Giant Elastocaloric Effect and Improved Cyclic Stability in a Directionally Solidified (Ni50Mn31Ti19)99B1 Alloy

Superelastic shape memory alloys with an integration of large elastocaloric response and good cyclability are crucially demanded for the advancement of solid-state elastocaloric cooling technology. In this study, we demonstrate a giant elastocaloric effect with improved cyclic stability in a <001>A textured polycrystalline (Ni50Mn31Ti19)(99)B-1 alloy developed through directional solidification. It is shown that large adiabatic temperature variation (|Delta T-ad|) values more than 15 K are obtained across the temperature range from 283 K to 373 K. In particular, a giant Delta T-ad up to -27.2 K is achieved by unloading from a relatively low compressive stress of 412 MPa at 303 K. Moreover, persistent |Delta T-ad| values exceeding 8.5 K are sustained for over 12,000 cycles, exhibiting a very low attenuation behavior with a rate of 7.5 x 10(-5) K per cycle. The enhanced elastocaloric properties observed in the present alloy are ascribed to the microstructure texturing as well as the introduction of a secondary phase due to boron alloying.