Dependence of the martensitic transformation and magnetic transition on the atomic order in Ni–Mn–In metamagnetic shape memory alloys

Recarte, V.; Pérez-Landazábal, J.I.; Rodríguez-Velamazán, J. A.

doi:10.1016/j.actamat.2012.01.020

Cited by 91 publications

(69 citation statements)

References 37 publications

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“…In particular, the MT temperature T m increases and T C decreases with the increasing T quench for T quench < 900 K, and the opposite behavior, that is, a decrease on T m and a slight increase on T C , is observed when quenching from above 900K. The evolution of the transformation temperatures for T quench < 900 K is similar to that found in ternary NiMn-In, and can be ascribed to a decrease of the retained degree of L2 1 atomic order on increasing the quenching temperature [19]. On the other hand, assuming that quenching mainly affects the transformation temperatures due to the modification of atomic order, the behavior of T m and T C for T quench > 900 K could be related to an increase of the retained degree of atomic order with the increasing T quench , promoted by a high vacancies concentration at the quenching temperature that assist the ordering process, as in fact occurs in Ni-Mn-Ga and Ni-Fe-Ga alloys [20,27].…”

Section: Methodssupporting

confidence: 63%

“…On the other hand, assuming that quenching mainly affects the transformation temperatures due to the modification of atomic order, the behavior of T m and T C for T quench > 900 K could be related to an increase of the retained degree of atomic order with the increasing T quench , promoted by a high vacancies concentration at the quenching temperature that assist the ordering process, as in fact occurs in Ni-Mn-Ga and Ni-Fe-Ga alloys [20,27]. In any case, the net variations of the MT temperature (ΔT m ≈ 20 K) are much lower than those found in Ni-Mn-In subjected to exactly the same quenching treatments (ΔT m > 60 K) [19], thus pointing out either a lower effect of quenching on the retained atomic order or a lower influence of atomic order on the MT. From the latent heat estimated from the area bellow the peaks in Figure 1, Q, the corresponding entropy change at the MT has been calculated as ΔS = Q/T m .…”

Section: Methodsmentioning

confidence: 81%

“…The magnetic contribution, and therefore the entropy change at the MT, can be modified by the application of an external magnetic field [17] and, taking into account that the magnetic moment depends on the configurational ordering of the magnetic atoms in the crystal lattice, by the variation of the long-range atomic order. In this last respect, it has been recently shown that, for a given alloy composition, the atomic order can be easily modified in Ni-Mn-In alloys by means of different thermal treatments [18,19]. In particular, quenching from high temperatures (around the B2-L2 1 ordering temperature) allows to partially retain the low atomic order present at these temperatures, in such a way that the degree of long-range atomic order in the as-quenched alloys is lower than the equilibrium value allowed by the stoichiometry, which can be achieved after a slowly enough cooling.…”

Section: Introductionmentioning

confidence: 99%

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Long-Range Atomic Order and Entropy Change at the Martensitic Transformation in a Ni-Mn-In-Co Metamagnetic Shape Memory Alloy

Sánchez-Alarcos

Recarte

Pérez-Landazábal

et al. 2014

Entropy

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Abstract:The influence of the atomic order on the martensitic transformation entropy change has been studied in a Ni-Mn-In-Co metamagnetic shape memory alloy through the evolution of the transformation temperatures under high-temperature quenching and post-quench annealing thermal treatments. It is confirmed that the entropy change evolves as a consequence of the variations on the degree of L2 1 atomic order brought by thermal treatments, though, contrary to what occurs in ternary Ni-Mn-In, post-quench aging appears to be the most effective way to modify the transformation entropy in Ni-Mn-In-Co. It is also shown that any entropy change value between around 40 and 5 J/kgK can be achieved in a controllable way for a single alloy under the appropriate aging treatment, thus bringing out the possibility of properly tune the magnetocaloric effect.

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Section: Methodssupporting

confidence: 63%

Section: Methodsmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Long-Range Atomic Order and Entropy Change at the Martensitic Transformation in a Ni-Mn-In-Co Metamagnetic Shape Memory Alloy

Sánchez-Alarcos

Recarte

Pérez-Landazábal

et al. 2014

Entropy

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“…The atomic order degree of the L21 austenite can be modified by means of thermal treatments: atomic disorder can be forced by quench from temperatures around the B2↔L21 transition, and progressive ordering occurs by ageing at temperatures at which atomic diffusion is possible, as proven by neutron diffraction experiments in several Ni-Mn-based alloys [18,21,22].…”

Section: Introductionmentioning

confidence: 99%

Contributions to the Transformation Entropy Change and Influencing Factors in Metamagnetic Ni-Co-Mn-Ga Shape Memory Alloys

Seguı́¹,

Cesari²

2014

Entropy

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Ni-Co-Mn-Ga ferromagnetic shape memory alloys show metamagnetic transition from ferromagnetic austenite to paramagnetic (or weak-magnetic) martensite for a limited range of Co contents. The temperatures of the structural and magnetic transitions depend strongly on composition and atomic order degree, in such a way that combined composition and thermal treatment allows obtaining martensitic transformation (MT) between any magnetic state of austenite and martensite. The entropy change ΔS measured in the magnetostructural transition comprises a magnetic contribution which depends on the type and degree of magnetic order of the related phases. Consequently, both the magnetization jump across the MT (ΔM) and ΔS are composition and atomic order dependent. Both ΔS and ΔM determine the effect of applied magnetic fields on the MT, hence knowledge and understanding of their behavior can help to approach the best conditions for magnetic field induced MT and related effects. In previous papers, we have reported findings regarding the behavior of the transformation entropy in relation to composition and atomic order in Ni50−xCoxMn25+yGa25−y (x = 3-8, y = 5-7) alloys. In the present paper we will review our recent results, summarizing the key findings and drawing general conclusions regarding the magnetic contribution to ΔS and the effect of different factors on the magnetic and structural properties of these metamagnetic alloys. OPEN ACCESSEntropy 2014, 16 5561

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“…Substantial experimental and numerical work has been carried out on investigating the the order-disorder transition, long-range ordering and effect of ordering on the phase transformation characteristics in various shape memory alloys [40][41][42] fig. 8.…”

Section: Effect Of Configurational Disordermentioning

confidence: 99%

Stability analysis of the martensitic phase transformation inCo2NiGaHeusler alloy

et al. 2015

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Phase competition and the subsequent phase selection are important characteristics of alloy systems exhibiting numerous states of distinct symmetry but comparable energy. The stoichiometric Co 2 NiGa Heusler alloy exhibits a martensitic transformation with concommitant reduction in symmetry from a austentic L2 1 phase (cubic) to a martensitic L1 0 phase (tetragonal). A structural search was carried out for this alloy and it showed the existence of a number of structures with monoclinic and orthorhombic symmetry with ground state energies comparable to and even less than that of the L1 0 structure, usually reported as the ground state at low temperatures. We describe these structures and focus in particular on the structural transition path from the L2 1 to tetragonal and orthorhombic structures for this material. Calculations were carried out to study the Bain (L2 1 − L1 0 ) and Burgers (L2 1 − hcp) transformations. The barrierless Burgers path yielded a stable martensitic phase with orthorhombic symmetry (O) with energy much lower-beyond the expected uncertainty of the calculation methods-than the known tetragonal L1 0 martensitic structure. This low energy structure (O) has yet to be observed experimentally and it is thus of scientific interest to discern the cause for the apparent discrepancy between experiments and calculations. It is postulated the the Co 2 NiGa Heusler system exhibits a classic case of the phase selection problem: although the unexpected O phase may be relatively more stable than the L1 0 phase, the energy barrier for the (L2 1 − O) transformation may be much higher than the barrier to the (L2 1 − L1 0 ) transformation. To validate this hypothesis, the stability of this structure was investigated by considering the contributions of elastic, vibrational effects, configurational disorder, magnetic disorder and atomic disorder. The calculations simulating the effect of magnetic disorder/ high temperature as well as the atomic disorder simulations showed that the transformation from L2 1 to L1 0 is favored over the Burgers path at high temperatures (large magnetic disorder). These conditions are prevalent upon cooling the material from high temperatures (the usual synthesis route), and this provides a plausible explanation why L1 0 and not the O phase is observed. Other ground states (not observed in experiments but predicted through calculations) are ruled out in terms of symmetry relations as well as through considerations of elastic barriers to their nucleation.

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Dependence of the martensitic transformation and magnetic transition on the atomic order in Ni–Mn–In metamagnetic shape memory alloys

Cited by 91 publications

References 37 publications

Long-Range Atomic Order and Entropy Change at the Martensitic Transformation in a Ni-Mn-In-Co Metamagnetic Shape Memory Alloy

Long-Range Atomic Order and Entropy Change at the Martensitic Transformation in a Ni-Mn-In-Co Metamagnetic Shape Memory Alloy

Contributions to the Transformation Entropy Change and Influencing Factors in Metamagnetic Ni-Co-Mn-Ga Shape Memory Alloys

Stability analysis of the martensitic phase transformation inCo2NiGaHeusler alloy

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