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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 （26）

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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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