High-temperature microstructural evolution of Ti3AlC2 ceramics in a graphite bed

Microstructural evolution and chemical reactions of Ti3AlC2 ceramics in the range from 1100 degrees C to 1500 degrees C in a graphite bed were investigated in the present work. The electron probe microanalysis (EPMA) results indicated that only a thin but unbroken reaction layer was formed on the surface of Ti3AlC2 ceramics at 1100 degrees C. It was further confirmed as aluminum oxide, while aluminum oxide fine grains were distributed separately over the surface layer along a dozen microns scale. At 1300 degrees C, a continuous and dense reaction layer which was mainly composed of aluminum oxide and titanium carbide was detected. After heat-treated at 1500 degrees C, an obvious difference in metallic luster contrast between the interior and exterior layer of cross-sections of the sample was observed. The Kirkendall effect was proposed to elucidate the above results. Titanium carbide, instead of TiO2, became the main product phase in the reaction product layer. It was attributed to the weak oxidative condition in a graphite bed and low oxygen partial pressure, which was not considered in the previous study. Besides, thermodynamic calculations result was provided to elaborate on the reaction mechanism in detail.