Paper number 195

THE DISTRIBUTION AND THE DIFFUSION OF SI ABOVE THE LIQUIDUS IN SICP/AL COMPOSITE

Di Zhang¹ ,Tongxiang Fan¹, Zhongliang Shi¹, Renjie Wu¹, T.Sakata², H.Mori²

1 State Key Laboratory of Metal Matrix Composites,
Shanghai Jiao Tong University,Shanghai,200030, P.R.China
2 Research Center for Ultra-High Voltage Electron Microscopy, Osaka University,
Yamada-oka, Suita, 565, Japan

Summary

The properties and the structures of liquid melt above liquidus play an important role in determining the resultant properties of the alloy and the composite, the distribution and the diffusion of Si above liquidus in molten composite melt are responsible for the interfacial reaction between SiC reinforcement and molten aluminium above liquidus. In this paper, the melt structures of SiCp/Al composites with two different reinforcement volume fraction were investigated using Liquid Metal X-Ray Diffraction and Differential Scanning Calorimety. The experimental results showed that the melt structures of SiCp/Al composite are different from that of liquid matrix alloy, Si-Si hump in the pair radial distribution function in SiCp/Al composite melt and the DSC trace indicated that Si is non-well-distributed above liquidus, the size change of short-range-order(SRO) in SiCp/Al composite melt indicated the diffusion of Si released from chemical reaction between SiC and molten Al is possible only after a given temperature or after some extent concentration fluctuation of Si. The existence of Si-Si hump and the size change of SRO are attributed to the chemical reaction in SiCp/Al composite and the existence of reinforcing particles, high volume fraction plays more greater influence on the Si-Si hump and the size change of SRO than low volume fraction.

Keywords

melt structure, distribution and diffusion of Si, interfacial reaction, SiC/Al composite.