Damage Evolution in Creep of SCS-6/Ti-24AI-11Nb Metal-Matrix Composites

Abstract

Titanium aluminide composites reinforced with SiC fibers belong to a family of an emerging class of new materials suited for advanced aerospace structural ap plication. However, these materials are yet to be characterized for elevated temperature mechanical behavior and their failure mechanism. During flight, the structural com ponents of advanced aircraft undergo sustained loading for extended periods of time. These materials must show satisfactory creep resistance before they can be recommended for actual use. This investigation deals with the experimental study of creep behavior of a model SCS-6/Ti-24Al-11Nb composite. The main objective of this study is to understand the damage evolution under sustained load at high temperature in this class of material. Tensile creep tests were conducted over the temperature range of 650 to 815°C. All the tests were conducted in laboratory air on specimens fabricated from umdirectional panels. The specimens were loaded with tensile axis parallel to (0) fiber The strain vs. time plot produced a classical creep behavior with three distinct regions. The total creep strain to failure was found to be less than the strain for fiber failure. Evidence of fiber failure was observed as early as in the initial part of the secondary stage.