Toughening aluminum matrix composites via spatial decoupling of phase interfaces and grain boundaries

To overcome poor fracture toughness in particle-reinforced aluminum matrix composites (PRAMCs), we engineered a coarse-grained architecture featuring the intragranular dispersion of micron-sized reinforcements. Fabricated via extrusion-forging-rolling, a 17 vol.% B4C/Al-Zn-Mg-Cu composite achieved a 73% toughness improvement without sacrificing strength. This exceptional fracture toughness originates from spatially decoupling phase interfaces from grain boundaries, which prevents rapid damage propagation. A synergy was identified between crack deflection induced by low-angle grain boundaries and sufficient plastic deformation in the coarse-grained matrix. This intragranular design offers a robust paradigm for developing highly damage-tolerant PRAMCs.