On the proposed martensitic-like structural transformation in V, Nb, and Ta
The transition metals Nb, Ta and V have been known to be cubic at all temperatures, until recently the existence of a martensitic transformation has been reported, based on anomalies in the thermal expansion at low temperatures. Such a structural transformation would have passed unnoticed, because i...
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Cordero, F. 2021-02-04T07:50:50Z 2021-02-04T07:50:50Z 2018 On the proposed martensitic-like structural transformation in V, Nb, and Ta / F. Cordero // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1213-1217. — Бібліогр.: 32 назв. — англ. 0132-6414 https://nasplib.isofts.kiev.ua/handle/123456789/176246 The transition metals Nb, Ta and V have been known to be cubic at all temperatures, until recently the existence of a martensitic transformation has been reported, based on anomalies in the thermal expansion at low temperatures. Such a structural transformation would have passed unnoticed, because it would be hindered by small amounts of impurities. This finding is discussed in the light of anelastic measurements on Nb samples whose purities are comparable to those presenting the dilatometric anomalies. It results that the effects of the alleged transformation on the anelastic spectra would be at least three orders of magnitude smaller than in typical martensitic transformations. A possible alternative explanation for the observed anomalies is proposed in terms of precipitation of unnoticed residual H. До недавнього часу вважалось, що перехідні метали Nb, Ta та V залишаються кубічними при всіх температурах, аж поки не з’явилось повідомлення про існування в них мартенситних перетворень. Повідомлення, яке базувалося на аномаліях, що спостерігалися при вивченні теплового розширення при низьких температурах. Стверджувалось, що це структурне перетворення залишалось непоміченим лише тому, що його прояву заважала невелика кількість домішок. Цей висновок обговорюється з урахуванням вимірювань непружності, проведених на зразках Nb, чистота яких порівнянна з тими, на яких були виявлені дилатометричні аномалії. В результаті встановлено, що вплив перетворення, що було припущене, на непружні спектри є як мінімум на три порядки меншим, ніж у типових мартенситних перетвореннях. Пропонується можливе альтернативне пояснення спостережених аномалій у термінах утворення преципітатів з непоміченого залишкового H. До недавнего времени считалось, что переходные металлы Nb, Ta и V остаются кубическими при всех температурах, пока не появилось сообщение о существовании в них мартенситных превращений. Сообщение основывалось на аномалиях, которые наблюдались при изучении теплового расширения при низких температурах. Утверждалось, что данное структурное преобразование оставалось незамеченным лишь потому, что его проявлению мешало наличие небольшого количества примесей. В настоящей работе сделанный вывод обсуждается с учетом измерений неупругости на образцах Nb, чистота которых сравнима с теми, на которых выявлены дилатометрические аномалии. В результате установлено, что влияние предполагаемого превращения на спектры неупругости как минимум на три порядка меньше, чем в обычных мартенситных превращениях. Предлагается возможное альтернативное объяснение зарегистрированных аномалий в терминах образования преципитатов из неучтенного остаточного H. ru Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України Физика низких температур Низькотемпературна фізика пластичності та міцності On the proposed martensitic-like structural transformation in V, Nb, and Ta Про уявнe мартенситоподібнe структурнe перетворення у V, Nb та Ta О предполагаемом мартенситоподобном структурном преобразовании в V, Nb и Ta Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| title |
On the proposed martensitic-like structural transformation in V, Nb, and Ta |
| spellingShingle |
On the proposed martensitic-like structural transformation in V, Nb, and Ta Cordero, F. Низькотемпературна фізика пластичності та міцності |
| title_short |
On the proposed martensitic-like structural transformation in V, Nb, and Ta |
| title_full |
On the proposed martensitic-like structural transformation in V, Nb, and Ta |
| title_fullStr |
On the proposed martensitic-like structural transformation in V, Nb, and Ta |
| title_full_unstemmed |
On the proposed martensitic-like structural transformation in V, Nb, and Ta |
| title_sort |
on the proposed martensitic-like structural transformation in v, nb, and ta |
| author |
Cordero, F. |
| author_facet |
Cordero, F. |
| topic |
Низькотемпературна фізика пластичності та міцності |
| topic_facet |
Низькотемпературна фізика пластичності та міцності |
| publishDate |
2018 |
| language |
Russian |
| container_title |
Физика низких температур |
| publisher |
Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| format |
Article |
| title_alt |
Про уявнe мартенситоподібнe структурнe перетворення у V, Nb та Ta О предполагаемом мартенситоподобном структурном преобразовании в V, Nb и Ta |
| description |
The transition metals Nb, Ta and V have been known to be cubic at all temperatures, until recently the existence of a martensitic transformation has been reported, based on anomalies in the thermal expansion at low temperatures. Such a structural transformation would have passed unnoticed, because it would be hindered by small
amounts of impurities. This finding is discussed in the light of anelastic measurements on Nb samples whose purities are comparable to those presenting the dilatometric anomalies. It results that the effects of the alleged
transformation on the anelastic spectra would be at least three orders of magnitude smaller than in typical martensitic transformations. A possible alternative explanation for the observed anomalies is proposed in terms of
precipitation of unnoticed residual H.
До недавнього часу вважалось, що перехідні метали Nb,
Ta та V залишаються кубічними при всіх температурах, аж
поки не з’явилось повідомлення про існування в них мартенситних перетворень. Повідомлення, яке базувалося на аномаліях, що спостерігалися при вивченні теплового розширення
при низьких температурах. Стверджувалось, що це структурне перетворення залишалось непоміченим лише тому, що
його прояву заважала невелика кількість домішок. Цей висновок обговорюється з урахуванням вимірювань непружності, проведених на зразках Nb, чистота яких порівнянна з
тими, на яких були виявлені дилатометричні аномалії. В результаті встановлено, що вплив перетворення, що було припущене, на непружні спектри є як мінімум на три порядки
меншим, ніж у типових мартенситних перетвореннях. Пропонується можливе альтернативне пояснення спостережених
аномалій у термінах утворення преципітатів з непоміченого
залишкового H.
До недавнего времени считалось, что переходные металлы
Nb, Ta и V остаются кубическими при всех температурах, пока
не появилось сообщение о существовании в них мартенситных превращений. Сообщение основывалось на аномалиях, которые наблюдались при изучении теплового расширения при
низких температурах. Утверждалось, что данное структурное
преобразование оставалось незамеченным лишь потому, что
его проявлению мешало наличие небольшого количества примесей. В настоящей работе сделанный вывод обсуждается с
учетом измерений неупругости на образцах Nb, чистота которых сравнима с теми, на которых выявлены дилатометрические аномалии. В результате установлено, что влияние предполагаемого превращения на спектры неупругости как
минимум на три порядка меньше, чем в обычных мартенситных превращениях. Предлагается возможное альтернативное
объяснение зарегистрированных аномалий в терминах образования преципитатов из неучтенного остаточного H.
|
| issn |
0132-6414 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/176246 |
| citation_txt |
On the proposed martensitic-like structural transformation in V, Nb, and Ta / F. Cordero // Физика низких температур. — 2018. — Т. 44, № 9. — С. 1213-1217. — Бібліогр.: 32 назв. — англ. |
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2025-11-24T06:45:52Z |
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| fulltext |
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9, pp. 1213–1217
On the proposed martensitic-like structural transformation
in V, Nb, and Ta
F. Cordero
Istituto di Struttura della Materia (ISM-CNR), Area della Ricerca di Roma–Tor Vergata,
Via del Fosso del Cavaliere 100, I-00133 Roma, Italy
E-mail: francesco.cordero@artov.isc.cnr.it
Received March 2, 2018, published online July 26, 2018
The transition metals Nb, Ta and V have been known to be cubic at all temperatures, until recently the exist-
ence of a martensitic transformation has been reported, based on anomalies in the thermal expansion at low tem-
peratures. Such a structural transformation would have passed unnoticed, because it would be hindered by small
amounts of impurities. This finding is discussed in the light of anelastic measurements on Nb samples whose pu-
rities are comparable to those presenting the dilatometric anomalies. It results that the effects of the alleged
transformation on the anelastic spectra would be at least three orders of magnitude smaller than in typical mar-
tensitic transformations. A possible alternative explanation for the observed anomalies is proposed in terms of
precipitation of unnoticed residual H.
Keywords: martensite transformations, acoustic spectroscopy, thermal expansion, transition metals, low tem-
perature.
1. Introduction
In an intriguing Letter [1] it has been reported that crys-
tals of pure Nb, Ta and V exhibit a splitting of the thermal
expansion along the 100 directions below room tempera-
ture, attributed to a previously unknown martensitic trans-
formation (MT). The occurrence of the MT would be pre-
vented by impurities at levels as low as few hundreds at.
ppm, so explaining why it had never been noticed before [1].
It is even postulated that the structural instability in A-15
intermetallics like Nb3Sn is due to the presence of the
Group-Va element itself [1], rather than to their correlation
in one-dimensional chains, as usually accepted [2]. This is a
provocative finding, since Nb, Ta and V have been thor-
oughly studied for decades starting from the 1960s, and are
known to have bcc structure at all temperatures. In order to
induce a structural instability in V, a pressure of 69 GPa
must be applied, so causing a rhombohedral distortion of
the cell [3], while Nb exhibits some shallow softening of
the 44c elastic constant above room temperature [4], and
Ta presents the same effect at 80 GPa [5], but neither
Nb nor Ta have been found to complete the transition to
the rhombohedral state.
Many investigations on these group Va transition met-
als have been conducted by various experimental tech-
niques, including anelastic relaxation and neutron scatter-
ing, which are also the most sensitive techniques in
detecting martensitic transformations. Those investigations
were not focused on martensitic transformations, but on
dislocations and their interaction with the gaseous impuri-
ties H, O, N and C [6–8], or the absorption, diffusion, trap-
ping and tunneling of such impurities, particularly H, and
the complex x T− phase diagrams of MHx (M = V, Nb,
Ta) [9–11], or the coupling of the superconducting transi-
tion to the lattice [12]. These studies were made on vari-
ously doped samples, but in some cases with quite low
levels of impurities [13,14] or undoped [13]. Considering
the sensitivity of the anelastic measurements to structural
phase transitions, a traditional martensitic transformation
would hardly have passed unnoticed.
Also the electronic structure of these transition metals
has been thoroughly studied both experimentally and theo-
retically and has been shown to be at the origin of the ten-
dency or manifestation of structural instability at high tem-
perature and pressure. The softening of the shear elastic
constant 44c is driven by a combination of intraband nest-
ing of the Fermi surface, electronic topological transition,
and band Jahn–Teller effect [5,15]. When the softening
becomes complete, as in V at high pressure, the lattice be-
comes unstable against shears of the 4ε type (Voigt nota-
tion) and becomes rhombohedral, but in Nb and especially
Ta this instability is more than counterbalanced by the
Madelung contribution to the elastic energy [5,15,16]. Tan-
talum is even considered as “prototype metal for the inves-
tigation and calibration of equation of state and material
strength at extreme thermodynamics conditions” [5].
© F. Cordero, 2018
F. Cordero
For these reasons, a report of martensitic-like transfor-
mations so far unnoticed in V, Nb and Ta should be care-
fully considered and verified also by the methods most
sensitive in detecting MTs. Experimental techniques wide-
ly used to study the MTs are diffraction experiments, re-
vealing splittings of the Bragg peaks, TEM revealing the
twin domains of the low-symmetry phase, and anelastic or
ultrasonic experiments exhibiting cusped or step-like sof-
tening of the shear moduli involved in the transformation
and elastic energy loss from the movement of the twin
boundaries. None of these features has ever been reported
in pure and dislocation-free V, Nb and Ta. Yet, the lack of
evidence of MT from the existing studies might be due to
the fact they were mostly made on samples with contents
of impurities, either added or unwanted or unknown, that
would hinder the transformation. Indeed, anelastic relaxa-
tion experiments have been done also on crystals much
purer than those of Ref. 1, for example, on a Nb crystal
with residual resistivity ratio RRR = 10000 measured with
the composite oscillator technique [6], or a Ta crystal with
RRR = 17000 measured with the torsion pendulum [17],
which did not show signs of phase transformations. These
experiments, however, were devoted to studying disloca-
tions on deformed samples, so that the reported anelastic
spectra are dominated by the motions of dislocations. The
search for a MT hindered by minimal amounts of impuri-
ties was not an issue and to my knowledge there are no
reports of the background complex elastic moduli of unde-
formed samples with very high purity. Since the level of
impurities seems to be critical in revealing the MT, here
are presented the anelastic spectra of two samples of Nb
with purities as close as possible to those where a MT ap-
pears in Ref. 1.
2. Experimental
Sample #1 was a 50 5 0.67× × mm polycrystalline bar
prepared by Prof. G. Hörz (MPI für Metallforschung, Inst.
für Werkstoffwissenschaften, Stuttgart). The residual resis-
tivity ratio was RRR = (296 K)/ (0 K) = 320,R R very close
to the value of 347 of the pure Nb crystal of Ref. 1, from
which a residual resistivity 2(0 K) = 6.13 10 ·cm−ρ ⋅ µΩ is
deduced. Assuming that the main contribution is from inter-
stitial O, which contributes with 104.5 10 ·cm/at ppm O−⋅ Ω
[18], the impurity content was O 136c at. ppm, the < sign
being due to the fact that the anelastic spectrum showed also
the presence of H. Sample #2 was a 40 4.5 0.56× × mm bar
cut from Marz grade polycrystalline Nb, previously subject-
ted to various thermal treatments during which O uptake
occurred. The O content estimated from RRR = 26.5 was
Oc 1200 ppm, about ten times larger than in sample #1,
but close to that of the pure Ta crystal of Ref. 1. The impuri-
ty content of sample #2 might also be higher than those of
the heat treated samples of Ref. 1, which are not specified.
The dynamic Young’s modulus ( , ) =E T E iEω −′ ′′ was
measured by suspending the samples on thin thermocouple
wires and electrostatically exciting the flexural modes [19];
the first and fifth flexural modes, whose nodal lines practi-
cally coincide and whose frequencies are in the ratio 1:13.3,
could be measured during a same run.
3. Results and discussion
Figure 1 presents the anelastic spectra of the above
samples: the upper panel contains the relative change of
E ′ with respect to its 0 K value, and the lower panel con-
tains the elastic energy loss coefficient 1 = / .Q E E− ′′ ′ Of
sample #1 are shown the ( )1Q T− curves measured at both
1 and 13 kHz (closed symbols). The almost linear rise of
( )1Q T− is thermoelastic effect [20,21], namely the diffu-
sion of heat between the alternately expanded and com-
pressed faces of the bar during the flexural vibration, with
consequent out-of-phase expansion of the heated region. In
sample #2 (open symbols) there is no trace of additional
dissipation mechanisms, while in sample #1 (closed sym-
bols) there are two peaks at ∼90 K and ∼190 K. These
peaks are shifted to higher T when measured at higher
frequency (smaller symbols) and therefore are due to ther-
mally activated relaxations. The peak at ∼90 K is readily
recognized from its temperature and activation energy as
due to the hopping of residual H trapped by O [22,23],
while the peak at ∼190 K is associated with the simultane-
ous presence of H and dislocations [8,24]. It turns out that,
Fig. 1. Relative change of the Young’s modulus E and elastic
energy loss coefficient Q–1 = E′′/E′ measured on two samples of
Nb with different purities.
1214 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
On the proposed martensitic-like structural transformation in V, Nb, and Ta
in spite of the fact that sample #1 has a RRR 12 times
higher than that of sample #2, its content of residual H and
dislocations is larger. The seeming inconsistency is due to
the fact that H contributes little to the residual resistivity,
especially when it is trapped by an impurity like O, and
dislocations contribute even less. Therefore, the RRR pro-
vides a good estimate of the content of heavy gaseous im-
purities, but neither of H nor of dislocations. The ∼130 at.
ppm O impurities can trap about as many H atoms, and if
untrapped H in excess is also present, it would partially
precipitate into β phase hydride. When this precipitation
from the the gas-like α phase to the α + β phase occurs, it
is accompanied by the formation of dislocations at the
phase interfaces and manifests itself in the anelastic spec-
trum as a sharp rise of dissipation and anomalies in the
modulus [9,10,25,26]. The absence of a clear precipitation
peak indicates that, if any additional H was present in solid
solution, its precipitation might have only occurred below
150 K, and therefore could not exceed hundred at. ppm.
One or two hundred at. ppm is the typical residual content
of H even after prolonged outgassing treatments in UHV,
unless particular precautions are taken, like applying a film
of Pd on the sample surface [17], or an oxide layer during
cooling from the high-temperature annealing [27].
The real parts of the modulus do not present any anom-
aly attributable to structural instabilities, except for the
well known shallow softening above room temperature
from the Fermi surface topology and electron-phonon cou-
pling, which appears as a positive curvature of the E(T)
curve. There is a drop of E(T) below the superconducting
transition at 9.2 K [12], again due to the electron-phonon
coupling, but is invisible on the scale of Fig. 1.
The curves in Fig. 1 exclude the occurrence of any
structural transformation near or below room temperature
with a sensitivity much higher than diffraction experi-
ments. In fact, a MT would appear as a step-like or
cusped softening [28] with amplitudes up to several tens
of percent in the polycrystalline Young’s modulus E [29],
which contains all the elastic constants, but no trace of it
is found in Fig. 1. In addition, the motion of the twin
walls formed in the low-symmetry phase would cause
a very broad thermally activated maximum with sharp
onset at the transformation, whose typical amplitude is
[28,29] ∆Q–1 = 10–3–10–1. A similar anomaly, if present
in Fig. 1, cannot have an amplitude above few 10–6. It
can be concluded that, if a MT occurs in any of the two
samples, it causes elastic and anelastic anomalies with an
amplitude at least three orders of magnitude smaller than
in the known cases of MTs.
It should be stressed that a transformation where the or-
der parameter is strain (ferroelastic transformation), is best
detected in the complex elastic modulus (or its reciprocal,
the compliance), exactly as a ferroelectric or magnetic
transition appears in the dielectric and magnetic suscepti-
bilities. Therefore, in the absence of a clear splitting of the
Bragg peaks in diffraction experiments, the hard evidence
for a ferroelastic transformation should come from elastic
and/or anelastic anomalies, just like the case of the ferro-
electric and ferromagnetic transitions, where the main evi-
dence is the Curie–Weiss peak in the respective suscepti-
bility. This is true also if strain is not the primary order
parameter, but only coupled to it, so causing a possibly
small step-like anomaly in the compliance, rather than a
Curie–Weiss peak [30]. In fact, whatever the nature of the
transition, if the cell departs from the cubic shape, it will
lead to the formation of domain walls, whose motion en-
hances the mechanical loss to levels much higher than the
Q–1(T) curves in Fig. 1.
These data show that the absence assumed so far of
structural transformations near and below room tempera-
ture in Nb is not due to a high amount of impurities, since
it persists at the same content of impurities as in Ref. 1. In
addition, the anelastic spectrum is much more sensitive and
selective in characterizing the status of the sample than
resistivity, which is little sensitive to H and even less to
dislocations. It can be concluded that the interpretation of
the thermal expansion anomaly in Nb, Ta and V as due to a
MT [1] is problematic. Lacking an anelastic characteriza-
tion of those samples, an alternative explanation can only
be speculated in terms of unwanted interstitial H and dislo-
cations. In fact, the estimate in Ref. 1 of < 0.05 at.% H from
the Vickers hardness VH and lattice parameters [31]
seems unreliable, since the error bars and dispersion of
points in the plot of VH vs x in Fig. 5 of Ref. 31 (setting
Hc x≡ in NbHx) do not allow estimates better than
0.005.x∆ This estimate may still seem to exclude that
the precipitation of H is at the origin of the anomalies with
onset just below room temperature, since the solvus line
x(T) separating α and α + β phases in NbHx is close to
0.03 at room temperature. Yet, the reported solvus line is
not a true border at thermodynamic equilibrium, but pre-
sents large hysteresis between heating and cooling and can
be shifted to higher temperature of tens of kelvins just by
repeating the temperature cycles [10,32]. This is due to the
fact that once the precipitates of β phase are plastically
accommodated, the plastic deformation remains and allows
subsequent precipitations to occur at higher temperature.
As a consequence, the anomalies found in Nb [1] are not
incompatible with precipitation of H with 0.01,x if they
are measured after the first cooling run. This is especially
true for the anomalies in V and Ta, which appear well be-
low room temperature and might be accounted for by a
much lower content of H.
Another issue in the interpretation of the anomalies in
the thermal expansion in terms of MT [1] is their anisotro-
py on a macroscopic scale. It is unlikely that, in crystals
with edges long up to 3.5 cm, the transformation strains of
the twin domains do not average in all directions and in-
stead the edges present different elongations, unless the
crystals are strained or rich in dislocations. Analogously,
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1215
F. Cordero
ferromagnetic or ferroelectric materials do not acquire
macroscopic magnetization or polarization in the absence
of an external field or anisotropic defects.
4. Conclusion
In conclusion, a convincing evidence of the existence of
a martensitic-like transformation in Nb, Ta and V can
come from anelastic or diffraction experiments, but the
existing anelastic measurements, including those presented
here, provide a negative answer so far.
_______
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___________________________
Про уявнe мартенситоподібнe структурнe
перетворення у V, Nb та Ta
F. Cordero
До недавнього часу вважалось, що перехідні метали Nb,
Ta та V залишаються кубічними при всіх температурах, аж
поки не з’явилось повідомлення про існування в них мартен-
ситних перетворень. Повідомлення, яке базувалося на анома-
ліях, що спостерігалися при вивченні теплового розширення
при низьких температурах. Стверджувалось, що це структур-
не перетворення залишалось непоміченим лише тому, що
його прояву заважала невелика кількість домішок. Цей ви-
сновок обговорюється з урахуванням вимірювань непружно-
сті, проведених на зразках Nb, чистота яких порівнянна з
тими, на яких були виявлені дилатометричні аномалії. В ре-
зультаті встановлено, що вплив перетворення, що було при-
пущене, на непружні спектри є як мінімум на три порядки
меншим, ніж у типових мартенситних перетвореннях. Про-
понується можливе альтернативне пояснення спостережених
аномалій у термінах утворення преципітатів з непоміченого
залишкового H.
Ключові слова: мартенситні перетворення, акустична спект-
роскопія, теплове розширення, перехідні метали, низькі тем-
ператури.
О предполагаемом мартенситоподобном
структурном преобразовании в V, Nb и Ta
F. Cordero
До недавнего времени считалось, что переходные металлы
Nb, Ta и V остаются кубическими при всех температурах, пока
не появилось сообщение о существовании в них мартенситных
1216 Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9
https://doi.org/10.1103/PhysRevLett.107.075503
https://doi.org/10.1103/PhysRevB.12.3849
https://doi.org/10.1103/PhysRevLett.98.085502
https://doi.org/10.1016/0038-1098(77)90541-5
https://doi.org/10.1016/0038-1098(77)90541-5
https://doi.org/10.1103/PhysRevB.82.132101
https://doi.org/10.1103/PhysRevB.82.132101
https://doi.org/10.1002/pssa.2211570213
https://doi.org/10.1063/1.593784
https://doi.org/10.1063/1.593784
https://doi.org/10.1063/1.1374728
https://doi.org/10.1063/1.1374728
https://doi.org/10.1007/3-540-08705-2
https://doi.org/10.1007/BFb0103398
https://doi.org/10.1007/BFb0103398
https://doi.org/10.1016/j.msea.2006.02.231
https://doi.org/10.1016/j.msea.2006.02.231
https://doi.org/10.1103/PhysRevB.49.15040
https://doi.org/10.1016/j.jpcs.2006.05.027
https://doi.org/10.1016/j.jpcs.2006.05.027
https://doi.org/10.1016/0038-1098(80)90957-6
https://doi.org/10.1016/0001-6160(89)90111-9
https://doi.org/10.1088/0957-0233/20/1/015702
https://doi.org/10.1063/1.322341
https://doi.org/10.1016/0001-6160(75)90011-5
https://doi.org/10.1016/0038-1098(82)90077-1
https://doi.org/10.1016/0036-9748(72)90060-9
https://doi.org/10.1016/0036-9748(84)90173-X
https://doi.org/10.1016/0001-6160(82)90101-8
https://doi.org/10.1016/0036-9748(80)90203-3
https://doi.org/10.1016/0036-9748(80)90203-3
https://doi.org/10.1016/S0925-8388(02)01289-6
https://doi.org/10.1080/00018737300101379
https://doi.org/10.1016/j.jallcom.2006.01.043
https://doi.org/10.1016/j.jallcom.2006.01.043
https://doi.org/10.1016/0036-9748(76)90331-8
On the proposed martensitic-like structural transformation in V, Nb, and Ta
превращений. Сообщение основывалось на аномалиях, кото-
рые наблюдались при изучении теплового расширения при
низких температурах. Утверждалось, что данное структурное
преобразование оставалось незамеченным лишь потому, что
его проявлению мешало наличие небольшого количества при-
месей. В настоящей работе сделанный вывод обсуждается с
учетом измерений неупругости на образцах Nb, чистота кото-
рых сравнима с теми, на которых выявлены дилатометриче-
ские аномалии. В результате установлено, что влияние пред-
полагаемого превращения на спектры неупругости как
минимум на три порядка меньше, чем в обычных мартенсит-
ных превращениях. Предлагается возможное альтернативное
объяснение зарегистрированных аномалий в терминах образо-
вания преципитатов из неучтенного остаточного H.
Ключевые слова: мартенситные превращения, акустическая
спектроскопия, тепловое расширение, переходные металлы,
низкие температуры.
Low Temperature Physics/Fizika Nizkikh Temperatur, 2018, v. 44, No. 9 1217
1. Introduction
2. Experimental
3. Results and discussion
4. Conclusion
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