Temperature and high strain rate dependence of tensile deformation behavior in single crystal iron from dislocation dynamics simulations

Abstract

We conduct dislocation dynamics (DD) simulations of Fe periodic single crystals under tensile load at several high strain rates and temperatures. The simulations are enabled by the recent development of temperature-dependent dislocation mobility relations obtained from atomistic calculations. The plastic evolution in the simulations is governed by rapid initial dislocation multiplication, followed by a saturation of the flow stress when the subpopulation of slow plastic carriers becomes stabilized by dislocation annihilation. Above 500 K, edge dislocations coexist with screw dislocations and contribute proportionaly to the value of the flow stress. The DD simulations are used to interpret shock-loading experiments in Fe in terms of the relative importance of different strengthening mechanisms. We find that in the $10^4$-to-$10^6$ s$^{-1}$ strain rate regime, work hardening explains the hardening of shock-loaded bulk Fe crystals.