Effect of Atomic Size Difference on the Microstructure and Mechanical Properties of High-Entropy Alloys.

Chan-Sheng Wu,Ping-Hsiu Tsai,Che-Wei Tsai,Chia-Ming Kuo

doi:10.3390/e20120967

Chan-Sheng Wu, Ping-Hsiu Tsai + Show 2 more

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https://doi.org/10.3390/e20120967

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Journal: Entropy	Publication Date: Dec 14, 2018
Citations: 36	License type: CC BY 4.0

Affiliation: National Tsing Hua University

Abstract

The effects of atomic size difference on the microstructure and mechanical properties of single face-centered cubic (FCC) phase high-entropy alloys are studied. Single FCC phase high-entropy alloys, namely, CoCrFeMnNi, Al0.2CoCrFeMnNi, and Al0.3CoCrCu0.3FeNi, display good workability. The recrystallization and grain growth rates are compared during annealing. Adding Al with 0.2 molar ratio into CoCrFeMnNi retains the single FCC phase. Its atomic size difference increases from 1.18% to 2.77%, and the activation energy of grain growth becomes larger than that of CoCrFeMnNi. The as-homogenized state of Al0.3CoCrCu0.3FeNi high-entropy alloy becomes a single FCC structure. Its atomic size difference is 3.65%, and the grain growth activation energy is the largest among these three kinds of single-phase high-entropy alloys. At ambient temperature, the mechanical properties of Al0.3CoCrCu0.3FeNi are better than those of CoCrFeMnNi because of high lattice distortion and high solid solution hardening.

Highlights

A multi-principal-element alloying system, developed by Yeh et al in 2004 [1,2], is called high-entropy alloy (HEA)
A lattice is highly distorted because all atoms are solutes that can disorderly fill in a face-centered cubic (FCC) or body-centered cubic (BCC) lattice, and atomic sizes differ among elements in this alloying system, thereby possessing strengthening effect in high-solid-soluted HEAs [4]
The comparison result of the microstructure between Al0.2 CoCrFeMnNi and Al0.3 CoCrCu0.3 FeNi single FCC-type high-entropy alloys according to X-ray diffraction (XRD) analysis in Figures 2 and 3 shows that the assingle FCC-type high-entropy alloys according to XRD analysis in Figures 2 and 3 shows that the homogenized state and the furnace-cooled state both have outstanding phase stability without any as-homogenized state and the furnace-cooled state both have outstanding phase stability without detrimental non-FCC phases regardless of the cooling condition

Summary

Introduction

A multi-principal-element alloying system, developed by Yeh et al in 2004 [1,2], is called high-entropy alloy (HEA). HEAs are defined as equiatomic or near-equiatomic alloys containing at least five elements, whose atomic concentration ranges from 5% to 35%. The multiprincipal-elemental mixtures of HEAs result in high entropy, lattice distortion, sluggish diffusion, and cocktail effects [3]. High entropy causes single-phase structures to become stable; as such, HEAs usually consist of simple solid solution phases with face-centered cubic (FCC) and body-centered cubic (BCC) structures rather than other intermetallic compounds [2]. A lattice is highly distorted because all atoms are solutes that can disorderly fill in a FCC or BCC lattice, and atomic sizes differ among elements in this alloying system, thereby possessing strengthening effect in high-solid-soluted HEAs [4]. Lattice distortion impedes atomic movement and slows down the diffusion rate of atoms in HEAs; these conditions lead to higher recrystallization temperatures, that is, the activation energies of grain growth in deformed

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Conclusion