High cycle fatigue deformation mechanisms of a single phase CrMnFeCoNi high entropy alloy

High entropy alloys (HEAs) with exceptional mechanical properties have gained a considerable attention in the recent years. Some of these alloys, including the equiatomic, single-phase, face-centered-cubic CrMnFeCoNi alloy with an excellent combination of strength, ductility and fracture toughness at room and cryogenic temperatures have been studied extensively. Still, further studies are required to explain the fatigue behavior and the encountered deformation mechanisms of this class of alloys. In this study, high cycle fatigue behavior of the single-phase CrMnFeCoNi HEA, known as Cantor alloy, has been investigated. S-N curve has been obtained in the range of 10(6) to 10(9) loading cycles by using small-scaled samples and an ultrasonic fatigue test system. Microstructural investigations and fracture surface analyses suggest that cyclic plastic deformation occurs due to the combined interaction of planar slip and deformation twinning at low-stress amplitudes in the very high cycle regime.