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Abstract:The microstructures of the as-cast and as-extruded Mg-14 wt. % Li-1 wt. % Al (LA141) and Mg-14 wt. % Li-2 wt. % Sn (LT142) were observed by optical and scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The effects of Al and Sn on the grain refinement on the Mg-14Li alloy were investigated. In addition, the mechanism of grain refinement on the as-cast and as-extruded alloys was discussed from the view of the solute effect and heterogeneous nucleation effect via edge-to-edge matching model. The results showed that the average grain sizes of the as-cast LA141 and LT142 alloys were similar due to the close solute effect of 1.1 wt. % Al and 1.8 wt. % Sn, while, in the as-extruded alloys, the average grain size of LT142 was over two times finer than that of LA141. This was attributed to the reason that Li 2 MgSn particles can serve as heterogeneous nucleation sites for the β-Li matrix during the process of dynamic recrystallization (DRX), but LiMgAl 2 cannot serve the same way. Therefore, Sn can act as a more effective grain refiner for the Mg-14Li alloy compared to Al.

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