Magnetocaloric Response Of Non-Stoichiometric Ni2Mnga Alloys And The Influence Of Crystallographic Texture

Keywords

Magnetocaloric; NiMnGa alloy; Polycrystalline; Preferred orientation; Twinning

Abstract

Abstract Currently, there is significant interest in magnetocaloric materials for solid state refrigeration. In this work, polycrystalline Heusler alloys belonging to the Ni2+xMn1-xGa family, with x between 0.08 and 0.24, were evaluated for the purpose of finding composition(s) with an enhanced magnetocaloric effect (MCE) close to room temperature. Differential scanning calorimetry (DSC) was successfully used to screen alloy composition for simultaneous magnetic and structural phase transformations; this coupling needed for a giant MCE. The alloy with x = 0.16 showed an excellent match of transformation temperatures and exhibited the highest magnetic entropy change, ΔSM, in the as-annealed state. Furthermore, the MCE increased by up to 84% with a 2 Tesla (T) field change when the samples were thermally cycled through the martensite to austenite transformation temperature while held under a constant mechanical load. The highest ΔSM measured for our x = 0.16 alloy for a 2 T magnetic field change was -18 J/kg K. Texture measurements suggest that preferential orientation of martensite variants contributed to the enhanced MCE in the stress-assisted thermally cycled state.

Publication Date

7-15-2015

Publication Title

Acta Materialia

Volume

97

Number of Pages

245-256

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.actamat.2015.06.059

Socpus ID

84937565562 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84937565562

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