The heterogeneity of the aluminum structure and mechanical properties under equal-channel angular pressing

An analysis of the diffraction patterns from backscattered electrons and of measured microhardness has been performed to investigate the distributions of structural parameters (average grain/subgrain size and fraction of high-angle grain boundaries) and of the mechanical properties in the longitudinal section of a pure aluminum billet subjected to severe plastic deformation by equal-channel angular pressing. The distributions of the characteristics under study were found to be nonuniform. A minimum average grain size and a maximum fraction of high-angle boundaries were observed in the core of the billet. As the sample surface was approached, the examined parameters were seen to vary in magnitude through a broad range. Conceivable reasons for the structural heterogeneity of the material are discussed.