Superplastic characteristics in an extruded AZ31 magnesium alloy.

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Abstract
Deformation characteristics at elevated temperatures were examined in an AZ31 magnesium alloy. The asreceived bar was extruded for refineing its microstructure. The extruded alloy had equiaxed grains with an average grain size of ∼5 μm. Tensile test revealed that the material exhibited superplasticity. The maximum elongation of 608% was obtained at a temperature of 598 K and at a strain rate of 1 × 10−4 s−1. Microstructural observations indicated that the dominant deformation process was grain boundary sliding. The strain rate sensitivity exponent in the superplastic region was 0.5 and the activation energy was close to that for grain boundary diffusion in magnesium. Experimental results suggested that the dominant deformation mechanism in AZ31 was grain boundary sliding accommodated by dislocation glide controlled by grain boundary diffusion.