Effects of Adding La-rich Mischmetal on the Microstructure and Mechanical Properties of Hot Extruded Mg-8AI Alloys

摘要

It is possible to use hot extrusion to get grain refinement and to use rare earth elements addition to improve high temperature mechanical properties for Mg-based alloys. The aim of this study was to investigate the effects of adding La-rich mischmetal (RE) on the microstructure and mechanical properties of hot extruded Mg-8Al alloys. Mg-8Al-xRE (in wt.%; x is 0,1,2 or 3%) alloys were prepared by melting and casting in a vacuum induction furnace, and extruded at a temperature of 633K and a ratio of 90:1. Mechanical properties of the above alloys were measured at an initial strain rate of 8.3x10~(-4) s~(-1) from room temperature to 673K. Fine morphology and homogeneously distributed fine precipitates with size less than 5μm was obtained. RE greatly improves the mechanical properties of the hot-extruded Mg8Al alloy, and superplasticity of the as-extruded alloys has been observed when the temperature was 473K or above.