 50 (2): 74-80. doi:10.13251/j.issn.0254-6051.2025.02.011

Abstract （15）

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Continuous cooling transformation and isothermal transformation tests of undercooled austenite were carried out on a carbide-free bainitic tested steel by using the DIL-805A phase transformation tester. The CCT and TTT curves of the tested steel were obtained. The results show that the starting and ending transformation temperatures of austenite of the tested steel are 760 ℃ and 860 ℃, respectively, and the starting transformation temperature of martensite is approximately 300 ℃. When the cooling rate is between 0.1-15 ℃/s, the undercooled austenite mainly transforms to bainite+martensite complex structure. When the cooling rate is between 15-50 ℃/s, the undercooled austenite transforms into martensite. The microhardness of the tested steel increases with the increase of cooling rate, up to 742 HV0.5. When the tested steel undergoes isothermal transformation, the bainite transformation temperature range is 300-400 ℃, and the "nose tip" temperature is about 360 ℃.

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Differences and optimization practice of banded structure in gear steels

Zhang Zhixing, Guo Ziqiang, Wang Hailong, Qin Xuan

Heat Treatment of Metals 2025, 50 (2): 81-85. doi:10.13251/j.issn.0254-6051.2025.02.012

Abstract （17）

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A comprehensive study on the formation mechanisms and differences in the banded structure of commonly used automotive gear steels, namely SCr420H, 16MnCr5, 20CrMnTiH, SAE8620H and 22CrMoH, which possessed varying alloy element compositions but underwent similar smelting and rolling processes, was conducted. In addition, the process was optimized. The findings reveal that SCr420H, 16MnCr5 and 20CrMnTiH steels exhibit relatively less pronounced banded segregation, whereas 22CrMoH and SAE8620H steels display distinct banded structures. The alloying elements Mo and Ni in 22CrMoH and SAE8620H steels affect the microstructure transformation during rolling and cooling, resulting in the development of an abnormal microstructure, bainite, in the final rolled steel. By adjusting the continuous casting superheat to a range of 15-30 ℃, maintaining a consistent pulling speed, intensifying the crystallizer and secondary cooling, achieving a homogeneous rolling heating temperature of 1200-1240 ℃, ensuring a diffusion duration of at least 90 min, and maintaining a final rolling temperature of 910-960 ℃, the banded structure in SAE8620H round steel is effectively improved to a grade of ≤2.0.

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Effect of segregation on surface microstructure and hardness of induction hardened inner gear ring

Chen Yongxiang, Lü Hesheng, Yang Gang, Li Yong, Wang Chunli, Zhong Boying

Heat Treatment of Metals 2025, 50 (2): 86-89. doi:10.13251/j.issn.0254-6051.2025.02.013

Abstract （14）

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Segregation phenomenon of 42CrMoA steel inner gear ring was characterized, and the microstructure and hardness gradient of the induction hardened layer of the inner gear ring were analyzed. The results show that the microstructure of the 42CrMo steel inner gear ring forging is uneven, with severe banded structure and compositional segregation, which leads to uneven induction hardened layer structure, and the distribution of banded structure still exists. The banded structure and compositional segregation of inner gear ring forgings have a significant impact on the hardness gradient of the induction hardened subsurface and transition zone. The hardness gradient of the induction hardened subsurface and transition zone of the inner gear ring fluctuates greatly and exhibits a steep rise and fall phenomenon.

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Effect of partial austenite reverse transformation process on microstructure and mechanical properties of Fe-8Mn-0.2C-3Al medium Mn steel

Liu Mingzhu, Ding Hua, Zou Yuming

Heat Treatment of Metals 2025, 50 (2): 90-95. doi:10.13251/j.issn.0254-6051.2025.02.014

Abstract （16）

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Microstructure and mechanical properties of Fe-8Mn-0.2C-3Al medium Mn steel treated by partial austenite reverse transformation (PART) process with two-step annealing were studied by means of field emission scanning electron microscope, X-ray diffractometer and universal testing machine. The results show that for the tested steel treated by PART process with the increase of first step annealing temperature, the austenite content gradually decreases from 49.7% to 21.6%, and the microstructure is lath-like, the yield strength gradually increases, while the tensile strength and elongation gradually decrease. After treated at 755 ℃ for 15 min and 620 ℃ for 30 min, the tested steel obtains optimal mechanical properties, with the tensile strength of 1087 MPa, elongation of 43.4%, and the product of strength and elongation of 47.2 GPa·%, which is attributed to that the moderate austenite stability can fully utilize the TRIP effect during the tensile process and improve the comprehensive mechanical properties of the steel.

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Influence of austenite reverse transformation annealing temperature on microstructure and properties of Cu-containing medium manganese steel

Zhang Shenghao, Wang Bao, Li Sijia, Xiao Meimei, Zhou Jian'an

Heat Treatment of Metals 2025, 50 (2): 96-101. doi:10.13251/j.issn.0254-6051.2025.02.015

Abstract （17）

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Influence of austenite reverse transformation annealing temperature on microstructure evolution, mechanical properties and deformation behavior of 0.30C-5.21Mn-0.34Cu medium manganese steel was studied by means of SEM, EBSD, XRD and TEM. The results show that the microstructure of the steel after annealing is mainly composed of ferrite, retained austenite and martensite. As the annealing temperature increases, the content of retained austenite first increases and then sharply decreases, reaching a maximum of 20.38% at 700 ℃. As the annealing temperature increases, the tensile strength and yield strength of the tested steel show opposite changes. While the elongation and product of strength and elongation first increase and then decrease, which is basically consistent with the variation law of retained austenite volume fraction. When annealed at 700 ℃ for 60 min, the comprehensive mechanical properties of the tested steel are the best, with tensile strength, elongation, and product of strength and elongation reaching 1004 MPa, 54.80%, and 55.02 GPa·%, respectively.

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Effect of heat treatment temperature on microstructure and mechanical properties of salt bath quenched 65Mn steel

Yang Bin, Wang Lin, Shen Hangrui, Feng Songke, Li Guofei, Liu Fuqiang, Fang Liuxin, Yang Lin

Heat Treatment of Metals 2025, 50 (2): 102-106. doi:10.13251/j.issn.0254-6051.2025.02.016

Abstract （27）

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Focusing on the strict requirements for blade sharpness, hardness and wear resistance of chaff cutter blade, the balance between hardness and toughness of 65Mn steel was achieved through salt bath quenching with different heating temperatures and tempering. The microstructure, hardness, friction and wear resistance of the steel were studied systematically. The results show that when austenitizing at 840 ℃, the lath martensite of the 65Mn steel after quenching is smaller, together with clear acicular martensite. After tempering, the carbide in tempered martensite precipitates at the lath martensite interface, and its distribution is more uniform combined with smaller particle in the martensite matrix. The hardness of the steel after salt bath quenching at 840 ℃ and tempering is the highest, which is 58.04 and 53.50 HRC, respectively, combined with no excessively loss of the wear resistance for the 65Mn steel, meeting the application requirements of agricultural machinery materials. As a consequence, salt bath quenching at 840 ℃ and tempering is the optimal heat treatment process.

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Effect of rapid annealing temperature on evolution mechanism of microstructure and properties of SPCC steel for dust hoods

Hu Jingjing, Yuan Qing, Ren Jie, Xiong Le, Bao Linlin

Heat Treatment of Metals 2025, 50 (2): 107-113. doi:10.13251/j.issn.0254-6051.2025.02.017

Abstract （11）

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Based on the previously proposed rapid annealing method for SPCC steel, the influence of rapid annealing temperature on the relationship among grain size, orientation distribution, and mechanical properties of the SPCC steel was investigated. The results indicate that the rapid annealing temperature is a crucial factor affecting the size of ferrite grains. When the rapid annealing process is conducted at 650 ℃ for 100 s, the tensile strength of the SPCC steel can reach 487.09 MPa, with the elongation after fracture of 26.84% and the product of strength and elongation (PSE) of 13.07 GPa·%. At higher rapid annealing temperature, the grains become coarse, and the favorable {111} texture is enhanced, leading to a significant reduction in strength but a relatively high elongation. Conversely, at lower rapid annealing temperature, due to insufficient ripening of second-phase particles and no significant coarsening of ferrite grains, the material exhibits higher strength but a noticeable decrease in elongation. Furthermore, after grain refinement, the work-hardening ability of the material is diminished, and the {111} texture is weakened. The combined effect of these two factors results in a significant decrease in elongation compared to the traditional annealing methods under rapid annealing. Additionally, within a rapid annealing holding time of 100 s, a higher rapid annealing temperature facilitates a more uniform growth behavior among most ferrite grains, thereby improving the mixed grain structure of ferrite grains.

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Effect of peak temperature of thermal cycling on microstructure and properties of heat affected zone of G115 steel pipe

Chen Qian, Chen Zhengzong, Liu Zhengdong, Cai Wenhe, Jiang Haifeng, Bao Hansheng, He Xikou

Heat Treatment of Metals 2025, 50 (2): 114-120. doi:10.13251/j.issn.0254-6051.2025.02.018

Abstract （15）

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Heat affected zone (HAZ) of the G115 steel pipe was simulated by Gleeble-1500D thermal simulation machine, and the microstructure and hardness of the subregions of heat affected zone were analyzed by means of OM, SEM, EBSD, TEM and microhardness tester. The results indicate that the welded heat affected zone of G115 steel pipe is mainly divided into the coarse grain heat affected zone (CGHAZ) with coarse equiaxed grains, the fine grain heat affected zone (FGHAZ) with a fine mixed grain structure of large grains surrounded by crushed fine grains, and the intercritical heat affected zone (ICHAZ) with tempered martensite, which shows a little difference from the base metal. The geometric dislocation density of the fully phase-transformed microstructure (CGHAZ,FGHAZ) (24.1×10¹⁴, 24.5×10¹⁴ m^-2) is approximately twice that of the incompletely phase-transformed microstructure (ICHAZ) (13.6×10¹⁴, 11.8×10¹⁴ m^-2), meaning that there is a significant stress-strain gradient at the interface between ICHAZ and FGHAZ. Only a small number of M₂₃C₆and Laves phases are present within the FGHAZ, which can completely dissolve at higher temperatures. The complete dissolution temperature of the MX phase is higher, and it is still distributed in a small number in the CGHAZ. The Cu-rich phase only precipitates spherically within the grains at the ICHAZ. After the thermal simulation, the hardness and microstructure are positively correlated with the thermal cycling peak temperature. The microhardness of the CGHAZ, FGHAZ and ICHAZ near the base metal is 437.55, 421.85 and about 375 HV0.2, respectively.

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Effect of solution treatment and aging on microstructure and properties of laser powder bed fused FeCoNi alloy

Ye Guochen, Xia Zhonghu

Heat Treatment of Metals 2025, 50 (2): 121-127. doi:10.13251/j.issn.0254-6051.2025.02.019

Abstract （13）

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Effects of solution treatment and solution treatment+aging on microstructure and mechanical properties of the FeCoNi medium entropy alloy prepared by laser powder bed fusion were investigated. The results show that the microstructure of solution treated alloy is BCC single-phase structure, and during the solution process, the strip-shaped molten pool dissolves and the grains undergo recrystallization and coarsening. Granular Ni₃Fe phase precipitates at the grain boundaries and within the grains of the solution treated and aged alloy, and its content decreases with the increase of solution temperature. Solution treatment at 900 ℃ and aging at 470 ℃ refine the grain size of the alloy from 4.16 μm(solution treated) to 2.43 μm. During the solution treatment process, the disappearance of cellular structure and the release of residual stress result in a decrease in the hardness of the 900 ℃ solution treated alloy to 314 HV0.2 and a tensile strength of 709 MPa. After solution treatment and aging, Ni₃Fe intermetallic compounds precipitate from the matrix, which enhances the strength of the FeCoNi alloy. The hardness of FeCoNi alloy after solution treatment at 900 ℃ and aging at 470 ℃ is 508 HV0.2, and the tensile strength is 1238 MPa. The alloy strength is mainly contributed by precipitation strengthening and grain refinement strengthening. However, the accumulation of dislocations near the grain boundary precipitates can cause stress concentration, leading to a decrease in the plasticity of the FeCoNi medium entropy alloy.

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Effect of annealing temperature on mechanical properties of cold-rolled CoCrFeNi high entropy alloy

Jiang Mengyuan, Wu Zhennan, Wu Chengbo, Xu Wang, Li Ning, Dong Fuyuan

Heat Treatment of Metals 2025, 50 (2): 128-132. doi:10.13251/j.issn.0254-6051.2025.02.020

Abstract （17）

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A CoCrFeNi high entropy alloy was prepared by vacuum induction melting casting method, and the effect of different annealing temperatures on the mechanical properties of the CoCrFeNi high entropy alloy in -196 ℃ cryogenic rolling and room temperature rolling states was systematically studied. The results indicate that there is only FCC phase in the CoCrFeNi high entropy alloy in all the cold rolled and annealed states, and the percentage total extension at fracture and uniform elongation increase with the increase of annealing temperature, while the tensile strength decreases. Among them, the alloy in both the cold-rolled states has a good strength plasticity matching when annealed at 700 ℃. At the same annealing temperature, the strength of cryogenic rolled alloy is higher than that of alloy rolled at room temperature. There are numerous dimples distributed on the fracture of the as-cast CoCrFeNi high entropy alloy. The dimples on the fracture of the CoCrFeNi high entropy alloy in the two rolling states are few and shallow, and no dimple appears in some locations. As the annealing temperature increases, the size of the dimples increases and the number of pores increases.

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Effect of Nb addition and heat treatment on microstructure and properties of heterogeneous high carbon steel

Zhao Weinan, Lu Chao, Wang Haoyun, Cao Jianchun, Zhang Yongqing, Zhou Xiaolong

Heat Treatment of Metals 2025, 50 (2): 133-141. doi:10.13251/j.issn.0254-6051.2025.02.021

Abstract （14）

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High carbon steel Fe-0.86%C-0.04%Nb(mass fraction) was quenched at 1150 ℃ and tempered at different temperatures. The microstructure of the high carbon steel specimens under different heat treatment conditions was characterized by means of OM, SEM and EPMA. The macro and micro hardness tests were carried out by using Vickers hardness tester and nanoindentation tester, respectively, and compared with high carbon steel with the same C content. The effect of Nb on the microstructure and properties of high carbon steel was studied. The results show that the addition of Nb in high carbon steel can slow down the dissipation of C at the surface of specimen during quenching, and change the distribution of C at the core. The microstructure at the surface is martensite and retained austenite, and the microstructure at the core is composed of pearlite, proeutectoid ferrite and a small amount of martensite, and the heterostructure is obtained from the surface to the core. During tempering, Nb promotes the precipitation of fine granular carbides. After tempering at 300 ℃, the microstructure at surface of the high carbon steel specimen containing Nb is tempered martensite, and the microstructure of core is pearlite+ferrite+a small amount of tempered martensite, the Vickers hardness is 506 HV0.2 and 240 HV0.2, respectively, and the nanoindentation hardness of surface martensite and core pearlite is 4.20 GPa and 2.42 GPa, respectively. The surface has higher hardness, and the core has stronger toughness, showing the characteristics of hard surface and tough core.

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Interfacial structure evolution and mechanical properties of Mg/Al composite sheet by corrugated/flat-flat rolling

Zhu Jinsen, Bian Liping, Luo Baoquan, Li Teng, Wang Tao, Liang Wei

Heat Treatment of Metals 2025, 50 (2): 142-147. doi:10.13251/j.issn.0254-6051.2025.02.022

Abstract （12）

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Mg/Al composite sheet was prepared by corrugated/flat-flat rolling, and the composite sheet was subjected to final annealing treatment at 200 ℃ for 1 h. The microstructure evolution and mechanical behavior of the interface of the Mg/Al composite sheet were investigated by means of metallographic microscope, scanning electron microscope (SEM/EDS), electron backscatter diffractometer and universal electronic tensile machine. The results show that the metallurgical bonding is realized at the interface after the first pass of the both rolling methods and intermediate annealing at 400 ℃ for 15 min, and no intermetallic compound is formed at the interface. After the second pass of corrugated-flat rolling and 200 ℃×1 h annealing, the grain size of magnesium alloy matrix shows uneven distribution at the trough and peak, and the grains at the trough are significantly refined, but the grain size is larger than that of the flat-flat rolling, The “staggered occlusion” intermetallic compound particles are formed at the interface, and the compounds are dispersed along the corrugated interface, possessing better interface bonding characteristics. While a straight and continuous intermetallic compound layer is formed at flat-flat rolling interface. The corrugated-flat rolling process has the deformation characteristics of local strong pressure and strong shear. Compared to the flat-flat rolling, Mg/Al composite sheet has higher tensile strength and yield strength, and lower plasticity.

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Effect of Y addition and heat treatment on microstructure and properties of Al-Mg-Si-Y alloy

Bi Xiaoqin, Zhang Sen, Zheng Zeyuan, Qi Yulei, Fu Ying, Xu Qin

Heat Treatment of Metals 2025, 50 (2): 148-154. doi:10.13251/j.issn.0254-6051.2025.02.023

Abstract （9）

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Al-0.6Mg-0.5Si-xY (x=0, 0.1, 0.2, 0.3, 0.4) alloys were prepared and T6 heat treatment was carried out. The evolution of microstructure, electrical conductivity, and mechanical properties of the alloys after heat treatment were investigated. The results show that AlSiY phases are formed at the grain boundaries of the alloy with Y addition after heat treatment, and granular and rod-like AlSiY phases are precipitated in intragranular mode. The white granular Mg₂Si phases are dispersed in the alloy matrix. After heat treatment, the average grain size of the alloys is increased compared to their as-cast state, but it decreases with the increase of Y addition. After heat treatment, electrical conductivity of the alloys initially increases and subsequently decreases with the increase of Y content. The electrical conductivity reaches the highest value of 55.2%IACS by addition of Y with 0.3%, which is 1.7% higher than that of the as-cast alloy. After heat treatment, an increase in grain size of the alloys results in a reduction of grain boundaries, and the precipitation of solved Si atoms reduces the solid solution distortion, thereby improving the conductivity of the alloys. The tensile strength and hardness of the alloys after heat treatment exceed those of the as-cast alloy, exhibiting an initial increase followed by a subsequent decrease with the addition of Y. The tensile strength and hardness of the alloys reach the highest values of 206.2 MPa and 91.3 HV0.1 respectively by addition of Y with 0.3%, which are 36.6% and 40.5% higher than those of the as-cast alloy. The heat-treated alloys exhibit a significantly reduced elongation compared to the as-cast alloys. The heat treatment promotes a large amount of second phase precipitation in the alloys, thereby improving the strength and hardness of the alloys. However, the reduction in grain boundaries and the augmented presence of precipitated phases contribute to a diminished elongation in the heat-treated alloy compared to the as-cast alloy.

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Solution treatment and aging of 7055 aluminum alloy containing Ce

Fang Hongjie, Yang Yuzeng, Zhang Zhikai, Min Hong, Liu Zhendong, Shen Yuxin

Heat Treatment of Metals 2025, 50 (2): 155-159. doi:10.13251/j.issn.0254-6051.2025.02.024

Abstract （14）

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A 7055 aluminum alloy sheet containing 0.1%Ce was prepared in the laboratory, and different solid solution treatments (solution temperature of 465, 470, 475, and 480 ℃, holding time of 20, 40, and 60 min) and aging treatments (aging temperature of 120 ℃, holding time of 0-36 h) were carried out, and the microstructure and mechanical properties were observed and tested by using metallographic microscope, scanning electron microscope, transmission electron microscope, and electronic universal testing machine. The results indicate that there is a low melting point second phase at 470.83 ℃ in the cold-rolled alloy sheet. To avoid burning and reduce the mechanical properties of the sheet, the selection of the solid solution temperature should not exceed this temperature. The optimal solid solution and aging process for the alloy is 470 ℃×60 min+120 ℃×22 h. Under this process, the tensile strength is 577 MPa, the yield strength is 547 MPa, and the elongation is 9.47%.

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Influence of pre-deformation on stress relaxation aging behavior of 2195 aluminum-lithium alloy

Zhang Liwen, Liu Qiang

Heat Treatment of Metals 2025, 50 (2): 160-165. doi:10.13251/j.issn.0254-6051.2025.02.025

Abstract （10）

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Different pre-deformations (0%-10%) were performed on the naturally aged 2195 aluminum-lithium alloy. The effect of pre-deformation on the microstructure and mechanical properties of the 2195 aluminum-lithium alloy after stress relaxation aging was studied by means of stress relaxation aging test at 180 ℃ under initial loading stress of 250 MPa, mechanical tensile test at room temperature and scanning electron microscope observation. The results show that as the pre-deformation increases, the residual stress after stress relaxation of the alloy generally decreases and then increases. The alloy with 4% pre-deformation has the lowest residual stress, which is more conducive to the accumulation of creep strain. The stress relaxation curve of the alloy without pre-deformation shows four-stage characteristics, while that of the alloy with pre-deformation show two-stage characteristics, which is attributed to the difference in evolution of microstructure of the alloy with or without pre-deformation. The yield strength and tensile strength of the stress relaxation aged alloy increase with the increase of pre-deformation. The elongation after fracture of the stress relaxation aged alloy without pre-deformation is the smallest, while that of the stress relaxation aged alloy with 4% pre-deformation is the largest. The intrinsic reason for the superior comprehensive mechanical properties exhibited by stress relaxation aged alloy with 4% pre-deformation is the uniform distribution of small-sized T₁ strengthening phases within the grains and the relatively narrow precipitation free zones at the grain boundaries. The fracture mechanism of stress relaxation aged alloy without pre-deformation treatment is intergranular fracture, while under 4% and 10% pre-deformation conditions, the fracture mechanism is transgranular ductile fracture and transgranular cleavage fracture, respectively.

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Optimization of heat treatment process of 36CrNi3MoV steel forging for hot isostatic pressing machine

Shi Haopeng, Zhang Zhiyong, Shi Ruxing, Chen Ming, Dai Bojie, Kong Yuting

Heat Treatment of Metals 2025, 50 (2): 166-171. doi:10.13251/j.issn.0254-6051.2025.02.026

Abstract （10）

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Effects of quenching temperature, cooling method and tempering temperature on microstructure and mechanical properties of the 36CrNi3MoV steel forging for hot isostatic pressing machine were studied. The results show that when quenched between 770-860 ℃ and tempered at 600 ℃, the obtained microstructure is tempered martensite. With the increase of quenching temperature, the strength increases, while the impact property and plasticity decrease. When quenched with different cooling methods, the water quenched microstructure is the most uniform. The strength of water quenched steel is slightly higher than that of oil quenched. When tempered in the range of 580-620 ℃, with the increase of tempering temperature, the strength decreases, but the impact property and plasticity increase. The optimal heat treatment process consists of austenitizing in the range of 830-860 ℃, water quenching and then tempering at 600 ℃,which can achieve mechanical properties that meet the design requirements and NB/T 47008-2017.

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Research progress of induction hardening technology for ball screw

Li Mingzhe, Chen Baofeng, Sun Lizhuang, Zhang Wenliang, Zhang Lun, Liu Junjie

Heat Treatment of Metals 2025, 50 (2): 172-180. doi:10.13251/j.issn.0254-6051.2025.02.027

Abstract （14）

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Induction hardening technology, as an advanced metal surface heat treatment strengthening method, can effectively improve the hardness and wear resistance of ball screws, thereby significantly extending their service life and performance stability. The key technical issues and challenges faced by induction hardening technology for ball screws were summarized, and its main research progress, covering basic principles, application of simulation technology, optimization of process parameters, specialized equipment, and other aspects, were systematically over viewed. Based on these, the prospects of induction hardening technology in the screw manufacturing industry were discussed.

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Effect of annealing temperature on hot-rolled microstructure and texture of 1.45%Si non-oriented silicon steel

Xuan Dongpo, Guo Han, Xu Ning, Dong Linshuo, Zhang Jian, Li Zhijian, Liu Xuming

Heat Treatment of Metals 2025, 50 (2): 181-186. doi:10.13251/j.issn.0254-6051.2025.02.028

Abstract （15）

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Effect of different annealing temperatures on the hot-rolled plate of 1.45%Si non-oriented silicon steel was studied in order to guide the heat preservation process of the hot-rolled plate and provide a theoretical basis for its non-normalizing production. The results show that the microstructure of the hot-rolled plate has a large gradient along the thickness direction, and the surface layer, the subsurface layer and the center layer are equiaxed grains, deformed grains and fine equiaxed grains and deformed grains, respectively. With the increase of annealing temperature, the recrystallization ratio of hot-rolled plate gradually increases from 32.8% to 96.8%, and the microstructure of hot-rolled plate gradually uniform, the grain size of hot-rolled plate reaches 51.4 μm after annealing at 740 ℃ for 2 h, the γ texture and Goss texture in hot-rolled plate continue to decrease, and the λ texture gradually increases. Complete recrystallization can occur after annealing at a temperature higher than 740 ℃ for 2 h. In actual production, the hot-rolled coil crimp temperature (≥700 ℃) should be increased as much as possible, and the hot-rolled coil should be quickly stored in the slow cooling pit for insulation, so that complete recrystallization can occur as much as possible. Finally, after cold rolling and recrystallization annealing, the final product has excellent magnetic properties.

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Effect of heat treatment process on mechanical properties at room temperature and high temperature of TC21 titanium alloy

Jiang Long, Zhao Wenpu, Zhang Chaoqun

Heat Treatment of Metals 2025, 50 (2): 187-193. doi:10.13251/j.issn.0254-6051.2025.02.029

Abstract （11）

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TC21 titanium alloy with different α phase lamella distributions was prepared by designing different heat treatment processes, and the precipitation of secondary α phase was controlled by aging. Combined with the results of mechanical property testing and analysis at room temperature and high temperatures, the effect of heat treatment on mechanical properties at room temperature and high temperatures of the TC21 titanium alloy was studied. The results show that after solution treatment at 980 ℃, following by annealing at 770 ℃, 810 ℃ and 850 ℃, respectively, the strength at room temperature of the alloy decreases with the increase of annealing temperature, while the plasticity increases. After annealing and aging at 550 ℃ for 4 h, the strength at room temperature of the alloy increases with the increase of annealing temperature, while the plasticity shows the opposite trend. With the increase of tensile test temperature, the plasticity of the TC21 titanium alloy treated by different processes is improved, and the strength retention rate is above 65% at 500 ℃, and the strength of TC21 titanium alloy annealed at 850 ℃ and aged at 550 ℃ is higher when used below 500 ℃.

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Effect of annealing treatment on microstructure and mechanical properties of electron beam welding TC17 titanium alloy

Bian Hongyou, Liu Mingsong, Liu Weijun, Liu Yanshuo, Yu Xingfu

Heat Treatment of Metals 2025, 50 (2): 194-199. doi:10.13251/j.issn.0254-6051.2025.02.030

Abstract （12）

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Effect of annealing on the microstructure and mechanical properties of TC17 titanium alloy welded joint was studied by means of metallographic microscope, scanning electron microscope, hardness tester, and tensile testing machine. The results show that dynamic recrystallization occurs in the weld seam of the TC17 titanium alloy, and metastable β grains are formed, and there is no obvious second phase in the grains, which leads to softening of the weld zone. As the distance from the weld seam gets closer, the aspect ratio of the primary α phase in the heat affected zone decreases and the secondary α phase dissolves gradually, resulting in a gradual decrease in microhardness. After annealing at 600 ℃ for 4 h, the hardness of weld seam is increased by 41% compared with that of the welded state, and the hardness of heat affected zone is increased by 12.8% compared with that of the welded state. Due to the fine and dispersed secondary α phase precipitated in the metastable β phase in both the weld and heat affected zone, the microhardness of weld and heat affected zone is increased significantly compared with the welded state. The properties of the welded joint are mainly determined by the size and quantity of α phase. After annealing, the α phase has obvious strengthening effect, the tensile strength of the welded joint is increased by 14% compared with that of the welded state, and the tensile strength of joint is higher than that of the substrate, thus the fracture position of the joint is on the substrate.

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Effect of finish rolling process on precipitation hardening of TiC in a titanium microalloyed steel

Wang Rui, Cui Yan, Peng Xiying, Feng Yunli, Sun Xinjun, Yong Qilong

Heat Treatment of Metals 2025, 50 (2): 200-205. doi:10.13251/j.issn.0254-6051.2025.02.031

Abstract （12）

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Nucleation parameters of TiC precipitation in austenite (γ) in a Ti microalloyed high-strength steel were calculated according to the solid solution precipitation theory and classical nucleation growth dynamics theory of binary precipitates. Then the TiC precipitation-time-temperature (PTT) curve and TiC nucleation rate-temperature (NrT) curve were drawn. The effects of finish rolling on the TiC nucleation rate, TiC precipitation rate, strength, and hardness were also studied. The results show that the temperature of the maximum nucleation rate of deformation-induced TiC precipitation is 740 ℃, the fastest precipitation temperature is 820 ℃, and the corresponding finish rolling temperature for the maximum hardness is 880 ℃. When the finish rolling temperature is 780-830 ℃, the rate of deformation-induced TiC precipitation is not significantly affected by temperature and has almost no effect on the hardness. As the finish rolling temperature increases from 830 ℃ to 880 ℃, the rate and precipitation amount of deformation-induced TiC precipitation decrease, promoting an increase in the amount of fine TiC precipitation during coiling, an increase in precipitation hardening effect, and an increase in hardness. When the finish rolling temperature is higher than 880 ℃, the hardness decreases due to the increase in grain size.

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Effect of heat treatment parameters on surface contamination layer of Ti80 titanium alloy plate

Zhang Qiang, Liu Feng, Hao Xiaobo, Wang Fei, Yu Dongdong, Liu Xibo, Li Bobo

Heat Treatment of Metals 2025, 50 (2): 206-211. doi:10.13251/j.issn.0254-6051.2025.02.032

Abstract （12）

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Effects of heat treatment temperature and holding time on surface contamination layer of the Ti80 titanium alloy plate under atmospheric conditions and with/without surface anti-oxidation coating were studied by using metallographic method. The results show that when without surface anti-oxidation coating, as the heat treatment temperature increases and the insulation time prolongs, the thickness of the surface contamination layer on the Ti80 alloy plate continues to increase. When heat treated at 800-900 ℃, the surface contamination layer is relatively thin and easy to remove. However, when heat treated at 965-990 ℃, the removal of the surface contamination layer is difficult. When with surface anti-oxidation coating, the coating composition and coating thickness have a significant impact on the thickness of surface contamination layer on the Ti80 alloy plate. Choosing the appropriate type of coating and ensuring a certain coating thickness can significantly reduce the thickness of surface contamination layer on the Ti80 alloy plate after high temperature heat treatment, but it can not completely eliminate the surface contamination layer.

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Nb element segregation behavior and homogenization law of GH2909 superalloy

Qi Huilin, Guo Xulong, Chen Qi, Zhou Yang

Heat Treatment of Metals 2025, 50 (2): 212-217. doi:10.13251/j.issn.0254-6051.2025.02.033

Abstract （11）

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Theoretical homogenization process of GH2909 alloy was calculated via JMatPro and homogenization experimental verification was conducted for the as-cast alloy at 1130 ℃ to 1190 ℃. Microstructure, element segregation and dissolution of Laves phase of the as-cast and homogenized GH2909 alloy were characterized by means of metallurgical microscope, scanning electron microscope and electronic probe. After heat treatment at 845 ℃ for 4 h and then air cooling for the homogenized GH2909 alloy, the distribution of needle-like η phase was observed, in order to evaluate homogenization effect of the GH2909 alloy. The results show that a mass of low melting point Laves phase exists in the as-cast GH2909 alloy and Nb element is the most important segregation element. Laves phase dissolves completely in the GH2909 alloy after 1150 ℃×7 h or 1130 ℃×10 h homogenization treatment. After complete Laves phase dissolution, 1190 ℃×35 h homogenization treatment decreases segregation coefficient to 1.046 and residual segregation coefficient to 0.059 of Nb element. After heat treatment at 845 ℃ for 4 h and air cooling for homogenized specimens, Nb-rich needle-like η phase precipitates along grain boundary and in grain with uniform diffusion of Nb element. Combining segregation coefficient with η phase precipitation behavior, 1150 ℃×7 h+1190 ℃×35 h homogenization treatment can realize complete homogenization of the GH2909 alloy.

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Effect of cooling rate on microstructure of high reliability SAC-SBN alloy and its solder joints

Xia Ziqi, Cao Dali, Cao Lihua, Zhao Lingyan, Yang Jiaojiao

Heat Treatment of Metals 2025, 50 (2): 218-224. doi:10.13251/j.issn.0254-6051.2025.02.034

Abstract （10）

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In order to optimize the welding process of high reliability solder SAC-SBN alloy for automotive electronics, the influence of different cooling rates on microstructure of the SAC-SBN solder alloy and its solder joints was investigated. The test results indicate that the microstructure of the SAC-SBN alloy gradually coarsens with the decrease of cooling rate. Under the condition of a cooling rate of 48 ℃/s, the refinement degree of the alloy structure is optimal, while at a cooling rate of 0.13 ℃/s, the intermetallic compound (IMC) coarsens in the alloy and the Bi element exhibits grain boundary segregation. Compared with traditional SAC305 alloy, the SAC-SBN solder joints have a larger number and smaller size of IMC grains at the solder joint interface, which is attributed to the precipitation of Bi element at the interface grain boundary, which promotes the heterogeneous nucleation growth of (Cu, Ni)₆Sn₅. When the cooling rate is 48 ℃/s, the IMC layer at the SAC-SBN solder joint interface is the thinnest, as 1.96 μm. However, due to the difference in thermal expansion coefficients, the stress at the interface is relatively high, and voids appear in the IMC layer at the interface. When the cooling rate is 0.13 ℃/s, the IMC layer of the solder joint is the thickest, as 3.18 μm. And due to the interface reaction and maturation mechanism, there is stress between the Sn alloy matrix and IMC, resulting in voids in both the IMC layer at the interface and the (Cu,Ni)₆Sn₅ that has matured and grown inside the solder. When the cooling rate is 1.33 ℃/s, the solder joint structure is fine and there are no obvious defects.

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Hot rolling process of non-tempered bainitic steel pipe for oil drilling

Ma Lina, Wang Xiaoyu, Nie Shunuo, He Jiaqi, Ouyang Siyi, Niu Sai, Wu Meng

Heat Treatment of Metals 2025, 50 (2): 225-229. doi:10.13251/j.issn.0254-6051.2025.02.035

Abstract （12）

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Effects of reheating temperature, cooling rate after rolling and tempering temperature on the microstructure and properties of hot-rolled non-tempered bainitic steel pipe for oil drilling were studied by laboratory heat treatment simulation. The results show that the reheating temperature decreases from 930 ℃ to 850 ℃, the sizes of bainite and lath martensite become smaller, and the impact absorbed energy of air-cooled tested steel increases from 19.48 J to 35.26 J. When reheated at 850 ℃, the microstructure is lath and packet martensite and granular bainite, the impact absorbed energy of air cooled tested steel is higher than that of furnace cooled. However, the impact property of the tested steel decreases after tempering at 300-400 ℃. In the actual production, the reheating temperature of the steel pipe during hot rolling should be properly reduced, and the cooling rate after rolling should be properly accelerated, so as to obtain the high toughness of the non-tempered bainitic steel pipe.

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Changes in microstructure and properties of TP347HFG steel aged at 700 ℃

Song Tao, Xing Honggen, Wang Zhiwu, Zhang Yonglin

Heat Treatment of Metals 2025, 50 (2): 230-234. doi:10.13251/j.issn.0254-6051.2025.02.036

Abstract （11）

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By using SEM, EDS, TEM, universal testing machine and Brinell hardness tester, the changes in microstructure and properties of TP347HFG steel in as-received state and different aged states (aged at 700 ℃ for 500, 800, 1500, 2500, 3650 h) were analyzed. The results show that the relationship of total amount of precipitated phases vs aging time during the aging process of the TP347HFG steel at 700 ℃ is as follows: y=0.060-9.956×10^-5x+2.912×10^-7x²-2.707×10^-11x³-7.719×10^-15x⁴. The precipitated phase of the as-received TP347HFG steel is fine primary phase Nb(C, N). After aging for 500 h, M₂₃C₆ carbides precipitate and grow at the grain boundaries, and a small amount of σ phase appears after aging for 3650 h. After aging for 500 h, the fine second phase on the grain boundaries inhibits grain boundary slip, improves the hardness and strength, but reduces the material plasticity. After aging for 800 h, the precipitation of hard and brittle M₂₃C₆ carbides and the decrease in twinning quantity reduce the strength of the steel. After aging for 1500 h, the fine secondary Nb(C, N) plays a role in dispersion strengthening, increasing the strength and reducing the plasticity of the steel. When aged to 3650 h, with the coarsening of precipitated phases, the hardness value of the steel is decreased, the strength is slightly decreased, and the plasticity is slightly improved.

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Pre-heat treatment process for large size NiCrMoV steel forgings

Li Guang, Qin Hongfu, Li Jie, Su Wenbo, Li Liangyu, Jin Ming

Heat Treatment of Metals 2025, 50 (2): 235-240. doi:10.13251/j.issn.0254-6051.2025.02.037

Abstract （17）

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In response to the problem of coarse grain and structural inheritance of high hardenability NiCrMoV steel forgings after forging, a process experiment using small-sized specimens was used to analyze the effect of heat treatment schemes such as pre-treatment before normalizing, multiple high-temperature normalizing treatments, two-phase region high-temperature side normalizing and annealing for cutting off the structural inheritance and for grain refinement. According to the size and shape characteristics of the rotor core shaft forgings, the optimal pre-heat treatment process scheme was developed, and control measures for austenitizing heating temperature and time and cooling process were proposed. The results show that after the optimal pre-heat treatment, the actual grain size of the actual produced large size forging body is sampled and tested as grade 6.5, and the ultrasonic testing of the forging meets the ø2 mm initial sensitivity requirement.

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Influence of heat treatment process on microstructure and properties of SDP80C steel

Chen Shengnan, Peng Ruizhi, Wu Xiaochun

Heat Treatment of Metals 2025, 50 (2): 241-246. doi:10.13251/j.issn.0254-6051.2025.02.038

Abstract （9）

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Austenite continuous cooling transformation curve of pre-hardened die casting steel SDP80C was measured by using a thermal dilatometer, and the microstructure and mechanical properties under different aging processes were studied. The results show that the martensitic transformation starting temperature (Ms) of the SDP80C steel is 320 ℃, the austenite transformation starting temperature (Ac₁) is 695 ℃, and the austenite transformation ending temperature (Ac₃) is 841 ℃. Within the aging temperature range of 525-600 ℃, the increase of aging temperature promotes the formation and growth of NiAl phase and Cu-rich phase, and the martensite recovers. As a result, the hardness of the SDP80C steel gradually decreases while the impact property improves. After aging at 525 ℃ for 2 h, the SDP80C steel reaches the maximum hardness of 44.9 HRC and the impact absorbed energy is about 123 J, which is attribute to the precipitation strengthening of nano-scale NiAl phase and Cu-rich phase.

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Effect of austenitizing temperature on microstructure and properties of 1500 MPa cold-rolled Q&P steel

Cai Shunda, Xin Lifeng, Song Liwei, Ruan Guoqing, Sun Rongsheng, Zhong Lili

Heat Treatment of Metals 2025, 50 (2): 247-250. doi:10.13251/j.issn.0254-6051.2025.02.039

Abstract （11）

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Effect of austenitizing temperature on microstructure, retained austenite content and mechanical properties of 1500 MPa grade Q&P steel was studied by means of optical microscope, scanning electron microscope, X-ray diffractometer and tensile testing machine. The results indicate that the tested steel is composed of ferrite, martensite and retained austenite austenitized at different temperatures, slow cooled, quenched and partitioned, but there are significant differences in the content of each phase and grain size. After the same slow cooling, quenching and partitioning process, the content of martensite and retained austenite significantly increases during intercritical austenitizing (750, 800 ℃), while there is no significant difference in the proportion of phases between high-temperature intercritical austenitizing at 800 ℃ and complete austenitizing at 850 ℃. The average grain size of the tested steel decreases with the increase of austenitizing temperature. The volume fraction of retained austenite in the tested steel austenitized at 750, 800 and 850 ℃ is 8.7%, 13.3% and 12.0%, respectively. The comprehensive mechanical properties of the tested steel are optimal when austenitized at 800 ℃, with a yield strength of 1169 MPa, tensile strength of 1503 MPa and elongation of 13.3%. The mechanical properties are mainly affected by the phase proportion, fine grain strengthening effect and retained austenite distribution.

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Effect of diffusion time on microstructure and hardness of 20CrMnTi steel after vacuum low-pressure carburizing

Yu Penghan, Yan Haoming, Yang Shuai, Yu Xingfu, Liu Yongji, Dai Yougui

Heat Treatment of Metals 2025, 50 (2): 251-255. doi:10.13251/j.issn.0254-6051.2025.02.040

Abstract （11）

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20CrMnTi carburizing steel was subjected to vacuum carburizing treatment by using vacuum low-pressure pulse carburizing technology and quenching and tempering treatment, and the effect of diffusion time on the carbon concentration of the carburized layer, hardness, and microstructure was analyzed. The results show that after vacuum low-pressure pulse carburizing, when the diffusion time is short, e. g., 1125 min, due to the large surface carbon concentration gradient, significant internal stress is generated between the surface and subsurface layers, which can easily lead to internal cracks. When the diffusion time extends to 2125 min, the surface carbon content significantly decreases from 1.30% to 0.80%, the carbon content changes slowly from the surface to the core, and the surface hardness changes smoothly. When the diffusion time is short, after quenching, large-sized carbides and a large amount of retained austenite are observed in the surface layer. When the diffusion time prolongs, the carbide size and retained austenite content in the surface structure are significantly reduced. After 960 ℃ pulse vacuum low-pressure carburizing treatment for 52 min+diffusion for 2125 min, cooling to 840 ℃ for oil quenching, and then tempering at 180 ℃ for 2 h, the carbide in the carburized layer is grade 1, the core microstructure is grade 2, and the effective depth of carburized layer is about 3.12 mm, and the hardness changes smoothly from the surface to core, meeting the requirements of carburizing.

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Effect of normalizing process on microstructure and properties of large nodular cast iron travel wheel containing Cu

Xiao Jieliang, Sun Hao, Li Fei, Hu Ping, Xie Yang, Chen Jinggang

Heat Treatment of Metals 2025, 50 (2): 256-259. doi:10.13251/j.issn.0254-6051.2025.02.041

Abstract （11）

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A normalizing process experiment was conducted on a large travel wheel made of nodular cast iron containing 0.460% Cu, and the effect of normalizing temperature (850 ℃ and 880 ℃) on the microstructure and mechanical properties of the travel wheel flange and spoke was studied. The results show that the large nodular cast iron travel wheel containing Cu can only obtain partial pearlite after low-temperature normalizing at 850 ℃, and there is still 25% to 30%(volume fraction) fragmented ferrite, resulting in the strength of the wheel flange not meeting the requirements. After normalizing at 880 ℃ (fan blown cooling) and tempering at 550 ℃, the mechanical properties of the flange and spoke can meet the requirements. More pearlite forms when normalized at 880 ℃ than that at 850 ℃. This is because as the normalizing temperature increases, the carbon content in austenite increases, the stability of undercooled austenite increases, and the C-curves shift to the right, making it easier to obtain pearlite during cooling. For the tested large nodular cast iron travel wheels, a higher normalizing temperature such as 880 ℃ is preferred.

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Carburizing and quenching treatment of 18CrNiMo7-6 steel gear with small and medium modulus

Li Yao, Zhang Wei, Li Chaoqing

Heat Treatment of Metals 2025, 50 (2): 260-263. doi:10.13251/j.issn.0254-6051.2025.02.042

Abstract （13）

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Using orthogonal test, different processes of carburizing and quenching treatment were carried out on small and medium modulus gear made of 18CrNiMo7-6 steel, and the surface hardness, effective hardening layer depth, and microstructure after heat treatment were analyzed. The results show that the heat treatment processes with a strong carburizing potential of 1.10% and a diffusion carbon potential of 0.65%-0.85%, quenching time of 1.5 h and tempering time of 4 h, as well as quenching time of 1.0 or 1.5 h and tempering time of 6 h, can all achieve a surface hardness of over 59 HRC for the 18CrNiMo7-6 steel gear, and the effective hardening layer depth and microstructure meet the technical requirements. However, the microstructure observation finds that under the process of diffusion carbon potential of 0.85%, quenching time of 1.5 h, and tempering time of 4 h, both the carbides and retained austenite are at critical values, and there is a risk of exceeding the standard during mass production. After comprehensive consideration, the optimum carburizing and quenching process for the tested 18CrNiMo7-6 steel gear is determined as follows: strong carburizing potential of 1.10%, tempering time of 6 h, as well as diffusion carbon potential (0.65%-0.85%) matched with quenching time (1.0-1.5 h) by contour method.

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Rapid and uniform temperature dropping method for heat treatment furnace

Liu Penghan, Zhou Chun, Li Zhengtao, Wen Changfei, Han Bing, Liu Yujia, Li Jiadong

Heat Treatment of Metals 2025, 50 (2): 264-267. doi:10.13251/j.issn.0254-6051.2025.02.043

Abstract （15）

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A novel rapid temperature adjusting method is proposed and experimentally validated to find a solution to the issues of low temperature dropping efficiency and uneven temperature distribution in traditional roller hearth open-flame heat-treatment furnace. Traditional methods rely on natural cooling or simple forced air cooling systems, resulting in slow cooling rates (66 h to cool from 600 ℃ to 200 ℃) and uneven temperature distribution. This leads to significant variations in the mechanical properties of the steel plates, impacting product quality and production efficiency. The novel cooling method integrates five measures: ① alternating pulse cooling of the burners to improve both cooling rate and temperature uniformity; ② increasing furnace negative pressure while raising the furnace door to enhance cold air intake; ③ increasing the exhaust fan frequency to control furnace pressure; ④ auxiliary cooling by steel plate, large-specification steel plates to absorb heat; and ⑤ accelerating hot gas turbulence by increasing the frequency of the top circulating fan to promote better heat mixing within the furnace. Comparative tests on a roller hearth annealing furnace demonstrate that the novel method reduces the cooling time from 600 ℃ to 200 ℃ to 26.9 h, representing at least a two-fold increase in cooling rate. Mechanical property tests show that the steel plates treated with the novel method exhibit significantly lower transverse variations in tensile strength and yield strength (less than 0.40% and 0.41%, respectively) compared to the traditional method. This novel method significantly improves the production efficiency, enhances product quality, and offers substantial economic and environmental benefits.

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Prediction of critical temperature A₁ and A₃ of medium-Mn steel based on machine learning models

Zhang Zhiye, Wang Yan, Zhang Biao, Ji Ze, Liu Yaliang, Zhang Minghe, Feng Yunli

Heat Treatment of Metals 2025, 50 (2): 268-277. doi:10.13251/j.issn.0254-6051.2025.02.044

Abstract （15）

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In order to facilitate the design of heat treatment process of medium-Mn steel, a machine learning model for predicting the critical temperature A₁ and A₃ of medium-Mn steel was optimized. The critical temperature data of 496 groups of medium-Mn steels with different compositions were obtained by Thermal-Calc simulation software. Mn, Al and C compositions were taken as input characteristics, and phase transition temperatures A₁ and A₃ were taken as output targets. Three indexes of root mean square error (RMSE), mean absolute error (MAE) and determination coefficient (R²) were used to evaluate the prediction effect of the model. From seven machine learning models (LR, DT, SVM, GPR, Boosting, Bagging and ANN), the GPR model for predicting A₁ and the GPR and ANN model for predicting A₃ were screened. The results show that the GPR model for predicting A₁ has sufficient accuracy, that is the optimal model for A₁. The grid search method is used to adjust the hyperparameters of the preliminary model for predicting A₃, and the optimal model of A₃ (single-layer ANN model) is obtained. According to the chemical composition of medium-Mn steel in the applied literature, A₁ and A₃ are predicted by using the optimal model. The overall MAE of the predicted value and measured value of A₁ and A₃ is 9.95 ℃ and 13.57 ℃, respectively, and the minimum difference is 0.30 ℃ and 6.20 ℃, respectively, indicating that the model has high accuracy and can be used to predict the critical temperature of medium-Mn steel.

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Simulation calculation of heating efficiency of heat treatment furnace based on ANSYS Fluent

Yu Liang, Zhang Fei, Tian Tong, Liu Yujia

Heat Treatment of Metals 2025, 50 (2): 278-281. doi:10.13251/j.issn.0254-6051.2025.02.045

Abstract （15）

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To improve the heating efficiency of the heat treatment furnace, a design scheme of adding nozzles on the top of furnace was proposed. The flow field distribution inside the furnace at different firing rates (0-120 m/s) of the furnace top nozzles was simulated by ANSYS Fluent software, and the temperature rise changes of the steel plates inside the furnace at different firing rates (30-210 m/s) were analyzed. The results show that after adding nozzles on the top of furnace, the flow field distribution inside the furnace is more uniform, and as the nozzle firing rate increases, the gas flow becomes more stable and uniform, and the temperature distribution inside the furnace becomes more uniform. At different nozzle firing rates, the heating rate of the steel plate in the furnace increases with the increase of firing rate, but beyond a certain threshold, the increase in heating rate of the steel plates is limited. It can be seen that adding nozzles on the top of furnace and optimizing the firing rate parameters can significantly improve the heating efficiency of the heat treatment furnace.

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Influence of WC content on microstructure and wear resistance of AlCrFe₂Ni₂Mo_0.9 high-entropy alloy coatings

Wang Qingtian, Man Jiao, Wang Juncheng, Liu Genggen, Yang Bin

Heat Treatment of Metals 2025, 50 (2): 282-291. doi:10.13251/j.issn.0254-6051.2025.02.046

Abstract （12）

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By adding spherical WC particles with mass fraction of 10% to 30% to AlCrFe₂Ni₂Mo_0.9 high-entropy alloy powder, the coatings with various WC contents were prepared on 316L stainless steel by using high-velocity laser cladding technology. The effect of WC content on the phase composition, microstructure, element distribution, hardness, and wear resistance of the coatings was systematically evaluated by means of X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, microhardness tester, and friction wear tester. The results indicate that, without WC addition, the coating mainly consists of FCC phase, BCC phase and σ phase. As the WC content increases, the diffraction peak intensities of the BCC and σ phases gradually weaken, while that of the FCC phase strengthens. When the WC content reaches 30%, the phase composition is in a state where FCC phase and Fe₃W₃C phase coexist. With the increase of WC content, the microstructure of the coating transitions from dendritic to a more uniform equiaxed crystal morphology, significantly enhancing the fine grain strengthening effect. Simultaneously, partial dissolution of WC particles promotes the formation of an alloyed reaction layer and fishbone-like structures. As the WC content increases from 0% to 30%, the microhardness and wear resistance of the coating show a trend of first decrease and then increase, ultimately reaching the highest hardness of 567.22 HV at 30% WC content, along with the best wear resistance, reducing the wear rate to 0.68×10^-5 mm³·N^-1·m^-1, with a friction coefficient of 0.386.

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Effects of activators and surface laser-quenching on low-temperature pack aluminizing of TC4 titanium alloy

Lu Jiacheng, Tian Xiaodong

Heat Treatment of Metals 2025, 50 (2): 292-297. doi:10.13251/j.issn.0254-6051.2025.02.047

Abstract （13）

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Effects of activators and surface laser-quenching pretreatment on low-temperature aluminizing of TC4 titanium alloy were studied. The solid powder pack cementation aluminizing of TC4 alloy was conducted between 550-700 ℃ for 4 h with three different activators of NH₄Cl, NH₄F and NaF, respectively, in the pack mixture, and the aluminizing of TC4 alloy substrate after surface laser-quenching was carried out. The cross-sectional morphology, element content and surface phase of the aluminized layers were analyzed by means of scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-Ray diffractometer (XRD). The results reveal that the three activators, NaF, NH₄F and NH₄Cl, can make Al content increase from 10.04% to 11.56%, 15.66% and 16.96%, respectively, of the surface layer of TC4 alloy after 700 ℃×4 h pack aluminizing. Compared with the Al content of the substrate, it is increased by 15.1%, 56.0% and 68.9%, respectively. The catalytic permeation effect of NH₄Cl is the best, followed by NH₄F, and the effect of NaF is the worst. The experiment results and the thermodynamic analysis are coincident. When the holding temperature drops to 600 ℃, there is almost no change in the surface Al content of the specimen after aluminizing. However, surface laser-quenching pretreatment of TC4 alloy substrate can refine the surface grain size and promote low-temperature aluminizing. After surface laser-quenching of TC4 alloy, the surface average grain size of α-Ti phase decreases continuously with the increase of laser power. When surface laser-quenched under 240 W, the average grain size of α-Ti phase is reduced by 47.9% compared with that without laser-quenching, and after four times laser-quenching at this power, the average grain size of α-Ti phase can be reduced by 68.6% than that without laser-quenching. The reduction of grain size of α-Ti phase on surface layer can promote the diffusion of aluminum in the surface layer, of which the content increases from 10.04% to 15.54% after 600 ℃×4 h aluminizing.

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Influence of PIP/LQ composite process on properties of gun steel

Luo Yisong, Wang Fangzhou, Zhu Wei, Chen Shengyi, Luo Defu

Heat Treatment of Metals 2025, 50 (2): 298-303. doi:10.13251/j.issn.0254-6051.2025.02.048

Abstract （11）

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A composite treatment combining the advantages of two processes, PIP (Programable ion permeation) and laser quenching (LQ) for the gun steel material 25Cr3Mo3NiNbZr steel was performed to enhance its surface properties. After pretreatment of quenching and tempering, the tested steel was treated with PIP followed by laser quenching at different scanning speeds. Properties of the specimens were characterized by metallographic observation, XRD analysis, microhardness test, electrochemical corrosion and neutral salt spray test. The results show that scanned at the laser energy density of 2.31-3.00 J/mm², part of the compound layer decomposes, reducing the surface hardness, nitrogen-containing martensite generates in the diffusion layer, and the peak hardness of the subsurface layer is improved. Laser scanning speed of 39 mm/s (laser energy density of 2.31 J/mm²) is determined for the optimum process, when scanned at this speed, the microstructure is refined, more nitrogen-containing martensite transforms, less nitrides lose in the surface layer, and the eggshell effect is effectively alleviated. The corrosion resistance of the PIP/LQ composite process treated specimens is lower than that of the PIP treated specimens but still higher than that of the untreated specimens. It is concluded that the PIP/LQ composite process is feasible to improve the surface properties of gun steel.

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Common failure problems and corresponding strategies for walking wheels of coal mining machines

He Xiao, Xu Hongxiang, Shi Lubing, Chen Shengchao, Li Ziyan, Rong Zeyu, Li Fuli

Heat Treatment of Metals 2025, 50 (2): 304-311. doi:10.13251/j.issn.0254-6051.2025.02.049

Abstract （19）

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Walking wheel, as the actuator of the walking device of the coal mining machine, often suffers from tooth breakage accidents due to the effect of strong impact loads. This seriously affects the working efficiency and poses a threat to the personal safety of the operators. Thus firstly, the failure modes of the walking wheel, such as wear, tooth breakage, spalling and plastic deformation of the tooth surface were expounded. Subsequently, for the tooth breakage failure, the coping strategies were summarized, including optimizing the product design, rationally selecting materials, increasing the gear modulus, installing protective devices and optimizing the heat treatment process. Finally, the suggestion of combining traditional carburizing and quenching processes with Q-P-T processes was proposed for heat treatment of walking wheel to improve its strength and toughness.

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Fracture cause analysis of one tower bolt

Zhang Demei, Liang Xiaodong, Zhang Yan

Heat Treatment of Metals 2025, 50 (2): 312-315. doi:10.13251/j.issn.0254-6051.2025.02.050

Abstract （27）

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One tower bolt used in one wind-power station was fractured. The fracture cause of the failed bolt was analyzed by means of metallographic examination, SEM-EDS analysis, chemical composition testing and mechanical property testing. The results show that chemical composition and mechanical properties all meet the requirements of national standard. There is no abnormality for the microstructure. But the R value at the connection between the head of the fractured bolt and the screw is too small. The depth of Zn-Ni plating near the crack source is deeper than other edges, which indicates that during quenching and tempering treatment, cracks are generated at the intersection of the bolt head and the screw under the action of quenching stress. When in use, under the action of force, cracks continue to propagate, ultimately leading to fatigue fracture.

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