Infrared brazing Ti–6Al–4V and Mo using the Ti–15Cu–15Ni braze alloy

Abstract

Brazing Ti–6Al–4V and Mo using the Ti–15Cu–15Ni alloy has been extensively evaluated in the study. Both infrared and conventional furnace brazing are included in the experiment. Ti–15Cu–15Ni braze alloy demonstrates excellent wettability on Ti–6Al–4V at 970 °C. In contrast, the wettability of the molten braze on the Mo substrate is significantly improved for the test temperature above 1000 °C. The brazed specimen is primarily comprised of the Ti-rich phase, and there is no interfacial reaction layer observed in the joint. Most of the brazed joints are fractured at the Mo substrate except for the joint infrared brazed at 970 °C for 180 s. For the specimen infrared brazed at 970 °C for 180 s demonstrates the average shear strength of 251 MPa, and quasi-cleavage fracture with sliding marks on facets is widely observed in the fractured surface. ABAQUS ® stress simulations are also performed in order to illustrate the effect of residual stresses in the brazed joint during shear test. Based on the simulated result, there are two possible fracture locations in the brazed joint due to the presence of high Mises stresses, i.e., the braze alloy and Mo substrate. Additionally, the inherent low strength of the Mo substrate results in premature failure of the brazed joint during shear test for most brazed specimens.