Strength and ductility in ultrafine-grained wrought aluminum alloys

Strength and ductility are two of the most important mechanical properties of engineering materials. In this work, a 6061 aluminum alloy was subjected to multi-directional forging (MF) and aging treatment. The samples possess high strength and high ductility after processing. The strength of samples was enhanced by dispersing ultrafine precipitate particles within the grains, reducing grain-size and increasing dislocation density after MF and aging. The ductility was improved due to reducing the forging stress during aging. Moreover, a mass of dispersing ultrafine precipitate particles widespread within the grains after aging, which helps to accumulate dislocations, increase the dislocation storage capability and resist dislocation slip that lead up to increasing work hardening, the ductility was also enhanced. A linear strengthening elastic–plastic model was developed by simplifying the stress–strain curves. On this basis, the strength and ductility of ultrafine-grained (UFG) materials were discussed. This also provides fundamental insight into the mechanisms that govern the strength and ductility of UFG materials.