Solid solution softening and hardening in the group-V and group-VI bcc transition metals alloys: First principles calculations and atomistic modeling

The interaction of d transition metal additions with dislocations was studied in bcc alloys by using the atomic row model with ab initio parametrization of the interatomic interactions. Opposite trends were obtained for the solute-dislocation interactions in the group-V (Nb, Ta) and group-VI (Mo, W) bcc metals: while additions with extra valence electrons enhance the double-kink nucleation and result in solid solution softening in the group-VI metals, they cannot cause the intrinsic softening in the group-V metals. Oppositely, additions with fewer valence electrons should lead to an intrinsic softening in the group-V metals and a strong hardening in the group-VI metals. The effect of electronic concentration on the solute-dislocation interaction is less pronounced in the group-V alloys, and other mechanisms may be dominant in their softening and hardening behavior.