Microstructure and Mechanical Properties of Al-SiCp Metal Matrix composites fabricated by Spray Forming Process

초록

Preforms of SiC particle-reinforced Al-Si metal matrix composites were fabricated by Mixed Phase injection during the spray forming process, and the microstructure of the powders and the preforms produced were investigated, and the dffects of SiC particulates on the mechanical properties of the composites were evaluated. The SiC-reinforced droplets are particle-embedded type, and result in homogenously dispersed type microstructure of the Al-Si/SiC composite preform. The presolidified droplets and the deposited preform of SiC-reinforced alumimium alloy exhibit finer equiaxed grain size than that of unreinforced aluminium alloy. For unreinforced preform, eutectic silicons of granular type 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 amount of liquid phase in the top part of the preform and by the solidification rate of the preform deposited. The SiC-feinforced preform was hot extruded and subsequently T6 treated, and the composite gave the tensile strength of 345 MPa, and the elongation of 2.3%