Diffusion bonding joint of TiAl-based alloy and Ni-based alloy by using composite interlayer

Diffusion bonding of TiAl-based alloy to Ni-based alloy by using Ti/Nb and Ti/Nb/Ni composite interlayer was carried out.The interfacial microstructure and fracture morphology were investigated by scanning electron microscopy and electron probe X-ray microanalysis.The bonding strength of the joints was evaluated through shear test.The results showed that when the interlayer was Ti/Nb,the optimum bonding time was t=30 min,the maximum shear strength was Rτ=273.8 MPa,and the fracture occured at the GH99/Nb interface;when the interlayer was Ti/Nb/Ni,the optimum bonding time was t=60 min,the maximum shear strength was Rτ=314.4 MPa,the fracture occured at Ti3Al reaction layer of Ti/TiAl interlayer.The shear strength of the joints with Ti/Nb/Ni interlayer is higher than that with Ti/Nb interlayer,and the fracture location changes.It shows that the use of Ni foil has certain effect on relaxing joint stress.