Microstructure and Thermal Expansion Behavior of Al-Si/SiC_p Metal Matrix Composites Fabricated by Spray-casting Process

摘要

Preforms of hypereutectic Al-Si metal matrix composites reinforced with or without SiC_p were fabricated by spray-casting process, and the effects of microstructural parameters, such as the volume fraction of SiC paniculate and the shape and size of the silicon phase on the coefficient of thermal expansion(CTE) of the spray-cast and hot-extruded hypereutectic Al-Si alloys were investigated. Microstructural observations of the spray-cast and hot-extruded preforms reveal that the average size of grains and Si phase become finer and the aspect ratio of Si phase become smaller with an increase in SiC_p content, i.e. the morphology of the Si phase change from rod to blocky and globular type with an increase in SiC_p content. Spray-cast and hot-extruded preform without SiC_p shows lower CTE compare to the mold-cast specimen, mainly due to fine grain size and fine Si phase with granular morphology, and increase in volume fraction of SiC particulates lower the CTE of the composites, and the CTE of hypereutectic Al-Si/ SiC_p composite is greatly influnced by the size of Si phase, and the Young's modulus.