Effect of Y on microstructure and mechanical properties of duplex Mg-7Li alloys

Mg-7Li-xY (x = 0-7 wt.%) alloys were prepared by permanent mould casting method, and the microstructure and mechanical properties of the alloys were investigated. The results show that alpha-Mg and beta-Li phases exist in all alloys. The Y-enriched alpha-Mg phase distributes along the edge of alpha-Mg phase and in the beta matrix of x = 1-7 alloys, and Mg24Y5 mainly disperses in the beta matrix of x = 3-7 alloys. The strength of the alloy is enhanced by adding Y element, and the elongation is improved with the Y content no more than 3 wt.%. The as-cast Mg-7Li-3Y alloy exhibits an optimum combination of mechanical properties with the ultimate tensile strength, yield strength and elongation of 160 MPa, 144 MPa and 22%, respectively. After solutionized at 400 degrees C for 3 h with a subsequent aging at 100 degrees C, Mg-7Li-7Y alloy exhibits high ultimate tensile strength and yield strength, which are improved to 120% and 152% compared with hose of the as-cast Mg-7Li alloy, respectively. (C) 2010 Elsevier B.V. All rights reserved.