Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K
Mechanical properties of a nanocrystalline (~ 60 nm) and a coarse grained (grain sizes ~ 4 µm) CoCrFeNiMn high entropy alloys were studied in uniaxial compression in the temperature range 4.2–350 K. Temperature dependences of yield strength, flow stress and strain rate sensitivity have been registe...
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| Date: | 2018 |
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Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
2018
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| Cite this: | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K / A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, M.J. Zehetbauer // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1245-1253. — Бібліогр.: 36 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859879394383757312 |
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| author | Podolskiy, A.V. Schafler, E. Tabachnikova, E.D. Tikhonovsky, M.A. Zehetbauer, M.J. |
| author_facet | Podolskiy, A.V. Schafler, E. Tabachnikova, E.D. Tikhonovsky, M.A. Zehetbauer, M.J. |
| citation_txt | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K / A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, M.J. Zehetbauer // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1245-1253. — Бібліогр.: 36 назв. — англ. |
| collection | DSpace DC |
| container_title | Физика низких температур |
| description | Mechanical properties of a nanocrystalline (~ 60 nm) and a coarse grained (grain sizes ~ 4 µm) CoCrFeNiMn
high entropy alloys were studied in uniaxial compression in the temperature range 4.2–350 K. Temperature dependences of yield strength, flow stress and strain rate sensitivity have been registered and analyzed in the framework of
two thermal activation deformation models, that of thermal activation of local barrier overcoming, and that of
Peierls valley double kink formation. Microscopic parameters of dislocation interaction with the barriers for thermally activated motion are estimated and low temperature deformation mechanisms are discussed.
Механічні властивості нанокристалічного (середній розмір
зерен ~ 60 нм) та крупнозернистого (середній розмір зерен
~ 4 мкм) високоентропійного сплаву CoCrFeNiMn вивчались
шляхом одноосного стискання в інтервалі температур
4,2–350 К. Температурна залежність межі плинноcті, напруження течії та швидкісної чутливості деформуючого напруження виміряно та проаналізовано в рамках двох термоактиваційних моделей: моделі взаємодії дислокацій з локальними
бар’єрами та моделі Пайєрлса щодо утворення подвійних перегинів. Визначено мікроскопічні параметри взаємодії дислокацій
з бар’єрами при термоактивованому русі та обговорюються
низькотемпературні механізми, які контролюють пластичну
деформацію.
Механические свойства нанокристаллического (средний
размер зерен ~ 60 нм) и крупнозернистого (средний размер
зерен ~ 4 мкм) высокоэнтропийного сплава CoCrFeNiMn
изучались путем одноосного сжатия в интервале температур 4,2–350 К. Температурная зависимость предела текучеcти, напряжения течения и скоростной чувствительности
деформирующего напряжения измерены и проанализированы в рамках двух термоактивационных моделей: модели
взаимодействия дислокаций с локальными барьерами и
модели Пайерлса образования двойных перегибов. Определены микроскопические параметры взаимодействия дислокаций с барьерами при термоактивированном движении и
обсуждаются низкотемпературные механизмы, которые
контролируют пластическую деформацию.
|
| first_indexed | 2025-12-07T15:52:10Z |
| format | Article |
| fulltext |
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9, pp. 1245–1253
Thermally activated deformation of nanocrystalline and
coarse grained CoCrFeNiMn high entropy alloy
in the temperature range 4.2–350 K
A.V. Podolskiy1, E. Schafler2, E.D. Tabachnikova1,
M.A. Tikhonovsky3, and M.J. Zehetbauer2
1B. Verkin Institute for Low Temperature Physics and Engineering
47 Nauky Ave., Kharkiv 61103, Ukraine
E-mail: podolskiy@ilt.kharkov.ua
2Physics of Nanostructured Materials, Faculty of Physics, University of Vienna
Boltzmanngasse 5, A-1090 Wien, Austria
3National Science Center, Kharkov Institute of Physics and Technology
1 Akademicheskaya Str., Kharkiv 61108, Ukraine
Received April 16, 2018, published online July 26, 2018
Mechanical properties of a nanocrystalline (~ 60 nm) and a coarse grained (grain sizes ~ 4 µm) CoCrFeNiMn
high entropy alloys were studied in uniaxial compression in the temperature range 4.2–350 K. Temperature depend-
ences of yield strength, flow stress and strain rate sensitivity have been registered and analyzed in the framework of
two thermal activation deformation models, that of thermal activation of local barrier overcoming, and that of
Peierls valley double kink formation. Microscopic parameters of dislocation interaction with the barriers for ther-
mally activated motion are estimated and low temperature deformation mechanisms are discussed.
Keywords: high entropy alloy, nanocrystalline, low temperature, dislocation, thermal activation analysis.
1. Introduction
The high entropy alloys (HEAs) are new and intriguing
materials [1–4], which have unique mechanical properties
such as a combination of high strength and good plasticity,
high fracture toughness in a wide range of low tempera-
tures, high thermal stability, and others. These properties
are related to the multicomponent structure of the alloys
and distorted crystal lattice due to presence of elements
with different atomic radius. At present, the most promi-
nent HEA is CoCrFeNiMn, which has a single fcc phase
and high plasticity at all temperatures, including cryogenic
ones [4–7]. The carriers of plasticity are reliably found in a
wide range of temperatures [5,6]. The principles of the
thermally activated plastic deformation of coarse grained
CoCrFeNiMn alloy, which govern the temperature de-
pendences of strength and strain rate sensitivity at low ho-
mologous temperatures, were attempted to study in several
works [8–10], but they were not sufficiently clarified
(mainly due to absence of the detailed temperature de-
pendence of yield stress and strain rate sensitivity), which
therefore will be the main task of this work.
The nanocrystalline state of the CoCrFeNiMn alloy
achieved by high pressure torsion (HPT) at a processing
temperature 300 K, demonstrates both an outstanding
strength and at the same time good plasticity [11,12], while
the deformation mechanisms behind still are not clear so
far. Therefore, the mechanical properties of the coarse
grained (CG) and nanocrystalline (NC) CoCrFeNiMn HEA
will be studied and compared in a broad range of low tem-
peratures; a careful thermal activation analysis of the ex-
perimental data should allow to clarify the microscopic
mechanisms of the thermally activated plastic deformation
of both structural states of CoCrFeNiMn in question.
2. Materials and methods
Ingots of the equiatomic fcc CoCrFeNiMn high entropy
alloy were produced by arc melting of the components in
high-purity argon inside a water-cooled copper cavity. The
purities of the alloying elements were higher than 99.9%.
© A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, and M.J. Zehetbauer, 2018
A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, and M.J. Zehetbauer
To ensure chemical homogeneity, the ingots were flipped
over and re-melted at least 5 times. After that, the homog-
enization annealing was carried out at 1000 °C for 24 h (in
vacuum), which was followed by rolling from 5.3 to
2 mm, annealing at 800 °C (1 h), rolling from 2 to 1 mm,
annealing at 800 °C (1 h). The average grain size after such
treatment was 4 µm.
Severe plastic straining of the alloy was performed by
the High Pressure Torsion (HPT) method. Disc-shaped
billets with diameter 10 mm and thickness 0.9 mm were
processed by 5 rotations of HPT at a hydrostatic pressure
of 6 GPa and temperature 300 K. Plungers have been rotat-
ed by a speed of 0.2 rot/min. It is known that such HPT
regime allows to produce uniform NC structural state with
average grain sizes 50–60 nm [11,12].
Compression samples with the shape of rectangular
prisms 0.8 × 0.8 × 1.3 mm, were cut from the HPT discs.
CG compression samples with the same dimensions were
cut from the initial discs.
The mechanical characteristics of HPT processed as well
as of CG CoCrFeNiMn samples were studied in a MRK-3
deformation machine at initial strain rate 3·10−4 s−1. Cryo-
genic temperatures were achieved by liquid nitrogen and
helium and temperatures above 290 K were achieved by
hot air.
During the measurement of the deformation curves, the
shear flow stress sensitivity / ln∆τ ∆ ε was estimated from
the change in the flow stress by increasing the rate of de-
formation by a factor of 9. The resolved shear stress τ was
expressed by the relation τ = σ/3 typical for texture free fcc
polycrystalline materials [13].
The values of apparent activation volume for the pro-
cess of plastic deformation were calculated from the rate
sensitivity of yield stress [14]
ln( )
( )
V T kT
T
∆ ε
=
∆τ
(1)
where k is the Boltzmann constant.
For the thermal activation analysis of the NC and CG
structural states, the temperature dependences of the shear
flow stress τ(T) and of the strain rate sensitivity
/ ln ( )T∆τ ∆ ε are required, which have been registered at the
stage of well developed plastic strain, but very close to the
yield limit to reduce influence of strain hardening at diffe-
rent temperatures: in this work the values at 1% of plastic
strain are analyzed. In NC state the strain rate sensitivity was
registered within a temperature range of 65–350 K, as rela-
tively low plasticity below 65 K does not allow to reliably
determine the / ln∆τ ∆ ε values.
3. Experimental results
The temperature dependences of the yield strength σ0.2
of the HPT deformed NC and initial CG CoCrFeNiMn
high entropy alloy can be seen in Fig. 1.
The strength of CG CoCrFeNiMn (Fig. 1) well com-
bines with the literature data for the tension of the samples
with comparable grain sizes (~ 5 µm) [6] and (~ 17 µm)
[10]. The comparison of yield strength at different com-
pression temperatures shown in Fig. 1 demonstrates that
decrease of grain size from 4 µm to approximately 60 nm
leads to significant (5–6 times) increase of strength. The
value of the yield strength at 300 K in tension (1.95 GPa)
of HPT CoCrFeNiMn [11] is in good correlation with the
value of yield strength in compression (Fig. 1) — 2 GPa,
so very weak SD effect (strength difference in tension and
compression) is observed.
The plasticity of the NC CoCrFeNiMn in compression is
rather high in a wide temperature range: approximately 10%
at 350 K, increasing up to 30% at 200 K, decreasing to 10%
at 77 K and approximately to 1% at 4.2 K. At the tempera-
ture 4.2 K, significantly serrated plastic deformation is regis-
tered in the CG and NC states, which can be explained by
collective avalanche-type motion of dislocations [15].
The temperature dependences of the shear flow stress τ(T)
and of the strain rate sensitivity / ln ( )T∆τ ∆ ε have been
determined at 1% of plastic strain and are shown in Fig. 2
(τ1(T)) and Fig. 3 ( / ln ( )).T∆τ ∆ ε A wide maximum is ob-
served in the / ln ( )T∆τ ∆ ε dependence at 150–250 K for NC
state and at 100–200 K for CG state. Such “bell-shaped”
temperature dependence of the strain rate sensitivity is typical
of many metals with fcc, hcp and bcc crystal lattice.
From the flow stress sensitivity for strain value 1%
(Fig. 3), the activation volume calculated according to rela-
tion (1), shown in Fig. 4 in b3 units, where b is Burgers
vector, being for fcc structures, with a = 3.6 Å [16] as the
lattice parameter.
The activation volume of the CG CoCrFeNiMn high en-
tropy alloy had been evaluated from strain rate change and
stress relaxation tests in several works: 18 b3 (at 77 K) and
85 b3 (at 293 K) [8]; 40 b3 (at 293 K) [9]; 60 b3at (77 K) and
Fig. 1. Temperature dependence of yield strength σ0.2 in com-
pression of nanocrystalline (grain size ~ 60 nm) and initial coarse
grained (grain size ~4µm) CoCrFeNiMn high entropy alloy.
1246 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy
340 b3 (at 293 K) [10]. Large difference in values partly can
be explained by difference in the used Taylor factor ( 3, 2,
3), different grain sizes of the samples and the different type
of experiments (strain rate jumps and relaxation), but never-
theless it should be noted that the observed variance of the
activation volume values is much higher than variance of the
corresponding strengths characteristics and maybe more
fundamental reasons underline it.
The values and temperature dependence of the activa-
tion volume of the NC CoCrFeNiMn alloy in general are
similar to those observed in NC fcc alloys [17].
4. Analysis and discussion
The microscopic mechanisms of plastic strain in CG fcc
CoCrFeNiMn high entropy alloy have been discussed in
[5,6,18] in a wide range of low temperatures: the main de-
formation mechanism is typical of fcc materials sliding of
full <110> {111} dislocations; twinning is registered at
300 K and its activity is increasing with decrease of tempera-
ture [6,18,19]. It was found [18,19] that twinning actively
participates in the plastic deformation at later stages of the
deformation curve (typically after 5% of plastic strain). Thus
it can be expected that only dislocation processes are respon-
sible the experimental data (Figs. 2–4). Compression tests in
the CoCrFeNiMn single crystal allowed to estimate the criti-
cal resolved shear stress (CRSS) for <110> {111} disloca-
tions at temperatures 300 and 77 K (70 and 175 MPa corre-
spondingly) [20]. These values cannot be directly compared
to shear stress values of polycrystals (Fig. 2) due to differ-
ent values of internal stresses, but the difference τcrss77 –
τcrss300 = = 105 MPa in the single crystal is roughly com-
parable to difference τCG77 – τCG300 = 71 MPa of CG
CoCrFeNiMn (Fig. 2(b)), indicating that the shear stress
(Fig. 2(b)) can be considered as a stress acting at the full
dislocation in its glide plane. In NC state, however, this
difference is as large as τNC77 – τNC300 = 269 MPa, indi-
cating that in this state the temperature dependence of
strength cannot be explained by thermally activated motion
of dislocations inside the grains.
The present CoCrFeNiMn alloy demonstrates a rather
strong temperature dependence of the flow stress (Figs. 1, 2)
in CG as well as in NC state (approximately 1.7–1.8 times
Fig. 2. (Color online) Temperature dependences of the shear
stress τ1 (at 1% plastic strain) of the CoCrFeNiMn high entropy
alloy in nanocrystalline (a) and coarse grained (b) states. The
lines are theoretical dependences (see Sec. 4).
Fig. 3. (Color online) Temperature dependences of the strain rate
sensitivity 1/ ln∆τ ∆ ε (at 1% plastic strain) of the CoCrFeNiMn
high entropy alloy in nanocrystalline (a) and coarse grained (b)
states. The lines are theoretical dependences (see Sec. 4).
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1247
A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, and M.J. Zehetbauer
increase of strength at 4.2 K in comparison with 350 K), in-
dicating that plastic deformation occurs thermally activated.
In CG fcc metals and alloys at low temperatures the tempera-
ture dependence of flow stress is typically rather weak, and
plastic straining is controlled by thermally activated motion
of dislocation through the local barriers inside the grains [14],
and the typical local barriers are forest dislocations, impurity
atoms and clusters, small precipitates, etc. In bcc metals,
however, the thermally activated motion of dislocations in
the Peierls potential relief determines the macroscopic
strength [21] and gives much higher temperature dependence
of flow stress than in fcc metals. The measured temperature
dependence of strength in CG CoCrFeNiMn is in the middle
of fcc and bcc cases, which suggests to apply also the Peierls
potential model to this fcc alloy. It is interesting to note that
temperature dependences of flow stress for fcc CoCrFeNiMn
HEA and for bcc Ti30Zr25Hf15Nb20Ta10 HEA [22] are rather
similar, and as the both models (local barriers and motion in
the Peierls potential relief) successfully were applied for
approximation of the experimental data for the bcc HEA al-
loy [22], it can be considered as additional argument for trying
the Peierls potential model for the fcc CoCrFeNiMn alloy.
The microscopic plasticity mechanisms of the NC mate-
rials with the grain sizes below 100 nm have not been fully
clarified yet, but it has been reported [23,24] that for grain
sizes above approximately 20 nm the plasticity is realized
by dislocation motion. Similar temperature dependences of
the flow stress and strain rate sensitivities in NC and CG
states (Figs. 2, 3) suggest that in NC state these tempera-
ture dependences are also related to the thermally activated
motion of dislocations, which allows to apply the thermally
activation analysis to the experimental data of NC
CoCrFeNiMn (Figs. 2–4), results of it will be discussed.
Description of the thermally activated process of plastic
deformation in the framework of the transition state theory
[14,25] allows relate the plastic strain rate ε , activation
enthalpy H and temperature T by the Arrhenius-type ex-
pression:
*
0
( )exp ,H
kT
τ
ε = ε −
(2)
where the pre-exponential factor 0ε is constant to a good
approximation, *τ = τ – τi is thermally activated (effec-
tive) component of the flow stress τ, and τi is the athermal
component arising from internal stresses.
4.1. Local barriers
The thermally activated motion of dislocation over the lo-
cal barriers often is described by two models (two statistics):
for sufficiently small values of *τ (almost straight disloca-
tion line) the Mott–Labusch statistics [26] applies, while for
significantly curved dislocation segments the Friedel sta-
tistics [27] is to be used. Reasonable correlation of the exper-
imental data (Figs. 2–4) with the theory was achieved only
for the Friedel model, which thus will be described here in
more detail. The analytical approximation of the activation
enthalpy for the Friedel model [27–29] reads as
2/3
*
0( *) 1 , 1 2,
q
c
H H q
τ τ = − ≤ ≤ τ
(3)
Table 1. Empirical values of the parameters for the nanocrystalline structural state
Model τi, GPa τc (τp), GPa H0(2Hk), eV Tc, K A q
Local barriers 0.627 0.512 0.65 384 19.51 1.4
Peierls (regime 1) 0.617 0.458 0.74 420 20.40 –
Fig. 4. Temperature dependences of the activation volume
(measured at the value of plastic strain 1%) of the CoCrFeNiMn
high entropy alloy in nanocrystalline (a) and coarse grained (b)
structural states. The lines are theoretical dependences (see Sec. 4).
1248 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy
where H0 is the enthalpy parameter of the dislocation-
barrier interaction, τc is the critical stress for non-thermally
activated motion of dislocation over the barrier, and q is a
numerical parameter, which depends on the barrier shape.
Relations (2) and (3) provide expressions (4)–(6) for the
experimentally measured characteristics of plasticity, i.e.,
the flow stress τ, strain rate sensitivity / ln∆τ ∆ ε , and the
effective activation volume of plastic deformation V:
3/21/
( ) 1 ,
q
i c
c
TT
T
τ = τ + τ −
(4)
1/21/ 1/3
1 .
ln ln 2
q q
c
c cT T
T T
qA T T
τ∆τ ∂τ ≈ = − ∆ ε ∂ ε
(5)
1/2( 1)/ 1/
0
*
2
1 .
3
q q q
c c cT
qHH T TV
T T
−− ∂ = − = − τ ∂τ
(6)
Here, the parameter ( )0ln /A = ε ε should not depend signif-
icantly on temperature and stress; above the critical tempera-
ture Tc = H0/kA the thermal part of the flow stress is negligi-
ble. The parameters τc, τi and H0 depend on the shear
modulus G, and correspondingly depend on temperature as
the shear modulus does. Use of relations (4)–(6) in a wide
temperature range requires to take into account the tempera-
ture dependence of these parameters, but here the investiga-
tion is limited by a temperature range around 300 K, so in
first approximation the corrections due to the temperature
dependence of the shear modulus can be neglected.
The parameter A can be estimated by the relation
1
ln T
dA T
dT
−
ε
∆τ τ = − ∆ ε
, (7)
which one receives from expressions (4) and (5) considering
dτi/dT << dτ/dT [29]. Empirical estimates of the parameter
A, obtained with relation (7) and the experimental depend-
ences ( )Tτ and / ln ( )T∆τ ∆ ε (Figs. 2, 3), are shown in
Fig. 5 for the NC and CG structural state. As the parameter
A does not depend significantly on temperature, the assump-
tion 0ε = const holds, being one of the criteria for the ap-
plicability of relations (4)–(6) for describing the process of
thermally activated plastic flow.
The theoretical equations ( )Tτ , / ln ( )T∆τ ∆ ε and V(T)
(4)–(6) can be fitted to the experimental dependences
(Figs. 2–4) to determine material parameters q, τi, τc, H0,
Tc, A for the model of local barriers. The best fit values of
parameters are listed in the first line of Table 1 for NC
state and Table 2 — CG state.
The experiments’ dependences and approximating theo-
retical curves (marked as “Local barriers”) in Figs. 2–4 show
that in the whole temperature range 25 K ≤ T ≤ 350 K con-
sidered for the CG state, and 65 K ≤ T ≤ 350 K for the NC
state, good coincidences of the theoretical and experimental
results were achieved, which suggests to consider one single
mechanism to control the thermally activated plasticity in the
temperature ranges studied.
For the Friedel statistics, the average area S0 per local
obstacle in the slip plane of a dislocation can be written in
the form [27,30].
Table 2. Empirical values of the parameters for the coarse grained structural state
Model τi, GPa τc (τp), GPa H0(2Hk), eV Tc, K A q
Local barriers 0.145 0.134 0.63 353 20.80 1.71
Peierls (Regime 1) 0.147 0.100 0.65 365 20.76
Peierls (Regime 2) 0.143 0.110 0.54 330 19.00
Fig. 5. Temperature dependence of the parameter A in
nanocrystalline (a) and coarse grained (b) structural states.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1249
A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, and M.J. Zehetbauer
332 *
0 3
b b VS
G w b
τ =
, (8)
where G is shear modulus, and *( )w w= τ is half-width of
the barrier for thermal activation.
Using Eq. (8), the values of activation volume (see
Fig. 4), and those of the shear modulus of CoCrFeNiMn
alloy being G = 80 GPa [31] can be derived. Assuming
w ≥ b, upper estimates of the average area per local obsta-
cle S0 can be achieved, being S0CG ≤ 340b2 for the CG
state, and S0NC ≤ 58b2 for the NC state; they correspond to
the following average distances between the local obstacles
in the slip plane: l0CG = (S0CG)1/2 < 18.4b = 4.7 nm for CG
state, and l0NC < 7.6b = 1.9 nm (for NC state).
4.2. Peierls barriers
In the frame of this model, the thermally activated mo-
tion of dislocations in the Peierls potential relief below the
critical temperature Tc is realized by nucleation and expan-
sion of kink pairs at the dislocation line [25,32]. Two dif-
ferent regimes of the kink–kink interaction are considered
[25,32,33]: in regime 1 at low *τ values (at high tempera-
tures), the kinks are fully formed and separated, and the
enthalpy balance is governed by the elastic interaction be-
tween kinks; in regime 2 at high *τ values (at low temper-
atures), the dislocation has not reached the adjacent Peierls
valley; the kinks have not fully formed yet and can be de-
scribed by the line tension model.
In the regime 1, the activation enthalpy is represented by
the formation of kink pairs, that is, associated with elastic
repulsion of the kink pair. This can be quantified according
to [25,34] as
1/2
*
2 1kp k
p
H H
τ ∆ = − τ
(9)
where Hk is the formation enthalpy of the isolated kink,
and pτ is the critical stress of the athermal part of disloca-
tion motion over the Peierls barrier.
Combining equations (2) and (9), expressions for the
flow stress τ, strain rate sensitivity / ln∆τ ∆ ε , and the acti-
vation volume of plastic deformation V can be obtained as
follows:
2
( ) 1 ,i p
c
TT
T
τ = τ + τ −
(10)
2
1
ln ln
p
c cT T
T T
A T T
τ ∆τ ∂τ ≈ = − ∆ ε ∂ ε
, (11)
1
*
1 .
k
p cT
HH TV
T
− ∂ = − = − τ∂τ
(12)
Where ( )0ln / ,A = ε ε and Tc = 2Hk/kA.
Joint approximation of the experimental data (Figs. 2–4)
by the relations (10)–(12) allows to self-consistently find the
values of all theoretical parameters τi, τp, Hk, Tc, A, which are
given in line 2 of Tables 1 and 2 for the NC and CG state
correspondingly. Note that the approximated value of param-
eter A coincides well with its empirical value calculated by
Eq. (7) (also shown in Fig. 5), which is an additional prove of
the consistency of the model. The Regime 1 of the thermally
activated flow typically is valid at relatively low stresses
* /2pτ < τ [32], and correspondingly the relations (10)–(12)
should correlate with the experimental data at not too low
temperatures (e.g., above 100–150 K). However, it can be
seen from Figs. 2–4 that even in the whole range of low
temperatures studied, the theoretical curves (10)–(12) of the
regime 1 of the Peierls model (noted as “Peierls, Regime 1”
at Figs. 2–4) are in good correlation with the experimental
data.
At high values of *τ (at low temperatures) the line ten-
sion approximation of the kink interaction (Regime 2)
gives the activation enthalpy [25,34] in the form
5/4
*6 22 1
5 3kp k
p
H H
τ ∆ = − τ
(13)
where Hk is formation enthalpy of the isolated kink, and
pτ is the critical stress of the non-activated motion of dis-
location over the Peierls barrier.
Now, the temperature dependences of the flow stress τ,
strain rate sensitivity / ln∆τ ∆ ε , and the activation volume
of plastic deformation V can be obtained also for the re-
gime 2, with the use of (2) and (13):
4/5
3 5( ) 1 ,
2 6i p
c
TT
T
τ = τ + τ −
(14)
4/5
6 5
ln ln 5 6
p
cT T
T
A T
τ ∆τ ∂τ ≈ = ∆ ε ∂ ε
, (15)
1/5
*
2 5
6
k
p cT
HH TV
T
∂ = − = τ ∂τ
, (16)
where ( )0ln /A = ε ε , and Tc = 2Hk/kA.
Approximation of ( )Tτ and / ln ( )T∆τ ∆ ε (Figs. 2(b),
3(b)) by the relations (14) and (15) for the CG alloy gives
empirical values of the parameters τi, τp, Hk, Tc, A (line 3
of the Table 2). It can be seen from Figs. 2(b) and 3(b) that
the low temperature model of the Regime 2 is valid at tem-
peratures below 100–150 K, and that at higher tempera-
tures the elastic approximation of regime 1 more adequate-
ly corresponds to experimental data. For the NC alloy, the
low plasticity below 65 K did not allow to measure the
strain rate sensitivity, and correspondingly there are not
sufficient experimental points to perform approximations
for the low temperature regime 2 as well.
1250 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy
4.3. Discussion of the thermally activated plastic
deformation
As the thermally activated motion of dislocations over
the local barriers inside the grains is the main microscopic
plasticity mechanism of the CG CoCrFeNiMn high entropy
alloy, the knowledge on microscopic parameters of the
thermal activation analysis (Table 2) could help to identify
the type of barriers. Considering forest dislocations as the
possible local barriers — taking into account that the area
per local obstacle is S0CG ≤ 340b2 — an estimation of the
required dislocation density gives 1/S0CG ≥ 4.5·1016 m–2,
which is too high for CG not severely deformed material.
Impurity atoms also cannot be these local barriers, because
the alloy doesn’t contain the impurity, whose concentration
would provide the estimated distance between the barriers
4.5 nm. Alloy atoms also cannot represent these local bar-
riers, because the alloy concentration is much too high to
provide the estimated barrier distance of 4.5 nm. However,
several neighboring atoms of the present HEA alloy with
relatively high atomic radius can cause distinctly increased
lattice distortions, and therefore may act as the barriers for
the dislocation motion. Indeed, such “clusters” of atoms
were experimentally observed in high entropy alloys [35],
with a typical distance between them of several nanome-
ters; this value equals that from the estimation done by the
thermally activation analysis by means of the local barrier
model. Moreover, the value of activation energy 0.63 eV
(Table 2) obtained from this model is more typical of a
complex local obstacle than of a single impurity atom; al-
together an interpretation of plasticity process with the
thermally activated overcome of complex atom clusters
seems to be rather convenient. Unfortunately, at the mo-
ment no detailed statistics is available of the clusters sizes
and distribution, which not allows more exact analysis.
Alternatively, motion of dislocation in grains of CG
CoCrFeNiMn can be controlled by thermally activated over-
coming by dislocations of the Peierls potential relief — the
model demonstrates good correlation with the experimental
results (Figs. 2–4). The activation energy (energy of the kink
pair formation) for the low and high temperature regimes of
the Peierls barrier model of CoCrFeNiMn (Table 2) (0.54 eV
and 0.65 eV) are in reasonable correlation with the kink pair
formation energy of the metals (elements of the alloy), whose
dislocation motion is controlled by the Peierls barriers: Fe —
0.58 eV, Cr — 0.93 eV [21]. Modelling of the single crystal
CoCrFeNiMn alloy utilizing the Peierls–Nabarro formalism
by density functional theory calculations [20] gives estima-
tion of the Peierls stress: 178 MPa. This estimate is in rather
good agreement with the values of the Peierls stress from the
thermal activation analysis (Table 2) 100 MPa and 110 MPa
for the Regimes 1 and 2 correspondently.
Such agreement of the thermal activation analysis with es-
timate of the Peierls stress from the single crystal modeling
and good correlation of the Peierls model with the experi-
mental results (Figs. 2–4) allow to consider at the moment
the thermally activated overcoming by dislocations of the
Peierls potential relief as the most probable microscopic
mechanism, which control the motion of dislocations in
grains of the CG CoCrFeNiMn alloy. However, when micro-
scopic parameters of dislocation interaction with the local
clusters as well as a statistics of the cluster’s distribution will
be available, the additional comparison of the models will be
required. It also should be noted that both models (local clus-
ters and Peierls barriers) give very similar values of the mi-
croscopic parameters of the dislocation-barrier interaction
(Table 2), which indicate that maybe both of them are rele-
vant and they describe the same effect from different sides,
for example the size of the kink pair can be influenced by
variation of local composition of atoms (a sort of clusters
along the Peierls valley). The recently developed model for
solute strengthening of random FCC alloys [36] could be
such an alternative to the models of the local barriers and the
Peierls barriers, but the attempt to apply this solute strength-
ening model to the thermally activated plastic deformation of
the CG CoCrFeNiMn [10] has shown that the predictions of
the model are not able at the moment correlate to experi-
mental results sufficiently good (for example, values of the
activation volume from theory and experiment differed sev-
eral times), so the model should be improved to use it for
describing the thermally activated plastic deformation of the
high entropy alloys.
Concerning the relevance of the Peierls relief model in
NC state of the CoCrFeNiMn high entropy alloy, the ther-
mal activation analysis gives the value of the Peierls stress
of 458 MPa (Table 1), which is much higher than in CG
state, although the height of the Peierls barrier should not
depend on grain size. And like in case of CG state, this value
is much higher than that estimated from the single crystal
modelling [20], meaning that thermally activated motions of
dislocations over the Peierls barriers inside the grains cannot
control the plastic deformation. On the other hand, for the
NC state the estimation of the distance between the local
clusters to be 7b by means of the barrier model looks too
small: it is difficult to imagine the two clusters with a curved
dislocation segment between them at the area of seven inter-
atomic distances. Moreover, this result would mean that the
distance between the clusters in the NC state is much small-
er than in CG state, which has no relevant explanation. Al-
ternatively, the commonly accepted viewpoint in literature
[24] is that in NC materilas the process of plastic defor-
mation is not controlled by motion of dislocations inside the
grains, but by the nucleation of dislocations at the grain
boundaries. As these dependences of the flow stress, strain
rate sensitivity and activation volume of the NC
CoCrFeNiMn are very similar to that of the CG state, this
indicates similar processes to occur, but with much higher
barriers for the thermally activated plastic deformation. In-
deed, such high barriers may be represented by the grain
boundaries of the NC state. Then the model of local barriers
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1251
A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, and M.J. Zehetbauer
probably concerns the dislocation line, which had been al-
ready nucleated at the grain boundary, but pinned there at
several points (probably at ledges). Under applying stress,
these dislocation segments will bow out, and the plastic de-
formation is controlled by thermally activated tearing-off
the bowed dislocation segment from the pinning ledges
within the grain boundary, followed by subsequent free mo-
tion of dislocation through the grain. During the latter, the
local barrier model (Table 1) gives the stresses and energy
parameters of thermally activated transition of dislocation to
the grain as well as the estimate of average distance between
the ledges at the grain boundary. As well as the model of
Peierls barrier can describe the transition of dislocation from
grain boundary to the neighboring Peierls valley and Table 1
gives the microscopic parameters of this process. The com-
puter simulations of the NC materials [24] confirm the pos-
sibility of dislocation nucleation at grain boundaries.
Conclusions
The process of plastic deformation of the NC and CG
CoCrFeNiMn high entropy alloy has been studied in a wide
range of low temperatures. NC CoCrFeNiMn demonstrates
exceptionally high strength (especially for fcc material),
which achieves 3 GPa at 4.2 K, while maintaining reason-
able plasticity even at cryogenic temperatures. The yield
stress and strain rate sensitivity of flow stress have been
registered at temperatures 4.2–345 K. Values of the activa-
tion volume of the process of plastic deformation have
been evaluated from the strain rate sensitivity. Experimen-
tally measured temperature dependences of the flow stress
and strain rate sensitivity in a wide range of low tempera-
tures indicate thermally activated plasticity of both the CG
and the NC CoCrFeNiMn high entropy alloy. Thermal
activation analysis for the CG CoCrFeNiMn has shown
that plastic deformation most probably is controlled by
thermally activated motion of dislocation in grains over the
Peierls potential relief. The thermally activated process in
the nanocrystalline material can be interpreted as the gen-
eration of dislocation from grain boundary and the transi-
tion to the grain interior. Microscopic parameters of dislo-
cation interaction with the barriers for thermally activated
motion are estimated for CG and NC structural states of
the CoCrFeNiMn high entropy alloy.
The authors have pleasure to dedicate this publication
to the 80th anniversary of Prof. V.D. Natsik and express
gratitude for interest to the work and useful discussions.
_______
1. W. Yeh, S.K. Chen, S.J. Lin, J.Y. Gan, T.S. Chin, T.T. Shun,
C.H. Tsau, and S.Y. Chang, Adv. Eng. Mater. 6, 299 (2004).
2. B. Cantor, I.T.H. Chang, P. Knight, and A.J.B. Vincent,
Mater. Sci. Eng. A 375, 213 (2004).
3. B. Gludovatz, A. Hohenwarter, D. Catoor, E.H. Chang, E.P.
George, and R.O. Ritchie, Science 345, 1153 (2014).
4. Y. Zhang, T.T. Zuo, Z. Tang, M.C. Gao, K.A. Dahmen, P.K.
Liaw, and Z.P. Lu, Progr. Mater. Sci. 61, 1 (2014).
5. A. Gali and E.P. George, Intermetallics 39, 74 (2013).
6. F. Otto, A. Dlouhy, Ch. Somsen, H. Bei, G. Eggeler, and
E.P. George, Acta Mater. 61, 5743 (2013).
7. Е.D. Tabachnikova, А.V. Podolskiy, M.O. Laktionova, N.A.
Bereznaia, M.A. Tikhonovsky, and A.S. Tortika, J. Alloys
Comp. 698, 501 (2017).
8. Z. Wu, Y. Gao, and H. Bei, Acta Mater. 120, 108 (2016).
9. S.I. Hong, J. Moon, S.K. Hong, and H.S. Kim, Mater. Sci.
Eng. A 682, 569 (2017).
10. G. Laplanche, J. Bonneville, C. Varvenne, W.A. Curtin, and
E.P. George, Acta Mater. 143, 257 (2018).
11. B. Schuh, F. Mendez-Martin, B. Völker, E.P. George,
H. Clemens, R. Pippan, and A. Hohenwarter, Acta Mater. 96,
258 (2015).
12. A.V. Podolskiy, E.D. Tabachnikova, S. Maier, M.J.
Zehetbauer, C. Rentenberger, B. Joni, M.A. Tikhonovsky,
A. Tortika, and E. Schafler, Mater. Design (2018), in
submission.
13. J.P. Hirth and J. Lothe, Theory of Dislocations, McGraw-
Hill, New York (1968).
14. A. Evans and R. Rawlings, Phys. Status Solidi 34, 9 (1969).
15. V.V. Pustovalov, Fiz. Nizk. Temp. 34, 871 (2008) [Low Temp.
Phys. 34, 683 (2008)].
16. N.D. Stepanov, D.G. Shaysultanov, G.A. Salishchev, M.A.
Tikhonovsky, E.E. Oleynik, A.S. Tortika, and O.N. Senkov,
J. Alloys Comp. 628, 170 (2015).
17. E.D. Tabachnikova, A.V. Podolskiy, S.N. Smirnov, I.A.
Psaruk, V.Z. Bengus, H. Li, L. Li, H. Chu, and P.K. Liao,
Fiz. Nizk. Temp. 380, 301 (2012) [Low Temp. Phys. 38, 239
(2012)].
18. G. Laplanche, A. Kostka, O.M. Horst, G. Eggeler, and E.P.
George, Acta Mater. 118, 152 (2016).
19. N. Stepanov, M. Tikhonovsky, N. Yurchenko, D. Zyabkin,
M. Klimova, S. Zherebtsov, A. Efimov, and G. Salishchev,
Intermetallics 59, 8 (2015).
20. L. Patriarca A. Ojha, H. Sehitoglu, and Y.I. Chumlyakov,
Scripta Mater. 112, 54 (2016).
21. H. Conrad and W. Hayes, Amer. Soc. Metals 56, 249 (1963).
22. A.V. Podolskiy, E.D. Tabachnikova, V.V. Voloschuk, V.F.
Gorban, and S.A. Firstov, Mat. Sci. Eng. A 710, 136 (2018).
23. H. Li, F. Ebrahimi, H. Choo, and P.K. Liaw, J. Mater. Sci.
41, 7636 (2006).
24. M.A. Meyers, A. Mishra, and D.J. Benson, Progr. Mater.
Sci. 51, 427 (2006).
25. A. Seeger, Z. Metallk. 72, 369 (1981).
26. B. Schwarz and R. Labusch, J. Appl. Phys. 49, 5174 (1978).
27. J. Friedel, Dislocations, London, Pergamon (1964).
28. U.F. Kocks, A.S. Argon, and M.F. Ashby, Progr. Mater. Sci.
19, 1 (1975).
29. V.N. Kovaleva, V.A. Moskalenko, and V.D. Natsik, Philos.
Mag. A 70, 423 (1994).
30. E.D. Tabachnikova, A.V. Podolskiy, S.N. Smirnov, I.A.
Psaruk, and P.K. Liao, Fiz. Nizk. Temp. 40, 1419 (2014)
[Low Temp. Phys. 40, 1104 (2014)].
1252 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
https://www.diva-portal.org/smash/get/
https://doi.org/10.1126/science.1254581
https://doi.org/10.1016/j.pmatsci.2013.10.001
https://doi.org/10.1016/j.intermet.2013.03.018
https://www.sciencedirect.com/journal/acta-materialia/.../61/
https://www.tib.eu/.../tema%3ATEMA20170124936/Mechan.
https://www.tib.eu/.../tema%3ATEMA20170124936/Mechan.
https://doi.org/10.1016/j.actamat.2016.08.047
https://doi.org/10.1016/j.msea.2016.11.078
https://doi.org/10.1016/j.msea.2016.11.078
https://doi.org/10.1016/j.actamat.2017.10.014
https://doi.org/10.1002/pssb.19690340102
https://doi.org/10.1063/1.2973710
https://doi.org/10.1063/1.2973710
https://doi.org/10.1063/1.3693584
https://doi.org/10.1016/j.actamat.2016.07.038
https://doi.org/10.1016/j.intermet.2014.12.004
Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy
31. B. Gludovatz, E.P. George, and R.O. Ritchie, JOM 67, 2262
(2015).
32. A. Seeger, Mater. Sci. Eng. A 370, 50 (2004).
33. H. Lim, C.C. Battaile, J.D. Carroll, B.L. Boyce, and C.R.
Weinberger, J. Mech. Phys. Sol. 74, 80 (2015).
34. A. Seeger, J. Phys. Colloq. 42(C5), 201 (1981).
35. E.J. Pickering, H.J. Stone, and N.G. Jones, Mater. Sci. Eng.
A 645, 65 (2015).
36. G. Leyson, L. Hector, and W. Curtin, Acta Mater. 60, 3873
(2012).
___________________________
Термоактивована деформація нанокристалічного
та крупнозернистого високоентропійного сплаву
CoCrFeNiMn у діапазоні температур 4,2–350 К
А.В. Подольський, Е. Шафлер, О.Д. Табачнікова,
М.А. Тихоновський, M.J. Zehetbauer
Механічні властивості нанокристалічного (середній розмір
зерен ~ 60 нм) та крупнозернистого (середній розмір зерен
~ 4 мкм) високоентропійного сплаву CoCrFeNiMn вивчались
шляхом одноосного стискання в інтервалі температур
4,2–350 К. Температурна залежність межі плинноcті, напру-
ження течії та швидкісної чутливості деформуючого напру-
ження виміряно та проаналізовано в рамках двох термоактива-
ційних моделей: моделі взаємодії дислокацій з локальними
бар’єрами та моделі Пайєрлса щодо утворення подвійних пере-
гинів. Визначено мікроскопічні параметри взаємодії дислокацій
з бар’єрами при термоактивованому русі та обговорюються
низькотемпературні механізми, які контролюють пластичну
деформацію.
Ключові слова: високоентропійні сплави, нанокристалічні
метали, низькі температури, дислокації, термоактиваційний
аналіз.
Термоактивированная деформация
нанокристаллического и крупнозернистого
высокоэнтропийного сплава CoCrFeNiMn в
диапазоне температур 4,2–350 К
А.В. Подольский, Е. Шафлер, Е.Д. Табачникова,
М.А. Тихоновский, M.J. Zehetbauer
Механические свойства нанокристаллического (средний
размер зерен ~ 60 нм) и крупнозернистого (средний размер
зерен ~ 4 мкм) высокоэнтропийного сплава CoCrFeNiMn
изучались путем одноосного сжатия в интервале темпера-
тур 4,2–350 К. Температурная зависимость предела теку-
чеcти, напряжения течения и скоростной чувствительности
деформирующего напряжения измерены и проанализирова-
ны в рамках двух термоактивационных моделей: модели
взаимодействия дислокаций с локальными барьерами и
модели Пайерлса образования двойных перегибов. Опреде-
лены микроскопические параметры взаимодействия дисло-
каций с барьерами при термоактивированном движении и
обсуждаются низкотемпературные механизмы, которые
контролируют пластическую деформацию.
Ключевые слова: высокоэнтропийные сплавы, нанокристал-
лические металлы, низкие температуры, дислокации, термо-
активационный анализ.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1253
1. Introduction
2. Materials and methods
3. Experimental results
4. Analysis and discussion
4.1. Local barriers
4.2. Peierls barriers
4.3. Discussion of the thermally activated plastic deformation
Conclusions
|
| id | nasplib_isofts_kiev_ua-123456789-176251 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0132-6414 |
| language | English |
| last_indexed | 2025-12-07T15:52:10Z |
| publishDate | 2018 |
| publisher | Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| record_format | dspace |
| spelling | Podolskiy, A.V. Schafler, E. Tabachnikova, E.D. Tikhonovsky, M.A. Zehetbauer, M.J. 2021-02-04T07:52:08Z 2021-02-04T07:52:08Z 2018 Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K / A.V. Podolskiy, E. Schafler, E.D. Tabachnikova, M.A. Tikhonovsky, M.J. Zehetbauer // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1245-1253. — Бібліогр.: 36 назв. — англ. 0132-6414 https://nasplib.isofts.kiev.ua/handle/123456789/176251 Mechanical properties of a nanocrystalline (~ 60 nm) and a coarse grained (grain sizes ~ 4 µm) CoCrFeNiMn high entropy alloys were studied in uniaxial compression in the temperature range 4.2–350 K. Temperature dependences of yield strength, flow stress and strain rate sensitivity have been registered and analyzed in the framework of two thermal activation deformation models, that of thermal activation of local barrier overcoming, and that of Peierls valley double kink formation. Microscopic parameters of dislocation interaction with the barriers for thermally activated motion are estimated and low temperature deformation mechanisms are discussed. Механічні властивості нанокристалічного (середній розмір зерен ~ 60 нм) та крупнозернистого (середній розмір зерен ~ 4 мкм) високоентропійного сплаву CoCrFeNiMn вивчались шляхом одноосного стискання в інтервалі температур 4,2–350 К. Температурна залежність межі плинноcті, напруження течії та швидкісної чутливості деформуючого напруження виміряно та проаналізовано в рамках двох термоактиваційних моделей: моделі взаємодії дислокацій з локальними бар’єрами та моделі Пайєрлса щодо утворення подвійних перегинів. Визначено мікроскопічні параметри взаємодії дислокацій з бар’єрами при термоактивованому русі та обговорюються низькотемпературні механізми, які контролюють пластичну деформацію. Механические свойства нанокристаллического (средний размер зерен ~ 60 нм) и крупнозернистого (средний размер зерен ~ 4 мкм) высокоэнтропийного сплава CoCrFeNiMn изучались путем одноосного сжатия в интервале температур 4,2–350 К. Температурная зависимость предела текучеcти, напряжения течения и скоростной чувствительности деформирующего напряжения измерены и проанализированы в рамках двух термоактивационных моделей: модели взаимодействия дислокаций с локальными барьерами и модели Пайерлса образования двойных перегибов. Определены микроскопические параметры взаимодействия дислокаций с барьерами при термоактивированном движении и обсуждаются низкотемпературные механизмы, которые контролируют пластическую деформацию. The authors have pleasure to dedicate this publication to the 80th anniversary of Prof. V.D. Natsik and express gratitude for interest to the work and useful discussions. en Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України Физика низких температур Низькотемпературна фізика пластичності та міцності Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K Термоактивована деформація нанокристалічного та крупнозернистого високоентропійного сплаву CoCrFeNiMn у діапазоні температур 4,2–350 К Термоактивированная деформация нанокристаллического и крупнозернистого высокоэнтропийного сплава CoCrFeNiMn в диапазоне температур 4,2–350 К Article published earlier |
| spellingShingle | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K Podolskiy, A.V. Schafler, E. Tabachnikova, E.D. Tikhonovsky, M.A. Zehetbauer, M.J. Низькотемпературна фізика пластичності та міцності |
| title | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K |
| title_alt | Термоактивована деформація нанокристалічного та крупнозернистого високоентропійного сплаву CoCrFeNiMn у діапазоні температур 4,2–350 К Термоактивированная деформация нанокристаллического и крупнозернистого высокоэнтропийного сплава CoCrFeNiMn в диапазоне температур 4,2–350 К |
| title_full | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K |
| title_fullStr | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K |
| title_full_unstemmed | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K |
| title_short | Thermally activated deformation of nanocrystalline and coarse grained CoCrFeNiMn high entropy alloy in the temperature range 4.2–350 K |
| title_sort | thermally activated deformation of nanocrystalline and coarse grained cocrfenimn high entropy alloy in the temperature range 4.2–350 k |
| topic | Низькотемпературна фізика пластичності та міцності |
| topic_facet | Низькотемпературна фізика пластичності та міцності |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/176251 |
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