Grain refinement and mechanical properties of Mg–5Li–3Al alloy inoculated by Al–5Ti–1B master alloy

The grain refinement efficiency of Mg–5Li–3Al alloy inoculated by Al–5Ti–1B master alloy and the influences of grain size on the mechanical properties were investigated. With the addition of 1.0 wt% Al–5Ti–1B, the average grain size of Mg–5Li–3Al alloy decreases markedly from ~120 μm to 50 μm, leading to significant increases in both strength and elongation. The tensile yield strength (YS), ultimate tensile strength (UTS) and elongation increased from 82 MPa, 154 MPa and 7.8% to 110 MPa, 216 MPa and 12.2%, respectively. XRD and EDS analysis show that Al–5Ti–1B master alloy is composed of α-Al, Al3Ti and TiB2. Crystallographic calculations and EDS analysis indicate that TiB2 particles are the potent heterogeneous nucleating substrates for α-Mg grains, which is the main reason for grain refinement. In addition, solute element, Ti also plays an important role in grain refinement.