Brazing high Nb containing TiAl alloy using TiNi–Nb eutectic braze alloy

High Nb containing TiAl alloy (Ti–45Al–5Nb-(W, B, Y) (at.%)) was successfully brazed using a novel TiNi–Nb eutectic braze alloy (Ti40Ni40Nb20 (at.%)), which was fabricated by vacuum arc remelting technique in the lab. The interfacial microstructure and mechanical properties of TiAl brazed joints were characterized by electronic microscopy and shear test, respectively. Microstructure analysis results showed that new intermetallic phases of O–Ti2AlNb and τ3-Al3(Ti,Nb)2Ni formed in the joint. Moreover, the brazing temperature had a great influence on the interfacial morphology of TiAl joints. With increasing brazing temperature the dissolution style of TiAl substrate into molten braze alloy changed significantly. The shear test results showed that the maximum shear strength at room and high temperature reached 308 MPa and 172 MPa, respectively. Brittle fractures were observed in all of the TiAl brazed specimens and the fracture location varied with brazing temperature and shear test temperature. The interaction of materials and joining mechanism was systemically discussed.

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► A novel TiNi–Nb eutectic braze alloy was designed and fabricated by vacuum arc remelting.
► Brazing of high Nb containing TiAl alloy was achieved using TiNi–Nb braze alloy.
► O–Ti2AlNb and τ3-Al3(Ti,Nb)2Ni intermetallic phases were formed in the brazing seam.
► TiAl brazed joints demonstrated excellent room temperature and high temperature shear strength.