Effect of braze processing on SCS-6/[beta]21S titanium matrix composites

This study was undertaken to investigate the effects of braze processing on the microstructure and tensile properties of [0/90][sub s] laminates of SCS-6 SiC fiber-reinforced [beta]21S (Ti-15Mo-2.7Nb-3Al-0.25Si, wt-%) titanium matrix composites (TMC). TMC panels were exposed to brazing processes employing two forms of commercially available Ti15Cu-15Ni brazing filler metal. Tensile specimens from the panels were tested at room temperature, 1,200 F (649 C), and 1,500 F (816 C), and the resulting properties were compared to those of TMC specimens subjected to only a stabilization heat treatment. The results showed that the brazing processes investigated had little effect on the tensile properties of the TMC. The application of the brazing filler metals to the TMC surface resulted in a braze-transformed surface layer that exhibited brittle fracture, while the bulk of the [beta]21S matrix exhibited a ductile fracture morphology. Metallurgical analysis showed that the brazing filler metal constituents did not diffuse into the carbon-enriched outer layers of the fiber or affect the fiber/matrix reaction zone thickness. Thus, the lack of a significant effect of the brazing processes on the TMC tensile behavior can be primarily attributed to the limited embrittlement of the matrix and the absence of deleterious effects on the fibersmore » and the fiber/matrix interface.« less