Microstructure and mechanical property of Zr-3/CoCrFeMnNi high-entropy alloys joints brazed using a novel Zr[sbnd]Cu alloys

Abstract

In this paper, the Zr53Cu47 (wt%) alloys were designed by vacuum melting for the joining Zirconium (Zr) alloys to equiatomic CoCrFeMnNi high entropy alloys (HEA). The wetting, microstructure, growth kinetics of reaction layer, shear strength and rupture behavior of joints evolved with temperature were specifically deliberated. The interfacial reactions were determined to be CrMn layer/Zr(Cr,Mn)2 layer + corpuscular β-Zr/tuberous Zr2(Cu,Ni,Co,Fe) + Zrss + tuberous Zr(Cr,Mn)2 from HEA to Zr-3. Herein, the β-Zr precipitates with the sterling plasticity had the semi-coherent relationship with the matrix phase Zr(Cr,Mn)2, and β-Zr precipitates developed with the elevated temperature, contributing to the plasticity improvement of Zr(Cr,Mn)2 and the growth of joints properties. The activation energy (Q) of CrMn was 127.0 kJ/mol, significantly less than that that of Zr(Cr,Mn)2 (159.7 kJ/mol), thereby the generation of CrMn was underlying to Zr(Cr,Mn)2 during brazing. Moreover, grains orientations in CrMn and Zr(Cr,Mn)2 were stochastically dispersed. The strength of Zr-3/Zr53Cu47/HEA achieved peak of 136.8 MPa when brazed at 970 °C/10 min. Cracks were preferably started at the non-coherent interface of Zr(Cr,Mn)2/CrMn with the higher lattice mismatch degree of 26.0 % in I area, and propagated toward tuberous Zr2(Cu,Ni,Co,Fe) in II area.