Phase Transformations in the Al–Mg-Based Alloys Driven by the Severe Plastic Deformation

Abstract

It was discovered early the that severe plastic deformation (SPD) not only leads to the remarkable grain refinement but also enables effective mechanical mixing of diverse materials, allowing for a high concentration of dissolved components in a solid solution. Later it was observed that this dissolution of the second-phase precipitates and enrichment of a solid solution occurs simultaneously with decomposition of a solid solution. These two processes compete with each other during SPD. After a certain deformation, a steady-state concentration c_ss of the second component is reached in the solution during SPD. This concentration can be found at the solvus line in the phase diagram at the certain temperature T_eff (called usually effective temperature). The effect of SPD on the structure of various Al−Mg-based alloys is analyzed. The similarity and differences of precipitation and dissolution during various severe plastic deformation methods is described. The model describing the change of concentration in a solid solution during high-pressure torsion is developed.