Giant magnetocaloric effect in melt-spun Ni-Mn-Ga ribbons with magneto-multistructural transformation

Qian

Applied Physics Letters

et al. 2016

Ni-Mn-Ga-X microwires were produced by melt-extraction technique on a large scale. Their shape memory effect, superelasticity, and damping capacity have been demonstrated. Here, the excellent magnetocaloric effect was revealed in Ni-Mn-Ga-Cu microwires produced by melt-extraction and subsequent annealing. The overlap of the martensitic and magnetic transformations, i.e., magnetostructural coupling, was achieved in the annealed microwires. The magnetostructural coupling and wide martensitic transformation temperature range contribute to a large magnetic entropy change of −8.3 J/kg K with a wide working temperature interval of ∼13 K under a magnetic field of 50 kOe. Accordingly, a high refrigeration capacity of ∼78 J/kg was produced in the annealed microwires.

supporting

confidence: 49%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Magnetostructural coupling and magnetocaloric effect in Ni-Mn-Ga-Cu microwires

Qian

Applied Physics Letters

et al. 2016

“…6,7 The austenite phase becomes ferromagnetic below T = T C (A) and the A-M transition is often accompanied by an abrupt decrease of magnetization at T M . [8][9][10] In Ni 2+x Mn 1−x Ga, T C decreases, while T M increases, with increasing Ni content, for x = 0.19 both the structural and magnetic phase transition coincide. 11 Externally applied magnetic fields usually decrease T M , but the relative shift depends on the magnetic field strength as well as the choice of alloying element and Ni/Mn ratio.…”

Section: Introductionmentioning

confidence: 99%

Magnetic field dependence of electrical resistivity and thermopower in Ni50Mn37Sn13 ribbons

et al. 2015

We report magnetization, magnetoresistance (MR) and magnetothermopower (MTEP) of melt spun Ni 50 Mn 37 Sn 13 ribbons which exhibit an austentite to martensite phase transition at a temperature (T M ) ≈ 294 K. Upon cooling from 400 K, dcresistivity and thermopower show abrupt changes at T M , indicating a change in the electronic density of states. The thermopower is negative from 400 K down to 10 K. Application of a magnetic field of µ 0 H = 5 T decreases T M by 5 K and induces large negative MR (-23%) but positive MTEP (9%) near T M . While the MR is appreciable from T M down to 10 K, MTEP is significant only below 60 K (MR = -2.5% and MTEP = +300% at 10 K). The magnetic field dependence of resistivity and thermopower show either reversible or irreversible behavior near T M , depending on whether the sample is zero-field cooled or field-cooled, which indicates that the electronic band structure near T M is magnetic history dependent. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx

J. of Materi Eng and Perform

“…High-entropy alloys (HEAs) emerge as a novel research frontier in the metallic materials community (Ref [17][18][19][20]. Unlike traditional alloys, HEAs consist of at least five principal elements (5 to 35 at.% for each element) ( Ref 20).…”

Section: Introductionmentioning

confidence: 99%

Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

Wang

Lin

et al. 2016

Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe-x (x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with YangÕs proposition, the two alloys form simple solid solutions. The electronegativity difference (Dv) favors a formation of the solid solution when Dv £ 14.2. The hardness of AlCoCuFe-x (x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.