<p>This study focuses on typical nano-phase reinforced 2009Al matrix composites, aiming to clarify how reinforcement types affect their quench behavior. Results show significant differences in quench sensitivity between composites with different reinforcements, primarily attributed to reinforcement distribution and thermal mismatch with the matrix. For nano-sized SiC, its high surface energy leads to a tendency to segregate along grain boundaries in the composites. During quenching of SiC/2009Al composites, this distribution triggers significant Cu element segregation at grain boundaries. Additionally, the large difference in coefficients of thermal expansion (CTE) between SiC and the matrix results in a high density of thermal mismatch dislocations induced during quenching, which further reduces the stability of the supersaturated solid solution. Ultimately, this leads to significant performance degradation of thick-section components after quenching. In contrast, nano-sized Al₂O₃ has lower surface energy, allowing part of the reinforcements to easily disperse inside the grains. Consequently, the segregation of alloying elements along grain boundaries in Al₂O₃/2009Al composites during quenching is alleviated. Meanwhile, the smaller CTE difference between Al₂O₃ and the matrix reduces the density of thermal mismatch dislocations, improving the stability of the supersaturated solid solution. This thus substantially mitigates the performance degradation of thick-section components. These findings indicate that Al₂O₃ as reinforcement favors alleviating strength attenuation from quench sensitivity in large-sized Al matrix composite components.</p>