Microstructure and mechanical properties of Mg-Cu-Y alloy with a long period ordered phase

Microstructure and mechanical properties of the Mg-Cu-Y alloy were investigated. Volume fraction of a long period ordered (LPO) phase was increased with the increasing of Cu and Y contents in the Mg100-x-yCu xYy., (x = 1-3, y=2-6at. %) alloys. Yield strength of Mg-Cu-Y alloy tends to increase with the increasing volume fraction of the LPO phase, while elongation decreases. The Mg91Cu3Y 6 cast alloy indicated yield strength of 242 MPa, and high yield strength above 200 MPa was maintained at 523 K. The Mg91Cu 3Y6 cast alloy exhibited high strength over a wide temperature range compared with commercial Mg alloys (AZ91D or WE54-T6). The Mg91Cu3Y6 annealed sheet exhibited yield strength and an elongation of 412 MPa and 6%, respectively, at room temperature, and 254 MPa and 24%, respectively at 523 K. Specific strength of the Mg 91Cu3Y6 annealed sheet was 198 kN·m/kg which is higher than that of commercial Mg alloy (AZ31) or super extra duralumin (A7075-T6).