Impact of Chemical Fluctuations on Stacking Fault Energies of CrCoNi and CrMnFeCoNi High Entropy Alloys from First Principles

Ikeda, Yûji; Körmann, Fritz; Tanaka, Isao; Neugebauer, Jörg

doi:10.3390/e20090655

Cited by 85 publications

(39 citation statements)

References 69 publications

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“…The SFEs of fcc austenitic steels, particularly of high-Mn steels, have empirically been known to correlate with their deformation behaviors [63][64][65][66][67]. Also for 3d-transitionelement-based HEAs, their SFEs have also been measured in experiments [8,17,26,[68][69][70][71] and computed based on firstprinciples simulations [72][73][74][75][76][77][78][79][80][81][82][83][84]. While the impact of C atoms on the SFEs of HEAs has also been discussed in experimental fcc hcp FIG.…”

Section: A Stacking-fault Energymentioning

confidence: 99%

“…In first-principles simulations for 0 K, negative SFEs are rather common for 3d-transition-element-based HEAs [76][77][78][80][81][82]84,127,128]. Various factors such as lattice vibrations [12,78,81], magnetic fluctuations [12,73,127], chemical short-range order [82], and chemical fluctuations close to the stacking faults [83,128] are known to substantially modify the absolute value of the SFEs. In addition, a recent firstprinciples study found that a potential Cr sublattice ordering could further increase the SFE of CrCoNi [82].…”

Section: A Phase Stability and Sfe Of The Interstitial-free Crmnfeconimentioning

confidence: 99%

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Impact of interstitial C on phase stability and stacking-fault energy of the CrMnFeCoNi high-entropy alloy

Ikeda

Tanaka

Neugebauer

et al. 2019

Phys. Rev. Materials

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Interstitial alloying in CrMnFeCoNi-based high-entropy alloys is known to modify their mechanical properties. Specifically, strength can be increased due to interstitial solid-solution hardening, while simultaneously affecting ductility. In this paper, first-principles calculations are carried out to analyze the impact of interstitial C atoms on CrMnFeCoNi in the fcc and the hcp phases. Our results show that C solution energies are widely spread and sensitively depend on the specific local environments. Using the computed solution-energy distributions together with statistical mechanics concepts, we determine the impact of C on the phase stability. C atoms are found to stabilize the fcc phase as compared to the hcp phase, indicating that the stacking-fault energy of CrMnFeCoNi increases due to C alloying. Using our extensive set of first-principles computed solution energies, correlations between them and local environments around the C atoms are investigated. This analysis reveals, e.g., that the local valence-electron concentration around a C atom is well correlated with its solution energy.

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Section: A Stacking-fault Energymentioning

confidence: 99%

Section: A Phase Stability and Sfe Of The Interstitial-free Crmnfeconimentioning

confidence: 99%

Impact of interstitial C on phase stability and stacking-fault energy of the CrMnFeCoNi high-entropy alloy

Ikeda

Tanaka

Neugebauer

et al. 2019

Phys. Rev. Materials

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“…The advantage of this method is that it is possible to calculate several alloy compositions with less effort than the one required for an experimental determination of the same alloys. So far, the systems CoCrFeMnNi [9,10,13,14], AlCoCrCuFeNi, and AlCoCrFeNi [15] have been investigated regarding their SFE. A comprehensive list can be found in Reference [12].…”

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confidence: 99%

“…A comprehensive list can be found in Reference [12]. First-principle methods have even allowed the constructions of property maps, where the SFE can be read as a function of the chemical composition [14], which can be used to predict the expected physical acting mechanisms. The experimental determination of the SFE, although it is arguably more laborious, is as important as its computational calculation because, as accurate as they are, ab initio calculations still rely on a model, which may not be accurate for some conditions.…”

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confidence: 99%

From High-Manganese Steels to Advanced High-Entropy Alloys

Haase

Barrales‐Mora

2019

Metals

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Arguably, steels are the most important structural material, even to this day. Numerous design concepts have been developed to create and/or tailor new steels suited to the most varied applications. High-manganese steels (HMnS) stand out for their excellent mechanical properties and their capacity to make use of a variety of physical mechanisms to tailor their microstructure, and thus their properties. With this in mind, in this contribution, we explore the possibility of extending the alloy design concepts that haven been used successfully in HMnS to the recently introduced high-entropy alloys (HEA). To this aim, one HMnS steel and the classical HEA Cantor alloy were subjected to cold rolling and heat treatment. The evolution of the microstructure and texture during the processing of the alloys and the resulting properties were characterized and studied. Based on these results, the physical mechanisms active in the investigated HMnS and HEA were identified and discussed. The results evidenced a substantial transferability of the design concepts and more importantly, they hint at a larger potential for microstructure and property tailoring in the HEA. several core effects (high-entropy effect, sever lattice distortion effect, sluggish diffusion effect, cocktail effect) of HEAs have been proposed [5], a clear design strategy is still missing.The underlying physical mechanisms active in HMnS have already been studied for several decades [1,2,6], and therefore are comparatively well understood. One of the most important parameters when designing HMnS is the tailoring of their stacking fault energy (SFE). This property controls the dissociation distance of partial dislocations and determines whether TRIP and/or TWIP is activated/suppressed during plastic deformation. The role of the SFE during plastic deformation and subsequent heat treatment in metals has been studied for decades, and its effect is relatively well-known for face-centered cubic (fcc) metals [7]. In fcc HEAs, the mechanisms of microstructure formation have been found to occur in a similar way to the same class of alloys with comparable SFE [8]. For instance, the Cantor alloy (CoCrFeMnNi) with an estimated SFE between 18.3-27.3 mJ/m 2 [9,10] has been shown to develop the TWIP effect, depending on the processing conditions [11]. Evidently, the determination of the SFE in HEAs is fundamental, because this property indicates the possible acting mechanisms for microstructure development. However, as with steels, the complex chemistry of HEAs leads to almost unlimited combinations that make a systematic determination of this property difficult. Nevertheless, to accelerate the development of these alloys, several research groups have made use of ab initio calculations, e.g., [12]. The advantage of this method is that it is possible to calculate several alloy compositions with less effort than the one required for an experimental determination of the same alloys. So far, the systems CoCrFeMnNi [9,10,13,14], AlCoCrCuFeNi, and AlCoCrFeNi [15] have been investig...

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“…Ab initio calculations have been successfully utilized to estimate the SFEs of various HEAs. To take the effect of magnetic ordering and VEC upon SFE into consideration, in the present study we further employ ab initio calculations to efficiently screen for quinary compositions based on the SFEs [1,30,[34][35][36][37][38][39][40][41] and design nonequiatomic HEAs with TRIP and/or TWIP. We first computationally screen for SFEs of alloys in the quasiternary Cr 20 Mn x Fe y Co 20 Ni z (x + y + z = 60, at.…”

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confidence: 99%

Role of magnetic ordering for the design of quinary TWIP-TRIP high entropy alloys

Rao

et al. 2020

Phys. Rev. Materials

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We reveal the impact of magnetic ordering on stacking fault energy (SFE) and its influence on the deformation mechanisms and mechanical properties in a class of nonequiatomic quinary Mn-containing compositional complex alloys or high entropy alloys (HEAs). By combining ab initio simulation and experimental validation, we demonstrate magnetic ordering as an important factor in the activation and transition of deformation modes from planar dislocation slip to TWIP (twinning-induced plasticity) and/or TRIP (transformation-induced plasticity). A wide compositional space of Cr 20 Mn x Fe y Co 20 Ni z (x + y + z = 60, at. %) was probed by density-functional theory calculations to search for potential alloys displaying the TWIP/TRIP effects. Three selected promising HEA compositions with varying Mn concentrations were metallurgically synthesized, processed, and probed for microstructure, deformation mechanism, and mechanical property evaluation. The differences in the deformation modes of the probed HEAs are interpreted in terms of the computed SFEs and their dependence on the predicted magnetic state, as revealed by ab initio calculations and validated by explicit magnetic measurements. It is found that the Mn content plays a key role in the stabilization of antiferromagnetic configurations which strongly impact the SFEs and eventually lead to the prevalent deformation behavior.

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Impact of Chemical Fluctuations on Stacking Fault Energies of CrCoNi and CrMnFeCoNi High Entropy Alloys from First Principles

Cited by 85 publications

References 69 publications

Impact of interstitial C on phase stability and stacking-fault energy of the CrMnFeCoNi high-entropy alloy

Impact of interstitial C on phase stability and stacking-fault energy of the CrMnFeCoNi high-entropy alloy

From High-Manganese Steels to Advanced High-Entropy Alloys

Role of magnetic ordering for the design of quinary TWIP-TRIP high entropy alloys

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