20 June 2018, Volume 42 Issue 6

    

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  Research Progress on Structure Phase Transition and Physical Properties of Photoelectric Materials Under High-Pressure

  LI Shasha, ZHANG Ganghua, ZENG Tao

  Materials For Mechanical Engineering. 2018, 42(6): 1-6. https://doi.org/10.11973/jxgccl201806001

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  High-pressure technique can efficiently tune the crystal lattice and electronic state of photoelectric materials. It is a feasible route to adjust physical properties of photoelectric materials, and an important method for synthesizing new photoelectric materials. A review of the high-pressure research progress on photoelectric materials is summarized. The effects of high-pressure condition on the crystal structure, electronic configuration and physical properties of photoelectric materials are described. The mechanism of enhancing light absorption, conductivity and photoelectric performance is analyzed. The intrinsic relation between the pressure-induced structural phase transition and physical properties is discussed. The development possibility of the high-pressure research on photoelectric materials is in prospect.
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  Research Progress on Al-based Sliding Bearing Alloys

  ZENG Meiqin, LU Zhongchen, CHEN Jintian, SONG Kaiqiang, HU Renzong, ZHU Min

  Materials For Mechanical Engineering. 2018, 42(6): 7-14. https://doi.org/10.11973/jxgccl201806002

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  The research and application situation of Al-based sliding bearing alloys is reviewed in terms of type, microstructure and properties. The methods including structure refinement, alloying element addition, surface modification and dual-scale structure controlling for improving the properties of Al-based sliding bearing alloys are described. It is proposed that the new Al-based sliding bearing alloy can be designed and prepared by referring to the new preparation process and microstructure design of high-performance alloys and combining the manufacture techniques of Al-based alloy bearing shell strip.
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  Research Progress on Powder Injection Molding of Titanium and Titanium Alloy

  GUO Li, ZHAN Hao, YOU Yuping, YUE Wei

  Materials For Mechanical Engineering. 2018, 42(6): 15-21,86. https://doi.org/10.11973/jxgccl201806003

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  The characteristics and advantages of powder injection molding of titanium and titanium alloys are described in brief. The research progress on powder injection molding of titanium and titanium alloys is reviewed in terms of raw material powder, binder system, injection molding process, performance and microstructure after formation, etc. The research direction in future for powder injection molding of titanium and titanium alloys is also proposed.
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  Effect of Cu Content on Corrosion Behavior of 304 Stainless Steel in Al-12Si-xCu Alloy Melt and Its Mechanism

  ZHANG Xiaohua, YU Sirong, GUO Lijuan, YAO Qiang

  Materials For Mechanical Engineering. 2018, 42(6): 22-25,64. https://doi.org/10.11973/jxgccl201806004

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  304 stainless steel was corroded in Al-12Si-xCu (x=0, 5, 10, 15, mass fraction/%) alloy melts at 620℃ for 120 h. The effect and mechanism of Cu content on corrosion behavior of the stainless steel were studied. The results show that the corrosion rate and the corrosion layer thickness of 304 stainless steel decreased with the increase of Cu content. The surface corrosion layer was composed of inner corrosion layer and outer corrosion layer. The microhardness of outer corrosion layer increased and that of inner corrosion layer decreased with the increase of Cu content. The corrosion reaction mainly occurred between Fe, Cr atoms in the stainless steel and Al, Si atoms in the alloy melt. Cu atom was not involved in the corrosion reaction. However, the addition of Cu reduced the diffusion activation energy of corrosion reaction, resulting in the decrease of corrosion ability of the alloy melt.
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  Prediction for Creep Behavior and Creep Rupture Life of 25Cr35Ni Heat Resistant Steel on Basis of Parameter Z_c

  LIU Xinyue, CAO Tieshan, LI Huifang, CHENG Congqian, MENG Xianming, ZHAO Jie

  Materials For Mechanical Engineering. 2018, 42(6): 26-29. https://doi.org/10.11973/jxgccl201806005

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  Creep tests were conducted on 25Cr35Ni heat-resistant steel at different temperatures T and different stresses σ. The temperature and time at different creep strains were normalized by introducing parameter P. The variation of (P,σ) data point with creep strain was analyzed. Parameter Z_c was proposed to analyze the dispersion degree of data and to predict the creep rupture life with experimental data at creep strain of 5.0%. The results show that with increasing creep strain, the σ-P curve became close to the fracture curve; the value of Z_c increased rapidly and then became stable; the deviation between (P,σ) data point and the corresponding fitting curve decreased. The predicted rupture lives on basis of Z_c parameter method were close to the experimental rupture lives; the dispersion degree was relatively small.
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  Structure and Property of Aluminum-Steel Dissimilar Metal Joint by Laser Fusion Brazing with Addition of Different Alloy Powders

  LI Yan, LIU Ning, HUANG Jiankang, FAN Ding

  Materials For Mechanical Engineering. 2018, 42(6): 30-35,41. https://doi.org/10.11973/jxgccl201806006

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  5A06 aluminum alloy and ST04Z galvanized steel plates with different thicknesses were joined by laser fusion brazing after precoating with five alloy powders enriched with Si, Mg, Mn, B, Zn elements, respectively. The microstructure, tensile properties and corrosion resistance of the welded joint were studied. The results show that an intermetallic compound layer was formed at the interface of the joint; the intermetallic compound formed near the galvanized steel side was mainly composed of Fe₂Al₅ and near the aluminum alloy side was mainly composed of FeAl₃. The intermetallic compound layer obtianed by precoating with B-rich alloy powder was the thickest. All the joints fractured at the weld in a mixed mode that was dominated by ductile fracture and supplemented by brittle fracture. The tensile strength of the joint obtained by precoating Si-rich alloy powder was the largest. The corrosion resistance of the joint was the best after welded by precoating with Mn-rich alloy powder, and decreased when precoating with Mg-rich, Si-rich, and Zn-rich alloy powders in turn. The corrosion was likely to occur at the interface between intermetallic compound layer and alumium alloy.
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  Effects of Stressed Aging on TCP Phase Precipitation Behaviour of DD11 Single Crystal Superalloy

  LIU Chenguang, ZHAO Yunsong, ZHANG Jian, LUO Yushi, TANG Dingzhong, LI Chunzhi, ZHAO Zhenye

  Materials For Mechanical Engineering. 2018, 42(6): 36-41. https://doi.org/10.11973/jxgccl201806007

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  After a completely heat treatment, DD11 nickel-based single crystal superalloy was treated by stressed aging at 1 070℃ under 100 MPa and unstressed aging at 1 070℃, respectively. The precipitation behaviour of topologically close-packed (TCP) phase after aging under different conditions was analyzed. The results show that no TCP phase precipitated in the tested alloy after stressed aging and unstressed aging for 50 h. After aging for 100 h, TCP phase began to precipitate in dendrite region; the precipitation amount of TCP phase increased with the extension of aging time. For the same aging time, the precipitation amount of TCP phase after stressed aging was less than that after unstressed aging. The stress did not change chemical composition and crystal structure of TCP phase; the precipitated TCP phase was μ phase.
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  Effect of Strain Aging on Tensile Properties of X80 Large-Diameter Pipeline Steel

  PENG Ningqi, SHI Shuhua, LUO Deng, XIONG Xiangjiang, LI Zhongping

  Materials For Mechanical Engineering. 2018, 42(6): 42-45,49. https://doi.org/10.11973/jxgccl201806008

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  Aging treatment at room temperature and 200, 230, 250℃, respectively, was conducted on X80 large-diameter pipeline steel specimens after stretching to strains of 0.5%-3.5% and then unloading; the effects of tensile pre-strain and aging temperature on tensile properties of the tested steel were studied. The tested steel was made into pipe by longitudinal submerged arc welding at pipe-making expanding ratios of 0.5%-0.8%; the effect of pipe-making expanding ratio on tensile properties of the tested steel was investigated. The results show that after tensile at a certain strain and then aging or pipe-making expanding, the strain aging occurred in the tested steel; the yield strength of the tested steel increased, the tensile strength changed little, and the yield ratio increased. The pipe-making expanding ratio had bigger influences on the yield strength increment and yield ratio increment than the tensile pre-strain had. Tensile pre-strain was the main factor that improved the yield strength and yield ratio after room-temperature strain aging. The effect of strain aging at 200-250℃ on tensile properties was stronger than that at room temperature. The variation of aging temperatures between 200-250℃ had little effect on the tensile properties.
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  Effects of Piezoelectric Ceramic Powder Content and Surface-Attaching Microparticles on Properties of 0-3 Type Piezoelectric Composite

  CAI Zhenjie, YU Chenglin, ZHAO Cheng, WANG Jiaqi

  Materials For Mechanical Engineering. 2018, 42(6): 46-49. https://doi.org/10.11973/jxgccl201806009

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  With PbZr_0.49Ti_0.51O₃ (PZT) piezoelectric ceramic powder before and after ultrasonic cleaning and polyvinylidene fluoride (PVDF) as raw materials, 0-3 type PZT/PVDF piezoelectric composites containing different content of ceramic powder were prepared by flow casting method. The effects of ceramic powder content and surface-attaching microparticles on the properties of the piezoelectric composite were studied. The results show that the surface of the ceramic particles was attached with ceramic microparticles without ultrasonic cleaning, and the ceramic microparticles were almost removed after ultrasonic cleaning. The relative dielectric constant and piezoelectric constant of the piezoelectric composites increased with the increase of ceramic powder content. The relative dielectric constant and piezoelectric constant of the piezoelectric composite obtained with ceramic particles without surface-attaching microparticles were higher than those with surface-attaching microparticles; the difference values of the relative dielectric constants and of the piezoelectric constants increased with the increase of ceramic powder content.
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  Property and Microstructure Evolution of 20G Steel under High Temperature Loading

  SUN Ning, JIANG Yong, GONG Jianming

  Materials For Mechanical Engineering. 2018, 42(6): 50-54,58. https://doi.org/10.11973/jxgccl201806010

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  Tensile testing from room temperature to 850℃ and synchronous creep testing (stress of 62 MPa) and aging treatment (no stress) at 550-850℃ were conducted on 20G steel for water wall tube. The effects of temperature on tensile properties and involution of structure and properties after creep and aging were studied. The results show that the microstructures of tested steel after creep and aging were all composed of ferrite and pearlite. The applied stress improved the spheroidization of pearlite. With imcreasing temperature, the tensile strength of tested steel decreased slightly and then increased and then decreased rapidly; the yield strength decreased approximately linearly; the elongation decreased and then increased and then decreased in fluctuations. With the rise of temperature, the creep fracture time of tested steel was shortened rapidly and then became stable. The creep fracture was controlled by creep cavity nucleation at grain boundaries at 550℃ while by plasticity damage at 650℃.
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  Forming Limit for As-quenched 2A12 Aluminum Alloy

  ZHANG Peng, CHEN Minghe, YE Jianhua

  Materials For Mechanical Engineering. 2018, 42(6): 55-58. https://doi.org/10.11973/jxgccl201806011

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  As-quenched 2A12 aluminum alloy specimens with nine kinds of size obtained after aging at room temperature for 10, 20, 30 min, respectively, were bulged under three types of lubrication conditions including solid lubrication, liquid lubrication and no lubrication, respectively. The forming limit diagram of the aluminum alloy was obtained, and the effect of aging time on the formability was analyzed. The results show that the as-quenched 2A12 aluminum alloy obtained after aging for 10 min had good formability. With the increase of aging time, the forming limit curves moved down, indicating that the plasticity of the aluminum alloy decreased and the forming safety area became smaller. The appropriate natural aging time of 2A12 aluminum alloy before forming was within 10 min.
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  Preparation and Performance of Gradient WC Reinforced NiCrBSi Alloy Coating Based on Flexible Metallic Cloth Technique

  LI Haosai, JIA Yunfei, XUAN Fuzhen

  Materials For Mechanical Engineering. 2018, 42(6): 59-64. https://doi.org/10.11973/jxgccl201806012

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  WC-reinforced NiCrBSi alloy flexible metal cloth containing NiCrBSi alloy powder and WC alloy powder with volume ratios i of 1:1, 2:1, 5:1, 10:1 and 20:1 was prepared by the folding roller press technique. The metal cloth with i equal to 20:1 was placed on a 316L stainless steel substrate, and stacked with another layer of metal cloth with other i values, and then four gradient WC reinforced NiCrBSi alloy coatings were obtained by vacuum brazing. The distribution of WC particles in the coatings and the wear resistance and tensile properties of the coatings were studied. The results show that the gradient coatings were prepared successfully by controlling the thickness of metal cloth at 0.5 mm and brazing holding time of 10 min. The gradient slope characterizing the distribution of WC particles in coatings decreased with increasing i in the upper metal cloth. The gradient coatings improved the wear resistance of the substrate obviously. The wear resistance of the coating increased while the tensile strength decreased with increasing gradient slope. During the tensile process, multiple penetration cracks were produced in the coating with a relatively large gradient slope.
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  Synthesis of Graphitized Carbon Nanosheet by Molten Salt Method

  LI Junyi, LIANG Feng, TIAN Liang, ZHANG Haijun

  Materials For Mechanical Engineering. 2018, 42(6): 65-68. https://doi.org/10.11973/jxgccl201806013

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  Graphitized carbon nanosheets were prepared by molten salt method with diaminomaleonitrile as raw material, iron trichloride as catalyst precursor, and ZnCl₂-KCl as molten salt medium. The effects of reaction temperature and salt to reactant mass ratio on the phase composition, microstructure and degree of graphitization of the product were investigated. The results show that the degree of graphitization and the proportion of flake structure in the product increased with the increase of reaction temperature and salt to reactant mass ratio. When the reaction temperature was 1 000℃ and the salt to reactant mass ratio was 40:1, the graphitized carbon nanosheets with diameter of 2-10 μm and thickness of 30 nm were obtained.
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  Effects of Rolling Process Parameters on Microstructure and Tensile Properties of ZK60 Magnesium Alloy

  HUANG Biao, YAN Hongge, CHEN Jihua, XIA Weijun, SU Bin, CHENG Meixin

  Materials For Mechanical Engineering. 2018, 42(6): 69-73. https://doi.org/10.11973/jxgccl201806014

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  ZK60 magnesium alloy was rolled at different deformation temperatures (275-350℃) and different strain rates (5-25 s^-1) by a single pass rolling process with a large reduction of 80%. The effects of deformation temperature and strain rate on microstructure and tensile properties of the alloy were studied. The results show that the recrystallization volume fraction of the alloy increased with the increase of deformation temperature and stain rate. When the deformation temperature was not higher than 300℃, the recrystallization grain size decreased and then increased, the tensile strength increased and then decreased, and the elongation increased with the increase of strain rate. When the temperature was higher than 300℃, the recrystallization grain size increased and then decreased and then increased, the tensile strength decreased and then increased and then decreased, and the elongation increased with the increase of stain rate. After being rolled at 300℃ and strain rate of 10 s^-1, the as-rolled ZK60 magnesium alloy sheet had a relatively optimal comprehensive tensile property with the tensile strength of 358 MPa and the elongation of 21.5%.
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  Effect of Heat Input on Microstructure and Impact Toughness of Coarse Grain Heat Affected Zone of Welded Joint of X120 Pipeline Steel

  ZHOU Xu, YANG Jie, ZHAO Wengui

  Materials For Mechanical Engineering. 2018, 42(6): 74-77,82. https://doi.org/10.11973/jxgccl201806015

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  The welding thermal simulation tests of X120 pipeline steel were conducted with a Gleeble-3800 type thermal simulator, and the microstructure and impact toughness of the coarse grain heat-affected zone (CGHAZ) of welded joint of X120 pipeline steel under different heat input conditions were investigated. The results show that when the heat input was 10 kJ·cm^-1, the microstructure of CGHAZ was mainly composed of bainite and a small amount of low-carbon martensite with small-angle grain boundaries. As the heat input was 20 kJ·cm^-1, the microstructure of CGHAZ consisted of fine lath bainite with large-angle grain boundaries. With the increase of heat input, the microstructure of CGHAZ was composed of coarse bainite and the proportion of large-angle grain boundaries decreased. The impact toughness of CGHAZ increased first and then decreased with the heat input increasing from 10 kJ·cm^-1 to 40 kJ·cm^-1. When the heat input was 20 kJ·cm^-1, the impact toughness was the best and the fracture mode was ductile fracture. The combination fracture with ductile fracture and brittle cleavage fracture occurred when the heat input was 30 kJ·cm^-1 and the brittle cleavage fracture occurred when the heat input was 10, 40 kJ·cm^-1.
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  Effect of TiCN Addition on Properties of WC-Co Cemented Carbide

  LIAO Cong, GONG Manfeng, LI Mingsheng, LI Man

  Materials For Mechanical Engineering. 2018, 42(6): 78-82. https://doi.org/10.11973/jxgccl201806016

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  WC-Co cemented carbides were prepared by powder metallurgy and high temperature liquid sintering with TiCN content of 0,0.5wt%,1.0wt%,1.5wt%,2.0wt%, respectively. The effects of TiCN content on the micromorphology, densification performance and mechanical properties of the cemented carbide were studied. The results show that when TiCN content was no more than 1.0wt%, the grain size of the cemented carbide distributed evenly and less defects such as holes, microcracks and impurity segregation were observed; when higher than 1.0wt%, the amount of defects increased and the size bacame larger. With the increase of TiCN content, the densification performance of the cemented carbide decreased; the Vickers hardness increased and then decreased; the bending strength and fracture toughness first decreased then increased slightly and then decreased. When the TiCN content was 1.0wt%, the comprehensive performance of the cemented carbide was the best.
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  Effect of Addition Amount of Mullite Sols on Property of Corundum Castable

  HOU Qingdong, LUO Xudong, XIE Zhipeng, YU Min, YANG Mengmeng

  Materials For Mechanical Engineering. 2018, 42(6): 83-86. https://doi.org/10.11973/jxgccl201806017

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  With the mullite sols prepared by coprecipitation method as a binder, the corundum castable was sintered at different temperatures (1 100,1 300,1 500℃). The effects of addition amount of mullite sols on the phase composition, sintering performance, compressive strength at ambient temperature and microstructure of the corundum castables were studied. The results show that with the increase of mullite sols addition amount, the bulk density of the sample first increased and then decreased; the apparent porosity first decreased and then increased. The phase composition of the sample mainly consisted of corundum phase and mullite phase. With the increase of sintering temperature and addition amount of mullite sols, the content of mullite phase increased; the compressive strength at ambient temperature of the sample was improved. When the mass fraction of mullite sols was 3%, the compressive strength at ambient temperature of the sample sintered at 1 500℃ was the largest.