Towards the Development of High Ductility Mg–Al Based Alloys Through Second-Phase Refinement with Trace Yttrium Additions

Magnesium alloys are attractive lightweight materials for transportation industry as they offer a viable approach for reduced CO₂ emissions and fuel economy. The most widely used alloys for automotive applications are based on the Mg–Al system where the principal second-phase β-Mg₁₇Al₁₂ provides strengthening but reduces ductility. A key factor in widening the use of magnesium in crashworthy components such as vehicle body applications is the availability of cost-effective Mg casting alloys with improved ductility. Modification of the Mg₁₇Al₁₂ in Mg–Al alloys via trace additions is a promising approach to enhance the ductility while maintaining the strength. Our research has found that only trace levels of yttrium (Y) can modify the Mg₁₇Al₁₂ and improve the ductility of Mg–6Al alloy by 63%. To elucidate the mechanism of this refinement, different methods are used including thermodynamic calculations, image analysis, scanning and transmission electron microscopy.