Brazability of a novel Ti-based filler alloy on the γ-TiAl alloy

Ti-47Al-2Nb-2Cr-0.15B (at.%) alloy was successfully brazed at 1050 ~ 1125 ℃ for 10 min with amorphous Ti-Zr-Cu-Ni-Co-Mo filler. The microstructures of crystalline and amorphous fillers, the effects of brazing temperature (900 ~ 1125 ℃) and holding time (0 ~ 15 min) on the wettability and spreadability of the crystalline filler over the γ-TiAl alloy as well as the relationship between the microstructure and hardness of TiAl brazed joint at different brazing temperature were analyzed by SEM, EDS, XRD, TEM and Vickers hardness tester. Results showed that the increment of spreading area of the crystalline filler on γ-TiAl alloy increased firstly and then decreased with the increasing of temperature and holding time. The interfacial microstructure of γ-TiAl brazed joint mainly consisted of TiAl substrate layer, α₂+AlCuTi (layer Ⅰ)and γ-(Ti, Zr)₂(Ni, Cu)+α-(Ti, Zr) (layer Ⅱ). The hardness of the brazing seam increased with the brazing temperature and the maximum hardness of 872(±8) HV was obtained at 1125 ℃, which was mainly related to the hard and brittle (Ti, Zr)₂(Ni, Cu) and α₂-Ti₃Al intermetallics generated in the brazing seam.