Effect of Cu/Ta duplex metal coating on interface characterization in SiC fibre-reinforced Ti-15 wt% V-3 wt% Cr-3 wt% AI-3 wt% Sn matrix composite

Abstract

The interfacial reaction behaviour, alloying element diffusion behaviour and interface shear mechanical properties in Cu/Ta-duplex-metal-coated SiC(SCS-6)-fibre-reinforced Ti—15-3 matrix composite (SiC/Cu/Ta/(Ti—15-3)) have been studied. The results are compared with the original SiC(SCS-6)-fibre-reinforced Ti—15-3 matrix composite (SiC/(Ti—15-3)), and the effect of the Cu/Ta duplex metal coating on the interface characterizations has been discussed. The interface reaction occurs between the coating layer and the matrix, and the thickness of the reaction layer in the SiC/Cu/Ta/(Ti—15-3) increases slightly more than that of the SiC/(Ti—15-3). Electron probe microanalysis shows that the Cu and Ta diffuse into both the SCS coating and the matrix and that a large amount of Cu and Ta exists in the interface reaction region. The Cu/Ta coating acts as a diffusion barrier layer on Ti; however, the coating has no significant effect on the diffusion behaviours of C and Si. Fibre push-out test results indicate that the Cu Ta coating layer reduced significantly the interfacial shear debond stress and frictional stress. The interfacial shear mechanical properties of the composite have significantly degenerated after thermal exposure. This degeneration is attributed to a microstructure change of the matrix, which is associated with thermal exposure and the diffusion of alloying elements during fabrication and/or following heat treatment and/or thermal exposure processes.