Dislocation creep behavior of CoCrFeMnNi high entropy alloy at intermediate temperatures

Kang, You Bin; Shim, Sang‐Chul; Lee, Kap Ho; Hong, Sun Ig

doi:10.1080/21663831.2018.1543731

Cited by 74 publications

(35 citation statements)

References 32 publications

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“…At 500 mN load, the creep displacement in the case of CoCrNi first increased from 298 K to 423 K and then decreased with further increase of temperature to 573 K. For CoCrFeMnNi, the creep displacement decreased with increasing temperature. This may be attributed to generation of partial dislocations at these intermediate temperatures and/or solute drag effects which restrict dislocation mobility [26][27][28]. Overall, CoCrNi showed the smallest creep displacement among the three systems for the load and temperature range investigated.…”

Section: Methodsmentioning

confidence: 93%

High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

Sadeghilaridjani

Mukherjee

2020

Metals

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Creep is a serious concern reducing the efficiency and service life of components in various structural applications. Multi-principal element alloys are attractive as a new generation of structural materials due to their desirable elevated temperature mechanical properties. Here, time-dependent plastic deformation behavior of two multi-principal element alloys, CoCrNi and CoCrFeMnNi, was investigated using nano-indentation technique over the temperature range of 298 K to 573 K under static and dynamic loads with applied load up to 1000 mN. The stress exponent was determined to be in the range of 15 to 135 indicating dislocation creep as the dominant mechanism. The activation volume was ~25b3 for both CoCrNi and CoCrFeMnNi alloys, which is in the range indicating dislocation glide. The stress exponent increased with increasing indentation depth due to higher density and entanglement of dislocations, and decreased with increasing temperature owing to thermally activated dislocations. The results for the two multi-principal element alloys were compared with pure Ni. CoCrNi showed the smallest creep displacement and the highest activation energy among the three systems studied indicating its superior creep resistance.

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Section: Methodsmentioning

confidence: 93%

High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

Sadeghilaridjani

Mukherjee

2020

Metals

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“…The Zr alloy cladding tube's in-reactor behaviors such as mechanical strength and creep and irradiation-induced growth are mainly controlled by its alloying elements and impurities including oxygen and heat treatment conditions applied in the tubing processing [20], [21]. In the future works, the effects of alloying elements and particles on the tubing processing and creep properties [17], [19], [22]- [25] will be investigated for the safe application of nuclear fuel cladding tubes processed with Zr alloy ingots cast with nuclear grade scraps.…”

Section: Resultsmentioning

confidence: 95%

Recycling Zr-Nb-Sn-Fe Scrap in Casting of Nuclear-Grade Alloy Ingots and Its Effects on Mechanical Performance and Integrity

Song¹,

Hong²

2020

IJESD

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Recycling of Zr-Nb-Sn-Fe scraps in casting enhances the price competitiveness of nuclear-grade Zr alloys and accordingly the energy from nuclear power plants. Increasing the fraction of scrap in casting of new alloy ingots increases the price competitiveness, but it aggravates the deformability and mechanical reliability of cast alloys. In this study, the effect of scrap ratio on the mechanical reliability of Zr-Nb-Sn-Fe alloys was studied. The increase of scrap fraction in casting increases the oxygen content in the ingot and nuclear claddings fabricated from cast ingots. The increase of oxygen content is caused by the surface oxide of scraps such as small pieces of turning, chips, etc. Iron content was not found to increase appreciably with the increasing fraction of scrap because scraps were well kept in the iron-free container. The microstructure of ss-cast Zr alloy with increasing fraction of scraps displayed plate/or needle α phase and the microstructural features were observed to be affected by increase of scrap fraction. The strength increases with increasing fraction of scrap, which can be attributed to the increase of oxygen content. The ductility decreased slightly with increase of scrap fraction. The strength increased at the expense of ductility with increase of scrap fraction. In some ingots, iron oxide flakes were intentionally added to explore the effects of iron oxide which may be added from the scarp storage container. The alloys with the addition of iron oxide flakes exhibited the drastic decrease of the formability and exhibited the brittle fracture behavior during rolling. The increase of oxide fraction increased the oxidation resistance because of high oxygen content the matrix may have prevented oxygen diffusion into matrix.

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“…Linear regression indicated creep activation energy of 352 ± 10 kJ/mol, 925 ± 100 kJ/mol, and 1000 ± 50 kJ/mol for W, Ta-Hf, and Ta-W, respectively. The calculated higher activation energy of 900-1000 kJ/mol for HEAs compared to pure W may be associated with severe lattice distortion and sluggish diffusion in HEAs resulting in a greater degree of dislocation interaction and supporting their higher creep resistance [48]. Activation energy for CoCrFeNiMn [12] and precipitation-hardened (FeCoNiCr)94Ti2Al4 [49] HEAs were reported to be ~300-400 kJ/mol and ~300-800 kJ/mol, respectively, from tensile tests.…”

Section: Discussionmentioning

confidence: 92%

High-Temperature Nano-Indentation Creep of Reduced Activity High Entropy Alloys Based on 4-5-6 Elemental Palette

Sadeghilaridjani

Muskeri

Pole

et al. 2020

Entropy

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There is a strong demand for materials with inherently high creep resistance in the harsh environment of next-generation nuclear reactors. High entropy alloys have drawn intense attention in this regard due to their excellent elevated temperature properties and irradiation resistance. Here, the time-dependent plastic deformation behavior of two refractory high entropy alloys was investigated, namely HfTaTiVZr and TaTiVWZr. These alloys are based on reduced activity metals from the 4-5-6 elemental palette that would allow easy post-service recycling after use in nuclear reactors. The creep behavior was investigated using nano-indentation over the temperature range of 298 K to 573 K under static and dynamic loads up to 5 N. Creep stress exponent for HfTaTiVZr and TaTiVWZr was found to be in the range of 20–140 and the activation volume was ~16–20b3, indicating dislocation dominated mechanism. The stress exponent increased with increasing indentation depth due to a higher density of dislocations and their entanglement at larger depth and the exponent decreased with increasing temperature due to thermally activated dislocations. Smaller creep displacement and higher activation energy for the two high entropy alloys indicate superior creep resistance compared to refractory pure metals like tungsten.

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Dislocation creep behavior of CoCrFeMnNi high entropy alloy at intermediate temperatures

Cited by 74 publications

References 32 publications

High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

Recycling Zr-Nb-Sn-Fe Scrap in Casting of Nuclear-Grade Alloy Ingots and Its Effects on Mechanical Performance and Integrity

High-Temperature Nano-Indentation Creep of Reduced Activity High Entropy Alloys Based on 4-5-6 Elemental Palette

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