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  Effect of subcritical heat treatment on microstructure and properties of high chromium cast irons Yuan Zhizhong, Liu Haiming, Ju Yulin, Chen Lu, Niu Zongran, Wang Zhiyuan, Cao Fuyang, Cheng Xiaonong Heat Treatment of Metals    2024, 49 (10): 1-7.   doi:10.13251/j.issn.0254-6051.2024.10.001 Abstract （244）      PDF （4765KB）（173）       Knowledge map    Aiming at the problem of high energy consumption in conventional quenching and tempering process of high chromium cast irons, the subcritical heat treatment tests of three kinds of high chromium cast irons were carried out. Moreover, the effect of the process on the microstructure, hardness and surface wear resistance was studied. The results show that the microstructure of high chromium cast irons is primarily composed of retained austenite, M7C3 carbide, (Fe, Cr)23C6 carbide, Mo2C carbide and pearlite when subjected to holding temperatures ranging from 500 ℃ to 650 ℃ for 1 h to 14 h. A peak value in hardness is observed for the three high chromium cast irons when holding at 550 ℃ to 600 ℃ for 6 h to 12 h, with the highest peak hardness being 57.4 HRC. The hardness is most significantly influenced by the Mo element. During the insulation process, the pearlite phase transformation of austenite is promoted by the precipitation of secondary carbides in high chromium cast irons. The effects of pearlite transformation strengthening and precipitation strengthening of secondary carbides gradually decrease with prolonged holding time. The eutectic high chromium cast iron with the highest carbon content exhibits the best wear resistance when holding at 600 ℃ for 8 h. It can be seen that the first step to improve the wear resistance of high chromium cast irons is to increase the amount of eutectic carbides, and then to add elements such as Mo to enhance the precipitation strengthening effect. Reference | Related Articles | Metrics

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  Effect of austenitization temperature on microstructure and mechanical properties of 40CrMnSi2Mo steel under air cooling Yu Linran, Liu Geng, Yang Zhuoyue, Su Jie, Ning Jing, Ding Yali Heat Treatment of Metals    2024, 49 (12): 1-8.   doi:10.13251/j.issn.0254-6051.2024.12.001 Abstract （179）      PDF （5846KB）（158）       Knowledge map    Effect of austenitization temperature (875-975 ℃) on the microstructure and mechanical properties of the novel Cr-Mn-Si series high strength medium carbon low alloy 40CrMnSi2Mo steel under air cooling condition was studied by means of optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and laser scanning confocal microscope (LSCM). The results show that when austenitized at 875 ℃ and 900 ℃, the microstructure is dominated by martensite with a small amount of the undissolved precipitates (NbC). The prior austenite grains are fine and stable. The tensile strength is 1997 MPa and 2003 MPa, the elongation is 11.0% and 12.0%, and the fracture toughness is 70.3 MPa·m1/2 and 73.6 MPa·m1/2, respectively. When austenitized at 975 ℃, the solubility of NbC increases and the pinning effect decreases. The growth of austenite grain size decreases the thermal stability so that the coarse bainite/martensite multiphase is obtained under air cooling. The tensile strength is 1980 MPa, the elongation is 10.5%, and the fracture toughness is only 77.6 MPa·m1/2. The effect of the austenite grain refinement on the strength and toughness of the 40CrMnSi2Mo steel is not obvious. The fine bainite/martensite multiphase can be obtained after austenitizing at 950 ℃. The mechanical properties achieve an excellent combination, with the tensile strength of 2040 MPa, the elongation of 12% and the fracture toughness of 86.6 MPa·m1/2. Reference | Related Articles | Metrics

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  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）       Knowledge map    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

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  Effect of Zn/Mg ratio on microstructure, mechanical properties and corrosion resistance of 7075 aluminum alloy He Zongzheng, Wu Mingdong, Yuan Shuo, Yao Shuwei, Xiao Daihong, Huang Lanping, Liu Wensheng Heat Treatment of Metals    2024, 49 (5): 1-9.   doi:10.13251/j.issn.0254-6051.2024.05.001 Abstract （185）      PDF （9223KB）（127）       Knowledge map    Effect of Zn/Mg ratio (mass fraction) on microstructure, mechanical properties, and corrosion resistance of 7075 aluminum alloys was investigated by means of optical microscope, scanning electron microscope, transmission electron microscope, tensile test, microhardness test and corrosion test. The results show that with the increase of Zn/Mg ratio from 1.76 to 2.90, the grain size of the as-cast alloy increases, the T6 age-hardening rate of the alloy is accelerated, and the time to reach peak hardness is shortened. The increase in Zn/Mg ratio results in a decrease in the recrystallization rate of the T6 peak-aged alloy and an increase in the percentage of the low-angle grain boundaries. The tensile strength of the alloy under the T6 peak-aging treatment with the Zn/Mg ratio of 2.10 is 634 MPa, the yield strength of the alloy is 588 MPa, and elongation is 8.4%. The tensile strength of the T74 aged alloy is 613 MPa, yield strength is 542 MPa, and elongation is 8.9%, and alloys with Zn/Mg ratio of 2.10 in both aging states exhibit good strength while maintaining high elongation. The corrosion resistance of the aged alloy decreases as the Zn/Mg ratio increases from 1.76 to 2.90. The corrosion resistance of the alloy after T74 aging treatment is better than that of the alloy under the T6 peak-aging state. Reference | Related Articles | Metrics

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  Numerical simulation of vacuum isothermal quenching process of H11 steel large module for die-casting dies Tu Yujie, Li Bingchen, Chen Hao, Wu Xiaochun Heat Treatment of Metals    2024, 49 (7): 1-8.   doi:10.13251/j.issn.0254-6051.2024.07.001 Abstract （102）      PDF （5794KB）（126）       Knowledge map    Based on the metal-thermo-mechanical coupled theory, multi-field coupled numerical models of the H11 steel large module (500 mm×500 mm×500 mm) during vacuum isothermal quenching was established, and the numerical simulation of different vacuum isothermal quenching processes was carried out to study the evolution of the temperature field, structure field and stress field. The results show that compared with direct quenching, isothermal quenching can effectively reduce the temperature difference and the stress between the core and surface during the cooling process of the module to avoid the risk of distortion and cracking. Vacuum isothermal quenching can increase the volume fraction of bainite in the core of the module while avoiding pearlite formation and carbides precipitating along the grain boundary, and with the increase of the isothermal time, the more core bainite will be generated. The experimental verification of vacuum isothermal quenching at 500 ℃ for 1 h carried out by using industrial equipment indicates that the temperature curves at different positions of the module are in good agreement with the simulation results, and the type of bainite formed in the core of the module after vacuum isothermal quenching is lower bainite with good toughness. Reference | Related Articles | Metrics

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  Microstructure, properties and dynamic recrystallization behavior of 20Mn23AlV non-magnetic structural steel hot rolled plate Luo Xiaoyang, Cheng Ganghu, Jin Ke, Zhou Weilian, Hou Yuanyuan, Tang Xingchang Heat Treatment of Metals    2024, 49 (7): 91-99.   doi:10.13251/j.issn.0254-6051.2024.07.014 Abstract （35）      PDF （4985KB）（108）       Knowledge map    Experimental study on the density, microstructure, and mechanical properties of 20Mn23AlV non-magnetic structural steel hot-rolled plate was conducted. Additionally, multi-pass thermal simulation tests were performed to investigate the changes in microstructure and magnetic properties before and after the tests. The results show that, due to the addition of the Al element, the density of the tested steel is reduced by approximately 0.192 g/cm3 compared to that of common steels. The average tensile strength of the hot-rolled plate of non-magnetic steel is 721 MPa, the yield strength is 371 MPa, and the elongation after fracture is 69.5%, indicating good strength-ductility matching. It is found that through multi-pass thermal simulation experiments with 60% hot compression deformation, the tested steel undergoes dynamic recrystallization behavior at 950 ℃, with the average austenite grain size decreasing from 10.24 μm to 6.08 μm. There is no phase transformation before and after the multi-pass thermal simulation tests, and the relative permeability measured is 1.001 and 1.002, respectively, which meets the requirements for the magnetic properties of non-magnetic steel. Reference | Related Articles | Metrics

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  Effect of deformation heat treatment on microstructure and properties of Ti45Zr20Nb15V(10-x)Al10Mox 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）       Knowledge map    Ti45Zr20Nb15V(10-x)Al10Mox (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

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  Effect of composite addition of trace amounts of Mn, Zn and Ti on microstructure and mechanical properties of Al-Cu-Li-Mg-Ag-Zr alloy Xu Qing, Yin Dengfeng, Wang Hua, Xie Kaiwen, Song Zhuanzhuan Heat Treatment of Metals    2024, 49 (11): 1-9.   doi:10.13251/j.issn.0254-6051.2024.11.001 Abstract （134）      PDF （5872KB）（101）       Knowledge map    Effect of composite addition of trace amounts of Mn, Zn and Ti on the microstructure and mechanical properties of Al-Cu-Li-Mg-Ag-Zr alloy was studied by using tensile testing machine, metallographic microscope, scanning electron microscope and transmission electron microscope. The results show that the composite addition of trace amounts of Mn, Zn and Ti elements can significantly refine the grain structure of the as-cast alloy, and at the same time, the insoluble second phase Al(CuMnFe) in the solution treated alloy is also refined. The composite addition of trace amounts of Mn, Zn and Ti elements can effectively promote the precipitation of the main strengthening phase T1 in the T6 and T8 peak aged Al-Cu-Li-Mg-Ag-Zr alloy, improving the mechanical properties of the alloy. Compared with the T6 peak aged, the amount of T1 phase precipitated in the T8 peak aged Al-Cu-Li-Mg-Ag-Zr alloy significantly increases, the size significantly decreases, the distribution is more uniform and dispersed, and the strength and plasticity are significantly improved. Reference | Related Articles | Metrics

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  Simulation and calculation of heat treatment parameters and thermophysical properties of 16CrSiNi steel using JMatPro software Ma Luyi, Du Qingyin, Li Shijian, Yang Lixin, Liu Gang, Wang Xinyu Heat Treatment of Metals    2024, 49 (7): 42-46.   doi:10.13251/j.issn.0254-6051.2024.07.007 Abstract （136）      PDF （2973KB）（96）       Knowledge map    Thermodynamic equilibrium phase composition, Jominy hardenability, phase transition, thermophysical properties and mechanical properties after quenching and tempering of the 16CrSiNi steel were simulated by using JMatPro software, and the thermodynamic equilibrium phase compositions, hardenability curves, TTA curves, TTT curves, CCT curves, quenching microstructure, mechanical properties after quenching and tempering, thermophysical properties under different temperatures as density, thermal conductivity, Young's modules, specific heat, Poisson's ratio and enthalpy were obtained. Reference | Related Articles | Metrics

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  Effect of solution treatment on microstructure and low temperature impact properties of 022Cr22Ni5Mo3N duplex stainless steel Cui Liyun, Liu Qingtao, Luo Rui, Qian Xigen, Ding Hengnan, Sun Xi, Zhao Xiaotao, Liu Heng, Cheng Xiaonong Heat Treatment of Metals    2024, 49 (10): 18-24.   doi:10.13251/j.issn.0254-6051.2024.10.003 Abstract （155）      PDF （5070KB）（95）       Knowledge map    Solution treatment for as-forged 022Cr22Ni5Mo3N duplex stainless steel was carried out, and the effects of solution temperature (1000-1100 ℃) and time (1 h and 2 h) on the microstructure and -46 ℃ low temperature impact properties were studied. The results show that with the increase of solution temperature, the austenite content of the 022Cr22Ni5Mo3N stainless steel decreases, the phase boundary of austenite tends to be smooth and the number of needle-type and island austenite in ferrite decreases gradually. The low temperature impact properties increase first and then decrease with the increase of solution temperature. When the solution temperature is 1050 ℃, the low temperature impact absorbed energy of the 022Cr22Ni5Mo3N stainless steel is higher, which is about 260 J. The solution treatment can change the austenite phase morphology and adjust the phase content. Serrated phase boundaries(below 1050 ℃) and lower austenite phase content(above 1050 ℃) promote the brittle fracture of dual-phase steels at low temperatures, which is the main reason for the reduction of low-temperature toughness. Reference | Related Articles | Metrics

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  Heat treatment for recycled material of DD494 alloy turbine blade Yang Shanjie, Hao Zhibo, Yuan Xiaofei Heat Treatment of Metals    2024, 49 (6): 1-7.   doi:10.13251/j.issn.0254-6051.2024.06.001 Abstract （98）      PDF （5742KB）（92）       Knowledge map    Effect of three types heat treatment processes on the microstructure, creep rupture properties and fracture mechanism of recycled material of the DD494 alloy turbine blade was studied. The initial melting temperature of the alloy was determined by metallographic observation. The effect of solution treatment temperature on the dissolution of γ/γ′ eutectic and γ′ phase morphology, and the effect of first aging heat treatment temperature on the size, quantity and distribution of γ′ phase were analyzed by using scanning electron microscope (SEM). The results show that the initial melting temperature of the alloy is between 1310 ℃ and 1315 ℃. After heat treatment at 1300 ℃ for 4 h followed by air cooling, the number of γ/γ′ eutectic and the size of γ′ phase are decreased compared to that of 1290 ℃ for 4 h followed by air cooling. Compared to single step solution, segmented solution treatment can reduce the eutectic content in the alloy. It is found that the higher first aging heat treatment temperature (1140 ℃ compared with 1080 ℃) causes the growth of primary γ′ phase and a large amount of fine secondary particles γ′ precipitated in the γ matrix. The optimal heat treatment process for the alloy is segmented solution treatment+high temperature first aging+secondary aging, i.e. 1280 ℃×1 h+1290 ℃×2 h+1300 ℃×6 h, AC+1140 ℃×3 h, AC+870 ℃×20 h, AC. The average creep rupture life of the alloy treated with the optimal process is 175.05 h, which is more than twice that of the specimen treated with “single step solution+low temperature first aging+secondary aging”. Reference | Related Articles | Metrics

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  Numerical simulation of spiral bevel gear quenching based on thermo-fluid-solid coupling model Liu Ganhua, Deng Shiyi, Huo Xiaodong Heat Treatment of Metals    2024, 49 (7): 16-21.   doi:10.13251/j.issn.0254-6051.2024.07.003 Abstract （68）      PDF （2435KB）（86）       Knowledge map    Based on thermo-fluid-solid coupling simulation, quenching and cooling process of 45 steel spiral bevel gears was numerical simulated, and the influence of quenching medium flow rate on quenching results was studied. It is found that the maximum relative errors between the cooling curves of thermo-fluid-solid coupling simulation and traditional simulation and experimental measurement are 9.2% and 7.4%, respectively. Moreover, more accurate prediction of temperature distribution under quenching medium flow conditions is achieved, verifying the accuracy and convenience of this method. When the inlet flow rate is 2 m/s, the maximum hardness value is 52.0 HRC, and the residual stress is mainly favorable compressive stress. Reference | Related Articles | Metrics

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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）      PDF （2775KB）（82）       Knowledge map    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. Reference | Related Articles | Metrics

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  Development outline 2035 of China heat treatment Heat Treatment of Metals    2025, 50 (1): 1-5.   Abstract （76）      PDF （1038KB）（81）       Knowledge map    Related Articles | Metrics

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  Research status of high-temperature mechanical properties and deformation mechanism of FeMnCoCrNi high-entropy alloy Sheng Jian, Li Dazhao, Yan Zhijie, Bai Shaobin, Chen Yongan, Xie Ruofei Heat Treatment of Metals    2024, 49 (10): 211-219.   doi:10.13251/j.issn.0254-6051.2024.10.035 Abstract （187）      PDF （4238KB）（80）       Knowledge map    As a class of emerging advanced metal materials in recent years and based on the unique multi-principal element alloy design concept, high-entropy alloys (HEAs) are expected to break through the performance limit of traditional single-principal element alloys. Among them, FeMnCoCrNi HEA is one of the most widely studied systems with excellent mechanical properties and broad application prospects. The unique “four core effects” of HEAs were firstly introduced, including high entropy effect, lattice distortion effect, hysteresis diffusion effect and cocktail effect. Secondly, the research status of FeMnCoCrNi high entropy alloy in high temperature tensile properties, high temperature creep properties and corresponding deformation mechanisms was reviewed. Reference | Related Articles | Metrics

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  Effects of carbon content and heat treatment on microstructure and mechanical properties of TiAl alloys with high Nb Gao Yukui, Fang Wenyi Heat Treatment of Metals    2024, 49 (8): 9-14.   doi:10.13251/j.issn.0254-6051.2024.08.002 Abstract （96）      PDF （2905KB）（74）       Knowledge map    Taking Ti-44Al-8Nb-xC(x=0, 0.3, 0.6) alloys as the research object, the effects of three different carbon contents and two aging temperatures on the microstructure, microhardness and high-temperature tensile properties were studied. The results show that when the carbon content increases to 0.6%, Ti2AlC precipitates in the alloy. When the aging temperature increases from 800 ℃ to 900 ℃, Ti3AlC precipitates in the alloy containing carbon. The increase in carbon content and aging temperature are all beneficial to improving the microhardness and tensile strength at 850 ℃ of the alloy, where the highest microhardness is (477.6±9.1) HV0.3, and the highest tensile strength at 850 ℃ is (605.07±5.01) MPa, which increases by 32.7% compored to the lowest tensile strength. The elongation is related to the number and size of carbides, and all the tensile fractures show brittle fracture. The alloy with 0.3% carbon has the best plasticity when aged at 900 ℃, the highest elongation is 5.41%±0.42%, which increases by 67.5% compared to the lowest elongation. Reference | Related Articles | Metrics

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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）      PDF （3505KB）（73）       Knowledge map    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

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  Effect of natural aging on Portevin-Le Chatelier effect of TiB2/7050 aluminum matrix composites Shang Hongshuai, Han Wenfeng, Jie Zhaocai, Yuan Binxian Heat Treatment of Metals    2024, 49 (5): 81-87.   doi:10.13251/j.issn.0254-6051.2024.05.013 Abstract （41）      PDF （3125KB）（72）       Knowledge map    Effect of natural aging time on Portevin-Le Chatelier effect (PLC effect) of TiB2/7050 aluminum matrix composites was investigated. Firstly, room temperature constant strain rate tensile tests were carried out on the TiB2/7050 aluminum matrix composites, which was solution treated and water cooled, and then naturally aged for different time. Then the average serration amplitude, fall time, recovery time and critical strain were analyzed to study the influence of natural aging time on PLC effect. Finally, the morphology of the tensile fracture was observed by means of scanning electron microscope. The results show that the natural aging time within 1 h has a little effect on strength of the TiB2/7050 aluminum matrix composites, but the yield and tensile strengths increase significantly when the natural aging time is more than 1 h. The type of PLC bands evolves with the prolongation of natural aging time from the class B (0-1 h) with jumping nature to the class A (1.5 h) with continuous propagation, and then to the class D (2-4 h) with step propagation characteristics. When the natural aging time exceeds 1 h, the tensile fracture dimples of the TiB2/7050 aluminum matrix composites become significantly shallower and the size becomes smaller, indicating that the plasticity of the composite decreases with the extension of natural aging time. Therefore, the interval between solution treatment and artificial aging of the TiB2/7050 aluminum matrix composite should not beyond 1 h. Reference | Related Articles | Metrics

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  Effect of annealing temperature on microstructure and mechanical properties of low-density steel for bogie frame Wu Si, Li Feifan, Wang Xuemin, Shang Xueliang, Xu Xiangyu Heat Treatment of Metals    2024, 49 (6): 8-16.   doi:10.13251/j.issn.0254-6051.2024.06.002 Abstract （88）      PDF （8960KB）（69）       Knowledge map    Effect of annealing temperature on the microstructure and mechanical properties of a medium-Mn low density medium thick plate for bogie was designed and investigated by means of Thermo-Calc calculations, scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), tensile tests and machine learning from the perspectives of phase transformation, densities of geometrically necessary dislocations, grain boundary types and grain boundary density. The results show that the hot-rolled microstructure of the low-density steel at room temperature consists of δ-ferrite, austenite, and martensite. The matrix undergoes reverse transformation and the growth of prior austenite during annealing treatment, and the stability of austenite decreases with the increase of annealing temperature. The densities of geometrically necessary dislocations of the tested steel decrease with the increase of annealing temperature. The growth of the grains and the merging of martensite laths during annealing lead to a decrease in the density of prior austenite grain boundaries and martensite lath boundaries. The annealed tested steel shows significantly higher elongation than that of the hot-rolled state, with yield strength decreasing as the annealing temperature increasing. The tested steel under both hot-rolled and annealed states shows uniform deformation and cleavage fracture during tensile test. After annealing at 820 and 880 ℃, the yield strength of the tested steel reaches 491 and 413 MPa, respectively. Reference | Related Articles | Metrics

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  Stress corrosion behavior of TP347H stainless steel and BT700-l alloy Li Dongsheng, Liu Rencai, Tu Yuhang, Lan Keyu Heat Treatment of Metals    2024, 49 (8): 1-8.   doi:10.13251/j.issn.0254-6051.2024.08.001 Abstract （70）      PDF （4805KB）（69）       Knowledge map    Stress corrosion cracking (SCC) behavior of TP347H stainless steel and BT700-l alloy in high concentration salt corrosion environment was studied by using slow strain rate tensile (SSRT) stress corrosion test. The results show that there is no SCC behavior between the TP347H stainless steel and BT700-l alloy in high concentration salt solution with different pH values. The TP347H stainless steel and BT700-l alloy show a certain SCC tendency under the condition of Cl- sensitization and H+ catalysis in acidic corrosion environment, and the fractures are tough-brittle mixed cracking. The stress corrosion resistance of the BT700-l alloy in acid corrosion environment is significantly higher than that of the TP347H stainless steel. Reference | Related Articles | Metrics