Atomic displacement in the CrMnFeCoNi high-entropy alloy – A scaling factor to predict solid solution strengthening

Norihiko L Okamoto,Haruyuki Inui,Koretaka Yuge,Easo P George,Katsushi Tanaka

doi:10.1063/1.4971371

Norihiko L Okamoto, Haruyuki Inui + Show 3 more

Open Access

https://doi.org/10.1063/1.4971371

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Journal: AIP Advances	Publication Date: Dec 1, 2016
Citations: 193	License type: cc-by

Affiliation: Kyoto University, Kobe University

Abstract

Although metals strengthened by alloying have been used for millennia, models to quantify solid solution strengthening (SSS) were first proposed scarcely seventy years ago. Early models could predict the strengths of only simple alloys such as dilute binaries and not those of compositionally complex alloys because of the difficulty of calculating dislocation-solute interaction energies. Recently, models and theories of SSS have been proposed to tackle complex high-entropy alloys (HEAs). Here we show that the strength at 0 K of a prototypical HEA, CrMnFeCoNi, can be scaled and predicted using the root-mean-square atomic displacement, which can be deduced from X-ray diffraction and first-principles calculations as the isotropic atomic displacement parameter, that is, the average displacements of the constituent atoms from regular lattice positions. We show that our approach can be applied successfully to rationalize SSS in FeCoNi, MnFeCoNi, MnCoNi, MnFeNi, CrCoNi, CrFeCoNi, and CrMnCoNi, which are all medium-entropy subsets of the CrMnFeCoNi HEA.

Highlights

One of the ways in which alloying elements strengthen metals is by solid solution strengthening (SSS): solute atoms dissolved in a solvent matrix offer resistance to the motion of dislocations thereby making the material stronger
We investigate the magnitude of the average atomic displacement in the quinary equiatomic high-entropy alloys (HEAs) CrMnFeCoNi using single-crystal synchrotron X-ray diffraction and firstprinciples calculations, in order to determine whether it can be used as an alternative scaling factor to predict SSS
For this we utilize the results of Wu et al.[35] who recently investigated the temperature dependence of the yield strength of polycrystals of the quinary CrMnFeCoNi HEA and some of its derivative face-centered cubic (FCC) quaternary and ternary equiatomic alloys with similar grain sizes so that the grain boundary effect can be ignored to first order

Summary

Introduction

We investigate the magnitude of the average atomic displacement in the quinary equiatomic HEA CrMnFeCoNi using single-crystal synchrotron X-ray diffraction and firstprinciples calculations, in order to determine whether it can be used as an alternative scaling factor to predict SSS. In order to estimate the atomic radius for each of the constituent elements in the quinary HEA, the relaxed supercell volumes were calculated for five hypothetical quaternary alloys with different combinations of four of the five elements (MnFeCoNi, CrFeCoNi, CrMnCoNi, CrMnFeNi and CrMnFeCo).

Results

Conclusion