Dislocation nucleation from damaged grain boundaries in face centered cubic metals - An atomistic study

Towards unraveling the underlying behavior of grain boundaries containing a pre-existing void, we here present a computational approach to quantify the resistance of voided grain boundaries to plasticity evolution in face centered cubic metals. This is realized by conducing an atomistic modeling survey on 104 distinct grain boundaries in both Ni and Cu bicrystals subjected to uniaxial tension perpendicular to the interface plane. Within the framework of embedded-atom method, molecular dynamics simulations are performed to evaluate the critical stress and energy barrier required for dislocation nucleation from the voided interfaces. The resulting set of data is then analyzed to gage correlations between the strength of voided boundaries and common grain boundary descriptors in an effort to inform plasticity models at higher length scales. It is found that macroscopic grain boundary descriptors fail to uniquely predict the strength of damaged grain boundaries, thus suggesting some other mechanistic rationale for the role of such boundaries in governing dislocation nucleation under uniaxial tension in metals. Simulations indicate a direct correlation between the strength and ability of a grain boundary to store energy during tensile deformation. Additionally, it is also observed that a simple statistical distribution can represent dislocation nucleation stresses in face centered cubic metals. These correlations can definitely benefit the materials community in formulating rules for multi-scale materials modeling.