GND accumulation in bi-crystal deformation: Crystal plasticity analysis and comparison with experiments

A three-dimensional, large deformation crystal plasticity model is presented in which the lengthscale effect is incorporated through the explicit coupling of the density of geometrically necessary dislocations (GNDs) with the crystallographic slip rule.The channel-die bi-crystal compression tests carried out by Sun et al. [1998. Mesoscale investigation of the deformation field of an aluminium bicrystal. Scripta Material 39(4/5), 501–508; Sun, S., Adams, B.L., King, W.E., et al., 2000. Observations of lattice curvature near the interface of a deformed aluminium bicrystal. Philosophical Magazine 80 (1), 9–25] have been assessed and the crystal plasticity model has been employed to predict the distributions of GNDs local to the grain boundary. Quantitative comparisons of the predicted distributions with those determined experimentally show reasonable agreement. The qualitative comparisons of crystal reorientation predicted by the model with those observed by Zaefferer et al. [2003. On the influence of the grain boundary misorientation on the plastic deformation of aluminium bicrystals. Acta Materialia 51, 4719–4735] show good agreement. Further analyses of the bi-crystal have been carried out both with and without the development of GNDs. The results show that the crystal re-orientations local to the grain boundary are different if GND accumulation is included, suggesting that conventional, non-lengthscale crystal plasticity models are unlikely to be capable of capturing correctly the deformations arising at grain boundaries.