Formation of textural inhomogeneity in a Zn-1.1% Al alloy during superplastic deformation

The Zn-1.1% Al alloy with a strong rolling texture has been tested under the conditions of superplasticity. The samples were cut from a sheet 5 mm thick at an angle of 20° with the sheet plane. The material in the initial state was characterized by the absence of a texture gradient over the sample thickness. Deformation led to a substantial weakening of texture maxima inside the sheet and their retention at the surface. Estimate of intragrain slip revealed that the contribution from slip was greater in deeper layers and smaller at the sheet surface. The effect was explained by different conditions of accommodation of grain-boundary sliding at the surface and inside the sheet.