Designing a low-melting Sn₆Ag₇Ni₄Co₂Ti high entropy alloy filler to optimize microstructure and mechanical properties of Ti₃SiC₂/Cu joint

Brazing Ti₃SiC₂ ceramic to pure copper can expand their practical applications, but excessive brittle intermetallic in the joint is harmful to mechanical properties of joint. The key to acquire a high-quality brazed joint is to control the microstructure in brazing seam and diffusion reaction zone at Ti₃SiC₂ ceramic side. Herein, Sn₆Ag₇Ni₄Co₂Ti low-melting high entropy alloy was fabricated and brazed to acquire a defect-free Ti₃SiC₂/Cu brazed joint. Through careful characterizations of the interfacial reaction products, the influence of novel HEA filler was clarified. The high-entropy effect and hysteresis effect of HEA filler effectively reduced the rate of atomic, and metallurgical reaction was also slowed down, which is beneficial to maintain a simple interface structure. The interface of Ti₃SiC₂/Cu joint brazed with Sn₆Ag₇Ni₄Co₂Ti HEA filler is mainly composed of Ag (s, s), Cu (s, s), Cu₃Sn and FCC-base solid solution. Due to the thin diffusion reaction zone and solid solution, the maximum shear strength of 60.55 ± 3.45 MPa was achieved when the joint was brazed at 1000 °C for 10 min. This is 34.85% more than the joint brazed with Ag-26.7Cu-4.5Ti filler under its optimal brazing parameter.