Thermal and Structural Analysis of Mn49.3Ni43.7Sn7.0 Heusler Alloy Ribbons

Abstract

Abstract:The martensitic transformation and the solidification structures of Mn49.3Ni43.7Sn7.0 alloy ribbons prepared by melt-spinning were investigated by means of scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. In those experiments special attention was given to melt spinning processing parameters such as the linear surface speed of the copper wheel rotating, the injection overpressure and the distance between wheel and injection quartz tube. Transformation entropy was found higher when increasing linear surface speed or the distance from injection point to wheel. The resulting samples showed chemical compositions close to the nominal ones and, at room temperature, crystallized in a monoclinic single-phase martensite with 14M modulation (without a significant variation in the cell parameters). Strong dependence of ribbon thickness on processing parameters was found. The average grain size varied between 1.6 and 6.6 μm, while the start temperature of the martensitic temperature varied from 394 to 430 K.

Impact of annealing on martensitic transformation of Mn50Ni42.5Sn7.5 shape memory alloy

“…The structure of martensite obtained in both alloys is identical to the structure observed in melt spun ribbons with similar composition [4]. It must be remarked that no detected secondary phase could be adjusted to the obtained XRD patterns.…”

“…Heusler-based Mn-Ni shape memory alloys have received increasing interest in technological applications, due to their potential functional properties during martensitic transformation (MT). This transition is from a cubic austenitic phase L21 or B2 at high temperature to a martensitic phase, whose structure can be L10, 10M and 14M at low temperature [1][2][3][4]. Their properties make them of particularly interest for improving of new magnetic actuators, magnetic sensors and refrigerants for attractive refrigeration [5].…”

Magnetic properties, martensitic and magnetostructural transformations of ferromagnetic Ni–Mn–Sn–Cu shape memory alloys

“…It is important to note that the theoretical curves fit properly with the experimental ones excepting for the highest of certain peaks. This minor mismatch in the altitude of peaks is conceivably due to the anisotropy and texture effect [15].for that, the degree of B2 and L21 ordering in the alloys was assessed using these relations [16]…”

Martensitic Transformation and Crystalline Structure of Ni50Mn50−xSnx Melt-Spun Heusler Alloys

“…These ribbons are obtained as flakes because they are obtained at a high solidification rate (10 6 K s −1 ) and are also fragile and brittle. The micrographs (free surface) of alloys Sn10, Sn11, Sn12, and Sn13 are shown in Figure 3b1-b4, respectively These flakes have a coarse granular microstructure (average grain size value around 1-2 µm); the average grain size values are well below those obtained in bulk alloys (10 to Crystals 2020, 10, 853 5 of 11 20 µm) [17]. The micrographs (cross-sections normal to ribbon plane) for Sn10, Sn11, Sn12, and Sn13 alloys can be observed respectively in Figure 3c1-c4.…”

“…In references [22,29], the temperatures are lower/higher for Sn13 and Sn10 alloys, respectively. It is known that the shape, geometry, and processing parameter (as the wheel speed) influence the characteristic temperatures [17,30]. For it, it is recommended to compare alloys produced at the same conditions or to be careful in the comparative analysis.…”