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

Resin-bonded Al-SiC composite was sintered at 1100°C, 1300°C, and 1500°C in the air, the oxidation mechanism was investigated by XRD and SEM, combined with thermodynamic calculations. 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. 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 was formed which cut 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.