Effects of calcium on the microstructures and tensile properties of Mg–5Li–3Al alloys

The as-cast Mg–5Li–3Al–xCa (x = 0, 0.5, 1, 1.5 wt.%) was prepared with vacuum induction melting furnace, then processed by hot extrusion. The microstructures and tensile properties were investigated. The results show that the grains of as-cast alloys were refined gradually with the increase of Ca content from 0.5 wt.% to 1 wt.%, while the Ca content increases to 1.5 wt.%, the grain size increases. The microstructures of investigated alloys were further refined after hot extrusion. Both as-cast and as-extruded Mg–5Li–3Al–0.5Ca alloys have the highest mechanical properties, which is mainly attributed to the grain refinement caused by the addition of Ca and the formation of strengthening phase, Al4Ca. When the addition of Ca is up to 1–1.5 wt.%, the tensile properties of alloys are worsened due to the excessive (Mg, Al)2Ca eutectic phase forming at grain boundary.