Giant enhancement of elastocaloric effect by introducing microstructural holes

Abstract

Improving the elastocaloric effect (eCE) under a low stress by microstructure design is critical for the realization of eCE based solid-state cooling technology. Herein, we demonstrate a nearly seven-fold enhancement of adiabatic temperature change (ΔTad) and a large operating temperature window (WT), by simply introducing microstructural holes into a polycrystal shape memory alloy via phase-field simulations. At a low external compressive stress of 170 MPa, ΔTad is increased from 1 to 7.1 K and WT is 9 K when a microstructural hole with a radius of 200 nm is introduced. It is found that under such a low external compressive stress, the local stress concentration induced by the hole initiates and promotes the austenite-martensite transformation that otherwise cannot occur in the sample without a microstructural hole, and thus is responsible for the giant enhancement of ΔTad. These findings would provide guidance to improve low-stress eCE by microstructural geometry design.