Microstructural Evolution in Pure Aluminum in the Early Stages of Processing by High-Pressure Torsion

Measurements were taken to evaluate the evolution of homogeneity in disks of high-purity aluminum in the early stages of processing by high-pressure torsion. The results demonstrate that samples processed through 1/4 or mole whole revolutions exhibit microhardness values which are generally higher in the centers of the disks than at the edges whereas after 1/8 turn the hardness is higher at the edge than in the center. It is shown that all of the hardness measurements are mutually consistent and they scatter around a unique curve When plotted against the equivalent strain. The measurements of hardness are supplemented by microstructural observations which provide evidence of a gradual evolution in the microstructure with increasing strain from an initial formation Of subgrains to an array Of Ultrafine grains separated by boundaries having high angles of misorientation. [doi: 10.2320/matertrans.MB200910]