Study on the oxidation mechanism of Al–SiC composite at elevated temperature

Resin-bonded Al–SiC composite was sintered at 1100, 1300, and 1500°C in the air, the oxidation mechanism was investigated. The reaction models were also established. The oxidation resistance of the Al–SiC composite was significantly enhanced with temperature increase. SiC in the exterior of the composite was partially oxidized slightly, while the transformation of metastable Al₄C₃ to stable Al₄SiC₄ existed in the interior. At 1100°C, Al in the interior reacted with residual C to form Al₄C₃. With increasing to 1300°C, high temperature and low oxygen partial pressure lead to active oxidation of SiC, and internal gas composition transforms to Al₂O(g) + CO(g) + SiO(g) as the reaction proceeds. After Al₄C₃ is formed, CO(g) and SiO(g) are continuously deposited on its surface, transforming to Al₄SiC₄. At 1500°C, a dense layer consisting of SiC and Al₄SiC₄ whiskers is formed which cuts off the diffusion channel of oxygen. The active oxidation of SiC is accelerated, enabling more gas to participate in the synthesis of Al₄SiC₄, eventually forming hexagonal lamellar Al₄SiC₄ with mutual accumulation between SiC particles. Introducing Al enhances the oxidation resistance of SiC. In addition, the in situ generated non-oxide is uniformly dispersed on a micro-scale and bonds SiC stably.