Longitudinal Fatigue Response of a Metal Matrix Composite Under Strain Controlled Mode at Elevated Temperature

Abstract

The fatigue characteristics of a unidirectional titanium-based metal matrix composite (MMC) (SCS-6/Ti-15-3) were investigated at elevated temperature (427°C). A hybrid strain controlled loading mode was employed for this purpose. This hybrid control mode did not allow the specimen to experience compressive stress in order to prevent any possible buckling effects. To fully understand the fatigue behavior of the MMC under this control mode, fatigue tests, microscopic evaluation, and micromechanical analysis were performed. Based on this combination of activities, the damage and deformation mechanisms were systematically identified. It was found that the fatigue behavior was initially dominated by creep deformation of the matrix. This was accompanied by plastic deformation in those specimens that were subjected to a maximum strain level of 0.55% or higher. Depending on the maximum strain level, the specimen failure was a result of either fiber fracture or matrix cracking. Using the combined approach involving experiments, microscopy, and analysis, the interrelationships among applied strain levels, fatigue life, damage mechanisms, and macroscopic response were established to characterize the longitudinal fatigue characteristics of the tested MMC.