Interfacial microstructure, cracking and mechanical properties of vacuum diffusion bonding zirconium alloy to 304L stainless steel

Zirconium alloy was vacuum diffusion bonded to 304L stainless steel. Different interlayers were used to regulate the evolution of the cracks and the evolution of the microstructure. The results demonstrated that the Zr(Fe, Cr)2 solid solution and α-Zr + Zr2(Fe, Cu) eutectic phases were formed with Cu interlayer at 1000 ℃. The microcracks primarily propagate along the grain boundaries between the brittle Zr3Fe phase and secondary Zr(Fe, Cr)2 phases. The interface consists of α(Fe, Cr) and Zr(Fe, Cr)2 in the joint without interlayer. The reaction layer also contains Kirkendall voids and uniformly distributed granular precipitates. The thickness of the reaction layer increases with bonding temperature, reaching 165.75 μm with Ni interlayer joint at 1000 ℃. Cu interlayer enhances the shear strength of the joint by inhibiting the formation of brittle phases, achieving the maximum shear strength of 160.73 MPa. The maximum microhardness of joints is 854 HV0.1 obtained with Ni interlayer joint at 1000 ℃.