Response surface for screw dislocation: Twin boundary interactions in FCC metals

Abstract

In a previous manuscript, large scale 3D atomistic simulations were used to study the interaction between a curved dislocation with a dominant screw character and a Coherent Twin Boundary (CTB) for three FCC metals (Al, Cu and Ni) using 6 embedded-atom method (EAM) potentials [1]. Under both uniaxial and multiaxial stresses, both transmission mechanism and critical transmission stress differ from the results reported in 2D simulations [1]. Transmission mechanisms were found to be material dependent, and non-glide (Escaig) stresses have a profound effect on the transmission. In order to provide input for constitutive equations for mesoscopic approaches, the previous results are used to inform analytic models that incorporates mechanisms observed in the atomistic simulations [1]. For Al, the Fleischer mechanism of cross-slip at the twin boundary [2] is used whereas for Cu and Ni, Escaig mechanism of cross-slip [3] at the twin boundary is invoked. For Cu and Ni the transmission stress is determined by the critical stress required to grow the cross-slip nucleus in the adjacent grain, as opposed to growth of cross-slip nucleus in the twin boundary. As a result, the critical transmission stress in these materials is almost athermal. The analytic, mechanistic model reproduces the atomistic simulation results for the Escaig stress dependence of the transmission stress as well as its dependence on a shear component in the CTB fairly well, within 10% for the Escaig stress dependence.