Enhancing the Effect of Elastocaloric Cooling of NiTiCuCo Shape Memory Alloys by Cold-Rolling Process

Abstract

The elastocaloric cooling performance of NiTiCuCo nano-grain bulk and thin sheets are investigated via cold rolling and post-heat treatment process. At first, to enhance the elastocaloric cooling ability at room temperatures, a grain size of 59 nm NiTiCuCo pillar is fabricated by cold rolling and annealing. It shows a large and stable adiabatic temperature drop (ΔT) of 18 K over 104 cycles under 600 MPa, with an accumulated residual strain of 1%. The dense dislocation induced by cold rolling is effective in suppressing the growth of new dislocation and residual B19’. The COP reaches the highest value of 40, which surpasses commercial NiTi and previous result reported cold-rolled NiTi. Second, for the extension of NiTiCuCo to commercialization needs, the replacement of a SMA pillar by multiple stacked flakes is implemented, by using NiTiCuCo thin sheets. This thin sheet is fabricated through cold-rolling and aging, with a final thickness t of 0.4 mm. With an operating stress of 550 MPa, this thin sheet exhibits a consistent ΔT about 15 K and total residual strain εr of 1% over 105 cycles. The COP of this thin sheet doubles the commercial NiTi, providing a simpler and cost-effective processing routine for manufacturing eCC materials.

Date of Award	2025
Original language	English
Supervisor	Qingping SUN (Supervisor)