Releasing the residual stress of Cf/SiC-GH3536 joint by designing an Ag-Cu-Ti + Sc2(WO4)3 composite filler metal

Due to native character of thermal expansion coefficient (CTE) mismatch between Cf/SiC and GH3536, achieving high strength joint was a huge challenge for Cf/SiC-GH3536 joints. Herein, a composite filler metal of Ag-Cu-Ti + Sc2(WO4)3 was developed to join Cf/SiC and GH3536. This work introduced Sc2(WO4)3 to Ag-Cu-Ti system as a negative thermal expansion (NTE) reinforcing phase to release joint residual stress. Sc2(WO4)3 was evenly distributed in the brazing seam and reacted with Ti to form Ti3O5 reaction layer. The results of finite element analysis showed that the residual stress of the joints was effectively released by introducing Sc2(WO4)3 reinforcing phase, and the mises stress was decreased from 447 to 401 MPa. The maximum shear strength of the Cf/SiC-GH3536 joint brazed with Ag-Cu-Ti + 6 vol% Sc2(WO4)3 filler alloys was 64 MPa, which was about 2.6 times higher than that of Ag-Cu-Ti alloys. The results of this study provide a promising strategy for the introduction of new Sc2(WO4)3 reinforcing phase in Ag-Cu-Ti system, and improve the reliability and feasibility of composite brazing alloy in brazing filed.