MEASUREMENT AND SIMULATION OF PLASTIC ANISOTROPY IN MAGNESIUM ALLOY AZ31B SHEET

摘要

The anisotropic plastic responses of magnesium alloy AZ31B sheets in the stress-relieved and soft-annealed conditions are found to be similar. Measurements of the r-value (r=d epsilon_w/d epsilon_t) for 0, 45, and 900 deg oriented tensile samples highlighted a strong in-plane anisotropy, with r(0 deg)approx l and r(90 deg)approx 3.5. This anisotropic response is somewhat surprising given the nearly ideal basal texture present in the material. However, it could be simulated using a viscoplastic self-consistent model that incorporated the initial texture and the hardening response of the individual crystallite-level deformation modes. The simulation code enables us to conclude that the slight off-basal character of the texture is enough to induce a change in the balance between the activities of basal and prismatic slip. During tension along the transverse direction (90 deg), the majority of the strain is accommodated by the harder prismatic slip mode, which induces little change in the thickness, while producing a strong reduction in the width.