Study on 3-dimensional graphene sponge reinforced C/C composites-TiAl alloy brazed joints

Abstract

To address the large residual stress and brittle compounds formation issues when brazing C/C composites and the TiAl alloy, a 3-dimensional (3D) graphene sponge (GS) reinforced Ag-Cu based braze filler was adopted. Results show that the 3D GS can compete with Cu when reacting with Ti, which results in the formation of 3D network TiC strengthening phase instead of the large-area brittle Cu2Ti phase. The TiC phase with a low coefficient of thermal expansion (CTE) can also help reduce the CTE mismatch between the Ag-Cu based braze filler and the C/C composites. The shear strength of the C/C-TiAl brazed joints increased by 40% after using a 3D GS reinforced braze filler. The effect of the GS thickness on the microstructural evolution and mechanical properties of the brazed joints were studied. The possible strengthening mechanism of the C/C-TiAl brazed joints after using the 3D GS reinforced braze filler was discussed.