Effects of bonding parameters on the properties of TLP diffusion bonding joints of Ti-22Al-25Nb O-phase alloy

The transient liquid phase (TLP) diffusion bonding of Ti-22Al-25Nb O-phase alloy using Ti-15Cu-15Ni film as interlayer has been studied on thermal-mechanical simulator Gleeble 1500D. The results show that the brittle microstructures of Ti2(Cu,Ni) and Ti(Cu,Ni) containing a small amount of Al and Nb elements were remained in the bonding zone when using short holding time. The bonding zone was composed of pure B2 phase when the holding time was long enough and a rapid cooling technology was utilized. However, the bonding zone consisted of B2 matrix and second phases of α2 and O when using a slow cooling technology. A slow cooling technology was beneficial to improving the microstructures and strengths of the joints, and the maximum tensile strengths of the joints at room temperature and 650 ℃ under the conditions of bonding temperature 990 ℃ for 90 min reached up to 1 041 MPa and 659 MPa, which are equal to 95 % and 81% of base material themselves, respectively.