Investigation on the role of Nb in strengthening Ti3SiC2/Ti25Zr25Ni25Cu25 + Nb/Ti60 brazed joint

Abstract

Ti25Zr25Ni25Cu25 amorphous high-entropy alloy (HEA) filler has been proved to be an excellent filler in acquiring the ceramic/metal brazed joint with thin brittle diffusion and reaction zone (DRZ). However, due to the high content of active Ti element, excessive intermetallics (IMCs) is generated in the brazing seam inevitably, which significantly deteriorates the mechanical properties of brazed joint. Therefore, it's urgent to improve the composition of Ti25Zr25Ni25Cu25 amorphous HEA filler to avoid the generation of excessive IMCs, contributing to its further application. In this study, the Ti25Zr25Ni25Cu25 amorphous HEA filler was proposed to be modified with Nb element and applied to achieve the Ti3SiC2/Ti60 brazed joint, which is a promising candidate brazed joint in the aerospace industry. According to the detailed characterization on the microstructure and mechanical properties, the role of Nb in strengthening brazed joint was clarified. The addition of Nb contributed to the generation of more ductile (Nb, β-Ti) (s, s), β-Ti (s, s) and less brittle IMCs. As a result, the brazing seam was strengthened and was not the weak area anymore during the shear test. When 20 vol% Nb was added into the HEA filler, the shear strength of Ti3SiC2/Ti60 brazed joint reached to a maximum value of 90.65 ± 3.15 MPa. This study provides a potential method to improve the composition Ti25Zr25Ni25Cu25 amorphous HEA filler and promotes its further application.