In this work, we proposed a process to improve the functional stability of Ni-rich NiTi alloys, which combines surface nano-crystallization by means of ultrasonic shot peening and subsequent low-temperature (523 K) aging treatment. The as-annealed coarse-grained NiTi plates were fist subjected to ultrasonic shot peening, which generates nano-grains at the surface region, and introduces dislocation networks in the interior of the NiTi sample. Both the grain boundaries and the dislocations could serve as the heterogenous nucleation sites for Ni₄Ti₃ nanoprecipitates during subsequent low-temperature aging treatment. Therefore, with the presence of nano-grains and dislocation networks, a homogeneous distribution of Ni₄Ti₃ nanoprecipitates in the sample is expected, which will strengthen largely the NiTi matrix and resist the plastic activities during the repetitive martensitic transformation. As a result, the improved stability during cyclic superelastic loading is achieved.

在这项工作中，我们提出了一种提高富镍NiTi合金功能稳定性的方法，该方法结合了通过超声喷丸处理和随后的低温（523 K）时效处理而形成的表面纳米晶。首先对退火后的粗晶粒NiTi板进行超声喷丸处理，这会在表面区域产生纳米晶粒，并在NiTi样品内部引入位错网络。在随后的低温时效处理过程中，晶界和位错均可作为Ni ₄ Ti ₃纳米沉淀的异质成核位点。因此，在存在纳米晶粒和位错网络的情况下，Ni ₄ Ti ₃的均匀分布预计样品中会出现纳米沉淀，这将在很大程度上强化NiTi基体，并在重复性马氏体转变过程中抵抗塑性活动。结果，在循环超弹性载荷期间实现了改善的稳定性。