877Metal Matrix Composites

The various grades of Cerme Ti offer higher elevated temperature strength, increased hardness, and improved modulus over the monolithic titanium alloy while maintaining both the fracture toughness and machinability of a metal (albeit more difficult), as opposed to those of a brittle ceramic [19].

The mechanical behavior of Ti-6Al-4V reinforced with continuous SiC fibers is shown in Table 8.12 [7, 33]. Greatly enhanced specific strength is obtained in a2-type titanium aluminide/SiC composites compared to conventional superalloys, with dramatic weight savings of up to 75% by replacing a conventional disc-and-spacer assembly with a titanium aluminide reinforced ring configuration [34].

As a matrix, the richer orthorhombic a2 alloys exhibit increased ambient temperature ductility and enhanced oxidation resistance. However, they are more costly and higher density [13, 14, 19].

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