Phase diagrams in the NiMnGa system under compression

Chernenko, V.A.; Кокорин, В. В.; Babii, O. M.; Zasimchuk, I. K.

doi:10.1016/s0966-9795(97)00050-2

Cited by 62 publications

(32 citation statements)

References 8 publications

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“…This value of parameter κ results in a ∆S mag = 14.3 J/kg K, which corresponds to a Q mag = 4.1 J/g, with T M ≈ 285 K for this alloy. The estimated Q mag is similar to the experimental value of the transformation heat Q ≈ 4.2 J/g reported for this alloy [22,23]. It can be concluded, therefore, that the magnetic subsystem of this alloy is the main contributor to transformation heat and entropy change.…”

Section: Evaluation Of Magnetic and Non-magnetic Contributions To ∆S supporting

confidence: 86%

Entropy Change Caused by Martensitic Transformations of Ferromagnetic Shape Memory Alloys

L’vov

Cesari

Kosogor

et al. 2017

Metals

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Abstract:In this paper, our most recent findings on the influence of magnetic order on the main transformational caloric and elastic properties of shape memory alloys (SMAs) are reviewed. It is argued that ferromagnetic order has a strong influence on the temperature interval of martensitic transformation (MT), the characteristics of stress-induced MT, and the shear elastic modulus of SMA. The problem of separation of the magnetic contributions to the entropy change ∆S and heat Q exchanged in the course of martensitic transformation (MT) of SMA is considered in general terms, and theoretical formulas enabling the solution of the problem are presented. As an example, the ∆S and Q values, which were experimentally determined for Ni-Mn-Ga and Ni-Fe-Ga alloys with different Curie temperatures T C and MT temperatures T M , are theoretically analyzed. It is shown that for Ni-Mn-Ga martensites with T M < T C , the ratio of elastic and magnetic contributions to the entropy change may be greater or smaller than unity, depending on the temperature difference T C -T M .

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Section: Evaluation Of Magnetic and Non-magnetic Contributions To ∆S supporting

confidence: 86%

Entropy Change Caused by Martensitic Transformations of Ferromagnetic Shape Memory Alloys

L’vov

Cesari

Kosogor

et al. 2017

Metals

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“…For instance, in the first neutron diffraction studies of a sample of stoichiometric composition [14] it was found that there are additional reflections of the tetragonal phase and it was assumed that this phase is modulated along, apparently, the [100] direction. Further studies of the crystal structure of the low-temperature phase in non-stoichiometric compounds revealed a complex pattern of formation of different martensitic phases and the presence of intermartensitic phase transitions in the system Ni 2+x+y Mn 1−x Ga 1−y [44][45][46][47][48][49][50][51][52][53][54][55][56][57]. In the early stages of such studies the superstructural motifs were described as static displacement waves (modulations) [44], although lately an alternative approach is being developed, in which the superstructural reflections of martensite are interpreted as long-period rearrangements of closely packed planes of the {100} type [25,57].…”

Section: Superstructural Motivesmentioning

confidence: 99%

Shape memory ferromagnets

Васильев¹,

Buchelnikov²,

Takagi³

et al. 2003

Phys.-Usp.

249

135

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In ferromagnetic alloys with shape memory large reversible strains can be obtained by rearranging the martensitic domain structure by a magnetic field. Magnetization through displacement of domain walls is possible in the presence of high magnetocrystalline anisotropy, when martensitic structure rearrangement is energetically favorable compared to the reorientation of magnetic moments. In ferromagnetic Heusler alloys Ni2+xMn1−xGa the Curie temperature exceeds the martensitic transformation temperature. The fact that these two temperatures are close to room temperature offers the possibility of magnetically controlling the shape and size of ferromagnets in the martensitic state. In Ni2+xMn1−xGa single crystals, a reversible strain of ∼ 6% is obtained in fields of ∼ 1 T.

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“…Refs. [8][9][10]. The most clear way to study the superelastic behavior of alloys is the analysis of non-linear stress-strain dependencies obtained experimentally in the course of stress-induced MT-s.…”

Section: Introductionmentioning

confidence: 99%

Stress-induced Martensitic Transformation and Superelasticity of Alloys: Experiment and Theory

et al. 2005

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The superelasticity of alloys undergoing a stress-induced martensitic transformation is studied in both experimental and theoretical way. Experimental stress-strain dependencies illustrating the different types of superelastic behavior are taken from Ni-Mn-Ga alloys typifying thermoelastic martensites and then modeled theoretically using a statistical approach to describe the growth of stress-induced martensite in the matrix of parent (austenitic) phase. A good agreement between the experimental and theoretical results is achieved whereby a physical interpretation of the different types of stress-strain dependencies is made and a quantitative evaluation of the main parameters controlling transformational behavior of the alloys is carried out.

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Phase diagrams in the NiMnGa system under compression

Cited by 62 publications

References 8 publications

Entropy Change Caused by Martensitic Transformations of Ferromagnetic Shape Memory Alloys

Entropy Change Caused by Martensitic Transformations of Ferromagnetic Shape Memory Alloys

Shape memory ferromagnets

Stress-induced Martensitic Transformation and Superelasticity of Alloys: Experiment and Theory

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