Damage evolution during thermal fatigue of a unidirectional SCS-6/Ti-24Al-11Nb metal matrix composite
Okazaki Masakazu; Hayashi Keijiroh; Nakatani Hiroshi
Abstract:Metal matrix composites (MMCs) reinforced with continuous fibres have received considerable interests as the materials under severe service conditions, because they generally possess many attractive characteristics: higher specific strength and higher specific stiffness, compared with traditional monolithic materials. While these materials are on the way of improvements and development, there remain many works to be understood, or clarified. In this work thermal fatigue tests of a unidirectional SiC fiber reinforced Ti-24Al-11Nb matrix composite were carried out under various conditions with maximum temperature and temperature range without external load in air. The fiber employed was a b SiC fiber of 140mm diameter with a carbon rich graded silicon carbide coating on the surface: SCS-6. During the study, special attentions were paid to understand what damage is produced by the application of thermal cycle, how the damage evolves, and how the thermal fatigue life should be evaluated, taking account of the change of reaction zone near the fiber/matrix interface. Based on the experimental observations, a simple method how to assess the thermal fatigue damage was discussed and proposed. Key Words:Ti-24Al-11Nb matrix composite, SiC fiber, thermal fatigue, crack density, interface, life assessment