High Temperature Structural Materials for Advanced Air Force Systems
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7960 S. Kolb Rd, Tucson, AZ, 85706
Dr S Guha
AbstractConventional composite processing techniques are presently unable to fabricate Al1O3-fiber reinforced y-titanium aluminide matrix composites based on low cost, small diameter ( 5-20um) fibers. The primary problem is one of infiltration of the matrix in between the fibers without any degradation in fiber properties. Although pressure casting would be a low cost processing approach, the severe chemical attack by molten metals would limit the performance of these composites. Instead, an innovative composite processing technique for TiAl-based composites will be demonstrated wherein, starting with a commercial Al2O3 fiber tow, each fiber will be spread and individually coated with the matrix material by a plasma-assisted hollow cathode sputtering process. The fiber volume fraction within the matrix can be varied by varying the thickness of the coating. By coating all the fibers to a given thickness, a more or less constant inter -fiber spacing can be obtained in a hot-consolidated state. Such a composite processing technique is also amenable to tailoring of the fiber-matrix interface by the addition of vary thin coat of metals such as Nb for improved resistance to chemical attack by the matrix. This Nb layer can also act as a compliant layer, thereby improving the thermal cycling performance of these composites.
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