The influence of Zr content on the performance of TiZrCuNi brazing filler

Brazing joining process offers a better structure integrity performance than traditional welding due to its lower melting point, considerable improved strength and narrower joining lines. It has been useful widely in aerospace industry for joining high-performance titanium alloys into a sandwich honeycomb structure, which enhances the weight reduction of aero vehicles. This research focuses on the effects of Zr content of the filler metal on brazing Ti-6Al-4V alloy sandwich structure as Zr was found to have profound influence on brazing performance e.g. brazing temperature, wettability and strength. Three different Zr content brazing filler materials were studied including two of them were designed. The associated joint tensile strength and microstructure by these three fillers were systematically evaluated. It is of interest to see that lower Zr content results in poorer brazing wettability while high Zr content leads to a reduction in strength due to the formation of interface compounds, which is an undesired phase lowering the toughness of joining. The appropriate Zr content (18 wt%) is identified with an excellent combination of strength (22.3 MPa), wettability and brazing temperature (1173 K). A range of microstructure characterization tools including (SEM, TEM and EDX) were used to reveal the effect of Zr contents on local microstructure and explore the reasons for strength and wettability weakening.