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Application of the gel casting process in iron powder metallurgy

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Journal of University of Science and Technology Beijing 2006年第1期13卷 29-33页

作者： chengchang jia Weihua Liu Zhimeng Guo Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

The effects of various gel casting process parameters such as the dispersant and solid loading on the rheology of Fe slurries, molding, and sintering behaviors were studied. The relationship between solid loading and viscidity in the process of iron base powder metallurgy was researched to obtain better microstructure and properties. The results showed that the viscosity of Fe slurries is obviously reduced with the increase of the dispersant. The suitable parameters are as follows： the solid loading is 61% and sintering temperature is 1180℃. Iron parts with relatively high density and better properties were obtained by the gel casting process.

关键词： gel casting Fe powder metallurgy rheology

Phase Equilibria in Ni Rich Region of Ni-Al-Fe System

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International Journal of Minerals,Metallurgy and Materials 2000年第4期14卷 277-281页

作者： chengchang jia Kiyohito Ishida Taiji Nishizawa Material Science and Engineering School University of Science and Technology BeijingBeijing 100083China Engineering faculty Tohoku UniversitySendai 980Japan

The phase equilibria between γ, α, γ' and β in the Ni-rich region of the Ni-Al-Fe system were investigated by the diffusion couple method and thermodynamic models. The thermodynamic parameters were assessed based on experimental results and thermodynamic data. Moreover, the system's phase equilibria from 900 to 1 300℃ were calculated with regular solution and sublattice models, and it is shown that the theoretic results agree well with experimental phase diagram data.

关键词： Superalloys

Influence of process control agents on the performance of Ni_3Al by mechanical alloying

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Rare Metals 2008年第6期27卷 648-651页

作者： LIAN Jiqiong MENG Jie jia chengchang School of Materials Science and Engineering University of Science and Technology Betting Beijing 100083 China Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

The influence of process control agents （PCAs） on the mechanical properties of Ni3AI intermetallic compounds by mechanical alloying was investigated in order to develop oxide deposition reinforced intermetallics. The PCAs in mechanical alloying were pure ligroin, 75 vol.% ligroin ＋ 25 vol.% alcohol, 50 vol.% ligroin ＋ 50 vol.% alcohol, 25 vol.% ligroin ＋ 75 vol.% alcohol, and pure alcohol. The normal composition is Ni-22.9at.%Al-0.5at.%B, the ball-to-powder weight ratio is 10：1, and the milling time is 30 min. Then, the powders were sintered by spark plasma sintering under 40 MPa for 5 min at 1000℃. The results show that a higher bending strength and a higher hardness were obtained when the PCAs were 75% ligroin ＋ 25% alcohol in mechanical alloying. The bending strength is about 2700 MPa and the hardness （HV） is more than 6 GPa.

关键词： intermetallic compounds mechanical properties mechanical alloying process control agent spark plasma sintering

Effect of solution cooling rate on the γ′ precipitation behaviors of a Ni-base P/M superalloy

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Journal of University of Science and Technology Beijing 2008年第6期15卷 729-734页

作者： Gaofeng Tian chengchang jia Ying Wen Benfu Hu School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

The effect of cooling rate on the cooling γ′ precipitation behaviors was investigated in a Ni-base powder/metallurgy （P/M） superalloy （FGH4096）. The empirical equations were established between the cooling rate and the average sizes of secondary and tertiary γ′ precipitates within grains and tertiary γ′ precipitates at grain boundaries, as well as the apparent width of grain boundaries. The results show that the average sizes of secondary or tertiary γ′ precipitates are inversely correlated with the cooling rate. The shape of secondary γ′ precipitates within grains changes from butterfly-like to spherical with the increase of cooling rate, but all the tertiaryγ′ precipitates formed are spherical in shape. It is also found that tertiary γ′ may be precipitated in the latter part of the cooling cycle only if the cooling rate is not faster than 4.3℃/s, and the apparent width of grain boundaries decreases linearly with the increase of cooling rate.

关键词： powder metallurgy Ni-base superalloy precipitates cooling rate

Micro powder injection molding——large scale production technology for micro-sized components

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Science China(Technological Sciences) 2008年第2期51卷 121-126页

作者： YIN HaiQing jia chengchang QU XuanHui Institute of Particle and Powder Metallurgy School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083China

Micro powder injection molding (μPIM),a miniaturized variant of powder injection molding,has advantages of shape complexity,applicability to many materials and good mechanical properties. Co-injection molding has been realized between met-als and ceramics on micro components,which become the first breakthrough within the PIM field. Combined with the prominent characteristics of high features/cost ratio,micro powder injection molding becomes a potential technique for large scale production of intricate and three-dimensional micro components or micro-structured components in microsystems technology (MST) field.

关键词： micro injection molding co-injection molding large scale production microsystems technology

Predicted interfacial thermal conductance and thermal conductivity of diamond/Al composites with various interfacial coatings

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Rare Metals 2011年第5期30卷 544-549页

作者： LIANG Xuebing jia chengchang CHU Ke CHEN Hui School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China General Research Institute for Nonferrous Metals （GRINM） Beijing 100083 China

The interfacial thermal conductance （ITC） and thermal conductivity （TC） of diamond/Al composites with various coatings were theoretically studied and discussed. A series of predictions and numerical analyses were performed to investigate the effect of thickness, sound velocity, and other parameters of coating layers on the ITC and TC. It is found that both the ITC and TC decline with increasing coating thickness, especially for the coatings with relatively low thermal conductivity. Nevertheless, if the coating thickness is close to zero, or quite a small value, the ITC and TC are mainly determined by the constants of the coating material. Under this condition, coatings such as Ni, TiC, Mo 2 C, SiC, and Si can significantly improve the ITC and TC of diamond/Al composites. By contrast, coatings like Ag will exert the negative effect. Taking the optimization of interfacial bonding into account, conductive carbides such as TiC or Mo 2 C with low thickness can be the most suitable coatings for diamond/Al composites.

关键词： metallic matrix composites coatings diamonds thermal conductivity interfacial thermal conductance

Copper base materials prepared by gel-casting process

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Rare Metals 2008年第1期27卷 78-82页

作者： LIU Weihua jia chengchang SHI Yantao HAN Yuepeng School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Gel-casting process was developed as a new molding process in the field of copper base powder metallurgy to manufacture metal parts with excellent performance and complex *** changing the parameters of gel-casting process,such as dispersant and solid loading,the corresponding effects on the rheology of Cu slurries,molding and sintering behaviors were *** results show that the viscosity of Cu slurries was significantly reduced with an increase in *** most appropriate solid loading was found to be 61% and the sintering temperature was 910°C in these *** the optimization of parameters of gel-casting process,copper composite parts with relatively high density and better properties were obtained.

关键词： gel-casting Cu powder metallurgy rheology drying rate shrinkage ratio

Kinetic characteristics of liquid phase sintering of mechanically activated W-15wt%Cu powder

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Journal of University of Science and Technology Beijing 2006年第4期13卷 338-345页

作者： Zhigang Li chengchang jia Yuntao He Liliang Chen Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

The kinetic characteristics of W grain growth operated by diffusion controlled Oswald ripening （DOR） during liquid phase sintering were studied. A liquid phase sintering of W-15wt%Cu was carried out by pushing compacts into a furnace at the moment when the temperature increased to 1340℃ for different sintering times. The results show that liquid phase sintering produces the compacts with considerably low relative density and inversely, rather high homogeneity. On the basis of the data extracted from the SEM images, the kinetic equation of W grain growth, G^n = G0^n ＋ kt, is determined in which the grain growth exponent n is 3 and the grain growth rate constant k is 0.15 μm^3/s. The cumulative normalized grain size distributions produced by different sintering times show self-similar. The cumulative distribution function is extracted from the curves by non-linear fitting. In addition, the sintering kinetic characteristics of W-15wt%Cu compacts were also investigated.

关键词： liquid phase sintering mechanical alloying grain growth kinetics W-Cu alloy

Influence of mechanical alloying time on the properties of Fe_3Al intermetallics prepared by spark plasma sintering

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Journal of University of Science and Technology Beijing 2007年第4期14卷 331-334页

作者： chengchang jia Qing He Jie Meng Lina Guo Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

The Fe3Al-based intermetallics were prepared by mechanical alloying and spark plasma sintering （SPS）, and the influence of milling time on the properties of materials was investigated. The phase identification was investigated by X-ray, and the surface morphology and fractography were observed by scanning electron microscope （SEM）. The mechanical properties such as bending strength, strain, and microhardness were tested. The results show that Fe reacts with Al completely to form Fe3Al during short SPS processing time. The relative densities of the sintered samples were nearly 100%. The mechanical properties of the sintered samples can be improved along with the milling time. The representative values are the bend strength of 1327 MPa and the microhardness of 434.

关键词： Fe3A1 intermetallics mechanical properties mechanical alloying and milling powder metallurgy