Atomistic-based Dislocation Mobility Model for Material Strength at High Pressure

Understanding and predicting the mechanical behavior of materials at a range of temperatures, pressures, and strain rates require a detailed knowledge of the underlying mechanisms that govern plasticity. In this work, we focus on the high-pressure plastic deformation properties of bcc metals in which the plasticity is controlled by $a/2<111>$ screw-dislocation behavior in the crystalline lattice. In particular, the finite-temperature motion of the screw dislocation is believed to be associated with the formation of mobile kinks on the screw dislocation line. Thus, the accurate prediction of kink-pair activation energetics is essential to the understanding and determination of the mobility of screw dislocations in these materials. In turn, an atomistic-based dislocation mobility model for $a/2<111>$ screw dislocation is a key ingredient needed to develop predictive multiscale simulations of crystal plasticity for bcc metals. Based on the data obtained from atomistic simulations, we have developed a scaling relation and strength model for bcc metals under extreme conditions. The predicted flow stress as a function of temperature, strain rate and pressure for bcc Ta and Mo will be presented.