Unveiling the strengthening effect of Nb in Ti3SiC2/Ti25Zr25Ni25Cu25 + Nb/GH3536 brazed joint

In order to achieve the ceramic/metal brazed joint with excellent mechanical properties, many kinds of high-entropy alloy (HEA) filler have been developed to acquire the joint. However, in some HEAs with high content of active element, such as Ti 25 Zr 25 Ni 25 Cu 25 amorphous HEA, the metallurgical reaction between active element and base materials resulted in the formation of continuous intermetallics (IMCs) layer in the brazing seam inevitably, embrittling the brazed joint. In this study, Nb element was added into Ti 25 Zr 25 Ni 25 Cu 25 amorphous HEA filler to improve the microstructure of Ti 3 SiC 2 /GH3536 brazed joint, promoting the application of Ti 3 SiC 2 and GH3536 in the aerospace industry. After detailed characterizations, the strengthening effect of Nb in the brazed joint was unveiled. The formation of Nb-base solid solution in the brazing seam was achieved owing to the addition of Nb, which effectively inhibited the generation of large brittle IMCs bulk. Moreover, the Nb-strengthened ZrSi 2 and Ni 2 Ti phases were generated in the reaction zone, which was also favor in promoting the mechanical properties of brazed joints. When Ti 25 Zr 25 Ni 25 Cu 25 amorphous HEA filler with 20 vol.% Nb was applied to braze Ti 3 SiC 2 to GH3536, a maximum value of 85.36 ±2.39 MPa for shear strength was achieved. This study illustrates the optimization mechanism of Nb in Ti 25 Zr 25 Ni 25 Cu 25 +Nb composite filler and promotes the further application of Ti 25 Zr 25 Ni 25 Cu 25 in brazing system.