Brazing SiC ceramics and Zr with CoCrFeNiCuSn high entropy alloy

CoCrFeNiCuSn high-entropy alloy and Cu foam composite interlayer was used as a filler for the brazing of SiC ceramics and Zr. The microstructure and mechanical properties of the brazed joint at room temperature and high temperatures as well as the brazing mechanism were systematically investigated. The microstructure is adjusted by controlling the brazing temperature. The main phases in the joint were identified at different brazing temperatures to be a high-entropy alloy phase, α-Zr (s, s), Zr₂Cu, (Zr, Sn) and Zr(Cr, Fe)₂ Laves phase. The joint brazed at 1040 °C for 20 min exhibited a maximum shear strength of 221 MPa at room temperature and an average shear strength of 207 MPa at 600 °C. The room temperature and high temperature-strength obtained here are much higher than those obtained for joints brazed using a conventional filler. Owing to the high-entropy effect, the joint matrix is mainly composed of solid solution phase, which improves the strength and thermal stability of the joint. The existence of the hard Zr(Fe, Cr)₂ Laves phase and the soft α-Zr (s, s) phase in the joint significantly improves its strength and plasticity.