The atomistic insights of chemical complexity effect on irradiation resistance of high entropy alloys

One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding this issue by modifying the composition of duodenary TiZrHfNbVCrMoMnFeCoNiAl (12x) alloy in which we recently reported the fabrication of hexagonal C14 Laves phase. We consider three alloys based on 12x: 7x=12x-VCrMoMnFe, 12x+Sc, 12x+Be and observe that all of them crystalize with the formation of C14 Laves phase as a dominant structure. We report that 12x+Be alloy reveals single-phase C14 structure with very high concentration of structural defects and ultra-fine dendritic microstructure with almost homogenous distribution of the constituted elements over the alloy matrix. The 7x and 12x+Sc alloys contain C14 as a main phase and unknown impurity phases. To characterize the materials, we examine their heat capacity, electrical conductivity and magnetic properties. The measurements reveal that the Laves phases are Curie-Weiss paramagnets, which demonstrate metallic conduction; 7x and 12x alloys also reveal a pronounced Kondo-like anomaly. Analysis of experimental data as well as ab initio calculations suggests that chemical complexity and compositional disorder cause strong s-d band scattering and thus the rather high density of d-states in the conduction band. Analysis of the results suggests that the mechanism of Laves phase formation in multicomponent multi-principal element metallic alloys is may be the same as in polydisperse hardspheres mixtures. Another important conclusion is that the configurational entropy is a negligible factor in the stabilization of multi-element Laves phases.

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Laves Phase Formation in High Entropy Alloys

Metals ◽

10.3390/met11121962 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1962

Author(s):

Roman Ryltsev ◽

Vasiliy Gaviko ◽

Svetlana Estemirova ◽

Evgenii Sterkhov ◽

Lubov Cherepanova ◽

...

Keyword(s):

Single Phase ◽

Chemical Elements ◽

Laves Phase ◽

Structural Defects ◽

Clear Understanding ◽

High Entropy Alloys ◽

High Concentration ◽

Laves Phases ◽

High Entropy ◽

Chemical Complexity

One of the intriguing recent results in the field of high-entropy alloys is the discovery of single-phase equiatomic multi-component Laves intermetallics. However, there is no clear understanding that a combination of chemical elements will form such high-entropy compounds. Here we contribute to understanding this issue by modifying the composition of duodenary TiZrHfNbVCrMoMnFeCoNiAl (12x) alloy in which we recently reported the fabrication of hexagonal C14 Laves phase. We consider three alloys based on 12x: 7x = 12x-VCrMoMnFe, 12x + Sc, 12x + Be and observe that all of them crystalize with the formation of C14 Laves phase as a dominant structure. We report that 12x + Be alloy reveals a single-phase C14 structure with a very high concentration of structural defects and ultra-fine dendritic microstructure with an almost homogenous distribution of the constituted elements over the alloy matrix. The analysis of electrical and magnetic properties reveals that the Laves phases are Curie-Weiss paramagnets, which demonstrate metallic conduction; 7x and 12x alloys also reveal a pronounced Kondo-like anomaly. Analysis of experimental data as well as ab initio calculations suggest that chemical complexity and compositional disorder cause strong s-d band scattering and thus the rather high density of d-states in the conduction band.

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High irradiation resistance of nanocrystalline W-based high entropy alloy

10.2172/1573323 ◽

2019 ◽

Cited By ~ 1

Author(s):

Osman El Atwani ◽

Enrique Martinez Saez ◽

Nan Li ◽

Jon Kevin Scott Baldwin ◽

Stuart Andrew Maloy ◽

...

Keyword(s):

High Entropy Alloy ◽

High Entropy ◽

High Irradiation ◽

Irradiation Resistance

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Fabrication and Characterization of Quinary High Entropy-Ultra-High Temperature Diborides

Ceramics ◽

10.3390/ceramics4020010 ◽

2021 ◽

Vol 4 (2) ◽

pp. 108-120

Author(s):

Simone Barbarossa ◽

Roberto Orrù ◽

Valeria Cannillo ◽

Antonio Iacomini ◽

Sebastiano Garroni ◽

...

Keyword(s):

High Temperature ◽

Single Phase ◽

Nominal Composition ◽

High Entropy ◽

Chemical Complexity ◽

Alternative Processing ◽

Plasma Sintering ◽

High Temperature Synthesis ◽

Spark Plasma

Due to their inherent chemical complexity and their refractory nature, the obtainment of highly dense and single-phase high entropy (HE) diborides represents a very hard target to achieve. In this framework, homogeneous (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, and (Hf0.2Zr0.2Nb0.2Mo0.2Ti0.2)B2 ceramics with high relative densities (97.4, 96.5, and 98.2%, respectively) were successfully produced by spark plasma sintering (SPS) using powders prepared by self-propagating high-temperature synthesis (SHS). Although the latter technique did not lead to the complete conversion of initial precursors into the prescribed HE phases, such a goal was fully reached after SPS (1950 °C/20 min/20 MPa). The three HE products showed similar and, in some cases, even better mechanical properties compared to ceramics with the same nominal composition attained using alternative processing methods. Superior Vickers hardness and elastic modulus values were found for the (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2 and the (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2 systems, i.e., 28.1 GPa/538.5 GPa and 28.08 GPa/498.1 GPa, respectively, in spite of the correspondingly higher residual porosities (1.2 and 2.2 vol.%, respectively). In contrast, the third ceramic, not containing tantalum, displayed lower values of these two properties (25.1 GPa/404.5 GPa). However, the corresponding fracture toughness (8.84 MPa m1/2) was relatively higher. This fact can be likely ascribed to the smaller residual porosity (0.3 vol.%) of the sintered material.

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A review on phase prediction in high entropy alloys

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211008935 ◽

2021 ◽

pp. 095440622110089

Author(s):

Vinay Kumar Soni ◽

S Sanyal ◽

K Raja Rao ◽

Sudip K Sinha

Keyword(s):

Solid Solution ◽

Phase Formation ◽

Single Phase ◽

High Entropy Alloy ◽

High Entropy Alloys ◽

Modeling Tools ◽

High Entropy ◽

Recent Developments ◽

Phase Prediction ◽

The Stability

The formation of single phase solid solution in High Entropy Alloys (HEAs) is essential for the properties of the alloys therefore, numerous approach were proposed by many researchers to predict the stability of single phase solid solution in High Entropy Alloy. The present review examines some of the recent developments while using computational intelligence techniques such as parametric approach, CALPHAD, Machine Learning etc. for prediction of various phase formation in multicomponent high entropy alloys. A detail study of this data-driven approaches pertaining to the understanding of structural and phase formation behaviour of a new class of compositionally complex alloys is done in the present investigation. The advantages and drawbacks of the various computational are also discussed. Finally, this review aims at understanding several computational modeling tools complying the thermodynamic criteria for phase formation of novel HEAs which could possibly deliver superior mechanical properties keeping an aim at advanced engineering applications.

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Al, Cu and Zr Addition to High Entropy Alloys: The Effect on Recrystallization Temperature

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.1137 ◽

2018 ◽

Vol 941 ◽

pp. 1137-1142

Author(s):

Elena Colombini ◽

Andrea Garzoni ◽

Roberto Giovanardi ◽

Paolo Veronesi ◽

Angelo Casagrande

Keyword(s):

Solid Solution ◽

Grain Size ◽

Single Phase ◽

Boundary Energy ◽

Cold Deformation ◽

Recrystallization Temperature ◽

High Entropy Alloys ◽

High Entropy ◽

Ni Alloy ◽

Sluggish Diffusion

The equimolar Cr, Mn, Fe, Co and Ni alloy, first produced in 2004, was unexpectedly found to be single-phase. Consequently, a new concept of materials was developed: high entropy alloys (HEA) forming a single solid-solution with a near equiatomic composition of the constituting elements. In this study, an equimolar CoCrFeMnNi HEA was modified by the addition of 5 at% of either Al, Cu or Zr. The cold-rolled alloys were annealed for 30 minutes at high temperature to investigate the recrystallization kinetics. The evolution of the grain boundary and the grain size were investigated, from the as-cast to the recrystallized state. Results show that the recrystallized single phase FCC structures exhibits different twin grains density, grain size and recrystallization temperatures as a function of the at.% of modifier alloying elements added. In comparison to the equimolar CoCrFeMnNi, the addition of modifier elements increases significantly the recrystallization temperature after cold deformation. The sluggish diffusion (typical of HEA alloys), the presence of a solute in solid solution as well as the low twin boundary energy are responsible for the lower driving force for recrystallization.

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Accelerated discovery of single-phase refractory high entropy alloys assisted by machine learning

Computational Materials Science ◽

10.1016/j.commatsci.2021.110723 ◽

2021 ◽

Vol 199 ◽

pp. 110723

Author(s):

Yonggang Yan ◽

Dan Lu ◽

Kun Wang

Keyword(s):

Machine Learning ◽

Single Phase ◽

High Entropy Alloys ◽

High Entropy

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Study on properties of single-phase high entropy alloys with FCC structure based on the empirical electron theory

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2021.162892 ◽

2021 ◽

pp. 162892

Author(s):

Xinpeng Guo ◽

Yongquan Guo ◽

Linhan Yin

Keyword(s):

Single Phase ◽

High Entropy Alloys ◽

Electron Theory ◽

High Entropy ◽

Empirical Electron Theory ◽

Fcc Structure

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Shear localization of fcc high-entropy alloys

EPJ Web of Conferences ◽

10.1051/epjconf/201818303028 ◽

2018 ◽

Vol 183 ◽

pp. 03028 ◽

Cited By ~ 1

Author(s):

Marc A. Meyers ◽

Zezhou Li ◽

Shiteng Zhao ◽

Bingfeng Wang ◽

Yong Liu ◽

...

Keyword(s):

Shear Strain ◽

Single Phase ◽

Dynamic Compression ◽

Impact Resistance ◽

Shear Localization ◽

Solid Solution Hardening ◽

High Entropy Alloys ◽

High Entropy ◽

Work Hardening Rate ◽

High Work

Dynamic behavior of the single phase (fcc) Al0.3CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs) was examined. The combination of multiple strengthening mechanisms such as solid solution hardening, cutting forest dislocation, as well as mechanical nano-twinning leads to a high work-hardening rate, compared with conventional alloys. The resistance to shear localization was studied by dynamicallyloading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed for Al0.3CoCrFeNi HEA at a large shear strain ~1.1. Additionally, shear localization of the CoCrFeMnNi HEA was only found at an even larger shear strain ~7 under dynamic compression. It is therefore proposed that the combination of the excellent strain-hardening ability and modest thermal softening of these two kinds of high-entropy alloys gives rise to remarkable resistance to shear localization, which makes HEAs excellent candidates for impact resistance applications.

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