The efficient storage and release of elastic mechanical energy are crucial in both natural and engineered mechanical systems, such as biological tissues for the fast locomotion as well as high-performance microelectromechanical actuators. Emerging applications, including artificial muscles, hopping robots, and unmanned aerial vehicle catapults, require elastic materials with enhanced energy density and efficiency. Metallic materials are the most well-known carriers of elastic energy due to their high strength and excellent workability, commonly utilized in forms such as springs and clockworks. However, the generally low energy storage density of current metallic materials hinders their application towards device minimization and integration.
To address this issue, researchers at the State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, proposed a "dual-level nanostructure" design strategy to achieve excellent elastic energy storage in shape memory alloys. As shown in Figure 1, this strategy constructs a nanocrystalline structure embedded with pre-stored martensite nanodomains. This leads to nucleation-free phase transformation and grain boundary strengthening effects, enabling the simultaneous achievement of high yield strength, large elastic strain, and low energy dissipation. The newly developed TiNiV shape memory alloys demonstrate ultrahigh elastic energy storage density (> 40 MJ/m³) with ultrahigh energy efficiency (> 94%) and excellent fatigue resistance. This concept, which combines nano-sized embryos to minimize energy dissipation of psuedo-elasticity and employs a fine-grained structure to enhance yield strength, could be applied to other ferroelastic materials. Furthermore, it holds promise for the development of phase transformation-involved functionalities such as high-performance dielectric energy storage, ultralow-hysteresis magnetostrain, and high-efficiency solid-state caloric cooling.
Figure 1: "Dual-level nanostructure" design strategy for ultrahigh elastic energy storage
The above research was published in the internationally renowned academic journal Advanced Materials under the title "Ultrahigh Elastic Energy Storage in Nanocrystalline Alloys with Martensite Nanodomains". The paper was completed under the guidance of Academician Sun Jun, Professor Ding Xiangdong, Professor Xue Dezhen, and Professor Zhou Yumei. Ph.D. student Dang Pengfei from the School of Materials Science and Engineering is the first author, with co-authors including Dr. Xu Yangyang, a young faculty member from the School of Physics at Xi'an Jiaotong University, and Ph.D. students Li Cheng and Yang Yuanchao (now graduated) from the School of Materials Science and Engineering. The State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, is the sole corresponding institution for the paper. This research was jointly funded by the National Key R&D Program, the National Natural Science Foundation of China, and the Xi'an Jiaotong University Youth Top Talent Program. The testing and characterization work involved in this study received support from the Xi'an Jiaotong University Analysis and Testing Center.
Paper Link: https://doi.org/10.1002/adma.202408275
