Materials Science & Engineering A 973 (2026) 150712

Keywords:NiTi shape memory alloy, Elastocaloric effect ,Fatigue life ,Microstructural reconstruction ,Synergistic strengthening mechanism

Elastocaloric cooling based on NiTi shape memory alloys offers a promising alternative to conventional vapor  compression refrigeration, yet the enhancement of elastocaloric and fatigue properties remains a critical chal lenge. In this work, a novel pretraining coupled low-temperature aging strategy is proposed to achieve syner gistic optimization of these properties. For the Ni 50.3 Ti 49.7  alloy, multiple pretraining schemes and aging  conditions are investigated and the strengthening mechanism is discussed. The optimal coupled treatment is  identified as cyclic pretraining to 10% strain for 5 cycles, followed by aging at 623 K for 120 min. Compared with  the as-received specimen, this processing route achieves 19.3% increase in the initial adiabatic temperature  change, 2.1-fold extension in fatigue life, and 50% reduction in the degradation rate of adiabatic temperature  change during cyclic loading. Multiscale characterization is employed to elucidate the underlying mechanisms.  The structure-property relationship is established by correlating the microstructural evolution induced by pre training and aging treatment with the macroscopic performance changes in elastocaloric effect and fatigue life.  The coupled treatment is found to reconstruct the microstructure through grain refinement with optimized  crystallographic orientation, the development of stable dislocation networks and dense martensite. These in sights demonstrate that by synergistically integrating multiple strengthening mechanisms through pretraining-  coupled aging treatment, the trade-off between elastocaloric performance and fatigue durability in single-  route processing can be effectively overcome, providing a feasible design strategy for high-performance NiTi-  based elastocaloric cooling systems.

Tianyi Hu, Xiaoxian Zhang, Yanju Liu, Jinsong Leng

Synergistic optimization of elastocaloric effect and fatigue life in NiTi shape memory alloys via pretraining-coupled aging treatment.pdf