Microstructure evolution and critical stress for twinning in the CrMnFeCoNi high-entropy alloy

Laplanche, Guillaume; Kostka, Aleksander; Horst, Oliver Martin; Eggeler, Gunther; George, E.P.

doi:10.1016/j.actamat.2016.07.038

Cited by 869 publications

(309 citation statements)

References 56 publications

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“…11,14,15 To obtain the equilibrium atomic configuration, we performed a CMC simulation for 10,000 MC steps using a sample with 5760 atoms at 1073 K. Periodic boundary conditions were applied to all directions, and atomic vibration and change in sample dimensions were allowed during the simulation. The results are presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Micro-twining mechanism at cryogenic temperatures Micro-twins have been experimentally observed in most HEAs during deformation, [2][3][4]8,15 particularly at 77 K, and are regarded as a probable reason for excellent tensile properties at 77 K. Previous studies claimed that the low stacking fault energy (SFE) of HEAs is one of the probable reasons for the micro-twinning. 27,28 However, it is not fully understood why HEAs have a low SFE.…”

Section: Resultsmentioning

confidence: 99%

“…Sluggish diffusion, [11][12][13] severe lattice distortion 14 and microtwinning [2][3][4]8,15 have been mentioned as probable reasons for the typical HEA properties. However, exact mechanisms for such structural reasons are not clearly known yet.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

et al. 2018

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Although high-entropy alloys (HEAs) are attracting interest, the physical metallurgical mechanisms related to their properties have mostly not been clarified, and this limits wider industrial applications, in addition to the high alloy costs. We clarify the physical metallurgical reasons for the materials phenomena (sluggish diffusion and micro-twining at cryogenic temperatures) and investigate the effect of individual elements on solid solution hardening for the equiatomic CoCrFeMnNi HEA based on atomistic simulations (Monte Carlo, molecular dynamics and molecular statics). A significant number of stable vacant lattice sites with high migration energy barriers exists and is thought to cause the sluggish diffusion. We predict that the hexagonal close-packed (hcp) structure is more stable than the face-centered cubic (fcc) structure at 0 K, which we propose as the fundamental reason for the micro-twinning at cryogenic temperatures. The alloying effect on the critical resolved shear stress (CRSS) is well predicted by the atomistic simulation, used for a design of non-equiatomic fcc HEAs with improved strength, and is experimentally verified. This study demonstrates the applicability of the proposed atomistic approach combined with a thermodynamic calculation technique to a computational design of advanced HEAs.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

et al. 2018

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“…Laplanche et al [8] performed TEM analyses of the CoCrFeMnNi HEA using interrupted tensile specimens to determine the widths of the nanoscale mechanical twins, and spacings between twins. In this study, the widths and spacings of the mechanical twins were measured using their method.…”

Section: Methodsmentioning

confidence: 99%

“…Otto et al [7] provided microstructural evidence for the formation of deformation twins in CoCrFeMnNi HEA after a tensile strain of 20.2% at 77 K. In addition, Laplanche et al [8] reported that the formation of nanoscale twins in the CoCrFeMnNi HEA began at a lower true strain of ∼ 6% during tensile tests at 77 K. In spite of several efforts, there remains a diversity of opinion about the role of twins in FCC HEAs at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

On the strain rate-dependent deformation mechanism of CoCrFeMnNi high-entropy alloy at liquid nitrogen temperature

Moon

Hong

Bae

et al. 2017

Materials Research Letters

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(2017) On the strain rate-dependent deformation mechanism of CoCrFeMnNi highentropy alloy at liquid nitrogen temperature, Materials Research Letters, 5:7, 472-477, DOI: 10.1080/21663831.2017 ABSTRACTIn the present work, the deformation mechanisms of the CoCrFeMnNi high-entropy alloy at 77 K were investigated using thermal activation analyses. The strain rate jump test was performed to estimate strain rate sensitivity and the activation volume of the alloy. Transmission electron microscopy analyses were performed to identify the evolution of twins at low temperatures. The insensitivity of activation volume to strain observed in the CoCrFeMnNi alloy at 77 K was different from the observed increase in the activation volume with strain at room temperature, which occurred due to the shearing of nanoscale inhomogeneities, such as co-clusters and short-range orders. IMPACT STATEMENTThe insensitivity of the activation volume to plastic strain in the CoCrFeMnNi alloy at 77 K can be attributed to the increasing fraction of mechanical twinning with strain. ARTICLE HISTORY

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High‐Entropy Alloys: Potential Candidates for High‐Temperature Applications – An Overview

2017

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Multi-principal elemental alloys, commonly referred to as high-entropy alloys (HEAs), are a new class of emerging advanced materials with novel alloy design concept. Unlike the design of conventional alloys, which is based on one or at most two principal elements, the design of HEA is based on multi-principal elements in equal or near-equal atomic ratio. The advent of HEA has revived the alloy design perception and paved the way to produce an ample number of compositions with different combinations of promising properties for a variety of structural applications. Among the properties possessed by HEAs, sluggish diffusion and strength retention at elevated temperature have caught wide attention. The need to develop new materials for high-temperature applications with superior high-temperature properties over superalloys has been one of the prime concerns of the high-temperature materials research community. The current article shows that HEAs have the potential to replace Ni-base superalloys as the next generation hightemperature materials. This review focuses on the phase stability, microstructural stability, and high-temperature mechanical properties of HEAs. This article will be highly beneficial for materials science and engineering community whose interest is in the development and understanding of HEAs for high-temperature applications.

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Microstructure evolution and critical stress for twinning in the CrMnFeCoNi high-entropy alloy

Cited by 869 publications

References 56 publications

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

On the strain rate-dependent deformation mechanism of CoCrFeMnNi high-entropy alloy at liquid nitrogen temperature

High‐Entropy Alloys: Potential Candidates for High‐Temperature Applications – An Overview

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