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  • Physical Simulation & Numerical Simulation
    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
    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.
  • Review
    PAN Xincheng, LIN Zhengqi, YANG Liu, DENG Liping
    Materials For Mechanical Engineering. 2023, 47(1): 1-10. https://doi.org/10.11973/jxgccl202301001
    As a commonly used metal material, copper is limited in its application due to its low strength. Because of its excellent comprehensive properties, graphene has attracted wide attention as a potential reinforcement. Graphene reinforced copper matrix composites combine the great properties of both copper and graphene, and have become an research hotspot. The preparation processes and comprehensive properties of graphene reinforced copper matrix composites are introduced. The characteristics of various preparation processes, strengthening mechanism and configuration design are emphatically discussed, and the improvement approaches to solve the two main technical difficulties of weak bonding of composite interface and difficult dispersion of graphene are summarized. Finally, the preparation process of graphene reinforced copper matrix composites is prospected.
  • Failure Analysis
    CHENG Quanshi, HUANG Qingmei, YE Lingying, XU Yongchun
    Materials For Mechanical Engineering. 2022, 46(10): 106-112. https://doi.org/10.11973/jxgccl202210018
    High lock nuts were made from 7075-T73 aluminum alloy that was obtained by T73 heat-treating 7075-T6 aluminum alloy. After serving in an atmospheric environment for about 3.5 a, many nuts cracked. The crack reason was analyzed by chemical composition analysis, microstructure and fracture morphology observation, residual stress testing and other methods. The results show that stress corrosion cracking occurred in the 7075 aluminum alloy high lock nut during service. After the high lock nut was installed, the circumferential residual tensile stress was generated at the closing part, and the surface oxide film was cracked, making the metal substrate in contact with corrosive media in atmosphere. The second phase precipitated locally and continuously along grain boundaries during the heat treatment from T6 to T73 states, providing channels for crack initiation and propagation. Under the combination of these factors, stress corrosion cracking occurred in the high lock nut.
  • Review
    CONG Jiaqi, JI Yunping, WANG Lei, KANG Xueliang, LI Yiming, REN Huiping
    Materials For Mechanical Engineering. 2023, 47(2): 1-6. https://doi.org/10.11973/jxgccl202302001
    Selective laser melting (SLM) is one of the most widely used metal additive manufacturing techniques. Many defects are inevitably produced in the SLM formed parts, including pores, surface layer powder spheroidization, cracks and so on. The formation of defects not only affect the smoothness of the forming process, but also damage the internal integrity of the part and reduce its serviceability. The main characteristics of three defects including pores, surface layer powder spheroidization and cracks in SLM formed 316L stainless steel parts are reviewed. The formation mechanisms and influencing factors of these three defects are summarised, and the main measures to control the defects are proposed. Finally, future research directions are put forword.
  • Material Properties & Application
    YANG Hongbo, LIN Guangqiang, LI Hongyi, WANG Wenjun, LIU Huijun, WANG Yuansheng, ZENG Chaoliu
    Materials For Mechanical Engineering. 2022, 46(12): 72-78,84. https://doi.org/10.11973/jxgccl202212012
    High-Entropy ceramics (La0.2Eu0.2Gd0.2Y0.2Yb0.2)2Zr2O7 were prepared by high-temperature solid state reaction method with La2O3, Eu2O3, Gd2O3,Y2O3, Yb2O3 and ZrO2 powder as raw materials. The preparation process was determined and the microstructure, phase composition, thermophysical properties of the high-entropy ceramics were studied. The high temperature thermal stability was analyzed. The results show that the dual-phase high-entropy ceramics with complete solid solution were obtained by sintering at 1 500 ℃ for 5h followed under furnace cooling. The high-entropy ceramics presented the dual-phase coexistence characteristics of pyrochlore/fluorite with grain size of 200—800 nm; the element distribution was uniform. The thermal conductivity at 800 ℃ of the high-entropy ceramics was 50% of currently used 8YSZ ceramics, and the thermal expansion coefficient was equivalent to that of 8YSZ ceramics. the high-entropy ceramics also showed excellent high temperature thermal stability.
  • Testing & Research
    LIU Changjun, GONG Weizhong, ZENG Xin, XU Xiuqing, LIU Junjie, TAN Jianping
    Materials For Mechanical Engineering. 2022, 46(8): 28-32,39. https://doi.org/10.11973/jxgccl202208005
    The tensile and fracture properties at 20℃ room temperature and -158℃ low temperature of 9Ni steel welded joint, base metal and weld were obtained by experiments, and the effects of temperature on the properties were compared and analyzed. Approximate R6 option 2 failure assessment curves (FAC) for the base metal and weld, as well as FAC for the 9Ni steel welded joint were established and compared. The results show that the tensile and fracture properties of the base metal and the tensile properties of the joint and weld at low temperature were higher than those at room temperature, but the fracture toughness of the weld hardly changed with temperature. The yield strength and fracture toughness of the weld at different temperatures were lower than those of the base metal, and the weld was a weak area of the 9Ni steel welded joint. The envelope area of the approximate option 2 FAC constructed with room temperature tensile properties was slightly smaller than that with low temperature tensile properties, so the approximate option 2 FAC constructed with room temperature tensile properties can be used for safety evaluation of 9Ni steel welded joints. The FAC of 9Ni steel welded joint constructed by segment selection of the approximate option 2 FACs of the base metal and weld at room temperature can be used for safety evaluation of 9Ni steel defect-containing structures at low temperatures in the most conservative way.
  • Testing & Research
    LI Chao
    Materials For Mechanical Engineering. 2022, 46(8): 1-7. https://doi.org/10.11973/jxgccl202208001
    Laser additive manufacturing technique has the advantage of rapidly forming complex-shaped parts, and has received widespread attention in recent years. Two laser additive manufacturing techniques, directed energy deposition and selective laser melting, are introduced. The research progress of laser additive manufacturing formed 316L stainless steel is reviewed from the aspects of common defect, microstructure and texture, and mechanical properties. The current problems of laser additive manufacturing formed 316L stainless steel are analyzed, and its development prospects are prospected.
  • Testing & Research
    ZHU Guangshe, ZHANG Xiaobo, YANG Xuefeng, LIU Yang, ZHANG Liyuan, ZHAO Chunyu, YOU Jiaqing, JIANG Feng, LIU Man, LIU Sijia
    Materials For Mechanical Engineering. 2022, 46(12): 55-59. https://doi.org/10.11973/jxgccl202212009
    The corrosion product composition and morphology on the surface of J55 steel casing in H2S containing block in Changqing Oilfield and in different corrosive enviroments (pure CO2, pure H2S, different partial pressure CO2+H2S enviroments) were analyzed by energy spectrum analyzer, scanning electron microscope and X-ray diffractometer. The corrosion rate was calculated, and the corrosion mechanism of J55 steel casing in H2S containing block was studied. The results show that the coarse-grained FeCO3 corrosion product film with low compactness was formed in a single CO2 environment for J55 steel, whose corrosion rate was high. The addition of H2S made J55 steel form a fine-grained and dense FeS corrosion product film in CO2+H2S environments, which could protect the base metal and significantly reduce the corrosion rate of J55 steel. The corrosion mechanism of J55 steel in sulfur-containing block of Changqing Oilfield was CO2+H2S corrosion dominated by H2S corrosion.
  • Review
    ZHAO Tingting, FAN Likun, LI Yang
    Materials For Mechanical Engineering. 2022, 46(12): 1-8. https://doi.org/10.11973/jxgccl202212001
    When the thermal stress caused by sudden temperature change of ceramic materials exceeds its strength, materials will happen to crack, peel and even fracture, and then failure. Therefore, the study of thermal shock resistance of ceramic materials becomes a hot spot. The evaluation theory of thermal shock resistance of ceramic materials and the methods for testing and characterizing are described. The methods of improving thermal shock resistance, including strengthening and toughening, improving thermal conductivity, reducing thermal expansion coefficient, and reducing elastic modulus, are reviewed. The external influencing factors of thermal shock resistance are summarized. The development direction of improving thermal shock resistance of ceramic materials in future is proposed.
  • Review
    CAO Yida, LIU Chengbao, CHEN Feng, QIAN Junchao, XU Xiaojing, MENG Xianrong, CHEN Zhigang
    Materials For Mechanical Engineering. 2022, 46(10): 8-14. https://doi.org/10.11973/jxgccl202210002
    Reducing NOx emission is one of the most critical global environmental problems. At present, the traditional denitrification technology generally has the problems of high reaction temperature, low catalytic efficiency and high cost. Therefore, new photocatalytic NOx removal technologies such as photocatalytic oxidation and photocatalytic selective reduction have attracted great attention. The research progress in NOx removal by photocatalytic materials is reviewed from two aspects including photocatalytic oxidation and photocatalytic selective reduction. The types of photocatalytic materials, the removal principle and the factors affecting the removal efficiency are emphasized. Finally, the prospects for future development of photocatalytic materials used for denitrification are presented.
  • Testing & Research
    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
    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.
  • Testing & Research
    LIU Linbo, CHEN Jiawen, SHEN Xixun
    Materials For Mechanical Engineering. 2022, 46(8): 22-27. https://doi.org/10.11973/jxgccl202208004
    Bulk nanocrystalline copper with a thinkness of about 600 μm was prepared by electrodeposition, and then was annealed at 100-250℃. The effect of the annealing temperature on the microstructure and mechanical properties of the nanocrystalline copper was studied. The results show that both unannealed and annealed nanocrystalline copper showed a face-centered cubic structure. As the annealing temperature rose from 100℃ to 250℃, the diffraction peak intensity of (200) crystal faces of the nanocrystalline copper gradually increased. With the increase of annealing temperature, the tensile strength of the nanocrystalline copper gradually decreased while the elongation after fracture increased first and then decreased; and the numbers of both the surface tensile deformation zones and the large and deep dimples on the tensile fracture increased. The nanocrystalline copper had the relatively good tensile properties after annealing at 200℃, with the tensile strength up to about 500 MPa and the elongation after fracture of nearly 30.5%.
  • Testing & Research
    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
    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.
  • Physical Simulation & Numerical Simulation
    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
    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%.
  • Material Properties & Application
    CHEN Yanfei, ZHU Zhengqiang, YANG Qunyi
    Materials For Mechanical Engineering. 2022, 46(9): 57-63. https://doi.org/10.11973/jxgccl202209010
    Torsional deformation at 720 ℃ and 500 ℃×60 min annealing treatment were carried out on the 8 mm diameter recycled copper rods prepared by fire refined high conductivity (FRHC) waste copper refining process and continuous casting and rolling process. The effects of torsional deformation and annealing treatment on the microstructure, mechanical properties and electrical conductivity of the copper rod were studied. The results show that twins were generated in the recycled copper rod structure during continuous casting and rolling process, and the twin crossover and the interaction between twins and dislocations caused by torsional deformation made the grains refined. The tensile strength of the recycled copper rod after torsional deformation increased from 215 MPa without torsional deformation to 273 MPa, but the elongation after fracture decreased from 40% to 21%;the hardness increased and the electrical conductivity decreased from 99.37%IACS to 86.78%IACS. After annealing treatment, the recycled copper rod had a structure with equiaxed crystals with more uniform size. The tensile strength was reduced to 208 MPa, while the elongation after fracture increased to 55%; the hardness decreased and the electrical conductivity increased to 98.21% IACS.
  • Materia Testing and Equipment
    ZHANG Bingxian, LEI Longyu, DU Mingke, ZHANG Yunlong, ZHANG Min
    Materials For Mechanical Engineering. 2022, 46(10): 87-91,97. https://doi.org/10.11973/jxgccl202210015
    A laser welding method was used to conduct welding experiments on A286 iron-based superalloy thin plates and the welded joints were subjected to heat heatment with 982℃ solid solution, and 982℃ solid solution+718℃ aging. The influence of heat treatment on the microstructure and mechanical properties of welded joints was studied. The results show that the weld structure of the welded joint was mainly composed of austenite, δ ferrite and γ' phases without heat heatment. After solid solution, the δ ferrite content in the joint weld increased, and the number of γ' phases decreased; the strength and hardness of the joint changed little, compared with those at weld state, but the elongation after the fracture increased from 17.3% at the weld state to 22.7%. After solid solution+aging, most of the δ ferrite in the joint weld structure was converted to austenite, whose grains were coarsened; a large number of diffuse distribution γ' phases were precipitated, and the tensile strength and yield strength of the welded joint increased from 639, 360 MPa at solid solution state to 1 019, 662 MPa; the average hardness reached 200% of solid solution state, but the elongation after the fracture was reduced to 17.1%.
  • Review
    ZHOU Qiong, WEN Yadong, ZHANG Ergeng, HUANG Biao, LI Yaodong, LIANG Dandan, CHEN Qiang
    Materials For Mechanical Engineering. 2022, 46(10): 1-7. https://doi.org/10.11973/jxgccl202210001
    Diamond-like carbon (DLC) is a kind of metastable amorphous material containing diamond structure (sp3 hybrid bond) and graphite structure (sp2 hybrid bond), and has excellent characteristics such as high hardness, corrosion resistance, low friction coefficient, wear resistance. However, DLC also has problems such as large internal stress, poor thermal stability and sensitive tribological behavior caused by different preparation process and deposition parameters, which greatly limits its industrial application. The affecting factors of DLC film tribology properties are summarized from two aspects of the intrinsic factors and external factors. The improvements of DLC film tribology properties are discussed from heterogeneous elements doping and surface texture. The research trend of tribological properties of DLC film is prospected.
  • Failure Analysis
    LAN Haotian, QIN Song, XU Xiaohan, SONG Yifeng, YUE Chongxiang
    Materials For Mechanical Engineering. 2022, 46(10): 113-118. https://doi.org/10.11973/jxgccl202210019
    The tin plate for easy-opening lid produced by a steel factory cracked at the rivet during the lid making process, and the cracking rate was about 0.08%, which was lower than the customer's expected quality requirements. The cracking reasons were analyzed by chemical composition analysis, mechanical property testing, microstructure observation and inclusion analysis, and the improvements were suggested. The results show that the ductile fracture occurred on the rivets of easy-opening lids. The presence of large Al2O3 and CaO inclusions at the edge of the rivets and the obvious thickness thinning were the direct and indirect causes of the lidding cracking of the tin plate, respectively. After the ladle refining furnace (LF) refining process during the smelting process changed to the molten steel vacuum circulating degassing (RH) refining process, the number of inclusions per square millimeter in the finished tin plate was 4.7, and the maximum size was 15.5 μm, which were significantly lower than the 49.8 per square millimeter and 38.9 μm before the process improvement, and no cluster large inclusions were found, indicating that the RH refining process had a better control effect on the inclusions. The chemical composition, hardness, tensile properties and microstructure with the RH refining process were all met the requirements for easy-opening lids, and the cracking rate of lidding was reduced to less than 0.01%.
  • Testing & Research
    WANG Dan, ZHONG Qingdong, YANG Jian, ZHANG Shujian
    Materials For Mechanical Engineering. 2022, 46(9): 16-23. https://doi.org/10.11973/jxgccl202209003
    Three test steels with composition (mass fraction/%) of 0.35C,0.9Mn, 3.5Cr, 0.6Si, 0.3V, 0.05Ti (namely N1), 0.35C, 1.2Mn, 2.0Cr, 0.8Si, 0.4V, 0.11Ti (namely N2) and 0.40C,0.6Mn, 3.5Cr, 0.8Si, 0.1V, 0.23Ti (namely N3) were designed based on 40Cr steel composition, and the microstructure, electrochemical properties and corrosion resistance in 3.5wt% NaCl solution of test steels were studied. The results show that N3 test steel had the smallest grain size and the narrowest martensite lath bundle, followed by N1 test steel and N2 test steel. N1 test steel had the highest open circuit potential, the highest free-corrosion potential, the lowest free-corrosion current density, the largest absolute value of the maximum phase angle, and the largest radius of the capacitive arc. After soaking in NaCl solution for 24 h, localized pitting corrosion occurred on the surface of N1 and N3 test steel, while uniform corrosion occurred on N2 test steel. N1 test steel had high chromium content, moderate grain size, the highest surface corrosion product compactness and the best corrosion resistance.
  • Testing & Research
    WANG Lei, LIU Yang, SONG Xiu, SUN Shixin, LIU Shizhong, LI Jiarong
    Materials For Mechanical Engineering. 2022, 46(8): 15-21,27. https://doi.org/10.11973/jxgccl202208003
    Based on the fourth generation nickel-based single crystal superalloy DD15, single crystal superalloys were prepared by adjusting its Re content (mass fraction) to 5%, 6% and 7%, respectively. The effects of Re content on the solidification microstructure characteristic and element distribution of the alloy were studied. The results show that with increasing Re content, the precipitation temperature and dissolution temperature of γ' phase of the alloy increased, while the solidus temperature decreased slightly and the liquidus temperature had no obvious change. With increasing Re content, both the primary and secondary dendrite spacings increased, the content of (γSymbolk@@γ') eutectic microstructure increased, while the size and volume fraction of γ' phase decreased. Increase in Re content could decrease the segregation degree of negative segregation elements such as Re, W, Mo, Cr and Co in the alloy structure, but increase the segregation degree of the positive segregation element Ta.
  • Testing & Research
    CAI Xiaotao, QI Yanchang, WEI Jinshan, MA Chengyong
    Materials For Mechanical Engineering. 2022, 46(8): 33-39. https://doi.org/10.11973/jxgccl202208006
    During the construction of large liquefied natural gas storage tanks, spot-like and floccus unknown images were found on the radiographic-inspection film of the 06Ni9DR steel weld by the ENiCrMo-6 nickel-based alloy electrode. The cause of unknown images was analyzed, and the effect of unknown images on the mechanical properties of weld was studied by microstructure observation, energy spectra analysis, hardness test, cryogenic impact tests, and thermodynamic calculations. The results show that the spot-like and floccus images were mainly caused by large-sized tungsten-rich inclusions and niobium-molybdenum-rich precipitate clusters. The average hardness of areas of inclusions and precipitate clusters were 456, 288 HV, respectively, which were both higher than that of the substrate; the tungsten-rich particles and precipitate clusters had a negative effect on the stability of tensile strength and cryogenic impact toughness of the weld joints. The quantity of unknown images decreased significantly after replacing the electrode. The unknown images were related to uneven mixing of coating components or uneven particle size of the flux during the production of nickel-based alloy electrodes, resulting in the abnormal enrichment of alloy elements in the weld metal.
  • Testing & Research
    LI Cong, DING Zhili, HUANG Can, ZHOU Libo, CHEN Wei, CHEN Jian
    Materials For Mechanical Engineering. 2023, 47(1): 48-55,64. https://doi.org/10.11973/jxgccl202301007
    SP-700 titanium alloy was treated by solid solution in β phase region at 1 000℃ for 15 min, and then was cooled to (α+β) phase region for solid solution at different temperatures (650-900℃) for different times (3-10 min) or was treated by single stage aging and or double stage aging including 280℃ low temperature pre-aging and the second aging at different temperatures (370-650℃) for different times (15, 90 min). The microstructure and properties of the alloy under different processes were studied. The results show that the volume fraction of α phase in the alloy after 850℃ solid solution increased with the solid solution time; when the solid solution time was 5 min, the alloy had good strong plastic matching. Under solid solution time of 5 min, the volume fraction of α phase decreased with increasing solid solution temperature; when the solid solution temperature was 650℃, the alloy had good strong-plastic matching. After β phase region solid solution and single/double stage aging, the alloy was basically composed of β grain, α phase and acicular martensite. After single stage aging at aging temperature of 650℃ for 90 min or double stage aging at aging temperature of 650℃ for 15 min, the alloy showed good strong-plastic matching.
  • Review
    YANG Zonghui, SHEN Yifu, ZHANG Xu, LI Xiaoquan
    Materials For Mechanical Engineering. 2022, 46(12): 9-17. https://doi.org/10.11973/jxgccl202212002
    In nuclear fusion reactors, joining the plasma material tungsten and structural material low activation steel is a key issue to manufacture tungsten/steel composite structures that can meet extremely harsh working requirements. The difficulties of joining tungsten and steel are introduced, and the research status of bonding technologies of tungsten/steel composite structure, thermal stress and stress reduction method of the joint, and mechanical properties of the joint are described in detail. It is pointed out that improving bonding technology and processes on the basis of systematic test and analysis of thermal conductivity, thermal fatigue resistance and working reliability in high temperature and strong radiation environment, standardizing test methods, and determining the priority and requirements of the key performance of tungsten/steel composite structures are the development direction of the research on tungsten/steel composite structure bonding technologies for nuclear fusion reactors.
  • Testing & Research
    ZHANG Wei, JIANG Shengqiang, DUAN Chunyan, XIAO Xiangwu, TAN Yuanqiang
    Materials For Mechanical Engineering. 2023, 47(2): 21-25. https://doi.org/10.11973/jxgccl202302004
    IN718 nickel-based superalloy powder was spreaded at different scraper moving speeds (28.23, 63.55, 91.11, 125.25 mm·s-1), and the powder layer thickness was 0.3, 0.5, 0.7, 0.9 mm, respectively. The powder at different positions with the same volume of the powder layer was collected by a self-made device for testing powder uniformity and weighted. The influence of the scraper moving speed and the powder layer thickness on the powder spreading uniformity was studied by calculating mass standard deviation. The results show that the mass standard deviation of the powder layer increased with the increase of the scraper moving speed or the powder layer thickness, indicating the powder spreading uniformity became worse; the scraper moving speed had a greater effect on the powder spreading uniformity. The optimal process parameter combination to obtain the best powder spreading uniformity was listed as follows:scraper moving speed of 28.23 mm·s-1 and powder layer thickness of 0.3 mm.
  • Testing & Research
    HOU Huaishu, LI Jinhao, LU Ding, XIA Shuaijun, XIN Jianlong
    Materials For Mechanical Engineering. 2022, 46(8): 46-52. https://doi.org/10.11973/jxgccl202208008
    Grain size of base metal and weld of thin-walled 304L austenitic stainless steel welded tube after solid solution treatment at different temperatures (800-1 350℃) were counted by tests. The ultrasonic signals of base metal and weld were triple wavelet decomposed by ultrasonic attenuation method based on continuous wavelet transform to extract the characteristic energy. The feasibility of ultrasonic attenuation method to evaluate grain size of welded tube was studied. The results show that with increasing solid solution temperature, the base metal grain size and the corresponding ultrasonic characteristic energy decreased; in the actual detection, the relative characteristic energy threshold of ultrasonic signals could be set between 600 and 1 000; in this case, the grain size was between 7 and 8.5, and the grain size was qualified. With increasing solid solution temperature, the grain size of weld increased, and characteristic energy first increased and then decreased and then increased, and reached the maximum at about 1 050℃; in the actual detection, the relative characteristic energy threshold of ultrasonic signals could be set between 140 and 180; in this case, the grain size was 8.5-9, and the grain size was qualified. Ultrasonic attenuation method could be used to quickly and nondestructively evaluate the grain size of thin-walled 304L austenitic stainless steel welded tube.
  • Failure Analysis
    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
    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.
  • Testing & Research
    YANG Yong, WANG Jiaxin, WANG Bin, YAO Yulong
    Materials For Mechanical Engineering. 2022, 46(8): 53-57,67. https://doi.org/10.11973/jxgccl202208009
    The microstructure, hardness and surface temperature at the end of production of phosphorus copper ball with diameter of 25 mm by rolling and upsetting processes were comparably studied. The results show that compared with the rolling process, the surface of the phosphorus copper ball by upsetting process was smooth; the grain was obviously refined, and grain boundary was clear; the element distribution was uniform; the grains were mainly equiaxed and the number of columnar grains was relatively small. The maximum surface temperatures of the phosphorus copper ball far away from and near the outlet tank at the end of production by upsetting process were lower than those by the rolling process. The heart hardness of the phosphorus copper ball by upsetting process was obviously higher than that by the rolling process, and the surface hardness fluctuated less. Compared with the rolling process, the phosphorus copper ball by the upsetting process had the technical advantages of good quality, environmental protection and low energy consumption.
  • Material Properties & Application
    CHEN Lei, SU Bin, SUN Qiaoyan, ZHU Bo, BAI Xinfang
    Materials For Mechanical Engineering. 2022, 46(8): 94-99. https://doi.org/10.11973/jxgccl202208015
    Zr-4 alloy was heated to 1 000℃ for 5 min, and then was cooled to room temperature at cooling rate of 200, 20, 2, 0.2, 0.02℃·s-1. The effects of quenching cooling rates on microstructure and corrosion behavior of the alloy in 360℃/18.6 MPa water were studied. The results show that the average width of α phase plate in alloy increased from 1.4 μm to 28.0 μm, and the average particle size of the second phase particles increased from 38 nm to 580 nm with decreasing cooling rate from 200℃·s-1 to 0.02℃·s-1. The second phase particles were mainly distributed in grain boundaries of α phase plate at cooling rate of 200, 20, 2℃·s-1, and were distributed both inside the crystal and grain boundaries at cooling rate of 0.2, 0.02℃·s-1. When the cooling rate decreased from 200℃·s-1 to 0.2℃·s-1, the increase of the second phase particles helped to release the compressive stress in the oxide film and improved the corrosion resistance of the alloy. A number of microcracks initiated around the second phase particles, and the corrosion resistance decreased at the cooling rate of 0.02℃·s-1. The corrosion resistance was the best at the cooling rate of 0.2℃·s-1, and the ZrO2 grains in the oxide film were mainly columnar crystals with dense structure.
  • New Materials & Technology
    ZHANG Jin, HUANG Yuntao, YUE Xinyan, ZHANG Cuiping, RU Hongqiang
    Materials For Mechanical Engineering. 2023, 47(1): 70-75. https://doi.org/10.11973/jxgccl202301010
    Taking Al2O3 and TiC powders as raw materials, TiC-Al2O3 conductive ceramic composites were prepared by pressureless sintering technique. The effects of TiC content on the microstructure and properties of ceramic composites were investigated. The results show that TiC-Al2O3 conductive ceramic composites mainly consisted of Al2O3 phase and TiC phase. With increasing content of TiC, the relative density decreased, and the open porosity increased; when the TiC volume fraction was 30%, the ceramic composites had the maximum relative density of 95.5% and the minimum open porosity of 3.0%. The conductive phase TiC in ceramic composites was connected as a network structure; with increasing TiC content, the network structure formed by TiC became more complete,the hardness of ceramic composites increased first and then decreased, the resistivity and fracture toughness decreased, and the bending strength increased. When the TiC volume fraction was 45%, the bending strength was the highest and the conductivity was the lowest, which were 361 MPa, 6.95×10-6 Ω·m, respectively.
  • Testing & Research
    YU Qingping, ZHANG Guangsheng, XIA Liansen, FANG Huimin
    Materials For Mechanical Engineering. 2023, 47(4): 18-22,32. https://doi.org/10.11973/jxgccl202304004
    Fe-2%Cu-0.4%C iron-based powder metallurgy material was boronized at 950 ℃ for 5 h by solid powder boronizing method with a boronizing agent containing CeO2. The effects of CeO2 addition (0,2%, 4%, mass fraction) on the microstructure and friction and wear properties of the boronizing layer were studied. The results show that the boronizing layer with different addition amounts of CeO2 had a single Fe2B phase. With the increase of CeO2 addition, the surface roughness of the boronizing layer increased, and the thickness, hardness and wear resistance increased first and then decreased. When the mass fraction of CeO2 was 2%, the thickness and hardness of the boronizing layer were the largest, about 144 μm and 58.0 HRC, respectively. At this time, the surface integrity of the boronizing layer was relatively good, the amount of wear was the smallest, about 0.008 g, and the wear resistance was the best.
  • Testing & Research
    SUN Jing, WU Jun, ZHU Zhongliang, YANG Shuai, LI Fuzhong, YAN Dapeng, ZHAO Weigang, WANG Lianfeng
    Materials For Mechanical Engineering. 2022, 46(8): 68-74. https://doi.org/10.11973/jxgccl202208011
    The Al4SiC4/AlSi10Mg composite was fabricated by selective laser melting process with ball-milling mixed powders of SiC and AlSi10Mg. The effect of laser energy density (76.2, 80.0, 91.5 J·mm-3) on the microstructure of the composite was explored. The results show that a sub-micro scale Al4SiC4 reinforcing phase was produced by the interaction between the laser beam and the composite powder. The phase exhibited needle-like morphology and distributed in clusters or parallel arrangement around the original SiC particles. With the increase of the laser energy density, the Marangoni convection intensified in the melt pool, promoting the generation of Al4SiC4; so the original SiC reinforcements were transformed into Al4SiC4 grandually. In addition, the morphology of the Al4SiC4 phase changed from needle-like to cluster-like or parallel-arranged sheet-like morphology.
  • Testing & Research
    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
    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.
  • Review
    SUN Hui, WU Huibin, XU Yaowen
    Materials For Mechanical Engineering. 2023, 47(1): 11-18. https://doi.org/10.11973/jxgccl202301002
    High entropy alloys have great development potential in industry with the advantages of high strength,high hardness and corrosion resistance. The phases of typical high entropy alloys include solid solution phases, such as face-centered cubic (FCC) phase,body-centered cubic (BCC) phase and hexagonal close-packed (HCP) phase, and amorphous phases. The unique phase structure has an important influence on mechanical behaviors of high entropy alloys. The mechanical behaviors of high entropy alloys with different phase structures are reviewed, and the research progress on phase structure prediction methods of typical high entropy alloys, including empirical rule, CALPHAD method, first-principles calculation and machine learning method, are summarized. The future development direction of phase structure prediction of high entropy alloys is given.
  • Testing & Research
    LI Haitao, CHENG Jingtian, FAN Shuaiqi, XU Jinfu
    Materials For Mechanical Engineering. 2022, 46(8): 83-88. https://doi.org/10.11973/jxgccl202208013
    The carbon-boron binary alloying layer was prepared on the surface of 45 steel by laser alloying process. The process was optimized by orthogonal test, and the microstructure and properties of alloying layer under the optimal process were studied. The results show that the optimal process obtained by orthogonal test included laser power of 2.2 kW, scanning speed of 500 mm·min-1, overlap rate of 40%, and mass ratio of boron and carbon powder of 6.0:3.5. The alloying layer prepared under the optimal process was composed of Fe3C, Fe2B, FeB and γ- (Fe, C) phases, and consisted of alloying zone and heat affected zone. The microstructure of alloying zone was mainly columnar and cellular crystals, with a thickness of about 600 μm and an average hardness of 879 HV. The microstructure of heat affected zone was composed of acicular martensite and retained austenite, and its grains gradually became smaller from the matrix to the alloying zone. The thickness of heat affected zone was about 450 μm, and the hardness presented gradient distribution between 220-768 HV; The friction coefficient of alloying layer sample was about 0.466 6 and the wear rate was 0.455 3×10-14 m3·N-1·m-1; compared with 45 steel matrix sample, the wear resistance was greatly improved.
  • Material Properties & Application
    ZOU Chunlei, YU Hang, REN Huiyuan, GU Jinbo, ZHOU Jian, CHI Hongxiao
    Materials For Mechanical Engineering. 2022, 46(9): 46-51. https://doi.org/10.11973/jxgccl202209008
    Annealed Cr12Mo1V1 die steel was treated by single quenching+tempering, double-quenching+tempering, single quenching+cryogenic treatment+tempering and double-quenching+cryogenic treatment+tempering processes, respectively. The single quenching process was 1 030 ℃×0.5 h oil quenching. The double-quenching process was 1 050 ℃×0.5 h oil quenching+1 030 ℃×0.5 h oil quenching. The cryogenic treatment was -60 ℃×1 h+-120 ℃×1 h. The effects of double-quenching+cryogenic treatment on the microstructure and mechanical properties of the test steel were studied contrastively. The results show that comparing with the single quenching+tempering process, the double-quenching+tempering process could improve the distribution uniformity of eutectic carbides, and make the carbides be spherical. The addition of cryogenic treatment had little effect on the improvement of the morphology and uniformity of eutectic carbides, but reduced the residual austenite content. The hardness of the test steel after the double-quenching+tempering treatment was similar to that after the single quenching+tempering treatment, while the impact absorption energy and bending strength increased by 22% and 12%, respectively. The addition of cryogenic treatment had little effect on the hardness, impact toughness and flexural strength of the test steel.
  • Testing & Research
    LI Zhen, YANG Li, SHEN Tong, FENG Lingxiao
    Materials For Mechanical Engineering. 2022, 46(9): 11-15. https://doi.org/10.11973/jxgccl202209002
    Two-stage vacuum nitriding process was used to modify the surface of quenched and tempered PCrNi3Mo steel. Under the condition of the same nitriding temperature and nitrogen potential, the microstructure, phase composition, hardness and wear resistance of the surface layer of the test steel were studied under the conditions of strong infiltration for 6 h and diffusion for 6 h, and compared with those by strong infiltration for 4 h and diffusion for 8 h. The results show that after nitriding, the phase of the test steel surface layer was ε-Fe2-3N phase. Under two nitriding time conditions, the thickness of nitrided layer was about 0.6, 0.7 mm, and the surface hardness was 660.3, 581.3 HV, respectively, higher than 360 HV of substrate. Under the former nitriding time condition, the compound layer in the nitriding layer had poor compactness and a great number of micropores; the hardness transition of the nitriding layer was good, and the hardness was relatively high at the distance from the surface of greater than 0.3 mm; the friction coefficient and wear amount of the nitrided layer were relatively low, and the furrow on the wear surface was shallow, indicating the wear resistance was relatively good.
  • Material Properties & Application
    SHI Kunyu, ZHUANG Chenqi, WU Weijin, ZHANG Bo, YU Chuanhao
    Materials For Mechanical Engineering. 2022, 46(9): 34-39. https://doi.org/10.11973/jxgccl202209006
    NbTiN2 coating was prepared on TC4 alloy surface by dual cathode plasma sputtering deposition. The phase composition, microstructure, hardness, adhesion to matrix and friction and wear properties of the coating were studied. The results show that the NbTiN2 coating had strong (220) preferred orientation. The coating had good surface quality, no obvious defects and a thickness of about 10 μm. The average hardness of the coating was 2 478.46 HV, about 6 times that of the matrix, and the critical load of coating in scratch test was 68.5 N, indicating that the coating was well combined with the matrix. The friction coefficient of the coating was lower than that of the matrix under the load of 2-5 N at room temperature; the wear scar was narrower than that of the matrix, and the wear rate of the coating was one order of magnitude lower than that of the matrix; the main wear mechanism of the coating was fatigue wear. At 500 ℃, the friction coefficient was higher than that at room temperature, and the wear scar of the coating was narrower and shallower; the wear rate was lower, and the wear mechanism was adhesive wear and oxidation wear, indicating the coating had better wear resistance.
  • Testing & Research
    WANG Zixuan, XUE Rong, ZHU Congzhen, LIN Haoran, WANG Jiping
    Materials For Mechanical Engineering. 2022, 46(10): 21-26. https://doi.org/10.11973/jxgccl202210004
    Taking two kinds of constituent siliconized graphite composites prepared by reactive molten infiltration with different isostatic pressures (40 MPa and 70 MPa) and commercially purchased Russian-made siliconized graphite composites as research objects, the phase composition, microstructure and friction and wear properties under water lubrication conditions of three kinds of constituent siliconized graphite composites were studied. The results show that the phases of the siliconized graphite composites were composed of carbon phase, silicon carbide phase and silicon phase, which were distributed as a three-dimensional network embedded. When the carbon phase content was relatively low and the silicon graphite content was relatively high, friction coefficient of siliconized graphite composites increased with the load; when the carbon phase content was relatively high and silicon carbide content was relatively low, the friction coefficient increased first and then decreased with the load. The wear loss of different constituent siliconized graphite composites was extremely low, and the siliconized graphite composites had excellent wear resistance. The wear mechanism was mainly abrasive wear.
  • Review
    SUN Ruting, MA Ran
    Materials For Mechanical Engineering. 2022, 46(11): 1-8. https://doi.org/10.11973/jxgccl202211001
    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.
  • New Materials & Technology
    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
    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.