Improving the ductility of nanostructured Al alloy using strongly textured nano-laminated structure combined with nano-precipitates

A ductile nanostructured Al alloy with desired microstructure is tailored via the precipitation optimization and texture design. The microstructure consists of two-dimensional nano-laminated structure with strong texture and one-dimensional elongated sub-micron structure with intra-precipitations at nanoscale and sub-nanoscale level. The precipitation optimization is realized by the appropriate introduction of its embryo in the NS matrix before aging. The embryo is the solute-rich structures (solute clusters) segregated to dislocations due to strain-induced dissolution of initial precipitations into the matrix. These nano-precipitations not only impede dislocation motion but also accommodate plastic deformation during loading. The textured laminate activates the partial dislocation mechanism in high stacking-fault energy alloys and the extrinsic toughening mechanism during loading. In addition, the laminated structure exhibits significant texture strengthening. Therefore, both nano-precipitations and textured laminated structure are responsible for the simultaneous increase in strength and ductility. Additionally, the initial deformable precipitations play a positive role in microstructural refinement and the refined structure shows significant cluster strengthening, ~20% relative contribution to total strength. This paper provides a new understanding of designing nanostructured materials for achieving high ductility by several toughening strategies, which is expected to be applicable to other age-hardenable alloys and steels as well.