Polycrystal plasticity and grain boundary evolution: A unified dislocation-based diffuse-interface approach

Grain structure plays a key role in the mechanical properties of alloy materials. Engineering the grain structure requires a comprehensive understanding of the evolution of grain boundaries (GBs) when a material is subjected to various manufacturing processes. To this end, we present a computationally efficient framework to describe the co-evolution of bulk plasticity and GBs. We represent GBs as diffused geometrically necessary dislocations, whose evolution describes GB plasticity. Under this representation, the evolution of GBs and bulk plasticity can be described in unison using the evolution equation for the plastic deformation gradient, an equation central to classical crystal plasticity theories. In addition, we outline a method to introduce a synthetic potential to drive migration of a flat GB within our diffuse-interface framework. We validate the framework by simulating the evolution of a triple junction, and demonstrate its computational efficiency. We further leverage this framework to study the migration of a flat GB driven by a potential difference, subject to different sets of available slip systems and mechanical boundary conditions.