Giant elastocaloric effect in directionally solidified Ni-Mn-In magnetic shape memory alloy

Achieving a broad refrigeration temperature region through the combination of successive caloric effects in a multiferroic Ni50Mn35In15 alloy

Giant low-field magnetocaloric effect in a textured Ni45.3Co5.1Mn36.1In13.5 alloy

Microstructure and the correlated martensitic transformation of melt spinning Ni50Mn29Ga21−xTbx (x = 0–1) ribbons

Enhanced elastocaloric effect and mechanical properties of Fe-doped Ni–Mn–Al ferromagnetic shape memory alloys

Banded-like morphology and martensitic transformation of dual-phase Ni–Mn–In magnetic shape memory alloy with enhanced ductility

The magnetic anisotropy energy (MAE) in the ferromagnetic shape memory alloys (FSMAs) provides the driving forces to obtain large magnetic field induced strain (MFIS) by rearranging the martensitic variants. However, to date, no significant MAE was observed in the new class of Ni-Mn-Z (Z = In, Sn, Sb) metamagnetic shape memory alloys (MSMAs). Here, we report a significant magnetic anisotropy in Ni48Mn35In17 Heusler alloy with a [110]A fiber texture prepared by the directional solidification. In this case, when the applied magnetic field is along the [110]A direction, a larger magnetization change is obtained compared with that of the randomly oriented samples, which increases the driving forces for the magnetically induced martensitic transformation (MIMT). In contrast, along the [110]A direction, the magnetocaloric effect (MCE) is enhanced by 60 pct, the MFIS is improved by 20 pct, and the critical field for the MFIS is reduced by 0.5 T. Such a peculiar magnetic behavior could be well explained by a proposed model on the viewpoint of the transformation of ferromagnetic austenite phase. Furthermore, considering the thermodynamics aspects, we demonstrate that two main magnetic energies of the Zeeman energy and the MAE in the MSMAs assist each other to promote the MIMT, instead of opposing each other in the FSMAs. This discovery of the strong magnetic anisotropy in highly textured polycrystals provides a feasible route to enhance the MIMT, and new insights to design and prepare the Ni-Mn-based Heusler alloys for practical applications.

On the Driving Forces of Magnetically Induced Martensitic Transformation in Directionally Solidified Polycrystalline Ni-Mn-In Meta-Magnetic Shape Memory Alloy with Structural Anisotropy

The invention discloses a zone melting and directional solidifying method used for a volatile element alloy. The method comprises the following steps of: selecting raw metals according to alloy components; matching the raw metals selected; smelting into an initial alloy bar; transferring into a directional solidifying crucible; fully filling slag forming constituents into a clearance between the initial alloy bar and the directional solidifying crucible; transferring the directional solidifying crucible into a directional solidifying device; and heating through an induction coil to realize zone melting of the initial alloy bar and the slag forming constituents, wherein volatile components of the alloy are prevented from volatilizing through the molten slag forming constituents, and the slag forming constituents react with impurities in the alloy to generate molten slag; the directional solidifying device downwards moves relative to the induction coil to accomplish the zone melting and directional solidifying of the whole initial alloy bar; the molten slag is continuously generated and floats upwards, and then stops on the top of the alloy and finally is removed. By adopting such directional solidifying method, the consumption in volatilizing of the volatile element of the alloy can be greatly reduced during solidifying, the impurities and air pores are removed at the same time, and the alloy with components approaching to design components and having a uniform distribution an axial direction can be obtained.

Zone melting and directional solidifying method used for volatile element alloy

High Cr steel (X12CrMoWVNbN10-1-1) ingots were prepared by thermal control by varying three parameters: the melt pouring temperature, the mold temperature and the melt superheating temperature. The effects of these parameters on the macro-/micro-structure of the ingots were investigated through a group of orthogonal experiments. The results showed that superheating temperature was the dominating parameter that affects the grain size and fraction of delta ferrite. The optimized parameters for the sound ingot were 1 893 K for superheating temperature, 1 073 K for mold temperature and 1 873 K for pouring temperature. Under that condition, the ingot was composed of fine equiaxed grain with a radius of 1.1 mm, and the fraction of the delta ferrite was less than 2%. Mechanisms that explain the increment in the proportion of the equiaxed fraction and the grain refinement were proposed, and the mechanisms for the delta ferrite reduction were explained.

Yujin Huang

Papers

Banded-like morphology and martensitic transformation of dual-phase Ni–Mn–In magnetic shape memory alloy with enhanced ductility

On the Driving Forces of Magnetically Induced Martensitic Transformation in Directionally Solidified Polycrystalline Ni-Mn-In Meta-Magnetic Shape Memory Alloy with Structural Anisotropy

Zone melting and directional solidifying method used for volatile element alloy

Grain Refinement and Delta Ferrite Reduction of High Cr Steel Ingots by Thermal Control

Internal friction behaviors of Ni-Mn-In magnetic shape memory alloy with two-step structural transformation