Brazing TiAl intermetallics using TiNi–V eutectic brazing alloy

Abstract

A novel TiNi–V25 (at.%) eutectic brazing alloy, which was composed of TiNi intermetallics and V, was designed and fabricated. Subsequently, the brazing alloy was used to braze TiAl intermetallics (Ti–42.5Al–9V–0.3Y (at.%)) and reliable joints were obtained. The typical interfacial microstructure of TiAl brazed joints was characterized by employing SEM, EDS and XRD, and the brazing mechanism was analyzed in detail. The brazed joints mainly consisted of B2 phase and τ3-Al3NiTi2 intermetallics. Interfacial morphology of TiAl joints varied with the increase of brazing temperature, while the phase constitution in joints did not change sound TiAl joints with the highest average shear strength of 196MPa were obtained when the specimens were brazed at 1220°C for 10min. The presence of B2 phase and τ3-Al3NiTi2 intermetallics in joints deteriorated the joining properties due to their brittleness, which led to cleavage-dominated fracture after shear test. The crack propagation path and fracture location were mainly determined by the content and distribution of τ3-Al3NiTi2 phase.