Deformation faulting in a metastable CoCrNiW complex concentrated alloy: A case of negative intrinsic stacking fault energy?

Wei, Shaolou; Taşan, Cemal Cem

doi:10.1016/j.actamat.2020.09.056

Cited by 65 publications

(11 citation statements)

References 108 publications

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“…The curves, in Figure 5 a,b, show that the inclined stacking fault starts with an intense light line at the intersection of the defect with the surface (x = 0 nm). For increasing x values, the calculated contrast fades with oscillations in agreement with experimental ECC images of twin boundary ( Figure 1 ) and stacking fault (Figure 12 in [ 6 ]). Furthermore, the more the inclination angle θ is important the more the spatial periods T and T’ (indicated, respectively, by the green and the blue lines in Figure 5 a,b) become lower (T ≈ 5 nm, T’ ≈ 50 nm for θ = 45°, and T ≈ 2 nm, T’ ≈ 18 nm for θ = 70°), and the more the contrast fades quickly.…”

Section: Theoretical Modelssupporting

confidence: 85%

“…For example, the CrMnFeCoNi high entropy alloy exhibit at room temperature deformation by dislocation slip whereas at very low temperature stacking faults and twinning act in addition [ 5 ]. Recent work has shown that the stacking faults role is predominant in response to loading in CoCrNiW metastable alloy [ 6 ]. On the other hand, the presence of such defects in materials for optoelectronic devices induces local strains leading to the degradation of their performances [ 7 , 8 ].…”

Section: Introductionmentioning

confidence: 99%

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Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

2021

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In a scanning electron microscope, the backscattered electron intensity modulations are at the origin of the contrast of like-Kikuchi bands and crystalline defects. The Electron Channeling Contrast Imaging (ECCI) technique is suited for defects characterization at a mesoscale with transmission electron microscopy-like resolution. In order to achieve a better comprehension of ECCI contrasts of twin-boundary and stacking fault, an original theoretical approach based on the dynamical diffraction theory is used. The calculated backscattered electron intensity is explicitly expressed as function of physical and practical parameters controlling the ECCI experiment. Our model allows, first, the study of the specimen thickness effect on the channeling contrast on a perfect crystal, and thus its effect on the formation of like-Kikuchi bands. Then, our theoretical approach is extended to an imperfect crystal containing a planar defect such as twin-boundary and stacking fault, clarifying the intensity oscillations observed in ECC micrographs.

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Section: Theoretical Modelssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

2021

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“…Since our trained model(s) are capable of predicting SFEs over the entire range (from negative to positive values), possible targets include TWIP, TRIP, TWIP/TRIP deformation mechanisms. We note that even the micro-faulting mechanism due to negative intrinsic SFE recently reported by Wei and Tasan [92] can potentially be a target for our multi-objective optimization.…”

Section: Overcoming the Strength-ductility Trade-off Through Sfe Engi...mentioning

confidence: 87%

Towards Stacking Fault Energy Engineering in FCC High Entropy Alloys

Khan,

Kirk,

Vazquez

et al. 2021

Preprint

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Stacking Fault Energy (SFE) is an intrinsic alloy property that governs much of the plastic deformation mechanisms observed in fcc alloys. While SFE has been recognized for many years as a key intrinsic mechanical property, its inference via experimental observations or prediction using, for example, computationally intensive first-principles methods is challenging. This difficulty precludes the explicit use of SFE as an alloy design parameter. In this work, we combine DFT calculations (with necessary configurational averaging), machine-learning (ML) and physics-based models to predict the SFE in the fcc CoCrFeMnNiV-Al high-entropy alloy space. The best-performing ML model is capable of accurately predicting the SFE of arbitrary compositions within this 7-element system. This efficient model along with a recently developed model to estimate intrinsic strength of fcc HEAs is used to explore the strength-SFE Pareto front, predicting new-candidate alloys with particularly interesting mechanical behavior.

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“…3(b1)] were firstly Gaussian fitted to determine the FCC peak positions and to calculate the corresponding d-spacings. The peak shifting phenomena mentioned in "Initial microstructure and diffraction profile evolution during heating" section are next quantified by the apparent lattice strain [50]:…”

Section: Defect Content Evolution During Reverse Austenitic Transform...mentioning

confidence: 99%

An in situ synchrotron X-ray study of reverse austenitic transformation in a metastable FeMnCo alloy

Wei

Kang

Taşan

2022

Journal of Materials Research

Self Cite

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This study concerns reverse austenitic transformation of plastic strain-induced hexagonal close-packed martensite. With the aid of in situ synchrotron X-ray diffractometry, the kinetic features of the transformation and the defect content evolution in a metastable (Fe60Mn40)85Co15 alloy are quantitatively examined using 5, 20, and 100 °C/min heating rates. It is found that the reverse austenitic transformation can be activated below 200 °C and completes within a short time scale. Through a Kissinger-style kinetic analysis, the activation energy of the reverse austenitic transformation is determined as 171.38 kJ/mol, confirming its displacive nature. Although exponential attenuation is observed in both stacking fault probability and dislocation density upon the initiation of the transformation, the resulting microstructure (single-phase face-centered cubic structure) remains highly defected, exhibiting high Vickers hardness, but still preserving somewhat strain hardenability. Atomistic mechanisms for the reverse austenitic transformation are further conceived according to the crystallographic theory of martensitic transformation. Graphical abstract

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Deformation faulting in a metastable CoCrNiW complex concentrated alloy: A case of negative intrinsic stacking fault energy?

Cited by 65 publications

References 108 publications

Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

Towards Stacking Fault Energy Engineering in FCC High Entropy Alloys

An in situ synchrotron X-ray study of reverse austenitic transformation in a metastable FeMnCo alloy

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