Understanding the effects of inter- and intra-grain dislocation transport in shock compression of bicrystals

Dislocation-mediated plasticity plays a critical role in the deformation behavior of most polycrystalline materials. Dislocation motion, in particular, significantly affects the material’s ability to accommodate deformation. The motion of dislocations through the material is impeded by microstructural features such as grain boundaries (GBs). Predictive models for dislocation motion within grains and across GBs can aid in material microstructure design.

In this work, we extend the dislocation density-based crystal plasticity model, called Discoflux, to incorporate dislocation transport within grains and across GBs. We present a geometric criteria that uses an interaction matrix to govern the flux of dislocations from a slip system of grain A to another slip system of grain B. The interaction matrix uses slip plane normals, slip directions, and the GB normal. Next, the outgoing flux from a slip system of grain A is distributed to slip systems of grain B ensuring the conservation of total flux.

We implement this dislocation transport model in FLAG, an in-house arbitrary Lagrangian Eulerian hydrocode. We perform high strain rate compression of copper and tantalum bicrystals for different GB orientations. Finally, we validate our results against existing literature data.