20 July 2018, Volume 42 Issue 7
    

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  • Research Progress on Irradiation Damage of Austenitic Stainless Steel for Nuclear Reactor
    HAO Yuchen, ZHAO Meiling, LUO Laima
    Materials For Mechanical Engineering. 2018, 42(7): 1-5. https://doi.org/10.11973/jxgccl201807001
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    Different irradiation damage behavior, including irradiation induced change of microstructure, irradiation induced segregation, irradiation induced precipitation and irradiation induced stress corrosion cracking of austenitic stainless steels commonly used in nuclear reactors is summarized. The research direction of irradiation damage of austenitic stainless steels for nuclear reactors is proposed from the aspects of test methods and category of austenitic stainless steel.
  • Fretting Wear Behavior of AZ31B Magnesium Alloy at Different Temperatures
    WAN Xingzhi, LIU Xinlong, WANG Mengjie, CAI Zhenbing, PENG Jinfang, ZHU Minhao
    Materials For Mechanical Engineering. 2018, 42(7): 6-11. https://doi.org/10.11973/jxgccl201807002
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    The tangential fretting wear tests were conducted on AZ31B magnesium alloy with a self-designed fretting wear tester by contact form of ball against plane, the fretting wear behavior of AZ31B magnesium alloy at 20, 100, 200, 300℃ was studied, and the wear mechanism and the tribo-oxidation effect were analyzed. The results show that the fretting of magnesium alloy took place by means of sliding at different testing temperatures. With the increase of testing temperature, the friction factor in the ascending stage increased, and the number of cycles when friction factor reached peak value and stable stage decreased. The wear volume of AZ31B magnesium alloy and total wear volume of friction pair both decreased first and then increased with the increase of testing temperature, and the wear volume of AZ31B magnesium alloy was the smallest at 200℃. The tribo-oxidation on wear scar surface of AZ31B magnesium alloy played a key role in the fretting wear process. The iron oxide transfer layer was formed on the wear scar surface of AZ31B magnesium alloy when the testing temperature was below 200℃; the wear volume decreased with the increase of testing temperature. The iron oxide transfer layer was destroyed at 300℃ and the wear volume increased.
  • Hydrogen Diffusion Behavior and Its Influencing Factors of Grade 690 MPa Medium Mn Steels with Different Composition
    DU Yu, LI Weijuan, GAO Xiuhua, WU Hongyan, HU Jun, DU Linxiu
    Materials For Mechanical Engineering. 2018, 42(7): 12-15,52. https://doi.org/10.11973/jxgccl201807003
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    Double electrolytic cell electrochemistry hydrogen permeation test was conducted on two grade 690 MPa medium Mn steels with different composition in queched state and tempered state. The effects of chemical composition and heat treatment condition of the tested steel, and hydrogen charging current on the hydrogen diffusion behavior were analyzed. The results show that the microstructures of two tested steels after quenching both consisted of lath martensite, and reverted austenite was observed after tempering at 650℃; the reverted austenite content of the tested steel adding alloying elements of Cu, N and Cr was higher and lath martensitic was finer. The difference of the hydrogen diffusion behavior of the two quenched tested steels was not obvious, but after tempering, the hydrogen permeation rate and hydrogen apparent diffusion coefficient in the tested steel added with alloying elements were both relatively small, and the hydrogen permeation time was relatively long. The hydrogen charging current had a little effect on the hydrogen permeation rate of the quenched tested steel, but had a great effect on the tempered tested steel. With the increase of hydrogen charging current, the hydrogen permeation rate and the hydrogen apparent diffusion coefficient of the tempered tested steel both increased, hydrogen permeation time shortened.
  • Microstructure and Tensile Properties of Hastelloy-X Alloy Prepared by Selective Laser Melting
    LIAO Wenjun, FAN Enxiang, FU Chao
    Materials For Mechanical Engineering. 2018, 42(7): 16-22,27. https://doi.org/10.11973/jxgccl201807004
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    Hastelloy-X alloy (as-diposited state) was prepared by selective laser melting, and was treated by thermal isostatic pressure and heat treatments in sequence. The microstructure and tensile properties at room temperature of the alloy after different treatment were investigated. The results show that defects of pores and un-melting powder and sub-structures of melting pool boundaries and dendrites were formed in as-deposited Hastelloy-X alloy at linear energy of 98 J·m-1; with the increase of linear energy, the relative density of the alloy increased and defects amount decreased. After thermal isostatic pressure treatment, the microstructure consisted of equiaxial grains and network carbides. After thermal isostatic pressure and heat treatment, a part of network carbides dissolved and distributed evenly, and the fine second phases precipitated in grains. The fracture mode of as-deposited alloy was brittle fracture. After thermal isostatic pressure treatment, the plasticity of the alloy was improved and the fracture presented a mixed morphology with secondary cracks and dimples. After thermal isostatic pressure and heat treatment, the plasticity was further improved, the room-temperature tensile properties was better than the standard index of forging parts, and the fracture presented the ductile fracture morphology with the dimple center of fractured carbides.
  • Effect of Heat Treatment on Reverted Austenite Content of 04Cr13Ni8Mo2Al Steel
    YANG Xiaohui, LI Xingdong, ZHANG Fan, YUE Caixu, LI Haixia
    Materials For Mechanical Engineering. 2018, 42(7): 23-27. https://doi.org/10.11973/jxgccl201807005
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    The effects of aging treatment at different temperatures and following low-temperature treatment on the content of reverted austenite and hardness of 04Cr13Ni8Mo2Al steel were studied with rapid phase transition instrument,X-ray stress analyzer, optical microscope and hardness tester. The results show that the starting temperature of martensite transformed to austenite (Ac1) of the tested steel was 620℃, and the finishing temperature of martensite transformed to austenite (Ac3) was 675℃. With the increase of aging temperature,the content of reverted austenite remained constant first,then increased rapidly, and then decreased rapidly. The reverted austenite content reached the maximum of 35vol% at aging temperature of 620℃. The Vickers hardness decreased at the aging temperature below Ac1 with the increase of aging temperature, increased slightly at the aging temperature over Ac1 because of the formation of martensite, and decreased slightly at the aging temperature close to 700℃. After low-temperature treatment, the Vickers hardness of the aged test steel increased, the content of reverted austenite decreased, and the variation amount of reverted austenite content before and after low-temperature treatment increased with the increase of aging temperature.
  • Preparation, Microstructure and Electrochemical Performance of Nano-Sized MnO2
    TANG Huili, REN Yu
    Materials For Mechanical Engineering. 2018, 42(7): 28-31,56. https://doi.org/10.11973/jxgccl201807006
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    Nano-sized MnO2 was synthesized by loading KMnO4 on a mesoporous silica KIT-6 template and calcination at different temperatures (400-700℃). The microstructure and electrochemical performance of nano-sized MnO2 at different calination temperatures were studied. The results show that the prepared nano-sized MnO2 was composed of δ-MnO2 with layered structure when calcined at 400℃, δ-MnO2 with layered structure and a small amount of α-MnO2 with tunnel structure when calcined at 500℃, α-MnO2 with tunnel structure which presented ordered mesoporous morphology and rod shape morphology, respectively, when calcined at 600℃ and 700℃. The α-MnO2 with tunnel structure showed a better cycling stability than that of δ-MnO2 with layered structure, and had a discharge capacity more than 100 mAh·g-1 after 50 cycles of charge-discharge at a current density of 100 mA·g-1.
  • Relation between Friction and Wear Properties and Microstructure of Special Brass
    FANG Wei, FANG Qian, CHANG Ruobin, LI Shaomin, ZHANG Fanyong, LIU Baoxi, YIN Fuxing
    Materials For Mechanical Engineering. 2018, 42(7): 32-36. https://doi.org/10.11973/jxgccl201807007
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    The relation between the friction and wear properties and microstructure of three kinds of special brass with different composition was studied by electron probe microanalysis, scanning electron microscopy, X-ray diffraction and friction and wear testing. The results show that the wear mechanism of special brass was closely related to the matrix phase. The wear mechanism of the special brass with β+α phase was mainly adhesive wear, and that of the special brass with single β phase was mainly abrasive wear. The matrix structure had a greater influence on the friction and wear properties of the special brass. The wear rate of the special brass with β+α phase was obviously smaller than that with single β phase. The wear resistance of special brass containing Fe3Al hard phase was better than that containing Mn5Si3 hard phase when the matrix structure was composed of single β phase.
  • Influence of C, Cr and Mo Elements on Microstructure and Properties of X70 Pipeline Steel
    JIANG Jinxing, YU Xinpan, PAN Xuefu, WU Huibin
    Materials For Mechanical Engineering. 2018, 42(7): 37-40. https://doi.org/10.11973/jxgccl201807008
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    Chemical composition of X70 pipeline steel was adjusted, and the effects of C, Cr, Mo elements on the microstructure, mechanical properties and wear resistance of the pipeline steel were studied. The results show that the microstructures of the tested steels with different composition were composed of acicular ferrite, quasi-polygonal ferrite and granular bainite, and the mechanical properties all met the requirements of API SREC 5L specifications for X70 pipeline steel. Increasing the content of C or Cr element appropriately increased the tensile strength and wear resistance of the tested steel. Mo element had little effect on the tensile strength of the tested steel, and the wear resistance of the tested steel first decreased and then increased when the mass fraction of Mo increased from 0 to 0.22%.
  • Friction and Wear Properties of Different Fibers Reinforced and Different Solid Lubricants Modified PTFE Composites
    HU Gang, CHEN Xueqing, JIN Shilei
    Materials For Mechanical Engineering. 2018, 42(7): 41-44. https://doi.org/10.11973/jxgccl201807009
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    Polytetrafluoroethylene (PTFE) composites with different formulas were prepared with carbon fiber or glass fiber as reinforcing fibers and molybdenum disulfide (MoS2) or graphite as solid lubricants. Friction and wear tests under dry friction and oil lubrication conditions was conducted on the composites, the wear morphology of composites was observed, and the influence of different reinforcing fibers and solid lubricants on friction and wear properties of composites was analyzed. The results show that under dry friction condition, when modified with the same solid lubricant, the carbon fiber reinforced PTFE composite had a smaller wear scar width and a larger friction coefficient than that reinforced with glass fiber; with the same reinforcing fiber, MoS2 modified PTFE composite had a smaller scar width and a larger friction coefficient than the graphite modified PTFE composite. Under oil lubrication condition, when modified with the same solid lubricant, the wear scar width of carbon fiber reinforced PTFE composite was smaller than that of glass fiber reinforced PTFE composite, and the friction coefficient was larger; when the reinforcing fiber was the same, the wear scar width of MoS2 modified PTFE composite was slightly smaller and the friction coefficient was larger than that of graphite modified PTFE composite.
  • Hot Compression Behavior of Ti6Al4V Alloy in α+β Two-Phase Region Prepared by Powder Hot Isostatic Pressing
    WANG Min, YIN Yajun, ZHOU Jianxin, NAN Hai, ZHU Langping, WANG Tong
    Materials For Mechanical Engineering. 2018, 42(7): 45-52. https://doi.org/10.11973/jxgccl201807010
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    High-temperature compression tests were carried out on Ti6Al4V alloy prepared by powder hot isostatic pressing with a Gleeble3500 thermal simulator at different temperatures and strain rates. A constitutive equation describing the compression behavior of the alloy in two-phase region was established. The hardening, dynamic softening parameters, and dynamic recrystallization kinetics models of the alloy during hot working were solved. The flow stress model of the alloy in two-phase region was constructed. The results show that the microstructure of the prepared Ti6Al4V alloy was composed of α phase and β phase and presented a typical grid structure. The grids were formed by the small equiaxed α phase with interleaved lamellar α phase inside, and β phase was distributed at the boundary of α phase. The results calculated by flow stress model of Ti6Al4V alloy in α+β two-phase region was in good agreement with the experimental results, and the flow stress model had high accuracy.
  • Flow Stress Constitutive Equation of 2219 Aluminum Alloy During Hot Compression
    YI Zhaoxiang, LI Xinhe, CHANG Shiwu, CAO Quan
    Materials For Mechanical Engineering. 2018, 42(7): 53-56. https://doi.org/10.11973/jxgccl201807011
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    The flow behavior of 2219 aluminium alloy was studied by single pass hot compression at the temperatures of 200-350℃ and strain rates of 0.1-10.0 s-1 with Gleeble-3180 thermal mechanical simulator. The flow stress constitutive equation of 2219 aluminum alloy during hot compression was established and verified by experiments. The results show that the flow stress of 2219 aluminum alloy increased with the increase of strain rate or the decrease of deformation temperature. The change rule of stress calculated by Fields-Backofen constitutive equation was the same with that by experiments, and the relative error between calculated and tested stresses was less than 5%. The constitutive equation described the high temperature flow behavior of 2219 aluminium alloy accurately.
  • Hot Deformation Characteristics and Deformation Resistance Model of 40CrNiMo Steel
    LI Keyuan, WANG Jingzhong, DU Zhongze, WANG Qingjuan, LIU Ajiao
    Materials For Mechanical Engineering. 2018, 42(7): 57-61,66. https://doi.org/10.11973/jxgccl201807012
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    The stress-strain curves of 40CrNiMo steel at the strain rates of 0.1-50 s-1 and deformation temperatures of 800-1 100℃ were obtained by single pass hot compression experiment on the Gleeble-3500 thermo-simulation machine. The microstructure after deformation was observed and the hot deformation characteristics of 40CrNiMo steel were analyzed. The deformation resistance model of the steel was established and verified by experiments. The results show that the relatively high deformation temperature or relatively small strain rate were favorable for the complete dynamic recrystallization of 40CrNiMo steel. When the deformation temperature was 800℃, the amount of dynamic recrystallization grains increased with the increase of the strain rate. When the strain rate was 10 s-1, the amount of dynamic recrystallization grains increased when the deformation temperature increased from 800℃ to 900℃; the complete dynamic recrystallization of 40CrNiMo steel occured at the defermation temperature of 1 000℃; the dynamic recrystallization grains grew up at the deformation temperature of 1 100℃. The calculated dynamic recrystallization activation energy of 40CrNiMo steel was 322.53 kJ·mol-1. The average relative error between deformation resistance calculated by ZHOU Jihua-GUAN Kezhi model and experimental values was 4.82%, indicating a relatively high accuracy.
  • Numerical Simulation of Temperature Field of Friction Plug Welding Area of 7075-T6 Aluminum Alloy
    SI Peiqiang, YAN Chongjing, SONG Yan, ZHENG Yongle, LIU Jiangwei
    Materials For Mechanical Engineering. 2018, 42(7): 62-66. https://doi.org/10.11973/jxgccl201807013
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    By taking 7075-T6 aluminum alloy as the welding material, the heat generation model of friction plug welding was established on the basis of the law of Coulomb friction. The friction plug welding process of 7075-T6 aluminum alloy was simulated by ABAQUS software, and the finite element model of temperature field of the welding area was established. The temperature field of the friction plug welding area was simulated by two heat source loading models including the fixed heat flux and the heat flux based on the test data, respectively, and the simulation results were verified by the experimental results. The results show that the change trends of the temperature field of the welding area using the two heat source loading models were consistent, but the temperature of the welded aluminum plate obtained by the heat source loading model of using the fixed heat flux was higher at the same time. The temperature change trends of the temperature measurement point of the welded aluminum plate by two heat source loading models both agreed with the test results, but the simulation results obtained by using the heat flux based on the test data were more accurate. Therefore, it was feasible to simulate the temperature field of the friction plug welding area of 7075-T6 aluminum alloy by the finite element heat generation model.
  • Hot Deformation Behavior and Constitutive Relationship of FV520B Martensitic Stainless Steel
    HUANG Dan, FENG Wei
    Materials For Mechanical Engineering. 2018, 42(7): 67-72,77. https://doi.org/10.11973/jxgccl201807014
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    The hot deformation behavior of FV520B martensitic stainless steel was investigated by single pass isothermal compression test on the Gleeble-3500 thermal simulation machine at the deformation temperatures of 850-1 150℃ and stain rates of 0.005-5.000 s-1. According to the stress-strain curves and on the basis of Zener-Hollomon parameter and the Arrhenius hyperbolic-sine equation, the constitutive equation of the stainless steel during high temperature compression was established, and was corrected and verified by experiments. The results show that the flow stress of FV520B martensitic stainless steel decreased with the increase of deformation temperature or the decrease of strain rate. The dynamic recrystallization occurred obviously in the stainless steel at 0.005 s-1, 1 000-1 150℃ and 0.050-5.000 s-1, 1 075-1 150℃. The errors between the predicted flow stresses by the constitutive equation and the experimental values were relatively large under the conditions of 0.005 s-1, 850℃ and 5.000 s-1, 850℃ or 925℃. After the constitutive equation was corrected, the correlation coefficient between the predicted flow stress and the experimental value was 0.997 88, and the average relative error was 2.225%. The corrected constitutive equation predicted the hot deformation flow stress of the stainless steel accurately.
  • Evolution of Microstructure and Tensile Properties of 6061 Aluminum Alloy during Multi-directional Forging
    YANG Xing, FENG Qiang, SUN Zanpeng, LIU Zhoupan, ZHENG Zhanguang, CHANG Yanjun
    Materials For Mechanical Engineering. 2018, 42(7): 73-77. https://doi.org/10.11973/jxgccl201807015
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    The multi-directional forging process of 6061 aluminum alloy at initial forging temperatures of 250-350℃ was simulated by finite element simulation method, and the optimal multi-direction forging process was obtained and verified by microstructure observation and tensile property testing. The results show that the optimal initial forging temperature of the multi-directional forging process of 6061 aluminum alloy obtained by finite element simulation was 300℃. At the optimal initial forging temperature, complete dynamic recrystallization of 6061 aluminum alloy occurred after 4 cycles of multi-directional forging; the grains were highly refined and distributed uniformly; size of some grains was less than 1 μm and 6061 aluminum alloy had ultra-fine grains. The tensile properties of 6061 aluminum alloy were significantly improved. The tensile strength increased from 265.33 MPa before forging to 344.74 MPa, and the elongation after fracture decreased slightly.
  • Comparison of Two Rolling Force Models for 49MnVS3 Non-Quenched and Tempered Steel
    FENG Yaoyao, WANG Qingjuan, DU Zhongze, LI Qiang, ZHOU Ying, LU Chao
    Materials For Mechanical Engineering. 2018, 42(7): 78-82. https://doi.org/10.11973/jxgccl201807016
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    Single pass hot compression tests were conducted on 49MnVS3 non-quenched and tempered steel at deformation temperatures of 750-1 000℃ and strain rates of 0.1-50 s-1, and the Zhou Jihua-Guan Kezhi deformation resistance model was obtained according to the true stress-true strain curves. The average unit rolling pressure of 49MnVS3 non-quenched and tempered steel were calculated by Aiklund model and Zhou Jihua-Guan Kezhi deformation resistance model, respectively, and the calculated results were compared. The results show that the average unit rolling pressures calculated by Aiklund model and Zhou Jihua-Guan Kezhi deformation resistance model increased with the increase of strain. The fluctuation of average unit rolling pressure curve calculated by Aiklund model was relatively small, while the fluctuation by Zhou Jihua-Guan Kezhi deformation resistance model was relatively large. The average unit rolling pressure calculated by Aiklund model was relatively large at low strain rate, and that calculated by Zhou Jihua-Guan Kezhi deformation resistance model was relatively large at high strain rate. When calculating the rolling force by Zhou Jihua-Guan Kezhi deformation resistance model, the data obtained from the thermal simulation test was required, and the model was suitable for controlling model. The Aiklund model calculated the average unit rolling pressure with chemical composition and rolling process parameters; the model was applied relatively widely and suitable for rolling process design.
  • Establishment and Application of Tension-Compression Fatigue Life Curve Model for ZL108 Cast Aluminum Alloy
    CHU Qi, ZHANG Chunzhi, REN Fengguo, SHI Lijuan
    Materials For Mechanical Engineering. 2018, 42(7): 83-86. https://doi.org/10.11973/jxgccl201807017
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    Tension-compression fatigue tests were conducted on ZL108 cast aluminum alloy and fatigue live at different stress amplitudes were obtained. On basis of three parameter exponential function, probabilistic stress amplitude-life (P-S-N) curves of ZL108 cast aluminum alloy were obtained. The limit state function for structure fatigue failure was established with fatigue life statisti data from fatigue tests to analyze the fatigue reliability, and was verified by experiments. The results show that the fatigue life of ZL108 cast aluminum alloy decreased with the increase of stress amplitudes, and had a great dispersion at each stress level. The logarithmic fatigue life of ZL108 cast aluminum alloy followed the normal distribution. The reliability calculated by established limit state function for structure fatigue failure were consistent with experimental results, and the maximum relative error was 5.71%.
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