However, the present authors have shown that, for a mechanically milled, powder-metallurgy Al- 1.1at.%Mg-1.2at.%Cu alloy with a submicron grain size, superplasticity occurs rather at an intermediate temperature around 750 K and at an intermediate strain rate of the order of 10° s−1 [1–4] and a consider- ably large portion (say, more than 70%) of the superplastic elongation is caused by the grain deformation, not by the grain boundary sliding [3,4]