20 November 2022, Volume 46 Issue 11
    

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  • Research Progress on Sedimentation Stability of Magnetorheological Fluids
    SUN Ruting, MA Ran
    Materials For Mechanical Engineering. 2022, 46(11): 1-8. https://doi.org/10.11973/jxgccl202211001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Magnetorheological fluids have high controllability and continuity, and are widely used in semi-active shock absorbers, polishing devices and torque transfer devices. The sedimentation stability is an important indicator to ensure their performance. The detection method of the sedimentation stability of magnetorheological fluids is summarized, and the research progress on improving the sedimentation stability of magnetorheological fluids is described from three aspects of magnetic particles, additives and carrier fluid. Considering the problems in the sedimentation stability research of magnetorheological fluids, some points of view are put forward for the future research direction.
    • Testing & Research
  • Effect of Melt Overheating Treatment on Pure Purification Behavior and Solidification Microstructure of FGH4096 Nickel-Based Superalloy
    ZHANG Feng, YOU Xiaogang, TAN Yi, ZHUANG Xinpeng, CUI Hongyang, WANG Yiling, CHANG Kai
    Materials For Mechanical Engineering. 2022, 46(11): 9-19. https://doi.org/10.11973/jxgccl202211002
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    FGH4096 alloy was treated by melt overheating process under different melt overheating temperatures (1 415,1 463,1 523 ℃) and overheating times (10, 20, 30 min). The influence of melt overheating on the purification behavior and solidification microstructure of the alloy was studied. The results show that with increasing melt overheating temperature or prolonging overheating time, the secondary dendrite spacing decreased gradually. With increasing overheating temperature, the segregation degree of the elements in the alloy decreased, but the influence of the overheating time on the segregation degree was not significant. When the overheating temperature was 1 415-1 463 ℃, carbon-oxygen reaction mainly occurred in the melt , and the nitrogen absorption reaction was weak, resulting in low oxygen and nitrogen content. When the melt overheating temperature was 1 463-1 523 ℃, MgO crucible decomposition reaction and absorbed nitrogen reaction occurred, resulting in high oxygen and nitrogen content in the alloy.
  • Effect of Powder Ball Milling Time on Microstructure and Properties of Mo2NiB2 Cermet
    DENG Weitao, LI Wenge, ZHANG Yangyang, ZHANG Bowen, ZHANG Shitao, ZHAO Yuantao
    Materials For Mechanical Engineering. 2022, 46(11): 20-25. https://doi.org/10.11973/jxgccl202211003
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    Molybdenum powder, nickel powder and boron powder were mixed by ball milling and press molded, and then Mo2NiB2 cermet was prepared by liquid phase sintering. The effects of powder ball milling time (1,12,24,36,48 h) on microstructure, hardness and electrochemical corrosion resistance of Mo2NiB2 cermet were studied. The results show that under different powder ball milling times, Mo2NiB2 cermets were all mainly composed of Mo2NiB2, MoB and MoNi phases. When the powder ball milling time was 24 h, the raw material powder was most evenly mixed, the content of the Mo2NiB2 phase generated by reaction was the highest, and the relative density of the cermet was the largest. With increasing powder ball milling time, the hardness of the cermet decreased first and increased and then decreased, and the free-corrosion current density increased first and decreased and then increased. When the powder ball milling time was 24 h, the hardness was the highest, and the free-corrosion current density was the smallest, indicating the corrosion resistance was the best. The best corrosion resistance was related to the reduction of diffusion channels of corrosive media due to the fewest pores in the cermet and the promotion of anodic polarization by the high content of Mo2NiB2 phase.
  • Wear Resistance of Plasma Sprayed Ni-Based Alloy Coating on ZL109 AluminumAlloy Surface for Engine Piston
    DU Wei, HAN Bingyuan, CUI Fangfang, HANG Weixing, CONG Mengqi, XU Wenwen, CHU Jiajie, GAO Xianghan, WU Haidong
    Materials For Mechanical Engineering. 2022, 46(11): 26-32. https://doi.org/10.11973/jxgccl202211004
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    A Ni60CuMo alloy coating was prepared by plasma spraying on the surface of ZL109 aluminum alloy for engine piston. The microstructure, phase composition, microhardness and wear resistance under different conditions of the coating were studied. The results show that the coating was composed of alternately overlapping Cr-rich zone and Ni-rich zone, and the bonding mode between coating and substrate was mechanical bonding. The porosity of the coating was 2.48%. The average microhardness was 792.91 HV and was about more than 6 times that of the substrate. The friction coefficient and wear mass loss decreased with increasing test temperature from 25 ℃ to 450 ℃. Under 450 ℃ oil lubrication condition, the average friction coefficient of the coating was 0.037, and the wear mass loss was 7.35 mg, which was only about 1/4 of the substrate. With increasing test temperature, the wear mechanism of the coating changed from peeling failure to oxidation wear and adhesive wear under dry friction condition, and from abrasive wear to abrasive wear and adhesive wear under oil lubrication condition, and finally to adhesive wear.
  • Microstructure and Tensile Properties of New Ni3Al Based Single Crystal Superalloy
    ZHAO Le, LIU Lirong, TIAN Sugui
    Materials For Mechanical Engineering. 2022, 46(11): 33-37. https://doi.org/10.11973/jxgccl202211005
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    A new Ni3Al based single crystal superalloy was prepared by liquid metal cooling (LMC) method and treated by 1 290 ℃×4 h solid solution and 1 000 ℃×4 h aging. The microstructure and tensile properties at different temperatures (23-900 ℃) of the alloy were studied. The results show that the γ' phase in the test alloy structure showed a regular cube shape after solid solution and aging treatment, whose average size was about 0.55 μm and volume fraction was about 72%. The tensile strength and yield strength of the alloy increased first and then decreased with increasing temperature, reaching the peak values at 800 ℃, which was 856 MPa and 808 MPa, respectively. The change of elongation after fracture with temperature was opposite to that of strength; the elongation after fracture reached a minimum value of 11% at 800 ℃. The fracture mode of the alloy was pure shear fracture when stretched at 600 ℃ and below. When stretched at 760 ℃, the alloy had a mixed fracture of pure shear fracture and microporous aggregation. When the tensile temperature was between 800-900 ℃, the alloy fractured in a microporous aggregation fracture mode.
  • Stabilization Treatment and Formation of Rust Layer ofQ500qENH Weathering Bridge Steel
    CHENG Binggui, HAN Limei, LI Li, QU Jinbo
    Materials For Mechanical Engineering. 2022, 46(11): 38-42. https://doi.org/10.11973/jxgccl202211006
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    The rust layer stabilization treatment was carried out on Q500qENH weathering bridge steel samples by combination of coating rust layer stabilizer and water treatment (84 d). The micromorphology, phase composition and formation mechanism of the surface rust layer of the sample were studied. The results show that the surface corrosion of the weathering bridge steel sample with rust layer stabilizer was uniform in the early stage of water treatment, and the rust layer formed in the later stage had good compactness and no obvious cracks inside. After water treatment for 84 d, the rust layers on the surface of the samples with and without rust layer stabilizer were both mainly composed of α-FeOOH, γ-FeOOH and a small amount of Fe3O4, and the mass ratios of α-FeOOH to γ-FeOOH were 2.77 and 1.85, respectively; the surface of the sample with rust layer stabilizer preferentially formed a stable rust layer. The rust layer stabilizer could make the weathering bridge steel quickly form a uniform rust layer, accelerate the formation and transformation of the initial phase γ-FeOOH in the rust layer, increase the content of the stable phase α-FeOOH in the rust layer, promote the formation of the stable rust layer, and shorten the stabilization period of the rust layer.
    • New Materials & Technology
  • Effect of TiC Content on Microstructure and Performance of TiC/ZrO2Conductive Ceramic Composites by Pressureless Sintering
    HUANG Yuntao, ZHANG Jin, YUE Xinyan, ZHANG Cuiping, RU Hongqiang
    Materials For Mechanical Engineering. 2022, 46(11): 43-48. https://doi.org/10.11973/jxgccl202211007
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    TiC/ZrO2 conductive ceramic composites were prepared by pressureless sintering with ZrO2, TiC, TiO2 and phenolic resin as raw materials and combining with in-situ synthesized TiC by carbothermal reduction reaction. The effect of TiC mass fraction (25%-40%) on the relative density, microstructure, mechanical properties and conducivity of the ceramic composites were investigated. The results show that the ceramic composites consisted of TiC and t-ZrO2 phases. With increasing TiC content, the TiC particles in ZrO2 matrix gradually connected with each other and then formed a continuous network structure, the bending strength of the ceramic composites increased first and then decreased, the hardness decreased first and then increased, and the relative density, fracture toughness and resistivity decreased constantly. When the mass fraction of TiC was 30%, the ceramic composite had the best comprehensive properties, whose relative density, bending strength, Vickers hardness, fracture toughness and resistivity were 97.42%, 571 MPa, 12.1 GPa, 3.43 MPa·m1/2 and 3.10×10-5 Ω·m, respectively.
  • Effect of Ti(C,N) Content on Microstructure and Properties ofPressureless Sintered Ti(C,N)/ZrO2 Ceramic Composites
    GUO Guanghan, LIU Jiaqi, HUANG Yuntao, YUE Xinyan, ZHANG Cuiping, RU Hongqiang
    Materials For Mechanical Engineering. 2022, 46(11): 49-54. https://doi.org/10.11973/jxgccl202211008
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    Ti(C, N)/ZrO2 ceramic composites were prepared by pressureless sintering with Y2O3 stabilized nano ZrO2 powder, TiO2 powder, TiN powder, carbon black and water-soluble phenolic resin as raw materials. The effects of Ti(C, N) mass fraction (25%-40%) on the microstructure and properties were studied. The results show that the Ti(C, N)/ZrO2 ceramic composites consisted of t-ZrO2 and Ti(C,N) phases. The Ti(C, N) particles agglomerated gradually with increasing Ti(C,N) content, while distributed relatively evenly when the Ti(C, N) mass fraction increased to 40%. With increasing Ti(C, N) phase content, the open porosity of the ceramic composites increased first and then decreased, and the hardness, flexural strength and fracture toughness decreased first and then increased. When the mass fraction of Ti(C, N) was 40%, the ceramic composites had the best comprehensive performance with the open porosity of 0.73%, the hardness of 14.4 GPa, the flexural strength of 354 MPa and the fracture toughness of 5.8 MPa·m1/2.
  • Effect of Sintering Additive Al2O3-Y2O3 Addition on Structure and Properties ofTiC Ceramics by Pressureless Liquid Phase Sintering
    ZHAO Yiliang, HUANG Nan, RU Hongqiang, ZHANG Cuiping, YUE Xinyan, LIU Chunming, WANG Wei
    Materials For Mechanical Engineering. 2022, 46(11): 55-59. https://doi.org/10.11973/jxgccl202211009
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    TiC ceramics were prepared by pressureless liquid phase sintering at 1 850 ℃. The effect of the mass fraction (0,6%, 8%,10%) of sintering additive Al2O3-Y2O3 (Al2O3 to Y2O3 molar ratio of 1.5) on the microstructure and properties of TiC ceramics was investigated. The results show that TiC phase, YAM (Y4Al2O9) phase and YAG (Y3Al5O12) phase existed in TiC ceramics after adding sintering additive. With increasing mass fraction of sintering additive from 0 to 10%, the relative density of ceramics increased from 94.50% to 97.86%, the open porosity decreased from 0.77% to 0.21%, the YAM and YAG phases increased and gradually aggregated, and the fracture toughness, Vickers hardness and flexural strength all increased first and then decreased. When the mass fraction of sintering additive was 6%, the fracture toughness and Vickers hardness reached the maximum value of 6.2 MPa·m1/2 and 19 GPa, respectively. When the mass fraction of sintering additive was 8%, the flexural strength reached the maximum value of 524 MPa. The resistivity of ceramics was between 1.00×10-6-2.00×10-6 Ω·m, and the addition of sintering additives affected the electrical conductivity little.
    • Materia Testing and Equipment
  • Effects of Sb and Al Elements on Corrosion Resistance of Weathering Steels inSimulated Industrial Atmospheric Environment
    CUI Kaiyu, LI Zhengrong, XU Jiewang, CHEN Shu, WANG Chuangwei, HU Yunfeng, XIONG Xuegang
    Materials For Mechanical Engineering. 2022, 46(11): 60-65. https://doi.org/10.11973/jxgccl202211010
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    Periodic wet/dry corrosion tests were conducted on the self-made Sb-Al composite added Cr-Ni-Cu series weathering steel (1#) and Al-containing Cr-Ni-Cu series weathering steel (2#), and commercially available S450AW Sb-containing weathering steel, Q450EWR1 high Cr weathering steel and Q355B low alloy steel. The corrosion resistance of the five steels and the structure and phase composition of the surface rust layers were compared and studied. The influence of Sb and Al elements on the corrosion resistance was analyzed. The results show that the surface rust layers of the four weathering steels contained high content protective phases including α-FeOOH, Fe3O4 and α-Fe2O3; the corrosion resistance was better than that of Q355B low alloy steel. The inner rust layer of 1# steel was enriched with Si, Cr, Cu, Sb, and Al elements, and the inner rust layer of 2# steel was enriched with Si and Al elements; the enrichment of these elements improved the corrosion resistance of the inner rust layer. The corrosion resistance of 1# steel, 2# steel and S450AW steel was similar, indicating that the composite addition of Sb and Al could ensure the good corrosion resistance of weathering steels while reducing the single addition of Al, Sb, and Cr elements.
  • Effect of Adding Tempering Process on Deformation of GCr15 Bearing Steel Ring
    WANG Yibo, LI Shuxin, SHU Jianming, CHEN Yinjun
    Materials For Mechanical Engineering. 2022, 46(11): 66-70. https://doi.org/10.11973/jxgccl202211011
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    A tempering process (150 ℃×2 h tempering+superfinishing) was added after grinding of the original manufacturing process of GCr15 bearing steel ring (raw material forging→annealing→turning→quenching→tempering→grinding→assembly). The microstructure, residual stress and roundness of the bearing ring were studied and compared before and after adding tempering process, and the effect of adding tempering process on the deformation was analyzed. The results show that after adding tempering process, the microstructure of the bearing ring still mainly consisted of lath matensite, retained austenite and spherical carbide particles; comparing with those under the original process, the fine carbide particle amount increased and the retained austenite content decreased. After adding tempering process, the roundness of the inner and outer surfaces of the bearing ring was reduced by 80% and 60%, respectively, indicating the deformation was reduced significantly. After adding tempering process, residual stresses in the ring decreased and tended to be evenly distributed, and the further precipitation of fine carbides inhibited the strain-induced martensitic transformation, thereby the deformation of the bearing ring decreased and the dimensional stability increased.
  • Friction and Wear Properties of CoCrAlSiY Alloy Coating Prepared byHigh Velocity Oxy-Fuel Spraying
    DENG Wen, TANG Lin, QI Hui
    Materials For Mechanical Engineering. 2022, 46(11): 71-77. https://doi.org/10.11973/jxgccl202211012
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    CoCrAlSiY alloy coatings were prepared by high velocity oxy-fuel spraying. The microstructure and mechanical properties as well as the friction and wear property under different loads (2, 5, 8 N) of the coating were studied. The results show that the CoCrAlSiY alloy coating was composed of CoCr2O4,CoAl and α-Al2O3 phases and the phases distributed uniformly. The coating was compact. The hardness of the coating was (7.41±0.16) GPa, which was close to that of other similar alloy coatings. During friction and wear under 2, 5, 8 N loads, the average friction coefficients of the CoCrAlSiY alloy coating were 0.33, 0.24, 0.22, and the corresponding wear rates were 3.52×10-5, 4.85×10-5, 5.58×10-5 mm3·N-1·m-1, respectively. The wear mechanisms under low load (2 N) were mainly adhesive wear and abrasive wear; under high loads (5, 8 N), brittle fracture occurred to the coating and large pieces peeled off. During friction and wear, oxides were formed on surface of the coating. Under 5 N and 8 N loads, a large number of oxides such as α-Al2O3 and CoCr2O4 appeared on the wear surface.
    • Physical Simulation & Numerical Simulation
  • Mechanical Behavior of Nanocrystalline Copper with Bimodal Structure
    ZHANG Feng, TANG Qiaoyun, CAI Qixing, ZHI Youran, MA Yinzhong
    Materials For Mechanical Engineering. 2022, 46(11): 78-85. https://doi.org/10.11973/jxgccl202211013
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    The deformation mechanism and mechanical properties of nanocrystalline copper with a bimodal structure (grain size obeying bimodal distribution in statistics) were systematically investigated by combination of molecular dynamics simulation, visco-plastic constitutive model and nanoindentation test verification. The results show that during the plastic deformation, dislocations were first nucleated and expanded in the fine grain zone of the nanocrystalline copper, and the directions were parallel to each other; while the dislocation slip directions in the coarse grain zone crossed each other, and the larger the size of coarse grains, the more likely dislocation entanglement and cross-slip occurred. The flow stresses of the nanocrystalline copper with a bimodal structure increased with increasing coarse grain size, and the hardness decreased with increasing volume fraction of coarse grains. The stress variation law calculated by the visco-plastic constitutive equation was consistent with that by the empirical formula and molecular dynamics simulation, and the relative error between the flow stresses calculated by the constitutive equation and the empirical formula was less than 5%.
  • Hot Compression Deformation Behavior and Variable ParameterArrhenius Constitutive Equation of 60 Steel
    ZHAO Jinsong, ZHOU Changlei, HUANG Suxia, LI Hezong
    Materials For Mechanical Engineering. 2022, 46(11): 86-91. https://doi.org/10.11973/jxgccl202211014
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    Hot compression tests were carried out on 60 steel at different temperatures (730, 750, 800, 850, 900, 1 000 ℃) and different strain rates (0.01, 0.1, 1, 5, 10 s-1) with a Gleeble-1500 thermal simulator; the total true strain was 0.8. The deformation behavior of 60 steel during the hot compression process was analyzed. A variable parameter Arrhenius constitutive model was introduced. The relationships between the parameters of the model and the strains were fitted by a fifth-order polynomial, and then the constitutive equation for high temperature deformation of 60 steel was established. The accuracy of the equation was evaluated. The results show that the higher the deformation temperature or the lower the strain rate, the lower the flow stress of 60 steel. At lower temperatures and higher strain rates, the softening mechanism of hot compression deformation of 60 steel was mainly dynamic recovery; at higher temperatures and lower strain rates, it was mainly dynamic recrystallization. The fitting correlation coefficient between the predicted flow stresses by the established variable parameter Arrhenius constitutive equation and the experimental values was up to 0.994 597, indicating that the constitutive equation could describe the high temperature deformation behavior of 60 steel well.
  • Calculation of Tensile Property Parameters of Stainless Steel Materials Based on Indentation Strain
    XUE He, LU Jingzhi, JIA Yulei, WANG Shuang, WANG Zheng
    Materials For Mechanical Engineering. 2022, 46(11): 92-96. https://doi.org/10.11973/jxgccl202211015
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    A three-dimensional finite element model for continuous ball indentation tests was established, and the relationship between residual indentation strains and different material tensile property parameters (elastic modulus of 90-210 GPa, yield strength of 180-300 MPa, strain hardening exponent of 0.1-0.3) was simulated by a single variable method. Finite element simulation of continuous ball indentation tests was performed under 125 sets of material tensile property parameter combinations, and formulas for calculating material tensile property parameters based on residual indentation strains were obtained and verified experimentally. The results show that there was a log-linear relationship between the residual indentation strain and the modulus of elasticity and yield strength, respectively, and a power-law relationship between the residual indentation strain logarithm and the strain hardening exponent. The residual indentation strains of 316L stainless steel measured by the continuous ball indentation test were substituted into the material tensile property parameter calculation formula, and the relative errors between the elastic modulus, yield strength, and strain hardening exponent obtained by inversion and the tensile test results were 1.50%, 1.57%, and 0.22%, respectively, indicating that the stainless steel material tensile property parameter calculation method based on the residual indentation strain could meet the engineering needs.
    • Failure Analysis
  • Burst Cause of 140V Steel Grade Production Casing Pipe During Wellbore Pressure Test
    ZHAO Jinlan, TONG Ke, LI Hong, GUO Jun, LIU Jianxiong, LIU Qing
    Materials For Mechanical Engineering. 2022, 46(11): 97-101. https://doi.org/10.11973/jxgccl202211016
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    The 140 V steel grade production casing pipe bursted during the wellbore pressure test. The causes of the casing pipe burst were analyzed by macromorphology analysis, geometry measurement, mechanical test, metallographic examination, scanning electron microscopy and energy spectrum analysis and so on. The results show that the microstructure, geometric size, mechanical properties and internal pressure strength of the failed casing met the requirements of the standard. The burst mode of the pipe was ductile fracture. The main reason for the burst was that the internal pressure of the pipe exceeded its own pressure bearing capacity, resulting in the overload fracture.
  • Cracking Cause of 700L Steel Trailer Frame Beam and Improvement
    ZHOU Song, FENG Yi, GAO Xiang, SUN Dai, SHEN Juan, WANG Binhua
    Materials For Mechanical Engineering. 2022, 46(11): 102-110. https://doi.org/10.11973/jxgccl202211017
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    700L steel trailer frame beam products in an enterprise under lower service lives cracked. The reason for cracking of the beam was analyzed by testing the fracture morphology, chemical composition, microstructure, mechanical properties, fatigue performance and service performance of the cracked beam, and comparing with those of the uncracked beam. The corresponding improvement was put forward. The results show that the structure of the cracked 700L steel trailer frame beam had mixed crystal phenomenon, led to low toughness and fatigue limit. Under the alternating load, stress concentration occurred at the position between the spring support and the reinforcing plate on the lower wing surface of the beam and the connection between the saddle plate and the beam. Microcracks initiated and growth at the stress concentration position, and eventually led to fatigue fracture of the frame beam. To reduce the risk of cracking, the final rolling temperature should be lowered slightly, and C-shaped reinforcing plate was placed near the inner side of the lower wing surface of the gooseneck to decrease stress concentration of the beam under service conditions.
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