Mechanical properties and microstructures of an AZ31 Mg alloy through severe plastic deformation

Equal channel angular pressing (ECAP) technique was adopted to a dilute Mg-Al alloy (AZ31) for its enhancement in formability and strength through grain refinement, The microstructure is reasonably homogeneous and equiaxed after 4 passings. The grains of the ECAPed AZ31 alloy (2.5 mum after 4 passings) are not so fine as those of the ECAPed Al alloys (0.5-1 mm) with the same ECAP strain due to the difference in ECAP processing temperature. In the activation energy for grain growth, there is clear evidence for a transition having an activation of 0.18 Q(l) (activation for lattice diffusion) from an activation energy of 0.46 Q(l) at temperatures of 473 - 523 K to an activation energy of 0.86 Q(l) at temperatures of 673 773 K. The yield stresses of the ECAPed alloy are lower than the unECAPed material whereas the hardness of the former is higher than that of the latter. For YS, the softening effect due to texture anisotropy overwhelms the strengthening due to grain refinement.