Meta-magnetic shape memory alloys (MMSMAs) exhibit multi-physical couplings across a reversible first-order martensitic transition which leads to their potential applications in solid-state cooling, thermally or magnetically driven precision actuation, energy harvesting, and magnetic memory storage. Through their magneto-structural transitions and simultaneous transformation latent heat, MMSMAs are capable of the magnetocaloric effect (MCE) at two distinct operating temperatures (i.e., the critical martensitic transformation temperature and the ferromagnetic Curie point of either the austenite or martensite phase). In this study, the Refrigeration Capacity (RC) and Coefficient of Refrigeration Performance (CRP) in MMSMAs are shown to depend on the critical martensite transformation temperatures and, by extension, uniaxial mechanical stress. A loading sequence, namely the stress-assisted magnetic field-induced phase transformation (SAMFIT) is described, whereby mechanical stress and magnetic field are applied to an MMSMA specimen in sequence to effectively increase the thermal operating range and CRP for a single MMSMA composition.

Shape memory alloys (SMAs) have gained attention in recent years as a powerful mechanism for mechanical actuation in space applications. One issue facing this technology is that most commercially available SMAs yield a high amount of energy loss due to their relatively large hysteresis, which can translate into an increase in the overall cost of the mission. Low hysteresis shape memory alloys (LHSMAs), which exhibit a much narrower hysteresis, are needed to minimize this energy loss. Previous studies have shown that elemental additions of Cu, Co, and Pd to the NiTi-based SMA can result in shape memory alloys with a much lower thermal hysteresis, due to better phase compatibility. This present work investigated seven alloy compositions to identify LHSMAs with less than 20 °C hysteresis and develop processing routes for these LHSMAs to determine potential candidates for space actuation applications.