Validity of Crystal Plasticity Models Near Grain Boundaries: Contribution of Elastic Strain Measurements at Micron Scale

Abstract

Synchrotron Laue microdiffraction and digital image correlation measurements were coupled to track the elastic strain field (or stress field) and the total strain field near a general grain boundary in a bent bicrystal. A 316L stainless steel bicrystal was deformed in situ into the elasto-plastic regime using a four-point bending setup. The test was then simulated using finite elements with a crystal plasticity model comprising internal variables (dislocation densities on discrete slip systems). The predictions of the model are compared with both the total strain field and the elastic strain field obtained experimentally. While activated slip systems and total strains are reasonably well predicted, elastic strains appear overestimated next to the grain boundary. This suggests that conventional crystal plasticity models need improvement to correctly model stresses at grain boundaries.