Shape memory and elastocaloric properties of melt-spun NiMn-based Heusler alloys

In the present work, towards further development of NiMn-based Heusler-type elastocaloric alloys a series of melt-spun ribbons have been prepared from three multicomponent Ni-Mn-Sn-based metamagnetic shape memory alloys (MetaMSMAs) and two multicomponent Ni-Mn-Ga-based ferromagnetic shape memory alloys (FSMAs). Their thermoelastic martensitic transformation (TMT), crystal structure and thermomechanical properties have been studied in detail. Whereas FSMAs ribbons showed a conventional stress-strain behavior at TMT and conventional elastocaloric effect (eCE), MetaMSMAs ribbons, in turn, exhibited highly pronounced inverse stress-strain and inverse eCE characteristics at TMT. The abnormal thermomechanical behavior of the MetaMSMA ribbons is produced by the presence of significant internal stresses due to appropriate amount of quenched-in defects resulting from the rapid solidification of melt-spun alloys. The results of the present study can serve as a guide for the design of new eCE-efficient materials in the form of ribbon.