| There are many aspects of the mechanical behavior of whisker reinforced alloys that are not well understood. The effects of thermal fatigue, for example, have been extensively studied for continuous fiber composites but not for whisker composites. In this study a model was developed for thermal fatigue damage in whisker reinforced metal matrix composites taking into account both metallurgical transformations and thermal stress damage. Also, thermal cycling tests were performed on 2124-T6 aluminum alloy reinforced with a 15% volume fraction of SiC whiskers. The microstructure and mechanical properties of the composite were evaluated before and after thermal cycling.; Unlike metal matrix composites with continuous fibers, the only thermal stress damage sustained by SiC{dollar}sb{lcub}rm w{rcub}{dollar}/Al were changes in dimensions as large as 7.4%. There were no indications of matrix or fiber cracking, void formation, interfacial debonding, or concentrated plastic flow. Thermal stress deformation appears to have been balanced by recovery and recrystallization. The effects of thermal cycling on composite strength were determined to be primarily due to overaging of matrix precipitates. The whiskers accelerated overaging, and may have increased the extent to which overaging could occur. |
