Diffusion brazing of Ti-6Al-4V and AISI 304: an EBSD study and mechanical properties

Ti-6Al-4V and AISI 304 stainless steel were joined by diffusion brazing with a Cu interlayer at 900 degrees C for different bonding times. The influence of the bonding time on the joint width, microstructure, microhardness and shear strength was studied. Interfacial characterizations and the identification of phases were done by scanning electron microscopy and electron backscatter diffraction (EBSD). The results revealed that by increasing the bonding time, the thickness of the joint was first increased and then decreased. Microstructure examinations also showed that the joints consisted of several intermetallics such as TiCu, Ti2Cu, TiCu4, TiCu2, FeTi and Fe2Ti. On the other hand, EBSD results demonstrated that the density of Cu-Ti intermetallics was reduced with the prolonged bonding time of 80 min, thereby indicating the occurrence of isothermal solidification. The microhardness profiles also showed a different behavior with varying the bonding time due to the change in the mechanism of the joint formation. The maximum shear strength obtained was 247 MPa, when the joint was bonded for 80 min; this was approximately equal to the stainless steel strength.