Infrared vacuum brazing of Ti–6Al–4V and Nb using the Ti–15Cu–15Ni foil

The microstructural evolution of infrared brazed joint is primarily depended upon redistribution of alloying elements such as Cu, Ni and Nb across the joint. For the specimen infrared brazed at 970 °C for 180 s, the joint primarily consists of coarse eutectic Ti2Cu, Ti2Ni intermetallics and transformed β-Ti. Increasing the brazing time to 600 s results in a fine eutectoid microstructure dominating the entire joint due to the depletion of Cu and Ni from the braze alloy into Ti–6Al–4V substrate. Ti2Cu, Ti2Ni and transformed β phases are almost absent from the specimen infrared brazed for 3600 s, and the β-Ti is stabilized by alloying high concentration of Nb. Based on the shear test result, all cracks propagate along the Nb substrate with typical ductile dimple rupture appearance. Consequently, Ti–6Al–4V and Nb can be vacuum brazed by Ti–15Cu–15Ni foil with good joint strength.