Microstructural Characteristics of SiC Particle Reinforced Aluminium Matrix Composites fabricated by Spray Forming Process

초록

Preforms of SiC particle-reinforced Al-Si metal matrix composites were fabricated by mixed phase injction during the spray forming process, and the microstructure of the powders and preforms produced were investigated. The Sic-reinforced droplets are particle-embedded type, and result in homogeneously dispersed type microstructure of the Al-Si/SiC composite preform. The presolidified droplets and the deposited preporm of SiC-reinforced aluminium alloy exhibit finer equiaxed grain size than that of unreinforced aluminium alloy. For unreinforced preform, eutectic silicons of granular typer are crystallized at the corner of the aluminium grains in the preform deposited. However, for SiC-reinforced droplets and preform, SiC particles seem to act as nucleation sites for primary/eutectic silicon during solidification. Such eutectic silicons seem to retard grain growth during the continued spray forming process. It is envisaged from the microstructural observations for the deposited preform that the resultant distribution of SiC injected particles in the Al-Si microstructure is affected by the mounts of liquid phase in the top part of the preform and by the solidification rate of the preform deposited.