Transient liquid-phase diffusion bonding of two-dimensional carbon-carbon composites to niobium alloy

Two-dimensional carbon-carbon composites (C/C) were successfully bonded to Nb alloy with a Ti/Cu interlayer by transient liquid-phase diffusion bonding (TLP-DB) in vacuum condition. The joining process consisted of two stages: solid diffusion bonding at 780 °C under joining pressure of 4 MPa for 30 min, and TLP-DB at 1050 °C for 30 min under 0 or 0.03 MPa. The results show that the eutectic Ti-Cu liquid, produced during the second stage, presented good wettability on the C/C surface and further infiltrated into the C/C matrix to take "nail effect", hence the bonding mechanisms were deduced; however, the residual Cu layer that was intentionally preserved as a stress relief buffer effectively relaxed the thermal stress of the joint, both of which made contributions to promote the shear strength of the joint that reached as high as 28.6 MPa.