Ministry of Education, Culture, Sports, Science and Technology Grant-in-Aid“Scientific Research on Innovative Areas” for FY2018-22
NEWSLETTERHigh Entropy Alloys
Science of New Class of Materials Based on
Elemental Multiplicity and Heterogeneity

Vol.

3

2021 MAY

Notable Achievements

The Latest Research Results Elucidated in the HEA Project!

A01(b)

Discovery of High-Entropy Alloy Nanoparticles and Explorationof Their Properties

Hiroshi Kitagawa (Kyoto University)

Solid-solution alloys are favorable to tune their properties because the constituent elements of a solid solution are randomly and homogeneously distributed in solids. However, the majority of the bulk alloys are phase-separated under ambient conditions, where the constituent
elements are immiscible with each other. To overcome the challenge of the bulk-phase metallurgical aspects, we have focused on the nanosize effect. Metal nanoparticles (NPs) are known to show different chemical and physical properties from bulk metals because of their highsurface-to-volume ratios and the quantum size effect. We have developed a continuous solvothermal flow reactor to synthesize novel
solid-solution alloy NPs and high-entropy alloy NPs consisting of immiscible constituents in bulk state (Fig. 1)[1]. In addition to the configurational entropy, it is expected that surface and vibrational entropies would have more impact on the thermodynamics of metal NPs rather thanbulk metals due to the nanosized effect.
We have also succeeded in developing PdRuIr ternary alloy NPs which exhibit highly stable and active three-way catalytic (TWC) property(Fig. 2)[2]. The binary PdRu shows higher TWC activity than the most expensive but essential Rh which is known as the best NOx reduction
catalyst. However, their activity significantly deteriorates due to the phase separation during the reaction since Pd and Ru are immiscible inbulk. We performed DFT calculations to elucidate the origin of the stabilization effect in PdRuIr ternary catalyst and found that the solid-solution phase in PdRuIr NPs was extremely stabilized by the combination of enthalpy of mixing and the large configurational entropy by alloying
the third element.
Besides, we had succeeded in synthesizing platinum-group metal HEA (PGM-HEA) NPs in the last year. This year we found that all the
6-elements PGM-HEA (RuRhPdOsIrPt) NPs show a record-high ethanol oxidation electrocatalytic activity with a 12-electron process.[3] We
expect that the HEA NPs would be promising catalysts for complex reactions because HEA NPs intrinsically possess various active sites andFig. 1: Schmatic of the continuous solvothermal flow reactor (a) HAADF-STEM image and (b-f) EDS maps of RuRhPdIrPt HEA NP synthesized by acontinuous flow reactor ((b) Pd-L, (c) Ru-L, (d) Ir-L, (e) Pt-L, and (f) Rh-L)

High Entropy Alloys Notable Achievements

2021 MAY

high stability. Furthermore, 5-elements PGM-HEA (RuRhPd
IrPt) NPs exhibited a very high hydrogen evolution reaction(HER) electrocatalytic activity in both acid and alkaline
solutions.[4] Although the HER activity is often discussed byd-band center theory, this HEA catalyst did not follow thetendency of d-band center theory and marked very highactivity. Therefore, this result implies that HEA catalysts
need a new descriptor to predict their activity. We are further
investigating this mechanism.
[1] K. Kusada, et al., “Nonequilibrium Flow-Synthesis of Solid-Solution
Alloy Nanoparticles: From Immiscible Binary to High-Entropy Alloys”,
Journal of Physical Chemistry C, 125, 458-463 (2021).
[2] K. Kusada, et al., “Highly Stable and Active Solid-Solution-Alloy
Three-Way Catalyst by Utilizing Configurational-Entropy Effect”,
Advanced Materials, 33, 2005206 (2021).
[3] D. Wu, et al., “Platinum-Group-Metal High-Entropy-Alloy Nanoparticles”, Journal of the Americal Chemical Society, 142, 13833-13838(2020).
[4] D. Wu, et al., “On the Electronic Structure and Hydrogen Evolution
Reaction Activity of Platinum Group Metal-Based High-Entropy-Alloy
Nanoparticles”, Chemical Science, 11, 12731 - 12736 (2020).

A01(a)

Fig. 2: The endurance test of the PdRuIr catalyst for the TWC reaction. a, b) The
cycle dependence of NOx conversion on PdRu (Pd:Ru = 1:1) (a) and PdRuIr(Pd:Ru:Ir = 1:1:1) (b) catalysts, and c) the temperatures corresponding to 50%
conversion (T50) of NOx of (a) and (b). d) HAADF-STEM image and elemental
maps of the PdRuIr catalyst after 20 cycles of the TWC test.

Persistent slip in TiZrNbHfTa observed by using an atomic force
microscope

Masaki Tanaka (Kyushu University), Shigeto Yamasaki (Kyushu University), Tatsuya Morikawa (Kyushu University)

inin

There are several reports which shows that slip bands in bcc high-entropy alloys are straight and sharp. This phenomenon suggests thatcross-slip is restricted in bcc high-entropy alloys. In this study, slip property of TiZrNbHfTa, which has bcc structure, was evaluated by obtaining ψ–χ relationships with bending tests of micro cantilevers, where χ is defined as the angle between the maximum shear stress plane and––(1 01) and ψ is defined as the angle between the apparent slip plane and (1 01). The ψ–χ relationship indicated that ψ is nearly the same asχ, suggesting that there is no persistent slip. Detailed observations with an atomic force microscope confirm as shown in right figure thatcross-slipping is so frequent at a sub-micrometer
length-scale that the slip bands appear to be straight andthe maximum shear stress plane is observed on a micrometer length-scale. Here, TiZrNbHfTa shows abnormallyfrequent cross-slipping, which is a novel characteristic ofhigh-entropy body-centered cubic alloys. Although further
investigations are necessary to elucidate the reason why
TiZrNbHfTa shows such frequent cross-slipping, one
possibility is the random atomic arrangement of high-entropy alloys.
a

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ca

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nd hba ntg
ip e
sl l
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av icrW bm
su.

0.2 µm

le

.

le

5 µm

s sca
nd hba tg
ip en
sl r l
ht te
ig e
ra om
St ocrm[1] M. Tanaka, S. Okajo, S. Yamasaki, T. Morikawa, “Persistent slip
observed in TiZrNbHfTa: A body-centered high-entropy cubic alloy”,
Scripta Materialia, 200, (2021),113895.

High Entropy Alloys Notable Achievements

A01(a)

2021 MAY

Electrical Resistivity and Local Structures of High Entropy Alloys

Hisanori Tanimoto (University of Tsukuba), Ryo Hozumi (University of Tsukuba), Mari Kawamura (University of Tsukuba)

Metallic solid solutions composed of five or more elements in equimolar ratios are called high-entropy alloys (HEAs). HEAs are crystalline
but the chemical atomic arrangement is disordered in principle and thelattice is locally strained. It was reported that locally-ordered atomic
clusters are existed in chemically and topologically disordered amorphous alloys. The retarded atomic diffusion in HEAs suggests theformation of chemical short-range-orders (SROs) or local units. The
electrical resistivity is a macroscopic property but quite sensitive forchanges in atomic configurations. The local structures and their stabilities in CrMnFeCoNi HEA have been surveyed from the electricalresistivity measurement. By isothermal annealing below 1073K, theresistivity of CrMnFeCoNi HEA showed a gradual increase from theinitial value after the solid solution treatment. The increased resistivity
by annealing showed a slight decrease by passing electric pulse
current (electropulsing). It was reported that the resistivity of CrMnFeCoNi HEA decreased by cold working. The resistivity of conventionalalloys shows increases due to lattice defects and precipitates and theincreased resistivity shows the recovery by annealing. The changes in
the resistivity observed for HEAs indicate that SROs or the local units
are formed by annealing and some of them are dissolved to the original
random state by electroplusing or deformation.

A01(b)

Electrochemical Passivation for Improving Pitting Corrosion Resistanceof Equiatomic CoCrFeMnNi High-Entropy Alloy

Li Pao (Tohoku University), Izumi Muto (Tohoku University), Yu Sugawara (Tohoku University)

The pitting corrosion behavior of arc-melted equimolar CoCrFeMnNi
alloy was investigated by macro-scale and micro-scale potentiodynamic polarization. It was found that Cr-Mn-O inclusions with S-containing
parts were the pit initiation sites for pitting in chloride solutions at
near-neutral pH. During polarization, in situ observations on the alloy
surface were performed, and the selective dissolution of the S-containing parts was found to occur under open-circuit and anodic potentials.
It was concluded that the S-containing parts of the inclusions were thefirst to dissolved, followed by the initiation of pitting. The S-containing
parts of the inclusions were removed by potentiostatic polarization andimmersion in H2SO4, but the pitting corrosion resistance after thesetreatments did not improve apparently. In contrast, by potentiodynamic
polarization in H2SO4, the S-containing parts of the inclusions were
removed and the passive film on the alloy-matrix became Cr enriched,resulting in significant improvement in the pitting corrosion resistance.
As a result, the pitting potential in 0.1 mol/L NaCl increased to above 1
V. To elucidate the protective ability of the passivated alloy surface, themeasurements of depassivation-pH were conducted. In the case of
as-polished surface, the depassivation pH was approx. 2.0, but it
decreased to 0.0 after the electrochemical passivation.

High Entropy Alloys Notable Achievements

A01(b)

2021 MAY

Suppression of Frank loop growth in CoCrFeNiMnx by the control
of stacking fault energy

Naoyuki Hashimoto (Hokkaido University), Eyo Wada (Hokkaido University), Tatsuya Fukushi (Hokkaido University), Hiroshi Oka (Hokkaido University),
Shigehito Isobe (Hokkaido University)

It has been reported that HEAs have unique properties such as a high radiation resistance and corrosion resistance at elevated temperatures compared with conventional nuclear component materials. This attractive property could make HEAs candidates for high temperature
nuclear reactor components. However, the studies on their microstructural evolution and mechanical property change under irradiation,
especially at elevated temperatures, is very limited. In this study, the single-phase FCC type high entropy alloys: CoCrFeNiMnx (x: 0.7~1.3)
were prepared and analyzed to understand the Mn effect on the growth ofFrank loops under irradiation. TEM
observation of deformed HEAs
indicated that the stacking fault energy
would have a positive dependence on
Mn content (Fig. 1(a)). Furthermore,
the irradiation experiments revealed
the suppression of Frank loop growthwith increasing stacking fault energy(Fig. 1(b)).
Fig. 1 (a) Mn content dependence on stacking fault energy of HEAs, (b) the average Frank loop size as
a function of stacking fault energy

A01(b)

High-Entropy Hydrogen Absorbing Alloys with Tunable Chemical
Equilibrium

Etsuo Akiba and Rika Hayashi (Kyushu University)

Laves phase related BCC solid solution alloys for hydrogenstorage have been developed in 1990’s by the author. The
concept of development was to explore at the middle of phase
diagrams not at the corners nor edges. This is the exactly same
concept of high-entropy alloy development. We extend ourconcept for four, five and six element alloy systems under thisprogram.
We developed four element alloys by adding the fourth
elements to the Ti-V-Cr equimolar alloy. Among them, Nb andMo added alloys are pure BCC and readily absorb and desorb
hydrogen. We selected Nb and Mo to form five element highentropy Ti-V-Cr-Nb-Mo alloys and they were successfully
prepared. Both equimolar and Ti0.1V0.3Cr0.2Nb0.1 Mo0.3 are BCC
and desorb and absorb hydrogen at room temperature. They are
the first high entropy pure BCC alloys show hydrogen absorption/desorption at room temperature.
Fig shows the PCT isotherms of TiVCrNbMo at 30˚C. The
green line was the first hydrogen absorption/desorption and thered and orange lines were the second and the third cycle,
respectively. It clearly shows room temperature hydrogen
absorption and good cyclability.

Fig. Hydrogen absorption by TiVCrNbMo high entropy alloy at 30˚High Entropy Alloys Notable Achievements

A02(c)

2021 MAY

A Strengthening Mechanism by Grain-Boundary Segregation in High
Entropy Alloys through Atomic Simulations

Tomotsugu Shimokawa, Kohei Shiotani, Tomoaki Niiyama (Kanazawa University)[1] K. Shiotani, T. Niiyama, T. Shimokawa, “Dislocation Emission from Grain Boundaries in
High-Entropy Alloys: Influence of Atomic Composition at Grain Boundaries”. Materials Transactions., 61(7), (2020), 1272-1279.

A02(c)

0.5

0.5

δ = 0.5, T=0.1Tm

0.4

c GB
i

0.4
0.3

0.3

0.2

0.2

0.1
0.0

δ = 2.3, T=0.1Tm

0.1
1

2.0
1.8

CRSS / (CRSS)rnd

In conventional alloys, smaller excess free volume at grain boundaries (GBs) is
known to increase the stress required for dislocation emission, e.g., twin boundary.
In high-entropy alloys (HEAs) consisting of various elements with different atomic
sizes, smaller GB free volume can be achieved even in large misorientation angles
if GB segregation occurs due to large (small) atoms occupying large (small) atomic
sites. We investigate the possibility of the strengthening mechanism by GB segregation in HEAs through a simple two-dimensional atomic simulation. Virtualequiatomic quinary HEA models with 5 types of atomic size difference δ ranging
from 0 to 2.28 are expressed by a tunable two-body atomic potential [1]. Thermallyequilibrium atomic configurations of 18 types of bicrystal models at different
temperatures (0.01 Tm, 0.1 Tm, 0.3 Tm, 0.5 Tm, 0.7 Tm. Tm = 960 K) obtained byhybrid MD and MC analyses show that stronger GB segregation of the maximum
and the minimum size atoms, which decreases GB free volume, occurs as thetemperature becomes lower (see the right upper figure. Both grain boundaries
have the same misorientation angle of 21.8 degrees but different δ and the largerδ enhances the GB segregation.). Uniaxial tensile and compressive deformation
tests are performed to all cases of bicrystal models at 1K and reveal the suppression of dislocation emission from segregated GBs with small free volumes. As
results, GB segregation could be a strengthening mechanism in HEAs.

2

3

4

5

0.0

1

2

3

4

5

Tensile tests
Compressive tests

1.6
1.4
1.2
1.0
0.8
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
VGB / (VGB)rnd

Geometric Study on Microscopic Structures in Thermodynamic
Equilibrium for High-Entropy Alloys

Koretaka Yuge (Kyoto University)

Whereas microscopic structures (Q) in high-entropy alloys (HEAs) in thermodynamic equilibrium, including short-range ordering (SRO), can be reasonably
predicted for given potential energy surface (U) through statistical mechanics,
nonlinear Q-U correspondence is far from well-understood due to its complexity,
especially enhanced for multicomponent systems. We here tackle this fundamental problem based on a variety of geometry, leading us clear and systematic
insight into how nonlinear character is essentially governed by underlying lattice.
Our recent, main results are: (i) We find that SRO tendency near transition
temperature can be well-characterized by a set of a few specially-selected configurations without requiring any thermodynamic information, i.e., they are common
for any combination of constituents[1]. (ii) We apply tropical geometry to evolutionof the nonlinearity, finding that asymmetric linear character around random stateis mainly bounded by the number of non-crossing, closed path on the lattice,corresponding to spatial constraint on constituents[2]. (iii) Based on Riemannian
manifold with dual-orthogonal foliation, we reveal that the nonlinearity can always
be geometrically decomposed into the sum of three contributions of deviation fromGaussian in individual structural degree of freedom (SDF), entanglement in SDF
and nonadditivity in the entanglement (Fig. 1)[3]. Particularly, the nonadditivity is
specific and enhanced for multicomponent systems, which should play essential
role for cocktail effect in HEAs on the Q-U correspondence nonlinearity.
References: [1] K. Yuge, R. Miyake, S. Ohta, J. Phys. Soc. Jpn. 89, 094803 (2020). [2] K. Yuge
and S. Ohta, J. Phys. Soc. Jpn. 89, 084802 (2020). [3] K. Yuge, arXiv:1811.09612[cond-mat.stat-mech].

FIG. 1: Geometric interpretation of nonlinearity on
α-connected dually flat Riemannian manifold.

High Entropy Alloys Notable Achievements

A02(d)

2021 MAY

First-principles Investigation on Effect of Inhomogeneous in High-Entropy Alloys:
CrFeNiCoMn vs. CrFeNiCoPd, Equiatomic vs. Non-equiatomic Compositions

Tran Nguyen Dung and Ying Chen (Tohoku University)

Cantor alloy CrFeNiCoMn is a well-known HEA which is consist of five 3d elements with similar properties. CrFeNiCoPd has been newly
synthesized with intentionally substituting Mn in Cantor alloy by Pd which has a markedly different atomic size and electronegativity fromthe other constituent elements, and has been achieved in experiments thebetter mechanical properties than Cantor alloy, while manifests rather
bigger fluctuation of atomic composition (Nature, 2019, 574, 223).
Comprehensive DFT-based calculations for both zero K and finite
temperature have been conducted on these two quinary systems using thespecial quasirandom structures (SQSs) in order to investigate the effect of
Pd-to-Mn substitution. It has been found that substituting Mn with Pd in
Cantor alloy introduces the inhomogeneous feature so that increases theaverage atomic local displacement of the CrFeNiCoPd to a moderateamount, consequently enhances the mechanical properties of the new
HEA. We constructed a model of hypothesized equiatomic composition asa mixture of several non-equiatomic compositions to simulate the local
inhomogeneous environment in CrFeNiCoPd, and found that for CrFeNiCoPd, the hypothesized equiatomic composition is more stable than its(a) The fluctuation of atomic compositions in CrFeNi
equiatomic composition, showing an opposite tend in CrFeNiCoMn. This
CoMn and CrFeNiCoPd ((Nature, 2019, 574, 223). (b)explained the experimental observation and gave a hint to design new
Hypothesized equiatomic composition model. (c) Gibbs
HEAs with compromising inhomogeneous and stability.
formation energies as the function of temperature for the
hypothesized (dashed lines) and real equiatomicmodeled (solid lines) equiatomic CrFeNiCoMn (blue)
and CrFeNiCoPd (red).

A02(d)CALPHAD modeling of Effect of Short-Range Ordering in High-Entropy
AlloysTaichi Abe (NIMS), Ikuo Ohnuma (NIMS), Kwangsik Han (NIMS)

In the framework of the CALPHAD (Calculation of phase diagrams) the
description of the short-range ordering (SRO) for binary systems was
expanded to multi-component systems [1]. The effect of SRO in high entropy alloys (HEAs) were estimated based on the Gibbs energy functions fromthe CALPHAD-type thermodynamic assessments. It was applied to the
BCC-based HEA (MoNbTaVW) and FCC-based HEA (CoCrFeMnNi). In thepresent calculation, the total contribution of the SRO to the Gibbs energy
was approximately −1 kJmol−1 and −0.2 kJmol−1 in the BCC- and FCC-based
HEAs at 1000 K, respectively. The variations in the excess Gibbs energy(presented in the right figure) and excess entropy due to SRO in lowerorder systems can be averaged in the HEAs because of the mixing ofmultiple elements, as formally suggested in the previous work [2] for theexcess Gibbs energy in Cantor alloy. It suggested that if the high-entropy
effect on the mechanical properties were originated from SRO, it might not
be related directly to integral quantities but local atomic arrangements.
[1] T. Abe, “Effect of Short-Range Ordering in High-Entropy Alloys”, Mater. Trans., 62[6],(2021), 711-718.
[2] T. Abe, “Thermal Vacancies in High-Entropy Alloys”, Mater. Trans., 61[4], (2020),
610-615.

High Entropy Alloys Notable Achievements

A03(e)

2021 MAY

Characterization of dendritic growth in an equimolar CrMnFeCoNihigh entropy alloy

Hideyuki Yasuda (Kyoto University), Keita Nakano (Kyoto University), Taka Narumi (Kyoto University), Kohei Morishita (Kyoto University, Now at Kyushu
University)

Dendrite arms generally grow along a preferred growth direction which is intrinsically determined by anisotropy of solid – liquid interface
energy. Although most of conventional FCC alloys grow in the <100> directions, some of FCC alloys such as Al-Zn alloys grow in the <110>directions [1]. Solidification structure and microsegregation in the interdendritic region are significantly influenced by the dendritic growth.
Thus, it is of interest to characterize the dendritic growth of high entropy alloys. We have developed a time-resolved in-situ tomography(4D-CT) and X-ray diffraction (XRD). This technique allows to observe
growing dendrites and to determine crystallographic orientation in-situ.
(a)Typical time resolution and special resolution for the observation in
SPring-8 are 0.5 - 8 s and 1 - 7 μm. Figure shows time evolution ofdendrites during cooling at 0.083 K/s in the CrMnFeCoNi alloy [2]. Three-dimensional images were reconstructed from 200 projection images and theimages were improved by an image filter using a phase field model. The
crystallographic orientations measured during cooling is also shown in the
figure. The observations proved that the dendrite arms strictly grew alongthe <100> directions. The specific solid–liquid interfacial area, which was
normalized by the total volume, was also evaluated as a function of solid
fraction. The interfacial area was compatible with the reported values of(b)t
conventional alloys such as Al and Mg alloys. The secondary arm spacing
was on the same order of magnitude as the spacing of conventional alloys.
suOverall, the solidification in this high-entropy alloy can be analyzed bymodels for pseudo-binary alloys.
[1] A. Sémoroz et. al, Acta Mater 49 (2001) 529, [2] K. Nakano et. al, Mater. Trans 61(2020) 596

A03(e)

Multimode Deformation in High-Entropy Alloy at Cryogenic Temperature
Revealed by In Situ Neutron Diffraction

Muhammad Naeem (City University of Hongkong), Haiyan He (City University of Hongkong), Fan Zhang (University of Science and Technology Beijing),
Stefanus Harjo (Japan Atomic Energy Agency), Takuro Kawasaki (Japan Atomic Energy Agency), Si Lan (Nanjing University of Science and Technology),
Xun-Li Wang (City University of Hongkong)Normalized
Integrated Intensity

Temperature (K)Applied True Stress (MPa)Stacking Fault
Probability, SFP (%)

High-entropy alloys exhibit exceptional mechanical properties, high strengths and large elongations accompanied with large work hardening, at cryogenic temperatures. In situ neutron diffraction studies during tensile loading at cryogenic temperatures were performed toelucidate the mechanism of such exceptional mechanical properties. The activation of twinning in addition to dislocation slip was observed
displaying the coexistence of multiple deformation pathways,
and how the individual deformation mechanisms compete or
In situ neutron diﬀrac�on during cryo-loading
synergize during plastic deformation were discussed based on
2500
20
3.0
(1) (2) (3)(4)
the evolutions of lattice strains, dislocation densities and
2.5
2000
18
2.0
σy,15K
textures obtained from neutron diffraction. It was found that the
1500
16
1.5
interaction of a rich variety of deformation mechanisms in
1.0
1000
14
high-entropy alloys at 15 K, began with dislocation slip,
0.5
500
12
followed by stacking faults and twinning, before transitioning to
0.0
010
inhomogeneous deformation by serrations. The cooperation of
0.0 0.1 0.2 0.3 0.4 0.5 0.6
3.0
Applied True Strain
these different deformation mechanisms led to extreme work
2.5
At 15K: (1) macroscopic yield point;
hardening. The stable face-centered cubic structure with the(2) start of SFs; (3) ﬁrst serra�on,
2.0
low stacking fault energy at cryogenic temperatures, enabled
followed by increase in SFP & change
σy,15Kin the slope of texture development;by the high-entropy alloying, played an important role provok1.5
and (4) massive serra�ons coincided
ing and mutually bridging dislocation slip and serration.
1.0
with the satura�on of texture
Insights from these in situ neutron diffraction studies point to0
500 1000 1500 2000 2500
M. Naeem et al., Science Advances
Applied True Stress (MPa)
6 (2020) eaax4002
the role of entropy in the design of structural materials at
cryogenic temperatures with superior properties.

High Entropy Alloys Notable Achievements

A03(f)

2021 MAY

Vacancy Formation Enthalpy in Medium-Entropy and High-Entropy Alloys
Studied by Positron Lifetime Measurements and First-Principles Calculations

Masataka Mizuno (Osaka University), Kazuki Sugita (Osaka University), Hideki Araki (Osaka University)

A03(f)

Vacancy formation enthalpy (eV)Mean positron lifetime (ps)To quantitatively evaluate the vacancy formation enthalpy in medium-entropy and high-entropy alloys, we performed in-situ positron
lifetime measurement under high-temperature condition and first-principles calculations based on the special quasi-random structure (SQS)
approach. Figure 1 shows the temperature dependence of mean positron lifetime in CrFeNi and CoCrFeMnNi alloys. The vacancy formation
enthalpy Hf can be determined by the threshold temperature at which the mean positron lifetime sharply increases. We obtained Hf = 1.80
± 0.14 eV for CrFeNi and Hf = 1.69 ± 0.13 eV for CoCrFeMnNi. These values do not differ much from the vacancy formation enthalpies of
constitutional elements of these alloys. Figure 2 shows the average value of calculated vacancy formation enthalpies of each element in
CrFeNi, CoCrFeNi and CoCrFeMnNi
alloys. The vacancy formation enthalpy
150slightly increases with increasing number
Cr
CrFeNiMn
CoCrFeMnNi
of elements. This trend is partly due to the
Fe
140
2.0
Co
difference in the energy gain by structuralNi
130
relaxations. The addition of Co and Mn to
CrFeNi reduces the energy gain by struc120
1.8
tural relaxation around a vacancy. The
110
general shape of averaged density of
200 400 600 800 1000 1200 1400
34
5states of each element is quite similar
Number of elements
Temperature (K)among these three alloys, which indicatesthat the increase in the number ofFig.1 Temperature dependence of mean
Fig. 2 Vacancy formation enthalpy as apositron lifetime.
function of the number of elements.
elements does not affect the chemicalbonding.

Middle Range Ordering realized in ZrPt Amorphous Alloy

Kazumasa Sugiyama (Tohoku University), Toru Kawamata (Tohoku University)

Atomic ordering in both the short-range region and the middle-range region in amorphous alloys is known to be closely correlated with unique material properties.
AXS-RMC technique is one of the powerful techniques to elucidate the interesting
short and middle range ordering of an amorphous alloy. AXS-RMC study of Zr80Pt20
amorphous alloy reveals a dominant topological short-range ordering of the icosahedral-like cluster. The discussion on such the correlation distance and corresponding
coordination number in the short rage ordering is very useful for understanding thefundamental structural features. However, it is sometimes necessary to conduct
further analysis with respect to the middle range ordering. The present amorphousalloy could be included in this category because the partial pair distribution function of
the Pt-Pt pair indicates a significant enlargement at approximately 0.45 nm in thesecond-nearest neighbor region. The middle range connection specified by the two Pt
atoms can be considered as a unit of face-sharing tetrahedra (FST), which lead to oneof the dense packing structural units among Bernal polyhedral. And further analysis
indicates the strong preference of the chemically featured Pt-Zr3-Pt middle range
linkage, by suggesting the strong chemical affinity between Pt and Zr. This is also
attributed to the saturation of the quasicrystalline phase found in the annealed
Zr80Pt20. Present AXS-RM analysis also revealed unique middle-range linkages basedon non-Bernal polyhedra, having a higher and lower packing density of atoms withslight preference for Zr and Pt, respectively. Notably, such chemical and density fluctuations identified by using the concepts of the Bernal polyhedral units are expected tobe utilized for characterizing the middle range ordering of a variety of amorphous alloy
systems.

The middle-range Pt-Pt correlations
realized in Zr80Pt20 amorphous alloy.

High Entropy Alloys Notable Achievements

2021 MAY

AWARD
Akihiko Chiba, April 2020, Commendation for Science and Technology (Research Division), The Minister of Education, Culture, Sports,
Science and Technology, Japan.
Nagase Takeshi, Terayama Akira, Nagaoka Takashi, Fuyama Nobuyuki and Sakamoto Tatsuaki, May 2020, The Best Paper Award,
Japan Foundry Engineering Society.
Koichi Tsuchiya, September 2020, The 17th Murakami Memorial Award, The Japan Institute of Metals and Materials.
Akira Takeuchi, Takeshi Wada and Hidemi Kato, September 2020, The 68th Best Paper Award (Materials Processing Category), The
Japan Institute of Metals and Materials.
Akira Takeuchi, Takeshi Wada and Hidemi Kato, September 2020, The 68th Best Paper Award (Material Characteristics Category), The
Japan Institute of Metals and Materials.
Naohiro Hayashi, Kazuki Nakashima, Masanori Enoki, Hiroshi Ohtani, September 2020, The Best Paper Award for Young Speaker, The
Japan Institute of Metals and Materials.
Takaaki Hara, Toshiki Ishida, Katsunari Oikawa, September 2020, The Best Paper Award for Young Speaker, The Japan Institute of
Metals and Materials.
Tomohiro Nishimura, Ryota Matsubayashi, Kouhei Morishita, Masato Yoshiya, Tomoya Nagora and Hideyuki Yasuda, March 2021, TheBest Paper Award (Sawamura Award), The Iron and Steel Institute of Japan.
Masaki Tanaka, Scientific Achievement Commemorative Prize (Nishiyama Commemorative Prize), The Iron and Steel Institute ofJapan.

PRESS
1

The Science News, 15 January 2021, “Deformation observation of high Mn steel: Elucidation of serration behavior-, in Kyoto
University”, Sukyoung Hwang, Myeong-Heom Park, Yu Bai, Akinobu Shibata, Wenqi Mao, Hiroki Adachi, Masugu Sato and Nobuhiro
Tsuji.

2

Kyoto University HP: Latest research news, 25 December 2020, Elucidation of serration behavior -Approaching the fundamental
mechanism of deformation in high Mn steel showing high strength and high ductility”, Sukyoung Hwang, Myeong-Heom Park, Yu Bai,
Akinobu Shibata, Wenqi Mao, Hiroki Adachi, Masugu Sato and Nobuhiro Tsuji.

3

Press Release, 25 August 2020, “Elucidation of cast iron strengthening mechanism by high-intensity neutron beam, -Observation ofcast iron microstructure at atomistic scale by in-situ neutron diffraction experiment-”, Stefanus Harjo, Takuro Kawasaki, Wu Gong,
Satoru Kubota, Si Gao.

4

Kyoto Shimbun, Morning edition: 12 August 2020, “Fabrication of a uniform alloy with 6 platinum family elements”, Hiroshi Kitagawa.

5

Yume Navi Web Lecture No.10234, 24 April 2020, “By controlling “powder” you can freely create new materials“, Hiroyuki Muto.

6

Press Release, 7 April 2020, “Elucidation of spontaneous fracture of Aluminum, - Investigating the cause of aluminum brittlenesswith hydrogen and expectations for high-strength alloys from computational materials science”, Tomohito Tsuru.

7

Press Release, 28 March 2020, “Elucidation of the unique deformation mechanism observed at extremely low temperatures inadvanced alloys, -Expectations for the development of high-performance low-temperature structural materials useful for spacetechnology-”, Xun-Li Wang, Stefanus Harjo, Takuro Kawasaki, et al.

High Entropy Alloys Notable Achievements

2021 MAY

LATEST INFORMATIONInternational Meeting
International Conference on Processing & Manufacturing of Advanced Materials (Thermec’2021), May 10-14, 2021 - Virtual Conference.
https://www.tugraz.at/events/thermec-2020/home/
International Conference on Advances in High-Entropy Alloys (ICAHEA 2021:15), June 3-4, 2021 in New York, USA.
https://waset.org/advances-in-high-entropy-alloys-conference-in-june-2021-in-new-york
International Conference on High-Entropy Alloy Design (ICHEAD 2021: 15), September 16-17, 2021 in Amsterdam, Netherlands.
https://waset.org/high-entropy-alloy-design-conference-in-september-2021-in-amsterdam
The Materials Science & Technology (MS&T) technical meeting and exhibition, October 17-21, 2021, Columbus, Ohio, USA.
https://www.matscitech.org/mst21
6th World Congress on Integrated Computational Materials Engineering (ICME 2021), November 14–18, 2021, Lake Tahoe, Nevada, USA
https://www.tms.org/icme2021
2021 MRS Fall Meeting & Exhibit, November 28 - December 2, 2021, Boston, Massachusetts, USA.
https://www.mrs.org/meetings-events/fall-meetings-exhibits/2021-mrs-fall-meeting
The 2nd World Congress on High Entropy Alloys (HEA 2021), December 5–8, 2021, Charlotte, North Carolina, USA.
https://www.tms.org/portal/MEETINGS___EVENTS/TMS_Meetings___Events/Upcoming_TMS_Meetings/HEA2021/portal/Meetings___Events/2021/HEA2021/default.aspx?hkey=51531264-7d36-4089-aa6f-ac3f591e2681
Materials Research Meeting 2021 (MRM 2021), December 13-17, 2021, Pacifico Yokohama, Japan.
https://mrm2021.jmru.org/
TMS 2022 151st Annual Meeting & Exhibition, February 27–March 3, 2022, Anaheim, California, USA.
https://www.tms.org/tms2022
International Conference on Advances in High-Entropy Alloys (ICAHEA 2022:16), March 15-16, 2022 in London, UK.
https://waset.org/advances-in-high-entropy-alloys-conference-in-march-2022-in-london

Domestic Meeting
2021 Startup Meeting of All Research Groups, May 20-21, 2021, Kyoto, Japan.
https://highentropy.mtl.kyoto-u.ac.jp/members
The Ceramic Society of Japan, The 34th Fall Meeting, September 1-3, 2021, Online Meeting, Japan.
https://fall34.ceramic.or.jp/
The Japan Institute of Metal (JIM) Symposium “Materials Science of High-Entropy Alloys”, September 14-17, 2021, Online Meeting, Japan.
https://jim.or.jp/MEETINGS/me_index.html

High Entropy Alloys
Science of New Class of Materials Based on
Elemental Multiplicity and Heterogeneity

CONTACTHEA Secretariat: In the Inui Research Group, Department ofMaterials Science and Engineering, Kyoto University
Yoshida Honmachi, Sakyo-ku, Kyoto, 606-8501, Japan
Tel: +81-75-753-5481, E-mail: hea-office@mtl.kyoto-u.ac.jp