Site preference and brittle-ductile transition mechanism of B2-NiAl with ternary elements additions form first-principles calculations

The mechanism between ductility and brittleness of materials is particularly important in the design of devices and materials, and which is one of the least understood properties. In this paper, site preference and brittle vs ductile behaviors of ternary elements X (X=Fe, Co, Mo, W, Pt, Sc and Y) on B2 NiAl are investigated by using of the first-principles calculations. It is shown that alloyed elements can effectively improve the ductility and even there is a transition form intrinsic brittleness to ductility from elastic constants. Competition mechanism of microcrack and dislocation shows that brittleness to ductility transition is due to the suppressed fracture but activated dislocation emission. Finally, the results show that the improved ductility is own to the weakened covalent interactions between Ni-d and Al-p states from DOS structure.