Mechanical properties and microstructure evolution of CrMnFeCoNi HEA/304 SS dissimilar brazing joints

CrMnFeCoNi, a typical face-centered-cubic high-entropy alloy (HEA), was selected to fabricate a dissimilar joint with 304 stainless steel by using Ag72Cu filler metal (FM) in a vacuum furnace for the first time in this study. Neither microcracks nor pores were found in the joints, and remarkable penetration of the liquid FM was observed at the HEA/FM interface and adjusted area. Such penetration is attributed to the low solid-liquid interface energy (sigma(SL)) between HEA and the liquid FM. The penetration coefficient (D*) of the liquid FM decreased with decreasing brazing temperature and increasing brazing time. During brazing, HEA atoms diffused into the liquid FM through dissolution and penetration. Compared with the other elements of HEA, Mn exhibited strong diffusivity and considerable dissolubility in the liquid FM, resulting in a low sigma(SL) between HEA and the liquid FM. The tensile strength of the joint could reach 459.7 MPa under the solution strengthening of Mn and the increased contact areas at the HEA/FM interface. Penetration also rendered the HEA/FM interface the weak part of the joints due to the formation of a stress concentration. This finding indicates that the strength of the joints can be enhanced through the controlled penetration of FM. (C) 2020 Elsevier B.V. All rights reserved.