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Microstructural Evolution from Dendrites to Core-Shell Equiaxed Grain Morphology for CoCrFeNiVx High-Entropy Alloys in Metallic Casting Mold

Department of Materials Science and Engineering, North China University of Technology, Beijing 100144, China
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Metals 2019, 9(11), 1172; https://doi.org/10.3390/met9111172
Received: 30 September 2019 / Revised: 24 October 2019 / Accepted: 29 October 2019 / Published: 30 October 2019
(This article belongs to the Special Issue Rapid Solidification Processing)
The CoCrFeNiVx (x = 0, 0.25, 0.5, 0.7, 0.8, 0.9, and 1.0) high-entropy alloys (HEAs) were fabricated by the copper mold casting process. The microstructure, phase constitution, and mechanical properties were investigated by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy analyses and compressive testing. It revealed that, when x ≤ 0.25, the alloys solidified into a single fcc phase. When 0.5 ≤ x ≤ 0.8, the alloys solidified into a dendritic structure of the fcc phase with the formation of the σ phase in the interdendrite region. Interestingly, when x exceeded 0.9, the alloys presented a typical core-shell equiaxed grain morphology. The core region consisting of a mixture of fcc + σ phases was surrounded by the shell of the single σ phase and the interdendrite region solidified into the single fcc phase. The dual-phase “eutectiod” structure in the core region of the equiaxed grain might be formed from the decomposition of the unidentified metastable phase. As the V fraction increased, the compressive yield strength of the CoCrFeNiVx alloys gradually increased from 164 MPa (x = 0) to 458 MPa (x = 0.8), and then sharply increased to 722 MPa (x = 0.9) and 1493 MPa (x = 1.0). View Full-Text
Keywords: high-entropy alloy; solidification; microstructure; sluggish diffusion high-entropy alloy; solidification; microstructure; sluggish diffusion
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Cao, L.; Zhu, L.; Shi, H.; Wang, Z.; Yang, Y.; Meng, Y.; Zhang, L.; Cui, Y. Microstructural Evolution from Dendrites to Core-Shell Equiaxed Grain Morphology for CoCrFeNiVx High-Entropy Alloys in Metallic Casting Mold. Metals 2019, 9, 1172.

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