Developing superplasticity in a magnesium AZ31 alloy by ECAP
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The processing of a magnesium AZ31 alloy by equal-channel angular pressing refines the grain size to ~2.2 μm, but annealing for 30 min at 673 K coarsens the grains to ~6.0 μm. Despite this microstructural instability, the alloy is superplastic when pulled in tension at temperatures in the range of 623–723 K with elongations up to >1000% at strain rates at and below 10−4 s−1. Experiments within the superplastic regime show the strain rate sensitivity is ~0.5 and the activation energy is close to the value for grain boundary diffusion. It is demonstrated by calculation that the experimental results are in good agreement with a model for superplasticity based on grain boundary sliding.
KeywordsFlow Stress Magnesium Alloy Boundary Diffusion Strain Rate Sensitivity AZ31 Alloy
One of the authors (RBF) was supported by a CAPES/Fulbright Scholarship. This work was supported by the U.S. Army Research Office under Grant No. W911NF-05-1-0046.
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