Hot deformation behaviour of Mg–Al–Zn alloys

Abstract

The hot working behaviour of Mg–Al–Zn alloy was studied in the temperature range of 270–370°C and strain rate range of 0·001–0·1 s−1. In order to eliminate the influence of Mg17AL12 phase, the magnesium alloy was solutionised at 420°C for 24 h and then quenched in water before hot compression. Results show that the microstructures are mainly characterised by twinning and dynamic recrystallised grains during the hot compression process. The twinning forms at lower temperature, while the dynamic recrystallised grains are usually found at higher temperature and lower strain rate. Moreover, constitutive analysis was carried out by the hyperbolic sine law function, which illustrated that the deformation mechanism of the present alloy is controlled by dislocation climb. The critical conditions associated with the onset of dynamic recrystallisation determine the changes of the strain hardening rate (θ), and the amount of dynamic recrystallised grains increases with the increasing strain in the form of sigmoid scheme.