Microstructure Evolution and Mechanical Properties of AZ31 Alloy with Accumulative Roll Bonding

This work investigated the influence of the number of rolling cycle on the microstructure evolution and mechanical characteristic of AZ31 magnesium alloy processed by accumulative roll bonding (ARB). Results show that the AZ31 alloy after ARB exhibit a typical mixed grain structure, which is mainly composed of refined grains and elongated original grains. Grain refinement is achieved by dynamic recrystallization (DRX), and fine DRXed grains formed the shear band in the direction of shear stress. Interface bonding is the result of DRX occurs on the contact surfaces, fine DRXed grains continually grew and replaced the coarse grains to achieve well bond of sheets. Microhardness was improved after ARB, and increased with the increasing of ARB cycle. The microhardness of inner plate was higher than that of outer plate due to the softening effect caused by the formation of shear bands. After ARB process, the increment of strength is caused by grain refinement, and the compromise of elongation can attribute to the nucleation and growth of internal microcrack.