Microstructure and bond strength of diffusion-bonded nickel aluminide–titanium joints

Diffusion bonding of Ni75Al25 alloy to commercially pure titanium was carried out at 900 °C for different times under 2 MPa in vacuum. The microstructure of transition joints was revealed by scanning electron microscopy (SEM). Good bonding was observed on all the samples. Chemical compositions of the interface of the bonded samples were identified by energy dispersive spectroscopy. EDS results indicated the formation of the different compositions at the interface of the bonded samples. X-ray diffraction studies showed the presence of TiNi, Ti2Ni, Ni3Al, Ni4.22Al0.9 and Ti phases on the fractured surfaces of bonded samples. It was observed that the shear strengths of joints increased with increasing of bonding time. The maximum shear strength was found as 205 MPa for the bonded couple treated for 2 h.