Vacuum brazing of Ti3Al-based alloy to TiAl using TiZrCuNi(Co) fillers

A traditional Ti-13Zr-21Cu-9Ni (wt.%) filler metal was used to join Ti3Al-based alloy and TiAl intermetallics, and the joints brazed at 1213-1233 K for 600s presented a shear strength of 113-149 MPa at room temperature. For the improvement of the joint strength a Ti-Zr-Cu-Ni-Co filler metal was designed. The shear strength of the joints brazed with the Ti-Zr-Cu-Ni-Co filler at 1283 K for 300s reached 278 MPa, increased about 86.6% compared with the Ti-Zr-Cu-Ni system filler. The overall hardness in the joint brazed with the Ti-Zr-Cu-Ni-Co filler was uniformly lower than the joint brazed with Ti-Zr-Cu-Ni filler. The Ti3Al/TiAl joint brazed with Ti-Zr-Cu-Ni mainly consisted of Ti2Al, alpha(2)-Ti3Al and the residual filler metal of Ti(Cu, Al)(2) + CuZr. The phase sequence within the Ti3Al/TiAl joint brazed with Ti-Zr-Cu-Ni-Co filler from TiAl side to Ti3Al side can be described as the follows: TiAl substrate/Ti2Al +alpha(2)-Ti3Al/alpha(2)-Ti3Al+Ti-rich phase/residual filler metal/Ti-rich phase/Ti-rich phase + O-Ti2AlNb/Ti3Al substrate, and the fracture surface of the corresponding joint was characterized by Ti-rich phase, indicating that compared with the traditional Ti-Zr-Cu-Ni filler the joint ductility was increased to a great extent. (C) 2015 Elsevier B.V. All rights reserved.