Microstructures and Mechanical Properties of Vacuum Brazed Ti3Al/TiAl Joints Using Two Ti-based Filler Metals

Vacuum brazing of Ti3Al-based alloy to TiAl was firstly carried out by Ti15Cu15Ni (wt%) filler metal. A continuous Ti3Al band, Ti2Ni and Ti2Cu/Cu3Ti phases formed and the joint showed a shear strength of 53.8–112.4 MPa at room temperature. For the improvement of the joint strength, a new TiZrCuNiFe filler alloy was designed, and its wettability on Ti3Al and TiAl substrate was studied with the sessile drop method. After holding for 20 min at 1010 °C the TiZrCuNiFe filler showed a low contact angle of 20° and 21° on Ti3Al and TiAl substrate, respectively. The joint brazed with this novel filler mainly consisted of Ti-rich area, Ti3Al reaction layer and residual filler metal. With the increase of the brazing temperature, the amount of residual filler metal decreased and the Ti3Al reaction layer thickened. The Ti3Al/TiAl joint brazed with TiZrCuNiFe filler exhibited a lower hardness than that brazed with TiCuNi filler. The corresponding joints brazed at 950 °C for 5 min presented the shear strength of 257.6 ± 33.6 MPa at room temperature and 304.8 ± 9.9 MPa at 600 °C.