Maximum strength and dislocation patterning in multi–principal element alloys

Cao, Penghui

doi:10.1126/sciadv.abq7433

Cited by 52 publications

(5 citation statements)

References 34 publications

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“…This process requires additional work to overcome the energy barrier due to the change of alteration of the local chemical environments, which was confirmed by the experimental observation of nanotwins and very thin HCP phase in deformed HEAs [38,39]. Recent experimental and computational studies also reveal that LCO affects the slip mode of dislocation and deformation behaviors [3,40].…”

Section: Mechanical Properties and Deformation Behaviorsmentioning

confidence: 76%

Impact of local chemical ordering on deformation mechanisms in single-crystalline CuNiCoFe high-entropy alloys: a molecular dynamics study

Shuang,

Liang,

Zhang

et al. 2023

Modelling Simul. Mater. Sci. Eng.

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High-entropy alloys (HEAs), composed of multiple constituent elements with concentrations ranging from 5% to 35%, have been considered ideal solid solution of multi-principal elements. However, recent experimental and computational studies have demonstrated that complex enthalpic interactions among constituents lead to a wide variety of local chemical ordering (LCO) at lower temperatures. HEAs containing Cu typically decompose by forming of Cu-rich phases during annealing, thus affecting mechanical properties. In this study, CuNiCoFe HEA was chosen as a model with a tendency for Cu segregation at low temperatures. The formation of LCO and its impact on the deformation behaviors in the single-crystalline CuNiCoFe HEA were studied via molecular dynamics simulations. Our results demonstrate that CuNiCoFe HEA decomposes by Cu clustering, in agreement with prior experimental and computational studies, owing to insufficient configuration entropy to compete against the mixing enthalpy at lower temperatures. A softening in ultimate stress in the LCO models was observed compared to the random solid solution models. The softening is due to the lower unstable stacking fault energy, which determines the nucleation event of dislocations, thereby rationalizing the dislocation nucleation in the Cu-rich regions and the softening of the overall ultimate strength in the LCO models. Additionally, the inhomogeneous FCC-BCC transformation is closely associated with concentration inhomogeneity. CuNiCoFe HEA with LCO can be regarded as composites, consisting of clusters with different properties. Consequently, concentration inhomogeneity induced by LCO profoundly impacts the mechanical properties and deformation behaviors of the HEA. This study provides insights into the effect of LCO on the mechanical properties of CuNiCoFe HEAs, which is crucial for developing HEAs with tailored properties for specific applications.

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Section: Mechanical Properties and Deformation Behaviorsmentioning

confidence: 76%

Impact of local chemical ordering on deformation mechanisms in single-crystalline CuNiCoFe high-entropy alloys: a molecular dynamics study

Shuang,

Liang,

Zhang

et al. 2023

Modelling Simul. Mater. Sci. Eng.

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“…The observation of rejuvenation in a quenched CrCoNi MEA after cyclic destruction of SRO offers critical insights into the impact of SRO on the mechanical performance of HEAs/MEAs, giving us a greater understanding of why certain HEAs/MEAs shows a combination of high strength and ductility. Previous MD simulations have shown that SRO in the CrCoNi MEA can lead to an increase in yield strength 13,38 . Furthermore, recent studies revealed that SRO can promote work hardening and thus enhance ductility 15 .…”

Section: Discussionmentioning

confidence: 97%

Rejuvenation as the origin of planar defects in the CrCoNi medium entropy alloy

Yang,

Yin,

et al. 2024

Nat Commun

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High or medium- entropy alloys (HEAs/MEAs) are multi-principal element alloys with equal atomic elemental composition, some of which have shown record-breaking mechanical performance. However, the link between short-range order (SRO) and the exceptional mechanical properties of these alloys has remained elusive. The local destruction of SRO by dislocation glide has been predicted to lead to a rejuvenated state with increased entropy and free energy, creating softer zones within the matrix and planar fault boundaries that enhance the ductility, but this has not been verified. Here, we integrate in situ nanomechanical testing with energy-filtered four-dimensional scanning transmission electron microscopy (4D-STEM) and directly observe the rejuvenation during cyclic mechanical loading in single crystal CrCoNi at room temperature. Surprisingly, stacking faults (SFs) and twin boundaries (TBs) are reversible in initial cycles but become irreversible after a thousand cycles, indicating SF energy reduction and rejuvenation. Molecular dynamics (MD) simulation further reveals that the local breakdown of SRO in the MEA triggers these SF reversibility changes. As a result, the deformation features in HEAs/MEAs remain planar and highly localized to the rejuvenated planes, leading to the superior damage tolerance characteristic in this class of alloys.

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“…It can be observed that the density of the alloy presents a trend of increasing and the melting point is also on a trend of increasing with the increment of Cr content. From the predicted values, the density of the current alloys with varied Cr elements ranges between 6.25-6.32 g/cm 3 , and the melting point is in the range of 1247-1282 • C. Compared to the Inconel 718 superalloy with a density of 8.19 g/cm 3 , the density values of all the designed compositions of the alloys were less than 7 g/cm 3 , which is beneficial for lightweight superalloys with higher service temperatures. Thus, Cr 0.6 HEA has great potential to become an alternative material to meet the requirements of lightweight development in the aviation and aerospace industries.…”

Section: Constitutional-phase Formation and Microstructure Evolution ...mentioning

confidence: 99%

“…High-entropy alloys (HEAs) and multiprincipal element alloys have received considerable interest for community experts and have become a worldwide hot spot since Cantor and Yeh reported their first publication [1,2]. Cr-containing HEAs have exhibited promising potential when applied in high-temperature industrial fields as a result of their remarkable strength [3][4][5][6], favorable ductility [7][8][9], distinguished corrosion resistance [10][11][12], superior wear and oxidation resistance [13][14][15], and acceptable thermal stability [16,17].…”

Section: Introductionmentioning

confidence: 99%

Effects of Cr Content on Microstructure and Mechanical Properties of Co-Free FeCryNiAl0.8 High-Entropy Alloys

et al. 2023

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High-entropy alloys have gained widespread concern in response to the increased requirements for future high-temperature structural superalloys. By combining phase-diagram calculations with microhardness, compression behavior measurements at room temperature, and elevated temperature conditions, the very important role of the Cr element on the microstructure and properties is deeply revealed, which provides candidates materials for future high-temperature alloy applications. The increment of Cr favors the regulation of the two-phase fraction and distribution. The thermodynamic calculations illustrate that the density and melting point of the HEAs showed an increasing trend with the increase of the Cr content. The typical worm-like microstructure of the Cr0.6 alloy with a dual BCC structure was detected. Meanwhile, on the one hand, the increment of the Cr elements results in a considerable optimization of the mechanical properties of the alloy in terms of strength and ductility at room temperature. The corresponding compressive strength and plasticity of Cr0.6 alloy at room temperature are 3524 MPa and 43.3%. On the other hand, the high-temperature mechanical properties of the alloy are greatly enhanced. At 1000 °C, the yield strength of the Cr0.6 alloy is about 25 MPa higher than that of the Cr0.4 alloy. The superior mechanical properties are attributed to the pronounced work-hardening response, and the work-hardening behavior of Cr-containing HEAs was systematically analyzed by employing the modified Ludwik model. The higher content of Cr helps the resistance of the local deformation response, improving the nonuniform strain and promoting the balance of strength and ductility of the alloys.

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Maximum strength and dislocation patterning in multi–principal element alloys

Cited by 52 publications

References 34 publications

Impact of local chemical ordering on deformation mechanisms in single-crystalline CuNiCoFe high-entropy alloys: a molecular dynamics study

Impact of local chemical ordering on deformation mechanisms in single-crystalline CuNiCoFe high-entropy alloys: a molecular dynamics study

Rejuvenation as the origin of planar defects in the CrCoNi medium entropy alloy

Effects of Cr Content on Microstructure and Mechanical Properties of Co-Free FeCryNiAl0.8 High-Entropy Alloys

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