Professor Fuzeng REN and team, from the Department of Materials Science and Engineering at the Southern University of Science and Technology (SUSTech), have achieved new progress in the study of elastocaloric materials with a wide temperature range. The related findings were published in the academic journal Advanced Functional Materials under the title “Super-Stable Triphase Nanostructured NiTi for Elastocaloric Heat Pump.”

Against the backdrop of the global energy transition and the “carbon peak and neutrality goals” goals, traditional refrigeration and heat pump technologies based on vapor compression are posing increasingly severe greenhouse gas challenges to the environment and climate due to their reliance on refrigerants. In this context, solid-state cooling technology is gradually gaining attention in both research and industry. This technology utilizes physical properties in materials which undergo solid–solid phase transitions under magnetic, electric, or stress fields accompanied by heat absorption or release (such as the magnetocaloric effect, electrocaloric effect, and elastocaloric effect), enabling efficient cooling and heating. Among them, stress-driven elastocaloric cooling/heat pump technology does not require traditional refrigerants and offers significant advantages such as environmental friendliness, high energy efficiency, and ease of fabrication and recycling, making it a focal point of international research.

Among many materials suitable for elastocaloric applications, superelastic nickel-titanium shape memory alloys are considered one of the ideal candidates for solid-state elastocaloric heat pumps because they can release and absorb a large amount of latent heat during stress-induced reversible phase transformations. However, commercially available nickel-titanium alloys still face significant challenges in practical applications: their mechanical properties and elastocaloric effects are highly sensitive to temperature changes, and they are prone to functional degradation and fatigue failure under cyclic loading, making it difficult to meet the engineering requirements of heat pump systems for stable operation over a period of more than ten years.

(Figure 1) Wide Temperature Range Elastocaloric Effect

To address these key bottlenecks, the research team successfully prepared a three-phase nanostructured nickel-titanium alloy consisting of nanocrystalline martensite, nanocrystalline austenite, and an amorphous phase by precisely controlling the cold-rolling process parameters. Within a wide temperature range of 20-100 °C, the alloy’s stress-strain response and adiabatic temperature change show little variation with environmental temperature (Figure 1), demonstrating excellent mechanical stability, thermal stability, and shape-memory effect stability.

In addition to stable performance over a wide temperature range, this material also demonstrates outstanding long-term service reliability: across 200 million cyclic loading conditions, it showed almost no functional degradation or fatigue failure (Figure 2), confirming its ultra-long lifespan and high reliability even under extreme conditions. Researchers noted that this achievement provides a new approach for the design and regulation of a new generation of ultra-stable shape memory alloys, and it is expected to promote the engineering and large-scale application of elastocaloric refrigeration and solid-state heat pump technologies.

(Figure 2) Functional Fatigue Performance

Dr. Kangjie CHU, Research Assistant Professor of the Department of Materials Science and Engineering at SUSTech, is the first author of the paper, and Professor Fuzeng REN from the same department is the corresponding author. SUSTech is the primary affiliation for the paper.

Paper Link：https://doi.org/10.1002/adfm.202526980