Enhanced strength and ductility synergy in aluminum composite with heterogeneous structure

A new heterogeneous aluminum composite was synthesized by one step mechanical milling followed by hot pressing sintering to evade the strength–ductility trade-off. The heterogeneous structure of the composite was composed of coarse-grained Al embedded in ultrafine-grained Al reinforced by Al2O3 nanoparticles. Compared to nanocrystalline Al and bimodal Al, an excellent combination of high strength and high ductility was obtained for the extruded composite specimen. The enhanced strength and ductility could be partially attributed to the induction of geometrically necessary dislocations resulting in back stress strengthening. The new strategy is expected to be applicable to other metal matrix composites and alloys.