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

Mg-Al-Ca matrix composites reinforced with three sizes (1 μm, 5 μm, and 10 μm) 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 3 mm/s. The results indicate that addition of only ~1 vol% 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 5 μm and 10 μm SiCp, however, it nearly cover the whole particle as the SiCp size decreases to 1 μm. Besides, the existence of 5 μm and 10 μm SiCp is propitious to the fracture of Al2Ca phase, however, the 1 μm 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.