Near-liquidus molding of Mg-Al and Mg-Al-Zn alloys

A novel application of the injection molding technique for net-shape forming of Mg-9Al-1Zn and Mg-6Al alloys, starting from a particulate precursor, was investigated. It was revealed that tight control of the alloy’s temperature within a narrow range around the liquidus level generated structures with high integrity and diminished some disadvantages inherent for conventional casting which utilizes superheated melts. The homogeneous matrix consisted of fine near-equiaxed (alpha)-Mg grains/cells surrounded by mostly discontinuous precipitates of Mg17Al12 intermetallics. The primary solid phase was either completely absent or present in negligible amounts, not exceeding 5%, with a morphology ranging from globules to degenerated rosettes. The structural integrity and fine microstructure improved mechanical properties which exhibited a superior combination of strength and ductility. The role of Mg17Al12 phase as a factor controlling ductility in Mg-Al and Mg-Al-Zn alloys is considered.