Low-Temperature Oxidation-Induced Crack Healing In Ti2al0.5sn0.5c-Al2o3 Composites

The oxidation-induced crack healing of an Al2O3 composite loaded with various volume fractions of Ti2Al0.5Sn0.5C repair filler particles was investigated by annealing in air at a relatively low temperature of 700 degrees C. After annealing a composite with 20 vol.% repair fillers (with a particle size of 5.6 mu m) 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 alpha-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.