Oxidation Behavior of a Ti 3 AlC 2 /TiB 2 Composite at 1000°−1400°C in Air

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Abstract
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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