Effects of minor scandium addition on the properties of Mg-Li-Al-Zn alloy

An Mg-Li-based alloy containing scandium (Sc) has been prepared by melting and solidifying it in a carbon steel crucible, and by extruding at a billet preheating temperature of 200 deg. C with an extrusion ratio of 28. Age heat treatments and thermomechanical processing were performed to investigate the effect of minor addition of Sc on the microstructures and mechanical properties. Hardness, optical microscopy, scanning electron microscopy, electron probe microanalyzer, X-ray diffraction studies, and tensile tests were carried out to explore the variations in microstructures and mechanical behaviors during processing. The Mg-Li-based alloy with Sc addition presented age hardening effect at room temperature. The hardness decreased rapidly with aging temperature at temperatures below 50 deg. C, indicating that the transformation of the θ phase into the equilibrium phase AlLi should be shifted to a lower temperature. Thermomechanical treatment could enhance the work hardening effect to improve the mechanical properties