Evolution of silicon phase configuration and Si-Al interface of Si_p/Al composites

The evolution of silicon phase configuration and Si-Al interface in Si_p/Al composites (ψ(Si)=65%) fabricated by squeeze casting technology during high temperature heat-treatment were investigated. The microstructure was observed by optical microscopy, transmission electron microscopy and high resolution electron microscopy. The results show that the silicon phase configuration becomes round, annular and reticular. The configuration evolution is based on the diffusion of silicon atoms, and the process is comprised of three parts as follows: the irregular corners and edges of silicon particles are dissolved, the silicon atoms dissolved from smaller particles diffuse to larger particles, because of the concentration gradient exists between them, and the larger particles grow up, then the grown particles connect with each other, and form network configuration silicon. The Si-Al interface of composites is straight and free from interfacial reaction products, lots of dislocations are found. But after the heat treatment, the interface becomes smooth and dislocations disappear. Around the interfaces, fine silicon phases precipitate.