Microstructural analysis of infrared brazed Ti-6AI-4V and Nb using the Ti-15Cu-25Ni foil

Abstract

Microstructural analysis of infrared brazed Ti-6AI-4V and Nb at 970°C using the clad Ti-15Cu-25Ni filler metal has been performed in the experiment. For the 180 s brazed specimen, at first primary Ti2Cu, Ti 2Ni as well as eutectic microstructure are obtained upon cooling cycle of brazing, and maximum amounts of Ti2Cu and Ti2Ni are observed at the brazed joint. The amount of transient Ti2Cu and Ti2Ni intermetallics is decreased with increasing the brazing time due to depletion of Cu and Ni from the braze Into the Ti-6AI-4V substrate. Diffusion of Cu and NI into Ti-6AI-4V substrate results in isothermal solidification rather than eutectic solidification of the molten braze, and the region of transformed β-Ti is broadened as the brazing time increased to 600 s and 1 200 s. For the 3 600 s brazed specimen, Ti2Cu, Ti 2Ni and transformed β-Ti are vanished from the infrared brazed joint. Disappearance of Ti2Cu and Ti2Ni intermetallics for the longer brazing time makes Ti-15Cu-25Ni filler metal with a great potential in future applications. © 2007 ISIJ.