The significance of grain boundary sliding in the superplastic Zn–22% Al alloy after processing by ECAP

Specimens of the superplastic Zn–22% Al eutectoid alloy were processed by equal-channel angular pressing (ECAP) through a total of eight passes at 473 K. Tensile specimens were cut from the as-pressed billets and tested at two different strain rates at 473 K under conditions where there is superplastic flow. Marker lines were placed on the polished surfaces of the specimens prior to testing and these lines were used to take measurements of the grain boundary sliding offsets at elongations of ∼30%. The measurements are used to estimate the contribution of sliding to the total strain and they show that grain boundary sliding is the dominant deformation mechanism under these conditions.