Boosting Caloric Performances of Ni-Co-Mn-Ti Shape Memory Alloy for Multi-Scenario Refrigeration by Spark Plasma Sintering

In this study, Ni₃₇Co₁₃Mn_{33.5+<i>x</i>}Ti_{16.5-<i>x</i>} alloys with different particle sizes (75-150 μm, 50-75 μm, 0-50 μm) were successfully fabricated using spark plasma sintering under different processing conditions. By adjusting the composition of alloy and particle size, a significant transformation entropy change and the generation of a suitable amount of second phases along the grain boundaries were achieved in the SPS Ni₃₇Co₁₃Mn_34.5Ti_15.5 alloy with a particle size range of 0-50 μm. The mechanical properties of this optimized alloy were excellent, exhibiting a compressive strength of 2005 MPa and a fracture strain of 27%. Furthermore, under a loading rate of 0.28 s^-1, the alloy demonstrated an adiabatic temperature change of up to 34.2 K. In addition, the alloy also exhibited a barocaloric effect under low-pressure conditions, achieving a substantial entropy change of 16.1 J·kg^-1·K^-1 and an estimated adiabatic temperature change of 11.2 K under 100 MPa pressure. Through these results, SPS Ni₃₇Co₁₃Mn_34.5Ti_15.5 alloy is proved to be a potential candidate for solid-state refrigeration applications.