Role of Al content on tensile properties and stretch formability of Mg–Al–Mn alloy sheet produced by continuous hot-rolling

Continuous rolling is a novel cost-effective process to fabricate high-performance Mg alloy sheets with good room-temperature formability, and we investigated the effect of Al content on tensile properties and room-temperature formability of a recently designed Mg–Al–Mn alloy sheet. An excellent combination of tensile 0.2 % proof stress (TPS) and limiting dome height (LDH) was achieved by adding the moderate content of Al (2 % or 4 %). The sheets annealed at a low temperature of 250 °C showed the TPSs of ∼170–180 MPa and LDHs of ∼8 mm. The LDHs further increased to ∼9 mm by the annealing at 350 °C, while moderate TPSs of ∼150–160 MPa were maintained. Further, the sheets had an in-plane isotropy in which the tensile properties along the rolling direction were very similar to those along the transverse direction. The good properties were achieved by fine grain structure with the reduced intensity of the (0001) poles. Indeed, the Elasto-ViscoPlastic Self-Consistent modeling revealed the increase of the activity of the prismatic slip by adding 4 % of Al, while it had a limited effect in improving the stretch formability. Further, we found that the deformation microstructure of the as-rolled sheets became uniform by the 2 % and 4 % Al addition, which would contribute to the reduced intensity of the (0001) poles after the annealing.