Temperature Dependence of Dislocation Core Configuration in Pure Ti

The glide of a dislocation on a selected crystallographic plane is facilitated depending on the dislocation core configuration. In pure Ti, the dislocation motion has been described as jerky, gliding during an extended period at high velocity on the {10-10} prismatic plane and cross-slipping slowly during a limited period on the {10-11} pyramidal plane. The rate of cross-slip is an important parameter that influences the ductility and strength of the material. The study of the temperature dependence of dislocation core configurations will allow us to know which glide plane is favored at a given temperature, hence, allowing us to predict the rate of cross-slip. We’ve computed the temperature dependence of the dislocation core Gibbs free energy for different core configurations to study the thermodynamic stability of these configurations. These computations have been done using molecular dynamics simulations using nonequilibrium free energy calculation methods, among which the Frenkel-Ladd path and the Reversible scaling methods, and a MEAM potential describing the properties of Ti. Different ground state core configurations are reached by applying a non-Schmid stress on the simulation cell, and the changes in the structures of the cores are characterized using an elastic stability parameter. It is shown that at low temperature the prism configuration is favored but as the temperature increases, a wider range of core structures become accessible through thermal fluctuation.<br/>The authors gratefully acknowledge funding from the U.S. Oce of Naval Research under grants N00014-16-S-BA10.