Ultra-long life fatigue behavior of a high-entropy alloy.

• Gigacycle fatigue behavior of a high-entropy alloy is firstly studied. • Fatigue micro-cracks trend to initiate near a triple junction grain boundary. • The {1 1 0} slip planes may also lead to the fatigue crack initiation, not only preferential {1 1 1} slip planes. Widespread interest has been generated by the high-entropy alloys (HEAs) due to their exceptional ability to combine high plasticity and high strength. However, there is still no comprehensive explanation for their fatigue behavior and crack initiation mechanism in the very high cycle fatigue region up to 109 cycles to the author's best knowledge. This work studied the gigacycle fatigue behavior of a single-phase CoCrFeMnNi HEA. It is found that fatigue failure is caused by casting defects and crystallographic facet. For the case of crystallographic facet just originating from matrix, the fatigue micro-cracks tend to initiate near a triple junction grain boundary. The activation of the {1 1 0} slip planes may also lead to the fatigue crack initiation, not only preferential {1 1 1} slip planes for this alloy. [ABSTRACT FROM AUTHOR]