Oxidation mechanism of Al–Si–SiC composite at elevated temperature

Resin-bonded Al–Si–SiC composite was sintered in the air, and the oxidation mechanism was investigated utilizing industrial CT, XRD, and SEM, combined with thermodynamic calculations, as well as a reaction model, was established. The generation of Al4C3 is avoided by constructing the Al-Sialloy(l) intermediate phase. Simultaneously, AlN exists as a solid solution, which improves the stability of the composite. With temperature increasing, the antioxidant properties of the Al–Si–SiC composite are enhanced by forming a dense layer, and the oxidation mechanism varies at different temperatures. At 1100 °C, the outer layer of Al and Si oxidized to generate Al2O3 and SiO2, respectively, while the inner layer generated irregular granular AlN–SiC solid solution; At 1300 °C, the outer pores were filled densely with Al2O3 and SiO2, while the high temperature and low Po2/Pθ induced active oxidation of SiC in the inner layer so that Po2/Pθ was further reduced and the AlN–SiC solid solution particles grew up; At 1500 °C, Al-Sialloy(l) rapidly seals the outer pore channels, accompanied by the in-situ formation of mullite and dense layers, where only N2(g) is free to diffuse inward, followed by the continuous dissolution of C and N in a form of atoms in the Al-Sialloy(l) to generate hexagonal granular AlN–SiC solid solution.