Strength and Microstructure of Brazed Alumina-Silicon Carbide Ceramic-Matrix Composites

Alumina‐silicon carbide whisker (Al2O3‐SiCw) composite pieces were brazed under high vacuum with Ag‐Cu‐based active braze alloys. Joined specimens exhibit mean fracture strengths of 480 MPa (4.5 wt% titanium in braze) and 591 MPa (2.0 wt% titanium in braze) in four‐point bend tests; these strengths are 78%−96% of the measured strength of the composite. The interfacial phases have been identified, by using transmission electron microscopy and electron probe microanalysis, as being Ti3(Cu,Al,Si)3O, Ti5Si3, TiC, and γ‐TiO, and the relative locations of the interfacial phases are described. The high strengths are believed to result from both good wetting behavior under high vacuum and the composite nature of the reaction product morphology.