Change in microstructures and mechanical properties during annealing of AZ31F magnesium alloy multi-directionally forged under decreasing temperature conditions

Hot extruded AZ31F magnesium alloy was multi-directionally forged (MDFed) to 6 passes (a cumulative strain of ΣΔε=4.8) under decreasing temperature conditions, and then the specimens MDFed to 6 passes were annealed at temperatures ranging from 373 to 623 K. The as-MDFed specimen possessed a weak (0001) texture, whereas the MDFed specimen annealed at 623 K almost random orientation. Average grain size and hardness before and after static recrystallization indicated 0.6 µm and 85.1Hv, and 3.2 µm and 58.5Hv, respectively. The relationship between hardness (Hv) and grain size (d) in both as-MDFed and as-annealed specimens followed the Hall–Petch relation, which was expressed by a unified equation of Hv=38.7+36d −1/2。