Microstructure and mechanical properties of SiCp/AZ91 composite deformed through a combination of forging and extrusion process

In this paper, 10vol.% SiCp/AZ91 magnesium matrix composites were fabricated by stir casting technology. The as-cast ingots were forged at 420°C with 50% reduction, and then extruded at 370°C with the ratio of 16 at a constant ram speed of 15mm/s. The results showed that the grains were refined during forging. A much finer grain size (∼2.7μm) of composite matrix was obtained by subjecting the as-forged composite to hot extrusion. The fine SiC particulates restricted the dynamic recrystallized grain growth during the hot extrusion processing, resulting in a remarkable grain refinement. The yield stress and ultimate tensile stress were increased in the as-extruded composite, with the reasons of eliminated casting flaws, the uniform particle distribution and grains refinement. The grain refinement and uniform particle distribution caused an obvious increase in work hardening rate in the as-extruded composite during tensile deformation at room temperature.