Determination of latent hardening response for FeNiCoCrMn for twin-twin interactions

Alkan, S.; Ojha, A.; Şehitoğlu, Hüseyin

doi:10.1016/j.actamat.2017.12.058

Cited by 45 publications

(13 citation statements)

References 64 publications

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“…The WHR of AM SS 316 L rapidly decreases and remain almost constant around 1000 MPa, whereas AM CrCoNi shows a rapid decrease, rather increases (Stage II), and gradually decreases until fracture. The four-stage response has been known as a characteristic of low SFE fcc metals and the stage II often includes primary twinning and its migration 36,37 and/or martensitic transformation 38 . Besides, the necking criterion (dσ/dε = σ) predicts a delayed necking occurrence of AM CrCoNi (38%) compared to the AM SS 316 L (33%).…”

Section: Resultsmentioning

confidence: 99%

“…The critical twinning stress (σ tw ) is described as an equivalent stress of importance to form sufficient stacking faults followed by the measureable deformation twins 8,37 . Several theoretical or phenomenological approaches have determined the σ tw using TEM 8,9 , neutron diffraction 12 or first-principle calculation based on energy barriers of stacking/twin faults 10,37 . It has been estimated for the CrCoNi alloy as 790 ± 100 MPa using TEM 9 , 890 MPa by first-principle calculation 10 , and 680-770 MPa by a numerical model by Steinmetz et al 36…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

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: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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

View full text Add to dashboard Cite

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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%

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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“…A key factor in controlling the underlying deformation mechanism and therewith tuning the mechanical properties is the stacking fault energy (SFE). Low SFEs can induce, e.g., transformation- induced plasticity (TRIP) or twinning-induced plasticity (TWIP) [ 14 , 15 , 16 ], and for this reason, SFEs of HEAs and CCAs have been investigated previously in numerous experimental [ 13 , 17 , 18 , 19 ] as well as theoretical studies [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ]. Interestingly, in a recent experimental work [ 17 ], the measured SFEs for equiatomic CrMnFeCoNi revealed large fluctuations, and it was proposed that the SFEs of CrMnFeCoNi may sensitively depend on the local chemical environments in the vicinity of the stacking faults (SFs).…”

Section: Introductionmentioning

confidence: 99%

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

Ikeda

Körmann

Tanaka

et al. 2018

Entropy

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Medium and high entropy alloys (MEAs and HEAs) based on 3d transition metals, such as face-centered cubic (fcc) CrCoNi and CrMnFeCoNi alloys, reveal remarkable mechanical properties. The stacking fault energy (SFE) is one of the key ingredients that controls the underlying deformation mechanism and hence the mechanical performance of materials. Previous experiments and simulations have therefore been devoted to determining the SFEs of various MEAs and HEAs. The impact of local chemical environment in the vicinity of the stacking faults is, however, still not fully understood. In this work, we investigate the impact of the compositional fluctuations in the vicinity of stacking faults for two prototype fcc MEAs and HEAs, namely CrCoNi and CrMnFeCoNi by employing first-principles calculations. Depending on the chemical composition close to the stacking fault, the intrinsic SFEs vary in the range of more than 150 mJ/m 2 for both the alloys, which indicates the presence of a strong driving force to promote particular types of chemical segregations towards the intrinsic stacking faults in MEAs and HEAs. Furthermore, the dependence of the intrinsic SFEs on local chemical fluctuations reveals a highly non-linear behavior, resulting in a non-trivial interplay of local chemical fluctuations and SFEs. This sheds new light on the importance of controlling chemical fluctuations via tuning, e.g., the annealing condition to obtain the desired mechanical properties for MEAs and HEAs.

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Determination of latent hardening response for FeNiCoCrMn for twin-twin interactions

Cited by 45 publications

References 64 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

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

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

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