Influence of Structural Defects on the Properties of Metamagnetic Shape Memory Alloys

Abstract

The production of μ-particles of Metamagnetic Shape Memory Alloys by crushing and subsequent ball milling process has been analyzed. The high energy involved in the milling process induces large internal stresses and high density of defects with a strong influence on the martensitic transformation; the interphase creation and its movement during the martensitic transformation produces frictional contributions to the entropy change (exothermic process) both during forward and reverse transformation. The frictional contribution increases with the milling time as a consequence of the interaction between defects and interphases. The influence of the frictional terms on the magnetocaloric effect has been evidenced. Besides, the presence of antiphase boundaries linked to superdislocations helps to understand the spin-glass behavior at low temperatures in martensite. Finally, the particles in the deformed state were introduced in a photosensitive polymer. The mechanical damping associated to the Martensitic Transformation (MT) of the particles is clearly distinguished in the produced composite, which could be interesting for the development of magnetically-tunable mechanical dampers.

High functional 3D printed PCL/FSMA magnetic composites

“…Figure 2(a) shows the DSC thermograms corresponding to the Ni 45 Mn 36.7 In 13.3 Co 5 MPs obtained on a heating-cooling thermal cycle. Exothermic and endothermic reactions which are related to the development of the forward-and the reverse-MT can be observed at around 310 K (cooling) and around 330 K (heating), respectively; in agreement with previous works [57]. Consequently, the appearance of the first order nature of the MT in the MPs, after the milling process [57], is confirmed by the thermal hysteresis between cooling and heating runs in the thermograms.…”

“…Exothermic and endothermic reactions which are related to the development of the forward-and the reverse-MT can be observed at around 310 K (cooling) and around 330 K (heating), respectively; in agreement with previous works [57]. Consequently, the appearance of the first order nature of the MT in the MPs, after the milling process [57], is confirmed by the thermal hysteresis between cooling and heating runs in the thermograms. In addition, a change in the base-line both during the heating and cooling runs at around 380 K can be also observed which is related to the high order transition promoted by the Curie transition (T c ) of the MPs [22,23,57].…”

“…Consequently, the appearance of the first order nature of the MT in the MPs, after the milling process [57], is confirmed by the thermal hysteresis between cooling and heating runs in the thermograms. In addition, a change in the base-line both during the heating and cooling runs at around 380 K can be also observed which is related to the high order transition promoted by the Curie transition (T c ) of the MPs [22,23,57].…”

Shape Memory Alloys 2020

“…In this context, Nakamura et al [3] provided an interesting investigation of a Co 64 V 15 (Si 21−x Al x ) alloy and proposed it as a new multifunctional magnetic material. Another remarkable group of ferromagnetic SMAs are the so-called metamagnetic ones and, paying attention to their critical role in material properties, the influence of structural defects in Ni 45 Co 5 Mn 37 In 13 alloy was investigated by Pérez-Landazábal et al [4]. In addition, keeping in mind potential applications, the refrigeration capacity of micro-particles of this alloy as well as the damping properties of the designed SMA-polymer composites have been tested.…”

Testing the Applicability of 119Sn Mössbauer Spectroscopy for the Internal Stress Study in Ternary and Co-Doped Ni-Mn-Sn Metamagnetic Alloys

“…As a result, the use of microparticles is attracting increasing interest as an effective method to overcome the drawbacks of bulk samples [10]. However, in micro-and nano-regime the control of internal stresses and defects becomes crucial to properly tune the desired multifunctional properties [11,12]. During thermal cycling, the retained residual stress degrades the MT, increasing its hysteresis and its irreversibility [13,14].…”