On the significance of matrix microstructure in fatigue strength of a unidirectional SCS-6/SP700 titanium alloy matrix composite

The effect of matrix microstructure on the fatigue strength of a SP700 titanium alloy matrix composite unidirectionally reinforced with SiC fibre, SCS-6, has been studied. Three kinds of composite materials associated with different matrix microstructure were prepared by giving the different heat treatments at elevated temperatures below and above the β-transus temperature of the matrix alloy after the fabrication process. The load-controlled high-cycle fatigue tests were conducted under a stress ration of 0.1 at room temperature in air. It was shown that the fatigue strength was significantly changed by the matrix microstructure. The mechanism was discussed, based on the measurement of the interfacial shear strength by the fibre push-out tests and the fatigue properties of the matrix alloy.