Heterointerface-induced stacking fault/dislocation modulation: A way to enhance work hardening and ductility in micro/nano-reinforced aluminum composites

Abstract

The potential of utilizing bimodal microstructures (including reinforcements and grains) with a high density of heterointerfaces in tailoring defects has not been well understood in particulate-reinforced aluminum matrix composites (PRAMCs). Inspired by this architecture, we developed a micro-B₄C/nano-MgO+CNTs-reinforced bimodally-grained 6xxx aluminum alloy composite with tailored internal stress distribution and high-density heterointerface-induced wide stacking faults (SFs). The evolution of linear/planar defect substructures during deformation was studied to explore the microstructural origins of enhanced work hardening and ductility. The novel micro/nano-reinforced composite exhibited significantly higher work hardening and ductility compared to the composite containing only microparticles. This was attributed to multiple heterointerface-induced mechanisms, including hetero-deformation-induced (HDI) hardening, activation of multiple slip systems, Lomer-Cottrell (L-C) locks, and deformation-induced SF networks. These deformation mechanisms allow the composites to exhibit an enhanced strength-ductility combination via in situ reduction of the mean free paths of dislocations. In addition, molecular dynamics (MD) simulation confirmed the high efficiency of l-C locks in pinning dislocations and strengthening. A semiquantitative model was developed to analyze the influence of heterointerfaces on SF width. This study effectively demonstrates the potential of introducing numerous heterointerfaces through bimodal reinforcements/grains, which can be applied to other composites, offering a promising prototype for designing strong yet ductile materials for technological applications via modulating defects.