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Quick Search     Adv Search   2014 Vol. 24, No. 05 Published: 2014-10-10   1 Discussion on the mechanism of micro-element Hf eliminating PPBS in powder metallurgy superalloy FGH96 ZHANG Yi-wen, , LIU Jian-tao, , HAN Shou-bo, , CHI Yue, DOI: 10.13228/j.boyuan.issn1006-6543.20140025 The precipitates at prior particle boundary (PPB) are composed of carbide and small amount oxycarbide or oxide in PM superalloys. The composition and structure of carbide inside the powder, on the powder surface and on the PPB were investigated by SEM, TEM, AES techniques, etc. The mechanism of Hf eliminating prior particle boundary structure (PPBS) was discussed according to thermodynamics and diffusion theory. The results show that metastable MC type carbide MC′ rich in Ti, Nb, Cr, Mo and W elements forms on powder surface during atomization, the metastable MC′ carbide will transform into stable MC carbide during hot isostatic pressing (HIP) process. Ti and C inside powder particles will diffuse to sintering neck during HIP process, then stable MC carbide (Ti,Nb)C will form on powder particle boundaries. When micro-element Hf is added in, more and more stable MC type carbides containing Hf precipitate within powder particles, which means C and Ti elements are bound in (Ti,Nb,Hf)C carbides, suppressing the diffusion of C and Ti to sintering neck, and finally the precipitation of MC type carbides is inhibited. 2014 Vol. 24 (05): 1-7 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 8 Influence?of doping Mo into APT on preparation of?tungsten powder LI Ya-lei, TAN Dun-qiang, , YANG Xin, LU Lei, LU De-ping DOI: 10.13228/j.boyuan.issn1006-6543.20140011 The effects of different Mo-doping on the morphology and grain size of tungsten powder were studied systematically by doping ammonium paramolybdate ((NH4)6Mo7O24) solution into APT. The results show that Mo experiences the transition process of MoO3→MoO2→Mo during the reduction process, and finally exists in the form of elemental Mo; Compared to tungsten powder without doping, the surface topography of Mo-contained tungsten powder becomes irregular; and the average grain size of tungsten powder decreases constantly with the increase of Mo doping content. 2014 Vol. 24 (05): 8-11 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 12 Effects of Si content on properties of Al-Si alloy powders produced by supersonic gas atomization FU Jun-hua, ZHANG Shao-ming, XU Jun,, ZHAO Xin-ming, , SHENG Yan-wei, DOI: 10.13228/j.boyuan.issn1006-6543.20140018 Fine droplets of Al-11Si, Al-22Si, Al-27Si and Al-50Si (mass percent) were produced using supersonic high-pressure gas atomization. The particle size of powders was carried out by using an ASTM standard sieve with a vibratory shaker. Scanning electron microscopy (SEM), optical microscopy (OM) and X-ray diffraction (XRD) were used to the hierarchy of different microstructure. The [D50] (particle size on average) of Al-Si alloy powder is 57 μm, and the geometric standard deviation [δ] is less than or equal to 1.38, which is much lower than conventional gas atomization powder. The morphology of Al-Si powder is spherical or ellipsoidal sphere. There are fine particles adhered to the larger particles. The smooth finish of particles becomes worse with increase of Si content. Dendrite Al, eutectic and primary Si have been observed in the powders. The primary Si content increases and changes from particle to slice with the increase of Si content. The powder particle size has an effect on phase content, and the eutectic phase content increases with the decrease of particle size when the Si content is more than 11wt%. 2014 Vol. 24 (05): 12-18 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 3 ) 19 Study on the effect of hot isostatic pressing process parameters on the properties of 2A12 aluminum alloy powder LANG Li-hui, WANG Gang, BU Guo-liang, YAO Song, XU Qiu-yu DOI: 10.13228/j.boyuan.issn1006-6543.20140005 The properties of 2A12 aluminum alloy powder fabricated by hot isostatic pressing with different process parameters were studied. The results show that the axial shrinkage is smaller than radial shrinkage for cylindrical specimens. The properties of 2A12 aluminum alloy specimens will be sharply decreased when the temperature is too high during hot isostatic pressing, leading to cracks and defects occurring during subsequent heat treatment. The microstructure and mechanical properties of materials can be improved by adjusting the process parameters. 2014 Vol. 24 (05): 19-23 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 24 Study on sintering performance of ultrafine copper powder in conductive paste LEI Xiao-xu,,, LIU Wen-ping,,, QIN Hai-qing,,, LIN Feng,, , ZHANG Zhen-jun,,, ZHANG Jian-wei,, DOI: 10.13228/j.boyuan.issn1006-6543.20140032 In order to obtain the metal ultrafine copper conductor paste, the ultrafine copper powder was prepared by direct current arc plasma evaporation method, the crystalline structure and morphology of copper powder were characterized by X-ray diffraction(XRD), field emission scanning electron microscope (FESEM). With acrylic resin, ethyl cellulose and terpineol as organic carrier, ultrafine copper powder (mass percent of 70%) as conductive phase, the copper conducting pastes were prepared. The conductive properties and morphology of pastes under different sintering temperature (450~600 ℃) and holding time (15~60 min) were studied. The results show that the sintering process has a great influence on the conductive properties of the paste. As the sintering temperature and holding time increase, the square resistance of conductive copper paste reduces gradually, and the conductivity of the paste is enhanced. The conductive copper paste sintered at 600 ℃ for 60 min has the square resistance of 14.8 m Ω /□. 2014 Vol. 24 (05): 24-28 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 29 Effect of solution aging treatment on microstructure and properties of TC4 titanium alloy XU Jian, WANG Wen-yan,, ZHANG Hao-yin, XIE Jing-pei,, LI Luo-li DOI: 10.13228/j.boyuan.issn1006-6543.20130122 TC4 titanium alloy powder was prepared with the method of cold isostatic pressing and vacuum sintering. By adopting different solution temperature and aging temperature, the effect of heat treatment process on microstructure and properties of TC4 powder metallurgy titanium alloy was studied. The results show that tensile strength and elongation of TC4 powder metallurgy titanium alloy can reach 852 MPa and 16%, respectively. With the improvement of solid solution temperature, the tensile strength increases and the elongation decreases. With the improvement of aging temperature, the tensile strength decreases and the elongation increases. When solid solution treated at 960 ℃ for 30 min and aged at 470 ℃ for 4 h, tensile strength of the alloy reaches 1 078 MPa, and the elongation reaches 11%. 2014 Vol. 24 (05): 29-32 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 33 Investigation of grain boundary diffusion on Nd-Fe-B sintered magnet with high Dy content LI Jian,, ZHOU Lei, LIU Tao, YU Xiao-jun, LI Bo DOI: 10.13228/j.boyuan.issn1006-6543.20130105 Effect of grain boundary diffusion treatment on magnetic properties and structures of sintered Nd-Fe-B magnet with high Dy content was investigated. Using Dy vapor sorption process, the coercivity of high Dy content magnet increases from 1 713 kA/m to 2 161 kA/m without decrement of remanence or maximum energy product. Dy content of the whole magnet merely increased 0.30% (mass percent) after treatment. Further investigation of the flakes at different depths of magnet reveals that the coercivity of the flakes is similar although the Dy content in subsurface flakes is more than that in central flakes. Moreover, the coervity of all flakes is much higher than untreated ones. According to the EPMA mapping images, Dy is dispersed not only in the grain boundary but also among the main phases, and concentration of Dy-rich area is lower in untreated sample. However, for the treated samples, the concentration and the scale of Dy-rich area in grain boundary are both much larger than those of untreated ones. The coercivity of the flakes at different depth is all greatly increased due to remarkable Dy increase among the most of Nd-rich triple junction grain phases. 2014 Vol. 24 (05): 33-37 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 38 Study on preparation and properties of silicon carbide particulate reinforced aluminum matrix composites HAO Shi-ming ,, XIE Jing-pei DOI: 10.13228/j.boyuan.issn1006-6543.20140008 To study the effects of hot pressing temperature, milling process parameters and SiCp volume fraction on SiC particle reinforced aluminum composites, the SiCp/6061Al composites were prepared by powder metallurgy routes. The mechanical and physical properties of the composite were tested, and the microstructure and fracture were observed using scanning electron microscope. The results show that 540 ℃ is the suitable hot pressing temperature; with SiCp content increasing, the relative density and thermal expansion coefficient of the composite decrease, and the tensile strength increases firstly and then decreases rapidly. 2014 Vol. 24 (05): 38-43 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 44 Research status of application of spark plasma sintering on the preparation of hydrogen storage alloy DONG Xiao-ping, YANG Li-ying, PANG Yan-rong, LI Zhi-yuan, WANG Qing DOI: 10.13228/j.boyuan.issn1006-6543.20140029 The feasibility of hydrogen storage alloy prepared by spark plasma sintering (SPS) was introduced. Research progress in the application of SPS on preparation of hydrogen storage alloy was summarized according to the microstructure and hydrogen absorption/desorption properties of La-Mg-Ni system, Mg-based and Ti-V based alloy. It was pointed out that the improvement of hydrogen absorption/desorption properties of the alloy was attributed to the fact that SPS at appropriate temperature could promote the formation of new phase in hydrogen storage alloy and control the grain size of the alloy. 2014 Vol. 24 (05): 44-47 [Abstract] ( 3 ) HTML (1 KB)  PDF  (0 KB)  ( 1 ) 54 Discussion of the powder metallurgy products and the auto parts market YAN Lian, LI Sen-rong, ZHOU Xu-lin DOI: 10.13228/j.boyuan.issn1006-6543.20140020 In recent years, the development of auto industry drives the development of powder metallurgy. The technical characteristics of powder metallurgy products, as well as the application of new material products in auto industry were briefly introduced. The development trend of high value-added powder metallurgy parts production was also suggested. 2014 Vol. 24 (05): 54-58 [Abstract] ( 5 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 59 Application of UG_CAE technique during the whole sizing die design for synchronizer gear hub JIANG Zheng DOI: 10.13228/j.boyuan.issn1006-6543.20130107 With the low-end market to high-end market transformation of automobile industry in China, the precision requirement of auto parts is also increased to ensure the mechanical and physical properties. Coordination characteristics among assembly parts is also facing new requirements, for example, the relative sliding between the synchronizer gear hub and tooth sleeve should be smooth, without clamping stagnation phenomenon, to ensure the smooth shifting in the car running process. In order to meet this requirement, the size precision of synchronizer gear hub and tooth sleeve, such as tooth shape, tooth and pitch error, has to be controlled precisely to ensure the appropriate assembly clearance and its uniformity. It often needs more than once experiments to meet the requirements of product design, leading to waste of resources, increased costs and long cycle of products, and then the competitiveness of products is greatly weakened. Using UG_CAE technique, the influence of shaping modes on the deformation of synchronizer gear hub was expected, the product development cycle was shortened, and the product quality was ensured. 2014 Vol. 24 (05): 59-62 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 63 Virtual assembly of powder metallurgy gear forming mould based on Cult3D ZHU Xiao-long, WANG Jun-ze, LIU Yu DOI: 10.13228/j.boyuan.issn1006-6543.20140045 In order to realize interactive display of the powder metallurgy gear forming mould on web, and make comprehension and repair of the mould become more convenient for users, interactive and dynamic display of operating principle and assembly relation for the powder metallurgy gear forming mould on the network was provided by 3D model of the mould with the software of SolidWorks and Cult3D. The dynamic interactive display of virtual assembly for the powder metallurgy gear forming mould was realized. 2014 Vol. 24 (05): 63-67 [Abstract] ( 0 ) HTML (1 KB)  PDF  (0 KB)  ( 2 ) 48 Research progress of WC-Co cemented carbides with three kinds of special microstructure LEI Chun-peng , , ZHAO Yong-jun , LIU Gang , TANG Jian-cheng DOI: 10.13228/j.boyuan.issn1006-6543.20130097 Research on powder preparation methods and sintering technologies for WC-Co cemented carbides with excellent performance has received wide attention, however, the influence of powder morphologies on properties of cemented carbides is also a lack of in-depth study. The powder morphologies, application and preparation of WC-Co cemented carbides with special microstructures, such as ultrafine/nano structure cemented carbide, middle/coarse grain cemented carbide and plate-like grain cemented carbide, were reviewed. 2014 Vol. 24 (05): 48-53 [Abstract] ( 1 ) HTML (1 KB)  PDF  (0 KB)  ( 1 )

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