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a b s t r a c tFatigue behavior of a cold-rolled two-phase Al 0.5 CoCrCuFeNi high-entropy alloy (HEA) was studied. Some specimens were fabricated, using commercial-purity raw materials, while others were manufactured with high-purity components. Scatter in the fatigue life of the commercial-purity samples was found in the stress vs. lifetime plot (S-N curve). However, the high-purity samples showed less scatter, and fatigue life is predictable using fatigue statistics. The fatigue property of the alloy is comparable with and may even outperform many commercial alloys. Fatigue cracking is promoted by shrinkage pores with a size of $5 lm, while mechanical nanotwinning was found to be the main deformation mechanism before crack-initiation and during crack propagation by transmission electron microscopy (TEM). Two orientations of dense nanotwins were found at the crack-initiation site, while less-dense nanotwins were found away from the crack initiation site. The nanotwinning behavior resulted in strengthening of the alloy and, consequently, high fatigue strength (383 ± 71 MPa). Moreover, statistical models were applied to predict fatigue life, suggesting that using improved fabrication processes and/or high-purity raw materials may enhance the fatigue behavior and scatter by reducing the number of fabrication microcracks and pores in the test samples.Published by Elsevier Ltd. on behalf of Acta Materialia Inc.

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Detailed metallographic investigations of Gleeble simulated HAZ samples in modified 800H were performed. Precipitate dissolution, grain growth, HAZ liquation and the hardness degradation behavior in modified 800H were also addressed. Results of this study agree with previous HAZ hot cracking and softening behavior evaluations.