scholarly journals Laves Phase Formation in High Entropy Alloys

2021 ◽  
Author(s):  
Roman Ryltsev ◽  
Svetlana Estemirova ◽  
Evgenii Sterkhov ◽  
Lubov Cherepanova ◽  
Denis Yagodin ◽  
...  
Keyword(s):  
Phase Formation ◽  
Single Phase ◽  
Laves Phase ◽  
Structural Defects ◽  
Clear Understanding ◽  
High Entropy Alloys ◽  
Laves Phases ◽  
Important Conclusion ◽  
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 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.

scholarly journals Laves Phase Formation in High Entropy Alloys

Metals ◽  
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.

A review on phase prediction in high entropy alloys

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.

Laves-phase formation criterion for high-entropy alloys

2016 ◽  
Vol 33 (1) ◽  
pp. 17-22 ◽  
Author(s):  
N. Yurchenko ◽  
N. Stepanov ◽  
G. Salishchev
Keyword(s):  
Phase Formation ◽  
Laves Phase ◽  
High Entropy Alloys ◽  
High Entropy

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

2022 ◽  
Author(s):  
Lingyun Qian ◽  
Honggang Bao ◽  
Rui Li ◽  
Qing Peng
Keyword(s):  
Nuclear Structure ◽  
Single Phase ◽  
High Entropy Alloys ◽  
Next Generation ◽  
High Entropy ◽  
Chemical Complexity ◽  
High Irradiation ◽  
Irradiation Resistance

High irradiation tolerance is a key feature required for designing the nuclear structure materials for the next generation reactors, where high entropy alloys and equiatomic multicomponent single-phase alloys are good...

scholarly journals Kinetically Limited Phase Formation of Pt-Ir Based Compositionally Complex Thin Films

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2298
Author(s):  
Aparna Saksena ◽  
Dimitri Bogdanovski ◽  
Hrushikesh Sahasrabuddhe ◽  
Denis Music ◽  
Jochen M. Schneider
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Surface Diffusion ◽  
Phase Formation ◽  
Single Phase ◽  
Configurational Entropy ◽  
High Entropy Alloys ◽  
X Ray ◽  
High Entropy ◽  
Two Phases

The phase formation of PtIrCuAuX (X = Ag, Pd) compositionally complex thin films is investigated to critically appraise the criteria employed to predict the formation of high entropy alloys. The formation of a single-phase high entropy alloy is predicted if the following requirements are fulfilled: 12 J∙K−1 mol−1 ≤ configurational entropy ≤ 17.5 J∙K−1 mol−1, −10 kJ∙mol−1 ≤ enthalpy of mixing ≤ 5 kJ∙mol−1 and atomic size difference ≤ 5%. Equiatomic PtIrCuAuX (X = Ag, Pd) fulfill all of these requirements. Based on X-ray diffraction and energy-dispersive X-ray spectroscopy data, near-equiatomic Pt22Ir23Cu18Au18Pd19 thin films form a single-phase solid solution while near-equiatomic Pt22Ir23Cu20Au17Ag18 thin films exhibit the formation of two phases. The latter observation is clearly in conflict with the design rules for high entropy alloys. However, the observed phase formation can be rationalized by considering bond strengths and differences in activation energy barriers for surface diffusion. Integrated crystal orbital Hamilton population values per bond imply a decrease in bond strength for all the interactions when Pd is substituted by Ag in PtIrCuAuX which lowers the surface diffusion activation energy barrier by 35% on average for each constituent. This enables the surface diffusion-mediated formation of two phases, one rich in Au and Ag and a second phase enriched in Pt and Cu. Hence, phase formation in these systems appears to be governed by the complex interplay between energetics and kinetic limitations rather than by configurational entropy.

Microstructural Characteristics and Mechanical Behaviors of AlCoCrFeNi High-Entropy Alloys at Ambient and Cryogenic Temperatures

2011 ◽  
Vol 688 ◽  
pp. 419-425 ◽  
Author(s):  
Jun Wei Qiao ◽  
S.G. Ma ◽  
E.W. Huang ◽  
C.P. Chuang ◽  
P.K. Liaw ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Ambient Temperature ◽  
Phase Formation ◽  
Single Phase ◽  
Size Difference ◽  
High Entropy Alloys ◽  
Cryogenic Temperatures ◽  
Mechanical Behaviors ◽  
Microstructural Characteristics ◽  
High Entropy

The phase-formation rule of high-entropy alloys (HEAs) with different microstructures is discussed, based on the atom-size difference in multicomponent alloys. For the single-phase HEA with the composition of AlCoCrFeNi, the yielding strengths and fracture strengths at cryogenic temperatures increase distinguishingly, compared to the corresponding mechanical properties at ambient temperature. However, the plasticity at 298 and 77 K changes very gently, while the fracture modes are intergranular and transgranular, respectively.

Criteria for laves-phase formation in refractory high-entropy alloys

2021 ◽  
pp. 1-17
Author(s):  
Hongwei Yao ◽  
Dongxu Qiao ◽  
Junwei Miao ◽  
Jun Wang ◽  
Enyu Guo ◽  
...  
Keyword(s):  
Phase Formation ◽  
Laves Phase ◽  
High Entropy Alloys ◽  
High Entropy

Effect of Ta Addition on Microstructure and Hardness of FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax High-Entropy Alloys

2016 ◽  
Vol 846 ◽  
pp. 13-19 ◽  
Author(s):  
Siti Sarah Mohd Pauzi ◽  
Mohamad Kamal Harun ◽  
Mahesh Talari
Keyword(s):  
Phase Formation ◽  
Intermetallic Phase ◽  
Laves Phase ◽  
Molar Ratio ◽  
High Entropy Alloys ◽  
Strengthening Effect ◽  
High Entropy ◽  
Arc Melting ◽  
Melting Technique ◽  
A Minor

Phase formation, microstructure, and hardness properties of FeCrNiMnCoTax and Al0.5 FeCrNiMnCoTax high-entropy alloys (HEA) have been investigated and reported. In this study, FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax high-entropy alloys (HEA) were synthesized using arc-melting technique in argon (Ar) atmosphere from high purity elements (x in molar ratio, x=0.2, x=0.4 and x=0.6). Ingots from arc-melting were homogenized for 24h at 900°C in Ar atmosphere. Dominant dendritic and inter-dendritic phases were identified from the electron micrographs of these HEA. The area of inter-dendrite region increased for both FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys with the increasing of Ta content. The major phases in both FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys were identified as FCC and BCC solid-solutions. Addition of Al in Al0.5FeCrNiMnCoTax alloys has resulted in precipitation of a minor phase which was identified as FCC-TaCr2 Laves phase. As the Ta content increased, hardness of FeCrNiMnCoTax and Al0.5FeCrNiMnCoTax alloys increased from 200.34 Hv to 345.10 Hv and 385.22 Hv to 570.86 Hv respectively. Furthermore, presence of Laves phase in Al0.5FeCrNiMnCoTax alloys has resulted in higher hardness values compared to Al free sample, and this higher hardness could be attributed to precipitation strengthening effect by Laves intermetallic phase formation.

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

Ceramics ◽  
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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