Semi-solid consolidation processing of rapidly solidified powders for fabrication of high strength AZ91 magnesium alloys

Abstract

Rapidly solidified AZ91 magnesium alloy was fabricated by a single roll technique. Microstmcture of the alloys were composed of a fine-grain supersaturated α-Mg solid solution with a small amount of β-Mg17Al12 precipitates dispersed. The ribbons were successively crushed into fine powders using mechanical grinding apparatus and preformed at 673 K using pulse current sintering machine. The preformed compacts were extruded into a bar using semi-solid consolidation process at 723 K. The pressure needed to extrude preformed AZ91 compacts was 110 MPa about 40% lower than that of as-cast alloys. Semi-solid consolidated specimen after heat treatment showed high tensile strength 350 MPa. These were mainly attributed to grain refinement. The process proposed in this study led to the improvement of formability and also tensile strength for AZ91 alloys.