Select

Microstructure and mechanical properties of ultrafine grained heterostructured dual-phase steel prepared by warm rolling and intercritical annealing

Yan Wenchao, Gao Bo, Xiao Lirong, Zhou Hao

Heat Treatment of Metals 2024, 49 (7): 54-62. doi:10.13251/j.issn.0254-6051.2024.07.009

Abstract （136）

PDF （5806KB）（56）

Comprehensive mechanical properties of the low-carbon steel were greatly improved by producing the ultra-fine grained heterostructured dual-phase (UFG-HSDP) structure. First, the initial structure of the low carbon dual-phase structure is refined by warm rolling at 300 ℃, and then the ultra-fine grained heterostructured dual-phase steel with high martensite content (volume fraction of77%) is obtained by intercritical annealing at 740 ℃. The average grain size of ferrite and martensite is 0.78 and 0.39 μm, respectively. The UFG-HSDP steel shows excellent comprehensive mechanical properties, with yield and tensile strengths of 1.26 and 1.75 GPa, respectively, while maintaining a uniform elongation of 6.2%. The mechanical incompatibility between ferrite and martensite in the UFG-HSDP steel during tensile deformation results in significant hetero-deformation induced hardening, which enhances the total strain hardening rate and thus improves the strength-ductility match of low-carbon steel.

Reference | Related Articles | Metrics

Select

Variant selection of α phase in β-type Ti-15Mo alloy

Ren Cheng, Min Xiaohua, Fei Qi

Heat Treatment of Metals 2024, 49 (9): 1-10. doi:10.13251/j.issn.0254-6051.2024.09.001

Abstract （128）

PDF （5708KB）（132）

SEM and EBSD were used to investigate the variant selection behaviour of the α phase in the β matrix and at the β grain boundaries in the Ti-15Mo alloy after solution treatment and aging. The results show that the solution treated specimen consists of single β grains without any preferred orientation. In the solution treated and aged specimen, the intragranular α phase does not undergo variant selection, instead, self-accommodation occurs among α variants, leading to a cross distribution of α phase variants at 60°. The variant selection of the film-like grain boundary α phase is influenced by the misorientation of adjacent β grains. A minor misorientation causes α phase to retain a Burgers orientation relationship with β grains on either side, whereas a major misorientation affects the precipitation of the α phase due to the interface orientation. The variant selection of the grain boundary Widmanstätten microstructure relies on the nucleation site. When the nucleation takes place at the film-like grain boundary α phase, it selects the same variants as the film-like grain boundary α phase. Nonetheless, when the nucleation occurs at the interface between the film-like grain boundary α phase and the β matrix, it is influenced by both.

Reference | Related Articles | Metrics

Select

Isothermal phase transformation behavior and cooperative regulation of microstructure and properties and flat coil of hot rolling 65Mn steel strip

Tian Yaqiang, Yao Zhiqiang, Nian Baoguo, Zhang Junfen, Zhang Xiaolei, Song Jinying, Zhang Mingshan, Chen Liansheng

Heat Treatment of Metals 2024, 49 (9): 24-30. doi:10.13251/j.issn.0254-6051.2024.09.004

Abstract （94）

PDF （5095KB）（51）

Isothermal transformation curve (TTT curve) of 65Mn steel was obtained by quenching phase change machine. Based on this curve, the evolution of microstructure and mechanical properties at different coiling temperatures was studied, and the possible causes and control methods of flat coil were discussed. The results show that the typical microstructure of the 65Mn steel, namely proeutectoid ferrite and pearlite, is obtained between 600-750 ℃. The TTT curve presents a typical "C" shape, with a "nose tip" temperature of 550 ℃. The incubation period is relatively short at this temperature, only 0.25 s. Within the typical microstructure formation temperature range of the 65Mn steel, the incubation period gradually increases with the increase of temperature, and the content of proeutectoid proeutectoid ferrite increases, while the content of pearlite decreases. According to the actual production, the selected coiling temperature of the 65Mn steel is between 650-750 ℃, and the microstructure is proeutectoid ferrite and pearlite. With the coiling temperature decreases from 750 ℃ to 650 ℃, the proeutectoid ferrite content decreases from 19.4% to 4.1%, and the distribution gradually transitions from block distribution to network distribution. The pearlite lamellar spacing decreases from 277.0 nm to 178.0 nm, resulting in an increase in the yield strength of the 65Mn steel from 534 MPa to 637 MPa, an increase in ultimate tensile strength from 776 MPa to 899 MPa, an increase in hardness from 18.8 HRC to 24.3 HRC, and a decrease in percentage total extension at fracture from 28.9% to 19.4%. In actual production, the coiling temperature and the holding time before coil discharging are adjusted based on TTT curve and the evolution of microstructure and mechanical properties under different coiling temperatures can achieve synergistic regulation of microstructure, mechanical properties and flat coil defects.

Reference | Related Articles | Metrics

Select

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）

PDF （3505KB）（73）

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.

Reference | Related Articles | Metrics

Select

Microstructure and properties of high hardenability high-carbon chromium bearing steel

Wang Bingnan, Jia Yuxin, Wang Shanshan, Zhang Yahui

Heat Treatment of Metals 2024, 49 (9): 31-35. doi:10.13251/j.issn.0254-6051.2024.09.005

Abstract （86）

PDF （2423KB）（50）

Martempering and austempering treatments were conducted on three types of high-hardenability high-carbon chromium bearing steels, namely GCr18MnMo steel, GCr18MnMo1 steel and GCr19SiMnMo1 steel. The differences in their microstructure, maximum hardenability size, retained austenite and impact properties were compared. The results show that the hardenability is ranked from high to low as GCr19SiMnMo1 steel > GCr18MnMo1 steel > GCr18MnMo steel. If the hardenability standard is that the core hardness is greater than or equal to 55 HRC, the maximum hardenability size of GCr18MnMo steel is approximately 70 mm, the maximum hardenability size of GCr18MnMo1 steel is approximately 100 mm, and the maximum hardenability size of GCr19SiMnMo1 steel is approximately 130 mm. When these three tested steels undergo austempering, the retained austenite content can be guaranteed to be less than 1%. During martempering, the retained austenite content of GCr18MnMo and GCr18MnMo1 steels is less than 15%, and for GCr19SiMnMo1 steel, the retained austenite content can be reduced to less than 1% by additional tempering while ensuring high hardness. The impact properties of these three specimen steels are very close, and the impact property after austempering is approximately 70% higher than that after martempering. Only GCr19SiMnMo1 steel can be used for parts with wall thickness or diameter more than ϕ100 mm to ensure that the core troostite meets the requirements.

Reference | Related Articles | Metrics

Select

Effect of banded structure on mechanical properties of cold-rolled dual phase steel DP780

Xue Renjie, Dong Yikang, Ma Ziyang, Cao Xiao'en, Li Zhi'ang

Heat Treatment of Metals 2024, 49 (12): 191-197. doi:10.13251/j.issn.0254-6051.2024.12.032

Abstract （81）

PDF （7623KB）（24）

In order to study the segregation behavior of elements in the banded structure of cold-rolled duplex steel DP780 and its effect on mechanical properties, OM, SEM, EMPA, EBSD and other methods were used to characterize and analyze the morphology and element distribution characteristics of the banded structure, tensile properties and microstructure change during the tensile process, fracture mechanism, and so on. The research results show that the macroscopic segregation formed by redistribution of C, Mn, Al and Si solute elements during the solidification process leads to the formation of banded structure, which is mostly distributed parallel to the rolling direction at 1/2 and 1/4 of the plate thickness, the grain size distribution is obviously nonuniform, and the small angle grain boundary density of the banded structure is significantly higher than that of the equiaxed structure. Meanwhile, the properties and microstructure change in tensile process indicate that after 10% tensile pre-deformation, the fibrosis is more obvious in the banded structure specimen, increasing the resistance of dislocation movement during the deformation process and improving the strength. The banded structure can also cause dislocation pile-up and lattice distortion, deteriorating the ability to deform. The banded structure reduces the coordinated deformation ability of the matrix structure, resulting in prominent anisotropy. Further, the observation of fracture morphology shows that the initial crack initiation occurs at the M/F phase interface, and a tear ridge is formed at the M/F interface during fracture, while the location and size of the tear ridge are consistent with that of the banded structure. There is a martensite band region with poor plastic deformation ability between the tear ridges, and the ferrite side of the M/F interface has significant plastic deformation; the specimen with equiaxed structure exhibits uniform axial deformation and better fracture plasticity.

Reference | Related Articles | Metrics

Select

Effect of heat treatment process on microstructure and precipitates of Q890 high strength steel

An Tao, Guo Chengyu, Li Tianyi, Zhang Chi, Dai Chunduo, Zhang Zhe

Heat Treatment of Metals 2024, 49 (11): 46-52. doi:10.13251/j.issn.0254-6051.2024.11.007

Abstract （79）

PDF （5742KB）（37）

Microstructure and precipitated phases of heat treated Q890 high strength steel were studied by using thermodynamic calculations and experimental equipment such as scanning electron microscope and transmission electron microscope. The results indicate that the microstructure of the quenched tested steel is lath martensite, a small amount of bainite, (Nb,Ti)C and Cu-rich nanoscale precipitated phase, the average size of precipitated phase is 42.09 nm, the volume fraction is 0.66%, and the precipitation strengthening component is 89.21 MPa. After low-temperature tempering at 200 ℃, the microstructure of the tested steel shows a little change, the precipitated phases grow slightly, and the precipitation strengthening component decreases. After high-temperature tempering at 600 ℃, the microstructure of the tested steel is tempered sorbite, a small amount of bainite and a large amount of Fe-rich M₂₃C₆ precipitate phases. The precipitated phase particle size significantly increases, with average size of 52.29 nm and volume fraction of 8.55%. The precipitation strengthening component is significantly increased to 271.08 MPa.

Reference | Related Articles | Metrics

Select

Effect of solution treatment on microstructure evolution and mechanical properties of aluminum alloy aluminum clad thin plate

Wang Jingtao, Sun Ning, Yu Lang, Wang Yonghong, Yu Jihai, Huang Tongjian, Zhang Ruiyuan

Heat Treatment of Metals 2024, 49 (11): 60-68. doi:10.13251/j.issn.0254-6051.2024.11.009

Abstract （63）

PDF （8222KB）（29）

Evolution of microstructure and properties of 2××× series aluminum alloy aluminum clad thin plate during solution treatment were studied by means of metallographic microscope, scanning electron microscope, energy dispersive spectroscopy, differential scanning calorimetry and room temperature tensile test. The results indicate that after solution treatment, there are still large-sized AlCuFeMn and Al₂CuMg phases in substrate of the cold-rolled aluminum clad thin plate. However, with the increase of solution treatment temperature and the extension of holding time, the content of retained second phases in the substrate gradually decreases. The diffusion degree of Mg and Cu elements is relatively high in the aluminum coating and the transition zone, but there is no failure problem of the aluminum coating caused by severe element diffusion. When the solution treatment process is 500 ℃×20 min, the retained second phase content in the alloy is the lowest of 1.101%. After natural aging for 96 h, the yield strength of the aluminum clad thin plate is 286.5 MPa, the tensile strength is 458.0 MPa, and the elongation after fracture is 23.1%, good combination of strength and plasticity is obtained.

Reference | Related Articles | Metrics

Select

Effect of deformation heat treatment on microstructure and properties of Ti₄₅Zr₂₀Nb₁₅V_(10-x)Al₁₀Mo_x refractory high entropy alloy

Li Zhenglong, Pang Jingyu, Tang Guangquan, Cheng Lufan, Zhang Caiwei, Hou Xingyu, Li Wen, Zhang Haifeng

Heat Treatment of Metals 2024, 49 (7): 47-53. doi:10.13251/j.issn.0254-6051.2024.07.008

Abstract （62）

PDF （5038KB）（106）

Ti₄₅Zr₂₀Nb₁₅V_(10-x)Al₁₀Mo_x (x=0, 0.5, 1.0) refractory high entropy alloy was prepared by adding trace amounts of Mo element to the Ti₄₅Zr₂₀Nb₁₅V₁₀Al₁₀ refractory high entropy alloy matrix, which strain hardening ability and plasticity were improved by deformation heat treatment. Microstructure and mechanical properties of the as-cast specimen and cold-rolled (deformation of 80%) and annealed (600 ℃×5 h and 800 ℃ for 1 h) specimen were investigated using X-ray diffractometer, field emission scanning electron microscope, and universal mechanical testing machine. The test results show that the as-cast alloy has a single-phase BCC structure, and the addition of Mo element increases the yield strength and maintains a fracture elongation of about 10%. After cold rolling and annealing, the microstructure of the alloy becomes BCC+Al₃Zr₄ dual phase with a large amount of approximately spherical nanoscale Al₃Zr₄ particles precipitated at and near grain boundaries, causing the alloy to transition from strain softening to strain hardening, and the yield strength of the alloy is maintained at 1100 MPa, while the fracture elongation is significantly improved. When the Mo content is 0.5%, the fracture elongation of the alloy after cold rolling annealing increases from 9.9% in as-cast state to 16.9%, exhibiting excellent strength plasticity matching and a density of only 5.638 g/cm³.

Reference | Related Articles | Metrics

Select

Microstructure and mechanical properties of typical hot formed parts

Shi Baoliang, Jiang Fatong, Liu Xuliang, Song Wenbin, Jin Yuming, Qiao Meng, Guo Qiuyan

Heat Treatment of Metals 2024, 49 (6): 135-141. doi:10.13251/j.issn.0254-6051.2024.06.023

Abstract （59）

PDF （5953KB）（47）

Microstructure and mechanical properties of different hot formed parts based on a body-in-white were systematically studied. The results show that the microstructure of the typical hot formed parts is mainly lath martensite, and some parts have residual austenite structure in local areas. The microstructure of the soft zone in the mold is mainly composed of ferrite, martensite and a small amount of bainite, where the martensite has no obvious lath characteristics and relatively low proportion. The decarburization layer thickness of the left front/rear door collision beam is distributed between 38.55-45.57 μm. The average force value of the three-point bending of the left front door anti-collision beam is 6962 N, and the maximum force value is 9709 N; while the average force value of the left rear door anti-collision beam is 8740 N, and the maximum force value is 11 392 N. The surface of the parts is in good condition and there are no cracks generate after three-point bending. The performance of the anti-collision beams meets the requirements of vehicle safety collision testing. For the typical hot formed parts, the average hardness distribution is 456-507 HV10, the yield strength is greater than 1000 MPa, the tensile strength is greater than 1400 MPa, and the elongation is ≥5.5%. While in the soft zone, the hardness distribution is between 225-243 HV10, the yield strength is greater than 470 MPa, the tensile strength is greater than 650 MPa, and the elongation is ≥17%. The performance of the parts meets the standard requirements.

Reference | Related Articles | Metrics

Select

Microstructure, properties and microalloyed phase precipitation behavior of high-conductivity high-strength steel

Tang Xingchang, Zhou Weilian, Qi Dayang, Jia Zhihui, Zhang Zhijian, Cheng Ganghu, Hou Yuanyuan

Heat Treatment of Metals 2024, 49 (6): 150-158. doi:10.13251/j.issn.0254-6051.2024.06.025

Abstract （59）

PDF （5937KB）（29）

In order to study the deformation-induced precipitation behavior and property changes of the second phase particles in high-conductivity high-strength steel, the stress relaxation experiment was carried out by using the Gleeble-3500 thermal simulation testing machine, and then the microstructure and properties of the tested steel were observed and analyzed by means of metallurgical microscope, inductively coupled plasma spectrometer (ICP), Vickers hardness tester, and four-probe resistivity meter. The test results show that the relaxation process can be divided into three stages according to the slope of the stress relaxation curve, the first stage is recrystallization, the second stage is deformation-induced precipitation, and the third stage is inhibited by recrystallization and precipitation grows. The PTT curve obtained from the stress relaxation curves is "S" type, and the nose tip temperature is 950 ℃. At higher deformation temperatures, the precipitated phase precipitates rapidly, and the dislocation is nailed, and the grain size decrease. The overall hardness of the tested steel is low and fluctuates greatly, and the overall change trend is irregular, and the hardness is the highest when deformed at 850 ℃. The resistivity decreases first and then increases with the increase of deformation temperature, and the resistivity is the lowest when deformed at 800 ℃.

Reference | Related Articles | Metrics

Select

Forming limit properties and microstructure analysis of high strength dual phase steel DP980

Xue Feng, Geng Zhiyu, Liu Xuming, Bi Lian, Zhou Tianpeng

Heat Treatment of Metals 2024, 49 (6): 164-168. doi:10.13251/j.issn.0254-6051.2024.06.027

Abstract （59）

PDF （2790KB）（35）

The forming limit of high strength dual phase steel DP980 specimens with 1.4 mm thichness and different widths was tested. The strain degree of forming limit fracture and necking were studied, and the effect factors of microstructure on necking and cracking were analyzed. The microstructure and properties of the steel were analyzed by means of scanning electron microscope, electron backscatter diffraction, transmission electron microscope and tensile machine. The results show that there are multiple stress limit points in the forming limit test of the steel, where the FLD₀ value at the necking location is 0.14, while that for the rupture forming limit is 0.20. The tensile fracture results show that the Nb and Ti precipitates existing in the high strength dual phase steel DP980 make the fracture characteristics after necking change from mixed fracture to ductile. The TEM results show that the lath martensite hinders the dislocation movement in the steel DP980, and greatly increases the strength of the steel. The KAM results show that the massive dislocations pile up in the ferrite grains after necking leads to the formation of dislocation walls, which makes the material produce stronger work hardening.

Reference | Related Articles | Metrics

Select

Effect of rare earth addition on microstructure and properties of Al-Mg-Si alloy

Chen Baoan, Li Menglin, Chen Rui, Duo Junlong, Han Yu, Zhu Zhixiang, Yang Changlong, Miao Yaojun

Heat Treatment of Metals 2024, 49 (7): 100-105. doi:10.13251/j.issn.0254-6051.2024.07.015

Abstract （59）

PDF （3563KB）（41）

Single wires of Al-Mg-Si alloys with rare earth addition (Ce or Sc) and without rare earth(RE) addition were prepared by hot rolling and cold drawing, and aged at 175 ℃ for different time. Microstructure of the alloy wires was observed by SEM and TEM, while the tensile strength and elongation were obtained by tensile test with electrical universal testing machine, and the resistance was also tested on digital micro-ohmmeter. The results show that the morphologies and size characteristics of micro-scale AlFeSi particles are improved owing to the RE addition. During the aging process, Ce has no obvious effect on the characteristics of nanoscale precipitates, while Sc can inhibit the precipitation and growth process of nanoscale precipitates. Therefore, the β″ phase in Sc-containing alloys possesses minimum size and well-dispersed distribution. After aging at 175 ℃ for 4 h, considerably well-performed comprehensive properties are obtained for all the 3 alloys, among which the Ce-added alloy has the highest electric conductivity (about 56.2%IACS), while the Sc-added alloy exhibits the highest tensile strength (about 350 MPa).

Reference | Related Articles | Metrics

Select

Effect of continuous annealing on microstructure and properties of 350 MPa cold-rolled high corrosion resistant weathering steel

Wang Nai, Ma Degang, Li Jianying, Ma Guangzong, Sun Lu, Sun Hongliang, Ji Minglong

Heat Treatment of Metals 2024, 49 (9): 18-23. doi:10.13251/j.issn.0254-6051.2024.09.003

Abstract （58）

PDF （3537KB）（53）

Effect of continuous annealing process on microstructure and properties of 350 MPa cold-rolled high corrosion resistant weathering steel was studied by simulating continuous annealing process with Gleeble-3500 annealing machine. The results show that with the increase of annealing temperature, the strength of the tested steel decreases first and then increases, the annealing temperature is the key factor affecting the microstructure and properties of the tested steel, whereas, the effect of strip speed, slow cooling temperature and rapid cooling temperature on properties of the tested steel is limited. When the annealing temperature is lower than 800 ℃, only recovery and recrystallization in the tested steel occur, and the microstructure is composed of ferrite and carbide, the strength of the tested steel decreases with the increase of annealing temperature. When the annealing temperature is 800 ℃, the yield ratio reaches a minimum value of 0.53, exhibiting the characteristics of duplex steel, and is annealed at the critical austenitizing temperature Ac₁. When the annealing temperature is higher than 800 ℃, the tested steel occurs recovery, recrystallization and austenitization transformation, and the microstructure is composed of ferrite, bainite and carbide after cooling, and the strength of the tested steel increases with the increase of annealing temperature. Based on the comprehensive analysis, two process routes, low-temperature annealing and high-temperature annealing, can be used in industrial production to obtain the tested steel that meet the standard requirements.

Reference | Related Articles | Metrics

Select

Effect of annealing on microstructure and mechanical properties of TC4 titanium alloy aeroengine blades

Wang Qingjuan, Du Xudong, Jiang Li, Li Zhiyi, Liu Dan, Wang Wei

Heat Treatment of Metals 2024, 49 (10): 126-132. doi:10.13251/j.issn.0254-6051.2024.10.022

Abstract （58）

PDF （7757KB）（22）

TC4 alloy third-stage rotor blade for aeroengine was annealed at different temperatures (600-950 ℃) with different cooling methods (air cooling and water cooling). The microstructure was analyzed by OM, SEM and EBSD. The microhardness and mechanical properties at room temperature were tested by Vickers hardness tester and tensile testing machine. The effect of annealing treatment on the microstructure and mechanical properties of the TC4 titanium alloy blades was studied. The results show that the volume fraction of α phase changes little with the increase of annealing temperature below 850 ℃, and the grain size of α phase is about 12 μm. When the annealing temperature exceeds 850 ℃, the acicular α phase appears in the microstructure. When the annealing temperature is below 900 ℃, the hardness of the air-cooled specimen is 5-10 HV0.2 higher than that of the water-cooled specimen. When the annealing temperature exceeds 850 ℃, the content of acicular α phase increases and the microhardness rapidly increases. The maximum strength appears at the annealing temperature of 600 ℃, but with relatively low elongation. Under air cooling conditions, at annealing temperature of 800 ℃, the tensile strength reaches 1033.7 MPa, the elongation is 23.2%, and the comprehensive mechanical properties of the blade are optimal.

Reference | Related Articles | Metrics

Select

Effect of long-term aging on microstructure and properties of 21-4NWNb steel

Zhao Shouzhong, Wang Shouqian, Zhu Zhiyuan, Min Liang, Xu Chaofan, Shen Jiabao

Heat Treatment of Metals 2024, 49 (7): 78-83. doi:10.13251/j.issn.0254-6051.2024.07.012

Abstract （58）

PDF （6041KB）（56）

Microstructure evolution and mechanical properties change of the 21-4NWNb steel after standard heat treatment (1050 ℃×30 min+750 ℃×4 h) during long-term aging at 750 ℃ were studied. The results show that the grain size of 21-4NWNb steel does not change obvious during long-term aging. When aged for 200 h, a small amount of regular block M₂₃C₆ carbides are distributed in the steel. When the aging time extends to 500 h, σ phase (AB) gradually appears in the grain. The hardness of the 21-4NWNb steel reaches the highest value of 324 HV when aged for 200 h with a maximum tensile strength of 971 MPa and a elongation of 22.2%. With the prolong of aging time from 200 h, the hardness and tensile strength show a gradual decline, and the elongation of the steel drops below 15% after aging for 2000 h.

Reference | Related Articles | Metrics

Select

Effect of cold rolling reduction rate on texture and formability of IF steel after annealing treatment

Ma Yi, Zhang Liwen, Song Kangjie, Luo Yalong, Miao Luyang, Zhang Chi, Wu Xin, Wang Yinzhou

Heat Treatment of Metals 2024, 49 (10): 121-125. doi:10.13251/j.issn.0254-6051.2024.10.021

Abstract （57）

PDF （4202KB）（22）

The texture and formability of IF steel with different cold rolling reduction rates after annealing at 800 ℃ for 300 s were studied. The microstructure and texture of annealed specimens at different cold rolling reduction rates were measured by metallographic microscopy and electron backscatter diffraction (EBSD). The tensile tests of the IF steel specimens were carried out by means of universal tensile testing machine. The experimental results show that the recrystallization grain size decreases gradually with the increase of cold rolling reduction rate. The texture uniformity along the gamma-orientation line increases first and then decreases with the increase of cold rolling reduction rate. When the reduction rate is 75%, the uniform shape of the texture is optimal. By comparing the plastic strain ratio (r value) and anisotropy Δr of the different IF steel specimens, it can be seen that IF steel has the largest r value and the smallest anisotropy Δr when the cold rolling reduction rate is 75%. Therefore, it has excellent formability.

Reference | Related Articles | Metrics

Select

Microstructure and tensile properties of different hardness regions in as-served P92 steel pipe

Li Yong, Ma Jialin, Wang Wanli, Fang Yiming, Zhan Xianqiang, Liu Junjian, Tang Wenming

Heat Treatment of Metals 2024, 49 (10): 140-147. doi:10.13251/j.issn.0254-6051.2024.10.024

Abstract （56）

PDF （4965KB）（34）

Remarkable hardness difference was found in the cross-sectional regions of low outside surface hardness in P92 main steam pipe after serving for 70 000 h. Microscopic and phase analysis, and room-/high-temperature tensile property tests were executed to confirm the microstructure characteristics and mechanical properties of the specimens in different hardness regions. The results show that for the low hardness specimens, widening and decomposing of martensite lathes is severe, lath martensite is gradually transferred to tempered martensite. The M₂₃C₆ and Laves-phase particles precipitated along the prior austenite grain boundaries and martensite lathes are further coarsened and distributed in semi-continuous chains. Meanwhile, the precipitated phase particles dispersively distributed in the martensite and (or) ferrite matrices are also expanded. The room and high temperature tensile strengths of the low hardness specimens are low too, especially, room and high temperature yield strengths of them are lower than the indexes required by the relevant national standards, which could be used for the key mechanical property index in aging state assessment of the as-served P92 main-steam pipe.

Reference | Related Articles | Metrics

Select

Behavior of microstructure evolution during wear and damage of pearlitic rail steel

Gao Chao, Jiang Hongli, Wang Xu, Wang Dongmei, Cen Yaodong, Chen Lin

Heat Treatment of Metals 2024, 49 (11): 38-45. doi:10.13251/j.issn.0254-6051.2024.11.006

Abstract （55）

PDF （6864KB）（23）

Friction and wear performance of 75 kg/m pearlitic heavy-duty heat-treated rail steel was investigated by means of the ring-block butt-abrasion test at different test forces and cycle times, and compared with that of rail steel with RE, Nb and Ni elements adding. At the same time, the surface morphology, profile damage, microstructure evolution in the plastic deformation zone and elemental content changes of the specimens after wear were analyzed by using a combination of scanning electron microscope, transmission electron microscope and electron microprobe techniques. The results show that with the increase of test force, the wear loss increases, the wear form transitions from oxidizing wear to adhesive wear and fatigue wear, and the thickness of the white layer in the deformation zone increases. With the increase of friction wear cycle times, the grain size of the deformation zone is finer, and the thickness of the plastic deformation layer becomes larger. However, under the larger test force, the crack extension in the white layer intersects and causes the material to break, and the wear loss increases. The pearlitic lamellar spacing of the rail steel with adding RE, Nb and Ni elements is refined by 21.8% compared with that of the original state rail steel, and the smaller the pearlite lamellar spacing is, the smaller the thickness of the white layer is formed and is less prone to breaking, and thus it has better wear resistance.

Reference | Related Articles | Metrics

Select

Microstructure and strengthening mechanism of 2100 MPa grade ultra-high strength spring steel

Lu Wei, Tu Tianquan, Deng Xiaoyun, Luo Suhui, Xing Xianqiang, Luo Zhichao

Heat Treatment of Metals 2024, 49 (6): 142-149. doi:10.13251/j.issn.0254-6051.2024.06.024

Abstract （55）

PDF （6711KB）（39）

Three ultra-high strength steels (1900, 2000 and 2100 MPa) were prepared by optimizing the alloy compositions and quenching and tempering processes. Their microstructure, mechanical properties and strengthening mechanisms were comparatively investigated. The results show that the prior austenite grain size decreases from 28.8 μm to 16.0 μm with the increase of C and V content in the steel. The tensile strength of 2100 MPa grade steel actually reaches 2130 MPa, and the percentage reduction of area is 42%. Further research shows that, the retained austenite in the 2100 MPa grade steel is up to 16.2% in volume fraction, and contributes a transformation-induced plasticity (TRIP) effect during tensile deformation, which significantly improves the work-hardening ability and uniform elongation of the steel. The strength of the 2100 MPa grade spring steel wire mainly comes from solution strengthening, dislocation strengthening and precipitation strengthening, and their contribution values are 391, 808 and 469 MPa, respectively. The fine prior austenite grain size and the TRIP effect from the retained austenite are the key to the excellent strength and ductility of the 2100 MPa grade ultra-high strength spring steel.

Reference | Related Articles | Metrics

Content of MICROSTRUCTURE AND PROPERTIES in our journal