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Quick Search     Adv Search   2021 Vol. 31, No. 03 Published: 2021-06-10   1 Materials development of powder metallurgy valve seat inserts and their failure analysis Hot! CHENG Jigui，CHENWenchao，CHEN Pengqi DOI: 10.13228/j.boyuan.issn1006-6543.20200301 Valve and valve seat inserts (VSIs) compose a friction pair, and are important components of the internal combustion engines. The valve seat inserts are vulnerable to wear, which has important influence on the performance of the engine. This paper introduces the working environment and service properties of VSIs, the types and development status of the VSIs materials, with emphasis on the types and characteristics of powder metallurgical VSIs materials. The failure modes and mechanism of the VSIs were also overviewed, and a prospect of the research and development tendency of the VSIs was presented. 2021 Vol. 31 (03): 1-9 [Abstract] ( 9 ) HTML (1 KB)  PDF (1805 KB)  ( 7 ) 10 Research on preparation progress of porous NiO with high activity of reduction reaction Hot! QU Yanjie，ZHONGWuye，ZHENG Jianping，GUO Zhimeng DOI: 10.13228/j.boyuan.issn1006-6543.20200098 Preparation progress of porous NiO with high activity of reduction reaction is researched, which includes pore-forming, ball-milling, and sintering. The reaction rate and conversion are discussed about the reaction of NiO reduced with CO by recording the total pressure and CO2 concentration of the reaction system. The optimum preparation progress of porous NiO granular material with high activity of reduction reaction is achieved. And it is verified that the porous NiO can react with CO at high rate before conversion rate reaches 93%. 2021 Vol. 31 (03): 10-17 [Abstract] ( 8 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 18 Effect of flake graphite content on the properties of copper-based powder metallurgy materials for subway collector boots Hot! LIU Xishuang，XU Xiongfei，WANG Xiufei，WEN Guofu，YIN Cailiu，FENG Chiyuan DOI: 10.13228/j.boyuan.issn1006-6543.20200252 Copper based powder metallurgy friction materials with flake graphite content of 2%, 3%, 4%, 5% and 6% were prepared by powder metallurgy technology and their mechanical properties were measured.The MM- 1000III friction and wear testing machine was used to test its friction and wear performance.Scanning electron microscopy (SEM) was used to observe the microstructure of the friction surface and impact section and analyze the mechanism of friction wear and impact fracture.The results show that the impact toughness, Brinell hardness and tensile strength decreases with the increasing of flake graphite content, and the resistivity of the material increases. With the increasing of flake graphite content, the friction coefficient and wear rate of the material decrease under the same pressure and inertia.The impact toughness of the material decreases with the increasing of flake graphite content. The formation of impact section dimples is affected by the number of tissue pores and dislocation plug. 2021 Vol. 31 (03): 18-24 [Abstract] ( 5 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 25 Preparation and research on temperature stability of Nd-Fe-B magnets with high Curie temperature Hot! LI Dong，DONG Shengzhi，XU Jiyuan DOI: 10.13228/j.boyuan.issn1006-6543.20200106 In this paper, the magnetic properties, density and grain size of (PrNd)27.8CoxDy3FebalB0.97(x=20, 25) magnets were investigated to explore the best heat treatment process, and the corresponding temperature stabilities were compared with commercial magnet 40M. The experimental results show that high Co content enhances the Curie temperature significantly while the intrinsic coercive force decreases in some extent. The temperature stability (temperature coefficient and irreversible flux loss) not only depend on the Curie temperature, but also are affected by the coercive force. Compared with the commercial magnet 40M, temperature coefficient and irreversible flux loss of the magnet with high Curie temperature has been significantly improved. 2021 Vol. 31 (03): 25-31 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 32 Influence of substrate temperature on magnetic properties of low coercivity Fe-Si thin film Hot! LI Tongkui1，2，ZHOU Chunxia1，2，YAN Pengfei2，3，YAN Biao1，2 DOI: 10.13228/j.boyuan.issn1006-6543.20210056 In this paper, Low coercivity soft magnetic films were obtained by DC magnetron sputtering at different temperatures. When the substrate temperature is higher than 140 ℃, Si in the substrate diffuses into the film, the magnetic moment of the film is diluted, the coercivity increases and the saturation magnetization decreases. The results of VSM show that the coercivity decreases first and then increases with the increase of substrate temperature. When the substrate temperature is 140 ℃, the soft magnetic properties of the sputtered Fe-Si films are better. The coercivity Hc reaches the lowest value of 1 Oe and the saturation magnetization Ms is 716 emu/cm3. The initial magnetization curve shows that when the applied magnetic field is 20 Oe, the magnetization is 670 emu/cm3 and the susceptibility is 421.5. 2021 Vol. 31 (03): 32-38 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 39 Effect of trace added Ni on sintering behaviors and physical properties ofW-Cu nano-composite Hot! LU Shangzhi，ZHANG Chunrui，GAO Bingxiang，ZHANG Jianghai，GUO Yajie DOI: 10.13228/j.boyuan.issn1006-6543.20200170 Tungsten-copper nanocomposite powder was prepared by chemical coprecipitation combined with hydrogen reduction process, and the rapid sintering ofW-Cu nanocomposite powder was realized by spark plasma sintering technology at different temperatures. The effects of trace active agent Ni addition on the morphology, sintering behavior and alloy properties of W-Cu composite powders were studied. The results show that the addition of a trace amount of of Ni (0.5%) makes the particle size of the composite powder grow more fully and the particle distribution is more uniform; When the sintering parameters are the optimal, with the temperature of 970 ℃, pressure of 120 MPa, and heat preservation time of 10 min, the average grain size of W particles in the W-20%Cu-0.5%Ni alloy is 362.9 nm , the relative density is 97.7%, the porosity is 2.1%, the microhardness is 474.74HV, the above properties are better than theW-20%Cu alloy prepared by the same SPS process. 2021 Vol. 31 (03): 39-44 [Abstract] ( 4 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 45 Effect of Pb doping on the structure and thermoelectric properties of Mg3Sb2 prepared by SPS Hot! ZHAI Xiuli，XIN Yunxia DOI: 10.13228/j.boyuan.issn1006-6543.20200209 The Mg3Sb2Pbx compound was prepared by Pb doping with Mg3Sb2 and selected as the test substrate for semiconductor, and the changes of carrier effective mass and mobility caused by Pb doping were analyzed. The results show that Pb doping in Mg3Sb2 is better in the range of 0.02-0.03. The Mg3Sb2Pbx samples forms the dense tissue, the density of which reached more than 95% of the theoretical density, and forms similar fracture morphology. Each element of Sb, Mg and Pb presents a uniform distribution state without element partial polymerization, so it can be inferred that the tissue composition of each part of the sample is uniform and has similar properties. After increasing Pb content, the sample obtains higher conductivity and Seebeck coefficient decreases continuously. With the increasing of Pb doping, the carrier mobility of Pb decreases. With the temperature increasing gradually, the sample obtained a larger ZT than it without doping. The addition of Pb can improve the performance of electric transport and obtain higher ZT. 2021 Vol. 31 (03): 45-49 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 50 Effect of Sn content on microstructure and mechanical properties of Al-Mg alloy for automotive powder injection molding Hot! MEN Dianyong，LI Minggang DOI: 10.13228/j.boyuan.issn1006-6543.20190256 The Al-Mg alloy for automotive lightweight were prepared by the powder injection molding. The effects of Sn content and solution treatment on microstructure and mechanical properties of Al-Mg alloy were studied. The results show that the density of Al-Mg alloy sintered at 600~620 ℃ is higher than 98%. With the increasing of Sn content, the density of Al-Mg alloy increases monotonically. When the Sn content is greater than 1%, the increase is not obvious. At this time, more white particles are formed in the grain boundary area, mainly Sn accumulation. Sn element can play a greater mechanical strengthening effect in the solution treatment process, the solution treatment can significantly improve the tensile strength of Al-Mg alloy. The tensile strength of solid solution alloy increases first and then decreases with the increasing of Sn amount. When 1% Sn is added, the tensile strength reaches the maximum. The pore structure are formed in the solid solution tissues, and the spots phenomenon are appeared, and the number of spots decreased with the increase of Sn content. When the amount of Sn is less than 1%, higher mechanical strength can be obtained, but too much Sn will cause the decreasing of mechanical strength of aluminum alloy. 2021 Vol. 31 (03): 50-54 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 55 Study on surface modification and properties of magnesium alloy sports instruments Hot! XUE Haitao，LIU Xiaofeng，QIN Keli DOI: 10.13228/j.boyuan.issn1006-6543.20190071 Surface modification of AZ31B alloy was carried out by magnetron sputtering and micro-arc oxidation. The morphology, corrosion resistance and wear resistance of AZ31B alloy matrix, magnetron sputtering Zr film and micro-arc oxidation ZrO2 film were compared and analyzed. The results show that the magnetron sputtered Zr film has a good metallurgical bonding with AZ31B alloy matrix, there are no abnormal pore or microcrack at the interface, the thickness of the film is about 4 μm, and there are volcanic jet micropore with random size of 2-10 μm on the surface of the micro-arc oxidation film. The surface hardness of ZrO2-AZ31B sample is 332.91HV, which is 422% higher than that of AZ31B alloy matrix and 328% higher than that of Zr-AZ31B sample. The open-circuit potential of Zr film and ZrO2 film is more stable than that of AZ31B matrix from the beginning of immersion to the end, and the open-circuit potential of ZrO2 film is the most positive at the same time. The corrosion potential of Zr film and ZrO2 film is more positive than that of AZ31B alloy matrix, and the corrosion current density is obviously reduced, the corrosion resistance of AZ31B alloy can be improved by magnetron sputtering and micro-arc oxidation modification, and ZrO2-AZ31B specimens have the best corrosion resistance; compared with AZ31B alloy matrix and Zr film specimens, ZrO2 film specimens have the shallowest wear trace depth, the smallest wear trace width and the smallest wear trace volume; the order of specific wear rate from high to low is: AZ31 alloy matrix > Zr film > ZrO2 film, micro-arc oxidation ZrO2 film has relatively better wear resistance, whether in dry friction or in simulated human sweat wet friction conditions. 2021 Vol. 31 (03): 55-62 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 63 Properties of Nd/TiC wear resistant coating on AZ91D magnesium alloy by argon arc cladding Hot! WANG Bohua，ZHANG Lijie DOI: 10.13228/j.boyuan.issn1006-6543.20200278 The single pass cladding of AZ91D magnesium alloy was carried out by using neodymium powder and tic powder as alloy powder. The results shows that the surface of Nd/TiC coating is mainly composed of eutectic structure, network structure and cellular structure, and the surface is smooth and delicate. XRD analysis shows that the crystal phase composition is in line with the experimental expectation. When the content of alloy powder is 30%, the average microhardness of the coating is about 587HV. The friction coefficient of the coating is stable at 0.48±0.05, and the wear rate is 3.64×10-10 m3 ·m-1 under 5 N and 13.68×10-10 m3 ·m-1 under 30 N. The wear morphology of the coating is slightly scratched at room temperature, and spalling pits with different depth are observed at high temperature. When the content of coating powder is 30%, the mass loss of the coating’s dynamic erosion is only about 30% of that of substrate, which has good erosion resistance in petroleum medium. 2021 Vol. 31 (03): 63-67 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 68 Research progress of nanoconfinement and ternary modification methods of Li- Mg-B-H hydrogen storage system Hot! HU Chuan，ZHOU Zhangwei，LIU Chunrong，ZHAOWang，LI Ping，QU Xuanhui DOI: 10.13228/j.boyuan.issn1006-6543.20200234 This article summarizes the latest research progress of Li-Mg-B-H hydrogen storage system which has unstable reaction in recent years. In view of the high hydrogen absorption and desorption temperature and slow kinetic performance of the composite system, especially the long incubation period between the two hydrogen release steps, the nanometerization and ternary system modification methods used in recent years are summarized and the future research and development of the system are prospected. 2021 Vol. 31 (03): 68-75 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 76 Study on effects of cross pressing forming process for the deformation of vertical loading inserts Hot! YUAN Caiyun，LI Jun，FENGWen，HE Haijun，CHI Yiyi DOI: 10.13228/j.boyuan.issn1006-6543.20210016 Deformation control of blank is one of the important quality indicator for mold forming process. In this paper, the CNC vertical loading insert was taken an example to analyze difference between transverses hole forming process and cross pressing forming process. Combined with the mold forming theory, the powder uniformity during cavity filling and the powder compression ratio during pressing were analyzed theoretically. The results show that powder uniformity during cavity filling and the uniformity of relative density in each area of the compaction formed by cross pressing forming process are better than that by transverse hole forming process. The dimension accuracy such as V-shape β angle, aperture roundness and flatness of positioning plane of the sintered blank by cross pressing forming process are higher. The deformation of insert is smaller, and there is no appearance defect such as crack in the center hole. 2021 Vol. 31 (03): 76-80 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 81 Effect of rolling method on mechanical properties of molybdenum Hot! WANG Guangda，XIONG Ning，LIU Guohui DOI: 10.13228/j.boyuan.issn1006-6543.20190172 The sintered billet of pure molybdenum was prepared by powder metallurgy, and the desired size and properties were obtained by rolling deformation. Rolling process is very important to the properties of molybdenum plate. By comparing and analyzing the differences of properties and microstructures between three kinds of cross rolling and unidirectional rolling, it is found that cross rolling can significantly improve the anisotropy and the material have excellent comprehensive properties. With the increasing of the temperature, the effect of rolling process on the properties of molybdenum sheet is obviously weakened. The recrystallization and growth of grains make the high temperature properties of molybdenum sheet the same. 2021 Vol. 31 (03): 81-84 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 85 The effect of cross rolling on the elevated temperature properties of pure molybdenum Hot! WANG Guangda，XIONG Ning，LIU Guohui DOI: 10.13228/j.boyuan.issn1006-6543.20190096 Rolling have an important influence on the properties of pure molybdenum plate. The effects of cross rolling on the microstructure, high temperature mechanical properties and fracture morphology of molybdenum sheet after heat treatment were studied. The results show that different cross rolling processes can improve the anisotropy of molybdenum sheet, the effect of different cross rolling processes on high temperature properties of molybdenum sheet is different, the recrystallization behavior is different too. 2021 Vol. 31 (03): 85-87 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 88 Study on friction and wear properties of tungsten-rhenium alloys at 600 ℃ Hot! DONG Di，WANGWeibing，XIONG Ning，LIU Guohui，WANG Chengyang， ZHAO Dalong DOI: 10.13228/j.boyuan.issn1006-6543.20190219 In this study, high temperature friction and wear property of W5Re and W25Re alloy which prepared by powder metallurgy were tested By means of electron probe, LEICA three- dimensional optical microscope, SEM and EDS，the composition, roughness and microstructure of wear surface were gained. The results show thal W25Re alloy has excellent friction and wear resistance at high-temperature . 2021 Vol. 31 (03): 88-93 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 94 Analysis of surface streaking on tungsten infiltrated copper gas rudder Hot! ZHANG Baohong，ZENG Qingxiang，LIU Qing，GUO Yingli，LIN Bingtao， SUN Xiaoxia DOI: 10.13228/j.boyuan.issn1006-6543.20200166 Taking tungsten infiltrated copper gas rudder (W-7Cu) as the research object, stripes with a width of 1~ 2 mm appeared during the machining process were analyzed. The results show that the stripes on the machined surface are a localized densified structure of tungsten skeleton produced by high- temperature sintering of tungsten. Non-destructive testing methods can not detect the stripes, and the stripe are not internal defects that can be identified by non-destructive testing.The presence of stripes has an effect on the local mechanical properties, but has little effect on the overall performance, and the performance meets the technical requirements. 2021 Vol. 31 (03): 94-98 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 99 Analysis of the causes for the dispersion of mechanical properties of a tungsten alloy counterweight Hot! ZUOWei，GUO Yin，YANG Lin，ZHANG Zhen，WANG Xinlei，SUN Xiaoxia DOI: 10.13228/j.boyuan.issn1006-6543.20200185 This paper takes 97W-2Ni-1Fe tungsten alloy for counterweight as the research object. The phenomenon reappearance analysis and verification are carried out for the large dispersion of the mechanical properties of the body sampling during the product reinspection process, which provides a reference for subsequent failure analysis and quality control of tungsten alloy. The test results show that the sintering temperature is the fundamental reason that affects the discreteness of the properties of the tungsten alloy material. As a result, the tungsten particles inside the structure grow abnormally, the structure is uneven, the bonding layer becomes thicker, and the tensile strength of the material decreases. Fractures are dominated by tungsten- tungsten interface separation, which is a typical brittle fracture. 2021 Vol. 31 (03): 99-103 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 104 Effect of molybdenum powder morphology on the performance and microstructure of molybdenum infiltrated copper products Hot! GUO Yingli，ZHANG Baohong，LIN Bingtao，LI Qiang，XIE Yina，SUN Xiaoxia DOI: 10.13228/j.boyuan.issn1006-6543.20200194 Molybdenum infiltrated copper products were prepared by molybdenum powder. The reasons for the low qualified rate of ultrasonic primary inspection of a batch of products were analyzed, and the effects of different morphology of molybdenum powder on the microstructure and properties of molybdenum infiltrated copper products were studied. The results show that different powder morphology has little effect on the mechanical properties at room temperature and high temperature, which can be ignored. The existence of pits, hollows, etc. in the powder may directly lead to defects such as holes in the sintered body. The existence of agglomerates will affect the uniformity of molybdenum skeleton, and also affect the uniformity of infiltrated copper liquid, and then affect the results of ultrasonic flaw detection. Suggestions on raw material control of molybdenum-copper infiltrated products which require ultrasonic testing are put forward. 2021 Vol. 31 (03): 104-110 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 )

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