Simulation of dislocation single kinks in γ-TiAl using embedded-atom method potentials

摘要

Core structures and mobilities of kinks on 1/2<110> screw dislocations in the L1_0 structure have been simulated using embedded-atom method potentials fitted to the bulk properties of γ-TiAl. Two kinks were simulated: a half-height kink, in which the kink height was 1/4<11-bar 2>, and a full-height kink, in which the kink height was 1/2<11-bar 2>. Both kinks were diffuse, spreading out over a distance of 1.3 nm in the case of the half-height kink, and 2.8 nm in the case of the full-height kink. Both were found to move under a stress of less than 0.5 * 10~(-3) μ, where μ is the shear modulus in the glide plane. This value is approximately an order of magnitude lower than the simulated friction stress of the unkinked screw dislocation. From consideration of the available experimental data on the low-temperature deformation behaviour of γ-TiAl, it is suggested that kinks significantly modify the friction stress of dislocations in γ-TiAl.