Comparison of low cycle fatigue performance of several [0] Sigma fibre reinforced titanium matrix composites

The low cycle fatigue behaviour of four SiC fibre reinforced titanium matrix composites (TMCs) is examined at temperatures relevant to gas-turbine compressor components. It is found that, in the high cyclic stress/short life regime, the fatigue performance of the four TMCs is similar at each temperature. At lower stresses, however, more relevant to the gas-turbine compressor application, fatigue lives of Ti-6-4/SM1240, Timetal 834/SM1140+ and Timetal 834/SM1240 TMC all become significantly inferior to those of Ti-6-4/SM1140+ at temperatures of 450°C and above. This inferiority is attributed to intergranular embrittlement of the Timetal 834 matrix, the high creep resistance of the Timetal 834 matrix and due to an as yet unexplained weakening of the SM1240 fibre.