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<p>This study demonstrates that high-density pulsed electric current (HDPEC) treatment enhances the performance of NiTi shape memory alloy (SMA) wires through short, non-equilibrium electrical stimulation enabling both annealing and recovery. At the optimal HDPEC annealing condition of a single pulse at 310 A for 10 ms, HDPEC-driven recovery achieved complete shape recovery, whereas conventional heat treatment (CHT)-annealed wires reached only 52.9% recovery. Even under severe bending deformation, HDPEC-treated wires kept recovery ratios above 80%. Moreover, 90.7% recovery was achieved at a low recovery current of 90 A while the bulk temperature remained below the austenite finish temperature (<i>A</i><sub><i>f</i></sub>), indicating that HDPEC can activate recovery under reduced thermal loads via combined thermal and athermal contributions. X-ray diffraction analysis revealed a marked increase in the B2 austenite phase fraction together with grain refinement to approximately 15–20 nm. In contrast to CHT annealing and recovery routes, HDPEC preserves a nanocrystalline microstructure while enabling effective phase reversion. Overall, HDPEC provides a localized and energy-efficient pathway for improving recoverability and microstructural stability of SMA wires, offering strong potential for low-power shape memory alloy-based actuators and flexible robotic systems.</p>

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Improving the Recovery Capability and Phase Composition of NiTi Shape Memory Alloy Wires by High-Density Pulsed Electric Current Treatment

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月2日

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  • Bochen Li,
  • Shaojie Gu,
  • Yasuhiro Kimura,
  • Yang Ju,
  • Yuhki Toku

摘要

This study demonstrates that high-density pulsed electric current (HDPEC) treatment enhances the performance of NiTi shape memory alloy (SMA) wires through short, non-equilibrium electrical stimulation enabling both annealing and recovery. At the optimal HDPEC annealing condition of a single pulse at 310 A for 10 ms, HDPEC-driven recovery achieved complete shape recovery, whereas conventional heat treatment (CHT)-annealed wires reached only 52.9% recovery. Even under severe bending deformation, HDPEC-treated wires kept recovery ratios above 80%. Moreover, 90.7% recovery was achieved at a low recovery current of 90 A while the bulk temperature remained below the austenite finish temperature (Af), indicating that HDPEC can activate recovery under reduced thermal loads via combined thermal and athermal contributions. X-ray diffraction analysis revealed a marked increase in the B2 austenite phase fraction together with grain refinement to approximately 15–20 nm. In contrast to CHT annealing and recovery routes, HDPEC preserves a nanocrystalline microstructure while enabling effective phase reversion. Overall, HDPEC provides a localized and energy-efficient pathway for improving recoverability and microstructural stability of SMA wires, offering strong potential for low-power shape memory alloy-based actuators and flexible robotic systems.