Effect of partial substitution of Fe by Mn in Ni55Fe19Ga26 on its microstructure and magnetic properties

•Effect of Mn in Ni55Fe19Ga26 on microstructure and MCE is presented.•Mn stabilizes 14M martensite in place of NM martensite.•Increasing Mn also leads to a drastic reduction in γ-phase content.•MCE shows significant improvement with increasing Mn.•A maximum value of ΔSM= −19.8J/kgK has been observed...

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Veröffentlicht in:Journal of alloys and compounds 2014-02, Vol.586, p.515-523
Hauptverfasser: Sarkar, Sudip Kumar, Biswas, Aniruddha, Babu, P.D., Kaushik, S.D., Srivastava, Amita, Siruguri, Vasudeva, Krishnan, Madangopal
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Sprache:eng
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Zusammenfassung:•Effect of Mn in Ni55Fe19Ga26 on microstructure and MCE is presented.•Mn stabilizes 14M martensite in place of NM martensite.•Increasing Mn also leads to a drastic reduction in γ-phase content.•MCE shows significant improvement with increasing Mn.•A maximum value of ΔSM= −19.8J/kgK has been observed at 9T for the Mn-10 alloy. Ni–Fe–Ga-based Ferromagnetic Shape Memory Alloys (FSMAs) show considerable formability because of the presence of a disordered FCC γ-phase, but they lack in magnetocaloric property. Addition of Mn has been explored as a way to improve their magnetocaloric property. The current study presents a detailed structural and magnetization analyses of a two-phase ternary Ni55Fe19Ga26 alloy and its quaternary counterparts obtained by partial replacement of Fe by Mn, Ni55Fe19−xMnxGa26 (x=2.5, 2.75, 3, 5, 10). Characterization of these alloys has been carried out using Optical and Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray (XRD) and Neutron Diffraction (ND), Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC) and DC magnetization measurement. Ni55Fe19Ga26 alloy shows predominantly non-modulated (NM) internally-twinned martensite, with traces of a modulated 14M martensite and the parent L21 phase along with the FCC γ-phase. Quaternary addition of Mn in partial replacement of Fe stabilizes14M martensite, drastically reduces the amount of γ-phase, keeps the martensitic transition temperatures unchanged, but raises TC considerably. Magnetocaloric effect improves significantly with increasing Mn-content and a maximum value of −19.8J/kgK for ΔSM has been observed at 9T for the alloy containing 10at.% Mn.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2013.10.057