Investigation of the Fatigue Behavior of SCS-Ultra/Ti-6-4

Abstract

The focus of this study is to evaluate the fatigue behavior of SCS-Ultra/Ti6-4 at 427⁰C. The improvement in ultimate strength over SCS-6/Ti-6-4 was less than expected and the fatigue lives of the new material were much shorter at all stress levels. Posttest evaluation with a scanning electron microscope revealed several processing flaws in the new composites. Because of these flaws, the SCS-Ultra fibers failed at a lower composite stress than predicted and there were numerous crack initiation sites to greatly accelerate the progression of damage in fatigue tests. Despite the poor fatigue performance of the SCS-Ultra/Ti-6-4 specimens, this material shows promise for greatly increased ultimate strength. Both the stress and strain to failure are greater than SCS-6/Ti-6-4, even with the previously mentioned processing defects.

Keywords

fatigue elevated temperature metal matrix composite silicon carbide titanium

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