Core-shell strategy for triple-phase reinforced (Al2O3+SiC+Al3BC)/Al composite: Achieving enhanced stiffness and strength while retained ductility

Abstract

Novel (Al₂O₃+SiC + Al₃BC)/Al composites were successfully synthesized via in-situ reactions within the Al-B₂O₃-SiC system, aiming to significantly enhance strength and stiffness while maintaining favorable ductility. The resulting composites exhibit a hybrid microstructure comprising uniformly dispersed in-situ γ-Al₂O₃ nanoparticles and core-shell structured SiC@Al₃BC particles, in which ex-situ SiC is coated by an in-situ formed Al₃BC shell. Among the compositions studied, the Al-5B₂O₃-10SiC composite exhibited the most balanced combination of properties at room temperature, with a Young's modulus of 104 ± 1 GPa, an ultimate tensile strength (UTS) of 440 ± 4 MPa, and an elongation to failure (EL) of 4.1 ± 0.6 %. Notably, this composite also demonstrated significant thermal stability, retaining a UTS of 191 ± 6 MPa and an EL of 3.7 ± 0.3 % at 350 °C. The concurrent enhancement in stiffness and strength is attributed to synergistic reinforcement mechanisms, including the rule-of-mixtures contribution from high-modulus phases, nano-scale strengthening from Al₂O₃, and improved load transfer enabled by the SiC@Al₃BC-Al interface. Further increases in SiC content to 20 wt% or the B₂O₃ content to 10 wt% led to additional improvements, achieving moduli of 114 ± 2 GPa and 118 ± 2 GPa, and UTS values of 548 ± 6 MPa and 538 ± 3 MPa, respectively. These results demonstrate the potential of the proposed composite design for advanced applications operating under both ambient and elevated temperature conditions.