Deformation induced solute segregation and G.P. zone formation in Mg-Al and Mg-Zn binary alloys

Abstract

A dispersion of Guinier Preston (G.P.) zones yields attractive mechanical properties in wrought magnesium alloys. However, the precipitation of G.P. zones has been reported in a limited number of Mg alloys. Here, we report deformation-induced G.P. zone precipitation in Mg-9Al and Mg-5 Zn (wt.%) alloys following equal channel angular extrusion at 150 °C. While the extrusion leads to the formation of a bimodal grain structure consisting of unrecrystallized and recrystallized regions, atom probe tomography reveals a high number density of G.P. zones across both regions. Furthermore, hybrid molecular dynamics/Monte Carlo simulations suggest that the attraction of Al and Zn solute atoms to vacancy clusters formed from excess vacancies during extrusion could be the major driving force for the G.P. zone formation. This combination of experiments and computations demonstrates that strategic control of atomic-scale defects can generate novel, far from equilibrium, microstructures, thereby providing an innovative approach to strengthening severely deformed Mg alloys.