Tensile properties of high- and medium-entropy alloys

Gali, Aravind; George, E.P.

doi:10.1016/j.intermet.2013.03.018

Cited by 969 publications

(436 citation statements)

References 28 publications

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“…Micro-twining mechanism at cryogenic temperatures Micro-twins have been experimentally observed in most HEAs during deformation, [2][3][4]8,15 particularly at 77 K, and are regarded as a probable reason for excellent tensile properties at 77 K. Previous studies claimed that the low stacking fault energy (SFE) of HEAs is one of the probable reasons for the micro-twinning. 27,28 However, it is not fully understood why HEAs have a low SFE.…”

Section: Resultsmentioning

confidence: 99%

“…1 Particularly, the equiatomic CoCrFeMnNi HEAs have been reported to possess a wide-range of promising properties such as good hightemperature structural stability 2,3 and an excellent balance between strength and ductility, particularly at cryogenic temperatures, typically 77 K, the liquid nitrogen temperature. 4 Even though most HEAs have equiatomic or near equiatomic compositions, it is believed that the equiatomic composition would not be the optimum composition for a wide range of material properties.…”

Section: Introductionmentioning

confidence: 99%

“…Sluggish diffusion, [11][12][13] severe lattice distortion 14 and microtwinning [2][3][4]8,15 have been mentioned as probable reasons for the typical HEA properties. However, exact mechanisms for such structural reasons are not clearly known yet.…”

Section: Introductionmentioning

confidence: 99%

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Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

et al. 2018

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Although high-entropy alloys (HEAs) are attracting interest, the physical metallurgical mechanisms related to their properties have mostly not been clarified, and this limits wider industrial applications, in addition to the high alloy costs. We clarify the physical metallurgical reasons for the materials phenomena (sluggish diffusion and micro-twining at cryogenic temperatures) and investigate the effect of individual elements on solid solution hardening for the equiatomic CoCrFeMnNi HEA based on atomistic simulations (Monte Carlo, molecular dynamics and molecular statics). A significant number of stable vacant lattice sites with high migration energy barriers exists and is thought to cause the sluggish diffusion. We predict that the hexagonal close-packed (hcp) structure is more stable than the face-centered cubic (fcc) structure at 0 K, which we propose as the fundamental reason for the micro-twinning at cryogenic temperatures. The alloying effect on the critical resolved shear stress (CRSS) is well predicted by the atomistic simulation, used for a design of non-equiatomic fcc HEAs with improved strength, and is experimentally verified. This study demonstrates the applicability of the proposed atomistic approach combined with a thermodynamic calculation technique to a computational design of advanced HEAs.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

et al. 2018

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“…One of the most studied single-phase HEAs is the equiatomic CoCrFeNiMn alloy [3][4][5]. The high temperature mechanical properties of this alloy were studied earlier but to date the occurrence of superplasticity has not been reported in this HEA [4,[6][7][8][9]. It is well established that superplastic flow requires a very small grain size [10] and this may be achieved most readily through the application of severe plastic deformation (SPD) [11,12].…”

Section: Introductionmentioning

confidence: 99%

Evidence for superplasticity in a CoCrFeNiMn high-entropy alloy processed by high-pressure torsion

Shahmir

Liu

et al. 2017

Materials Science and Engineering: A

104

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A CoCrFeNiMn high-entropy alloy was processed by high-pressure torsion to produce a grain size of ~10 nm and then tested in tension at elevated temperatures from 773 to 1073 K using strain rates in the range from 1.0 × 10 -3 to 1.0 × 10 -1 s -1 . The alloy exhibited excellent ductility at these elevated temperatures including superplastic elongations with a maximum elongation of >600% at a testing temperature of 973 K. It is concluded that the formation of precipitates and the sluggish diffusion in the HEA inhibit grain growth and contribute to a reasonable stability of the fine-grained structure at elevated temperatures. The results show the activation energy for flow matches the anticipated value for grain boundary diffusion in nickel but the strain rate sensitivity is low due to the occurrence of some grain growth at these high testing temperatures.

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“…The strengthening of CoCrFeMnNi HEA, which is controlled by thermally activated deformation, is more dependent on temperature than that of conventional FCC metals [9]. Nevertheless, there is a lack of systematic investigation on the thermally activated process of deformation in HEAs.…”

Section: Introductionmentioning

confidence: 99%

On the strain rate-dependent deformation mechanism of CoCrFeMnNi high-entropy alloy at liquid nitrogen temperature

Moon

Hong

Bae

et al. 2017

Materials Research Letters

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(2017) On the strain rate-dependent deformation mechanism of CoCrFeMnNi highentropy alloy at liquid nitrogen temperature, Materials Research Letters, 5:7, 472-477, DOI: 10.1080/21663831.2017 ABSTRACTIn the present work, the deformation mechanisms of the CoCrFeMnNi high-entropy alloy at 77 K were investigated using thermal activation analyses. The strain rate jump test was performed to estimate strain rate sensitivity and the activation volume of the alloy. Transmission electron microscopy analyses were performed to identify the evolution of twins at low temperatures. The insensitivity of activation volume to strain observed in the CoCrFeMnNi alloy at 77 K was different from the observed increase in the activation volume with strain at room temperature, which occurred due to the shearing of nanoscale inhomogeneities, such as co-clusters and short-range orders. IMPACT STATEMENTThe insensitivity of the activation volume to plastic strain in the CoCrFeMnNi alloy at 77 K can be attributed to the increasing fraction of mechanical twinning with strain. ARTICLE HISTORY

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Tensile properties of high- and medium-entropy alloys

Cited by 969 publications

References 28 publications

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

Understanding the physical metallurgy of the CoCrFeMnNi high-entropy alloy: an atomistic simulation study

Evidence for superplasticity in a CoCrFeNiMn high-entropy alloy processed by high-pressure torsion

On the strain rate-dependent deformation mechanism of CoCrFeMnNi high-entropy alloy at liquid nitrogen temperature

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