INFLUENCE OF INTERFACIAL REACTION ON TENSILE-STRENGTH OF SIC FIBER EMBEDDED IN A GAMMA-TITANIUM-ALUMINIDE ALLOY

The influences of interfacial reaction on tensile strength of continuo us SiC fiber (SCS-6. Textron Specialty Materials) embedded in the Ti-4 8 at% Al matrix consisting of gamma-TiAl and alpha(2)-Ti3Al compounds were studied. Due to the heat-treatment at 1423 K for various times, f our reaction layers were formed. (A) degenerated laver in the peripher y of the fiber in which pitts were observed for prolonged heat-treatin g time. and (B) TIC. (C) Ti2AlC and (D) Ti5Si3 layers in the matrix si de. The interfacial debonding between layer (B) and the originally coa ted C-rich layer observed in the fracture surface of composite samples suggests that the premature fracture of the layers (B)-(D) is not a m ain reason for the reaction-induced reduction in fiber strength in com posites. The tensile strength of the fibers extracted from the composi te samples. in which only the layer (A) was contained (the other react ion layers (B)-(D) were removed during extraction). uas reduced with i ncreasing heat-treatment time. The reduction could be attributed mainl y to the premature fracture of the layer (A) and the pits on its surfa ce.