Microstructure and mechanical properties of rheo-squeeze casting AZ91-Ca magnesium alloy prepared by gas bubbling process

Rheo-squeeze casting combined with gas bubbling process was proved effective to improve the mechanical properties of AZ91-2 wt%Ca (AZX912) alloy. Increase of gas flow led to improvement of the quality of AZX912 semi-solid slurry and improved ductility of rheo-squeeze casting AZX912 alloy samples. Increase of applied pressure brought refinement in as-cast microstructure and reduction of porosity, as well as continuous improvement in both tensile strength and elongation. Heat treatment at 410 °C promoted dissolution of β-Mg17Al12 phase, morphology modification of Al2Ca phase and further increase of both tensile strength and ductility. Compared with conventional squeeze casting, the mechanical properties of rheo-squeeze casting AZX912 alloy were improved by more than 20%. The improvement in mechanical properties was mainly attributed to the grain refinement in microstructure.