Microstructure and mechanical properties of the as-cast and extruded Mg-(6-11)Li-3Al-Ce-Ca alloys

Abstract

Samples of (A) Mg-6.86Li-3.02Al-1.12Ce-0.7Ca, (B) Mg-8.15Li-3.07Al-1.12Ce- 0.72Ca and (C) Mg-10.54Li-3.54Al-1.23Ce-0.94Ca alloys are prepared by casting and extrusion process. The microstructure and mechanical properties of alloys are characterized. The results indicate that the as-cast specimens of (A) and (B) have α + β dual phase structure and the as-cast (C) alloy has β phase (Li), α + β eutectic structure. Bulk and rod-like Al2Ce and Al2Ca compounds are found in matrix and boundaries in all the alloys. The orientation relationship between a type of Al2(Ce, Ca) phase and the a phase is confirmed, i.e., [1̄12]//[725̄3]α, (11̄1)//(0111̄)α. For the extruded alloys, the microstructures are refined and the β phase has the effect of coordination during deformation. The long rod-like and bulk compounds become short rods and fine clumps distributing evenly in the extruding direction. The microstrucrure of extruded Mg-10.54Li-3.54Al-1.23Ce-0.94-Ca alloy testifies the existence of the eutectic structure. The tensile strength and yield strength of Mg-6.86Li-3.02Al-1.12Ce-0.7Ca (UTS: 12.5%, YS: 36%) and Mg-8.15Li-3.07-Al-1.12Ce-0.72Ca (UTS: 24%, YS: 46%) alloys have improved after extruding process. © 2010 The Japan Institute of Metals.