Superplastic deformation behavior of ultra-fine-grained 5083 Al alloy using load-relaxation tests

In this study, superplastic deformation behavior of ultra-fine-grained (UFG) 5083 Al alloy was investigated in the context of inelastic deformation theory. By imposing an effective strain of 8 via equal-channel angular pressings, most of the grains were significantly refined to 0.3 μm with non-equilibrium boundaries. A series of tension and load-relaxation tests was carried out to measure elongations and to obtain flow curves of UFG alloy at strain rates of 10−4 to 10−2 s−1 and at temperatures of 498–548 K corresponding to 0.58–0.65 Tm. The UFG alloy exhibited much higher elongations than the coarse grain alloy at the same temperatures and strain rates, indicating that low-temperature superplasticity was achieved by UFG alloy in spite of its non-equilibrium grain boundaries. Quantitative analysis on deformation mechanisms of UFG alloy was made and compared with those of coarse grain alloy.