Equal-channel angular pressing using plate samples

Equal-channel angular pressing (ECAP) was applied to plate samples of high-purity aluminum using processing route BCZ in which the plate is rotated by 90° in the same sense about the Z-axis between each pass. Samples were taken to a total of 4 passes, equivalent to an imposed strain of ∼4, and then examined microscopically. In the as-pressed condition, the grain size was ∼0.9 μm but the microstructure exhibited some inhomogeneity with extensive areas (∼70–80% of the total) of equiaxed grains and other areas containing elongated grains. This limited inhomogeneity was not apparent in the macroscopic properties since the Vickers microhardness, Hv, was essentially identical at all points on all planes of sectioning and the tensile behavior at room temperature was independent of the direction of orientation of the specimen gauge lengths. The tendency to develop an inhomogeneous microstructure is explained by reference to the predicted shearing patterns for processing using route BCZ with plate samples.