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Quick Search     Adv Search   2015 Vol. 25, No. 01 Published: 2015-02-15   1 Application of powder metallurgy in CNTs reinforced metal-based composites YI Jian-hong,, BAO Rui DOI: 10.13228/j.boyuan.issn1006-6543.20140085 Carbon nanotubes (CNTs) have excellent mechanical, physical and chemical properties，which are the ideal reinforced composite materials. The application for preparation of CNTs reinforced metal matrix composite by powder metallurgy method at home and abroad in recent years was reviewed. The progress of CNTs/metal matrix composite powder and block materials was described in detail. Finally, the application foreground was prospected. 2015 Vol. 25 (01): 1-7 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 8 Current research status and development trend of advanced thermal barrier coatings Lü Yan-hong, ZHANG Qi-fu DOI: 10.13228/j.boyuan.issn1006-6543.20140057 The advanced thermal barrier coatings can be divided into the following categories, namely doped ceramics of yttria-stabilized zirconia coating, ABO3 ceramics with perovskite structure, A2B2O7 ceramics with pyrochlore or fluorite structure, MMeAl11O19 ceramics with magnetoplumbite structure and yttrium aluminitum garnet. The research status of the advanced thermal barrier coatings was summarized, and the existing problems and development tendency were discussed. 2015 Vol. 25 (01): 8-13 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 14 Preparation of ultrafine W-Ag composite powders by sol-gel method ZHANG Fu-bin, HU Yan-ling, HU Ye-qi, XU Long-shan, HU Bai-xin DOI: 10.13228/j.boyuan.issn1006-6543.20140068 W-20%Ag (mass percent) composite powders were prepared by sol-gel method with AgNO3 and (NH4)6H2W12O40·5H2O as raw materials and citric acid as a chelating reagent．The decomposition process of dry gel was checked by means of thermogravimetric analysis. The phase composition, particle size and morphology of the powders were studied by XRD and SEM. The results show that precursor powders undertake a series of decomposing and compound reactions during calcination and reduction. With the increasing of temperature, the phase composition, particle morphology, as well as particle size of the powder change apparently. The granularity of the W-20%Ag (mass percent) composite powders is about 200-400 nm． 2015 Vol. 25 (01): 14-18 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 19 YAG powders prepared by improved co-precipitation YANG Li-rong, LIU Chang,, LI Xiao-wu,, WEI Cheng-fu,ZHANG Lin, TANG Jie,, CHEN Chun-mao DOI: 10.13228/j.boyuan.issn1006-6543.20140055 YAG precursor powders were prepared via improved co-precipitation method with mixture of aluminum nitrate and yttrium nitrate as raw material and ammonium hydrogen carbonate as precipitant. The dispersant agent was PEG1000. The structure and properties of powder were investigated by thermal gravimetric analyzer, particle size analyzer, X-ray diffraction. The results show that YAG powders with high purity can be prepared by improved co-precipitation. The aging time has a dramatic effect on the powders. When aged for 12 h, the YAG powder has higher purity and more uniform particle size distribution. The specific surface area is 367.79 m2/kg and the average particle size is 7.52 μm. 2015 Vol. 25 (01): 19-22 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 23 Study on preparation of spherical silver powders with polyvinylpyrrolidone as dispersant XIE Wei,, ZHENG Ya-ya,, KUANG Jia-cai, XU Hua, DENG Ying-jun DOI: 10.13228/j.boyuan.issn1006-6543.20140039 The spherical silver powders with uniform particle size were prepared using silver nitrate as raw material, ascorbic acid as reducing agent, polyvinylpyrrolidone (PVP) as dispersant through the method of liquid reduction. The effects of mass ratio of PVP/AgNO3 on the microstructure, crystal structure, particle size distribution and resistivity of spherical silver powders were investigated. Results show that the silver particles tend to be more spherical, the particle size gets smaller and more uniform, and the resistivity of the powder increases, while the crystal structure remains unchanged with the mass ratio of PVP/AgNO3 increasing. The resistivity of silver powder is 367 Ω·mm2/m when the mass ratio of PVP/AgNO3 is 0.6. 2015 Vol. 25 (01): 23-27 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 28 Effect of hot extrusion on microstructure and properties of SiCp/6061Al composites CHEN Chao-qun,, YANG Yong-shun,, YANG Xi,, REN Xin-lei, DOI: 10.13228/j.boyuan.issn1006-6543.20140028 The SiCp/6061Al composites were prepared by powder metallurgy method, and then were hot extruded. Microstructure of the composites was observed by optical microscope and scanning electronic microscope. The physical and mechanical properties were also examined. The results show that the densities and mechanical properties are increased; the distribution of SiC particles is more uniform after hot extrusion, which is consistent?with the direction of extrusion force. 2015 Vol. 25 (01): 28-31 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 32 Effect of adding copper powder on the properties of GCr15 powder from grinding chips ZHONG Hong-hai, SHEN Wen-hao, SHAN Na, YU Ya-lan, NI Di, JIANG Yang DOI: 10.13228/j.boyuan.issn1006-6543.20140047 The compaction law of GCr15 bearing steel powder was analyzed. Influences of Cu addition on the green density, spring-back, sintered density and performance were explored, and the effect of pressure and sintering temperature on the density and hardness was studied. The results show that the compaction law of GCr15 bearing steel powder is accorded with Huang Pei-yun compaction equation. The green density increases with increasing pressure lower than 1 300 MPa, and the sintered density increases with increasing sintering temperature lower than 1 300 ℃. Addition of copper can improve the green and sintered density, but has little effect on the spring-back. For the GCr15 compacts without copper, the green density of 6.60 g/cm3 and spring-back of 1.73% are obtained when the pressure is 1 200 MPa, and after sintered at 1 150 ℃ for 2 h in H2 atmosphere, the sintered density is 6.91 g/cm3. While the compacts of GCr15 bearing steel powders with 5% (mass percent) copper powder sintered at 1 300 ℃ for the same time and in the same atmosphere, the density of 7.23 g/cm3 and the hardness of 36.3 HRC are achieved. 2015 Vol. 25 (01): 32-37 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 38 Study on the influence of different processes on the vacuum gas atomized Ni powder particle size YU Yong, ZENG Gui-yu, XIAO Ming-qing, LE Chen,, OU Jian-xiong DOI: 10.13228/j.boyuan.issn1006-6543.20140059 Nickel powders were produced by close-coupled gas atomization. The effects of atomization pressure, nozzle inner diameter and melting temperature on the particle size were studied. The results show that the particle size reduces with the increasing of atomization pressure or melting temperature, or the decreasing of nozzle inner diameter. The optimum parameters for the preparation of fine nickel powders are as follows: atomization pressure of 5 MPa, nozzle inner diameter of 4.5 mm and melting temperature of 1 600 ℃. The powders produced under this condition are mainly spherical. 2015 Vol. 25 (01): 38-41 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 42 Effects of thermal induced porosity on mechanical properties of PM superalloy ZHANG Guo-xing,, HAN Shou-bo,, SUN Zhi-kun, DOI: 10.13228/j.boyuan.issn1006-6543.20140031 Thermal induced porosity (TIP) is one of the three major defects in PM superalloy, which has a significant adverse effect on the alloy performance. PM superalloy parts with TIP were analyzed. The microstructure was observed and the effects of porosity on mechanical properties of the alloy were also studied. The results show that the main cause of TIP is residual gas in hot isostatic pressing canning for the PM superalloy parts with large size and complex shape. The tensile properties under room temperature and impact toughness are greatly reduced with the increase of porosity. When the porosity increases from 0.072% to 1.744%, the tensile strength and yield strength decrease by 28.37% and 17.39%, respectively, while the elongation and reduction of area decrease by 62.0% and 62.5%, respectively. At the same time, impact energy decreases by 58.18%. TIP becomes the source of crack during heat treatment, causing the alloy cracks or cracking. 2015 Vol. 25 (01): 42-45 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 46 Application of HIP technology in improving casting densification ZHANG Dian-xi, ZHOU Shi-yun, ZHANG Zai-yu, YANG Xiu-Fan, CHEN Zhao-song DOI: 10.13228/j.boyuan.issn1006-6543.20140033 Hot isostatic pressing (HIP) can realize the casting internal loose creep diffusion by high temperature and high pressure, to achieve densification purposes, so that the mechanical properties of the casting are improved significantly, and the safety and reliability of casting are improved greatly. The development and principle of HIP technology were briefly introduced. The application of HIP in densification processing of titanium alloy, superalloy, aluminum alloy and magnesium alloy was summarized. 2015 Vol. 25 (01): 46-48 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 49 Research progress of the dispersion strengthening diamond tool matrix NING Xin-yuan, WANG Li-min,, LIU Xiang-qing, DOI: 10.13228/j.boyuan.issn1006-6543.20140067 The mechanism and performance feature of dispersion strengthening was introduced. The application potential of dispersion strengthening was discussed combined with the problems existing during the using of diamond tools. The research status was also stated. 2015 Vol. 25 (01): 49-53 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 54 Improve the consistency of components by using an improved bonded mix TAN Zhao-qiang, WANG Hui, WANG Hao, CHEN Li-fang, ZHANG Xuan DOI: 10.13228/j.boyuan.issn1006-6543.20140064 One of the main advantages of PM technology is its ability to make near net shape components with a cost efficient process. However, variation in the dimensions of products after compaction and sintering that often calls for sizing or machining to reach the desired tolerance class. Bonded organic mixes have been developed to improve the consistency by reducing the segregation of elements in mix and improving the filling characteristics. An improved bonded mix combined with a recently developed lubricant, was evaluated by indutrial production of a complex shape component with tight tolerances. Many benefits of dimenisonal consistancy, weight precision, better lubrication as well as clean surfaces by using the improved bonded mix were presented. 2015 Vol. 25 (01): 54-59 [Abstract] ( 2 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 60 Process analysis and mold design improvement of clutch detaching cam ZENG Jin-yan, SHEN Hua, ZHAO Shan-jie, CAI Hu-lei DOI: 10.13228/j.boyuan.issn1006-6543.20140049 The problems that long production process, slow progress, low accuracy and precision of machining, complex product testing of clutch detaching cam produced by powder metallurgy method were analyzed. The clutch detaching cam mold design was improved and the process was optimized. The radial hole can be formed by one time, the accuracy and product quality are improved, the production process is shortened, and the unqualified products are reduced. 2015 Vol. 25 (01): 60-62 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 3 )

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