Author: JUAN PABLO RAMON CAMARILLO GARCIA
"Se fabricaron aleaciones tipo Heusler de los sistemas Ni-Mn-In-X (X= Cu, Cr y Ga) que presentan transformación martensítica en un intervalo de temperatura cercano a la temperatura ambiente. La síntesis de las aleaciones se realizó utilizando un horno de arco eléctrico con base refrigerada. Las aleaciones fueron caracterizadas por difracción de rayos X, calorimetría diferencial de barrido convencional y en presencia de campo magnético, magnetometría vibracional; y mediciones de longitud en función de la temperatura a esfuerzo constante. En estas aleaciones multicalóricas se determinó y comparó el cambio de entropía generado por la aplicación de un campo magnético de hasta 6 T y el cambio de entropía inducido por un esfuerzo de hasta 100 MPa. Los valores más altos de cambios de entropía inducidos fueron +27 JK-1kg-1 y -34 JK-1kg-1 para el efecto magnetocalórico y elastocalórico, respectivamente. En algunas aleaciones destacadas se determinaron además las variaciones de temperatura adiabática inducida por campo magnético o esfuerzo uniaxial, con valores máximos de -2.8 K a ?0?H = 1.5 T y -4.9 K a ?? = -100 MPa, respectivamente."
"In this work ferromagnetic Heusler alloys from the Ni-Mn-In-X (X=Cu, Cr and Ga) systems have been synthetized showing martensitic transformation in the temperature range nearby to room temperature. The alloys were synthesized using an electric arc furnace with cooled crucible. The characterization in the alloys includes x ray diffraction, conventional differential scanning calorimetry (DSC) and DSC applying magnetic field, vibrational sample magnetometry and measurements of length as function of temperature and constant stress. In these multicaloric alloys, the values of the magnetic entropy change applying magnetic field up to 6 T and the stress induced entropy change for stress up to 100 MPa were found and compared. The maximum values exhibited by the alloys are +27 JK-1kg-1 and -34 JK-1kg-1 for the magnetocaloric effect and elastocalóric effect, respectively. In the outstanding alloys, measurements of the adiabatic temperature change induced by magnetic field and uniaxial applied stress were carried out showing maximum values of -2.8 K at ?0?H = 1.5 T and -4.9 K at ?? = -100 MPa, respectively."
Transformación martensítica Cambio de entropía inducido por campo magnético Cambio de entropía inducida por esfuerzo uniaxial Cambio de temperatura adiabático INGENIERÍA Y TECNOLOGÍA CIENCIAS TECNOLÓGICAS TECNOLOGÍA DE MATERIALES TECNOLOGÍA DE MATERIALES
"Se realizó un estudio del efecto elastocalórico en las aleaciones con memoria de forma Ni48.6Mn31.0In20.4 y Ni47.7Mn31.2Ga21.1. El estudio se realizó durante la transformación martensítica aplicando esfuerzo en compresión. La aleación Ni48.6Mn31.0In20.4 fue sintetizada mediante horno de arco y tratada térmicamente para homogeneización y ordenamiento químico. En ambas aleaciones se observó una dependencia en el cambio de entropía máxima alcanzada y capacidad refrigerativa en función del esfuerzo aplicado. La aleación Ni47.7Mn31.2Ga21.1 muestra una transformación intermartensítica, la cual contribuye notablemente en el cambio de entropía y capacidad refrigerativa respecto a la transformación únicamente martensítica. Se encontró que la aplicación de esfuerzo en compresión modifica la capacidad refrigerativa (RCP) obtenida a través del efecto elastocalórico. Se determinaron valores de RCP de 26.9 J/kg a 52.4 MPa y 33.2 J/kg a 13.7MPa para las aleaciones con Indio y Galio respectivamente."
"A study of the elastocaloric effect has been carried out on Ni48.6Mn31.0In20.4 and Ni47.7Mn31.2Ga21.1 memory shape alloys. Measurements were performed during the martensistic transformation applying compression stresses. Ni48.6Mn31.0In20.4 alloy was elaborated by arc melting and was heat treated for homogenization and for chemical ordering. Both alloys have shown dependence between the maximum entropy change achieved and the relative cooling power with applied stress. The Ni47.7Mn31.2Ga21.1 alloy exhibits an intermartensitic transformation, which modifies significantly the entropy change and relative cooling power compared to the martensitic transformation only. It was found that the application of a compression stress modifies the relative cooling power (RCP) due the elastocaloric effect. Values of RCP were calculated for Ni48.6Mn31.0In20.4 and Ni47.7Mn31.2Ga21.1 as 26.9 J/kg at 52.4 MPa and 33.2 J/kg at 13.7MPa respectively."
"Heusler-type Ni-Mn-based metamagnetic shape memory alloys (MetaMSMAs) are promising candidates for magnetic refrigeration. To increase heat exchange rate and efficiency of cooling, the material should have a high surface/volume ratio. In this work, the typical Ni50Mn35In15 MetaMSMA was selected to fabricate thin ribbons by melt-spinning. The characteristic transformations of the ribbons were determined by calorimetry, X-ray diffraction, scanning electron microscopy and thermomagnetization measurements. The inverse and conventional magnetocaloric effects (MCEs) associated with the martensitic transformation (MT) and the ferromagnetic transition of the austenite (TCA), respectively, were measured directly by the adiabatic method (Delta T-ad) and indirectly by estimating the magnetic entropy change from magnetization measurements. It is found that the ribbons exhibit large values of Delta T-ad = -1.1K at mu(0)Delta H = 1.9 T, in the vicinity of the MT temperature of 300K for inverse MCE, and Delta T-ad = 2.3K for conventional MCE at TCA = 309 K. This result strongly motivates further development of different MetaMSMA refrigerants shaped as ribbons. Published by AIP Publishing."
"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 ?0?H?=?5?T) and Curie temperatures of austenite, TCA, and martensite, TCM (TCA?=?309?K and TCM = 199?K) compared with the B2-ordered single phase ribbons (?SM?=?11.3?J/kgK for ?0?H?=?5?T; TCA = 293?K; TCM?=?178?K) obtained at higher cooling rates (40 and 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 second-order 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."
ELENA VILLA CHRISTIAN OMAR AGUILAR ORTIZ Adelaide Nespoli Pablo Álvarez Alonso JUAN PABLO RAMON CAMARILLO GARCIA Daniel Salazar Jaramillo Francesca Passaretti Horacio Flores Zúñiga Hideki Hosoda Volodymyr Chernenko (2019)
"In the present work, the structural, mechanical and shape memory properties of Ni55Fe16Ga29 (at.%) melt-spun ribbons have been studied with a prospective of application in the elastocaloric devises. Particularly, a special thermo-mechanical treatment, consisting in the thermal aging under constant external stress, was elaborated to control the residual internal stress generated due to the melt-spinning processing and improve thermomechanical and superelastic responses of the ribbon. The stress-induced entropy change was evaluated for the ribbon with improved thermomechanical properties."
"Magnetic Shape Memory Alloys exhibit multifunctional properties due the martensitic transformation (MT) and accompanying changes in the magnetic subsystem. In this work, melt spun ribbons of nominal composition Ni55Fe16Ga29 (R1) and Ni50Mn40Sn10 (R2) have been produced and characterized by the calorimetric, thermomechanical, mechanical, microscopic and X-ray measurements. The effect of short annealing on MT and thermo-mechanical properties is rather modest and in the case of R2 enhances its brittleness. R1 and R2 as-spun ribbons show MT at TM ~ 340 K and ~ 420 K, respectively. The strain-stress curves for Ni-Fe-Ga in austenitic phase indicate good visco-elastic properties, although the superelastic effect was not well pronounced. Ni-Fe-Ga as-cast and annealed samples, as well as the as-cast Ni-Mn-Sn ribbons, present a shape memory effect with an anomalous contraction and elongation at low external stresses in the course of the forward and reverse MT, consequence of the compressive internal stresses."
"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 L2(1) 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  perpendicular to the cooled surface. The elastocaloric effect was determined by direct measurements of the adiabatic temperature change (Delta T-ad(me)), 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 310K by applying moderate stresses of 50, 75, and 100 MPa in the , , and  directions. A strong interrelation was found in the cyclic Delta T-ad(me) values of -3.9, -2.0, and -1.3K after unloading a compressive stress of 100 MPa applied mainly in the , , and  directions, respectively."
"We report a giant elastocaloric effect near room temperature in a polycrystalline Ga-doped Ni-Mn-In ferromagnetic shape-memory alloy. The elastocaloric effect has been quantified by measuring both isothermal stress-induced entropy changes and adiabatic stress-induced temperature changes. A reproducible maximum entropy change,Delta S-rev similar or equal to 25 J . K-1 . kg(-1), upon cycling across the martensitic transition was obtained by application of a compressive stress of 100MPa. The corresponding maximum amount of cooling, Delta T-adi similar or equal to -4.9K, was measured when this stress was rapidly removed. These values are comparable with those reported for giant magnetocaloric materials, which are induced by application and release of a high magnetic field. Therefore, the studied material is a good candidate to be used in solid-state refrigeration devices based on the elastocaloric effect."