Using an Al-Cu binary alloy to compare processing by multi-axial compression and high-pressure torsion

An Al-4% Cu alloy was selected as a model material in order to compare two different procedures for imposing severe plastic deformation: multi-axial compression (MAC) and high-pressure torsion (HPT). In MAC a compressive strain is applied to prismatic samples in a sequential order along three orthogonal directions and the process is repeated to large numbers of passes in order to attain high strains. In HPT a thin disk is held between anvils and subjected to a high applied pressure and concurrent torsional straining. The results show that HPT is the optimum procedure for producing a homogeneous ultrafine-grained material. Specifically, HPT is preferable because it produces materials having a larger degree of homogeneity and the equilibrium grain sizes are smaller and the Vickers microhardness values are higher than when processing by MAC.