Fatigue-resistant high-performance elastocaloric materials via additive manufacturing

TL;DR

This paper demonstrates that additive manufacturing of Titanium-Nickel alloys with intermetallic phases produces high-performance, low-hysteresis elastocaloric materials with enhanced efficiency and stability over one million cycles, suitable for cooling applications.

Contribution

It introduces a novel additive manufacturing approach to create low-hysteresis, high-efficiency elastocaloric materials with stable performance, leveraging intermetallic phases in Ti-Ni alloys.

Findings

Microstructure with intermetallic phases reduces hysteresis.

Efficiency increased by a factor of five.

Stable elastocaloric performance over one million cycles.

Abstract

Elastocaloric cooling, which exploits the latent heat released and absorbed as stress-induced phase transformations are reversibly cycled in shape memory alloys, has recently emerged as a frontrunner in non-vapor-compression cooling technologies. The intrinsically high thermodynamic efficiency of elastocaloric materials is limited only by work hysteresis. Here, we report on creating high-performance low-hysteresis elastocaloric cooling materials via additive manufacturing of Titanium-Nickel (Ti-Ni) alloys. Contrary to established knowledge of the physical metallurgy of Ti-Ni alloys, intermetallic phases are found to be beneficial to elastocaloric performances when they are combined with the binary Ti-Ni compound in nanocomposite configurations. The resulting microstructure gives rise to quasi-linear stress-strain behaviors with extremely small hysteresis, leading to enhancement in the materials efficiency by a factor of five. Furthermore, despite being composed of more than 50% intermetallic phases, the reversible, repeatable elastocaloric performance of this material is shown to be stable over one million cycles. This result opens the door for direct implementation of additive manufacturing to elastocaloric cooling systems where versatile design strategy enables both topology optimization of heat exchangers as well as unique microstructural control of metallic refrigerants.