The Formation Energy of Martensite Nuclei and the Phase Transition Kinetics under the Action of an External Magnetic Field

2021 ◽  
Vol 410 ◽  
pp. 3-8
Author(s):  
Viktor N. Pustovoit ◽  
Yuri V. Dolgachev
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Initial Phase ◽  
Formation Energy ◽  
Martensite Phase ◽  
Nucleation Center ◽  
Austenite Matrix ◽  
Ferromagnetic Order ◽  
The Matrix ◽  
Phase Transition Kinetics

The formation energy of martensite nuclei in the austenite matrix is calculated. Nanoclusters with ferromagnetic order, which exist in austenite above the Curie temperature, reduce the formation energy of a critical martensite nucleation center when exposed to an external magnetic field. The data obtained are explained by the magnetic separation of the initial phase under the action of a magnetic field. A fluctuation increase in nanovolumes with a ferromagnetic order in austenite increases the energy in a atoms group of the matrix phase with a parallel spins arrangement. As a result, the nucleation rate of the martensite phase increases and the martensitic transformation proceeds more completely.

scholarly journals Correlation of composition, aspect ratio and magnetic resistance of multilayer micro- and nanowires of the “ferromagnetic / diamagnetic” type

Doklady BGUIR ◽  
2021 ◽  
Vol 19 (2) ◽  
pp. 5-13
Author(s):  
V. M. Fedosyuk
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Aspect Ratio ◽  
Aluminum Oxide ◽  
Giant Magnetoresistance ◽  
Pore Diameter ◽  
Ferromagnetic Layer ◽  
Type I ◽  
Magnetic Layers ◽  
The Matrix

 The results of study of the giant magnetoresistance coefficient (GMR) in multilayer micro- and nanowires based on successively alternating ferromagnetic (Co, CoNi and NiFe) and diamagnetic (Cu) layers are presented in the paper. The samples were obtained by electrochemical deposition into the matrix pores. Aluminum oxide was used as matrices. To establish the influence of the aspect ratio, matrices of two types were used: with a pore diameter of 8 µm and 170–200 nm and a variable thickness from 10 to 60 µm. Investigations of the GMR coefficient were carried out by measuring the current-voltage characteristics in external magnetic fields up to 130 mT. When using type I matrices (pore diameter 8 μm), a positive GMR coefficient (an increase in electrical resistivity in an external magnetic field) was noted, while when using type II matrices (pore diameter 170–200 nm), a negative GMR coefficient was established (a decrease in electrical resistance in an external magnetic field). This is due to the enhancement of the interactions of spin-polarized electrons in the magnetic layers through the copper layer through the RKKY exchange with an increase in the aspect ratio. A significant effect of the composition of the ferromagnetic layer (Co, CoNi, and NiFe) on the value  of the GMR coefficient is noted. The maximum value of the negative GMR coefficient (up to –27.5 %) was established for the CoNi-based nanowire system. The use of multilayer micro- and nanowires, electrolytically deposited in a matrix of aluminum oxide with the ability to control the GMR coefficients, opens up perspective use of these objects as sensitive elements (sensors) of a constant magnetic field, as well as devices for storing magnetic information with a vertical principle. 

Energy Absorption/Dissipation Performances of Magnetic-Sensitive Rubber (MSR) With Hollow Iron Balls

2015 ◽  
Author(s):  
Shengqiang Zhang ◽  
Lingyu Sun ◽  
Dingxin Leng ◽  
Bincheng Huang ◽  
Jun Xu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Energy Absorption ◽  
Strain Energy ◽  
Effective Strain ◽  
Stress Concentrations ◽  
Buffer Material ◽  
The Matrix ◽  
Thin Walled ◽  
Applied External Magnetic Field

A kind of novel smart buffer material, magnetic-sensitive rubber (MSR) with embedded thin-walled iron balls, is provided, and the energy absorption and energy dissipation properties are investigated numerically. Two kinds of representative volume elements (RVEs) of MSR specimens with solid or hollow iron balls are studied, respectively. Under uniaxial compression alone or combined with magnetic field, the relation between effective stress and effective strain and that between strain energy desity and total compression deformation for these two specimens are established, respectively. With the increase of strain, it is demonstrated numerically that the MSRs with hollow iron balls have better energy absorption/dissipation capability than previous MSRs with solid balls. And the applied external magnetic-field increases this capability more. Under compression, the stress concentrations in elastomer matrix around the hollow balls decrease, that could increase the ultimate compression loads before the matrix failures. This is beneficial for us to design lightweight and efficient buffers according to different application cases.

Factorization of the evolution operator for a spin–orbit coupled system in an external magnetic field for an arbitrary L and

1976 ◽  
Vol 54 (23) ◽  
pp. 2295-2305
Author(s):  
R. Bogdanović ◽  
M. A. Whitehead ◽  
M. S. Gopinathan
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Evolution Operator ◽  
Coupled System ◽  
Projection Operators ◽  
Spin Orbit ◽  
Group Representations ◽  
Special Cases ◽  
The Matrix ◽  
Strong External Field

The evolution operator of the spin–orbit coupled system in an external magnetic field is factorized according to the operator equation:[Formula: see text]where HSO is the spin–orbit coupled Hamiltonian and HZ is the Zeeman Hamiltonian. The preceding equation is expressed in matrix form using the theory of the O(4) group representations. For the special case of [Formula: see text], an explicit form of the matrix C(t) is found. The operator corresponding to the matrix C(t) is found in a closed form using the projection operators constructed in the Appendix. Two special cases, corresponding to a weak and a strong external field, are considered, and possible applications of the results obtained are indicated.

Orientation loss of microcrystals of DyBa2Cu3Oy in a polymer composite during curing of the medium under an external magnetic field

CrystEngComm ◽  
2020 ◽  
Vol 22 (34) ◽  
pp. 5606-5612
Author(s):  
Tsunehisa Kimura ◽  
Hayato Kashiwagi ◽  
Fumiko Kimura ◽  
Shigeru Horii ◽  
Kazuki Takeda ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Polymer Composite ◽  
X Ray Diffraction ◽  
Consolidation Process ◽  
X Ray ◽  
The Matrix

The orientation loss of microcrystals during solidifying the matrix in a magnetic field was modeled. In situ X-ray diffraction results obtained for the consolidation process of DyBa2Cu3Oy microcrystal suspension were explained by the model presented.

scholarly journals Декорированная изинговская квадратная решетка в магнитном поле

2020 ◽  
Vol 62 (5) ◽  
pp. 683
Author(s):  
Ф.А. Кассан-Оглы ◽  
А.И. Прошкин ◽  
А.К. Муртазаев ◽  
В.А. Мутайламов
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Ising Model ◽  
External Magnetic Field ◽  
Initial Phase ◽  
Transition Point ◽  
Phase Transition Point ◽  
Square Lattice ◽  
Low Field ◽  
Exchange Parameters

Ising model on decorated square lattice is studied with arbitrary signs and values of exchange parameters in an external magnetic field. Comparison with the results of Ising madel on nondecorated square lattice is performed. It is shown that if magnetization increases antiferromagnetically then initial phase-transition-point gradually decreases up to the first frustration field and does not appear again even if further frustration fields apear. In the case of ferromagnetic type of magnetization increasing the phase transition disappears right away after switching on of magnetic field. In other words, an arbitrary low field completely suppresses the phase transition.

Features of Martensitic Transformation in Steel during Quenching in a Constant Magnetic Field

2019 ◽  
Vol 946 ◽  
pp. 304-308 ◽  
Author(s):  
Viktor N. Pustovoit ◽  
Yuri V. Dolgachev ◽  
L.P. Aref'eva
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
External Magnetic Field ◽  
Constant Magnetic Field ◽  
Electric Resistivity ◽  
Nucleation Center ◽  
Martensite Formation ◽  
Resistivity Method ◽  
Elastic Forces ◽  
Energy Of Formation

The data on the occurrence of martensitic transformation in steel under the action of a magnetic field were obtained by the electric resistivity method. The obtained data indicate the possibility of stress-assisted martensite formation in the temperature range of Ms-Md (in which superplasticity of austenite is observed). This possibility is due to the magnetic heterogeneity of austenite. Nanosized regions with a ferromagnetic order are present in the paramagnetic matrix. They can perceive the energy of the external magnetic field through the magnetostrictive stresses and change the fields of the elastic forces in the crystal lattice. All this leads to a decrease in the energy of formation of the nucleation center.

scholarly journals The induction of electric currents in a non-uniform ionosphere

1948 ◽  
Vol 195 (1041) ◽  
pp. 198-224 ◽  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Diurnal Variation ◽  
Initial Phase ◽  
Frequency Of Occurrence ◽  
Magnetic Disturbance ◽  
The Earth ◽  
Disturbance Vector ◽  
Sudden Commencements ◽  
The Magnetic Field

Calculations are made of the distribution and the magnetic field of the currents induced in a non-uniformly conducting ionospheric shell by an external magnetic field, which is either periodic or subject to sudden changes. Assuming that the initial phase of magnetic storms is due to field changes outside the ionosphere, it is shown that its mean integrated conductivity is probably not much greater than 10 -7 e.m.u. It is found that electromagnetic shielding by the ionosphere has an important effect on the distribution of field changes observed on the earth, and may lead to an apparent diurnal variation of frequency of occurrence of sudden commencements at a given station. Simple explanations are suggested for some known features of micropulsations, and for some well-known phenomena of magnetic disturbance, including Sangster’s rotating disturbance vector.

scholarly journals Dual Properties of Polyvinyl Alcohol-Based Magnetorheological Plastomer with Different Ratio of DMSO/Water

Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7758
Author(s):  
Norhiwani Mohd Hapipi ◽  
Saiful Amri Mazlan ◽  
Ubaidillah Ubaidillah ◽  
Siti Aishah Abdul Aziz ◽  
Seung-Bok Choi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Polyvinyl Alcohol ◽  
Solvent Mixture ◽  
Binary Solvent ◽  
Solvent Ratio ◽  
Sensors And Actuators ◽  
Relative Shear ◽  
The Matrix ◽  
Mr Effect

Polyvinyl alcohol (PVA)-based magnetorheological plastomer (MRP) possesses excellent magnetically dependent mechanical properties such as the magnetorheological effect (MR effect) when exposed to an external magnetic field. PVA-based MRP also shows a shear stiffening (ST) effect, which is very beneficial in fabricating pressure sensor. Thus, it can automatically respond to external stimuli such as shear force without the magnetic field. The dual properties of PVA-based MRP mainly on the ST and MR effect are rarely reported. Therefore, this work empirically investigates the dual properties of this smart material under the influence of different solvent compositions (20:80, 40:60, 60:40, and 80:20) by varying the ratios of binary solvent mixture (dimethyl sulfoxide (DMSO) to water). Upon applying a shear stress with excitation frequencies from 0.01 to 10 Hz, the storage modulus (G′) for PVA-based MRP with DMSO to water ratio of 20:40 increases from 6.62 × 10−5 to 0.035 MPa. This result demonstrates an excellent ST effect with the relative shear stiffening effect (RSTE) up to 52,827%. In addition, both the ST and MR effect show a downward trend with increasing DMSO content to water. Notably, the physical state of hydrogel MRP could be changed with different solvent ratios either in the liquid-like or solid-like state. On the other hand, a transient stepwise experiment showed that the solvent’s composition had a positive effect on the arrangement of CIPs within the matrix as a function of the external magnetic field. Therefore, the solvent ratio (DMSO/water) can influence both ST and MR effects of hydrogel MRP, which need to be emphasized in the fabrication of hydrogel MRP for appropriate applications primarily with soft sensors and actuators for dynamic motion control.

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