Fatigue behavior of Al0.5CoCrCuFeNi high entropy alloys

Research was performed on an Al_0.5CoCrCuFeNi high entropy alloy (HEA) in an attempt to study the fatigue behavior. The present fatigue investigation shows encouraging fatigue resistance characteristics due to the prolonged fatigue lives of various samples at relatively high stresses. The current results indicate that the fatigue behavior of HEAs compares favorably with many conventional alloys, such as steels, titanium alloys, and advanced bulk metallic glasses with a fatigue endurance limit of between 540 and 945 MPa and a fatigue endurance limit to ultimate tensile strength ratio of between 0.402 and 0.703. Some unpredictability in the fatigue life of the samples was observed as scattering in the stress vs. lifetime plot. Weibull models were applied to predict the fatigue data and to characterize the variability seen in the HEAs. A Weibull mixture predictive model was used to separate the data into two, strong and weak, groups. This model predicts that at stresses above 858 MPa the median time to failure of specimens in the strong group will be greater than 10⁷ cycles. It was shown that microstructural defects, such as aluminum oxide inclusions and microcracks, may have a significant effect on the fatigue behavior of HEAs. It is believed that a reduction in the number of these defects may result in a fatigue behavior which exceeds that of conventional alloys.