Abstract: By implementing an intragranular distribution strategy for Al₂O₃ nanoparticles, an Al₂O₃/Al composite with ultra-high strength-ductility synergy was fabricated. The research shows that nano Al₂O₃ particles in hot-pressed composites were mainly located at grain boundaries, while hot extrusion promoted grain boundary migration, facilitating the migration of nano Al₂O₃ particles into the grains. A critical model related to materials (including reinforcement content, size) and hot deformation parameters was proposed to describe the grain boundary migration and intragranular behavior of nano reinforcements, which provides a criterion for intragranular distribution regulation. The tensile results indicate that the intragranular nano Al₂O₃ particles triggered highly efficient Orowan strengthening, significantly enhancing the strength. Meanwhile, the intragranular nano Al₂O₃ particles induced more uniform proliferation of dislocations, effectively promoting the coordinated deformation between the grain boundaries and the grain interior, thereby enhancing the elongation. Finally, a prepared 3 vol. % Al₂O₃/2009Al composite exhibits a yield strength exceeding 700 MPa and an elongation of up to 9 %, achieving a synergistic enhancement of both high strength and high ductility in metal matrix nanocomposites.

Key words: Metal matrix composites, Intragranular distribution, Strengthening, Ductility