Fiber Dominant Tensile and Creep Strength at 600°C of SCS-6 Fiber Reinforced Titanium Alloys

The influence of the fiber strength on the unidirectional tensile and creep strength at 600°C has been investigated. Single fiber tensile tests are performed at 600°C and the resulting Weibull strength distribution is compared with the room temperature distribution. The 600°C characteristic strength is found to be only 7.6% smaller than that at room temperature. Fibers extracted from loaded-unloaded specimens at 600°C show more failures than expected on the basis of the 600°C Weibull strength distribution determined as manufactured fibers. From this and other experiments it is concluded, that the in-situ tensile strength of fibers at 600°C (embedded in the titanium) is smaller than that of manufactured fibers. Relaxation behavior of the unreinforced titanium alloys was investigated and described with the aid of Bailey-Norton creep law. This enables description of the stress redistribution during creep of the unidirectional composites performed in short time creep experiments up to ∼100 h. The creep strength has been described considering stress relaxation in the matrix and slow defect growth in the fibers. From the shape of the creep strength-life curve it is concluded that three different ranges of defect growth contribute to the creep strength.