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

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 gamma-Al2O3 nano-particles 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 degrees 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.