Abstract: Diffusion bonding of TiAl to Ni-based alloy(GH99) with Ti interlayer was carried out.The reaction products and the interface structures of the joints were investigated by scanning electron microscopy,electron probe X-ray microanalysis and X-ray diffraction.The results show that four kinds of reaction layers are formed at the interface between the GH99 alloy and Ti interlayer,such as(Ni,Cr)_ss,rich Ti-(Ni,Cr)_ss,TiNi and Ti₂Ni.When the holding time is short,Ti(Al)_ss layer is formed at the interface between Ti interlayer and TiAl alloy.With the holding time increasing,the Ti(Al)_ss reaction layer transformed into Ti3Al and Al₃NiTi₂.With the holding time increasing,the thickness of TiNi reaction layer increases,while the thickness of Ti₂Ni layer increases firstly and then decreases.The shear test results show that the shear strength of the joint increases at first,then decreases,and then increases with the holding time increasing.The fractographs of the joints show that the fracture mainly occurs in the Ti₂Ni reaction layer.