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 Ti-15Cu-15Ni (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 Ti-Zr-Cu-Ni-Fe 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 degrees C the Ti-Zr-Cu-Ni-Fe filler showed a low contact angle of 20 degrees and 21 degrees 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 Ti-Zr-Cu-Ni-Fe filler exhibited a lower hardness than that brazed with Ti-Cu-Ni filler. The corresponding joints brazed at 950 degrees 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 degrees C. Copyright (C) 2016, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved.