The oxidation behaviors of a Ti ₃ AlC ₂ /20(vol%)TiB ₂ composite, synthesized by means of in situ reactions of Ti, Al, graphite, and B ₄ C powder mixtures under hot pressing, have been investigated at 1000°–1400°C in air. The Ti ₃ AlC ₂ /20TiB ₂ composite followed the logarithmic oxidation law, and had a lower oxidation rate than the matrix Ti ₃ AlC ₂ . During the oxidation at 1000°–1400°C, a continuous Al ₂ O ₃ formed on the composite, meanwhile other different oxides formed on the top surface of the Al ₂ O ₃ layer, depending on the oxidation temperature: discontinuous α‐TiO ₂ at below 1200°C, mixture of Al ₂ TiO ₅ and TiO ₂ at 1300°C, and continuous Al ₂ TiO ₅ at 1400°C. The selective oxidation of Al occurred at the oxide/substrate interface through inward diffusion of oxygen, and TiO ₂ overgrew the Al ₂ O ₃ layer to form coarse grains through outward diffusion of titanium ions. When the temperature was above 1280°C, Al ₂ TiO ₅ appeared due to a eutectic reaction between TiO ₂ and Al ₂ O ₃ . The incorporation of TiB ₂ promoted the generation of great numbers of voids at the Al ₂ O ₃ /substrate interface and in the Al ₂ O ₃ inner layer, which is proposed as being the main reason for the Ti ₃ AlC ₂ /20TiB ₂ composite to follow a logarithmic oxidation law.

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