Inverse strain rate sensitivity of bendability of an AZ31 sheet in three-point bending

Three-point bending tests were performed on as-rolled and annealed (at 150 °C) AZ31 sheet specimens at various displacement rates (1.0, 5.0 and 50.0 mm/rnin) at room temperature. The as-rolled specimens present a negative sensitivity, i.e., the bending angle decreases as the strain rate increases; however, the annealed specimens show a positive sensitivity, i.e., the bending angle increases as the strain rate increases. Such an inverse strain rate sensitivity of sheet bending may significantly impact the sheet forming of Mg alloys