20 February 2023, Volume 47 Issue 2
    

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    Review
  • Research Progress on Defects and Forming Mechanisms of Selective Laser Melting Formed 316L Stainless Steel Parts
    CONG Jiaqi, JI Yunping, WANG Lei, KANG Xueliang, LI Yiming, REN Huiping
    Materials For Mechanical Engineering. 2023, 47(2): 1-6. https://doi.org/10.11973/jxgccl202302001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Selective laser melting (SLM) is one of the most widely used metal additive manufacturing techniques. Many defects are inevitably produced in the SLM formed parts, including pores, surface layer powder spheroidization, cracks and so on. The formation of defects not only affect the smoothness of the forming process, but also damage the internal integrity of the part and reduce its serviceability. The main characteristics of three defects including pores, surface layer powder spheroidization and cracks in SLM formed 316L stainless steel parts are reviewed. The formation mechanisms and influencing factors of these three defects are summarised, and the main measures to control the defects are proposed. Finally, future research directions are put forword.
    • Testing & Research
  • Directional Solidification Microstructure of Ti-46Al-8Nb Alloy and Effectof Crystal Selector Angle on Alloy Lamellar Orientation
    ZHANG Xuexian, DUAN Baohua, YANG Yuchen, MAO Lu, CHEN Guangyao, HOU Xinmei, LI Chonghe
    Materials For Mechanical Engineering. 2023, 47(2): 7-13,72. https://doi.org/10.11973/jxgccl202302002
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    Ti-46Al-8Nb (atomic fraction/%) alloy was directionally solidified by using BaZrO3/Al2O3 composite mold shell with Bridgman furnace. The interface erosion layer morphology, microstructure and phase composition of the alloy, and the effect of the crystal selector angle on the crystal selection efficiency and the alloy lamellar orientation were studied. The results show that after directional solidification, a 10 μm thick erosion layer existed at the bottom of the alloy. With increasing height, the oxygen content in the alloy and the thickness of the erosion layer increased. The alloy had a full lamellar structure composed of γ (TiAl) and α2 (Ti3Al) phases, and no inclusions existed. Within 30°-60°, the smaller the crystal selector angle was, the higher the crystal selection efficiency was. The crystal selector angle had little effect on the angle between the alloy lamellar orientation and growth direction.
  • Effect of CoCrFeNiWx High Entropy Alloy Binder on Microstructure and Mechanical Properties of WC Cemented Carbide
    YU Yifan, TIAN Jun, LIU Tao, CAI Xiaokang, LIU Chao, DAI Pinqiang
    Materials For Mechanical Engineering. 2023, 47(2): 14-20,25. https://doi.org/10.11973/jxgccl202302003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    CoCrFeNiWx(x=0.2, 0.5, mole fraction/%) high entropy alloy powder was prepared by mechanical alloying method. The powder was mixed with WC powder as a binder (adding mass fraction was 6%, 10%, 14%, respectively), and then WC cemented carbides were obtained by spark plasma sintering. The effect of the high entropy alloy binder on the microstructure and mechanical properties of the cemented carbide was studied. The results show that the CoCrFeNiWx high entropy alloy binder had a face-centered cubic and body-centered cubic dual-phase structure and could refine grains in WC cemented carbides. With the increase of high entropy alloy binder content, the Vickers hardness of the WC cemented carbide decreased, and the fracture toughness and bending strength had a general increase trend. The WC cemented carbide prepared by adding 10wt% CoCrFeNiW0.2 high entropy alloy binder had the best comprehensive performance, with Vickers hardness of 1 785 HV, fracture toughness of 10.6 MPa·m1/2, and bending strength of 1 373 MPa.
  • Powder Spreading Uniformity of IN718 Nickel-Based Superalloy Powder
    ZHANG Wei, JIANG Shengqiang, DUAN Chunyan, XIAO Xiangwu, TAN Yuanqiang
    Materials For Mechanical Engineering. 2023, 47(2): 21-25. https://doi.org/10.11973/jxgccl202302004
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    IN718 nickel-based superalloy powder was spreaded at different scraper moving speeds (28.23, 63.55, 91.11, 125.25 mm·s-1), and the powder layer thickness was 0.3, 0.5, 0.7, 0.9 mm, respectively. The powder at different positions with the same volume of the powder layer was collected by a self-made device for testing powder uniformity and weighted. The influence of the scraper moving speed and the powder layer thickness on the powder spreading uniformity was studied by calculating mass standard deviation. The results show that the mass standard deviation of the powder layer increased with the increase of the scraper moving speed or the powder layer thickness, indicating the powder spreading uniformity became worse; the scraper moving speed had a greater effect on the powder spreading uniformity. The optimal process parameter combination to obtain the best powder spreading uniformity was listed as follows:scraper moving speed of 28.23 mm·s-1 and powder layer thickness of 0.3 mm.
  • Effect of Niobium Content on Microstructure Evolution of HR3C Steel During High Temperature Aging
    YANG Conghui, CAO Tieshan, CHEN Xiangang, CHENG Congqian, ZHAO Jie
    Materials For Mechanical Engineering. 2023, 47(2): 26-32,66. https://doi.org/10.11973/jxgccl202302005
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    On the basis of the chemical composition of HR3C steel, the mass fractions of niobium element were adjusted to 0.5%, 0.8% and 1.1%, respectively. The ingot samples with the three components were obtained by melting, and then subjected to hot rolling, homogenization annealing at 1 200℃, solid solution at 1 200℃, and aging at 750℃ for different times (0-2 000 h). The effects of niobium content on the microstructure, grain size and hardness of the test steel were studied. The results show that increasing the niobium content could increase the content of undissolved MX phase in the solid solution test steel and reduce the grain size. During aging at 750℃, increasing the niobium content could promote the precipitation and coarsening of σ phase at grain boundaries and inside grains, and improve the hardness. When aging for 2 000 h, the niobium content had little effect on the size and distribution of grain boundary precipitates, but had some influence on the size and shape of intragranular precipitates; the test steel containing 1.1wt% niobium had a relatively small number of strip-like intragranular precipitates.
  • Effect of Bonding Temperature on Microstructure and Properties of TransientLiquid Phase Diffusion Bonded Joint of Titanium/Steel Composite Pipe
    YAO Shangjun, MIAO Xin, CHEN Sijie, HAO Lili, LI Zhenhao
    Materials For Mechanical Engineering. 2023, 47(2): 33-38. https://doi.org/10.11973/jxgccl202302006
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    Taking composite steel pipe with TA2 industrial pure titanium lining and 20 steel coating as the research object, and BNi2 amorphous alloy foil as the interlayer, the titanium/steel composite pipe was welded by transient liquid phase diffusion bonding at bonding temperatures of 1 130-1 200℃ under argon protection. The effect of bonding temperature on the microstructure and properties of titanium/steel composite pipe joints was investigated. The results show that the joints at different bonding temperatures were formed well without macroscopic defects such as holes and cracks. With increasing bonding temperature, the equiaxed microstructure of weld at the titanium side grew up, α→α'+β phase transition occurred, and the weld boundary became blurred gradually. The acicular ferrite and pearlite in the weld at the steel side became thicker, the black brittle phase gradually disappeared, and the diffusion distance of elements of interlayer and base material increased. The joints welded at different bonding temperatures all fractured in the weld at the titanium side. With increasing bonding temperature, the tensile strength of the joint increased first and then decreased. When the bonding temperature was 1 180℃, the tensile strength was the biggest of 460 MP, and the fracture form was ductile-brittle mixed fracture.
  • Effect of Austenitizing Temperature on Microstructure and Tensile Properties of C-Si-Mn Steel after Quenching and Partitioning Treatment
    YAN Jun, ZHOU Bowen, FAN Lei
    Materials For Mechanical Engineering. 2023, 47(2): 39-43,49. https://doi.org/10.11973/jxgccl202302007
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    0.2C-1.6Si-1.8Mn steel with initial martensite microstructures was subjected to austenitizing at different temperatures (840, 870, 910℃) and quenching-partitioning (Q&P) treatment. The effect of austenitizing temperature on the microstructure and tensile properties of the steel was studied. The results show that when the austenitizing temperature was in the two-phase region, the ferrite in the Q&P treated experimental steel was mainly banded, and the retained austenite was blocky and flaky. With the increase of austenitizing temperature, the content of ferrite and retained austenite decreased, and the content of martensite increased; accordingly, the yield strength and the tensile strength increased while the percentage elongation after fracture and the product of strength and elongation decreased. The higher percentage elongation after fracture of the Q&P treated experimental steel at austenitizing temperature of 840℃ was related to the higher content of the retained austenite with two forms of block and flake, which could effectively expand the transformation induced plasticity effect range.
  • Effect of Grain Size on Tensile Properties at Different Temperatures of 304L Stainless Steel
    SANG Wenya, MA Libing, JI Mingyue
    Materials For Mechanical Engineering. 2023, 47(2): 44-49. https://doi.org/10.11973/jxgccl202302008
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    304L stainless steels with two different grain size were fabricated by cold rolling and annealing at 900℃ and 700℃, respectively. The effect of grain size on room-temperature and high-temperature tensile properties of the steels was studied. The results show that the annealing treatment made the cold-rolled elongated grains recrystallize to form equiaxed grains. When the annealing temperature was 900℃ and 700℃, the average grain size was 63 μm and 3 μm, respectively. During tension at 25℃ and 200℃, the yield strength of the test steel with fine grains was higher than that of the test steel with coarse grains, but the percentage elongation after fracture was lower than that of the test steel with coarse grains. When the tensile test temperature increased to 800℃, the tensile fracture of the two grain size test steels both exhibited a transgranular+intergranular mixed fracture mode, indicating the grain boundary did not play a significant strengthening role; therefore, the strength and percentage elongation after fracture of the two grain size test steels stretched at 800℃ were basically the same.
  • Effect of Deformation Amount in Recrystallization Zone on Microstructure and Texture of X80 Pipeline Steel
    ZHOU Leilei, XIONG Xuegang, CHEN Shu, ZHOU Xiaoting, HUANG Jie, HU Xiao
    Materials For Mechanical Engineering. 2023, 47(2): 50-53,60. https://doi.org/10.11973/jxgccl202302009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    One-pass rolling deformation was carried out on X80 pipeline steel with a thermal simulator in the recrystallization zone (1 000℃), and the deformation amount was 25%, 30%, 35%, 40%, respectively. The effect of deformation amounts on the microstructure, grain misorientation, grain size and texture was studied. The results show that the microstructures of the tested steel under different deformation amounts were mainly martensite, and bainite appeared when the deformation amount increased to 35% and above. With the increase of deformation amounts, the grain misorientation distribution had no obvious change, and the grain size became finer and more uniform. Increasing the deformation amount could reduce the intensity of the recrystallization texture {110}〈110〉, meanwhile the deformation texture such as {112}〈110〉 appeared.
    • Material Properties & Application
  • Corrosion Behavior of High Corrosion Resistant Fe-Cr-Ni Medium-Entropy Alloy in H2SO4 Solution
    DING Xiao, DU Xiaojie, MA Xinyuan, XU Zhenlin, ZHANG Wei, HE Yizhu
    Materials For Mechanical Engineering. 2023, 47(2): 54-60. https://doi.org/10.11973/jxgccl202302010
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    A low-cost Fe-Cr-Ni medium-entropy alloy was developed. The corrosion resistance of the medium-entropy alloy in a 0.1 mol·L-1 H2SO4 solution was studied by comparing with that of 316L stainless steel, and the protective ability of the surface passive film was analyzed. The results show that comparing with 316L stainless steel, the test alloy had a higher free-corrosion potential and a smaller free-corrosion current density, indicating the stronger corrosion resistance, slower corrosion rates and better corrosion resistance. Comparing with those of 316L stainless steel, the content of chromium and nickel in the passive film on surface of the test alloy was higher, and the content of iron and manganese was lower; the charge transfer resistance was 8.1 times that of 316L stainless steel. This showed that a more protective passive film was formed on surface of the alloy. The test alloy had a stable single-phase face-centered cubic solid solution structure, and the degree of element segregation was low, which improved the passivation ability and reduced the corrosion sensitivity of the alloy, thus ensuring the stability and protection ability of the passive film.
  • Effect of Niobiumizing Temperature and Time on Microstructure andProperties of Niobiumizing Layer on GCr15 Steel Surface
    MENG Lingyao, SHANG Jian, ZHANG Mengjiu, XIE Aijun, ZHANG Yue
    Materials For Mechanical Engineering. 2023, 47(2): 61-66. https://doi.org/10.11973/jxgccl202302011
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    Niobiumizing layer was prepared on surface of GCr15 steel for pin shaft by solid powder packing method at different temperatures (910, 930, 950, 970℃) for different holding times (1, 2, 4, 5, 6 h). The effect of niobiumizing temperature and time on micromorphology, phase composition, microhardness, wear resistance and corrosion resistance of the niobiumizing layer was investigated. The results show that the niobiumizing layer prepared under different conditions was closely combined with the matrix. The niobiumizing layer was composed of NbC and α-Fe. With increasing niobiumizing temperature or niobiumizing time, the amount of NbC phase increased, the α-Fe phase disappeared gradually, and the thickness and microhardness of the niobiumizing layer increased. When the niobiumizing temperature was 950℃ and the niobiumizing time was 2 h, the self-corrosion potential of the niobiumizing layer was the largest and the self-corrosion current density was the smallest, indicating the corrosion resistance was the best. Considering the thickness, corrosion resistance and wear resistance comprehensively, the optimal niobiumizing process was niobiumizing temperature of 950℃ and niobiumizing time of 5 h. The niobiumizing layer prepared under this condition had relatively good corrosion resistance and small fluctuation of friction coefficients, and the average friction coefficient was only 0.22.
  • Rolling Contact Wear Characteristics of U75V Rail Repaired by Local Surfacing
    RONG Bin, WANG Yongqiang, ZHAO Huoping, LIU Shaopeng, SHEN Mingxue
    Materials For Mechanical Engineering. 2023, 47(2): 67-72. https://doi.org/10.11973/jxgccl202302012
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    The dry and wet two-stage continuous rolling contact wear tests were carried out on U75V rail samples without surfacing and with local surfacing. The rolling contact characteristics and wear behavior of the two rail samples were compared and analyzed.The results show that the adhesion coefficients of the two rail samples were both about 0.60 in the dry wear stage, and decreased sharply to about 0.25 into the wet wear stage; the adhesion coefficient of the local surfacing rail sample in the dry wear stage was slightly higher than the un-surfacing rail sample, and the wet wear stage was the opposite. The surfacing layer of the local surfacing rail sample mainly consisted of martensite and had the highest hardness. The wear surface damage of surfacing layer was slight, and no obvious cracks and plastic deformation were found. The heat affected zone was composed of ferrite, pearlite and martensite and the hardness was in the middle. After wear, the surface roughness of the heat affected zone was the largest, the plastic deformation was large and there were many cracks with large expansion angles. The non-surfacing zone was mainly composed of pearlite and the hardness was the lowest. After wear, the surface of the non-surfacing zone was flat, and obvious plastic deformation and a small amount of cracks were found.
  • Effect of Modified AlN/BN Thermal Conductive Fillers on Properties of Glass Fiber Reinforced Styrene-Butadiene Resin Composites
    MA Fengling, XU Qiaoyun, JIN Shilei
    Materials For Mechanical Engineering. 2023, 47(2): 73-78. https://doi.org/10.11973/jxgccl202302013
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    AlN and BN were modified with silane coupling agent KH570 under anhydrous conditions, and then were used as thermal conductive fillers added into glass fiber reinforced styrene-butadiene resin composites. The effect of different thermal conductive fillers on the water absorption, thermal conductivity, dielectric properties and mechanical properties of the composite was studied. The results show that filling the two thermal conductive fillers could improve the water absorption of the composite; comparing with the unmodified filler, the filling of the modified filler had a small increase in water absorption of the composite. With the increase of modified AlN content, the dielectric constant and dielectric loss of the composite increased significantly, indicating the dielectric properties decreased, and the flexural strength increased first and then decreased. With the increase of modified BN content, the dielectric constant of the composite increased, the dielectric loss decreased, and the flexural strength increased. The two modified thermal conductive fillers could improve the thermal conductivity of the composite. Compared with single component filling, modified AlN and modified BN hybrid filling had a stronger effect on improving the thermal conductivity of the composite.
  • Friction and Wear Performance of 2A12 Aluminum Alloy inDifferent States Against 17-4PH Stainless Steel
    WANG Bei, CHEN Xuli, HU Rongfang, CHEN Yanwei
    Materials For Mechanical Engineering. 2023, 47(2): 79-83,89. https://doi.org/10.11973/jxgccl202302014
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    In order to select materials for the guide rod and guide base friction pair of a certain type lock mechanism, the friction and wear performance of the friction pair of 2A12 aluminum alloy in rolling, solid solution, and solid solution and aging states against aged 17-4PH stainless steel under dry friction and grease-coated friction conditions was investigated. The results show that the tensile strength and microhardness of the 2A12 aluminum alloy in the rolling state were higher than those in the solid solution state and solid solution and aging state, but much lower than those of aged 17-4PH stainless steel. The average friction coefficient of the 2A12 aluminum alloy in the rolling state against 17-4PH stainless steel and the average volume wear rate of the aluminum alloy under grease lubrication conditions were significantly lower than those under dry friction conditions, and lower than those of 2A12 aluminum alloy in the solid solution state and solid solution and aging state under the same lubrication conditions. Under the two lubrication conditions, the wear mechanism of the three-state aluminum alloy was mainly abrasive wear, supplemented by adhesive wear, while the wear mechanism of the stainless steel was slight abrasive wear. The pairing of the 2A12 aluminum alloy in the rolling state and the aged 17-4PH stainless steel could be applied in the lock mechanism, and the friction and wear stuck could be reduced by coating grease.
    • Physical Simulation & Numerical Simulation
  • Finite Element Simulation of Influence of Residual Stress on Anti-ballistic Performance of Armor Steel Plate
    HUANG Feng, GUO Xun, LIANG Sicheng, LI Defa, GUAN Jisheng
    Materials For Mechanical Engineering. 2023, 47(2): 84-89. https://doi.org/10.11973/jxgccl202302015
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    A finite element model of 4.6 mm thick armor steel target plate shot by ordinary steel core bullet was established, and the residual stresses distributed along the plate thickness direction, which were measured by experiments, were assigned to the finite element model. The influence of the initial residual stress of the target plate on its anti-ballistic performance was studied, and the simulation results were verified by the test results. The results show that the simulation results of the back bulge height and crater depth of the target plate with initial residual stresses were consistent with the test results, and the relative errors were only 2.0% and 4.8%, respectively, indicating that the model was accurate. Comparing with those without initial residual stresses, the back bulge height and crater depth of the target plate with the initial residual compressive stress were reduced, indicating the anti-ballistic performance of the steel plate was improved. With the increase of applied residual compressive stresses, the anti-ballistic performance of the target plate showed a slight increase trend, but the increase was very small.
  • Single-Pass Hot Compression Deformation Behavior and Processing Map ofFe-0.2C-7Mn Medium Mn Steel
    WANG Yang, CEN Qiongying, WANG Weijun, ZHANG Mei
    Materials For Mechanical Engineering. 2023, 47(2): 90-95,102. https://doi.org/10.11973/jxgccl202302016
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    The hot deformation behavior of Fe-0.2C-7Mn medium Mn steel at different deformation temperatures (950-1 150℃) and strain rates (0.001-1 s-1) was investigated by single-pass isothermal compression tests on Gleeble-3500 thermal-mechanical simulator. The processing map of the steel was established by calculating the strain rate sensitivity index, power dissipation efficiency and instability parameters, and the best process window was obtained. The results show that the flow stress of the steel increased with increasing strain rate or decreasing deformation temperature. High deformation temperatures and low strain rates were conducive to the occurrence of dynamic recrystallization. The difference of dynamic recrystallization degree had great influence on strain rate sensitivity index. The instability regions at different true strains appeared in the region of high deformation temperatures and high strain rates, and basically coincided with the low power dissipation efficiency region in the power dissipation map. The best process window for the test steel was deformation temperature of 975-1 100℃ and strain rate of 0.006-1 s-1.
  • Fracture Behavior and Residual Strength Prediction of Modified Carbon/Carbon Composite after Fatigue Test
    LU Wentao, ZHANG Hongyu, LIN Weiqi, ZHAO Hua
    Materials For Mechanical Engineering. 2023, 47(2): 96-102. https://doi.org/10.11973/jxgccl202302017
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    The multi-layer plate specimens of a modified carbon/carbon composite were subjected to fatigue tests for a certain number of cycles at a stress ratio of 0.1 and -1, and then were subjected to uniaxial tensile tests to measure average residual strength of the composite. The specimen with regular penetrating cracks after fatigue was selected. On the basis of crack morphology of the specimen, a finite element calculation model was established in Abaqus software, and the critical stress intensity factor of the specimen was calculated. By using the critical stress intensity factor as a fracture criterion, the residual strength of the remaining specimens was predicted and compared with the measured residual strength of each remaining specimen. The results show that the fatigue cracks on fracture surface of the specimens were all I-type fracture mode, and the average residual strength at the stress ratio of 0.1 and -1 was 252.3 MPa and 258.8 MPa, respectively. The critical stress intensity factor of the specimen with regular penetrating cracks after fatigue was 630 MPa·mm1/2. The relative errors between the predicted residual strength and the measured values of the remaining specimens were all less than 5.5%, indicating that the prediction accuracy of this method was high.
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