Low Temperature Superplasticity of Ultra-Fine Grained 5083 Aluminium Alloy Produced by Accumulative Roll-Bonding

Abstract

Fully annealed 5083 sheets were highly strained up to an equivalent strain of 4.0 at 473K by the novel Accumulative Roll-Bonding (ARB) process, and the superplastic behaviors of the ARBed sheets were investigated. Sub-micrometer grains formed partially in the as-ARBed material, although the most part showed a complicated deformation structure. Just before tensile test, usual recrystallization structure whose mean grain size was 10μm formed at 573K and 673K, while the ultra-fine grains with the mean grain size of 280nm formed homogeneously at 473K. The sheets showed conventional superplasticity above 573K. Further, the ARBed sheets showed large elongation up to 220% and large strain-rate sensitivity (m-value) more than 0.3 even at 473K, which is half the melting point of this alloy. The behavior of the ARBed 5083 sheets at 473K could be concluded as the low temperature superplasticity caused by the ultra-fine grains.