Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding
Fine grained magnesium alloy AZ31 sheets were submitted to the accumulative roll bonding (ARB). After ARB, the microstructure of samples was refined, and the sheets exhibited pronounced texture. The amplitudedependent internal friction (ADIF) was measured at room temperature. Microstructure changes...
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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: | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding / Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik, J. Džugan, K. Halmešová // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1233-1240. — Бібліогр.: 41 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859793921999110144 |
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| author | Trojanová, Z. Drozd, Z. Lukáč, P. Minárik, P. Džugan, J. Halmešová, K. |
| author_facet | Trojanová, Z. Drozd, Z. Lukáč, P. Minárik, P. Džugan, J. Halmešová, K. |
| citation_txt | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding / Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik, J. Džugan, K. Halmešová // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1233-1240. — Бібліогр.: 41 назв. — англ. |
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| container_title | Физика низких температур |
| description | Fine grained magnesium alloy AZ31 sheets were submitted to the accumulative roll bonding (ARB). After
ARB, the microstructure of samples was refined, and the sheets exhibited pronounced texture. The amplitudedependent internal friction (ADIF) was measured at room temperature. Microstructure changes as the increased
dislocation density, grain size refinement, twins, and texture influenced the ADIF. A significant anisotropy of the
properties was observed. Experimental results are discussed on the base of physical mechanisms responsible for
internal friction.
Дрібнозернисті листи магнієвих сплавів AZ31
були піддані накопичувальному з’єднанню вальцюванням (ARB). Після застосування ARB мікроструктура зразків ставала більш фрагментованою,
і в листах спостерігалась яскраво виражена текстура. Амплітудно-залежне внутрішнє тертя (АЗВТ)
вимірювали при кімнатній температурі. Зміни мікроструктури, такі як збільшення щільності дислокацій, зменшення розміру зерна, поява двійників та
текстури, приводили до змін АЗВТ. Спостерігалась
суттєва анізотропія вивчених властивостей. Експериментальні результати обговорюються на базі відомих фізичних механізмів, що відповідають за
внутрішнє тертя.
Мелкозернистые листы магниевых сплавов
AZ31 были подвергнуты накопительному соединению прокаткой (ARB). После применения ARB
микроструктура образцов становилась более фрагментированной, и в листах наблюдалась ярко выраженная текстура. Амплитудно-зависимое внутреннее трение (АЗВТ) измеряли при комнатной
температуре. Изменения микроструктуры, такие
как увеличение плотности дислокаций, уменьшение размера зерна, появление двойников и текстуры, приводили к изменениям АЗВТ. Наблюдалась
существенная анизотропия изученных свойств.
Экспериментальные результаты обсуждаются на
основе известных физических механизмов, отвечающих за внутреннее трение.
|
| first_indexed | 2025-12-02T12:25:03Z |
| format | Article |
| fulltext |
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9, pp. 1233–1240
Amplitude-dependent internal friction in AZ31 alloy
sheets submitted to accumulative roll bonding
Z. Trojanová, Z. Drozd, P. Lukáč, and P. Minárik
Faculty of Mathematics and Physics, Charles University, Prague, Ke Karlovu 3, 121 16 Praha 2, Czech Republic
E-mail: ztrojan@met.mff.cuni.cz
J. Džugan and K. Halmešová
Comtes FHT, Průmyslová 996, 334 41 Dobřany, Czech Republic
Received March 19, 2018, published online July 26, 2018
Fine grained magnesium alloy AZ31 sheets were submitted to the accumulative roll bonding (ARB). After
ARB, the microstructure of samples was refined, and the sheets exhibited pronounced texture. The amplitude-
dependent internal friction (ADIF) was measured at room temperature. Microstructure changes as the increased
dislocation density, grain size refinement, twins, and texture influenced the ADIF. A significant anisotropy of the
properties was observed. Experimental results are discussed on the base of physical mechanisms responsible for
internal friction.
Keywords: magnesium alloy, accumulative roll bonding, internal friction, dislocations, twinning, texture.
1. Introduction
Magnesium alloys with their high specific strength and
low weight are used as structural materials in different ap-
plications. They have suitable mechanical and excellent
damping [1]. Magnesium wrought alloys, such as for in-
stant AZ31, are needed for applications where their weight
is important. It is well known that the mechanical proper-
ties of Mg alloys depend very sensitive on their micro-
structure [2]. Grain refinement is an effective way leading
to a higher strength and ductility. Different procedures
have been used for the grain refinement. Thus, extrusion of
samples causes grain refinement and may produce texture
and then anisotropy of mechanical properties [3].
In recent years, methods of severe plastic deformation
(SPD) have attracted interest of many researchers investi-
gating also properties of magnesium alloys [4]. Very often,
equal channel angular pressing (ECAP) and high pressure
torsion (HPT) are used to influence the microstructure.
Rarely, accumulative roll bonding technique is used. In this
processing, a sheet is rolled to 50% thickness, cut to two
halves that are connected and then again rolled [5]. In con-
trast to extrusion and/or rolling, the ECAP and HPT proc-
essing affect significantly the microstructure of Mg; not only
grains are refinement but also the total dislocation change
depending on conditions of processing. Many papers de-
scribing the effect of ECAP on the mechanical properties
of AZ31 magnesium alloys have been presented [6–8]. On
the other hand, very few experiments on the influence of
ARB on properties of AZ31 were conducted. It is important
to mention that also twins and texture changes can be in-
duced in samples undergone to SPD processing [9–11].
Microstructure changes have a significant influence on
internal friction. Damping of materials depends on micro-
structure, stress, temperature or frequency. The internal
friction is a result of motion of structural defects such as
point defects, dislocations, twins or grain boundaries. Con-
versely internal friction measurements can be used to study
changes in the microstructure or the density and mobility
of structural defects.
The purpose of the present study is to investigate the ef-
fect of microstructure modifications, introduced by the ac-
cumulative roll bonding into AZ31 alloy sheets, on strain
amplitude-dependent internal friction with the focus on the
mechanisms which are responsible for these changes.
2. Experimental procedure
Commercially available sheets from a magnesium alloy
AZ31 were used in this study. The chemical composition
(in wt%) of the alloy is introduced in Table 1.
Table 1. Chemical composition of the alloy studied (in wt.%)
Material Al Zn Mn Si Fe Ce Mg
AZ31_RS 3.2 1.3 0.4 0.015 0.03 0.06 Bal.
© Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik, J. Džugan, and K. Halmešová, 2018
mailto:ztrojan@met.mff.cuni.cz
Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik, J. Džugan, and K. Halmešová
The accumulative roll bonding of AZ31 magnesium al-
loy was performed using four high-rolling mill configura-
tion. Two strips with initial thickness of 2 mm were de-
greased with acetone, then wire brushed and fastened along
one side. These steps ensured conditions to achieve good-
quality joint. Prior to rolling the sheets were annealed at
400 °C for 15 min. At lower temperatures, material failed
to bond. The rolling speed was 0.4 mm/s and the ARB ex-
periments were carried out without a lubricant. The rolling
reduction was 50% in the thickness per each rolling cycle.
Two passes through the rolling mill were successfully real-
ized. Samples for the internal friction measurements were
cut from the sheets so that the longest axis of the sample
was either parallel (L-samples) or transversal (T-samples)
to the rolling direction. Samples from the ARB sheets will
be depicted hereafter as ARB_0 (original sheet), ARB_1
(after the first ARB pass) and ARB_2 (after the two ARB
passes).
Microstructure of samples was studied using a light mi-
croscope Neophot and scanning electron microscope (SEM)
Tescan. The texture analysis was performed in the ZEISS
Auriga Compact microscope equipped with EDAX EBSD
camera and special software, utilized for EBSD observa-
tions.
Internal friction measurements were carried out on bend-
ing beams (86 mm long, 10 mm wide and 2.3 mm thick) at
room temperature. The internal friction was obtained by
the measurement of the logarithmic decrement of free de-
caying bending beam vibrations in the resonant frequency.
Details of the apparatus were described in [12]. The typical
resonant frequency exhibited about 22 Hz. The logarithmic
decrement, δ, was estimated directly from the definition
according the exponential law
0 exp ( /( ) )pA t A t= −δ τ , (1)
where A0 is the required amplitude, t is the time and τp is
the period of vibrations. The signal amplitude is propor-
tional to the strain amplitude, ε. The amplitude depend-
ences of the decrement were measured from the maximum
amplitude towards to the lower amplitudes.
3. Results and discussion
3.1. Microstructure of sheets
Light micrograph of the as-received L-sample, taken
from the sheet surface, is reported in Fig. 1. Dark particles
are typical features of the microstructure. Bigger particles
are elongated in the rolling direction; smaller particles
decorate the grain boundaries. Chemical analysis of parti-
cles showed that these particles containing Al and Mn are
very probably Al8Mn5 precipitates which were described
in the literature by several authors [13,14]. No precipitates
Mg17Al12 typical for Mg–Al–Zn alloys were observed in
the microstructure. This was probably due to a higher
processing temperature during the rolling process (400 °C).
Traces of the bonding between sheets are visible in Fig. 2
indicated by the arrows. This bonding emerged strong
enough, no delamination of samples was observed even
during plastic deformation at elevated temperatures [15].
Good bonding may be achieved as a result of dynamic re-
crystallization (DRX) [16].
The effect of the ARB on the sheet microstructure is
shown in Fig. 3 by the means of EBSD. The micrograph of
the as-received material is shown in Fig. 3(a). Large grains
of size ~100 µm are surrounded by smaller ones; many
twins are typical feature of the microstructure. The first
rolling pass refined the grains. The grain size decreased ten
times down to ~10 µm as it is obvious from Fig. 3(b). The
highest area fraction had grains of 4–5 µm in diameter. On
the other hand, bigger grains 40–60 µm remained in the
microstructure. The fraction of high-angle grain boundaries
was particularly high ~0.8. Some bigger grains exhibit
changing colour, which indicates the high lattice distortion
due to high deformation energy stored in the grains. The
microstructure of the ARB_2 is presented in Fig. 3(c). The
Fig. 1. Microstructure of ARB_0 sample, taken from the sheet
surface.
Fig. 2. SEM micrograph of the ARB_2 sample showing joining
of sheets indicated by arrows.
1234 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding
microstructure is more homogeneous, the bigger grains
(> 30 µm) vanished. The mean grain size again decreased
down to ~7.6 µm in diameter, but the highest area fraction
was still represented by grains of 4–5 µm.
Revealing red colour in the pictures presented in
Figs. 3(a)–(c) indicates existing texture of rolled sheets.
EBSD pole figures are shown in Fig. 4. The texture can be
characterized as a fibre texture with the c-axis perpendicu-
lar to the sheet surface. Crystallographic texture was im-
proved during the ARB process in the first and second roll-
ing pass. The distribution of basal poles shows a basal pole
tilted away from the normal direction towards the trans-
verse direction, as can be seen in Fig. 4.
3.2. Amplitude-dependent internal friction
The logarithmic decrement, δ, is plotted against the strain
amplitude, ε, Fig. 5 for L-sample and T-sample. The depend-
ences can be divided as obvious into two regions: an ampli-
Fig. 3. (Color online) EBSD microstructure of samples ARB_0 (a), ARB_1 (b) and ARB_2 (c).
(a) (b) (c)
300 µm 50 µm 100 µm
0001 11 20
10 10
Fig. 4. Pole figures of ARB_0 sample (a), ARB_1 sample (b) and ARB-2 sample (c).
(a) (b)
0001 1010 0001 1010
(c)
RD
0001 1010
A
6
5
4
3
2
1
Fig. 5. Amplitude dependences of decrement measured for L-sample
and T-sample.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1235
Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik, J. Džugan, and K. Halmešová
tude-independent (or slightly depending on strain ampli-
tude) part, δ0, of the decrement found for smaller strain
amplitudes and the region of higher amplitudes where dec-
rement, δ(ε), rapidly increases with strain amplitude, i.e., δ
can be expressed as
δ = δ0 + δH(ε). (2)
From Fig. 5, it is obvious that the decrement values es-
timated in both regions are higher for T-sample comparing
with the L-sample. Such planar plastic anisotropy of sam-
ples deformed in L and T direction is known and it was
several times described in the literature [17–21]. Such pla-
nar anisotropy is not limited only on plastic properties, but
it was also found for Young’s modulus and the thermal
expansion coefficient [22,23]. Similar results were obtain-
ed for AZ31 alloy sheet in a different apparatus as it was
shown in [24]. The difference between both sample orien-
tations was more significant, very probably due to a bigger
maximum strain amplitude. The ARB process influences
the decrement in both regions. It is demonstrated in Fig. 6
for L-samples and in Fig. 7 for T-samples. The shape of
curves changed, and curves were shifted to higher values
of the decrement especially for smaller amplitudes. The
decrement component, δ0, estimated at an amplitude
ε = 5·10–6 was plotted as a function of rolling passes for
both sample orientations (see Fig. 8). It can be seen that δ0
component increases with increasing number of passes.
This increase is more distinctive for L-samples where δ0
increased approximately two times. On the other hand, the
increase of δ0 is only moderate.
Rolled sheets after the ARB process exhibit also a sig-
nificant internal stress. Samples of both orientations were
heated in a dilatometer and the thermal expansion was
measured. After one cycle from room temperature up to
400 °C with a heating rate of 0.9 K/min permanent short-
ening of samples was estimated. This relative shortening in
percent is presented in Fig. 9 for samples of both orienta-
tions. While the shortening of T-samples was more or less
the same, only slightly dependent on the number of passes;
shortening of L-sample increases rapidly with increasing
number of rolling passes. This result indicates that the in-
ternal stresses are higher in samples with the longest axis
parallel to the rolling direction.
While internal friction in the amplitude-independent part
may be done by several mechanisms (dislocation internal
Fig. 6. (Color online) Amplitude dependences of decrement mea-
sured for L-sample after ARB rolling.
Fig. 7. (Color online) Amplitude dependences of decrement mea-
sured for T-sample after ARB rolling.
Fig. 8. Amplitude component, δ0, of decrement estimated in L-
and T-samples after ARB passes.
Fig. 9. Permanent strain depending on number of ARB passes
measured after thermal cycle of L- and T-sample.
1236 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding
friction, grain boundary sliding, thermoelastic effect), the
amplitude-dependent part is only due to presence of dislo-
cation in the material. The thermoelastic loss may be ob-
served in the bending reed or a thin beam during vibrations
at low frequencies [25,26]. Damping can occur by heat
flow from the hotter (compressed) parts to the cooler (ex-
tended) parts of the sample. For the thermoelastic internal
friction following relationship may be written
0
2 2
0
TE T
f f
f f
δ =∆
+
, (3)
where ∆T is the relaxation strength, f is the measuring fre-
quency and f0 is the frequency at which the maximum of
the thermoelastic damping can be observed. Both quanti-
ties f0 and ∆T depend on thermal properties of the sample
material and its geometry:
2
0 / 2 m pf d C=π ρ , 2 /T u m pE T C∆ =α ρ , (4)
where κ is the thermal conductivity, ρm is the material den-
sity, α is the thermal expansion coefficient, T is the absolute
temperature, d is the sample thickness, EU is unrelaxed
Young’s modulus, and Cp is the specific heat at constant
pressure. Taking for κ = 76 W/(m·K), d = 2.3 mm, ρm =
= 1738 kg/m3, Cp = 1010 J/(kg·K), EU = 44 GPa and α =
= 26.5·10–6 K–1 [27], we obtain at room temperature for
f0 = 12.85 Hz and ∆T = 0.0052. Although the thermal pro-
perties depend slightly on the sample orientation and number
of passes, it is reasonable to consider that the contribution
to the internal friction value coming from the thermoelastic
effect will be for all samples approximately the same of
δTE = 0.0023.
In the vibrating string model the dislocation amplitude-
independent decrement component can be written as [28,29]
4
0 2
L
B
E b
Ω ρ ω
δ =
, (5)
where Ω is an orientation factor, ρ is the dislocation den-
sity, B is the coefficient of dislocation friction and EL is the
tension in a dislocation line, b is the magnitude of the Bur-
gers vector of dislocations and ℓ is length of shorter dislo-
cation segments between weak pinning points which may
be point defects or their small clusters.
The breakaway of dislocations from the weak pinning
points may occur when the force impacting on two adja-
cent dislocation segments with the length ℓ1 and ℓ2 exceed
the Cottrell energy EC/b. Therefore, the critical stress, σc,
for breakaway is given in the single pin approximation at
zero temperature as 1 2( ) / 2 /| |c Cb E bσ + = . The ampli-
tude-dependent internal friction was calculated by Granato
and Lűcke [30] under simplified conditions that disloca-
tions in a crystal form a network with the same loop length
of LN. Shorter dislocation segments pinned by the weak
pinning points are statistically distributed along the longer
dislocation segments. At temperatures higher than 0 K, the
amplitude dependence of the logarithmic decrement may
be expressed in the low-frequency limit as an exponential
function in the following form:
11/21/22 3 2 20 0
3
0 0
3 4 1 exp
6 2 3
N
H
L U U GkT
U U G kT
ρ π σ δ = − ω σ
ν
,
(6)
where G is the shear modulus, σ is the amplitude of the
applied stress and ω its angular frequency, ν is the attack
frequency. U0 is the activation energy of overcoming pin-
ning centres, k is the Boltzmann constant and T is the abso-
lute temperature. In the formula (6), the δH component is
an exponential function of the applied stress amplitude si-
milar to the original formula by Granato and Lücke [28,29].
Because the stress and strain amplitudes are related by the
Hooke’s law, Eq. (6) may be rewritten as
( )0 1 2 exp /C Cδ = δ + ε − ε , (7)
where ε = σ/E, C1 and C2 are parameters depending on
dislocation density and length of the shorter and longer
dislocation segments. Because all experiments were per-
formed at room temperature, the activation energy may be
considered in the first approximation as a constant.
The amplitude dependences of the logarithmic decre-
ment were fitted to Eq. (7) as it is shown in Fig. 10. The cor-
relation to the experimental points is good, R2 = 0.998 for
L-sample and R2 = 0.992 for T-sample. Parameter C1 was
estimated C1(L) = 18.9 and C1(T) = 35.1. Note that the
vibrating string model and dislocation dynamics were con-
structed for single crystals of “pure” metals. The model is
highly idealized and it does not take into account interac-
tions between dislocation loops, the fact that the line en-
ergy of dislocations depends on the dislocation type and
may be affected by anisotropy [31]. In real materials (al-
loys), the comparison of experimental results with the the-
Fig. 10. (Color online) GL fit for ARB_0 samples in both orienta-
tions.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1237
Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik, J. Džugan, and K. Halmešová
oretical model may be performed only qualitatively. Be-
cause the C1 parameter ∼ ℓ3/2, the higher value of the C1
parameter in the T-sample indicates a higher length of dis-
location segments operating in the slip plane after break-
away of shorter segments from the weak pinning points. It
means that the area swept by dislocation segments is big-
ger in the T direction.
Many pre-existing twins in the material are documented
in Fig. 2(a). These twins contribute to the amplitude-in-
dependent component of the logarithmic decrement, δ0,
very probably in both sample orientations. The idea of en-
hanced internal friction due to presence of twins in Mg and
Mg alloys was pronounced by several authors [32–34].
They consider that the twin boundary is movable under
alternating strain and it can either shrink or extent the twin
width even at stresses much lower than the nucleation
stress [32,33]. Watanabe et al. [34] studied the influence of
deformation twins on internal friction in extruded pure Mg.
They found that pre-deformation increased internal friction
due to new twins which were formed during compressive
deformation of the textured samples. Rolled sheets studied
exhibit texture where basal planes are parallel to the sheet
surface. The force causing the sheet vibrations impacts in
the perpendicular direction to the sheet surface. In such
situation, a〈 〉 dislocations are movable in (0001) basal and
{ }1120 prismatic planes. On the other hand, basal poles are
split into transversal direction (see Figs. 4) in all samples.
The splitting of basal poles decreases with increasing num-
ber of passes. Such type of the texture with the angular
distribution of the basal poles broader in the transversal
direction is favorable for mechanical twinning. Tensile ex-
periments of samples with the stress axis in the rolling direc-
tion and transversal direction showed that the yield stress in
the transversal direction is much lower than the yield stress
found for rolling direction, i.e., YS(RD) = 162 MPa and
YS(TD) = 85 MPa [15]. This planar plastic anisotropy was
explained by the different deformation mechanisms occur-
ring during plastic straining of both samples. While defor-
mation process in the rolling direction is realized mainly
by the dislocation motion, mechanical twinning may be
consider as the significant deformation mechanism at the
onset of deformation in the transversal direction. It is done
by the lower critical resolved stress of twinning. Because
twinning is a polar mechanism it can operate if special
geometrical conditions (texture) are fulfilled [35]. Acoustic
emission activity characterised by the count rate observed
during tensile deformation showed a higher intensity of
acoustic emission in the sample cut in the transversal direc-
tion as it is shown in Fig. 11. Note that the scale on the
count rate axis is logarithmic, thus the acoustic emission in
the T-sample is at the very beginning of deformation ap-
proximately ten times higher. It is valid for very low
strains (stresses) in the microyielding region which corre-
sponds with the region of the internal friction measure-
ments. In the bending experiment the half of the sample is
in tension while the second part of the sample is in com-
pression. Both parts of sample are divided by the neutral
plane. In the next half cycle, the situation is opposite. Taking
into account results of acoustic emission measurements,
we may consider that new { }1012 1011〈 〉 tension twins are
generated during loading in measuring apparatus [36]. In
the following half cycle detwinning takes place and these
tension twins are erased. Huang et al. and Yang et al. found
that the critical resolved stress for the twins’ formation is
really very low 2–2.8 MPa and tensile twins may be easily
formed [37,38]. Taking in the consideration that Young’s
modulus for AZ31 alloy E = 44 GPa, then such stress can
be achieved at the amplitudes of ε = (4.5−6.4)·10–5. Note
that in the samples exist appreciable residual tensile
stresses (see Fig. 9) which can add to the applied stress and
formatted the originally symmetrical tension — compres-
sion cycle into unsymmetrical.
The amplitude dependences of the logarithmic decre-
ment measured after the first and second rolling passes are
shown in Fig. 6 for L-sample and 7 for T-sample. It can be
seen that the shape of curves changed. The logarithmic
dependence of Eq. (7) is no more applicable for these
curves. In a material submitted to SPD processing, many
microstructural aspects must be taken into account. Inter-
nal friction is influenced by:
i) Decreased grain size;
ii) Increased volume of grain boundaries;
iii) Increased dislocation density;
iv) Dislocations in small angle grain boundaries;
v) Increased level of tensile residual stresses in the roll-
ing direction.
Decreasing grain size after the first and second ARB
passes is well visible in Figs. 2(b) and 2(c).
Internal friction in pure Mg and AZ31 magnesium alloy
subjected to EXECAP processing was studied by Fan and
co-workers [39,40]. They found increased internal friction
values in the strain-independent part due to abundant mo-
bile dislocations induced by the ECAP processing. How-
Fig. 11. (Color online) Acoustic emission activity measured dur-
ing tensile deformation in samples of both orientations.
1238 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding
ever, the intense tangle of dislocations and significant in-
crease of the grain boundary volume contribute to a de-
crease in strain-independent IF for ECA extruded Mg. The
GL model is applicable only for lower strain amplitudes.
Annealing at 200 and 300 °C reduced IF in the amplitude-
independent part due to a decrease of dislocation density,
while strain-dependent part is obviously increased. A high-
er dislocation density may be considered also after intense
plastic deformation due to rolling. High temperature of the
ARB process was the reason for the reconstruction of the
grain structure via operation of the rotational dynamic re-
crystallization (RDX). Increased dislocation density con-
tributes to the amplitude-independent internal friction in-
crease. However, increased dislocation density restricts the
mean free paths of dislocations and the area swept by dis-
locations after successful breakaway form the weak pin-
ning points. The EBSD analysis showed that 20 % of grain
boundaries are small angle grain boundaries formed by the
edge dislocations. These dislocations may also contribute
to the internal friction.
Trojanová et al. [41] studied internal friction in the
microcrystalline Mg and Mg reinforced with the ceramic
nanoparticles and showed that the nanoparticles were si-
tuated mainly in the grain boundaries. The amplitude-
dependent component of the decrement decreased in the
Mg + 3 vol.% n-Al2O3. Because of good bonding between
nanoparticles and Mg matrix, these nanoparticles restricted
grain boundary sliding. In a material with the grain size in
the µm region, grain boundary sliding may be not exclude-
ed, and it increases the internal friction in the amplitude-
independent region. On the other hand, the influence of
twinning decreases with decreasing grain size. The stress
necessary for twin’s formation increases with the decreas-
ing grain size, as it was shown in mechanical tests [24].
The ARB process introduced into the materials (ARB_1)
and (ARB_2) new interfaces. Although the bonding at the
interface is very good (no delamination of samples was not
observed even at elevated temperatures), sliding in this in-
terface may not be excluded. The interface is parallel with
the sample axis in L-sample and perpendicular in the T-
samples. It is reasonable to expect that the influence of this
new interface will be more substantial in the L-sample.
As it was mentioned above, it is not possible to describe
the amplitude dependence of decrement by the exponential
function theoretically proposed by Granato and Lücke [30].
This is very probably due to complex character of internal
friction in a highly deformed polycrystalline material. Sev-
eral mechanisms contribute to internal friction and each of
them has its specific influence on the amplitude-independ-
ent and dependent damping.
4. Conclusions
The amplitude dependences of internal friction were
measured in AZ31 alloy sheets after accumulative roll
bonding at room temperature. Following conclusions may
be drawn from the experimental finding.
– Anelastic planar anisotropy of internal friction was
observed; the logarithmic decrement was higher in rolled
sheets cut perpendicular to the rolling direction than that in
the samples where the longer axis was parallel to the roll-
ing direction.
– Different loss mechanisms are responsible for this
anisotropy; dislocation internal friction is the main loss
mechanism in samples cut parallel with the rolling direc-
tion while in the transversal samples twin’s formation and
twin’s boundary motion contribute to the internal friction.
– Accumulative roll bonding increased internal friction;
internal friction in the highly deformed material is some
complex problem where various mechanisms (dislocation
internal friction, grain-boundary sliding, interface sliding)
contribute to internal friction.
Acknowledgments
It is a great honour for us to have opportunity to dedi-
cate this paper to Vasilii Dmitrievich Natsik, well known
physicist theoretician, on the occasion of his 80th birthday.
We wish Vasilii good health and much happiness in the
years ahead.
This study was realized with the financial support of the
Grant Agency of the Czech Republic under project 18-
07140S.
________
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Амплітудно-залежне внутрішнє тертя в листах
сплаву AZ31, підданих накопичувальному
з’єднанню вальцюванням
Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik,
J. Džugan, K. Halmešová
Дрібнозернисті листи магнієвих сплавів AZ31
були піддані накопичувальному з’єднанню валь-
цюванням (ARB). Після застосування ARB мікро-
структура зразків ставала більш фрагментованою,
і в листах спостерігалась яскраво виражена тексту-
ра. Амплітудно-залежне внутрішнє тертя (АЗВТ)
вимірювали при кімнатній температурі. Зміни мік-
роструктури, такі як збільшення щільності дисло-
кацій, зменшення розміру зерна, поява двійників та
текстури, приводили до змін АЗВТ. Спостерігалась
суттєва анізотропія вивчених властивостей. Експе-
риментальні результати обговорюються на базі ві-
домих фізичних механізмів, що відповідають за
внутрішнє тертя.
Ключові слова: сплави магнію, накопичувальне
з’єднання вальцюванням, внутрішнє тертя, дисло-
кації, двійникування, текстура.
Амплитудно-зависимое внутреннее трение
в листах сплава AZ31, подверженных
накопительному соединению прокаткой
Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik,
J. Džugan, K. Halmešová
Мелкозернистые листы магниевых сплавов
AZ31 были подвергнуты накопительному соеди-
нению прокаткой (ARB). После применения ARB
микроструктура образцов становилась более фраг-
ментированной, и в листах наблюдалась ярко вы-
раженная текстура. Амплитудно-зависимое внут-
реннее трение (АЗВТ) измеряли при комнатной
температуре. Изменения микроструктуры, такие
как увеличение плотности дислокаций, уменьше-
ние размера зерна, появление двойников и тексту-
ры, приводили к изменениям АЗВТ. Наблюдалась
существенная анизотропия изученных свойств.
Экспериментальные результаты обсуждаются на
основе известных физических механизмов, отве-
чающих за внутреннее трение.
Ключевые слова: сплавы магния, накопительное
соединение прокаткой, внутреннее трение, дисло-
кации, двойникование, текстура.
1240 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
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https://www.sciencedirect.com/science/article/pii/S092583881002325X%23!
https://www.sciencedirect.com/science/article/pii/S092583881002325X%23!
https://www.sciencedirect.com/science/article/pii/S092583881002325X%23!
https://www.sciencedirect.com/science/article/pii/S092583881002325X%23!
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https://doi.org/10.1016/j.matchar.2016.11.046
https://doi.org/10.1016/S0921-5093(01)01297-7
https://doi.org/https:/doi.org/10.1016/j.scriptamat.2004.01.013
https://doi.org/10.1016/j.jallcom.2012.09.040
https://doi.org/10.1016/j.msea.2012.07.031
https://doi.org/10.1016/j.msea.2002.12.011
1. Introduction
2. Experimental procedure
3. Results and discussion
3.1. Microstructure of sheets
3.2. Amplitude-dependent internal friction
4. Conclusions
Acknowledgments
|
| id | nasplib_isofts_kiev_ua-123456789-176249 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0132-6414 |
| language | English |
| last_indexed | 2025-12-02T12:25:03Z |
| publishDate | 2018 |
| publisher | Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| record_format | dspace |
| spelling | Trojanová, Z. Drozd, Z. Lukáč, P. Minárik, P. Džugan, J. Halmešová, K. 2021-02-04T07:51:35Z 2021-02-04T07:51:35Z 2018 Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding / Z. Trojanová, Z. Drozd, P. Lukáč, P. Minárik, J. Džugan, K. Halmešová // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1233-1240. — Бібліогр.: 41 назв. — англ. 0132-6414 https://nasplib.isofts.kiev.ua/handle/123456789/176249 Fine grained magnesium alloy AZ31 sheets were submitted to the accumulative roll bonding (ARB). After ARB, the microstructure of samples was refined, and the sheets exhibited pronounced texture. The amplitudedependent internal friction (ADIF) was measured at room temperature. Microstructure changes as the increased dislocation density, grain size refinement, twins, and texture influenced the ADIF. A significant anisotropy of the properties was observed. Experimental results are discussed on the base of physical mechanisms responsible for internal friction. Дрібнозернисті листи магнієвих сплавів AZ31 були піддані накопичувальному з’єднанню вальцюванням (ARB). Після застосування ARB мікроструктура зразків ставала більш фрагментованою, і в листах спостерігалась яскраво виражена текстура. Амплітудно-залежне внутрішнє тертя (АЗВТ) вимірювали при кімнатній температурі. Зміни мікроструктури, такі як збільшення щільності дислокацій, зменшення розміру зерна, поява двійників та текстури, приводили до змін АЗВТ. Спостерігалась суттєва анізотропія вивчених властивостей. Експериментальні результати обговорюються на базі відомих фізичних механізмів, що відповідають за внутрішнє тертя. Мелкозернистые листы магниевых сплавов AZ31 были подвергнуты накопительному соединению прокаткой (ARB). После применения ARB микроструктура образцов становилась более фрагментированной, и в листах наблюдалась ярко выраженная текстура. Амплитудно-зависимое внутреннее трение (АЗВТ) измеряли при комнатной температуре. Изменения микроструктуры, такие как увеличение плотности дислокаций, уменьшение размера зерна, появление двойников и текстуры, приводили к изменениям АЗВТ. Наблюдалась существенная анизотропия изученных свойств. Экспериментальные результаты обсуждаются на основе известных физических механизмов, отвечающих за внутреннее трение. It is a great honour for us to have opportunity to dedicate this paper to Vasilii Dmitrievich Natsik, well known physicist theoretician, on the occasion of his 80th birthday. We wish Vasilii good health and much happiness in the years ahead. This study was realized with the financial support of the Grant Agency of the Czech Republic under project 18- 07140S. en Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України Физика низких температур Низькотемпературна фізика пластичності та міцності Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding Амплітудно-залежне внутрішнє тертя в листах сплаву AZ31, підданих накопичувальному з’єднанню вальцюванням Амплитудно-зависимое внутреннее трение в листах сплава AZ31, подверженных накопительному соединению прокаткой Article published earlier |
| spellingShingle | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding Trojanová, Z. Drozd, Z. Lukáč, P. Minárik, P. Džugan, J. Halmešová, K. Низькотемпературна фізика пластичності та міцності |
| title | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding |
| title_alt | Амплітудно-залежне внутрішнє тертя в листах сплаву AZ31, підданих накопичувальному з’єднанню вальцюванням Амплитудно-зависимое внутреннее трение в листах сплава AZ31, подверженных накопительному соединению прокаткой |
| title_full | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding |
| title_fullStr | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding |
| title_full_unstemmed | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding |
| title_short | Amplitude-dependent internal friction in AZ31 alloy sheets submitted to accumulative roll bonding |
| title_sort | amplitude-dependent internal friction in az31 alloy sheets submitted to accumulative roll bonding |
| topic | Низькотемпературна фізика пластичності та міцності |
| topic_facet | Низькотемпературна фізика пластичності та міцності |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/176249 |
| work_keys_str_mv | AT trojanovaz amplitudedependentinternalfrictioninaz31alloysheetssubmittedtoaccumulativerollbonding AT drozdz amplitudedependentinternalfrictioninaz31alloysheetssubmittedtoaccumulativerollbonding AT lukacp amplitudedependentinternalfrictioninaz31alloysheetssubmittedtoaccumulativerollbonding AT minarikp amplitudedependentinternalfrictioninaz31alloysheetssubmittedtoaccumulativerollbonding AT dzuganj amplitudedependentinternalfrictioninaz31alloysheetssubmittedtoaccumulativerollbonding AT halmesovak amplitudedependentinternalfrictioninaz31alloysheetssubmittedtoaccumulativerollbonding AT trojanovaz amplítudnozaležnevnutríšnêtertâvlistahsplavuaz31píddanihnakopičuvalʹnomuzêdnannûvalʹcûvannâm AT drozdz amplítudnozaležnevnutríšnêtertâvlistahsplavuaz31píddanihnakopičuvalʹnomuzêdnannûvalʹcûvannâm AT lukacp amplítudnozaležnevnutríšnêtertâvlistahsplavuaz31píddanihnakopičuvalʹnomuzêdnannûvalʹcûvannâm AT minarikp amplítudnozaležnevnutríšnêtertâvlistahsplavuaz31píddanihnakopičuvalʹnomuzêdnannûvalʹcûvannâm AT dzuganj amplítudnozaležnevnutríšnêtertâvlistahsplavuaz31píddanihnakopičuvalʹnomuzêdnannûvalʹcûvannâm AT halmesovak amplítudnozaležnevnutríšnêtertâvlistahsplavuaz31píddanihnakopičuvalʹnomuzêdnannûvalʹcûvannâm AT trojanovaz amplitudnozavisimoevnutrenneetrenievlistahsplavaaz31podveržennyhnakopitelʹnomusoedineniûprokatkoi AT drozdz amplitudnozavisimoevnutrenneetrenievlistahsplavaaz31podveržennyhnakopitelʹnomusoedineniûprokatkoi AT lukacp amplitudnozavisimoevnutrenneetrenievlistahsplavaaz31podveržennyhnakopitelʹnomusoedineniûprokatkoi AT minarikp amplitudnozavisimoevnutrenneetrenievlistahsplavaaz31podveržennyhnakopitelʹnomusoedineniûprokatkoi AT dzuganj amplitudnozavisimoevnutrenneetrenievlistahsplavaaz31podveržennyhnakopitelʹnomusoedineniûprokatkoi AT halmesovak amplitudnozavisimoevnutrenneetrenievlistahsplavaaz31podveržennyhnakopitelʹnomusoedineniûprokatkoi |