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

Abstract

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 degrees C for 10 min consisted of Zr2Fe + Zrss/Zr(Fe,Cr)2 + (Zr,Cu)/alpha-(Fe,Cr). As the temperature increased and the duration of holding was extended, both Zr(Fe,Cr)2 and alpha-(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 alpha-(Fe,Cr) were 0.0291 mu m2/s and 0.0058 mu m2/s, respectively, indicating that Zr(Cr,Fe)2 exhibited a higher thickening rate than alpha-(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 degrees 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.