Entropy change linked to the martensitic transformation in metamagnetic shape memory alloys

The magnetic contribution to the martensitic transformation entropy change plays a crucial role in the transition properties of metamagnetic shape memory alloys. This contribution leads to a common dependence of the total entropy change at the structural transformation, ΔStr, on the normalized tempe...

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Bibliographic Details
Published in:Acta materialia 2012-04, Vol.60 (6-7), p.3168-3175
Main Authors: Recarte, V., Pérez-Landazábal, J.I., Sánchez-Alarcos, V., Zablotskii, V., Cesari, E., Kustov, S.
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Martensitic phase transformation
Metals. Metallurgy
Metamagnetic shape memory alloys (MSMAs)
Thermodynamics
Transformation entropy
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Summary:The magnetic contribution to the martensitic transformation entropy change plays a crucial role in the transition properties of metamagnetic shape memory alloys. This contribution leads to a common dependence of the total entropy change at the structural transformation, ΔStr, on the normalized temperature difference δAtr=(TCA-Ttr)/TCA (where TCA is the Curie temperature of the austenitic phase and Ttr is the transformation temperature) whose main feature is a decrease in ΔStr with increasing δAtr. A phenomenological model based on a Bragg–Williams approximation has been proposed to describe the observed behaviour in terms of the evolution of the magnetic contribution to the total entropy change. The proposed approximation provides a good fitting between predicted and experimental entropy changes obtained for different Ni–Mn-based alloy systems.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2012.02.022