Effect of plastic anisotropy on the deformation behavior of bicrystalline aluminum films – Experiments and modeling

We investigated the effect of texture-induced plastic anisotropy on the deformation behavior of ultrafine-grained aluminum films with a bicrystalline texture (two grain variants). The films were uniaxially loaded along two different directions such that the heterogeneity in the plastic behavior of the two grain variants due to plastic anisotropy was minimized along one direction and maximized along the other. The bicrystalline films show smaller strain rate sensitivity and hysteresis of stress-strain response when they are deformed along the direction that minimizes plastic heterogeneity compared to the direction that maximizes it. Notable differences in flow stress and residual hardening were also found for the two loading directions. To quantitatively understand the effect of plastic anisotropy, we simulated the response of the films using three-dimensional finite elements with a microstructurally explicit model built from TEM automated crystal orientation mapping of the samples that includes a grain boundary region, along with crystal plasticity and anisotropic elasticity. The simulations reveal markedly different distribution of stresses and strains in the two grain variants when loading is performed along the two directions, which can be directly related to the ratio of Schmid factors of their most active slip systems.