Infrared brazing of Ti50Al50 and Ti-6Al-4V using two Ti-based filler metals

Infrared brazing of Ti50Al50 and Ti-6Al-4V using Ti-15Cu-25Ni and Ti-15Cu-15Ni braze alloys has been conducted. The joint mainly consists of Ti-rich, Ti2Ni and interfacial Ti3Al phases. The amount of Ti2Ni is decreased with increasing the brazing temperature and/or time due to the diffusion of Ni from the braze alloy into the Ti-6Al-4V substrate during brazing. In contrast, the thickness of interfacial Ti3Al phase is insensitive to infrared brazing conditions. The interfacial Ti3Al is primarily formed during the cooling cycle of brazing due to limited solubilities of Al, Cu and Ni in α-Ti. The presence of both Ti2Ni and interfacial Ti3Al phases deteriorates shear strength of the joint. The specimen using Ti-15Cu-15Ni braze alloy demonstrates the best bonding strength of the joint infrared brazed at 970 °C above 600 s.