Formation of nanograined structure and decomposition of supersaturated solid solution during high pressure torsion of Al–Zn and Al–Mg alloys

Abstract

Structure and phase composition of five binary Al–Zn and Al–Mg alloys were studied before and after high pressure torsion (HPT) with a shear strain 300. The grain size of (Al) solid solution and crystals of reinforcing second phases decreases drastically after HPT reaching nanometer range. As a result of HPT, the Zn-rich (Al) supersaturated solid solution decomposes completely and reaches the equilibrium state corresponding to room temperature. The decomposition is less pronounced for Al–Mg alloys. We conclude that the severe plastic deformation of supersaturated solid solutions can be considered as a balance between deformation-induced disordering and deformation-accelerated diffusion towards the equilibrium state.