Enhanced precipitate strengthening in particulates reinforced Al–Zn–Mg–Cu composites via bimodal structure design and optimum aging strategy

Abstract

Depletion of solutes on particle-Al interfaces in particulates reinforced precipitate-hardening Al composites was harmful to strength. A two-step strategy including bimodal structure design and dislocation assisting low-temperature aging was proposed to enhance the precipitate strengthening in composites. Bimodal structures can redistribute the dislocations from vicinities of particles to coarse grains and increase the density of GNDs under a low strain pre-deformation. Subsequent low-temperature aging at 373 K can eliminate the coarse phases and precipitate-free zones on both grain boundaries and phase interfaces and introduce dense plate precipitates with large aspect ratio in {111}Al planes, contributing to an ultrahigh strength in bimodal composites without the sacrifice of ductility.