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

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

doi:10.1103/physrevmaterials.3.113603

Cited by 38 publications

(30 citation statements)

References 136 publications

(238 reference statements)

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“…III D for further analyses). Note that a similar correlation has been also found between local VEC and C solution energies in CrMnFeCoNi [67]. Figure 4 shows the distributions of the atomic stresses σ Bader obtained from the Bader analysis for each element in the investigated equiatomic bcc alloys.…”

Section: A Distributions Of Atomic Volumes Charges and Stressessupporting

confidence: 72%

Correlation analysis of strongly fluctuating atomic volumes, charges, and stresses in body-centered cubic refractory high-entropy alloys

Ishibashi

Ikeda

Körmann

et al. 2020

Phys. Rev. Materials

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Local lattice distortions in a series of body-centered cubic alloys, including refractory high-entropy alloys, are investigated by means of atomic volumes, atomic charges, and atomic stresses defined by the Bader charge analysis based on first-principles calculations. Analyzing the extensive data sets, we find large distributions of these atomic properties for each element in each alloy, indicating a large impact of the varying local chemical environments. We show that these local-environment effects can be well understood and captured already by the first and the second nearest neighbor shells. Based on this insight, we employ linear regression models up to the second nearest neighbor shell to accurately predict these atomic properties. Finally, we find that the elementwiseaveraged values of the atomic properties correlate linearly with the averaged valence-electron concentration of the considered alloys.

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Section: A Distributions Of Atomic Volumes Charges and Stressessupporting

confidence: 72%

Correlation analysis of strongly fluctuating atomic volumes, charges, and stresses in body-centered cubic refractory high-entropy alloys

Ishibashi

Ikeda

Körmann

et al. 2020

Phys. Rev. Materials

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“…Given the fact that in particular Fe and Mn in elemental bulk fcc phases are prone to different kinds of antiferromagnetic ordering, we employ in the present study an extended set of calculations where we specifically screen for antiferromagnetic states. For a wide range of compositions including equiatomic CrMnFeCoNi, an antiferromagnetically ({100} layered) ordered state is found to be lower in energy (up to ∼23 meV/atom depending on composition) as compared to the above discussed and previously considered [54,55,58] magnetic state with Mn and Cr moments antiferromagnetically aligned relative to Fe, Co, and Ni moments [55] (a detailed analysis on the impact of magnetism on other properties will be given elsewhere [59,60]). In the present study, we therefore focused on the antiferromagnetic (AFM) state as an alternative representative ordered magnetic state of the fcc phase.…”

Section: A Ab Initio Calculationsmentioning

confidence: 88%

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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“…The lowest ε f value was less than any value recorded by Sun et al [19], Otto et al [18] or Liu et al [20]-a feature that may be related to the inhomogeneous microstructure of the finest grained material noted above-but the largest ε f had been observed by some of these other workers. The carbon appears to result in a greater dislocation density and fewer twins than in the undoped alloys, a feature that the authors ascribed to an increase in the stacking fault energy (SFE): ab initio quantum-mechanical calculations indeed indicate that carbon increases the SFE of CoCrFeMnNi [26]. Table 2.…”

Section: T (K)mentioning

confidence: 99%

Interstitials in f.c.c. High Entropy Alloys

Baker

2020

Metals

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The effects of interstitials on the mechanical properties of single-phase f.c.c. high entropy alloys (HEAs) have been assessed based on a review of the literature. It is found that in nearly all studies, carbon increases the yield strength, in some cases by more than in traditional alloys. This suggests that carbon can be an excellent way to strengthen HEAs. This strength increase is related to the lattice expansion from the carbon. The effects on other mechanical behavior is mixed. Most studies show a slight reduction in ductility due to carbon, but a few show increases in ductility accompanying the yield strength increase. Similarly, some studies show little or modest increases in work-hardening rate (WHR) due to carbon, whereas a few show a substantial increase. These latter effects are due to changes in deformation mode. For both undoped and carbon doped CoCrFeMnNi, the room temperature ductility decreases slightly with decreasing grain size until ~2–5 µm, below which the ductility appears to decrease rapidly. The room temperature WHR also appears to decrease with decreasing grain size in both undoped and carbon-doped CoCrFeMnNi and in nitrogen-doped medium entropy alloy NiCoCr, and, at least for the undoped HEA, shows a sharp decrease at grain sizes <2 µm. Interestingly, carbon has been shown to almost double the Hall–Petch strengthening in CoCrFeMnNi, suggesting the segregation of carbon to the grain boundaries. There have been few studies on the effects of other interstitials such as boron, nitrogen and hydrogen. It is clear that more research is needed on interstitials both to understand their effects on mechanical properties and to optimize their use.

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

Cited by 38 publications

References 136 publications

Correlation analysis of strongly fluctuating atomic volumes, charges, and stresses in body-centered cubic refractory high-entropy alloys

Correlation analysis of strongly fluctuating atomic volumes, charges, and stresses in body-centered cubic refractory high-entropy alloys

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

Interstitials in f.c.c. High Entropy Alloys

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