Eradicating Brittleness of Ti-6Al-4V/Cu Dissimilar Brazed Joint using a Nb Diffusion Barrier

Abstract

Directly brazing titanium (Ti) alloy and copper (Cu) using silver (Ag) based filler alloy has been recognized to be of limited success owing to the embrittlement of intermetallic compounds (IMCs) presented at joint interface. In the current investigation, strong and reliable brazing of Ti-6Al-4V and Cu was achieved by using a niobium (Nb) diffusion barrier deposited on Ti-6Al-4V base material and Ag-Cu-Ti active braze. The Nb diffusion barrier effectively suppressed the interaction between Ag-Cu-Ti filler and Ti-6Al-4V base material, avoiding formation of brittle Ti-Cu IMCs. Joint consisting of Ti-Nb solid solution, unconsumed Nb interlayer, remnant Ag-based braze and small quantity of tiny Ti-Cu IMC particles was obtained via diffusion bonding at Ti- 6Al-4V/Nb interface and active brazing between Nb interlayer and Cu based material. Bonding strength exceeding the Cu base material property was achieved in the resultant joint, ascribed to elimination of continuous bulk brittle interfacial reaction products.