Hardness homogeneity on longitudinal and transverse sections of an aluminum alloy processed by ECAP

Billets of a commercial-purity aluminum Al-1050 alloy were processed by equal-channel angular pressing (ECAP) at room temperature for up to six passes and microhardness measurements were recorded on the longitudinal and cross-sectional planes of each billet. Large numbers of datum points were recorded in order to minimize the errors in the results. The measurements show the hardness increases significantly after the first pass and then increases by very small amounts in subsequent passes. There are regions of lower hardness running in bands near the top and bottom surfaces of each billet. With increasing numbers of passes, the lower hardness region near the top surface disappears and the region near the lower surface remains in place but becomes less extensive. Neglecting the very small region of lower hardness near the bottom surface, the results show there is a potential for achieving excellent three-dimensional homogeneity after six passes of ECAP.