Impurity concentration effects on mechanical properties of Al-doped B2-NiSc intermetallics from first-principles investigation

Abstract

First-principles method based on density functional theory has been performed to study the crystal structures, phase stability, site preferences, elastic properties, hardness, melting points, Debye temperatures and electronic properties of Al-doped B2-NiSc intermetallics with different concentrations systematically. The results show that the Al atom occupies the Sc site preferentially. For the doped systems in which an Sc atom is substituted by one Al atom, the bulk modulus increases as the Al doping concentration increases and is larger than that of pure B2-NiSc. However, the shear modulus and Young’s modulus are smaller than the parent phase. The ductility of B2-NiSc intermetallics can be improved by adding Al element, and it increases with the increase of doping concentration. But, the increase of ductility is accompanied by the decrease of hardness. The melting points of doped alloys are all lower than the parent phase. Besides, on the basis of the calculated electronic properties, Al doping weakens covalent bonding and enhances the metal bonding of Al-doped NiSc.