First-principles investigation of phase stability and effects on ductility for MoSi₂ alloyed by Al and Nb

In this paper, site preference, phase stability and elastic parameters of MoSi 2 for Al and Nb addition are studied using first-principles calculation. The results show that alloying elements can cause MoSi 2 to change from C11 b to C40 phase and the phase transition is due to the activated 1/2[[Formula: see text]11](110) slip system for C11 b . [Formula: see text] ratio reveals that the ductility is enhanced after phase transition. Ductile factor [Formula: see text] based on competitive processes between micro-crack opening and dislocations emission is defined to assess the ductility of MoSi 2 . Interestingly, the increased ductility is due to the activated dislocation emission but suppressed crack propagation. Finally, charge density and DOS indicate that the improved ductility is due to the weakened Mo-4d and Si-3p covalent interactions.