Cracking behaviour of carbon coating on SiC fibre and residual stresses in Ti/SiC MMCs

The main purpose of this present work was to study the cracking behaviour of carbon coating on SiC fibre and residual stresses in Ti/SiC metal matrix composites (MMCs) during thermomechanical cycling. Acoustic emission (AE), scanning electron microscopy (SEM), transmission electron microscopy and x-ray photoelectron spectroscopy (XPS) were used in order to get more information of Ti-MMC damage mechanisms under tensile stress at room and elevated temperatures. Ti-6Al-4V/SiC (sigma fibre 1140 plus) composite was used. C coating layer (approx =5 mu m) cracking and interface debonding were found after the thermomechanical testing. TiC was found at the carbon/matrix interface was found by means of XPS. The AE peaks and SEM observations reveal that the AE signals come mainly from SiC-C debonding and cracking at room temperature with an increased likelihood of C/matrix debonding at high temperatures and stresses.