共查询到20条相似文献,搜索用时 31 毫秒
1.
G. A. Malygin 《Physics of the Solid State》2003,45(9):1784-1789
A mechanism for the bidirectional and all-round shape memory effects observed in titanium nickelide crystals is discussed quantitatively by using the theory of diffuse martensitic transformations (DMTs). These effects are associated with an anisotropic distribution of Ti3Ni4 particles, which arises in bent crystals subjected to annealing followed by relaxation of coherent microstresses produced by the particles. Using the DMT theory, the influence of the stepwise B2 → R → B19′ phase transition on the magnitude and sign of the radius of curvature of a thin strip of titanium nick-elide is calculated and the conditions are determined under which the bidirectional and all-round shape memory effects occur depending on structural factors and the geometrical parameters of the strip. 相似文献
2.
G. A. Malygin 《Physics of the Solid State》2003,45(8):1566-1571
The formation of martensite in an elastic stress field near a disk-shaped coherent precipitate is discussed in terms of the theory of diffuse martensitic transformations. The heterogeneous martensite nucleation on precipitates is found to increase the characteristic martensitic-transformation temperature, which increases linearly with the volume density of precipitates. The theoretical results are illustrated quantitatively using the example of the B2 → R phase transition in titanium nickelide alloys. 相似文献
3.
V. G. Pushin N. N. Kuranova A. V. Pushin A. V. Korolev N. I. Kourov 《Technical Physics》2016,61(4):554-562
The effect of copper alloying up to 25 at % on the structure–phase transformations and the physicomechanical properties of ternary alloys from the quasi-binary TiNi–TiCu section is studied by measuring the physicomechanical properties, transmission electron microscopy, scanning electron microscopy, electron diffraction, and X-ray diffraction (XRD). The data of temperature measurements of the electrical resistivity and the magnetic susceptibility and XRD data are used to plot a general diagram for the thermoelastic B2 ? B19', B2 ? B19 ? B19', and B2 ? B19 martensitic transformations, which occur in the alloys upon cooling as the copper content increases in the ranges 0–8, 8–15, and 15–25 at % Cu, respectively. The experimental results are compared to the well-known data, including differential scanning calorimetry data, obtained for these alloys. The changes in the mechanical properties and the microstructure of the alloys in the state of B19 or B19' martensite are discussed. 相似文献
4.
Klopotov A. A. Potekaev A. I. Gribov Yu. A. Kozlov E. V. 《Russian Physics Journal》2003,46(7):697-707
The paper presents an analysis of regular features of variations in phase composition and atomic volume of the austenite and martensite phases, and the value of Bein's deformation during thermoelastic martensitic transformations versus crystallochemical factors in low-stability alloys based on titanium nickelide doped by different elements (Fe, Co, Rh, Cu, Pd, Pt, Au). It is established that the low-stability alloys undergoing different sequences of martensitic transformations (B2–B19, B2–B19, B2–R–B19) demonstrate different values and character of the atomic hopping range during transformation. 相似文献
5.
Results are given of an in situ X-ray diffraction study of the crystal-lattice state of a TiNi-based alloy during deformation under the effect of an external
stress in the pretransition region preceding the B2-R-B19′ martensitic transformations. The pretransition state preceding martensitic transformations in the alloy under study was
found to manifest itself in a specific behavior of the lattice parameter and thermal expansion coefficient in the B2 phase. The magnitude of the thermal expansion coefficient in the B2 phase nonmonotonically depends on the amount of deformation and the applied stress. 相似文献
6.
V. G. Pushin N. N. Kuranova A. V. Pushin A. N. Uksusnikov N. I. Kourov 《Technical Physics》2016,61(7):1009-1014
The effect of alloying by 12–20 at % Hf on the structure, the phase composition, and the thermoelastic martensitic transformations in ternary alloys of the quasi-binary NiTi–NiHf section is studied by transmission electron microscopy, scanning electron microscopy, electron diffraction, and X-ray diffraction. The electrical resistivity is measured at various temperatures to determine the critical transformation temperatures. The data on phase composition are used to plot a full diagram for the high-temperature thermoelastic B2 ? B19’ martensitic transformations, which occur in the temperature range 320–600 K when the hafnium content increases from 12 to 20 at %. The lattice parameters of the B2 and B19’ phases are measured, and the microstructure of the B19’ martensite is analyzed. 相似文献
7.
N. N. Kuranova A. V. Pushin V. G. Pushin A. N. Uksusnikov N. I. Kourov 《Technical Physics》2014,59(5):685-691
The ternary metastable TiNiFe alloys that exhibit a low-temperature shape memory effect and are subjected to plastic deformation by rolling or high-pressure torsion followed by heat treatment are studied by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and electrical resistivity measurements. It is found that moderate plastic deformation of a Ti50Ni49Fe1 alloy at room temperature initiates the thermoelastic B2 ? B19’ martensitic transformation and the formation of a developed banded dislocation and twin substructure in the B19’ martensite. This deformation of a Ti50Ni47Fe3 alloy forms a similar dislocation substructure but in B2 austenite. Megaplastic deformation by high-pressure torsion causes amorphization in the Ti50Ni49Fe1 alloy and nanofragmentation in the Ti50Ni47Fe3 alloy. The evolution of the nanostructure and the martensitic transformations in TiNiFe-based ternary alloys is studied during plastic deformation and subsequent annealing at various temperatures. 相似文献
8.
N. N. Kuranova A. V. Pushin A. N. Uksusnikov E. S. Belosludtseva N. I. Kourov T. E. Kuntsevich V. G. Pushin 《Technical Physics》2017,62(8):1189-1193
We have reported the results of investigations of the structure and chemical and phase compositions of the amorphous Ni50Ti32Hf18 alloy prepared by rapid quenching from melt by spinning and subjected to heat treatments. The specific features of the fine polycrystalline alloy structure formation depending on the heat-treatment mode have been studied by transmission and scanning electron microscopy, chemical microanalysis, electron diffraction, and X-ray diffraction analysis. According to the data on the temperature behavior of electrical resistivity, critical temperatures of devitrification and subsequent thermoelastic martensitic transformation B2 → B19′ have been determined. The mechanical properties in different heat-treatment modes have been investigated. 相似文献
9.
The electric dipole moment of the B → X transition of 81Br2 has been calculated from the measured absorption of single vibration-rotation lines with a YAG laser at 558 nm to be |Re|2 = 0.12 D2. The corresponding radiative lifetime is τrad = 20 μsec. Fluorescence decay times have been measured, as a function of pressure, with a narrowband, nitrogen pumped, dye laser, for vibrational levels v′ = 16, 19, 23. The quantum yield for predissociation at zero pressure is near unity. 相似文献
10.
V. V. Novikov D. V. Avdashchenko N. V. Mitroshenkov A. V. Matovnikov S. L. Bud’ko 《Physics of the Solid State》2014,56(10):2069-2076
Thermal characteristics of the phonon and magnon subsystems of icosahedral borides RB66 (R = Gd, Tb, Dy, Ho, Eu, or Lu) have been studied based on the obtained experimental data on the thermal expansion of the borides and the earlier results on their heat capacity in the range of 2–300 K. The contribution to the expansion of borides containing paramagnetic R 3+ ions, which is characteristic of transition to the spin-glass state, has been revealed. The phonon spectrum moments of RB66 compounds and the Grüneisen parameters have been calculated. 相似文献
11.
In this work we used x-ray structural analysis to investigate the martensitic transformations (MTs)B2R andRB19 in Ti(Ni, Fe) alloys containing 1, 2.5, 4, 5 at. % Fe, and the effect of heat treatment on the MT temperatures and sequence. In the majority of cases, it was found that the MTB2R proceeds through a two-phase region (+R). Heat treatment leads to a narrowing of the temperature interval of the existence of the two-phase region, weakly affects the onset temperatures of the MTsB2R TR andRB19 Ms, and sharply increases the temperature-of the end of the MT Me. The existence of the two-phase region is related to the two MT channelsB2R andB2B19 initially intrinsic to the allovs of the given compositions.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 19–22, December, 1989. 相似文献
12.
Measurements of the microwave spectrum of the C4v molecule IF5 in the excited vibrational states v5(B1) = 1 and v9(E) = 1 are reported for the transitions J4 → 5, 5 → 6, 6 → 7, 8 → 9, and 9 → 10 (27–55 GHz). The Coriolis resonance interaction between these two states is analyzed by diagonalization of Hamiltonian matrices of dimension 3 × (2J + 1) in which all (Δl,Δk) = (±2, ±2)(q+), (±2, ±2)(q?), and (0, ±4)(R6) interactions are included as off-diagonal terms in addition to the v5 = 1 ? v9 = 1, l9 = ±1(R59) Coriolis interaction. In the v9 = 1 state spectra, the l-doubling of the kl = ?1 transitions and splittings of the kl = ?3 transitions and splittings of the kl = +3 transitions, all enhanced by the Coriolis resonance, have been observed and measured. Least-squares refined rovibrational parameters for the v5 = 1 and v9 = 1 states are reported and a preliminary value for the rotational constant C9 has been obtained. 相似文献
13.
Phase transformation characteristics of a Ti-Ni-Pd shape memory thin film composition spread have been investigated. The thin film composition spread was fabricated from elemental targets using an ultra-high vacuum combinatorial magnetron sputter-deposition system and subsequent annealing at 500 °C for 1 h in situ. Automated temperature-dependent resistance measurements (R(T)), energy dispersive X-ray analysis (EDX) and X-ray diffraction measurements (XRD) have been applied for the high-throughput characterization of the composition spread. Reversible phase transformations within the measurement range of −40 to 250 °C within the Ti-Ni-Pd system were observed for compositions with Ti content between 50 and ∼59 at.%. For Ti-richer films, Ti2Ni and Ti2Pd precipitates are inhibiting reversible phase transformations. The transformation temperatures and the thermal hysteresis were determined from R(T) measurements. Rising transformation temperatures with increasing Pd content and significantly lower thermal hysteresis for the B2-B19, compared to the B2-R-B19′ transformations were found in good agreement with published data. For low Pd contents (<7-12 at.%, depending on the Ti content) two-stage B2-R-B19′ transformations were observed. Compositions with higher Pd contents showed a single-stage B2-B19 transformation. Increasing Ti content within the B2-B19 transformation region results in a linear increase of the thermal hysteresis and decreasing transformation temperatures. 相似文献
14.
F. Štěrba 《Czechoslovak Journal of Physics》1968,18(7):900-909
The ground state rotational bands in the odd isotopes of uranium U 233 and U 235, were studied by the inelastic scattering of 13.1 MeV deuterons. Seven members of these bands were seen in both nuclei. By fitting the experimental energies of the levels to the relation E(I)= =AI(I+1)+B[I(I+1)]2, the parametersA andB were determined. Their values and the upper limits of the quadrupole reduced transition probabilities determined from the cross sections were: U 233:A=(5.93±0.10)keV,B=(?0.002±0.001)keV,B(E2,5/2→7/2)= =(6.51±0.66)×10?48 e2 cm4,B(E2,5/2→9/2)=(2.80±0.37) X 10?48 e2 cm4. U 235:A=(5.36±0.04)keV,B=(?0.0017±0.0004) keV,B(E2,7/2→9/2)=(8.05±0.71) × × 10?48 e2 cm4,B(E2,7/2→11/2)=(2.17±0.39) X 10?48 e2 cm4. 相似文献
15.
V. G. Pushin N. N. Kuranova N. I. Kourov R. Z. Valiev E. Z. Valiev V. V. Makarov A. V. Pushin A. N. Uksusnikov 《Technical Physics》2012,57(8):1106-1114
The effects of a high pressure and torsional plastic deformation in Bridgman anvils on the structure and phase transformations in titanium nickelide-based shape memory alloys are studied by electron microscopy, neutron diffraction, and X-ray diffraction. The physical properties of the alloys are measured. It is found that the baroelastic effects related to the highly reversible B2 ? B19?? martensitic transformation can occur in metastable austenitic titanium nickelide alloys in both the standard polycrystalline and nanocrystalline states under high pressure. 相似文献
16.
M. V. Gorev V. S. Bondarev S. I. Raevskaya M. P. Ivliev I. P. Raevskii I. N. Flerov 《Physics of the Solid State》2014,56(2):367-372
The heat capacity and thermal expansion of ceramic samples of the Na0.95K0.05NbO3 solid solution have been investigated over a wide temperature range of 100–750 K. The observed anomalies in the heat capacity and thermal expansion at T 4 = 297 K, T 3 = 535 K, T 2 = 665 K, and T 1 ≈ 710 K correspond to the sequences of phase transitions N → Q → G → S → T1. It has been shown that, as a result of the phase transitions, the unit cell volume at T 4 and T 2 decreases, and at T 3 and T 1, increases with increasing temperature. The directions of the shift of the phase transition temperatures induced by hydrostatic pressure have been determined. It has been established that all structural transformations are accompanied by relatively small variations in the entropy. Different mechanisms of the structural distortions have been discussed. 相似文献
17.
E. I. Pogorel’tsev S. V. Mel’nikova A. V. Kartashev M. S. Molokeev M. V. Gorev I. N. Flerov N. M. Laptash 《Physics of the Solid State》2013,55(3):611-618
The heat capacity, unit cell parameters, permittivity, optical properties, and thermal expansion of the (NH4)2TaF7 compound with a seven-coordinated anion polyhedron have been measured. It has been found that the compound undergoes two successive phase transitions with the symmetry change: tetragonal → (T 1 = 174 K) orthorhombic → (T 2 = 156 K) tetragonal. The ferroelastic nature of structural transformations has been established, and their entropy and susceptibility to hydrostatic pressure have been determined. 相似文献
18.
M. N. Achasov S. E. Baru K. I. Beloborodov A. V. Berdyugin A. V. Bozhenok A. G. Bogdanchikov D. A. Bukin S. V. Burdin A. V. Vasil’ev Yu. S. Velikzhanin T. V. Dimova V. P. Druzhinin M. S. Dubrovin D. I. Ganyushin I. A. Gaponenko V. B. Golubev V. N. Ivanchenko I. A. Koop A. A. Korol’ S. V. Koshuba G. A. Kukartsev E. V. Pakhtusova A. A. Sal’nikov S. I. Serednyakov V. V. Sharyi Yu. M. Shatunov V. A. Sidorov Z. K. Silagadze 《JETP Letters》2000,72(6):282-285
The e + e ?→ηγ→7γ process was studied in the energy range 2E=600–1060 MeV with an SND detector on a VEPP-2M e + e ? collider. The decay branching ratios B(φ→ηγ)=(1.353±0.011±0.052)×10?2, B(ω→ηγ)=(4.62±0.71±0.18)×10?4, and B(ρ→ηγ)=(2.73±0.31±0.15)×10?4 were measured. 相似文献
19.
The stability of the stacking ordered structures of close-packed layers in Mg-In alloys near Mg3In and pseudo-binary alloys Mg3(In1?yCdy) for 0 ? y ? 1 is studied from a standpoint based on the pseudopotential theory. An expression of the structure-dependent energy for an arbitrary type of layer stacking is given by the method described in the previous papers [1,2]. The numerical results explain well the observed trends in the composition and pressure dependences of stacking sequence; the orders of appearance of stacking variants are 3R → 12R → 2H with an increasing Mg-content for Mg-In alloys near Mg3In, 12R → 18R → 2H with an increasing Cd-content for Mg3(In1?yCdy) and 12R → 18R → 24R with an increasing pressure for Mg3ln. Speaking in detail, however, the present calculation fails to reproduce a 12R-structure (β1-phase) at 25% In in the Mg-In system, an 18R-structure of Mg3(In0.65Cd0.35) and an 18R-structure of Mg3In found under pressure of 20–55 kb, although the energy differences are small in all the cases. From the analysis of components of the structure-dependent energy, it is concluded that the favorable type of layer stacking is determined predominantly by a contribution from the band-structure energy term of a state with the disordered arrangement of constituent atoms and also that an energy required to the alternation of stacking of layers is apparently smaller than the ordering energy. If a specific layer sequence is characterized by a hexagonality, the alloys vary their sequences in such a way that the hexagonality increases from zero (3R) to unity (2H) as the electron-to-atom ratio of the alloys decreases from 2·3 to 2·0.The Ewald and Madelung constants are calculated for various types of layer structure. Both constants change linearly with hexagonality, without regard to period, symmetry and layer sequence. 相似文献
20.
Angular correlations have been measured between γ-rays from the 2 → 2 → 0 cascades in 106,112,114Cd and the beam of 11.0 MeV α particles effecting Coulomb excitation. Multipole admixtures for the 2 → 2 transitions, as deduced from these correlations, when combined with earlier results establish their B(E2) and B(M1) values. For the transitions from the 1312 and 1208 keV states in 112,114Cd the B(E2) values in single-particle units are 18±4 and 24±7. These values are typical for transitions from “two-quadrupole-phonon” states in this mass region whereas that of the 1718 keV transition in 106Cd has the smaller value of 7.0±2.3. The B(E2) values of the 2 → 2 transitions in 112,114Cd from the 1468 and 1363 keV states are < 0.3 single-particle units. The B(M1) values of all five transitions are ≈ 10?2. 相似文献