材料期刊网

The isothermal oxidation behavior of Ti3AlC2 based material containing 5 vol% TiC inclusion in air had been investigated at 500-900 degreesC by means of TGA, XRD, Raman spectroscopy and SEM/EDS. It was demonstrated that, although Ti3AlC2 based material exhibited good oxidation resistance at temperatures above 700 degreesC, anomalous oxidation with higher oxidation rate occurred at lower temperatures of 500 and 600 degreesC. This interesting phenomenon was due to the formation of microcracks associated with the stress developed within the scales, mainly consisting of anatase, and the volume expansion as Ti3AlC2 based material was directly exposed to air at those temperatures. Its oxidation, at temperatures investigated with the exception of 600 degreesC, generally obeyed a parabolic rate law. The weight gain data for the remaining temperatures were analyzed with an instantaneous parabolic rate constant method by assuming a parabolic rate law. The variations of instantaneous parabolic rate constant with time reflected the complexity of the oxidation behavior of Ti3AlC2 based material. These variations were discussed from the viewpoint of the formation of microcracks at 500 degreesC, and preferred oxidation of TiC inclusion in the initial oxidation and its subsequent depletion at 800 and 900 degreesC on the basis of X-ray diffraction, Raman spectroscopy, SEM scale morphology observation and composition analysis using EDS. In addition, the deleterious effect of TiC inclusion on the oxidation resistance of Ti3AlC2 based material was also investigated and discussed with comparison to monolithic Ti3AlC2, which was helpful to understand the discrepancies in reports on the oxidation of Ti3AlC2.