A deep insight into the mechanical properties of Mg-Sc alloys through DFT

Mg-Sc alloy is the lightest shape-memory alloy (SMA) discovered so far, offering a new material platform for lightweight SMAs. The main challenge for this system is to reveal its micro-mechanism and tune its performance for practical applications. In this work, we conducted the first-principles calculations to investigate the mechanical properties of Mg-Sc alloys. The effect of Sc content on the martensitic transformation behavior by combining dynamical stability, phonon dispersion and Fermi surfaces analyses were examined. We found that the Sc content should be neither below 15.625 at.% nor above 21.875 at.% to ensure the electronic structure and lattice dynamics stability. The effects of Sc content and rare-earth elements doping on the hardness of Mg-Sc alloys were also explored. We demonstrated that Gd doping can enhance the hardness of Mg-Sc alloys due to the strong interatomic interactions. Our results provide a solid basis for designing high-hardness Mg-Sc-based lightweight SMAs.