Strengthening the diffusion bonding of Zr-4 alloys through regulating surface roughness and Ti interlayer thickness

The welding of Zr alloys has garnered significant attention within the nuclear industry. In this study, diffusion bonding of Zr-4 alloys was performed at 700 °C/60 min/15 MPa, and effects of substrate surface roughness and Ti interlayer thickness on microstructure and mechanical properties of joints were investigated. Joints without or with Ti interlayers indicated an increase in bonding ratio (or diffusion layer thickness) and shear strength as the surface roughness decreased. Introducing Ti interlayers reduced the dependence on surface roughness and enhanced the joint performance. Moreover, the thickness and uniformity of diffusion layers and shear strength increased as the Ti interlayer thickness decreased. The maximum shear strength of 231 MPa was obtained for the Zr-4/Ti 10 /Zr-4 joint, 320 % higher than that of the direct joint under the same welding parameters. The fracture surfaces displayed features characteristic of shear bands and dimples, with nearly complete elimination of unbonded regions after decreasing substrate surface roughness or Ti interlayer thickness.