Microstructural and Mechanical Characterization of Interfacial Phenomena Occurring in Brazing Ti-6AL-4V Alloy Using TiZrCuPd Amorphous Ribbons

The brazing technology with the proper choose of the filler metals should provide a solution for the major disadvantage of titanium alloys related to the problems of joining. This work concerns brazing of the Ti-6Al-4 V substrates with the originally amorphous TiCuZrPd ribbon. The TiCuZrPd filler enables proceeding of the brazing process below the melting temperature of the alloy, at about 880 degrees C. As the high quality of the filler/substrate interconnection remains substantial for the industrial application, the evolution of the mechanical and structural properties was studied while the induction and resistance heating were used to obtain Ti/Ti joints. The microstructure studies showed that at the interfaces obtained by both methods, the brazed zone was characterized by the uniform microstructure without defects such as separation of intermetallic phases or Kirkendall voids. In both cases, the interface consisted of three zones: upper diffusion zone, filler material zone and lower diffusion zone. It was also observed that regardless of the heating method used, the width of the reaction zone of the joints was similar, about 47 mu m. On the other hand the ratio of the widths of the different zones was altered in dependence on the heating method used. The results showed that the brazing by induction heating increased the shear strength of the tested joints by two to three times, depending on the content of palladium in the filler metal. The highest value of shear resistance of approx. 650 MPa was noted for the joints obtained by induction heating at 850 degrees C.