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 α-Mg and β-Li phases. Irregular distribution of Al–Li lamellar and some granular fragments MgLi 2 Al observed over the magnesium-rich α-phase and lithium-rich β-phase. The influence of lanthanum addition to the alloy system leads to grain refinement by forming Al 11 La 3 and Al 4 La 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 (Al 4 La and Al 11 La 3 ) 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 Abstract