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  • Material Properties & Application
    ZHAO Qiuhong, WANG Qingfen, MA Daoyuan
    Materials For Mechanical Engineering. 2023, 47(7): 62-66. https://doi.org/10.11973/jxgccl202307010
    Fe-0.9C-1.4Si-1.6Mn-0.8Cr-0.2Mo-0.25Al steel ingot was subjected to cold rolling and hot rolling deformation, respectively, and then was treated by austenitizing at 850-1 100 ℃ and isothermal treatment at 300 ℃. The effects of the rolling pre-deformation and austenitizing temperature on the microstructure and tensile properties were studied. The results show that the cold rolled pre-deformed steel was mainly composed of bainite ferrite and retained austenite after austenitizing at 950 ℃, while the hot rolled pre-deformed steel was composed of bainite and retained austenite. Compared with that of the non-pre-deformed steel, the retained austenite content decreased. Cold rolling deformation could improve both tensile strength and percentage elongation after fracture of the steel, while hot rolling deformation could reduce the percentage elongation after fracture. The content of retained austenite in cold rolled pre-deformed steel did not change much at austenitizing temperatures of 850-1 050 ℃, but decreased at 1 100 ℃. At the austenitizing temperature of 1 100 ℃, flake Widmanstatten ferrite appeared. With the increase of austenitizing temperature, the tensile strength and percentage elongation after fracture of cold rolled pre-deformed steel first increased slightly and then decreased, and reached the maximum at the austenitizing temperature of 950 ℃.
  • Failure Analysis
    WANG Ming, WANG Qiongqi, ZHONG Jiru, GUAN Kaishu
    Materials For Mechanical Engineering. 2023, 47(8): 100-105. https://doi.org/10.11973/jxgccl202308016
    Brittle bursting occurred in 20 carbon steel pipe of diesel hydrogenation recycling in a chemical plant. The pipe debris was treated by stress relief annealing and dehydrogenation treatment, respectively. By comparing the microstructure and mechanical properties of the treated debris with those of the untreated original debris, as well as combination with chemical composition detection and fracture morphology observation, the cause of the pipe bursting was analyzed. The results show that strain-age embrittlement occurred in the pipe material after a long period of service, leading to brittle bursting of the pipe. The relatively high nitrogen content in the pipe material and the large deformation of the grains were the main reasons for strain-age embrittlement.
  • Material Properties & Application
    CAO Tieshan, CHEN Qiao, WANG Wei, CHI Qingxin, CHENG Congqian, ZHAO Jie
    Materials For Mechanical Engineering. 2023, 47(7): 55-61. https://doi.org/10.11973/jxgccl202307009
    Effects of pre-strains (0.5%, 1.0%, 1.5%, 2.0%, 2.5%), loading strain rates (4.0×10-5, 1.2×10-4, 4.0×10-4 s-1) and initial temperatures (750, 900 ℃) of continuous temperature stress relaxation tests on directionally solidified nickel-based alloy DZ411 were studied. Based on steady-state deformation obtained by dynamic equilibrium of work hardening and recovery softening, assuming that the change of the steady-state relaxation strain rate with stress was consistent with that of the minimum creep rate of the traditional creep rupture test, the minimum creep rate was predicted and verified by short-term stress relaxation tests. The results show that the test alloy was relaxed when the work hardening and recovery softening were in dynamic equilibrium. When the pre-strain was not less than 1.0%, the steady-state relaxation could be quickly achieved. The initial temperature had little effect on the steady-state relaxation behavior. The loading strain rate affected the initial relaxation strain rate, but had little effect on the change of steady-state relaxation strain rate with stress. The minimum creep rates under different temperatures and stresses could be predicted by the master curve of steady-state relaxation strain rate. The creep rupture test results were located in the range of 99% reliable curve of the master curve of steady-state relaxation strain rate.
  • Material Properties & Application
    LI Ying, HOU Huipeng, ZHANG Ting, CHAI Xianghai
    Materials For Mechanical Engineering. 2023, 47(10): 79-84. https://doi.org/10.11973/jxgccl202310013
    GH3536 alloy longitudinal and transverse samples were prepared by selective laser melting. After heat treatment and hot isostatic pressing treatment, some samples were machined into smooth-surface samples. The influence of surface state on tensile and fatigue properties was studied by comparing with build-surface samples. The results show that there was little difference in the longitudinal room temperature tensile properties between smooth-surface samples and build-surface samples, so the surface state had no significant effect on the tensile properties. Compared with that of smooth-surface samples, the strain fatigue life of build-surface samples was slightly lower, and the stress fatigue life of build-surface samples was significantly reduced, which was 2%-8% of smooth-surface samples. The cracks in the crack source region of the smooth-surface samples were radially shaped, those in the propagation region were vein-like, and there were a lot of dimples in the instantaneous fracture region. There were no obvious radial cracks in the build-surface samples, which was multi-source cracking, and the fracture was cleavage fracture.
  • Testing & Research
    LI Hongling, ZHANG Yanling
    Materials For Mechanical Engineering. 2023, 47(7): 37-42. https://doi.org/10.11973/jxgccl202307006
    With zinc powder and aluminum powder as raw materials and lanthanum nitrate as additive, lanthanum nitrate modified chromium-free Dacromet coating was prepared. The phase composition and micromorphology of the corrosion products of the coating after immersion in 5wt% NaCl solution were studied, and the corrosion behavior and anti-corrosion mechanism of the coating were investigated. The results show that after immersion in NaCl solution for 10 d, some zinc-rich phases in the modified coating were preferentially corroded to form Zn5(OH)8Cl2·H2O, and the surface showed a honeycomb morphology; after immersion for 30 d, the corrosion products increased and Zn5(OH)6(CO3)2 was formed, and the surface showed a sponge-like structure; after immersion for 60 d, the corrosion products gradually dissolved and peeled off, and the surface showed a three-dimensional porous network structure. The anti-corrosion mechanism of the coating included the self-repairing effect of corrosion products and rare earth passivation film, the physical shielding effect of organic silane passivation film and lamellar zinc-aluminum powder overlapping, the sacrificial anodization effect of zinc-aluminum metal, the passivation effect of rare earth and the slow-releasing effect of corrosion inhibitor.
  • New Materials & Technology
    YANG Qiyun, TAO Jie, WU Wenheng
    Materials For Mechanical Engineering. 2023, 47(7): 50-54,84. https://doi.org/10.11973/jxgccl202307008
    CoCrFeNiCuAl0.8 high entropy alloy was prepared by selective laser melting(SLM).The forming quality and density of the alloy at different laser heat inputs (0.06-0.36 J·mm-1) were studied, and the optimal forming process parameters were determined. The microstructure and tensile properties of the alloy under the optimal forming process parameters were analyzed. The results show that the density of SLM formed alloy increased first with the increase of heat input, and basically remained unchanged when the heat input was larger than 0.15 J·mm-1. When the heat input was 0.34 J·mm-1, the alloy had the maximum density of 7.5 g·cm-3, and the optimal process parameters were as follows: laser power of 270 W and scanning speed of 800 mm·s-1. The SLM formed alloy had a dual-phase structure consisted of disordered body-centered cubic phase (A2 phase) and ordered body-centered cubic phase (B2 phase), and the microstructure was composed of columnar and equiaxed grains. The yield strength, tensile strength, percentage elongation after fracture and percentage reduction of area of the alloy were 651 MPa, 840 MPa, 22% and 23%, respectively.The fracture mechanism was ductile fracture.
  • Testing & Research
    LEI Xin, YANG Tianye, CHEN Wanqi, ZHENG Yue
    Materials For Mechanical Engineering. 2023, 47(7): 31-36. https://doi.org/10.11973/jxgccl202307005
    S30403, S32101 and S32205 stainless steel structural parts for nuclear power plant pool cladding were corroded in a boric acid solution containing SO2-4 and Cl- for six months. The corrosion resistance of the three stainless steel structural parts was studied comparatively and the corrosion mechanisms were analyzed. The results show that the S32205 stainless steel structural part had uniform corrosion and less surface corrosion products, indicating the corrosion degree was slight. The selective corrosion of the S32101 stainless steel structural part occurred, and deep corrosion pits appeared. Blue-green corrosion products were found in the corrosion pits. Stress corrosion cracking occurred in the S30403 stainless steel structural parts, and the crack fracture showed cleavage fracture morphology, indicating the corrosion was the most serious. The selective corrosion of ferrite phases occurred in the S32101 stainless steel structural part due to the potential differences between ferrite phase and austenite phase and the low chromium content in ferrite. The single-phase austenitic S30403 stainless steel structural part was sensitive to Cl-, had high residual stresses, and could not form a two-phase synergy, resulting in stress corrosion cracking and fast crack propagation.
  • Physical Simulation & Numerical Simulation
    WEN Feijuan, WEN Qifei, LONG Zhang, SONG Meng, CAO Liqing
    Materials For Mechanical Engineering. 2023, 47(8): 86-92,99. https://doi.org/10.11973/jxgccl202308014
    The thermal compression test of TC17 titanium alloy at different temperatures (600~950 ℃) and different strain rates (0.001~10 s-1) was carried out, and the hot deformation behavior of TC17 titanium alloy was studied. The multiple linear regression constitutive model of TC17 titanium alloy was established and verified by experiments. The results show that the flow stress of TC17 titanium alloy decreased with the increase of deformation temperature, but increased with the increase of strain rate. At low temperatures (600~850 ℃), the true stress-true strain curve showed strain softening characteristics on the whole, while at high temperatures (850~950 ℃) showed steady flow characteristics, and the softening of flow stress at high temperatures was not obvious. The calculated value of the flow stress by the multiple linear regression constitutive model of TC17 titanium alloy was close to the experimental value, indicating the model had relatively high prediction accuracy.
  • Material Properties & Application
    XIE Rui, LYU Zheng, WANG Qing, LIU Chunming
    Materials For Mechanical Engineering. 2023, 47(8): 72-78. https://doi.org/10.11973/jxgccl202308012
    Fe-9Cr-1.5W-0.3Ti-0.3Y alloy powder was prepared by atomization method and then was subjected to ball milling for different time intervals. 9Cr oxide dispersion strengthened (ODS) steel was prepared by hot isostatic pressing with the alloy powder as raw materials. The microstructure and tensile properties of the 9Cr-ODS steel were studied. The results show that the atomized alloy powder was a regular spherical α-Fe alloy powder with average particle size of 47.83 μm and grain size of about 20 μm. After ball milling for 20 h, the average particle size and grain size of the alloy powder decreased significantly to 30.50 μm and 12 nm, respectively. With the extension of milling time, the grain size of 9Cr-ODS steel decreased and the content of precipitated phase increased. Prolonging ball milling time was beneficial to improve the room temperature and high temperature tensile strength of the 9Cr-ODS steel, but not conducive to improving the high temperature toughness.
  • Review
    WANG Tingxuan, ZHANG Jian, LIU Jing, SONG Dekun
    Materials For Mechanical Engineering. 2023, 47(8): 1-7,58. https://doi.org/10.11973/jxgccl202308001
    Laser cladding technology is a new type of surface modification technology with broad development prospects, which not only meets the requirements for surface specific properties of materials, but also saves a lot of precious elements. The crack problem is one of the main obstacles restricting the wide industrial application and further development of laser cladding technology. The causes of crack formation in laser clading layers are described, and the crack control measures are reviewed, including the material composition design of cladding layers, setting the transition layer, process parameter optimization, matrix preheating, external field (force) assistance, etc. Finally the problems existing in the current crack control measures of laser cladding layers are summarized, and the future research direction is prospected.
  • Testing & Research
    ZHOU Yong, SUN Youping, HE Jiangmei, LI Wangzhen, XIE Ziwen
    Materials For Mechanical Engineering. 2023, 47(7): 22-30. https://doi.org/10.11973/jxgccl202307004
    Laser butt welding-brazing was conducted on 6061-T6 aluminum alloy and galvanized Q235A steel at different laser powers (1.0-1.4 kW) with Er2319 wire as filler metal. The effect of laser power on microstructure and tensile properties of the joint was studied. The results show that aluminum alloy and steel could be effectively connected at the laser power of 1.1-1.3 kW, and when the laser power was 1.2 kW, the forming quality was the best. At the laser power of 1.1, 1.2 kW, a large number of equiaxed crystals and a small number of broken dendrites were formed in the weld, and at the laser power of 1.3 kW, the microstructure mainly consisted of coarse acicular crystals. The thickness of the intermetallic compound layer at the interface of the joint at the laser power of 1.2 kW was less than that at the laser power of 1.1 kW. The tensile strength of the joints increased first and then decreased with increasing laser power, and was the largest (107.43 MPa) at the laser power of 1.2 kW; the joint showed a mixed fracture mode of ductile and brittle.
  • Testing & Research
    SHOU Derong, DENG Zhenghua, ZHANG Chaoyang
    Materials For Mechanical Engineering. 2023, 47(8): 18-22. https://doi.org/10.11973/jxgccl202308003
    With copper powder, aluminum powder, nickel powder and copper-coated iron powder as raw materials, Cu-10Al-4Ni alloys containing different mass fractions (0, 1.6%, 3.2%, 4.8%, 6.4%) of iron were prepared by powder metallurgy process. The effect of iron content on the microstructure and properties of the alloy was studied. The results show that the microstructure of the alloy without iron addition consisted of Κ phase, α phase and Al4Cu9 phase. When the mass fraction of iron was 1.6%, the Κ phase increased and Al4Cu9 phase decreased in the alloy. When the mass fraction of iron was 3.2%, Al4Cu9 phase further decreased, and Κ and Κ phases were precipitated in the alloy. When the iron content continued to increase, the Al4Cu9 phase disappeared, Κ phase increased while Κ phase decreased. With increasing iron content, the sintered density of the alloy decreased, the hardness decreased first then increased and then decreased, and reached the maximum with iron mass fraction of 3.2%. The yield strength of the alloy fluctuated with increasing iron content, and reached the maximum when the mass fraction of iron was 4.8%.
  • New Materials & Technology
    TAN Xiaobo, ZHOU Jiali, LI Yun, ZHANG Longguan, LI Kaifu, HUANG Bin, XIE Shuchang, CHENG Yanhai
    Materials For Mechanical Engineering. 2023, 47(10): 62-67. https://doi.org/10.11973/jxgccl202310010
    FeCrB/NiCrB alloy coating was prepared by laser cladding technique on H13 steel substrate, and the microstructure, hardness, friction and wear performance and impact resistance of the coating were studied. The results show that there were no obvious cracks in the FeCrB/NiCrB alloy coating, and the forming quality was good. NiCrB alloy bonding layer was mainly composed of equiaxed and dendrite grains, and was tightly bonded to FeCrB alloy coating. The average hardness of FeCrB alloy coating, NiCrB alloy bonding layer and the substrate was 840, 403, 285 HV, respectively. Under 300, 600, 900 N load, the friction factors of the coating were 0.35, 0.44 and 0.42, respectively, and the corresponding wear amounts were 5.29, 248, 300 mg, respectively. The average impact absorbing energy of the coating was 12 J and was higher than 3 J of substrate; the fracture mechanism was ductile fracture.
  • Testing & Research
    PAN Hao, YANG Fan, GONG Meina, LIU Yongzhen, ZHOU Jinxin, HUANG Yuxin, MA Yonglin
    Materials For Mechanical Engineering. 2023, 47(8): 29-33. https://doi.org/10.11973/jxgccl202308005
    T6 heat treatment was conducted on A356 aluminum alloy, whose aging process was carried out under 33 mT low intensity pulse magnetic field. The effects of aging temperature (175,185 ℃) and aging time (50, 60, 70 min) on the microstructure and mechanical properties of A356 aluminum alloy were studied. The results show that after aging under pulse magnetic field, the secondary dendrite spacing of A356 aluminum alloy decreased with the increase of aging temperature or aging time, and the aspect ratio of eutectic silicon decreased first and then increased with the increase of aging time. The size and aspect ratio of eutectic silicon at 185 ℃ aging temperature were higher than those at 175 ℃, but the quantity decreased. After aging under pulse magnetic field, the tensile strength and yield strength of A356 aluminum alloy increased with the increase of aging time or aging temperature. The improved heat treatment process for A356 aluminum alloy was solid solution at 540 ℃ for 60 min+aging at 175 ℃ for 70 min, and during aging applying 33 mT pulse magnetic field. Treated by this process, the tensile properties of the aluminum alloy met the reguirements.
  • New Materials & Technology
    QIN Song, ZHOU Jianqiao, YANG Jialin, LI Yong, ZHOU Ao, XIA Guangming
    Materials For Mechanical Engineering. 2023, 47(8): 45-51,105. https://doi.org/10.11973/jxgccl202308008
    With self-made high-purity Y2O3 powder as raw material, Y2O3 coating was prepared on the surface of A6061 aluminum alloy substrate by atmospheric plasma spraying. Based on the response surface methodology, the corresponding response surface maps were constructed, and the influence of the interaction of spraying voltage (60-80 V), spraying current (500-600 A) and spraying distance (100-120 mm) on the microhardness and porosity of the coating was analyzed. The plasma spraying process was optimized. The results show that a quadratic mathematical model of the microhardness and porosity of coating was established by response surface methodology. The optimal process parameters of the Y2O3 coating predicted by the model were listed as follows: spraying voltage of 78 V, spraying current of 500 A and spraying distance of 120 mm. The corresponding microhardness and porosity were 633.28 HV and 3.22%, and the relative errors of the predicted value and the test value were 1.92% and 1.26%, respectively, verifying the accuracy of the model. Under the optimal process, the surface roughness of the prepared coating was 5.733 μm, and the bonding strength was 25.6 MPa.
  • New Materials & Technology
    YANG Yu, LEI Longlin, CAO Liying, WANG Lin, WANG Guoqing
    Materials For Mechanical Engineering. 2023, 47(7): 43-49,61. https://doi.org/10.11973/jxgccl202307007
    Nano zinc oxide modified by triazole ring fluorinated aromatic hydrocarbon (ZnO-sTRF) was prepared by Cu+ catalyzed azidoyne ring dipole addition click chemistry reaction under different catalysts (CuBr/PMDATA or CuSO4·5H2O/sodium ascorbate) and reaction temperatures (55,65,75 ℃). The chemical structure and element composition of ZnO-sTRF were studied. ZnO-sTRF with the highest surface grafting amount was added in polyurethane (PU) to prepare ZnO-sTRF/PU coating. The hydrophobic, antibacterial and antifouling properties of the coating were studied. The results show that with CuSO4·5H2O/sodium ascorbate as catalyst at 75 ℃ , the surface grafting amount of modified nano-ZnO was the highest. The water contact angle of ZnO-sTRF/PU coating surface could reach 105.4°. The area coverage of dead bacteria of surface against escherichia coli, staphylococcus aureus and pseudoaltermonas were more than 10 times that of ZnO/PU and 3-aminopropyltriethoxysilane modified ZnO/PU coatings. After immersion in the actual marine environment for 120 d, the surface of the coating had no obvious adhesion of hard organisms.
  • Testing & Research
    GUO Wei, YU Qi, CHEN Yan, HU Yanbo, SONG Hongwu, WANG Songwei, YANG Guofu
    Materials For Mechanical Engineering. 2023, 47(7): 7-13. https://doi.org/10.11973/jxgccl202307002
    Cu-2Ag-0.04La alloy rod with a diameter of 14 mm was prepared by downward continuous casting directional solidification technology, and then was continuously extruded to obtain alloy wire with a diameter of 7 mm, and finally was drawed for 6 passes to obtain alloy wire with a diameter of 2 mm. The effects of continuous extrusion and drawing on the microstructure and properties of the alloy were studied. The results show that during continuous extrusion of the as-cast alloy, {001}〈100〉 texture was weakened, and a small amount of {111}〈112〉 and {110}〈112〉 textures were formed. After drawing, {001}〈100〉 texture disappeared, and the strength of {111}〈112〉 and {110}〈112〉 textures increased. The tensile strength, percentage elongation after fracture, hardness and conductivity of the continuously extruded alloy were 270.0 MPa, 31.2%, 84.3 HV, 93.2%IACS, respectively, and after drawing were 566.1 MPa, 4.6%, 151.6 HV, 88.9%IACS, respectively.
  • Material Properties & Application
    XIONG Xuegang, ZHANG Kaihua, CHEN Shu, LI Zhengrong, CUI Kaiyu, WANG Chuangwei
    Materials For Mechanical Engineering. 2023, 47(7): 72-76. https://doi.org/10.11973/jxgccl202307012
    DP600 steel with different Mn content was designed and industrially produced under different laminar cooling air cooling time. The effects of Mn mass fraction (0.65%-1.25%) and laminar cooling air cooling time (8-11 s) on microstructure and strength of the steel were studied. The results show that the average grain size decreased, and the martensite content, the yield strength, and the tensile strength increased with increasing Mn content or decreasing laminar cooling air cooling time. With the increase of Mn content, the morphology of martensite changed from dispersion to chain. When the mass fraction of Mn was 0.85%, and the laminar cooling air cooling time was 8-9 s, DP600 steel had the excellent tensile properties with yield strength of 441-462 MPa, tensile strength of 614-618 MPa, and the martensite area fraction in the microstructure was less than 20%.
  • Testing & Research
    LI Yajie, LIU Tao, HONG Lei, HONG Liang, HUANG Aiyi
    Materials For Mechanical Engineering. 2023, 47(10): 43-49. https://doi.org/10.11973/jxgccl202310007
    Dissimilar steel welding was carried out on SUS316L stainless steel and 15CrMo low-alloy steel by tungsten inert gas (TIG) welding with nickel base alloy welding wire ERNiCrMo-3 and stainless steel welding wire ER309. The microstructure and mechanical properties of the two welded joints were studied and compared. The results show that the solidification modes of the welds obtained with ERNiCrMo-3 and ER309 welding wires were austenitic and austenite-ferrite solidification modes, respectively, and the solidification structures were complete austenitic and mixed austenite-ferrite structures, respectively. Compared with using ER309 welding wire, using ERNiCrMo-3 welding wire could inhibit the diffusion of carbon in the welding process on 15CrMo steel side, and obtain a welded joint with higher tensile strength and percentage elongation after fracture. The peak hardness of the two welded joints appeared in the coarse-grained heat affected zone on 15CrMo steel side. Due to Laves phase in the weld obtained with ERNiCrMo-3 welding wire, the hardness was about 30 HV higher than that with ER309 welding wire.
  • Materials For Mechanical Engineering. 2023, 47(7): 0-0.
  • Testing & Research
    SHI Jianmeng, ZHANG Haibao, ZHANG Yueling, JIA Tianyi, WANG Xinlei, CHEN Yizhi, LIU Daoxin
    Materials For Mechanical Engineering. 2023, 47(7): 14-21,30. https://doi.org/10.11973/jxgccl202307003
    The surface morphology, surface roughness, residual stress, hardness and fatigue properties of 2A12-T4 aluminum alloy samples processed by diamond tool and carbide tool mirror milling and chemical milling were studied by contrast. The results show that comparing with that of chemical milled samples, the detailed fatigue rated strength of carbide tool mirror milled equal thickness flat sample (one side for carbide tool processing and the other side for diamond tool processing) was improved by 4.27%, while that of diamond tool mirror milled depression sample was improved by 22.46%. The fatigue resistance of diamond tool mirror milled sample was higher than that of carbide tool mirror milled and chemical milled samples. The diamond tool mirror milling introduced residual compressive stress on the sample surface, improved the surface hardness, decreased the surface roughness, and did not damage the surface structure, resulting in increase of crack initiation and propagation resistance. The pits, intergranular corrosion defect and residual tensile stress on chemical milled sample surface, and deep tool grooving and residual tensile stress on carbide tool mirror milled sample surface all promoted the initiation of cracks.
  • New Materials & Technology
    LING Zhuangzhuang, FENG Yuehai, XIA Jie
    Materials For Mechanical Engineering. 2023, 47(8): 39-44,64. https://doi.org/10.11973/jxgccl202308007
    WC reinforced iron-based alloy cladding layer was prepared by heating WC reinforced iron-based alloy powder-cored wire with resistance heat and plasma arc dual heat source simultaneously. The macromorphology, microstructure and properties of cladding layers under different hot wire currents (0,40,50,60,70 A) were studied, and the appropriate hot wire current was obtained. The results show that when the hot wire current was 50 A, the forming quality of the cladding layers was good with the lowest dilution rate of 51.77%. With increasing hot wire current, the average grain size of the cladding layer first decreased and then increased, and the carbide content first increased and then decreased. When the hot wire current was 50 A, the microstructure mainly consisted of fine cellular austenite, the average grain size was small (9.45 μm), and the carbide content was the highest. With increasing hot wire current, the average hardness of the cladding layer first increased and then decreased, and the wear rate and friction coefficient first decreased and then increased. When the hot wire current was 50 A, the cladding layer had the highest average hardness of 403.1 HV, the smallest friction coefficient of 0.52 and the smallest wear rate of 4.53×10-6 mm3·N-1·m-1.
  • Testing & Research
    ZHENG Cheng
    Materials For Mechanical Engineering. 2023, 47(8): 34-38. https://doi.org/10.11973/jxgccl202308006
    Tensile and compressive fatigue tests were carried out on SAPH440 steel sheet specimen with TC4 titanium alloy sheet anti-buckling device under different torques (1.5-2.5 N·m) and different strain levels (0.25%-1.0%). The effect of friction force on the fatigue life of the sheet specimen was studied, and the applicability of the anti-buckling device was verified. The results show that under the low strain level (0.25%) dominated by elastic strain, the fatigue life of the specimen decreased slightly with the increase of friction force. Under the medium and high strain levels (0.5%-1.0%) dominated by plastic strain, the fatigue life of the specimen increased with the increase of friction force. When the strain levels were 0.25% and 0.5%, the average distance between fatigue striations in the middle section of the crack propagation zone of the specimen was 0.45 μm and 0.86 μm, respectively. As the strain level continued to increase, the fatigue striations became less obvious, and more obvious secondary cracks appeared.
  • Testing & Research
    WEI Chenxi, LI Kai, YANG Weitao, ZHU Xiangrong, YANG Qi
    Materials For Mechanical Engineering. 2023, 47(8): 23-28,38. https://doi.org/10.11973/jxgccl202308004
    IF steels with average grain size of 40 μm and 210 μm were prepared by annealing at 850 ℃ and 950 ℃, respectively. The effects of the grain size on the low-cycle fatigue behavior and the microstructure after fatigue were investigated. The results show that during fatigue cycle, the initial average peak stress of the fine-grained test steel was higher than that of the coarse-grained test steel. The average peak stress of the two test steels tended to be equal with increasing number of cycles. The fine-grained test steel always showed cyclic work hardening during fatigue, while the coarse-grained test steel showed initial cycle hardening, cycle saturation and secondary cycle hardening. After 400 fatigue cycles, the microstructure of the fine-grained test steel was composed of similarly sized and uniformly distributed dislocation cells, while the microstructure of the coarse-grained test steel was mainly composed of macro-persistent slip band (Macro-PSB) and dislocation cells. The Macro-PSB contained relatively small dislocation cells. The coarse-grained test steel had higher dislocation density and relatively significant structural heterogeneity.
  • Testing & Research
    ZHU Lihua, SU Lei, XU Chun, XIAO Lei, WEI Bing, JI Hongjun
    Materials For Mechanical Engineering. 2023, 47(8): 8-17. https://doi.org/10.11973/jxgccl202308002
    The effects of spindle speed (300, 500, 650, 800, 1 200 r·min-1), milling feed (0.030, 0.045, 0.060, 0.075, 0.090 mm·r-1) and single pass milling depth (0.20, 0.35, 0.50, 0.65, 0.80 mm) on the machined surface integrity of nickel-based superalloy FGH4113A were investigated by milling tests. The results show that with increasing milling feed or single pass milling depth, the defects on the machined surface, surface roughness and hardness increased, and the surface residual stress gradually changed from compressive stress to tensile stress. With increasing spindle speed, the machined surface defects, surface roughness, hardness and residual compressive stress all decreased. When the spindle speed exceeded 800 r·min-1, the single pass milling depth was less than 0.35 mm, and the milling feed was controlled below 0.045 mm·r-1, the machined surface had good quality with surface roughness Ra of about 0.40 μm, compressive residual stress and no obvious hardening layer existing.
  • Material Properties & Application
    NIE Zhenyu, AI Li
    Materials For Mechanical Engineering. 2023, 47(8): 79-85. https://doi.org/10.11973/jxgccl202308013
    The atmosphere plasma sprayed 8wt% Y2O3 stabilized ZrO2 (8YSZ) thermal barrier coating was sealed with the sealant of fluorocarbon finish paint. The effects of sealing treatment on the microstructure, electrochemical corrosion behavior and salt spray corrosion resistance of the coating were investigated. The results show that the fluorocarbon finish paint permeated into the coating due to capillarity action. The surface roughness of the coating was reduced from 5.4 μm before sealing to 0.8 μm after sealing, and the contact angle increased from 61.99° before sealing to 70.58° after sealing. The self-corrosion potential of the coating decreased from -0.308 V before sealing to -0.42 V after sealing, indicating the sealing agent was anodic relative to the coating. After sealing, the passivation phenomenon of the coating was observed, the polarization resistance increased, and the self-corrosion current density decreased to 1.26×10-6 A·cm-2, indicating that the corrosion resistance of the coating increased. The fluorocarbon finish paint could provide a good sealing effect on the thermal barrier coating in the neutral salt spray environment, which could effectively inhibit the diffusion of Cl- into the coating.
  • Material Properties & Application
    ZHANG Jing, ZHAO Xiaolei, HU Sufen
    Materials For Mechanical Engineering. 2023, 47(8): 59-64. https://doi.org/10.11973/jxgccl202308010
    Forging stock of bearing steel used for railway locomotive was pretreated by water quenching. The forging stock and water quenching pretreated steel were subjected to austenitizing and isothermal quenching. The effect of water quenching pretreatment on the microstructure and mechanical properties of the bearing steel was studied. The results show that the microstructure of forged bearing steel was composed of pearlite and ferrite, and after water quenching pretreatment was composed of martensite and a little ferrite. After austenitizing and isothermal quenching, slender bainite slat bundles and massive martensite/austenite (M/A) islands appeared in both forging stock and water quenching pretreated steel. The bainite slat bundles in the water quenching pretreated steel were smaller, and M/A islands were more in amount and smaller in size. The tensile strength and yield strength of the water quenching pretreated steel after austenitizing and isothermal quenching were 8.68% and 17.07% higher than those of the forging stock, respectively, and the impact energy was also higher than that of the forging stock. But the elongation after fracture of the two was similar.
  • Material Properties & Application
    LI Yu, HE Sifan, LIU Guangming, YANG Shou, LIU Zhihao, LI Futian
    Materials For Mechanical Engineering. 2023, 47(8): 65-71. https://doi.org/10.11973/jxgccl202308011
    The S31035 steel was shot peened, and then the high temperature steam oxidation test was carried out at 665 ℃. The effect of shot peening on the high temperature steam oxidation behavior of the steel was studied. The results show that the unpeening sample had obvious oxide diffraction peaks after 100 h oxidation, and a double-layer of oxides was formed after 3 000 h oxidation. The oxide film thickness of the unpeening sample was about 8.07 μm. The weak (Fe,Cr)2O3 diffraction peak appeared in the shot peening sample after 1 000 h oxidation, and the surface oxide film was still thin after 3 000 h oxidation, with a thickness of only 0.45 μm. In oxidation, the oxidation rate constant of the shot peening sample was 3 orders of magnitude lower than that of the unpeening sample, and the steam oxidation resistance was better. The shot peening refined the surface grains, which provided more channels for chromium diffusion and led to formation of a Cr2O3 protective film on the surface, thereby improved the high temperature steam oxidation resistance of the steel.
  • Review
    ZHOU Qiong, DU Junlong, ZHANG Ergeng, HUANG Biao, LIANG Dandan, CHEN Qiang
    Materials For Mechanical Engineering. 2023, 47(7): 1-6,36. https://doi.org/10.11973/jxgccl202307001
    Cermet is widely used in manufacturing cutting tools because of its excellent strength, high temperature thermal conductivity and thermal stability of metal materials, and high temperature resistance and corrosion resistance of ceramic materials. The lack of wear resistance and hardness of cermet limits its application range, which can be solved by preparing hard coating on its surface, but the bonding strength of the coating is weak, resulting in peeling off of the coating. The preparation method of the hard coating, the influencing factors on the bonding strength between the coating and the substrate are introduced, and the methods to improve the bonding strength of the hard coating are expounded. Finally, the preparation technique and the improvement of bonding strength of hard coating on cermet surface are prospected.
  • Physical Simulation & Numerical Simulation
    LI Jihong, GUO Zhao, LI Baoling, ZHANG Min, GUO Yufei, GOU Chuandong
    Materials For Mechanical Engineering. 2023, 47(7): 97-103. https://doi.org/10.11973/jxgccl202307016
    On the basis of the MATLAB simulation platform and the grain nucleation and growth theory, the numerical calculation model of microstructure evolution of laser cladding layer of Inconel625 alloy was constructed by cellular antomata-finite difference method. The microstructure evolution of the alloy during single pass laser cladding was simulated by the model and verified by experiments. The effects of laser heat input and heterogeneous nucleation quantity on the grain morphology of the cladding layer were studied. The results show that according to the established model simulation, the inner part of the cladding layer was composed of columnar crystals and sub-grains distributed between columnar crystals, and the cladding layer near the fusion line consisted of cellular crystals; the simulation was consistent with the test results. The average size of columnar crystals obtained by simulation and test were 2.817, 2.743 μm, respectively, and the relative error was only 2.69%, which verified the reliability of the calculation model. With decreasing laser heat input or increasing heterogeneous nucleation quantity, the microstructure of the cladding layer was gradually refined, the number of grains increased, and the size of the columnar crystals decreased.
  • Material Properties & Application
    WANG Baojun, BAI Lu, CHEN Long, SHEN Xinjun
    Materials For Mechanical Engineering. 2023, 47(7): 67-71. https://doi.org/10.11973/jxgccl202307011
    S32101 duplex stainless steel plate with a thickness of 6.5 mm was welded by laser welding. The post-weld heat treatment at different temperatures (800-1 100 ℃) and different holding time (0-180 s) was carried out. The effects of post-weld heat treatment on the microstructure and properties of the weld were studied. The results show that the austenite content in the weld after heat treatment was higher than that of as-welded weld, its content increased with the extension of holding time, and increased first and then decreased with the increase of heat treatment temperature. The austenite volume fraction was more than 30% after the weld was held at 1 000-1 100 ℃ for 0-180 s, and the austenite volume fraction was the highest when the heat treatment temperature was 1 075 ℃. The average microhardness of the weld after heat treatment was lower than that of the as-welded weld and similar to that of the base metal. When the heat treatment temperature was 1 075 ℃,and the holding time was 0, the free-corrosion potential of the weld was similar to that of the as-welded weld. When the holding time was extended to 180 s, the free-corrosion potential increased, and the corrosion tendency decreased.
  • Testing & Research
    ZHANG Jiamao, DU Jin, LI Yinling, SHI Haichuan, SU Guosheng, ZHANG Peirong
    Materials For Mechanical Engineering. 2023, 47(10): 31-36,96. https://doi.org/10.11973/jxgccl202310005
    High-speed milling of GH4169 nickel-based superalloy was carried out at different milling speeds (500-1 000 m·min-1) and radial milling depths (0.1-0.3 mm). The effects of milling parameters on cutting force, cutting temperature, metamorphic layer and white layer thickness and surface layer hardness were studied. The results show that with the increase of milling speed, the cutting force decreased and the cutting temperature increased. The increase of milling depth resulted in the increase of cutting force and cutting temperature. Under the same milling depth, when the milling speed increased from 500 m·min-1 to 1 000 m·min-1, the thickness of the metamorphic layer increased by about 30 μm, the thickness of the white layer increased by about 5 μm, the microhardness of the surface layer increased by about 200 HV, and the depth of the hardened layer increased by about 100 μm. Under the same milling speed, when the milling depth increased by 0.1 mm, the thickness of the metamorphic layer increased by about 30 μm, the thickness of the white layer increased by about 3 μm, the hardness of the surface layer increased by 20 HV, and the depth of the hardened layer increased by about 20 μm.
  • Testing & Research
    LI Haifeng, ZHONG Yuan, LIU Jianwu, WANG Yiwei, FANG Bingbing, WANG Qun
    Materials For Mechanical Engineering. 2023, 47(10): 50-54. https://doi.org/10.11973/jxgccl202310008
    6061 aluminum alloy coating was cold sprayed on ZM6 magnesium alloy substrate at four driving gas temperatures (350,400,450,500 ℃). The effects of driving gas temperature on the microstructure, hardness and corrosion resistance of the aluminum alloy coating were studied. The results show that with the increase of driving gas temperature, the deposition rate of 6061 aluminum alloy powder increased significantly, the hardness of coating slightly decreased, but the porosity decreased significantly, and the corrosion resistance of the coating increased significantly. When the driving gas temperature was 500 ℃, the comprehensive performance of the aluminum alloy coating was the best; the porosity was 0.23%, the hardness was 89.8 HV, and the corrosion resistance was significantly better than that of ZM6 magnesium alloy.
  • New Materials & Technology
    ZHANG Lifeng, WANG Sheze, TIAN Botong
    Materials For Mechanical Engineering. 2023, 47(10): 55-61. https://doi.org/10.11973/jxgccl202310009
    The medium manganese steels for automobile were treated by preheating at different temperatures (150, 550, 600, 750 ℃), quenching at 750 ℃, cryogenic treatment at -75 ℃, respectively, and then were subjected to reverted transformation annealing. The microstructure and mechanical properties after different heat treatments were studied. The results show that the retained austenite content in medium manganese steel after preheating was higher than that in as-cast steel. The volume fraction of the retained austenite reached the maximum value of 42.2% after preheating at 600 ℃, and the microstructure was composed of block/strip martensite and retained austenite. With the increase of preheating temperature, the tensile strength of medium manganese steel after reverted transformation annealing increased, and the elongation after fracture and the product of strength and elongation increased first and then decrease. When the preheating temperature was 600 ℃, the product of strength and elongation reached the maximum value of 51.99 GPa·%. Compared with those after quenching and reverted transformation annealing, the tensile strength and yield strength of the medium manganese steel after cryogenic treatment and reverted transformation annealing were smaller, and the elongation after fracture, the product of strength and elongation and the impact energy at -40 ℃ were higher.
  • Material Properties & Application
    WU Longfeng, LIANG Zhongwei, FANG Zhichun, ZOU Tao, ZHANG Yupeng, XIN Jijun, WANG Wei, LI Laifeng
    Materials For Mechanical Engineering. 2023, 47(10): 91-96. https://doi.org/10.11973/jxgccl202310015
    Different mass fractions (0,3.2%,11.2%) of BN on AlN modified IR3 epoxy resin (BN/EP,AlN/EP) composites were prepared by solution blending method. The effects of nanoparticle content on the resin viscosity and the tensile and shear properties of the composites were studied. The results show that adding BN and AlN nanoparticles improved the resin viscosity by 5%-10%. The tensile strength of BN/EP and AlN/EP composites increased by 10%-25% comparing with that of the pure resin, and the tensile strength increased with the increase of BN and AlN content. The shear strength of the AlN/EP composite increased by 40%-60% comparing with that of the pure resin, and the shear strength increased with the increase of AlN content, but the shear strength of BN/EP composite was almost unchanged with the increase of BN content. When the mass fraction of nanoparticles was 11.2%, the epoxy resin had moderate viscosity and the mechanical properties of the composites were the best.
  • Testing & Research
    WANG Yuanjing, CHEN Jian, ZHOU Libo, LI Chaoying, LIAO Xingyu
    Materials For Mechanical Engineering. 2023, 47(10): 16-25. https://doi.org/10.11973/jxgccl202310003
    Porous Ti-15Mo alloy specimens with support cells (BCC, Kelvin cells) and triple periodic minimum surface (TPMS) cells (Primitive, Gyroid ,Diamond cells) were prepared by laser selective melting. The porosity was evenly distributed (uniform specimen), increasing along the forming direction (vertical gradient specimen), increasing perpendicular to the forming direction (lateral gradient specimen). The compressive deformation behavior of the alloy was studied. The results show that the inclined support or surface of the porous sample would bond more powder, and the forming quality was relatively poor. The deformation mechanism of vertical gradient specimens was layer by layer from the top to the bottom, and the deformation mechanism of lateral gradient specimens was the whole uniform deformation first, and then the local significant deformation occurred and extended to the uniform deformation region. The compressive properties and energy absorption capacity of TPMS cell specimens were higher than those of the support cell specimens. The Diamond cell specimen had the best comprehensive properties. The elastic modulus, yield strength, platform stress and cumulative energy absorption values of lateral gradient specimen were respectively 4.088 GPa, 134.5 MPa, 175.4 MPa, 117.92 MJ·m-3, and those of vertical gradient specimen were respectively 3.761 GPa, 104.8 MPa, 165.2 MPa, 92.19 MJ·m-3.
  • Testing & Research
    GONG Jianxun, DONG Hailong, HUANG Hongjiang, XIAO Zhiqiang
    Materials For Mechanical Engineering. 2023, 47(10): 37-42. https://doi.org/10.11973/jxgccl202310006
    Fe-Cr-V-B-C system high boron hardfacing alloys were prepared on Q235A steel surface by self-shielded open arc welding with composite powder particles and H08A solid wire. The effects of vanadium mass fraction (0-7.5%) on the microstructure and wear resistance were studied. The results show that when the mass fraction of vanadium was 0, the hardfacing alloy consisted of α-Fe, M2B and M3C phases. When the vanadium mass fraction was 1.5%, the content and size of the bulk M2B phase increased, and point and cross flower-like VC phase was precipitated between grains. When the vanadium mass fraction increased to 3.0% and 4.5%, the primary M2B grains were refined. When the vanadium mass fraction increased to 6.0%, needle and strip V3B2 phase was precipitated between and within M2B phases. When the vanadium mass fraction increased to 7.5%, the V3B2 phase content increased significantly and the M2B phase content decreased. With the increase of vanadium content, the hardness of the hardfacing alloy first increased and then decreased, and the wear mass loss first decreased and then increased. When the vanadium mass fraction was 3.0%, the hardfacing alloy had the highest hardness of 61.6 HRC and the smallest wear mass loss of 0.019 4 g, indicating the hardfacing alloy had the best wear resistance.
  • Physical Simulation & Numerical Simulation
    ZHANG Chaofeng, ZHANG Dajun, HE Biao
    Materials For Mechanical Engineering. 2023, 47(7): 77-84. https://doi.org/10.11973/jxgccl202307013
    The out-of-plane buckling characteristics of aluminum alloy sandwich panels with different length-to-width ratios and width-to-thickness ratios under point/surface load were studied by finite element simulation, and was verified by tests. The out-of-plane bearing characteristics of aluminum alloy sandwich panels with different size parameters were studied by tests. The results show that the simulated load-displacement curves of the sandwich panels under point/surface load were basically consistent with the test results, and the average relative error was less than 5%, proving the reliability of the finite element simulation. The failure mode of the sandwich panels under point load was overall piercing, and was core compression under surface load. Under point load, when the width-to-thickness ratio was 13.6, with increasing length-to-width ratio from 0.7 to 1.9, the failure load of the sandwich panels first increased and then tended to be stable; when the width-to-thickness ratio was 21.4, with increasing length-to-width ratio from 0.4 to 1.2, the failure load basically remained unchanged; the failure load with width-to-thickness ratio of 21.4 was greater than that with width-to-thickness ratio of 13.6. Under surface load, the yield load decreased with the increase of length-to-width ratio, and the yield load with width-to-thickness ratio of 13.6 was greater than that with width-to-thickness ratio of 21.4. When the critical value of out-of-plane buckling deformation was 3 mm, the critical buckling ratio of the sandwich plate under point/surface load was 0.093.
  • Physical Simulation & Numerical Simulation
    LIU Hui, XUE Lijun, CHEN Jiangxu
    Materials For Mechanical Engineering. 2023, 47(7): 104-110. https://doi.org/10.11973/jxgccl202307017
    Based on thermodynamics theory and equivalent inclusion principle, a force-magnetic coupling mesoscopic model of NiMnGa alloy/epoxy resin (NiMnGa/ER) composites including mechanical energy, chemical free energy, magnetocrystalline anisotropy energy, Zeeman energy and hardening fuction of reorientation process was derived. The stress-strain curves of the composite were simulated under zero magnetic field and compared with the test results. Finally, the stress-strain curves under different magnetic field intensities and angles (angle to stress direction, 0°, 45°) were predicted. The results show that the critical stresses of the reorientation of martensitic variants in the composites were 39.2 MPa, and of the reverse reorientation were 41.8 MPa, and the relative errors with the test results were all no more than 1.2%, verifying the accuracy of model. The stress-strain hysteresis loop of the composite at 45° magnetic field angle was larger than that at 0° magnetic field angle. When the magnetic field angle was 0°, the greater the magnetic field intensity, the greater the stress-strain hysteresis loop.
  • Physical Simulation & Numerical Simulation
    LI Lekun, ZHANG Tiejun, ZHI Le, WEI Xiaolong, WANG Bo
    Materials For Mechanical Engineering. 2023, 47(8): 93-99. https://doi.org/10.11973/jxgccl202308015
    The stiffened panels of CCF300 carbon fiber/BA9916-II epoxy resin composite were prepared. The compression behavior of the stiffened panel under dry and hygrothermal conditions was studied. The finite element model of the stiffened panel was established, and the material parameters in the hygrothermal environment were modified by the empirical formula. The compressive buckling and post-buckling behavior of the stiffened panel in different states were simulated and verified by experiments. The results show that the stiffened panel had strong post-buckling bearing capacity in both dry and hygrothermal states. The hygrothermal environment had a great negative effect on the stability and carrying capacity of the stiffened panel. With increasing moisture absorption time, the buckling and failure loads of the stiffened panel decreased fast and then slowly. The relative errors between the simulation and test resuls of buckling load and failure load of the stiffened panel in the dry state were 3.1% and 5.2%, and in the moisture saturation state were 5.6% and 6.9%, respectively. The errors were small, proving the accuracy of the simulation method and the reasonableness of the finite element model.