scholarly journals High-Pressure Induced Phase Transitions in High-Entropy Alloys: A Review

Entropy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 239 ◽  
Author(s):  
Fei Zhang ◽  
Hongbo Lou ◽  
Benyuan Cheng ◽  
Zhidan Zeng ◽  
Qiaoshi Zeng
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Future Research ◽  
High Entropy Alloys ◽  
High Entropy ◽  
New Class ◽  
Materials Research ◽  
The Stability ◽  
Irreversible Phase Transitions

High-entropy alloys (HEAs) as a new class of alloy have been at the cutting edge of advanced metallic materials research in the last decade. With unique chemical and topological structures at the atomic level, HEAs own a combination of extraordinary properties and show potential in widespread applications. However, their phase stability/transition, which is of great scientific and technical importance for materials, has been mainly explored by varying temperature. Recently, pressure as another fundamental and powerful parameter has been introduced to the experimental study of HEAs. Many interesting reversible/irreversible phase transitions that were not expected or otherwise invisible before have been observed by applying high pressure. These recent findings bring new insight into the stability of HEAs, deepens our understanding of HEAs, and open up new avenues towards developing new HEAs. In this paper, we review recent results in various HEAs obtained using in situ static high-pressure synchrotron radiation x-ray techniques and provide some perspectives for future research.

scholarly journals HIGH-ENTROPY ALLOYS AS A PROSPECTIVE CLASS OF NEW RADIATION-TOLERANT MATERIALS RESEARCH DEVELOPMENT ANALYSIS BASED ON THE INFORMATION DATABASES

2021 ◽  
pp. 3-15
Author(s):  
A.V. Levenets ◽  
M.A. Tikhonovsky ◽  
V.N. Voyevodin ◽  
A.G. Shepelev ◽  
O.V. Nemashkalo
Keyword(s):  
Radiation Damage ◽  
Exponential Growth ◽  
High Entropy Alloys ◽  
Research Development ◽  
Metallic Materials ◽  
High Entropy ◽  
New Class ◽  
Materials Research ◽  
Development Analysis ◽  
Radiation Tolerant

A new class of metallic materials, so-called “high-entropy alloys” (HEAs), was under review. Various definitions of these alloys are given, their main differences from the conventional alloys are indicated and the dynamics of publications in the period from the first publications in 2004 to the end of 2020 are presented. It is noted the almost exponential growth of the article numbers concerning these alloys, and the main reasons of such high interest are discussed. Experimental results of development the radiation-tolerant materials based on the concept of high-entropy alloys and study of the radiation damage mechanisms are summarised.

scholarly journals Unconventional Deformation Behaviours of Nanoscaled High-Entropy Alloys

Entropy ◽  
2018 ◽  
Vol 20 (10) ◽  
pp. 778 ◽  
Author(s):  
Yeqiang Bu ◽  
Shenyou Peng ◽  
Shiwei Wu ◽  
Yujie Wei ◽  
Gang Wang ◽  
...  
Keyword(s):  
Phase Transformations ◽  
First Principles ◽  
Atomic Scale ◽  
High Entropy Alloys ◽  
First Principles Calculations ◽  
High Entropy ◽  
Fcc Metals ◽  
The Stability ◽  
Similar Deformation

The bulk high-entropy alloys (HEAs) exhibit similar deformation behaviours as traditional metals. These bulk behaviours are likely an averaging of the behaviours exhibited at the nanoscale. Herein, in situ atomic-scale observation of deformation behaviours in nanoscaled CoCrCuFeNi face-centred cubic (FCC) HEA was performed. The deformation behaviours of this nanoscaled FCC HEA (i.e., nanodisturbances and phase transformations) were distinct from those of nanoscaled traditional FCC metals and corresponding bulk HEA. First-principles calculations revealed an obvious fluctuation of the stacking fault energy and stability difference at the atomic scale in the HEA. The stability difference was highlighted only in the nanoscaled HEA and induced unconventional deformation behaviours. Our work suggests that the nanoscaled HEA may provide more chances to discover the long-expected essential distinction between the HEAs and traditional metals.

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.

scholarly journals Phase Transitions in Borohydride Perovskites

2014 ◽  
Vol 70 (a1) ◽  
pp. C73-C73
Author(s):  
Pascal Schouwink ◽  
Radovan Cerny
Keyword(s):  
Phase Transitions ◽  
Volume Expansion ◽  
Host Lattice ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
New Class ◽  
Structural Distortions ◽  
Complex Hydrides ◽  
Type Lattice

A series of complex hydrides based on the highly dynamic tetrahydroborate anion BH4-and crystallizing in theABX3type lattice has recently been discovered. They present a rare case of a family of iono-covalent hydrides that has a genuine tunable host lattice, making them an interesting new class of host compounds for not only the design of hydrogen storage materials but also hydride-properties related to heavy metals. Amongst these, preliminary results onREE-based luminescence will be discussed in the neat and doped compounds, the Ln2+excited states surprisingly not being subject to significant quenching by B-H vibrations. Unlike oxide- or halide-perovskites some members of theAB(BH4)3group do not evolve to higher symmetries as a function of temperature. We show by means ofin-situsynchrotron X-ray powder diffraction, vibrational spectroscopy andab initiocalculations in the solid state, that temperature-induced structural distortions in perovskite-typeACa(BH4)3(A= K, Rb, Cs) have their origin in close hydridic di-hydrogen contacts of repulsive nature. Coupling between internal B-H vibrations and phonons results in lattice distortions that are identical in symmetry to well-known instabilities (soft modes) in perovskites, which generally condense to lower temperatures. Anion-substitution BH4-<->X-(X= Halide) calculated on ordered models can relax distortions caused by repulsive effects. High temperature phase-transitions inACa(BH4)3can be of first or second-order, including 2-fold superlattices, simple cubic-cubic transitions accompanied by volume expansion or complex modulated superstructures accompanied by negative volume expansion, as is the case in RbCa(BH4)3. Close di-hydrogen contacts may be suggested as a tool to tailor the crystal symmetry in complex hydride perovskites in the future.

scholarly journals Pressure-and temperature induced phase transitions, piezochromism, NLC behaviour and pressure controlled Jahn–Teller switching in a Cu-based framework

2020 ◽  
Vol 11 (33) ◽  
pp. 8793-8799
Author(s):  
Charles J. McMonagle ◽  
Priyanka Comar ◽  
Gary S. Nichol ◽  
David R. Allan ◽  
Jesús González ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Single Crystal ◽  
Spectroscopic Techniques ◽  
Single Crystal Diffraction ◽  
Jahn Teller ◽  
Pressure Controlled

In situ high-pressure single-crystal diffraction and spectroscopic techniques have been used to study a previously unreported Cu-framework bis[1-(4-pyridyl)butane-1,3-dione]copper(ii) (CuPyr-I).

scholarly journals Phase Stability and Vibrational Properties of Iron-Bearing Carbonates at High Pressure

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1142
Author(s):  
Chaoshuai Zhao ◽  
Liangxu Xu ◽  
Weibin Gui ◽  
Jin Liu
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Spin Transition ◽  
Laser Raman ◽  
Electronic Spin ◽  
Pressure Medium ◽  
Raman Modes ◽  
Sample Chamber ◽  
The Stability ◽  
Iron Bearing

The spin transition of iron can greatly affect the stability and various physical properties of iron-bearing carbonates at high pressure. Here, we reported laser Raman measurements on iron-bearing dolomite and siderite at high pressure and room temperature. Raman modes of siderite FeCO3 were investigated up to 75 GPa in the helium (He) pressure medium and up to 82 GPa in the NaCl pressure medium, respectively. We found that the electronic spin-paring transition of iron in siderite occurred sharply at 42–44 GPa, consistent with that in the neon (Ne) pressure medium in our previous study. This indicated that the improved hydrostaticity from Ne to He had minimal effects on the spin transition pressure. Remarkably, the spin crossover of siderite was broadened to 38–48 GPa in the NaCl pressure medium, due to the large deviatoric stress in the sample chamber. In addition, Raman modes of iron-bearing dolomite Ca1.02Mg0.76Fe0.20Mn0.02(CO3)2 were explored up to 58 GPa by using argon as a pressure medium. The sample underwent phase transitions from dolomite-Ⅰ to -Ⅰb phase at ~8 GPa, and then to -Ⅱ at ~15 and -Ⅲb phase at 36 GPa, while no spin transition was observed in iron-bearing dolomite up to 58 GPa. The incorporation of FeCO3 by 20 mol% appeared to marginally decrease the onset pressures of the three phase transitions aforementioned for pure dolomite. At 55–58 GPa, the ν1 mode shifted to a lower frequency at ~1186 cm−1, which was likely associated with the 3 + 1 coordination in dolomite-Ⅲb. These results shed new insights into the nature of iron-bearing carbonates at high pressure.

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