Effect of imposed strain and annealing temperature on uniform elongation in A5052 alloy processed by accumulative roll bonding

The relation between strain and uniform elongation, and the effect of low-temperature annealing, were examined using an Al-Mg alloy (A5052) processed by accumulative roll bonding (ARB). Specimens were deformed by ARB for 1 to 7 cycles at room temperature, and then subjected to isochronal annealing for 30 min at temperatures ranging from 100 to 300 °C. Tensile properties, hardness, and grain boundary structure before and after annealing were investigated. The uniform elongation of ARB-processed specimens decreases with increasing ARB cycles. However, the elongation is improved by low-temperature annealing for specimens processed by ARB of 3 or more cycles. Higher strain in the ARB process results in higher uniform elongation after annealing, even though the specimens have the same value of 0.2% proof stress. This improvement of the uniform elongation by annealing is caused by annihilation of dislocations inside ultra-fine grains, which are developed by ARB of 3 or more cycles