Mingfang Qian

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

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.

Enhanced magnetocaloric effect in Ni-Mn-Sn-Co alloys with two successive magnetostructural transformations

High magnetocaloric refrigeration performance requires large magnetic entropy change ΔSM and broad working temperature span ΔTFWHM. A fourth element doping of Co in ternary Ni-Mn-Sn alloy may significantly enhance the saturation magnetization of the alloy and thus enhance the ΔSM. Here, the effects of Co-doping on the martensite transformation, magnetic properties and magnetocaloric effects (MCE) of quaternary Ni47−xMn43Sn10Cox (x = 0, 6, 11) alloys were investigated. The martensite transformation temperatures decrease while austenite Curie point increases with Co content increasing to x = 6 and 11, thus broadening the temperature window for a high magnetization austenite (13.5, 91.7 and 109.1 A·m2/kg for x = 0, 6 and 11, respectively). Two successive magnetostructural transformations (A → 10 M and A → 10 M + 6 M) occur in the alloy x = 6, which are responsible for the giant magnetic entropy change ΔSM = 29.5 J/kg·K, wide working temperature span ΔTFWHM = 14 K and large effective refrigeration capacity RCeff = 232 J/kg under a magnetic field of 5.0 T. These results suggest that Ni40.6Mn43.3Sn10.0Co6.1 alloy may act as a potential solid-state magnetic refrigerant working at room temperature.

Dataset on enhanced magnetic refrigeration capacity in Ni–Mn–Ga micro-particles

The dataset presented in this paper is supporting the research article “Enhanced magnetic refrigeration capacity in Ni-Mn-Ga micro-particles” (Qian, et al., 2018) [1]. The martensite transformation temperature (Ms) and the Curie point (Tc) of the annealed alloys with nominal composition Ni55-xMn20+xGa25 (x = 0, 0.25, 0.5, 1, atomic percent, labeled as A1, A2, A3 and A4, respectively) varied with x, yielding a temperature difference Tc-Mc of 7.2 K at x = 0.5 (A3). The magnetization difference (ΔM) between the austenite and martensite, the field dependence of transformation temperature (ΔT/ΔH) and the thermal hysteresis loss of A3 and the according stress relief annealing (SRA) particles were demonstrated. The isothermal magnetization curves of A3 and the SRA particles were measured in order to determine the magnetocaloric effect.

Dataset on the microstructure Ni50Mn38Sb9Si3 alloy and compositions of Ni50Mn38Sb12−xSix (x=2.5, 3) ferromagnetic shape memory alloys

The data presented in this article is the supplementary data of Zhang et al. (2018) [1]. The Ni50Mn38Sb9Si3 alloy is annealed at 1223 K for 24 h and then quenched into ice water; while the Ni50Mn38Sb9.5Si2.5 alloy is annealed at 1173 K for 24 h and then quenched into ice water. The microstructure of the Ni50Mn38Sb9Si3 alloy indicates that a higher heat treatment temperature cannot prevent the formation of secondary phases. Furthermore, the composition of α phase is similar to the nominal composition of the alloy. On the other hand, the nominal concentration of Si atoms and heat-treatment temperature do not affect the compositions of the β and γ phases. For example, the compositions of the β and γ phases in the Ni50Mn38Sb9Si3 alloy are similar when annealed at 1223 K for 24 h and 1173 K for 24 h

Elastocaloric effects in ultra-fine grained NiTi microwires processed by cold-drawing

Efficient elastocaloric cooling in shape memory alloys requires a stable superelastic behavior in which high yield strength is needed. Here Ni50.4Ti49.6 microwires with diameter 130 μm and ultra-fine grains ∼30 nm were prepared by multi-step cold-drawing and low-temperature annealing. Enhanced cyclic stability of the elastocaloric effects induced by the superelastic training was demonstrated. The pre-trained microwire showed a stable ΔSe 43 J/(kg K) with a broad working temperature range ΔT ∼ 70 K. The superelastic trained microwire, with giant and stable ΔSe over a wide working temperature window, may act as a promising elastocaloric cooling material for minor-sized devices.