Titanium aluminide-matrix composites

Metal-Matrix Composites. A metal-matrix composite (MMC) is comprised of a metal ahoy, less than 50% by volume that is reinforced by one or more constituents with a significantly higher elastic modulus. Reinforcement materials include carbides, oxides, graphite, borides, intermetahics or even polymeric products. These materials can be used in the form of whiskers, continuous or discontinuous fibers, or particles. Matrices can be made from metal ahoys of Mg, Al, Ti, Cu, Ni or Fe. In addition, intermetahic compounds such as titanium and nickel aluminides, Ti Al and Ni Al, respectively, are also used as a matrix material (58,59). P/M MMC can be formed by a variety of full-density hot consolidation processes, including hot pressing, hot isostatic pressing, extmsion, or forging. 

Reinforcement for metal-matrix composites with such metals as titanium, titanium aluminide, aluminum, magnesium, and copper. Applications are found mostly in advanced aerospace programs and include fan blades, drive shafts, and other components. 

One candidate is a titanium alioy that is reinforced with iarge diameter SiC/C filaments (see Chapter 4) and is fabricated by superplastic forming/ diffusion bonding. This MMC is suited to the fabrication of bladed compressor rings, shafts, ducks, fan components or structural rods for jet engines. Their use for parts submitted to still higher temperatures is limited by tiber/matrix reaction and environmental considerations. Titanium aluminide TisAI (or y-TiAl) matrices could permit an increase in the service temperature of the composites. 

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