Relative motion of grains during superplastic flow in an Al-9Zn-1 wt.%Mg alloy

The topological feature of the relative motion of grains during superplastic flow of an Al-9.3Zn-1.03Mg-0.22 wt.%Zr alloy has been examined by the translation of reference markers in the surface and interior of specimens. Microstructural evidence was obtained for grain-switching events based on the relative motion of a group of four grains. The translation of the grains seemed to occur by sliding and rotation. On the basis of the results of a texture study, accommodation strains required in this process are attributed predominantly to slip. Hence, the role played by slip in deformation at maximum strain-rate sensitivity is particularly significant for this alloy.