Influences of grain size on mechanical properties and cold formability of Mg-3Al-1Zn alloy sheets with similar weak initial textures

Mg-3Al-1Zn magnesium alloy sheets processed by high temperature rolling were annealed at different temperatures ranging from 250 °C to 500 °C, which resulted in an increase in grain size from 7 μm to 16 μm but similarly retained weak basal textures. The annealed sheets were used for investigating the influences of grain size on mechanical properties and press formability at room temperature. Increasing the grain size results in a decrease in r-value and an increase in n-value, which are generally favored for the improvement of sheet formability. However, both stretch formability and deep drawability deteriorate with an increase in grain size. The sheet annealed at 250 °C exhibits superior deep drawability with a high limited drawing ratio of 1.87. In contrast, the sheet annealed at 500 °C fractures at the flange when drawn at a ratio of 1.72. For the former sheet, the restricted tensile twinning activity due to the smaller grain size leads to a delay of texture strengthening for the TD-texture forming at the flange during deformation, which is responsible for the enhanced deep drawability.