Microstructure and Thermal Expansion of Spray Cast Al-Si/SiCp Composites

초록

The microstructure and thermal expansion response of spray cast and spray cast + hot extruded hypereutectic Al-Si and Al-Si/SiCp composites have been evaluated as a function of the size and shape of the Si phase, and the volume fraction of SiCp. Grain size and the size of the Si phase decrease with increasing volume fraction of SiCp. The decrease in size of the Si phase is accompanied be a decrease in aspect ratio as a result of a change in morphology from rod-like to blocky and globular. Compared to conventional mold cast Al-Si, spray cast Al-Si exhibits a lower coefficient of thermal expansion (CTE). The CTE is further decreased with the addition of, and increasing volume fraction of, SiCp to the spray cast and spray cast + hot extruded composites. Sensitivity of the CTE to the size and shape of the Si phase and the volume fraction of SiCp in the spray cast composites is analyzed and interpreted in terms of microstructure and Young's modulus.