Microstructure and Mechanical Property of Zr/316L Brazed Joints by Zr–Cu–Fe Amorphous Filler

Vacuum brazing of Zr and 316 stainless steels (316L) was conducted using a Zr₇₄Cu₁₃Fe₁₃ (at%) amorphous filler. A comprehensive investigation was carried out to examine the interfacial microstructure and mechanical properties of Zr/316L joints under varying brazing temperatures and extended holding times. The reaction products in Zr/316L joints brazed at 980 °C for 10 min consisted of Zr₂Fe + Zrss/Zr(Fe,Cr)₂ + (Zr,Cu)/α-(Fe,Cr). As the temperature increased and the duration of holding was extended, both Zr(Fe,Cr)₂ and α-(Fe,Cr) layers adjacent to 316L thickened. Particularly, the growth kinetics analysis of the diffusion zone revealed that the growth coefficient of Zr(Cr,Fe)₂ and α-(Fe,Cr) were 0.0291 μm²/s and 0.0058 μm²/s, respectively, indicating that Zr(Cr,Fe)₂ exhibited a higher thickening rate than α-(Fe,Cr). The shear strength of Zr/316L joints initially increased and then deteriorated with higher brazing temperatures or longer holding times. The Zr/Zr–Cu–Fe/316L joints achieved a maximum strength of 93.5 MPa at a brazing parameter of 980 °C/15 min. Additionally, the joints initially failed at the interface of Zr(Fe,Cr)₂/316L, with cracks propagating along the brittle Zr₂Fe phase within the brazing seam.