We have studied the correlation between the elastocaloric effect and the crystallographic direction where a uniaxial stress is applied in a textured polycrystalline Ni-Mn-In-Cr ferromagnetic shape memory alloy; this alloy displays martensitic transformation around room temperature and presents an L21 cubic structure in the austenite phase. The texture in the material was induced by simple arc melting synthesis; using inverse pole figures, a favored grain growth was shown in the direction [001] perpendicular to the cooled surface. The elastocaloric effect was determined by direct measurements of the adiabatic temperature change (ΔTadme), while compressive stress was applied and released; hereby, it has been shown that it is possible to exploit the columnar growth texture in order to obtain a large and reversible elastocaloric effect. The reversible elastocaloric response was measured between 280 and 310 K by applying moderate stresses of 50, 75, and 100 MPa in the [001], [111], and [011] directions. A strong interrelation was found in the cyclic ΔTadme values of −3.9, −2.0, and −1.3 K after unloading a compressive stress of 100 MPa applied mainly in the [001], [111], and [011] directions, respectively.
Ni50Mn35In15 compound has become an archetype for investigating the functional properties of metamagnetic shape memory alloys. We have fabricated Ni50Mn35In15 melt spun ribbons to study the crystal structure, microstructure, martensitic transformation, magnetic properties and magnetocaloric effect as a function of the ribbon solidification rate controlled by the wheel speed. We have found that an increase of the cooling rate refines the alloy grain size, which, in turn, influences the chemical order of austenite phase and functional properties: ribbons produced at low wheel speed (10, 20 and 30 m/s) present majorly L21 structure associated with higher magnetic entropy change, ∆SM (up to 18.6 J/kgK for a magnetic field change of µ0∆H = 5 T) and Curie temperatures of austenite, TC A , and martensite, TC M (TC A = 309 K and TC M = 199 K) compared with the B2-ordered single phase ribbons (∆SM = 11.3 J/kgK for µ0∆H = 5 T; TC A = 293 K; TC M = 178 K) obtained at higher cooling rates ( 40and 50 m/s). Besides, we have also observed a correlation between the grain size reduction and a shift of the martensitic transformation to lower temperatures. Direct measurements of the adiabatic temperature change have been performed during both the first-and secondorder phase transitions. The results disclose the correlation between structural and magnetic properties of the ribbon and the wheel speed, which opens an innovative tool to adjust the transformation characteristics and magnetocaloric properties through the solidification rate control.
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