Low-temperature oxidation-induced crack healing in Ti₂Al_0.5Sn_0.5C–Al₂O₃ composites

Abstract

The oxidation-induced crack healing of an Al₂O₃ composite loaded with various volume fractions of Ti₂Al_0.5Sn_0.5C repair filler particles was investigated by annealing in air at a relatively low temperature of 700°C. After annealing a composite with 20 vol.% repair fillers (with a particle size of ~5.6 µm) for 48 hours, artificial indentation cracks prepared on the surface, as well as pores near the surface, were completely healed by filling with condensed oxidation products. Additionally, minor fraction of metallic Sn was detected. A complementary study by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy revealed that nano-sized oxidation products (SnO₂, TiO₂, and α-Al₂O₃ phase) were formed as major crack-filling species. After healing, the strength recovery of the Al₂O₃ composites was significantly improved in the composites loaded with more than 10 vol.% repair fillers and achieved 107% at 700 for 48 hours.