Strengthening mechanism in the dissimilar CpTi/Inconel 718 joints obtained through diffusion bonding.

The lap joints of the CpTi/Inconel-718 was obtained by Diffusion bonding (DB) at 1020 °C for 1.5 h. Microstructure and chemical composition of the lap joints were examined using polarizing Microscope, Scanning Electron Microscope(SEM) and X-Ray Diffraction(XRD). The region of the CpTi in the vicinity of interface was transformed into β-Ti and after to that was a region observed as α-Ti Widmanstatten needles in a matrix of β-Ti. This transformation of CpTi into β-structure in the vicinity of the interface was attributed to the diffusion of β-stabilizers from the Inconel side of the joint. The average shear strength of the DB CpTi/Inconel-718 joints was measured to be 223 MPa which was greater than the conventional Pulsed TIG (P-TIG) weldment of CpTi/Inconel-718 obtained using the V and Nb interlayers. This was attributed to the stabilization of β-Ti as well as confinement of IMCs to a thinner region in the DB CpTi/Inconel-718 joints.