NEW MG-BASED AMORPHOUS-ALLOYS IN MG-Y-MISCH METAL SYSTEMS

New amorphous alloys in the Mg-Y-Mm (where Mm denotes misch metal) system were found to form in the composition range 2.5-1 5 at.% Y and 0%-8% Mm by melt spinning. The highest tensile fracture strength is 530 MPa for Mg88.5Y7.5Mm4 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 Mg95.5Y2.5Mm2 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, Mg12(Ce, Nd), Mg17La2 and Mg24Y5. 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.