Abstract
Ni45Co5Mn40Sn10 Heusler alloy was fabricated with elemental powders, using a powder processing route of press and sinter, in place of vacuum induction melting or arc melting route. The effects of process parameters, such as compaction load, sintering time, and temperature, on the transformation characteristics and microstructures of the alloy were investigated. While the effect of compaction pressure was not significant, those of sintering time and temperature are important in causing or annulling martensitic transformation, which is characteristic of Heusler alloys. The processing condition of 1050 °C/24 h was identified to be favorable in producing ferromagnetic Heusler alloy. Longer durations of sintering resulted in an increased γ-phase fraction, which acts as an impediment to the structural transformation.
Highlights
Ni–Mn–X (X – Ga, Sn, In, Sb)-based ferromagnetic Heusler alloys are multifunctional materials on account of their multiferroic nature [1]
The reversibility of the transformations is uniquely identified with a shape memory effect (SME), either magnetic (MSME) or metamagnetic (MMSME)
In the former, strain recovery is by martensitic twin variants reorientation under an applied field as in Ni–Mn–Ga alloys [3], while in the latter, it is by a field-induced reverse transformation from the martensite phase back to parent austenite phase, as in other Ga-free alloys (e.g., Ni50 Mn34 In16 ) [3]
Summary
Ni–Mn–X (X – Ga, Sn, In, Sb)-based ferromagnetic Heusler alloys are multifunctional materials on account of their multiferroic nature [1] This has its origin in a couple of remarkable and reversible solid-state transformations, viz., the primary martensitic phase transformation and the secondary magnetic transition. The reversibility of the transformations is uniquely identified with a shape memory effect (SME), either magnetic (MSME) or metamagnetic (MMSME) In the former, strain recovery is by martensitic twin variants reorientation under an applied field as in Ni–Mn–Ga alloys [3], while in the latter, it is by a field-induced reverse transformation from the martensite phase back to parent austenite phase, as in other Ga-free alloys (e.g., Ni50 Mn34 In16 ) [3]. MSME [4] and other effects of magnetocaloric [5,6,7,8], magneto-resistance [9,10], exchange bias [11], and direct conversion of heat into electricity [12] are interconnected [2], which explains the multifunctional behavior
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