Crack Healing in Ti ₂ Al _0.5 Sn _0.5 C–Al ₂ O ₃ Composites

Abstract

Oxidation induced crack healing of Al 2 O 3 composites loaded with a MAX phase based repair filler (Ti 2 Al 0.5 Sn 0.5 C) was examined. The fracture strength of 20 vol% repair filler loaded composites containing artificial indent cracks recovered fully to the level of the virgin material upon isothermal annealing in air atmosphere after 48 h at 700°C and 0.5 h at 900°C. SEM ‐ EBSD analysis of crack microstructure indicates two different oxidation reaction regimes to govern the crack filling: near the surface SnO 2 , TiO 2 , and Al 2 O 3 were formed whereas deeply inside the cracks Al 2 O 3 and TiO 2 and metallic Sn were detected. The presence of elemental Sn was attributed to partial oxidation of aluminum and titanium which lowered the local oxygen concentration below a threshold value required for Sn oxidation to SnO 2 . Thus, Ti 2 Al 0.5 Sn 0.5 C may represent an efficient repair filler system to trigger oxidation induced crack healing in ceramic composites at temperatures below 1000°C.