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Investigating elastocaloric effect of NiTi shape memory alloy fabricated by laser powder bed fusion technique
Elastocaloric materials are one of the main alternatives to conventional vapor compression for refrigeration systems. Shape memory alloys (SMA) are one category of these materials, which can exhibit the elastocaloric effect (eCE) as a result of reversible martensitic phase transformations when mechanically loaded and unloaded in an adiabatic state. Among SMAs, NiTi shape memory alloy has exhibited superior performance in eCE.
In our comprehensive study, we explored the eCE of NiTi manufactured using the Laser Powder Bed Fusion (LPBF) technique. Our investigation focused on the effect of building orientation on the elastocaloric response. To assess this, we fabricated samples with distinct building orientations: <001>, <011>, and <148>. Our findings underscore the pivotal role of building orientation in shaping the elastocaloric effect. Notably, parts with a <001> building orientation, characterized by the highest strain recovery, exhibited the highest elastocaloric performance, resulting in an adiabatic temperature change of 10.5°C.
Furthermore, we introduce a new porous structure, a pioneering contribution to the field, to enhance efficiency by elevating heat transfer capabilities and reducing the requisite loading for eCE. These porous structures, diamond, gyroid, and primitive configurations, were fabricated through LPBF. In compression loading, the diamond structure emerged as the standout performer, demonstrating adiabatic temperature of 5.31°C, signifying the highest eCE among the two other porous structures. Impressively, the diamond sample also demonstrated the Coefficient of Performance (CoP) of 15.3, highlighting the improved eCE achieved through this innovative design.