<p>β-Sialon has emerged as a promising material for enhancing the service life of Al₂O₃–C refractories due to its excellent physicochemical properties. The impact of varying concentrations of nanometer Al/Si alloy on the in-situ synthesis of β-Sialon within Al₂O₃–C refractory materials, as well as its oxidation behavior, was investigated. The findings indicate that the presence of Al/Si alloy promotes the formation of AlN and SiC whiskers at 1300&#xa0;°C, which subsequently facilitate the production of plate-like β-Sialon at 1500&#xa0;°C. Density functional theory analysis reveals that the (020) crystal plane of β-Sialon exhibits the lowest adsorption energy for Al₂O and AlO molecules under the influence of iron atoms, suggesting a solid–liquid–vapor growth mechanism for β-Sialon formation. The introduction of these ceramic phases significantly enhances the mechanical properties of Al₂O₃–C refractories. Specifically, the addition of 6&#xa0;wt.% Al/Si alloy yielded specimens with the highest cold modulus of rupture and cold crushing strength at 1500&#xa0;°C, achieving values of 35.2 and 127.5&#xa0;MPa, respectively––representing increases of 40.1% and 37.4%. Furthermore, during high-temperature oxidation, the formation of plate-like β-Sialon leads to the development of a dense protective layer on the surface. This impedes the diffusion pathways of oxygen and consequently enhances the oxidation resistance of the refractory.</p>