Abstract:High temperature tensile properties and microstructure evolutions of twin-roll-cast AZ31B magnesium alloy were investigated over a strain rate range from 10⁻³ to 1 s⁻¹. It is suggested that the dominant deformation mechanism in the lower strain rate regimes is dislocation creep controlled by grain boundary diffusion at lower temperature and by lattice diffusion at higher temperatures, respectively. Furthermore, dislocation glide and twinning are dominant deformation mechanisms at higher strain-rate. The processing map, the effective diffusion coefficient and activation energy map of the alloy were established. The relations of microstructure evolutions to the transition temperature of dominant diffusion process, the activation energy platform and the occurrence of the full dynamic recrystallization with the maximum peak efficiency were analyzed. It is revealed that the optimum conditions for thermo-mechanical processing of the alloy are at a temperature range from 553 to 593 K, and a strain rate range from 7×10⁻³ to 2×10⁻³ s⁻¹.

Key words: magnesium; AZ31B alloy; twin-roll cast; processing map; dislocation creep; effective diffusion coefficient