Contact-reactive brazing of CoCrFeMnNi high-entropy alloy to Zr alloys using Cu interlayer

Contact-reactive brazing was introduced to obtain the high-quality joints between CoCrFeMnNi high entropy alloys (HEA) and Zr alloys using Cu interlayer in a vacuum furnace. The influence of brazing temperature and holding time on the microstructure evolution and mechanical property of HEA/Cu/Zr-3 brazed joints were studied synthetically. The results displayed that the HEA/Cu/Zr-3 joints brazed at 950 degrees C for 10 min consisted of HEA/Cr-rich(Mn,Fe)ss/Zr(Cr,Mn)2/Zr2(Cu,Ni) + Zrss+Zr(Cr,Mn)2/Zr-3. As the brazing temperature raised, the Zr(Cr,Mn)2 layer adjacent to HEA thickened, the content of Zrss and blocky Zr(Cr,Mn)2 phases in brazing seam increased whereas Zr2(Cu,Ni) phase decreased. Noticeably, the Cr-rich(Mn,Fe)ss acted as the diffusion barrier at HEA/Zr(Cr,Mn)2 interface increased with the increasing of brazing temperature/holding time. The shear strength of HEA/Cu/Zr-3 joints was increased first and then diminished with the increasing of brazing temperature/ holding time. In particular, the joints brazed at 950 degrees C for 10 min had the maximum shear strength of 140.1 MPa. Moreover, the cracks started at HEA/Zr(Cr,Mn)2 interface, and extended along the bulk Zr2(Cu,Ni) phase in brazing seam. Furthermore, the finite element analysis demonstrated that the primary concentration of residual stress in HEA/Zr-3 joints was at the interface of Cr-rich (Mn,Fe)ss/Zr(Cr,Mn)2, indicating this area was the weaknesses in whole brazed joints.