MICROSTRUCTURALLY TOUGHENED INTERMETALLIC MATRIX COMPOSITES

SUCCESSFUL DEVELOPMENT OF HYPERSONIC FLIGHT VEHICLES AND ENGINES WILL DEPEND HEAVILY UPON RAPID DEVELOPMENT OF NEW, HIGH-TEMPERATURE METAL MATRIX COMPOSITE (MMC'S). FIBER REINFORCED TITANIUM ALUMINIDE ALLOYS HAVE GREAT POTENTIAL TO MEET THE ENGINEERING REQUIREMENTS OF SUCH STRUCTURES. CONSIDERABLE EFFORT HAS GONE INTO DEVELOPING THESE MMC'S WITH LARGE-DIAMETER SILICON CARBIDE FIBERS (5.6 MIL MONOFILAMENTS), AND MECHANICAL PROPERTIES HAVE BEEN IMPRESSIVE. HOWEVER THE TOUGHNESS HAS BEEN TOO LOW FOR DAMAGE-TOLERANT STRUCTURAL APPLICATIONS. RECENT DEVELOPMENTS IN THE MANUFACTURE OF MMC'S BY VAPOR DEPOSITIONMETHODS OFFER THE PROSPECT OF PRODUCING POLYPHASE MICROCOMPOSITE PRECURSORS IN THE FORM OF CONTINUOUS MONOFILAMENTS OR THIN MONOTAPES CONTAINING FIBER IN THE DESIRED VOLUME FRACTION, DIFFUSION BARRIERS, TITANIUM ALUMINIDE MATRIX, AND DUCTILE HIGH TEMPERATURE INTERPHASE FOR CRACK ARREST. PHASE I WILL ESTABLISH THE FEASIBILITY OFSUCH MMC MONOTAPES, DEMONSTRATE THIN-GAUGE COMPOSITE PANELS CONSOLIDATED FROM SUCH TAPES, AND DEVELOP PRELIMINARY PROCESS STRUCTURE/PROPERTY RELATIONSHIPS TO ESTABLISH THEIR POTENTIAL FOR STRUCTURAL USE AT TEMPERATURES ABOVE 1000 DEGREES CENTIGRADE, PHASE II WOULD DEMONSTRATE PILOT SCALE PRODUCTION OF PRECURSORS AND FABRICABILITY OF COMPLEX STRUCTURAL SHAPES.