Potentials of Orthorhombic Titanium Aluminide Composites

摘要

Future aerospace applications require materials with ever increasing temperature and load-bearing capabilities. Continuous SiC fibre-reinforced titanium metal matrix composites (TMCs) exhibit the potential for meeting these requirements and are particularly attractive for use in aircraft gas turbine engines owing to their specific mechanical properties at high temperature. Changing conventional titanium alloys matrices (Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo) to a titanium aluminide of the Orthorhombic type (Ti_2AlNb) which possesses a higher temperature capability will extend potential aero-engine applications of TMCs. Two different Orthorhombic alloys were considered in the present study and compared to a Ti-6Al-2Sn-4Zr-2Mo matrix. The composites were manufactured by a matrix-coated fibre process using the SM 1140+ silicon carbide fibre monofilament (O 108μm). Cyclic oxidation tests in air at 600 and 700℃ were performed on Orthorhombic and Ti-6Al-2Sn-4Zr-2Mo alloys ; they revealed the better oxidation resistance of the two Ti_2AlNb alloys. Mechanical properties of the SM 1140+/Ti_2AlNb and SM 1140+/Ti-6Al-2Sn-4Zr-2Mo composites have been assessed through tensile tests performed in the temperature range 20-700℃. The results show the influence of the chemical composition of the Orthorhombic alloy on the composite strength and the advantage of an Orthorhombic matrix beyond 500℃.