(V) Additive Manufacturing Enabling Elastocaloric Materials with Fatigue-Resistance and High-performance

Elastocaloric cooling, which exploits superelastic transitions of shape memory alloys to pump heat, has recently emerged as a frontrunner in alternative cooling technologies. Despite its intrinsic high efficiency, elastocaloric materials exhibit hysteresis associated with input work, a common attribute of caloric cooling materials. Here, we employ additive manufacturing to design highly-reversible superelastic transition pathways at a microscopic level in elastocaloric Ni–Ti. Through rapid cooling and high-precision compositional tuning, we fabricate Ni–Ti-based nanocomposites with unique curved nano-interfaces, which give rise to quasi-linear stress-strain behaviors with unusually narrow hysteresis, resulting in enhancement in the materials coefficient of performance by a factor of four to seven. Our nanocomposite NiTi is stable over 1 million cycles of superelastic transitions, opening the door for their direct implementation in cooling devices where additive manufacturing now provides much-needed geometrical design flexibility in elastocaloric system components which serve as both refrigerants and heat exchangers. We propose a functional fatigue model to capture the degradation behaviors of elastocaloric materials using a dissipation percentage of input work and extend to magnetocaloric, electrocaloric, and barocaloric materials. We will show the establishment of its applicability as a universal rule to predict the functional fatigue life of all caloric materials.