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 hasphase (Li), � þ � 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 thephase is confirmed, i.e., ½�� == ½7� 2� 5� � , ð1� 1Þ == ð01� 1� 1Þ� . For the extruded alloys, the microstructures are refined and thephase 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.