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Open AccessArticle

Fatigue Behaviour and Crack Initiation in CoCrFeNiMn High-Entropy Alloy Processed by Powder Metallurgy

1
Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, 616 62 Brno, Czech Republic
2
Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Za Slovankou 1782/3, 182 00 Praha, Czech Republic
*
Author to whom correspondence should be addressed.
Metals 2019, 9(10), 1110; https://doi.org/10.3390/met9101110
Received: 24 September 2019 / Revised: 9 October 2019 / Accepted: 14 October 2019 / Published: 17 October 2019
Single-phase equiatomic five-element high entropy alloy CoCrFeMnNi was prepared by powder metallurgy. Two materials with ultra-fine-grained microstructure were prepared by spark plasma sintering (SPS) of ball-milled powder at two sintering times (5 and 10 min), assigned as HEA 5 and HEA 10, respectively. Basic microstructural and mechanical properties were evaluated. The median grain size of the microstructures was determined to be 0.4 and 0.6 μm for HEA 5 and HEA 10, respectively. The differences in the microstructure led to a significant change in strength and deformation characteristics evaluated at room temperature. The effect of cyclic loading was monitored by three-point bending fatigue test. The results show that even relatively small change in the microstructure causes a significant effect on fatigue life. The fatigue endurance limit was measured to be 1100 MPa and 1000 MPa for HEA 5 and HEA 10, respectively. The detailed fractographic analysis revealed that abnormally large grains, localised in the microstructure on the tensile loaded surface, were a typical fatigue initiation site. The formation of (nano) twins together with dislocation slips caused the crack nucleation because of the cyclic loading. View Full-Text
Keywords: high entropy alloy; microstructure; spark plasma sintering; fatigue; grain size high entropy alloy; microstructure; spark plasma sintering; fatigue; grain size
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MDPI and ACS Style

Chlup, Z.; Fintová, S.; Hadraba, H.; Kuběna, I.; Vilémová, M.; Matějíček, J. Fatigue Behaviour and Crack Initiation in CoCrFeNiMn High-Entropy Alloy Processed by Powder Metallurgy. Metals 2019, 9, 1110.

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