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

In this study, Ni37Co13Mn33.5+xTi16.5–x 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 Ni37Co13Mn34.5Ti15.5 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 Ni37Co13Mn34.5Ti15.5 alloy is proved to be a potential candidate for solid-state refrigeration applications.