Active metal brazing and characterization of brazed joints in titanium to carbon–carbon composites

The Ti-metal/C–C composite joints were formed by reactive brazing with three commercial brazes, namely, Cu-ABA, TiCuNi, and TiCuSil. The joint microstructures were examined using optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry. The results of the microstructure analysis indicate solute redistribution across the joint and possible metallurgical bond formation via interdiffusion, which led to good wetting and spreading. A tube-on-plate tensile test was used to evaluate joint strength of Ti-tube/C–C composite joints. The load-carrying ability was greatest for the Cu-ABA braze joint structures. This system appeared to have the best braze spreading which resulted in a larger braze/C–C composite bonded area compared to the other two braze materials. Also, joint load-carrying ability was found to be higher for joint structures where the fiber tows in the outer ply of the C–C composite were aligned perpendicular to the tube axis when compared to the case where fiber tows were aligned parallel to the tube axis.