20 May 2022, Volume 46 Issue 5
    

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    Technical Review
  • MA Zhen, ZHANG Shitao, LIU Zhengyi, LI Wenge, RUAN Haini, CHEN Meitong, ZHAO Yuantao
    Materials For Mechanical Engineering. 2022, 46(5): 1-8. https://doi.org/10.11973/jxgccl202205001
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    The research progress of FeCoNiCr high-entropy alloy coatings prepared by atmospheric plasma spraying is reviewed, and the research progress of alloy components selection, spraying technology, coating structure and properties, and post-treatment technology are summarized in detail. Several problems such as the immature optimization of existing spraying process, the insufficient design of coating composition and the lack of research on the structure and properties are proposed, and the research directions and routes are put forward in a targeted manner, which provides reference and guidance for the follow-up research, application and development of FeCoNiCr high-entropy alloy coatings.
  • Testing & Research
  • YANG Kaihuai, YE Huijuan, HUA Nengbin
    Materials For Mechanical Engineering. 2022, 46(5): 9-15,21. https://doi.org/10.11973/jxgccl202205002
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    The effects of normal load on microscratch and nanoindentation behaviors of Ti40Zr10Cu38Pd12 bulk amorphous alloy were investigated by using microscratch tester and nano-indenter. The results show that as the normal load increased from 2 N to 10 N, the plastic deformation at the scratches of the amorphous alloy gradually changed from uniform to localized, which led to the initiation and expansion of multiple shear bands, the scratch width increased significantly, and the accumulation of wear debris was formed at the end of the scratch. As the normal load increased from 1 mN to 7 mN, the plastic deformation at the indentation of the amorphous alloy gradually accumulated, and the elastic modulus and hardness decreased, manifesting as a strain softening phenomenon, which was related to the increase of free volume of the shear band during the deformation process.
  • HUANG Bin, MENG Fanying, DING Liu, WU Junxia, ZHANG Wei, WANG Yongshan, LI Peiyou
    Materials For Mechanical Engineering. 2022, 46(5): 16-21. https://doi.org/10.11973/jxgccl202205003
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    Ti49Ni51 alloy rods were prepared by rapid solidification technique, and the as-cast alloy rods were subjected to quasi-static loading and unloading compression tests under different cyclic strains (5.0%, 6.0%, 6.5%) at an ambient temperature of 10℃. The effects of cyclic strains on the microstructure and properties of the alloy were studied, and hyperelastic behavior of the alloys under different cyclic strains was discussed. The results show that the Ti49Ni51 alloy after test was composed of B2-TiNi matrix phase, Ti3Ni4 precipitation phase and Ti2Ni precipitation phase under three cyclic strains. With increasing cyclic strain, the equiaxed B2-TiNi grains were gradually elongated, and the Ti3Ni4 phase increased, and part of the Ti3Ni4 phase at the grain boundary aggregated and became larger due to extrusion. Martensitic transformation stress platform existed in the stress-strain curves of the alloy under three cyclic strains, and the stress platform was not obvious under 5.0% cyclic strain. Under 6.0% and 6.5% cyclic strains, with increasing number of cycles, the dissipative energy decreased while the recoverable strain energy density increased. Compared with those under 6.0% cyclic strain, the dissipated energy under 6.5% cyclic strain was slightly lower, while the recoverable strain energy density was higher. The Ti49Ni51 alloy had good hyperelasticity. The hardness of the alloy increased with increasing cyclic strain.
  • ZHANG Quancheng
    Materials For Mechanical Engineering. 2022, 46(5): 22-27,35. https://doi.org/10.11973/jxgccl202205004
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    Referring to 5052 alloy, a new Al-Fe-Mn wrought aluminum alloy was developed by removing Mg and adjusting the content of Fe, Mn, Cr and rare earth elements, and the effects of precipitate and texture on PLC (Portevin-Le Chatelier) effect of the two aluminum alloys were studied. The results show that a strong rolling texture Brass{110}〈112〉 was formed in 5052 alloy, which produced an obvious PLC effect, and the interaction between a large amount of fine Mg2Al3 phase precipitated in the alloy and dislocation made the PLC effect stronger first and then weaker with increasing plastic strain. The Al-Fe-Mn alloy was mainly composed of recrystallized texture Cube{001}〈100〉, resulting in high plasticity of the alloy, and the FeAl3 precipitate with larger size had relatively weak pinning effect on dislocation, and no PLC effect occurred in the alloy.
  • LI Zhi, CHEN Xuan, WU Xiaochun
    Materials For Mechanical Engineering. 2022, 46(5): 28-35. https://doi.org/10.11973/jxgccl202205005
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    During solution treatment, two cooling methods, oil cooling and slow cooling, were used to simulate the surface and core microstructures of a large section new prehardened plastic-working die steel SDP1Cu. The effects of different aging treatments (350-600℃ for 1-20 h) on the microstructure and hardness were studied, and the aging precipitation strengthening mechanism were discussed by resistance method and aging theory. The results show that with increasing aging temperature and time, the oil-cooled martensite and slow-cooled bainite structure gradually decomposed and finally disappeared, and cementite particles were dispersed on ferrite matrix. After aging at 500℃ for 2-20 h, the hardness difference between oil-cooled and slow-cooled steels was within 0.5 HRC, and the cross-section hardness uniformity was good. The copper-rich precipitates started to precipitate when the temperature was higher than 400℃. With increasing aging temperature, the size of precipitates increased, and the precipitation strengthening mechanism changed from dislocation cutting mechanism combining modulus strengthening and coherence strengthening to dislocation bypassing mechanism.
  • ZHANG Shanglin, XUAN Fuzhen, QIU Yang, XIE Guofu, LI Guodong
    Materials For Mechanical Engineering. 2022, 46(5): 36-41. https://doi.org/10.11973/jxgccl202205006
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    Creep-fatigue test was conducted on P92 steel at 625℃. The effects of strain amplitude (0.4%-1.4%) and holding time (30-300 s) on cyclic deformation behavior of P92 steel were analyzed, and micro-mechanism under creep-fatigue interaction was discussed and compared by low-cycle fatigue tests. The results show that creep-fatigue interaction caused the transformation from non-Masing property to Masing property of P92 steel, and stress relaxation during holding time led to accelerated cyclic softening under creep-fatigue loading. During fatigue process, the microstructure of P92 steel changed inhomogeneously, the dislocation density decreased, and finally an elongated subgrain structure was formed. During creep-fatigue process, the microstructure change and dislocation density decrease of P92 steel were more uniform and significant, and finally equiaxed subgrains or dislocation cell structures were formed, accompanied by the coarsening of precipitates.
  • HUANG Yuansheng, WEN Lizhe
    Materials For Mechanical Engineering. 2022, 46(5): 42-46. https://doi.org/10.11973/jxgccl202205007
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    AlxTixNixCoCrCu0.5FeMo (x=4, 5, 6, 7, 8, 9, molar ratio) high-entropy alloy coating was laser cladded on the surface of 40Cr steel and annealed at 300-900℃. The effect of annealing temperature on the microstructure and properties of the coating was studied. The results show that both unannealed and 300℃ annealed high-entropy alloy coatings had a single body-centered cubic (BCC) phase structure, and Al2Ti3-like intermetallic compound phase was formed in the alloy coatings after annealing at 500-900℃. When the annealing temperature increased to 500℃, the intragranular corrosion resistance became poor, and the corrosion resistance of the coating decreased with increasing annealing temperature. With increasing annealing temperature, the hardness of the high-entropy alloy coating first decreased, then increased and then decreased. The Al4Ti4Ni4CoCrCu0.5FeMo alloy annealed at 700℃ had the highest hardness, which was 1 019 HV.
  • Material Properties & Application
  • ZHANG Zhan, TAN Dawang, LUO Sichun, GUO Weiming, LIN Huatai
    Materials For Mechanical Engineering. 2022, 46(5): 47-52,57. https://doi.org/10.11973/jxgccl202205008
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    Using Y2O3 as sintering aid, α-Sialon ceramics with MoSi2 as a second phase were prepared by spark plasma sintering. The effect of the MoSi2 adding amount (0-10wt%) on the microstructure and properties of the ceramics was studied. The results show that after adding MoSi2, the α-Sialon grains in the ceramics changed from equiaxed to long rod-like. With increasing MoSi2 adding amount, the long rod-like α-Sialon grains increased significantly, and the aspect ratio increased; when the addition of MoSi2 was 10wt%, the grain size exhibited a significant bimodal distribution. When the addition of MoSi2 increased from 0 to 10wt%, the relative density of the ceramics increased from 99.0% to 99.7%, the hardness decreased from 21.12 GPa to 20.44 GPa, and the fracture toughness increased from 4.80 MPa·m1/2 to 6.13 MPa·m1/2. In dry cutting of nickel-based superalloy, the cutting length of the ceramic tool with 10wt% MoSi2 was 1.5 times that of the ceramic tool without MoSi2 when it reached the wear standard, indicating the tool had excellent cutting performance; the main wear forms of the tool were flank wear and groove wear, and the main wear mechanisms were adhesive wear and abrasive wear.
  • HU Fengfeng, LIN Yongyong, ZHANG Huade, JIA Hepeng
    Materials For Mechanical Engineering. 2022, 46(5): 53-57. https://doi.org/10.11973/jxgccl202205009
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    Friction stir welding was carried out on 3 mm and 4 mm thick 6061-T6 aluminum alloy plates at high welding speeds (3 000 mm·min-1), respectively. The effect of high rotational speed (4 000-6 000 r·min-1) on microstructure and tensile properties of the joints was studied. The results show that the smaller the rotation speed, the easier the formation of hole defects. The higher the rotation speed was, the easier the overheated oxidation appeared. Increasing rotation speed was conducive to the recrystallization of the joint area to form a dense structure. The welding defects of welded joints of 4 mm thick aluminum alloy plates were more serious than those of welded joints of 3 mm thick aluminum alloy plates. The welding joint quality and tensile properties of 3 mm thick aluminum alloy plate at a rotation speed of 5 000 r·min-1 were the best, and the tensile strength and elongation after fracture were 265.82 MPa and 4.58%, respectively. The welding joint quality and tensile properties of 4 mm thick aluminum alloy plate at a rotation speed of 6 000 r·min-1 were the best, and the tensile strength and elongation after fracture were 212.14 MPa and 4.03%, respectively.
  • ZHU Li, HU Yanan, WU Shengchuan, LI Fei, YU Wenjun, LIN Bo, LI Guangjun
    Materials For Mechanical Engineering. 2022, 46(5): 58-63. https://doi.org/10.11973/jxgccl202205010
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    Three interlayer temperature control schemes of continuous welding, welding next layer after welding layer was cooled to room temperature, welding next pass after welding pass was cooled to room temperature, and two annealing temperatures of 730, 600℃ were selected, and the optimal process of gas tungsten arc welding (GTAW) for large-thickness TC4 titanium alloy cast plate was determined by microstructure, tensile properties and fatigue properties. The mechanical properties of welded joint under the optimal process were studied. The results show that the welded joint by welding next layer after welding layer was cooled to room temperature had the smallest weld microstructure and the highest fatigue life, and the welded joint after annealing treatment at 730℃ had better tensile properties; so they were determined as the optimal process. Under the optimal process, the hardness of weld of the GTAW joint was slightly higher than that of base metal, and the joint was a highly matched joint. The joint fractured at base metal during both tension and fatigue processes, but the fatigue cracking resistance of the weld was lower than that of base metal.
  • ZHOU Yuzhang, WEI Wanxin, LUO Sichun, GUO Weiming, LIN Huatai
    Materials For Mechanical Engineering. 2022, 46(5): 64-69,76. https://doi.org/10.11973/jxgccl202205011
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    Si3N4 ceramic with mass fraction of 5% TiO2 was prepared by gas pressure sintering and was made into a cutting tool. The effects of TiO2 on its microstructure, mechanical properties and cutting performance were investigated, and compared with Si3N4 ceramic sintered without TiO2. The results show that the sintered Si3N4 ceramic with TiO2 was mainly composed of long rod-shaped and equiaxed β-Si3N4 grains, accompanied by uniformly distributed TiN phases. Compared with the sintered Si3N4 ceramic without TiO2, the grains were refined, and the hardness increased while the fracture toughness decreased slightly. In the continuous cutting process of gray cast iron, Si3N4 ceramic cutting tool with TiO2 had a longer cutting life (effective cutting length of 2 410 m) and maintained the integrity of the cutting edge, and had less adhesive wear debris after cutting.
  • ZHANG Bowen, DENG Weitao, ZHAO Yuantao, LI Wenge
    Materials For Mechanical Engineering. 2022, 46(5): 70-76. https://doi.org/10.11973/jxgccl202205012
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    Mo2NiB2-based cermet coating was prepared on the surface of Q235 steel substrate by atmospheric plasma spraying, and the effect of powder feeding rate (40-80 g·min-1) on the hardness, bonding strength and corrosion resistance of Mo2NiB2 coating was studied. The results show that the Mo2NiB2 coating was mainly composed of Mo2NiB2 ceramic phase, MoNi4 alloy phase and MoB2 hard phase under different powder feeding rates, and the coating quality was the best when the powder feeding rate was 60 g·min-1. With increasing powder feeding rate, the hardness and bonding strength of Mo2NiB2 coating increased first and then decreased and both reached the maximum values when the powder feeding rate was 60 g·min-1, which were 2 107 HV and 29.23 MPa, respectively. The corrosion resistance of Mo2NiB2 coating increased with increasing powder feeding rate, and reached the best level when the powder feeding rate was 80 g·min-1.
  • Physical Simulation & Numerical Simulation
  • CHEN Zhichao, XU Peng, GAO Longfei, CHEN Yuyu, CAO An, WANG Min, WANG Shijie
    Materials For Mechanical Engineering. 2022, 46(5): 77-81. https://doi.org/10.11973/jxgccl202205013
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    Based on Eulerian-Eulerian gas-solid two-phase flow model, instantaneous velocity and velocity distribution of shot during shot peening process were simulated and analyzed by of Fluent-EDEM coupling calculation. Space position of shot was recorded by high-speed camera, and the real-time data of shot peening equipment and the image of high-speed camera were uploaded to cloud platform by 5G communication technology. Shot velocity was obtained by image processing, so as to realize the test verification of shot peening simulation. The results show that the relative error between simulation results and measured values of shot velocity under different process parameters was not more than 12.1%, indicating the simulation prediction accuracy of the model was high. The velocity of shot after ejection increased first and then decreased with increasing distance from the nozzle, and the spatial distribution of shot velocity presented a parabolic trend. The developed shot peening intensity analysis software had prediction accuracy of 95%.
  • E Hongwei, ZHENG Xuebin, LI Yadong, HAN Longshuai
    Materials For Mechanical Engineering. 2022, 46(5): 82-87,94. https://doi.org/10.11973/jxgccl202205014
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    Limit strain test of DP780 dual phase steel was carried out with a comprehensive sheet forming test machine. Based on C-H instability theory and M-K groove instability theory, the forming limit curve of DP780 dual phase steel was predicted by using Yld2000 yield criterion and power exponent hardening model, and compared with the test results. The results show that the prediction accuracy of forming limit curve based on M-K groove instability theory and C-H instability theory for the forming limit was 97.97% and 95.82%, respectively. The larger the initial thickness non-homogeneity, the smoother the steel plate surface, which was more conducive to forming. When the initial thickness non-homogeneity was 0.992, the M-K groove instability theory had the highest accuracy in predicting the forming limit of DP780 dual phase steel,with a relative error of 0.66%. The theoretical model can be used as a reliable method to obtain forming limit curve of DP780 dual phase steel in actual stamping production when the initial thickness non-homogeneity was 0.992.
  • XIAO Yongjian, WANG Yong, JING Xinjing
    Materials For Mechanical Engineering. 2022, 46(5): 88-94. https://doi.org/10.11973/jxgccl202205015
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    Single-period strain controlled creep-fatigue tests were carried out on P92 steel at different temperatures (500-675℃) and strain rates (5×10-6-1×10-4 s-1). The initial cyclic characteristics of the steel under creep-fatigue interaction were studied, and the corresponding constitutive equations were established to describe the cycling process. The results show that at load retention stage there was obvious stress relaxation phenomenon in P92 steel; the stress reduction rate had a small difference at 500-650℃, and increased with strain rate at 675℃; the curves of true stress and stress relaxation with holding time simulated by stress relaxation model derived from the power function were in good agreement with test results except the condition of 675℃, 1×10-5 s-1, and the relative error was less than 4.28%. At loading and unloading stage, when the strain rate was the same and the temperature was not higher than 550℃, the effect of temperature on stress change rate could be ignored; when the temperature was higher than 550℃, the effect of temperature was great; when the temperature was the same, the effect of strain rate was insignificant. The true stress-strain curve and true stress-time curve simulated by Ramberg-Ostgood model were in good agreement with the test results, and the relative error was less than 10.37%.