Microstructure and mechanical properties of Mg–Al–Ca alloy influenced by SiCp size

Abstract

Mg–Al–Ca matrix composites reinforced with three sizes (1μm, 5μm, and 10μm) of SiCp were fabricated by stir casting. Then the as-cast ingots were extruded at 400°C with the ratio of 16 at a constant ram speed of 3mm/s. The results indicate that addition of only ~1vol% SiCp is propitious to promote the nucleation and refinement of Al2Ca phase, which can eliminate the Al2Ca phase's network distribution that appeared in as-cast Mg–Al–Ca alloy. But the nucleation of Al2Ca phase strongly depends on SiCp size. Al2Ca phase nucleates at 5μm and 10μm SiCp, however, it nearly cover the whole particle as the SiCp size decreases to 1μm. Besides, the existence of 5μm and 10μm SiCp is propitious to the fracture of Al2Ca phase, however, the 1μm SiCp seems ineffective to Al2Ca phase during hot extrusion process. Compared with monolithic Mg–Al–Ca alloy, the as-extruded SiCp/Mg–Al–Ca composites exhibit much higher YS, UTS and θ value. Even though the YS and θ value increase with decreasing SiCp size, the UTS does not change linearly with them and the reasons are given and analyzed.