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  • MENG Xianming, ZHONG Zheng, CHENG Congqian, CAO Tieshan, ZHAO Jie, HUANG Yafeng, WU Yao
    Materials For Mechanical Engineering. 2020, 44(12): 85-90,96. https://doi.org/10.11973/jxgccl202012016
    The progressive failure model of fiber reinforced plastics and the continuous damage model of composite laminate of the Ls-Dyna software were applied to simulate the mechanical response and damage modes of carbon fiber reinforced plastic laminates under in-plane shear loads, with the mechanical parameters obtained by quasi-static uniaxial tensile and in-plane shear tests. The applicability of the two models was compared. The results show that in the initial linear elastic stage during in-plane shearing, the two models could simulate the mechanical characteristics of the carbon fiber reinforced plastic laminates. As the load continued to increase, the load-displacement simulation curve obtained by the progressive failure model still rose linearly, and dropped rapidly after reaching the load peak; the simulation curve had a large deviation from the test curve. When the material was damaged, because of the introduction of damage parameters, the load-displacement simulation curve obtained by the continuous damage model was nonlinear, which was in good agreement with the test curve.
  • ZHANG Min, TONG Xiongwei, LI Jie, XU Shuai, JIA Fang
    Materials For Mechanical Engineering. 2021, 45(1): 34-40. https://doi.org/10.11973/jxgccl202101006
    Microstructure, mechanical properties and corrosion resistance of 25Cr2Ni4MoV steel welded joint were compared and studied under conditions of pre-welding and post-welding quenching and tempering treatments. The quenching and tempering process was oil quenching at 920 ℃ for 1 h and tempering at 580 ℃ for 2 h. The welding process was manual electrode arc welding. The results show that by pre-welding quenching and tempering, the microstructure of the joint weld zone consisted of lath martensite, network δ-ferrite and M23C6 carbide. After the post-welding quenching and tempering, the δ-ferrite in the weld was dissolved, and the lath martensite, tempered sorbite and M23C6 carbide were formed. Under the post-welding quenching and tempering condition, the lath martensite in the weld was small and uniform, and the M23C6 carbide distributed in granular shapes on original austenite grain boundaries and martensite lath grain boundaries; the strength, impact toughness and corrosion resistance were better than those by the pre-welding quenching and tempering treatment.
  • HE Jie, MA Shizhou, ZHANG Xinggao, GAI Xiqiang, CHEN Houhe, ZHANG Kaichuang
    Materials For Mechanical Engineering. 2020, 44(11): 46-52,58. https://doi.org/10.11973/jxgccl202011009
    Additive manufacturing is an important development direction of advanced manufacturing technique for metal parts, but the metal powder for additive manufacturing has some problems such as insufficient research and development, weak stability and incomplete standards, which seriously restrict its development. The basic principles of common spherical metal powder preparation techniques including centrifugal atomization method, two-stream atomization method and spheroidization method are summarized, and their advantages, disadvantages and development status are introduced. It is proposed that the development of domestic additive manufacturing powder preparation technique can start from two aspects. One is to carry out process and equipment improvement and standardization research on traditional methods, and build automated factories; the other is to strengthen the research on basic theories of powdering and explore new processes.
  • ZHANG Tengyu, HAN Tao, WU Shuquan, JIANG Feng, ZHANG Zhibo, JIANG Shikai
    Materials For Mechanical Engineering. 2021, 45(2): 61-65. https://doi.org/10.11973/jxgccl202102011
    The hardness of the 1Cr5Mo steel fastening nut of a supercritical unit steam turbine in a thermal power plant was reduced significantly after service. Aiming at this phenomenon, the aging tests (equivalent to service) of the 1Cr5Mo steel nut were carried out at 566 ℃. The effect of aging time on the microstructure and mechanical properties was studied, and the microstructure and performance were compared with those of the nut served at 566 ℃ for 105 h. The results show that at temperatures not higher than 566 ℃, the microstructure of the 1Cr5Mo steel nut changed slowly; the microstructure was still martensite and carbide after aging for 2 880 h. But the microstructure changed to tempered sorbite after service for 105 h. With the extension of the aging/service time, the carbides migrated and concentrated from the inside grain to the grain boundary, and became obviously coarsened. The deterioration of the structure led to the reduction of the hardness, strength, and impact energy of the nut.
  • LIU Yuning, WANG Yunpeng, ZHU Rufei, WANG Hu, BAI Yike, LOU Huafen
    Materials For Mechanical Engineering. 2021, 45(1): 1-7. https://doi.org/10.11973/jxgccl202101001
    Development of high speed and high performance of mechanical equipments requires higher strength and better wear resistance of wear-resistant copper alloys. Although performance of traditional aluminum bronze series, manganese brass series and lead brass series alloys has been improved, their application scope is limited by various factors, such as material characteristics, processing technology and environmental protection, respectively. The application status and research progress of five typical wear-resistant copper alloys with high application values including Cu-Ni-Sn series, Cu-Al2O3 series, Cu-Nb series, Cu-C series (including copper/graphite, copper/graphene and copper/carbon nanotubes) and complex brass are described from preparation process, properties and application field. The problems in their development and application are analyzed, and their development prospect is also discussed.
  • ZHU Mingjun, ZHANG Ganghua, LI Shasha, ZENG Tao
    Materials For Mechanical Engineering. 2021, 45(6): 79-84,93. https://doi.org/10.11973/jxgccl202106014
    Ferroelectric materials have unique photovoltaic properties due to their polarized electric field, and are widely used in many fields, especially in photovoltaic power generation. The generation mechanism of internal electric field (photovoltaic mechanism) in ferroelectric materials, and the effects of electric field regulation mechanism on photovoltaic properties of ferroelectric materials are reviewed from aspects of the preparation of narrow band gap ferroelectric materials, enhancing visible light absorption by self-doping of oxygen deficiency constructing composite heterojunction, preparing multipole axial molecular ferroelectrics, and regulating the domain orientation and distribution in ferroelectric materials by external polarization field. The research direction of improving photovoltaic performance by regulating internal electric field is pointed out.
  • ZHENG Cheng, LU Qi, LI Hongtao
    Materials For Mechanical Engineering. 2021, 45(1): 41-45. https://doi.org/10.11973/jxgccl202101007
    Two types of unclosed staircase chart were cited, and reasonable assumptions were made on the test results that may appear during the staircase fatigue test. The effect of test data closed or not on the fatigue strength was analyzed when the fatigue strength was statistically estimated by the staircase method. The results show that when the last-level stress in the staircase chart of unclosed test data was lower than the first effective stress, the statistically estimated fatigue strength after subsequent supplementary of hypothetical staircase chart was also lower than the statistically estimated fatigue strength from the original unclosed fatigue test staircase chart. When the last-level stress of the staircase chart of unclosed test data was higher than the first effective stress, the statistically estimated fatigue strength after subsequent supplementary of hypothetical staircase chart was also higher than the statistically estimated fatigue strength from the original unclosed fatigue test staircase chart. Even if test data was not closed, the fatigue strength statistically estimated from failure events and non-failure events may be equal.
  • HU Rudan, SUN Jingwen, LIU Yifan, QIAN Xingyue, ZHANG Litong, ZHU Junwu
    Materials For Mechanical Engineering. 2021, 45(1): 20-27. https://doi.org/10.11973/jxgccl202101004
    The cobalt-doped manganese oxide for aqueous zinc-ion battery cathode material was prepared by solvothermal, hydrolyzing and annealing with cobalt nitrate and manganese nitrate as raw materials. The microstructure and electrochemical performance of cobalt-doped manganese oxide was investigated. The results show that the prepared cobalt-doped manganese oxide h-CoMn3.2Ox had a hierarchical yolk-shell structure, and the porous shell surface was decorated with petal-like nanosheets with radial dimension of more than 100 nm. Both of the shell and nanosheets were composed of primary nanoparticles with average size of 5 nm. Cobalt-doping endowed manganese oxides with small size and delicate structure. h-CoMn3.2Ox had the manganosite MnO crystal structure. Compared with monometallic manganese oxide, h-CoMn3.2Ox exhibited relatively large specific surface areas and specific capacities, and had good cyclic stability. The energy-storage behavior of h-CoMn3.2Ox was attributed to sequent co-insertion of H+ and Zn2+.
  • RAN Xu, JIANG Mingkun, HAN Ying
    Materials For Mechanical Engineering. 2019, 43(8): 41-45,74. https://doi.org/10.11973/jxgccl201908008
    Microstructure and mechanical properties of imported EA4T steel axle for high-speed railway were investigated, and uniformity of the microstructure and mechanical properties was analyzed. The results show that non-metallic inclusions, including CaS, Al2O3 and a small amount of silicate, were found in the axle, and the number of inclusions increased from the surface to the core. The microstructures at different positions in the axle all consisted of tempered martensite, bainite and a small amount of proeutectoid ferrite; the size and number of the proeutectoid ferrite increased from the surface to the core. The microstructure was uneven. The tensile properties and hardness of the axle met the standard requirements. The tensile strength at the core was obviously lower due to higher content of the proeutectoid ferrite. Banded structure was observed in the longitudinal direction of the axle, and therefore the transverse impact toughness was relatively low. The tensile fracture of the axle sample showed relatively small and deep dimples, indicating good plasticity; the tensile fracture mode was ductile fracture. The impact fracture had obvious river patterns and dimples, and the fracture mode was brittle-ductile mixed fracture.
  • LIU Xuan, YANG Rui
    Materials For Mechanical Engineering. 2020, 44(9): 1-10,71. https://doi.org/10.11973/jxgccl202009001
    Rubber is an important material in mechanical engineering industries. Rubber sealing materials play a key role in many mechanical instruments, and aging of rubber seals may cause unpredictable failures or even huge losses. Hence, aging research of rubber sealing materials are attracting great attentions. The aging research progress of rubber sealing materials is reviewed, including aging behavior and mechanism, effects of stress and chemical media on aging, lifetime evaluation indexes and prediction, and aging analysis techniques. The existing problems in aging research of rubber sealing materials are discussed. Future research perspectives are proposed, including studies on accelerated aging methods, aging mechanism, correlation between accelerated aging and natural aging of rubber seals, and so on.
  • GUO Laijia, GU Shuchao, DUAN Peng, DING Xianfei, WANG Song, LIU Yuzhe
    Materials For Mechanical Engineering. 2020, 44(9): 56-61,66. https://doi.org/10.11973/jxgccl202009010
    T23, T91 and TP347H steel tube samples were taken at different positions of the final boiler reheater of a 600 MW supercritical boiler in service of about 7.8×104 h. Microstructures and tensile properties at room temperature and elevated temperature of these samples were analyzed, and the deterioration degrees of the microstructure and tensile properties were studied and compared. The results show that the microstructures of T23, TP347H, T91 steel tube samples presented obvious degradation characteristics with M6C carbide,M23C6 carbide and Laves phase precipitated on grain boundaries, and the microstructure degradation grades were grade 4, grade 3.5 and grade 4, respectively. The tensile properties of T23 steel tube samples at room temperature and elevated temperature showed serious deterioration tendency, and did not meet the standard requirements. The tensile strength of T91 steel tube samples decreased significantly. The tensile properties of TP347H steel tube samples met the standard requirements. Under elevated temperature conditions, TP347H steel tube samples had good strength and structural safety, but ductility was significantly reduced.
  • LI Chunlai, QIN Qingbin, WU Shengchuan, ZHANG Xiaojun, LIANG Tao, LIU Yang
    Materials For Mechanical Engineering. 2020, 44(7): 8-11,17. https://doi.org/10.11973/jxgccl202007002
    G20Mn5 cast steel plates with thickness of 8 mm were connected by metal active gas (MAG) arc butt welding with one-side two-pass welding method. The microstructure, hardness, tensile property and fatigue property of the joint were studied. The results show that the joint had the good surface and no obvious welding defects were found. The joint consisted of base metal, heat affected zone and weld zone, and the heat affected zone was subdivided into incomplete normalized zone, normalized zone and overheated zone. From the base metal to the weld center, the hardness of the joint increased first and then decreased. The fusion zone had the highest hardness of about 70 HRB, and the hardness of the weld was 55-60 HRB, which was a little higher than that of the base metal. The tensile strength of the joint was obviously higher than that of the base metal, while the percentage elongation after fracture was lower than that of the base metal. The high cycle fatigue strength of the joint was equivalent to that of the base metal, and both fractured at heat affected zone. The properties of the joint met the design requirements.
  • ZHENG Yangfan, LIANG Feng, TIAN Liang, WANG Junkai, ZHANG Haijun
    Materials For Mechanical Engineering. 2018, 42(4): 27-30,52. https://doi.org/10.11973/jxgccl201804006
    Bamboo-like N-doped carbon nanotubes were prepared by catalytic pyrolysis method with melamine as raw material and FeCl2·6H2O as catalyst precursor. The effects of the reaction temperature and FeCl2·6H2O content on the phase composition and microstructure of the product were investigated. The results show that at the reaction temperatures of 650-800℃, the yield and length to diameter ratio of the carbon nanotubes first increased and then decreased with the increase of reaction temperature. The optimal reaction temperature was 750℃. When pyrolyzing at 750℃, the yield and length to diameter ratio of the carbon nanotubes first increased and then decreased with the increase of FeCl2·6H2O content and the optimal content was 0.50wt% of melamine. The obtained carbon nanotubes under this condition had diameters of 40-50 nm and lengths of 10-15 μm, the N-doping amount in the carbon nanotubes was about 3.42at%, in which the fraction of graphitic N was about 43.1mol%.
  • ZHANG Qinglian, LIU Cheng, GUO Jinbao
    Materials For Mechanical Engineering. 2021, 45(2): 66-70,77. https://doi.org/10.11973/jxgccl202102012
    The microstructure, tensile properties and corrosion resistance of a new BGNDMA low-alloy steel were studied and compared with the properties of 09CrCuSb steel and 2205 duplex stainless steel. The results show that the microstructure of the BGNDMA steel was ferrite and pearlite, and the tensile properties were better than those of 09CrCuSb steel. When immersed in 70 ℃, 50wt% H2SO4 solution for 24 h, the corrosion rates of most samples were not higher than 80 g·m-2·h-1, and the statistical average value was about 36.367 g·m-2·h-1, indicating the excellent resistance to sulfuric acid corrosion. In the dead green liquor and the industrial flue gas dew point (not higher than 80 ℃) corrosion environment, the BGNDMA steel underwent uniform corrosion, and 2205 duplex stainless steel underwent local corrosion such as pitting corrosion and crevice corrosion; BGNDMA steel was expected to replace 2205 duplex stainless steel in H2SO4-HCl mixed acid dew point corrosion environment. In an industrial flue gas dew point corrosion environment, the corrosion resistance of the hot rolled BGNDMA steel was better than that of the normalized steel.
  • XIONG Zhen, XU Chunxia, HU Rui, XIONG Le, MAITI Raman, MCQUADE Catherine
    Materials For Mechanical Engineering. 2021, 45(3): 1-5,51. https://doi.org/10.11973/jxgccl202103001
    Applying an external electromagnetic field is one of the ways to improve the tribological performance of the friction pair. From three aspects of the promotion of dislocation movement, the enhancement of the oxidation of the contact surface and the refinement and oxidation of the wear debris by the external electromagnetic field, the mechanism of the electromagnetic field improving the tribological performance of the metal material friction pair is reviewed. The influence of the external electromagnetic field type, the magnetic field strength, the magnetic field application direction, the magnetic field frequency, the magnitude and difference of magnetic permeability of the friction pair material and the size of the external magnetic particle on the friction and wear of the friction pair is discribed. The future research direction on the anti-friction of the electromagnetic field is pointed out.
  • LIU Quansheng, FAN Mengting, LUO Xinran
    Materials For Mechanical Engineering. 2021, 45(1): 66-72,79. https://doi.org/10.11973/jxgccl202101011
    6063 aluminum alloy was prepared by pressure forming process, and then was treated by solution at 535 ℃ and aging. The effects of solution time (15-120 min), aging temperature (160-200 ℃) and aging time (1-24 h) on the microstructure, tensile properties and hardness of the aluminum alloy were studied. The results show that with increasing solution time, the grain size of 6063 aluminum alloy increased, and the primary Mg2Si phase gradually disappeard and redissolved in the matrix; but the solution time had no effect on the content and morphology of α-Al8Fe2Si phase and β-Al5FeSi phase. After solution treatment, with increasing aging temperature or aging time, the number of second phase Mg2Si increased, but a higher temperature or a longer aging time resulted in the coarse of the Mg2Si phase. With increasing solution time, aging time or aging temperature, the strength and hardness of the alloy increased first and then decreased, and the precentage elongation after fracture decreased first and then increased. The appropriate solution and aging treatment system for 6063 aluminum alloy was 535 ℃×60 min + 180 ℃×7 h; at this time the Mg2Si phase precipitated in the alloy was the smallest and dispersed, and the alloy had the highest strength and hardness and the appropriate precentage elongation after fracture.
  • ZHANG Yan, WANG Zhenxu, XU Yu, SUN Chichi, XU Ruirui
    Materials For Mechanical Engineering. 2021, 45(1): 80-84. https://doi.org/10.11973/jxgccl202101013
    40Cr13 plastic die steel was quenched at different temperatures (960,1 020,1 080,1 140 ℃), and the effect of quenching temperature on microstructure and hardness was studied. The steel was tempered at 200 ℃,and the corrosion resistance of the steel was studied by immersion test and electrochemical test. The results show that the microstructure of the test steel after quenching at different temperatures was composed of quenched martensite, carbides and a small amount of retained austenite. The microstructure became coarse with increasing quenching temperature, and the number of carbides decreased. When the quenching temperature was 1 140 ℃, network carbides precipitated on austenite grain boundaries in the microstructure. The hardness of the test steel increased first and then decreased with increasing quenching temperature. When the quenching temperature increased from 960 ℃to 1 080 ℃, the corrosion rate of the test steel after tempering in FeCl3 solution decreased; the diameter and depth of pitting holes on the surface of the test steel decreased, and the number increased. The free-corrosion potential of the test steel in NaCl solution increased, and the free-corrosion current density decreased; the corrosion rate decreased and the corrosion tendency decreased. The optimum the quenching temperature was 1 020 ℃; at this point, the quenched martensite was relatively small, and the hardness was the largest; the corrosion resistance was relatively good.
  • GENG Ruwei, DU Jun, WEI Zhengying
    Materials For Mechanical Engineering. 2020, 44(12): 11-17. https://doi.org/10.11973/jxgccl202012002
    The wire and arc additive manufacturing (WAAM) has gained more and more attention because of its unique advantages in forming large-scale components, and has become one of the most widely used metal additive manufacturing technology. The development history of WAAM is described. The influence of process parameters on the morphology of deposited layer and the evolution mechanism of microstructure is analyzed from the perspective of “shape and property control”. The numerical simulation methods for residual stress and their advantages and disadvantages are discussed, and it is pointed out that the combination of computational fluid dynamics and finite element method is one future research trend. The common methods for controling the residual stress and deformation, as well as the problems and challenges in wire and arc additive manufacturing, are summarized.
  • WANG Zhengqiang, LI Wenge, DU Xu, ZHAO Yuantao
    Materials For Mechanical Engineering. 2020, 44(11): 35-40. https://doi.org/10.11973/jxgccl202011007
    Shaft parts are prone to failing such as friction, wear, corrosion and fatigue during service, which seriously affect the normal operation of construction machinery equipment. Laser cladding technique, as a common technical means for repairing and remanufacturing shaft parts, can effectively extend service lives of parts. The application of laser cladding technique in the remanufacturing of shaft parts is summarized. The influence of laser cladding process parameters (laser power, cladding speed, overlap rate and powder feeding amount) and cladding material selection on the repairing performance of shaft parts and the auxiliary application of simulation software are focused on. The development trend of laser cladding remanufacturing technique is prospected.
  • Testing & Research
    MA Yunhai, WANG Yanfeng, ZHAO Shuangqun, WANG Miaomiao
    Materials For Mechanical Engineering. 2022, 46(2): 48-57. https://doi.org/10.11973/jxgccl202202008
    The high temperature endurance test of G115 steel was carried out under different stresses at 625—700 ℃ to study its high temperature endurance performance, and the 1×105 h long-term endurance strength of the steel was extrapolated by the Larson-Miller(LM) parameter method. The oxidation test of G115 steel was carried out at 650 ℃/27 MPa steam parameter for 2 000 h, and the surface and cross-section morphology, phase composition and microarea composition of the oxide film were studied and compared with those of T92 steel. The results show that under the action of reinforcement of copper-rich phase, the long-term endurance strength of G115 steel at 650 ℃ was 82 MPa, which was significantly higher than 53 MPa of T92 steel. The steam oxidation resistance of G115 steel was better than that of T92 steel, and the thickness of oxide film on the surface of G115 steel was about 102 μm, which was smaller than about 110 μm of T92 steel. The oxide film structure of the two was similar. The outer oxide layer consisted of coarse columnar Fe3O4, and the inner oxide layer consisted of fine Fe-Cr spinel and a small amount of Fe3O4; the outer oxide layer had many holes, and the tendency of spalling was relatively large.
  • MA Mingtu, JIANG Songwei, LI Guangying, FENG Yi, ZHOU Jia, LU Hongzhou, LI Fuhuo
    Materials For Mechanical Engineering. 2020, 44(7): 1-7,27. https://doi.org/10.11973/jxgccl202007001
    Development in recent years of hot stamping steels, including ordinary hot stamping steel, hot stamping steel with high hardenability and oxidation resistance, high strength ductile hot stamping steel, ultra high strength hot stamping steel, high hydrogen embrittlement sensitivity hot stamping steel and ultra high strength hot stamping steel reinforced by nanoparticles, is summarized. The relation between lightweight and functionality of hot stamping steel parts, the relation between strength and hydrogen embrittlement and the influence mechanism of microstructure refinement on strength and toughness are analyzed. The suggestions for the further development direction of hot stamping steels are put forward.
  • LIU Kexiu, MA Kuo, FENG Xiaoliang, WANG Lian, XIE Xiaowu, LU Zhongming, LI Lushui
    Materials For Mechanical Engineering. 2021, 45(3): 29-34. https://doi.org/10.11973/jxgccl202103006
    The microstructure and mechanical properties at different positions of the two cast iron dryers in a paper mill after service for 62 a and 43 a were studied. The results show that there was no obvious surface defects and crack defects on the cylinder and end cover of the two dryers. The microstructure of substrate was pearlite without obvious spheroidization, and the size and distribution of the graphite sheets were mainly A type. The length of the graphite sheet of the front end cover of the dryer after service for 62 a and the rear end cover of the dryer after service for 43 a was relatively long. The hardness of the cylinder and the end cover of the two dryers all met the standards. The tensile strength of the front end cover of the dryer after service for 62 a was lower than the standard requirements, while those of the other positions of the two dryers all met the standard requirements. The tensile strength of the front end cover of the dryer after service for 62 a and the rear end cover of the dryer after service for 43 a was obviously lower than that of other positions. Both the two dryers still had sufficient strength under the maximum working internal pressure load of 0.22 MPa.
  • YUAN Zhaojing, LIU Hongyu, SHAO Yujia
    Materials For Mechanical Engineering. 2018, 42(12): 13-17,72. https://doi.org/10.11973/jxgccl201812003
    The rod end body of a rod end joint bearing fractured under tensile and compression loads. The fatigue fracture mechanism was analyzed by the observation of fracture morphology and microstructure and the measurement of micro area composition and hardness. The results show that the fatigue fracture of the rod end body occurred in the transition area between the rod and ring (position A) and on the ring in 45° direction to the rod (position B). Serious fretting wear existed between the ring inner face of the rod end body and the outer ring outer face of the joint bearing, resulting in the initiation of cracks. Under the tensile and compression loads, the microcracks at position B first propagated, leading to the fracture. The fracture at position B changed the force direction at position A, leading to the inclination of the rod end body. The inclination resulted in the cracking at position A, and finally led to the fracture of rod end body.
  • WANG Yinghu, SONG Lingxi
    Materials For Mechanical Engineering. 2021, 45(2): 37-42,48. https://doi.org/10.11973/jxgccl202102007
    Two titanium-sulfur containing free-cutting steels with titanium content (0.09wt% and 0.21wt%) were smelted and forged at 1 200 ℃. The morphology, size and quantity of sulfides in the structure and the mechanical properties of the as-cast and forged test steels were compared and studied. The results show that in the as-cast test steel, most of the manganese sulfides were short-rod-like and spherical, and distributed in chains or nets along the grain boundaries. After forging, the manganese sulfides extended along the forging direction, the statistically obtained length-width ratio increased, and the quantity per unit area decreased. The increase of titanicum content increased the quantity per unit area of manganese sulfides. The tensile fracture surface of the as-cast test steel showed cleavage terrace and river pattern, and the fracture mode was brittle fracture. The tensile fracture after forging showed cleavage and dimple mixed morphology, and the fracture mode was ductile fracture. The tensile properties and the impact toughness of the forged test steel were better than those of the as-cast steel, indicating forging was helpful to improve the mechanical properties of the titanium-sulfur containing free-cutting steel.
  • ZHOU Qiu-yue, WU Xiao-dong, LIANG Yu, XIE Jian-feng, WU Shun, ZOU Lei
    Materials For Mechanical Engineering. 2017, 41(4): 29-32,57. https://doi.org/10.11973/jxgccl201704007
    The hot compression deformation of 60Si2CrVAT high-strength spring steel was carried out on thermo-simulation machine at different temperatures (900,950,1 050,1 150℃) and strain rates of 0.1-10 s-1, the influences of deformation temperature and strain rate on hot deformation behavior of the steel were investigated. The hot-compression deformation constitutive equation of 60Si2CrVAT spring steel was established based on hyperbolic sine equations of Arrhenius type. The results show that the flow stress of the spring steel increased with the increase of deformation rate and decreased with the increase of deformation temperature, it was found that dynamic recrystallization was more likely to occur at high deformation temperature and low strain rate. And the activation energy was calculated to be 372 kJ ·mol-1 when true strain was 0.2, the calculated flow stress well agreed with the experimental results and the average relative error between them was 4.89%.
  • LU Yan, TAN Jinzhu, LI Yang, WANG Chao, LUO Shenghua
    Materials For Mechanical Engineering. 2021, 45(1): 105-108. https://doi.org/10.11973/jxgccl202101017
    The connecting bolts in a hydrogen reciprocating compressor were ruptured after woking normally for a period of time. The fracture cause of the bolts was investigated by fracture macro- and micro-morphology observation, chemical composition analysis, microstructure observation and mechanical property tests. The results show that the fracture mode of the bolts was low stress high cycle fatigue fracture. Under alternating stresses, some microcracks originated from the high stress concentration position at the root of the screw thread of the bolt. Improper heat treatment resulted in the mixed structure of tempered sorbite, upper bainite and ferrite, leading to the decrease of the strength and hardness of the bolts and the acceleration of fatigue crack propagation. Fianlly the fatigue fracture of connecting bolts occurred.
  • LIANG Chaojie, WANG Chenglei, LIANG Manchao, CHEN Zhonggan, XIE Yingguang, FU Yaokun
    Materials For Mechanical Engineering. 2020, 44(9): 62-66. https://doi.org/10.11973/jxgccl202009011
    Samples were taken from a forged deformation 6082 aluminum alloy control arm center, and were heat treated by solid solution at 510-590 ℃ and aging at 175 ℃. The effects of solution temperature on microstructure, hardness, and friction wear properties under loads of 2.8 and 6.8 N were studied. The results show that heat treatment improved the hardness and wear resistance of the alloy. With the increase of the solution temperature, the hardness of the alloy increased. When the temperature was 550 ℃, the alloy had the smallest grains and the highest hardnesss. As the temperature continued to rise, the grains became coarse, and the hardness decreased.The wear volume at 550 ℃ solution temperature was the smallest under the two loads. The wear mechanism of the samples with different heat treatments under the two loads was abrasive wear. Micro cracks and furrows appeared on the wear surfaces.
  • YANG Kang, YAN Zhaowei, LIANG Yu, WANG Ji, DING Wenxi
    Materials For Mechanical Engineering. 2021, 45(2): 85-89. https://doi.org/10.11973/jxgccl202102015
    A U-shaped thin-walled structure part model of T300 carbon fiber reinforced AG80 epoxy resin (T300/AG80) composite was established by ABAQUS finite element software. The stress and springback amount (synchronous demolding by simulation) changes during hot-press curing molding and the residual stress distribution after demolding were studied. The simulation of residual stress was verified by the small-hole test method. The results show that during the molding process, the stress and springback amount of the side wall and bottom surface of the U-shaped structure part increased with time. The stress and springback amount increased with the distance from the bottom surface or the distance from the center of symmetry. After demolding, the residual stress at the center of symmetry of the U-shaped structure part was the smallest, and the residual stress increased with the distance from the bottom surface or the distance from the center of symmetry. The greater the residual stress released before and after demolding, the greater the springback amount. The relative error between the residual stress measured by the small-hole method and the simulation was less than 10%, indicating the simulation was accurate.
  • ZHU Dong, ZHANG Liang, WU Wenheng, LU Lin, NI Xiaoqing, SONG Jia, ZHU Wenhua, WANG Jiaqi
    Materials For Mechanical Engineering. 2020, 44(8): 1-4,9. https://doi.org/10.11973/jxgccl202008001
    Selective laser melting technique is a widely used laser additive manufacturing technology in preparation of precise and complex parts, which could realize the near net forming of complex parts. Through the forming process parameters, and solution and aging treatment methods, the research progress of microstructure and mechanical properties control of TC4 alloy formed by selective laser melting in the current stage is reviewed, and the future development direction is prospected.
  • LI Tiantian, SUN Yaoning, ZHANG Li, WANG Guojian
    Materials For Mechanical Engineering. 2020, 44(5): 44-48. https://doi.org/10.11973/jxgccl202005009
    Surface texture technique is a new type surface modification technique, which can effectively improve the tribological properties of materials through machining patterns with a certain shape and size, and with regular arrangement on the surface of materials by micro-fabrication technique. Surface texture plays an important role in mechanical friction pairs because of its outstanding advantages in improving the tribological characteristics of materials. The common texture preparation methods are introduced; the wear reducation mechanism of surface texture under different working conditions is described; the influence of surface texture topography and its geometric parameters on the wear resistance is summarized. The development direction of surface texture technology is prospected.
  • LI Xingdong, LI Yan, AI Di, LI Yufeng, LIU Ruiliang
    Materials For Mechanical Engineering. 2021, 45(2): 31-36,89. https://doi.org/10.11973/jxgccl202102006
    The bainite transformation point at different quenching temperatures (950-1 100 ℃) and the continuous cooling phase transformation point at the optimal quenching temperature of 20Cr1Mo1VTiB steel were measured on a thermal dilatometer. Then the continuous cooling transformation curves were drawn by combination of the phase transformation points, microstructure observation and hardness test. The relationship between the phase transformation point or transformation amount and the cooling rate was established with empirical equations, and the phase transition activation energy was calculated. The results show that the bainite transformation temperature of the test steel decreased with increasing quenching temperature; the preferred quenching temperature was 1 050 ℃. The supercooled austenite transformation products were proeutectoid ferrite, pearlite and bainite with cooling rates not higher than 0.5 ℃·s-1, and were single bainite with cooling rates higher than 0.5 ℃·s-1. The fitting curves of phase transformation point- and phase transformation amount-cooling rate were in good agreement with the test results. The activation energy of proeutectoid ferrite and bainite transition was 744.8, 274.9 kJ·mol-1, respectively.
  • DONG Weiwei, LIN Jian, XU Hailiang, FU Hanguang, LEI Yongping, WANG Xibo
    Materials For Mechanical Engineering. 2019, 43(5): 38-42,48. https://doi.org/10.11973/jxgccl201905008
    Pulsed laser lap welding was conducted on SUS304 stainless steel sheets (0.2 mm thick), at different laser power (140-420 W) and welding velocities (10-30 mm·s-1), namely different heat input. The influence of heat input on the weld formation was studied, and the microstructure and mechanical properties of the joint with optimal formability were analyzed. The results show that a well-formed weld can be obtained when the heat input was in the range of 9-20 J·mm-1; the forming performance was the best at laser power of 320 W and welding velocity of 20 mm·s-1 (heat input of 16 J·mm-1). The microstructure in the weld center of the joint with optimal formability consisted of equiaxed grains, in the fusion line consisted of fine columnar grains, and in the weld near fusion line of cellular dendrites. The hardness at the fusion line of the welded joint with optirnal formability was the highest, followed by the weld zone. The joints obtained at different laser power and welding velocities all fractured in the heat-affected zone. The tensile strength of the joint with optinal formability was the highest of 790.1 MPa, which was close to that of the base metal, and the tesile fracture mode was ductile.
  • ZHOU Qingsong, HAO Qingguo, YANG Qi, ZHANG Ke, LIU Ping
    Materials For Mechanical Engineering. 2021, 45(1): 14-19,27. https://doi.org/10.11973/jxgccl202101003
    60Si2Mn spring steel was treated by quenching and partitioning (Q&P) at different quenching temperatures (140,160,180 ℃). The microstructure and mechanical properties of the steel after Q&P treatment were investigated, and compared with those after traditional quenching and tempering (Q&T) treatment. The results show that the microstructure of 60Si2Mn spring steel after Q&P treatment consisted of retained austenite and martensite, and the volume fraction of retained austenite was more than 12%. The microstructure of the steel after Q&T treatment was tempered troostite/tempered sorbite. The strength and hardness of the steel after Q&P treatment decreased with increasing quenching temperature, and the percentage elongation after fracture, impact energy and product of strength and elongation increased, which were all larger than those after Q&T treatment. The comprehensive performance of the spring steel after Q&P treatment was better than that after Q&T treatment because of the transformation-induced plasticity effect caused by the restained austenite during deformation.
  • WANG Xiaobo, HE Zhiyong, WANG Feng, ZHANG Qifu
    Materials For Mechanical Engineering. 2021, 45(7): 1-6,34. https://doi.org/10.11973/jxgccl202107001
    Silicon carbide ceramic has high strength and thermal conductivity, and good chemical stability, and is widely used in aerospace, petrochemical, integrated circuits and other fields; however, defects are easy to form in the silicon carbide ceramic during processing because of its high hardness and brittleness, which restricts the application of silicon carbide ceramic with complex structures. The preparation processes of silicon carbide ceramic with complex structures are described, and the advantages and disadvantages of the commonly used preparation technologies, such as cold isostatic pressing combined with pressure-free sintering, gel injection molding combined with reactive sintering, slip casting combined with reactive sintering, 3D printing combined with reactive sintering, are analyzed in order to provide a certain theoretical reference for the preparation of silicon carbide ceramic with complex structures.
  • XU Huanhuan, LIN Chen, LIU Jia, ZHANG Liang, SHEN Jingyi
    Materials For Mechanical Engineering. 2021, 45(7): 27-34. https://doi.org/10.11973/jxgccl202107006
    The mixed powders with nickel-coated tungsten carbide powder and CeO2 powder was used as raw materials, WC reinforced nickel-based alloy coating was prepared on the surface of 42CrMo steel by laser cladding technique. The effect of mass fraction (0-2.0%) of CeO2 in raw materials on the phase composition, microstructure, hardness and wear resistance of the coating was investigated. The results show that the phase of the coating with CeO2 was composed of γ-(Ni, Fe) solid solution, Ni3Fe, WC, Cr23C6, M7C3 (M=Fe, Cr) and a small amount of CeNi3. A good metallurgical bond was formed between the coating and the substrate. When the mass fraction of CeO2 was 1.0%, the structure was dense and uniform, and the refinement effect was the most obvious. With increasing CeO2 content, the hardness of the coating increased first and then decreased, and the friction coefficient and the amount of wear decreased first and then increased. The average hardness of the coating with 1.0% CeO2 was the highest, which was 956.0 HV, and increased by 29% compared with that without CeO2; the average friction coefficient and the average wear volume were the smallest, which were 0.383 and 11.25×10-3 mm3, and were reduced by 27% and 20% compared with those without CeO2, respectively. The wear resistance of the coating with 1.0% CeO2 was the best, and the wear mechanism of the coating was slight abrasive wear.
  • XUE Houqing, SUN Changle, JIANG Xinqi, HU Hao, YANG Jichen
    Materials For Mechanical Engineering. 2021, 45(6): 57-61,69. https://doi.org/10.11973/jxgccl202106010
    Considering the effects of coating, and the effects of tensile time, tensile rate, viscoelastic stress and reaction force on initial stress, the improved hyperelastic constitutive and viscoelastic constitutive model of thermoplastic polyurethane composite fabric and a single fiber bundle were established by tensile test. The stress-strain and stress relaxation curves during the tensile process were predicted and compared with the test results. The results show that the established hyperelastic constitive model could accurately predict the stress-strain curve of the fabric and the single fiber bundle, and the realtive errors were less than 3.5%. The viscoelastic constitutive model could accurately predict the stress relaxation curve of the fabric, and the relative error was less than 3.21%.
  • YAO Xiaofei, TIAN Wei, XIE Faqin
    Materials For Mechanical Engineering. 2019, 43(5): 12-16. https://doi.org/10.11973/jxgccl201905003
    Immersion corrosion tests in NaCl solutions with different NaCl mass fractions (5%-35%) were conducted on super 13Cr tubing steel at room temperature. Corrosion morphology, corrosion rate, corrosion products of the steel and electrochemical characteristics of its surface corrosion film were studied. The results show that the tested steel had relatively good corrosion resistance in NaCl solution. The corrosion resistance decreased with increasing mass fraction of NaCl and the decline was obvious when the NaCl mass fraction increased over 25%. With increasing NaCl mass fraction, the corrosion form changed from local corrosion to general corrosion. The corrosion products were composed of Fe3O4,and the corrosion film was loose and not dense. The polarization curves of the corrosion film had a passivation zone, indicating that the film had passivation characteristics. The electrode process in the low-frequency zone was diffusion control, and that in the high-frequency zone was charge transfer control. The impedance of the corrosion film was determined by a time constant.
  • WANG Qianjin, XU Congchang, LI Jia, XU Hong, HE Hong, LI Luoxing
    Materials For Mechanical Engineering. 2021, 45(3): 76-82. https://doi.org/10.11973/jxgccl202103015
    A high precision equivalent experimental method for measuring micro-zone tensile properties of 6061-T6 aluminum alloy MIG welded joint was established. The temperature changed during the welding process was simulated by finite element, and relationship between temperature and tensile properties of joint micro-zone was established. The parameters that could characterize properties of each micro-zone material of joint was obtained, and verified that joint was equivalent to materials in different thermal states to established the fine model for predicting the properties of joint was reliability. The results show that the simulation of the temperature field, weld pool morphology and tensile properties were in good agreement with the experimental results. The error of the peak force between simulation by eguivalent weld joint and experiment was only 0.1%, and the displacement error of fracture failure was only 5.7%. The heat affected zone grid was divided into different thermal state materials on the basis of temperature distribution could effectively predict tensile properties of weld joint.
  • ZHANG Nan, TIAN Zhiling, ZHANG Shuyan, ZHANG Feihu
    Materials For Mechanical Engineering. 2020, 44(12): 53-61. https://doi.org/10.11973/jxgccl202012010
    A rutile type SG90T-9C slag-gas bonded protection flux cored welding wire was developed. The effect of the amount of silicon and manganese on microstructure and properties of the welding wire deposited metal and weld metal by welding Q960E steel was studied. The effect of heat input on morphology of M/A island in the weld microstructure was studied. The comprehensive properties of SG90T-9C welding wire were compared with CHT91K2, ESAB91K2 welding wires and H08Mn2SiA welding wire coupling HJ431 flux. The results show that with increasing manganese and silicon addition, the tensile strength of the deposited metal increased, and the impact toughness increased and then decreased. With increasing heat input, the M/A island shape changed from point to block and the island gathered on boundaries. The heat input should be controlled within 10 kJ·cm-1. Compared with other welding materials, the SG90T-9C welding wire deposited metal had excellent mechanical properties, the weld quality by welding Q960E steel was better, and the porosity and repair rate by welding Q960E steel frame reduced significantly.
  • DU Jinfeng, CAI Wenhe, WANG Bin, LIANG Jun, DONG Shuqing, WANG Zhichun, SUN Biao
    Materials For Mechanical Engineering. 2020, 44(9): 42-46,51. https://doi.org/10.11973/jxgccl202009007
    Tensile properties at 20, 540, 560 ℃ and stress-rupture strength at 540, 560 ℃ of P91 steel specimens with different hardness were tested. On the basis of the approximate parallel nature of stress-rupture strength versus rupture time curves of P91 steel at certain temperatures and hardness, the linear equation of stress-rupture strength and rupture time was established for P91 steel with different hardness. By using this linear equation, the stress-rupture strength versus rupture time curves of whole life cycles were obtained by fitting the short-term stress-rupture data of different hardness specimens, and the fitting results of stress-rupture strength were compared and analyzed with the test results. The results show that the fitted stress-rupture strength had relative errors of less than 6% comparing to the test results, indicating relatively high fitting accuracy. By obtaining the full-life stress-rupture strength versus rupture time curves of P91 steel with different hardness with short-term stress-rupture data, the stress-rupture strength of P91 steel parts with abnormal hardness can be evaluated without destroying the integrity of parts.