Thermal fatigue of Ti-24Ai-11NB/SCS-6

The effect of thermally cycling in air with no applied load was studied using the Ti-24A1-11Nb (atomic percent)/SCS-6 composite system. Mechanisms of damage determination were observable cracking and residual tensile properties. Either the number of cycles or the temperature range was varied from specimen to specimen. Effects of number of cycles were investigated using a temperature range of 150 °C to 815 °C. Comparisons of temperature range effects were made at a constant cycle count of 500. Matrix cracking was observed at a †T of 450 °C and greater when oxidation was significant. Transverse cracking was not observed in specimens that were cycled to maximum temperatures where oxidation was insignificant, even for †T's as large as 500 °C. A decrease in tensile properties coincided with the observed transverse matrix cracking. This paper is based on a presentation made in the symposium “Interfaces and Surfaces of Titanium Materials” presented at the 1988 TMS/AIME fall meeting in Chicago, IL, September 25–29, 1988, under the auspices of the TMS Titanium Committee.