Particle size-dependent interface-dominated properties by electronic work function in Al ₂ O ₃ /Al composites from micron to submicron scale

Reinforcement size governs material properties by regulating interface continuity and inducing interface-dominated effects in particle-reinforced composites. This study focuses on the underexplored micron-to-submicron transitional regime and investigates particle size-induced interfacial evolution and its influence on multiple interface-sensitive properties in Al2O3/Al composites fabricated by fast hot-pressed sintering. Results show that, at a fixed 15 wt.% Al2O3 content, decreasing particle size increases densification and hardness, with the Al2O3(200 nm)/Al composite reaching the highest relative density of 99.65%. Electrochemical behavior exhibits a non-monotonic size dependence: the Al2O3(200 nm)/Al composite shows the most stable open-circuit potential, whereas the Al2O3(500 nm)/Al composite exhibits the lowest corrosion current density, reflecting a trade-off between interfacial stability and reactivity. Cavitation erosion resistance improves with particle refinement, manifested by shallower erosion pits and reduced surface roughness. AFM-based electronic work function analysis reveals that particle refinement transforms the interfacial contact potential difference from localized to dispersed distributions, confirming enhanced interfacial homogeneity. These results indicate that the transition of interfacial electronic states from localized concentration toward spatial delocalization provides a unified physical basis for the observed differences and decoupling among hardness, corrosion behavior, and cavitation erosion resistance, demonstrating that submicron systems exhibit pronounced interface-dominated responses without entering the nanoscale regime.