In order to improve the functional stability of Ti-50.8 at.% Ni alloy, repeated stretch-bending deformation (SBD), electric pulse (EP), and age-hardening were combined. Phase transformation behavior and superelastic properties of NiTi alloy subjected to different treatments were compared and analyzed in terms of average grain size, dislocation morphology, and nanoscaled Ni₄Ti₃ precipitates. The results indicate that the average grain size was refined from the annealing state of 9.1 μm down to 5.4 μm, and that a certain amount of dislocations or dislocation networks were introduced via 7 SBD passes. As EP-processed, both local stress relaxation and the non-uniform temperature field facilitated the microstructure to be a more homogeneous and stable state. With the increase of pulse frequency from 150 Hz to 400 Hz, a two-stage martensitic transformation occurred to replace the one-stage phase transformation and the combined multi-process induced multi-stage martensitic transformation behavior. Nanoscaled Ni₄Ti₃ precipitates with sizes in the range of 20–40 nm were homogeneously distributed in the matrix of NiTi alloy after aging at 250 °C for 48 h. As a result, based on the coupling effect of “Annealing-SBD-150 Hz EP-aging”, excellent functional stability was obtained. The accumulative residual strain was reduced from the annealing state of 3.6%–1.1%.

为了提高Ti-50.8 at。％Ni合金的功能稳定性，将反复的拉伸弯曲变形（SBD），电脉冲（EP）和时效硬化相结合。根据平均晶粒尺寸，位错形态和纳米级Ni ₄ Ti ₃对经过不同处理的NiTi合金的相变行为和超弹性性能进行了比较和分析。沉淀。结果表明，平均晶粒尺寸从9.1μm的退火态降至5.4μm，并且通过7次SBD道次引入了一定数量的位错或位错网络。当进行EP处理时，局部应力松弛和温度场不均匀都促进了微结构更均匀和稳定的状态。随着脉冲频率从150 Hz增加到400 Hz，发生了两级马氏体相变，以代替一级相变和组合的多过程感应多级马氏体相变行为。纳米Ni ₄ Ti ₃在250°C时效48 h后，尺寸在20-40 nm范围内的析出物均匀分布在NiTi合金基体中。结果，基于“退火-SBD-150Hz EP-老化”的耦合效果，获得了优异的功能稳定性。累积残余应变从退火状态降低了3.6％–1.1％。