Eutectic Reaction and Microstructure Stability in CoCrFeNiNbx High-Entropy Alloys

Cao, Xu; Wu, Changjun; Liu, Ya; Peng, Haoping; Su, Xuping

doi:10.3390/met12050756

Open AccessArticle

Eutectic Reaction and Microstructure Stability in CoCrFeNiNb_x High-Entropy Alloys

by

Xu Cao

¹,

Changjun Wu

^1,2,*

,

Ya Liu

^1,2

,

Haoping Peng

¹ and

Xuping Su

^1,3

¹

Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Changzhou 213164, China

²

National Experimental Teaching Demonstration Center of Materials Science and Engineering, School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China

³

Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Changzhou University, Changzhou 213164, China

^*

Author to whom correspondence should be addressed.

Metals 2022, 12(5), 756; https://doi.org/10.3390/met12050756

Submission received: 20 March 2022 / Revised: 18 April 2022 / Accepted: 26 April 2022 / Published: 28 April 2022

(This article belongs to the Special Issue Plastic Forming, Microstructure, and Property Optimization of Metals)

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Abstract

Seven arc-melted and then annealed CoCrFeNiNb_x (x = 0.3–0.6) alloys are experimentally and thermodynamically investigated in the present work. All the as-cast and 1000 °C annealed CoCrFeNiNb_x alloys are composed of face-centered cubic (FCC) and C14 Laves phases. Nb content in the C14 phase stays at around 24.5 at.%, and the Liquid → FCC + C14 eutectic reaction occurred at around 10.8 at.% Nb in a narrow temperature range. It is found that the microstructure in the CoCrFeNiNb_x alloys is dramatically affected by the cooling rate and annealing treatment. The C14 phase easily spheroidizes and coarsens under high temperature, which indicates that the interface energy between FCC and C14 is very large. Moreover, the solubility of Nb in the FCC phase decreases with decreasing temperature. After annealing at 800 °C, a needle-like nano Mg₃Cd-type τ phase precipitates from the pro-eutectic FCC phase and increases alloy hardness for ~100 HV. This should be a method to strengthen alloys.

Keywords: high-entropy alloys; C14 Laves phase; eutectic structure; microstructure stability; phase diagram

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MDPI and ACS Style

Cao, X.; Wu, C.; Liu, Y.; Peng, H.; Su, X. Eutectic Reaction and Microstructure Stability in CoCrFeNiNb_x High-Entropy Alloys. Metals 2022, 12, 756. https://doi.org/10.3390/met12050756

AMA Style

Cao X, Wu C, Liu Y, Peng H, Su X. Eutectic Reaction and Microstructure Stability in CoCrFeNiNb_x High-Entropy Alloys. Metals. 2022; 12(5):756. https://doi.org/10.3390/met12050756

Chicago/Turabian Style

Cao, Xu, Changjun Wu, Ya Liu, Haoping Peng, and Xuping Su. 2022. "Eutectic Reaction and Microstructure Stability in CoCrFeNiNb_x High-Entropy Alloys" Metals 12, no. 5: 756. https://doi.org/10.3390/met12050756

APA Style

Cao, X., Wu, C., Liu, Y., Peng, H., & Su, X. (2022). Eutectic Reaction and Microstructure Stability in CoCrFeNiNb_x High-Entropy Alloys. Metals, 12(5), 756. https://doi.org/10.3390/met12050756

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Eutectic Reaction and Microstructure Stability in CoCrFeNiNb_x High-Entropy Alloys

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