High strength ultrafine/nanostructured aluminum produced by back pressure equal channel angular processing

High strength ultrafine/nanograined aluminum materials with ultimate strength up to 740 MPa and Vickers microhardness up to 2285 MPa were produced using back pressure equal channel angular processing of ultrafine-sized aluminum powder at 400 °C. Microstructure analyses revealed that the attained high strength and microhardness were derived from the presence of nanosized aluminum and γ -alumina grains (5-10 nm) as well as residual amorphous alumina. The interaction between the severe shear deformation and the preexisting amorphous alumina, concurrent oxidation, and amorphous to γ -alumina transition was considered to be responsible for the formation of such a refined and complex nanostructure.