CONSOLIDATION AND THEIR MECHANICAL-PROPERTIES OF AMORPHOUS MG87.5CU5Y7.5 AND MG70CA10AL20 POWDERS PRODUCED BY HIGH-PRESSURE GAS ATOMIZATION

The newly developed ''clean process'' was confirmed to enable safe atomization and consolidation of fine Mg base alloy powders. Amorphous Mg87.5Cu5Y7.5 and Mg70Ca10Al20 powders with a particle size smaller than 25 mu m were extruded at 673 K which is higher than their crystallization temperatures (T-x). The extruded alloys have a mixed structure consisting of Mg + Mg24Y5 + Mg-2 Cu for the Mg-Cu-Y alloy and Mg + Al2Ca for the Mg-Ca-Al alloy. The particle size and interparticle spacing of these compounds are as small as 30 to 100 nm and 50 to 100 nm, respectively. The tensile strength at 298 K is 740 MPa for the former alloy and 600 MPa for the latter alloy. It is to be noticed that these values are about twice as high as the highest value for conventional Mg alloys. The high tensile strength is presumably due to the formation of the fine mixed structure consisting of nanoscale intermetallic compounds homogeneously embedded in the Mg matrix with fine grain sizes. These data allow us to expect that the newly developed Mg-based alloys proceed hereafter as a new type of high specific strength material.