Evolutions of microstructure and mechanical properties for SiCp/AZ91 composites with different particle contents during extrusion

SiC particles reinforced AZ91D Mg matrix composites with different particle contents fabricated by a ultrasonic method were extruded at 350 °C. Hot extrusion eliminated the “island” particle distribution, and evidently improved SiC particles distribution of the composites. However, hot extrusion induced particle cracking besides the improvement of SiC particles distribution. There existed more cracked particles in the particle-rich zones. During extrusion, SiC particles stimulated the nucleation of dynamic recrystallization in the matrix. Dynamic recrystallization is also sensitive to the particle content on a local scale in the composites. As SiC contents increased, the yield strength of the composites increased. However, the ultimate tensile strength increases of the composites were small as the SiC contents increased from 10% to 20%, because the improvement of ultimate tensile strength caused by the strengthen effects of SiC particles was offset by extrusion-induced particle cracking.