Microstructure and mechanical properties of nanostructured metals produced by high strain deformation

Deformation structures produced by high pressure torsion (HPT) and accumulative roll-bonding (ARB) were characterized by transmission electron microscopy and electron backscatter diffraction, and the mechanical properties of the ARB samples were determined by uniaxial tensile testing. The structural evolution during HPT in high purity nickel has been examined and an extended lamellar boundary structure was observed at high strains. For ARB samples deformed to high strains, an almost similar structural morphology has been observed in both interstitial free steel and in commercial purity aluminum, whereas a relatively equiaxed structural morphology was observed in high purity aluminum samples. In all samples, both deformed by HPT and ARB, the deformation structures were composed of a large fraction of high-angle boundaries, together with low-angle boundaries and isolated dislocations between the boundaries. Common characteristics have been identified in the mechanical behavior of the ARB samples, namely a very high strength, a small uniform elongation and a relatively large post-uniform elongation after necking. For HPT and ARB the structural morphology and structural parameters are compared, and for the ARB samples structure-property relationships are also discussed.