Influence of interfacial reaction on tensile strength of SiC fiber embedded in a γ-titanium-aluminide alloy

Abstract

The influences of interfacial reaction on tensile strength of continuous SiC fiber (SCS-6, Textron Specialty Materials) embedded in the Ti-48 at% Al matrix consisting of γ-TiAl and α 2-Ti 3Al compounds were studied. Due to the heat-treatment at 1423 K for various times, four reaction layers were formed; (A) degenerated layer in the periphery of the fiber in which pitts were observed for prolonged heat-treating time, and (B) TiC, (C) Ti 2AlC and (D) Ti 5Si 3 layers in the matrix side. The interfacial debonding between layer (B) and the originally coated C-rich layer observed in the fracture surface of composite samples suggests that the premature fracture of the layers (B)-(D) is not a main reason for the reaction-induced reduction in fiber strength in composites. The tensile strength of the fibers extracted from the composite samples, in which only the layer (A) was contained (the other reaction layers (B)-(D) were removed during extraction), was reduced with increasing heat-treatment time. The reduction could be attributed mainly to the premature fracture of the layer (A) and the pits on its surface.