An analysis of (the lack of) slip transfer between near-cube oriented grains in pure Al

Abstract

Slip transfer across grain boundaries was studied in annealed polycrystalline Al foils deformed in uniaxial tension by means of the analysis of the slip traces on the specimen surface. Grain orientations and selected grain boundary misorientations were measured on both surfaces of the sample using electron back-scattered diffraction mapping. Most of the grains were within 15° of a cube orientation and approximately half of the grains percolated through the specimen thickness. The Luster-Morris m' parameter (that can be computed from the surface grain orientation) was used to assess the likelihood of slip transfer across boundaries. It was found that transfer across grain boundaries was rare in near-cube oriented grains, and consistently convincing evidence was only found when m' > 0.97, which corresponds to low-angle boundaries with <15° misorientation. This behaviour was explained by the presence of many active slip slips in near-cube oriented grains that favor self-accommodation of the grain shape to the evolving boundary conditions imposed by neighboring grains instead of promoting slip transfer across the boundary. These results indicate that the alignment between slip planes and slip directions across the boundary is not the only important metric to determine the threshold for slip transfer, as the particular details of deformation in each grain (such as the number of available slip systems) also must be considered.