On the relation between the microstructure and the mechanical behavior of pure Zn processed by high pressure torsion

Abstract

Pure Zn was processed by high pressure torsion (HPT) at room temperature in order to evaluate the effect of this severe plastic deformation (SPD) technique on materials processed at high homologous temperatures. HPT leads to the development of coarse grains with orientations belonging to a basal fiber by discontinuous dynamic recrystallization (DDRX). The strength of the texture increases dramatically with the applied shear strain in such a way that, after 5 turns, the volume fraction of oriented material is 85%. The samples processed to large strains possess high yield strength along the in-plane directions due to the reduced activity of basal slip and the operation of non-basal systems. The microhardness values nevertheless remain similar to those of the annealed material up to equivalent strains of 50 and then they decrease gradually with increasing strain due to grain growth. The microstructural development of pure Zn after HPT is critically influenced by the initial microstructure, as well as by the temperature increase during processing which is highly dependent on the rotational speed of the anvils.