Screw-dislocation motion in b.c.c. transition metals model calculation using a tight-binding-type electronic theory

Abstract

Screw-dislocation motion under various types of shear stress has been investigated using a tight-binding-type electronic theory. The repulsive core–core interaction energies are simulated by a Born–Mayer potential, as well as a simple power law potential. Calculated Peierls stresses τ_p/μ for α-Fe (W) are 0·054 (0·036), 0·058 (0·032) and 0·080 (0·062) for shear on {110} planes, on {112} planes in the twinning direction, and on {112} planes in the anti-twinning direction respectively, where μ is the shear modulus. It is found that the motion of screw dislocations is strongly dependent upon the filling of the d-band and the orientation of the applied stress. These results qualitatively explain the anisotropic plastic behaviour of b.c.c. transition metals and the differences in the orientation dependence of the observed yield (Peierls) stress between the transition metals.