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Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select Microstructure and properties of WTaVNbMo refractory high-entropy alloy layer on W surface Huang Tianyang, Zheng Jiasheng, Tian Linhai, Lin Naiming, Wang Zhenxia, Qin Lin, Wu Yucheng Heat Treatment of Metals    2023, 48 (5): 6-11.   doi:10.13251/j.issn.0254-6051.2023.05.002 Abstract （83）      PDF （2249KB）（105）       Knowledge map    WTaVNbMo refractory high-entropy alloy layers were prepared on the surface of pure tungsten by double-glow plasma surface metallurgy technology with powder metallurgy W18Ta18V20Nb18Mo26 alloy as source target. The temperature of workpiece was 1200 ℃, and the voltage difference between the source and cathode was 300 V, 400 V and 500 V, respectively. The microstructure and phase composition of the alloy layers were examined by scanning electron microscope with attached energy dispersive spectrometer and X-ray diffractometer. The hardness and corrosion resistance of the alloy layers were tested by microhardness tester and electrochemical workstation. The irradiation resistance of the alloy layer was simulated by SRIM software. The results show that the WTaVNbMo high-entropy alloy layers with BCC structure are formed on the surface of pure tungsten under different voltage differences. When the voltage difference is 400 V, the thickness of alloy layer is more than 100 μm. The alloy layer prepared under voltage difference of 500 V has uniform surface, compact structure and the highest hardness, which can reach 1635 HV0.05. The corrosion resistance is good, and the self-corrosion current density decreases by nearly two orders of magnitude compared with that of the W substrate. The irradiation simulation results show that compared with pure tungsten, the damage range of the high-entropy alloy layer is more concentrated, the projected range is shorter, the electronic stopping power is greater, and the ionization loss rate is faster. Reference | Related Articles | Metrics Select Microstructure and hardness of laser clad zirconium coating on austenitic stainless steel Wu Yu, Tang Qi, Su Xiaofeng, Jiang Wenlong, Zhou Danqing Heat Treatment of Metals    2023, 48 (5): 12-17.   doi:10.13251/j.issn.0254-6051.2023.05.003 Abstract （79）      PDF （4859KB）（68）       Knowledge map    In order to improve the surface properties of commonly used austenitic stainless steels, extend their service life, and broaden their use value, the laser cladding technology was used to prepare a zirconium coating on the surface of a typical austenitic stainless steel. The microstructure of the clad coating was characterized by means of metallographic microscopy, XRD, ECC and EDS, and the hardness of the coating and substrate was tested by means of Vickers hardness tester. The results show that the laser clad zirconium coating has good metallurgical bonding with the stainless steel substrate, the coating grains mainly exhibit a dendritic morphology, while the substrate grains mainly exhibit an equiaxed morphology containing annealing twins. In the laser clad coating, Zr and Si elements are mainly concentrated within the dendrites, while Fe and Cr elements are mainly concentrated between the dendrites, and the distribution of Ni and Mn elements is relatively uniform. The hardness of the coating (about 743.2 HV0.1) is significantly higher than that of the substrate (about 230.5 HV0.1), being about 3.2 times that of the substrate, which may be related to the microstructure of the dendritic structure formed in the coating and the segregation of elements therein. In addition, the contribution from second phase strengthening cannot be ignored. Reference | Related Articles | Metrics Select Comparison of microstructure stability and corrosion resistance of nickel based alloys Inconel 740H and 617B Hou Shixiang, Liu Yan, Liu Dongyu Heat Treatment of Metals    2023, 48 (5): 18-24.   doi:10.13251/j.issn.0254-6051.2023.05.004 Abstract （58）      PDF （4262KB）（62）       Knowledge map    Nickel based superalloys Inconel 740H and 617B were aged at 750 ℃ and 780 ℃ for 5000 h, and then corroded in simulated coal-fired environment. The surface and cross sectional microstructures were characterized by TEM, EDS and SEM. The results show that the size of intragranular γ′ phase in the Inconel 740H alloy is about 5 nm before aging, while after aging at 750 ℃ and 780 ℃ for 5000 h, the average size of γ′ phase is about 70 nm and 95 nm, respectively. The intragranular γ′ phase in the 617B alloy is not observed before aging, while after aging, the γ′ phase is precipitated and grows to about 100 nm and 130 nm, respectively, which shows that the microstructure stability of the Inconel 740H alloy is better than that of the 617B alloy. The corrosion test results in simulating coal-fired environment at 750 ℃ and 780 ℃ show that the Inconel 740H alloy has better corrosion resistance than 617B alloy, so the 617B alloy cannot replace Inconel 740H alloy at present. Reference | Related Articles | Metrics Select Behavior of grain boundary precipitates of P91 steel during creep process Gu Baolan, Liu Jiachen, Sun Haoyu, Liu Wang, Yu Haiyang Heat Treatment of Metals    2023, 48 (5): 25-31.   doi:10.13251/j.issn.0254-6051.2023.05.005 Abstract （44）      PDF （4910KB）（36）       Knowledge map    Microstructure evolution and change law of grain boundary precipitates of P91 steel during the 600 ℃ and 650 ℃ creep rupture tests were studied. The results show that during the creep process, martensite lath tends to disperse gradually with the increase of creep rupture time, and the number and size of grain boundary precipitates increase. The grain boundary precipitates are mainly M23C6 and Laves(Fe2Mo) phases, the nucleating location of Laves phase is mainly at the interface of M23C6 phase on the grain boundary, because M23C6 phase on grain boundary has a higher content of Mo than that in the matrix, providing favorable conditions for the formation and coarsening of Laves phase. At the same time, the segregation of Si on grain boundary increases the self diffusion coefficient of the steel, promotes the formation of Laves phase, and also makes the coarsening rate of Laves phase higher than that of M23C6 phase. During the creep process, the hardness of the P91 steel decreases with the extension of creep rupture time, and the higher the test temperature, the more obvious the decrease of the hardness. Reference | Related Articles | Metrics Select Dynamic recrystallization behavior of 34CrNi3MoV alloy steel Zou Zhipeng, Xu Dong, Ren Yicheng, Wang Yiqun, Zheng Lei, Pang Hongxuan Heat Treatment of Metals    2023, 48 (5): 32-40.   doi:10.13251/j.issn.0254-6051.2023.05.006 Abstract （44）      PDF （4619KB）（43）       Knowledge map    Single-pass isothermal compression test with maximum deformation of 50% was conducted by using Gleeble-1500 thermo-mechanical simulator, and the true stress-strain curves for 34CrNi3MoV steel were obtained at deformation temperature of 800-1200 ℃ and strain rate of 0.01-10 s-1. The results show that, at 800 ℃ and 900 ℃ (1, 10 s-1), the 34CrNi3MoV steel undergoes dynamic recovery only, while at 1000-1200 ℃ and 900 ℃(0.01, 0.1 s-1) undergoes dynamic recrystallization. By using Arrhenius equation to calculate the activation energy Q under different strains, the corresponding relationship between activation energy Q and strain is obtained by using the quintic polynomial Q=331.78+1401.47ε-10 233.34ε2+33 725.26ε3-52 745.07ε4+31 981.48ε5. The relationships between critical eigenvalues (εc, εp) and Z parameter are constructed by using work-hardening rate, and based on which a kinetic model for the 34CrNi3MoV steel to predict dynamic recrystallization volume fraction is established: XDRX=1-exp[-0.564((ε-εc)/εp)1.945]. Reference | Related Articles | Metrics Select Microstructure and strengthening mechanism of a novel 700 MPa grade high strength anchor steel Meng Yasen, Pan Lifang, Zhang Hongxu, Liu Peng, Ren Zhifeng, Liu Guangming Heat Treatment of Metals    2023, 48 (5): 41-48.   doi:10.13251/j.issn.0254-6051.2023.05.007 Abstract （43）      PDF （3111KB）（37）       Knowledge map    Microstructure and mechanical properties of a self-designed 700 MPa grade high strength anchor steel were investigated systematically by means of optical microscope, scanning electron microscope as well as transmission electron microscope, etc, and the strengthening mechanisms of the tested steel were further quantitatively discussed. The results show that the microstructure of the tested anchor steel is composed of banded laminated pearlite and fine equiaxed ferrite, the volume fraction of pearlite is about 43%, and in the ferrite there are a large amount of nano-sized V(C, N) precipitated particles (<20 nm). In addition, the tested steel has good comprehensive properties, with the yield strength, tensile strength, and elongation after fracture being respectively about 734 MPa, 936 MPa, and 15.1%, and the yield ratio being about 0.78. The strengthening mechanism of the tested anchor steel is a coupling of grain refining strengthening, solid solution strengthening, dislocation strengthening, and precipitation strengthening, where the contributions induced by grain refining strengthening and solid solution strengthening account for about 73% of the total strength. Reference | Related Articles | Metrics Select Strength evolution law of electric heat treated commercially pure Al wire Zhang Yi, Hou Jiapeng, Yuan Qulong, Zhang Zhenjun, Chen Ling, Zhang Zhefeng Heat Treatment of Metals    2023, 48 (5): 49-53.   doi:10.13251/j.issn.0254-6051.2023.05.008 Abstract （40）      PDF （3454KB）（59）       Knowledge map    Traditionally annealing and electric heat treatment of commercially pure Al wire were carried out by using drying oven and current-providing device, respectively. The influence law and mechanism of traditionally annealing and electrical heat treatment at different temperatures on strength and microstructure of the commercially pure Al wire were investigated. The results show that when the heat treatment temperature is the same, the tensile strength and the grain size of the electric heated commercially pure Al wire is respectively lower and larger than those of the traditionally annealed, the main mechanism of which is the overheating caused by local Joule heating effect on grain boundaries in the commercially pure Al wire. Reference | Related Articles | Metrics Select Effect of ultrafine grain ferrite bimodal structure on mechanical properties of medium carbon steel Zhang Jiahao, Li Hongbin, Zhao Zhihao, Xu Haiwei, Han Yun, Tian Yaqiang, Chen Liansheng Heat Treatment of Metals    2023, 48 (5): 54-59.   doi:10.13251/j.issn.0254-6051.2023.05.009 Abstract （45）      PDF （4849KB）（60）       Knowledge map    A medium carbon steel with 0.49%C was quenched at different temperatures in two-phase zone, then cold rolled 50% and annealed to obtain the ferritic bimodal structure. The microstructure was characterized by means of scanning electron microscope (SEM) and electron backscattered diffraction(EBSD), and the effect of the bimodal structure on mechanical properties was analyzed by tensile experiments at room temperature. The results show that the average grain size of the ferrite decreases with the increase of the quenching temperature in the two-phase zone. The strength of the tested steel is the highest when quenched at 770 ℃, the elongation is the highest at 750 ℃, and the product of strength and elongation is the highest at 760 ℃. When the proportion of submicron grains is 31.4% and the peak grain sizes of coarse grains and fine grains are respectively 2.51 and 0.79 μm, the tested steel has better matching of strength and elongation. Reference | Related Articles | Metrics Select Micro and nano mechanical properties and corrosion resistance of SLM-printed Al0.5CoCrFeNiTi0.5/316L composites Sun Ying, Zheng Liuwei, Zhang Huiyun Heat Treatment of Metals    2023, 48 (5): 60-65.   doi:10.13251/j.issn.0254-6051.2023.05.010 Abstract （29）      PDF （3835KB）（34）       Knowledge map    316L stainless steel was selected as the matrix material and Al0.5CoCrFeNiTi0.5 high-entropy alloy (HEA) powder was used as the particle reinforcement. The 316L stainless steel matrix composites with different HEA contents were prepared by selective laser melting (SLM). The microstructure, micro and nano mechanical properties and corrosion resistance of the prepared composites were studied. The results show that there is no hole, crack and other defects in the 316L stainless steel and its composites printed by SLM. The remelted zone is mainly composed of fine cellular grains, while the non-remelted zone is composed of cellular grains and equiaxed grains, which is caused by the temperature gradient of the molten pool during solidification. With the increase of HEA content in the composite, both the hardness and the elastic modulus of the composite show an increasing trend, and the strengthening mechanisms are mainly solid solution strengthening and fine grain strengthening. With the addition of HEA alloy, the self-corrosion potential of the composites moves first to negative and then to positive direction, and the self-corrosion tendency increases first and then decreases. Reference | Related Articles | Metrics Select Cause analysis of AS14 annealed microstructure in 4Cr5Mo2V flat steel Chen Jianli, Chu Baoshuai, Zhang Xiaokun Heat Treatment of Metals    2023, 48 (5): 66-69.   doi:10.13251/j.issn.0254-6051.2023.05.011 Abstract （32）      PDF （2476KB）（44）       Knowledge map    Austenitizing at different temperatures+isothermal treatment at bainite transformation temperature+spheroidizing annealing were used to simulate the formation process of AS14 annealed microstructure in the 4Cr5Mo2V flat steel. Leica optical microscope was used to observe the microstructure, 438VP/KEVEX scanning electron microscope/energy dispersive spectrometer were used to analyze the chemical composition in the micro-area of the specimen, and the impact properties of flat steel with different microstructure were tested. The results show that, high final forging temperature leads to the formation of coarse bamboo leaf-like bainite in the steel due to staying within the bainite transformation temperature range or slow cooling after forging. During annealing, carbides nucleate and grow along the interface of coarse bainite, while fewer carbides precipitate between bamboo leaves, forming an AS14 annealed microstructure. The AS14 annealed microstructure has strong structural heritability, which can significantly reduce the transverse impact property of the flat steel. Lower final forging temperature and avoiding staying in the bainite transformation temperature range or slow cooling during cooling process can prevent the formation of AS14 annealed microstructure in the 4Cr5Mo2V flat steel. Reference | Related Articles | Metrics