Effect of Lanthanum Addition on Grain Refinement and Mechanical Properties of Mg-9Li-3Al Alloy

The impact of lanthanum addition on the microstructural changes and mechanical characteristics of Mg-9Li-3Al + xLa alloys are studied. The alloys are fabricated through a liquid metallurgy route involving stir casting by an electrical resistance furnace. The microstructural analysis showed that the as-cast alloys primarily comprises of alpha-Mg and beta-Li phases. Irregular distribution of Al-Li lamellar and some granular fragments MgLi2Al observed over the magnesium-rich alpha-phase and lithium-rich beta-phase. The influence of lanthanum addition to the alloy system leads to grain refinement by forming Al(11)La(3)and Al4La intermetallics. Among the series of cast alloys, the Mg-9Li-3Al-1La alloy exhibits excellent ultimate tensile strength-178 MPa with 10.2% elongation. Addition of 1.5 wt% La and beyond tends to coarsen the grains leading to a reduction in mechanical strength. Hot extruded Mg-9Li-3Al-1La alloy exhibited more refinement in the microstructure and breakdown of intermetallic (Al4La and Al11La3) is observed. A significant improvement in the UTS values around 39% displayed by the Mg-9Li-3Al-1La alloy extruded at a ratio of 25:1. Graphic