Fine-tuning the ductile-brittle transition temperature of Mg₂Si intermetallic compound via Al doping

Brittleness is a dominant issue that restricts potential applications of Mg₂Si intermetallic compounds (IMC). In this paper, guided by first-principles calculations, we found that Al doping will enhance the ductility of Mg₂Si. The underlying mechanism is that Al doping could reduce the electronic exchange effect between Mg and Si atoms, and increase the volume module/shear modulus ratio, both of which are beneficial to the deformation capability of Mg₂Si. Experimental investigations were then carried out to verify the calculation results with Al doping contents ranging from Al-free to 10wt%. Results showed that the obtained ductile-brittle transition temperature of the Mg₂Si-Al alloy decreased and the corresponding ductility increased. Specifically, the ductile-brittle transition temperature could be reduced by about 100℃. When the content of Al reached 6wt%, α-Al phase started to precipitate, and the ductile-brittle transition temperature of the alloy no longer decreased.