52 / 2024-09-18 11:09:18

New opportunity for green refrigeration technology realized by the elastocaloric effect of NiTi shape memory alloys manufactured by additive manufacturing

Solid-state refrigeration,Elastocaloric effect,Shape memory alloys,Additive manufacturing

Solid-state refrigeration based on shape memory alloys (SMAs) has emerged as a green alternative to conventional vapor compression refrigeration with zero global warming potential. Bulk NiTi SMAs were synthesized in situ on a substrate using the laser-directed energy deposition (LDED) additive manufacturing technique, and XRD analyses showed that austenite with a B2 structure predominated at room temperature and diffraction peaks of the precipitated phase Ti2Ni were observed. Microstructural observations revealed that the grain morphology of the B2 phase was elongated along the building direction, the Ti2Ni phase was found to be diffusely distributed inside the grains of the B2 phase by EBSD analysis, and no apparent weaving structure was formed inside the NiTi SMAs. The stress-strain curves of the stress-loaded trained NiTi SMAs exhibit near-linear behavior, contrasting with the conventional fabrication technique that shows a pronounced phase transformation plateau. The NiTi SMAs were loaded to different maximum compressive stresses and unloaded rapidly. It was found that the maximum temperature drop increased with the maximum stress and exhibited a cooling characteristic of up to −2.7 ℃ when the stress of 1100 MPa was removed rapidly. The uniform distribution of the surface temperature reflects the homogeneity of the elastocaloric effect, enabling additive manufacturing techniques to realize the preparation of NiTi SMAs and to create new opportunities to drive the development of novel refrigeration technologies.