Strength and microstructure of brazed alumina-silicon carbide ceramic-matrix composites

Alumina-silicon carbide whisker (Al2O3-SiCw) composite pieces were brazed u nder high vacuum with Ag-Cu-based active braze alloys. Joined specimens exh ibit mean fracture strengths of 480 MPa (4.5 wt % titanium in braze) and 59 1 MPa (2.0 wt % titanium in braze) in four-point bend tests; these strength s are 78%-96% of the measured strength of the composite. The interfacial ph ases have been identified, by using transmission electron microscopy and el ectron probe microanalysis, as being Ti-3(Cu,Al,Si)(3)O, Ti5Si3, TiC, and g amma-TiO, and the relative locations of the interfacial phases are describe d. The high strengths are believed to result from both good wetting behavio r under high vacuum and the composite nature of the reaction product morpho logy.