Influence of deformation induced nanoscale twinning and FCC-HCP transformation on hardening and texture development in medium-entropy CrCoNi alloy

Slone, C.E.; Chakraborty, Supriyo; Miao, Junwei; George, E.P.; Mills, Michael J.; Niezgoda, Stephen R.

doi:10.1016/j.actamat.2018.07.028

Cited by 167 publications

(43 citation statements)

References 44 publications

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“…It shows the hcp stacking (BABAB) with the sharing of the same {111} habit plane (B stacking layer) as a coherent atomic matching nano-twin boundary. Similar hcp structure observed favorably within the nanotwins (so-called nanotwin-hcp lamella composite) has been reported in CrCoNi alloys 6,7 . Besides, Fig.…”

Section: Resultssupporting

confidence: 82%

“…2(d) shows also the columnar grain structure. It should be mentioned that the mean grain size is about 42 μm along x, which is relatively larger than typically found in cast-wrought annealed CrCoNi alloys (13-24 μm) [6][7][8] . Considering comparable tensile properties between cast-wrought and AM CrCoNi alloys, the dominant strengthening factor is highly relevant to the deformation twinning rather than the initial grain size in AM CrCoNi.…”

Section: Resultsmentioning

confidence: 70%

“…2(f) at the strain of 58%. It highlights that 85% of misorientation angles have 60° rotation about the [111] direction, which is known as Σ3 type twin boundaries 6,7,28 . Figure 3(b,c) compares the local grain texture between as-built and deformed AM CrCoNi specimens with the analysis area of 1142 × 856 μm 2 .…”

Section: Resultsmentioning

confidence: 99%

“…www.nature.com/scientificreports www.nature.com/scientificreports/ Microstructure characterization by TEM. Extensive TEM analyses have been reported in case of cast-wrought type stainless steels 16,[18][19][20][21] and CrCoNi alloys [5][6][7][8][9] . High resolution TEM images clearly show the nanoscale deformation twinning and strain-induced martensitic transformation in both alloys.…”

Section: Resultsmentioning

confidence: 99%

“…dissociating a perfect dislocation into Shockley partial dislocations and considered as a surface tension pulling the partials, which is inversely proportional to the equilibrium distance between two partials 14 . The key issue of the CrCoNi MEA is the low SFE, which creates a wide stacking fault ribbon limiting the cross slip deformation mode and provides the superior mechanical properties by the dominant deformation twinning [6][7][8][9][10][11] . Up to date, Laplanche et al 9 reported the SFE of 22 ± 4 mJ/m 2 in CrCoNi MEA, which is ~25% lower than CrCoNiFeMn HEA (30 ± 4 mJ/m 2 ) and Liu et al reported as 18 ± 4 mJ/m 2 in CrCoNi MEA and 26.5 ± 4.5 mJ/ m 2 in CrCoNiFeMn HEA using TEM 2,11 .…”

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confidence: 99%

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Stacking Fault Energy Analyses of Additively Manufactured Stainless Steel 316L and CrCoNi Medium Entropy Alloy Using In Situ Neutron Diffraction

Woo

Jeong

Kim

et al. 2020

Sci Rep

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Stacking fault energies (SFE) were determined in additively manufactured (AM) stainless steel (SS 316 L) and equiatomic CrCoNi medium-entropy alloys. AM specimens were fabricated via directed energy deposition and tensile loaded at room temperature. In situ neutron diffraction was performed to obtain a number of faulting-embedded diffraction peaks simultaneously from a set of (hkl) grains during deformation. The peak profiles diffracted from imperfect crystal structures were analyzed to correlate stacking fault probabilities and mean-square lattice strains to the SFE. The result shows that averaged SFEs are 32.8 mJ/m 2 for the AM SS 316 L and 15.1 mJ/m 2 for the AM crconi alloys. Meanwhile, during deformation, the SFE varies from 46 to 21 mJ/m 2 (AM SS 316 L) and 24 to 11 mJ/m 2 (AM crconi) from initial to stabilized stages, respectively. The transient SFEs are attributed to the deformation activity changes from dislocation slip to twinning as straining. The twinning deformation substructure and atomic stacking faults were confirmed by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The significant variance of the SFE suggests the critical twinning stress as 830 ± 25 MPa for the AM SS 316 L and 790 ± 40 MPa for AM CrCoNi, respectively.Excellent combination of strength, ductility, and toughness has been found in an equiatomic, face-centered-cubic CrCoNiFeMn high-entropy alloys (HEA) 1 . The reason of the exceptional properties at cryogenic temperature has been mainly attributed to the evolution of the nanoscale twinning under plastic deformation, so-called twinning-induced plasticity 2,3 . Compared to the HEA, superior mechanical properties of CrCoNi medium-entropy alloys (MEA) have been recently reported at both room and cryogenic temperature 4-13 . High attention has been focused on the evolution of the twinning substructure and/or a new phase with hexagonal close packed structure instead of the initial deformation mode of the dislocation slip in MEAs 6-9 . Systematic examinations of the substructure elucidate that the critical twinning stress of 790 ± 100 MPa reaches at the earlier strain of 9.7-12.9% for CrCoNi MEA than 720 ± 30 MPa at ~25% for CrCoNiFeMn HEA because of higher yield strength and work hardening rate with larger shear modulus of the MEA 8-10 . Earlier formation of the nano-twinning and its activation over a more extended strain range is of importance accepted as the reason of the exceptional strength-ductility-toughness combination in MEA.Stacking fault energy (SFE) has been accepted as a responsible parameter to determine the deformation schemes, which is typically by slip (>45 mJ/m 2 ) to twinning (20-45 mJ/m 2 ) and/or phase transformation (<20 mJ/m 2 ) as often reported in austenitic stainless steels [14][15][16][17][18][19][20][21] . The SFE is defined as the energy per fault area by www.nature.com/scientificreports www.nature.com/scientificreports/ SFE ranges 11-24 mJ/m 2 , b p is the magnitude of the Burgers vector of partials (0.146 nm), G is the shear...

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Stacking Fault Energy Analyses of Additively Manufactured Stainless Steel 316L and CrCoNi Medium Entropy Alloy Using In Situ Neutron Diffraction

Woo

Jeong

Kim

et al. 2020

Sci Rep

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Strategies for Achieving Strength–Ductility Synergy in Face‐Centered Cubic High‐ and Medium‐Entropy Alloys

et al. 2023

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High‐ and medium‐entropy alloys (HEAs/MEAs), also called as multicomponent alloys, are a new class of materials that break through the traditional alloy design concept based on single principal element. However, they do not break away from the magic spell of strength–ductility trade‐off. Therefore, designing HEAs/MEAs with both high strength and high ductility still remains a great challenge nowadays. This article provides a review on the recent progress in mechanical properties of face‐centered cubic (FCC) HEAs/MEAs. First, several traditional strengthening strategies are briefly reviewed, focusing on the strengthening mechanisms and the optimized mechanical properties. Subsequently, various novel strategies for achieving strength–ductility synergy in HEAs/MEAs are summarized, which include lowering the stacking fault energy, regulating the short‐range order, promoting transformation‐induced plasticity, and constructing heterogeneous microstructures. The basic ideas and related underlying mechanisms from these strategies are discussed. Finally, the current challenges and the future outlooks are emphasized and addressed systematically. In brief, the present review is expected to provide a useful guide for the design of HEAs/MEAs with superior mechanical properties.

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A Novel Approach for Rapid Material Library Generation Using Laser‐Remelting

Gaag,

Heidowitzsch,

Galgon

et al. 2023

Adv Eng Mater

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Cost‐ and time‐demanding trial‐and‐error methods have been the historical route for alloy development. A combinatorial approach can significantly simplify and accelerate the development process by characterization of composition dependent properties on material libraries, which are specimens or sets of specimens that map out a certain composition space, often employing composition profiles. Herein, a promising production method for such a material library is proposed: laser‐remelting of stacked blocks of different compositions is evaluated for its suitability to produce material libraries, using the ternary CrCoNi system for a proof‐of‐concept. The composition profiles of the successfully created CrCoNi material library were measured by electron probe micro analysis. The intermixing has a length of about 2.5 mm. An analytical model describing the intermixing process is proposed and shows value in the estimation of the intermixing length after the first melting step. The comparison of the experimental microstructure observations from this work and from literature shows mostly good agreement with some deviations related to microsegregation and finite quenching cooling rates, which is supported by thermodynamic calculations regarding phase stability. In the single‐phase region, the mechanical properties as measured via microhardness indentation are discussed as potential candidates for model validation.

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Influence of deformation induced nanoscale twinning and FCC-HCP transformation on hardening and texture development in medium-entropy CrCoNi alloy

Cited by 167 publications

References 44 publications

Stacking Fault Energy Analyses of Additively Manufactured Stainless Steel 316L and CrCoNi Medium Entropy Alloy Using In Situ Neutron Diffraction

Stacking Fault Energy Analyses of Additively Manufactured Stainless Steel 316L and CrCoNi Medium Entropy Alloy Using In Situ Neutron Diffraction

Strategies for Achieving Strength–Ductility Synergy in Face‐Centered Cubic High‐ and Medium‐Entropy Alloys

A Novel Approach for Rapid Material Library Generation Using Laser‐Remelting

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