A tuning nano-precipitation approach for achieving enhanced strength and good ductility in Al alloys

A new strategy through controlling the aggregation states of alloying elements before cold-rolling is proposed to tune the nano-precipitation in Al alloys processed by combining deformation and aging. A considerable improvement in strength and good ductility is achieved in Al–Mg–Si–Cu alloy by our approach, which is applicable to many precipitation-hardened alloy systems and suitable for industrial application. A bi-modal distribution of precipitates, discrete lath-like Q″-type precipitate and continuous precipitate with the composition identical to Q′-type phase, occur in the annealed sample pre-treated by natural aging. A short-term artificial aging which induces a dispersion of nano-sized coherent particles, mainly GP zone of the monoclinic β″-type phase, before cold-rolling can lead to the formation of finely and homogeneously distributed Q″-type precipitates, which are in favor of an enhancement in strengthening potential for the final aging. Our finding suggests that the solutes aggregation state before deformation affects significantly the re-precipitation of solutes during the subsequent annealing.