Tailoring the microstructure, mechanical properties and damping capacities of Mg–4Li–3Al–0.3Mn alloy via hot extrusion

The microstructure, mechanical properties, and damping performance of Mg–4Li–3Al–0.3Mn alloy were systematically investigated in this research. The results show that the microstructure of Mg–4Li–3Al–0.3Mn alloy is significantly refined after extrusion. The average grain size of the as-extruded Mg–4Li–3Al–0.3Mn alloy is ∼1.5 μm and many nano-sized AlMn phases are precipitated during hot extrusion. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the as-extruded Mg–4Li–3Al–0.3Mn alloys reach 248 MPa, 332 MPa, and 14.3%, respectively, which are higher than most of the reported Mg–Li alloys. The high strength of as-extruded Mg–4Li–3Al–0.3Mn alloy is associated with the refined grains, residual dislocations, and nano-sized precipitates. The as-extruded Mg–4Li–3Al–0.3Mn alloy has better damping properties than its as-cast counterpart, with the damping capacity (Q−1) of 0.028 and 0.022 at the strain amplitude of 1 × 10−3, respectively. The relatively high Schmid factor of non-basal slip and the high dislocation density are attributed to the improved damping performance.