Effects of reheating temperature and isothermal holding time on the morphology and thixo-formability of SiC particles reinforced AZ91 magnesium matrix composite

摘要

SiC particles (SiCp) reinforced AZ91 magnesium (Mg) matrix composite manufactured by stir casting and hot extrusion was as starting material in a series of reheating-isothermal holding experiments and thixo-compression tests. Semisolid slurries composed of alpha-Mg grains and SiCp surrounded by liquid phase were obtained by heating the starting material to its semisolid temperature. Coalescence of alpha-Mg grains and coarsening of liquid phase occurred during further isothermal holding. alpha-Mg, SiCp, and liquid phase exhibited different forming behaviors in thixo-compressions. More and wider paths for outflow of liquid were formed in the semisolid slurry held at higher reheating temperature isothermally for a longer time. SiCp flowed outward together with the liquid phase through these paths during compression and resulted in segregations of liquid phase and SiCp in the compressed specimen.