New Mg-based amorphous alloys in MgY-misch metal systems

Abstract

New amorphous alloys in the MgYMm (where Mm denotes misch metal) system were found to form in the composition range 2.5–15 at.% Y and 0%–8% Mm by melt spinning. The highest tensile fracture strength is 530 MPa for Mg 88.5Y 7.5Mm 4 and the amorphous alloy also exhibits good corrosion resistance which is superior to that for the commercial AZ91 (MgAlZn) alloy. The application of powder metallurgy processing consisting of high pressure gas atomization and warm extrusion to an Mg 95.5Y 2.5Mm 2 alloy with good bending ductility even in a crystallized state caused the formation of a bulk alloy with a yield strength of 560 MPa at room temperature and 410 MPa at 523 K. The elevated-temperature strength is much superior to that for the heat-resistant type of MgYNd alloy (WE54A-T6). The high strength is presumably due to the formation of a finely mixed structure consisting of Mg, Mg 12 (Ce, Nd), Mg 17La 2 and Mg 24Y 5. Thus the MgYMm alloy is attractive because of the features of the high elevated-temperature strength combined with its light weight and good corrosion resistance.