Functional stability of a ferromagnetic polycrystalline Ni2MnGa high temperature shape memory alloy

Azeem, M.A. and Jones, N.G. and Raghunathan, S.L. and Vorontsov, V.A. and Dye, D. (2017) Functional stability of a ferromagnetic polycrystalline Ni2MnGa high temperature shape memory alloy. Scripta Materialia, 130. pp. 274-277. ISSN 1359-6462 (https://doi.org/10.1016/j.scriptamat.2016.12.012)

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Abstract

Electrocaloric Ni2MnGa is of interest for solid state refrigeration applications, as well as a high temperature thermal shape memory alloy. Here, polycrystalline Ni54Mn25Ga21 is examined using in situ synchrotron X-ray diffraction. The initial martensite (Mf) and austenite (Af) finish temperatures were found to be 232 ° C and 298 ° C respectively. Mf was observed to decline by 8 ° C/cycle and Af increased by 1 ° C/cycle. Both below and surprisingly, above the Curie temperature, the application of an e.m.f. was found to affect the lattice parameters measured. A change in the thermal expansion of the two phases was found around the Curie temperature.

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