Hot deformation behavior of an extruded AZ31 alloy doped with rare-earth elements

Abstract

The effect of rare-earth (RE) elements on the hot deformation behavior of an extruded Mg–3 wt% Al–1 wt% Zn (AZ31) alloy was studied. Compression tests were conducted in a temperature range of 250–450 °C and a strain rate of 0.0001–0.1 s−1. Hot working behavior of both AZ31 and Mg–3 wt% Al–1 wt% Zn–1 wt% RE (AZ31–1RE) alloys was analyzed by applying the modified hyperbolic sinus method and calculation of activation energies and stress exponents. The same stress exponent value of ∼5 was found for both alloys. However, the deformation activation energies for AZ31 and AZ31–RE were found to be 136.2 and 110.1 kJ mol−1, respectively, indicating enhanced plasticity at high temperatures for the AZ31–RE alloy. Lattice-diffusion-controlled dislocation climb was proposed as the controlling deformation mechanism for both AZ31 and AZ31–1RE alloys. Processing maps of the AZ31 and AZ31–1RE alloys were developed and the optimum ranges of strain rate and temperature for hot working were determined. According to processing maps, it was revealed that the instability region was reduced in the AZ31–1RE alloy.