An Ultrafine-Grained AZ31 Magnesium Alloy Sheet with Enhanced Superplasticity Prepared by Accumulative Roll Bonding

An ultrafine-grained AZ31 magnesium alloy sheet was produced using three-run accumulative roll bonding (ARB) performed at a rolling temperature of 350 degrees C and a reduction of 80% for each pass, based on examination of the bond interface influenced by reduction ranged from 10% to 80%. The microstructural change at the different ARB stages was observed and superplasticity of the final AZ31 alloy sheet was examined at a fixed temperature of 300 degrees C and strain rates varied from 10(-4) to 10(-1) s(-1). It is shown that a good AD31/AZ31 bond formed as a result of dynamic recrystalization (DRX) accumulation at the original separate interface, which is consistent with a high reduction. Moreover, a significant grain refinement was achieved mainly in the first run of ARB process by expanding the DRX reaction from the interface to the mass and gradual uniformity of grain size in the next by the successive DRX occurred in the AZ31 magnesium alloy. Besides, a superplastic tension with a high elongation of 316% was successfully performed at a strain rate of 10(-2) s(-1) indicating a low temperature and high strain rate superplasticity in the AZ31 alloy sheet processed by ARB. The results indicate that ARB is a promising approach to produce the ultrafine-grained magnesium alloy sheet with enhanced superplasticity.