Achieving high-strength joining of TiAl- and Ni-based alloys at room temperature and 750 ℃ via utilizing a quinary FeCoNi-based amorphous filler

High content of single element in TiAl- or Ni-based brazing filler metal always causes the formation of bulk, directional and brittle intermetallics in the TiAl/Ni brazed joints, which deteriorates the joint mechanical properties. In this study, a multicomponent FeCoNi-based amorphous filler was applied as the filler metal to vacuum braze γ-TiAl and Ni-based superalloy. The high mixing entropy derived from the multi-principle elements was envisaged to retard the atomic diffusion and slower grain growth. The experimental results showed that three different zones were formed in the TiAl/ Fe30Co30Ni15Si8B17/Ni joint: A diffusion zone Ⅰ composed of fine γ-(Fe, Ni) phase; a crystallization seam II containing dendritic α’-(Fe, Co) phase and nanoscale (Fe, Co, Ni)23B6, Fe2B in the inter-dendritic regions; a diffusion and reaction zone Ⅲ consisting of blocky τ3 and mixed (Fe, Co, Ni)23B6, τ, TiCo phases. The relationship between the microstructure and the mechanical property both at room temperature and high temperatures were discussed. The shear tests showed that the maximum shear strength at 30 ℃ and at 750 ℃ were 363 MPa and 252 MPa respectively when brazed at 1020 ℃ for 15 min.