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 600degreesC has been investigated. Single fiber tensile tests are performed at 600degreesC and the resulting Weibull strength distribution is compared with the room temperature distribution. The 600degreesC characteristic strength is found to be only 7.6% smaller than that at room temperature. Fibers extracted from loaded-unloaded specimens at 600degreesC show more failures than expected on the basis of the 600degreesC Weibull strength distribution determined as manufactured fibers. From this and other experiments it is concluded, that the in-situ tensile strength of fibers at 600degreesC (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 similar to100 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.