Tensile properties of duplex metal-coated SiC fiber and titanium alloy matrix composites

Abstract

SiC(SCS-6) fiber-reinforced titanium alloy matrix composites have a great potential for high-temperature aerospace structural applications. It is known that the interface reaction between the outermost SCS coating and Ti alloy matrix takes place during the fabrication process, and the formed reaction layer consists of a nonstoichiometric carbide (TiC{sub 1{minus}x}) and silicides (Ti{sub x}Si{sub y}). The reaction layer is brittle; however, this has only a slight effect on the quasi-static tensile strength. On the other hand, the effect of the reaction layer cracking on the fatigue damage evolution is quite severe. Such cracking under a cyclic fatigue loading condition leads to debonding of the SCS coating layer from the SiC fiber surface, which leads to a significant reduction in the fiber strength, because the debonding increases stress concentration at the SiC fiber surface, which originates from surface flaws of the fiber.