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 þ dual phase structure and the as-cast (C) alloy has phase (Li), þ eutectic structure. Bulk and rod-like Al 2 Ce and Al 2 Ca compounds are found in matrix and boundaries in all the alloys. The orientation relationship between a type of Al 2 (Ce, Ca) phase and the phase is confirmed, i.e., ½ " 1 112 == ½7 " 2 2 " 5 53, ð1 " 1 11Þ == ð01 " 1 1 " 1 1Þ. For the extruded alloys, the microstructures are refined and the 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 microstructure 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.