Damage evolution during thermal fatigue of a unidirectional SCS-6/Ti-24Al-11Nb metal matrix composite

摘要

Metal matrix composites (MMCs) reinforced with continuous fibres have received considerableinterests as the materials under severe service conditions, because they generally possess manyattractive characteristics: higher specific strength and higher specific stiffness, compared withtraditional monolithic materials. While these materials are on the way of improvements anddevelopment, there remain many works to be understood, or clarified. In this work thermal fatiguetests of an unidirectional SiC fiber reinforced Ti-24Al-llNb matrix composite were carried out undervarious conditions with maximum temperature and temperature range without external load in air.The fiber employed was aβ-SiC fiber of 140μm diameter with a carbon rich graded silicon carbidecoating on the surface: SCS6. During the study, special attentions were paid to understand whatdamage is produced by the application of thermal cycle, how the damage evolves, and how thethermal fatigue life should be evaluated, taking account of the change of reaction zone near thefiber/matrix interface. Based on the experimental observations, a simple method how to assess thethermal fatigue damage was discussed and proposed.