Cryogenic strength improvement by utilizing room-temperature deformation twinning in a partially recrystallized VCrMnFeCoNi high-entropy alloy

The main disadvantage of fcc (face-centred cubic lattice) high-entropy alloys is the low stress level at the yield point (σ0.1) at a test temperature above room temperature. This restricts their practical application at high test temperatures from 773 K to 973 K. In this study, we found that a high stress level was reached at the yield point σ0.1 ≈ G/100–G/160 (G is the shear modulus) of the [001]- and [1¯44]-oriented crystals of the Co23.36Cr23.29Fe23.80Ni21.88Al7.67 (Al0.3CoCrFeNi) high-entropy alloy (HEA) within a wide temperature range of 77–973 K under tension, due to the occurrence, of nanotwins, multipoles, dislocations under plastic deformation at 77 K and the subsequent precipitation of ordered L12 and B2 particles. It was shown that grain boundaries are not formed and the samples remain in a single-crystal state after low-temperature deformation and subsequent ageing at 893 K for 50 h. Achieving a high-strength state in the Al0.3CoCrFeNi HEA single crystals induces the orientation dependence of the critical resolved shear stresses (τcr) at T ≥ 200 K (τcr[1¯44] > τcr[001]), which is absent in the initial single-phase crystals, weakens the temperature dependence of σ0.1 above 573 K, and reduces plasticity to 5–13% in the [1¯44] orientation and 15–20% in the [001] orientation.

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Laser Beam Welding of a Low Density Refractory High Entropy Alloy

Metals ◽

10.3390/met9121351 ◽

2019 ◽

Vol 9 (12) ◽

pp. 1351 ◽

Cited By ~ 2

Author(s):

Evgeniya Panina ◽

Nikita Yurchenko ◽

Sergey Zherebtsov ◽

Nikita Stepanov ◽

Gennady Salishchev ◽

...

Keyword(s):

Laser Beam ◽

Room Temperature ◽

Elevated Temperatures ◽

Laser Beam Welding ◽

Base Material ◽

Laves Phase ◽

High Entropy Alloy ◽

High Entropy ◽

Grains Refinement ◽

Cast Condition

The effect of laser beam welding on the structure and properties of a Ti1.89NbCrV0.56 refractory high entropy alloy was studied. In particular, the effect of different pre-heating temperatures was examined. Due to the low ductility of the material, laser beam welding at room temperature resulted in the formations of hot cracks. Sound butt joints without cracks were produced using pre-heating to T ≥ 600 °C. In the initial as-cast condition, the alloy consisted of coarse bcc grains with a small amount of lens-shaped C15 Laves phase particles. A columnar microstructure was formed in the welds; the thickness of the grains increased with the temperature of pre-heating before welding. The Laves phase particles were formed in the seams after welding at 600 °C or 800 °C, however, these particles were not observed after welding at room temperature or at 400 °C. Soaking at elevated temperatures did not change the microstructure of the base material considerably, however, “additional” small Laves particles formed at 600 °C or 800 °C. Tensile test of welded specimens performed at 750 °C resulted in the fracture of the base material because of the higher hardness of the welds. The latter can be associated with the bcc grains refinement in the seams.

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Monocrystalline elastic constants of fcc-CrMnFeCoNi high entropy alloy

MRS Advances ◽

10.1557/adv.2017.76 ◽

2017 ◽

Vol 2 (27) ◽

pp. 1429-1434 ◽

Cited By ~ 7

Author(s):

Katsushi Tanaka ◽

Takeshi Teramoto ◽

Ryo Ito

Keyword(s):

Solid Solution ◽

Elastic Constants ◽

Room Temperature ◽

Entropy Change ◽

High Entropy Alloy ◽

Melting Points ◽

High Entropy ◽

Fcc Metals ◽

Cauchy Pressure ◽

Fcc Structure

ABSTRACTMono-crystalline elastic constants of equiatomic quinary Cr-Mn-Fe-Co-Ni high entropy alloy with the fcc structure have experimentally been determined by a resonance ultrasound spectroscopy at room temperature. The values of the bulk modulus of the high entropy alloy experimentally determined are similar to other conventional fcc metals when the values are normalized by the melting points. This indicates that the entropy change at melting is similar to that of conventional metals. The values of Pough’s index and the Cauchy pressure are determined as 1.79 and -11.6 GPa, respectively. When the ductility of the alloy is judged from the indices, the ductility of the high entropy alloy is limited. In order to explain the negative Cauchy pressure of the high entropy alloy, it is required to assume that relatively strong directional interatomic bondings like intermetallic compounds exist in the alloy though the crystal is disordered solid solution.

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Alloying behavior and deformation twinning in a CoNiFeCrAl0.6Ti0.4 high entropy alloy processed by spark plasma sintering

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2012.11.146 ◽

2013 ◽

Vol 553 ◽

pp. 316-323 ◽

Cited By ~ 79

Author(s):

Zhiqiang Fu ◽

Weiping Chen ◽

Sicong Fang ◽

Dayue Zhang ◽

Huaqiang Xiao ◽

...

Keyword(s):

Spark Plasma Sintering ◽

Deformation Twinning ◽

High Entropy Alloy ◽

High Entropy ◽

Plasma Sintering ◽

Spark Plasma

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In-situ neutron diffraction studies on high-temperature deformation behavior in a CoCrFeMnNi high entropy alloy

Intermetallics ◽

10.1016/j.intermet.2015.02.020 ◽

2015 ◽

Vol 62 ◽

pp. 1-6 ◽

Cited By ~ 42

Author(s):

Wanchuck Woo ◽

E-Wen Huang ◽

Jien-Wei Yeh ◽

Hahn Choo ◽

Chi Lee ◽

...

Keyword(s):

High Temperature ◽

Neutron Diffraction ◽

Deformation Behavior ◽

High Temperature Deformation ◽

Temperature Deformation ◽

High Entropy Alloy ◽

High Entropy ◽

In Situ Neutron Diffraction

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Elastic, Mechanical and Thermophysical properties of Single-Phase Quaternary ScTiZrHf High-Entropy Alloy

Фізика і хімія твердого тіла ◽

10.15330/pcss.22.4.687-696 ◽

2021 ◽

Vol 22 (4) ◽

pp. 687-696

Author(s):

Sachin Rai ◽

Navin Chaurasiya ◽

Pramod K. Yadawa

Keyword(s):

Mechanical Properties ◽

Elastic Constants ◽

Room Temperature ◽

Single Phase ◽

Mechanical Characterization ◽

Ultrasonic Attenuation ◽

High Entropy Alloy ◽

High Entropy ◽

Different Temperatures ◽

Ultrasonic Parameters

Consequent to the interaction potential model, the high-order elastic constants at high entropy alloys in single-phase quaternary ScTiZrHf have been calculated at different temperatures. Elastic constants of second order (SOECs) helps to determine other ultrasonic parameters. With the help of SOECs other elastic moduli, bulk modulus, shear modulus, Young’s modulus, Pugh’s ratio, elastic stiffness constants and Poisson’s ratio are estimated at room temperature for elastic and mechanical characterization. The other ultrasonic parameters are calculated at room temperature for elastic and mechanical characterization. The temperature variation of ultrasonic velocities along the crystal's z-axis is evaluated using SOECs. The temperature variation of the average debye velocity and the thermal relaxation time (τ) are also estimated along this orientation axis. The ultrasonic properties correlated with elastic, thermal and mechanical properties which is temperature dependent is also discussed. The ultrasonic attenuation due to phonon – phonon (p-p) interactions is also calculated at different temperatures. In the study of ultrasonic attenuation such as a function of temperature, thermal conductivity appears to be main contributor and p- p interactions are the responsible reason of attenuation and found that the mechanical properties of the high entropy alloy ScTiZrHf are superior at room temperature.

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