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<p>This study examines the impact of laser powder bed fusion (LPBF) scan strategies on the superelastic (SE) behavior of NiTi shape memory alloys (SMAs), with a particular focus on the distribution of residual stress, phase transformation characteristics, and microstructural evolution. Five unique scan strategies, including spatially varied island and hexagonal patterns and rotation angles (45°, 67°, 90°), were implemented to produce specimens with a consistent energy input. The mechanical response was assessed using compression experiments in conjunction with digital image correlation, while the crystallographic texture and phase transformation temperatures were characterized using electron backscatter diffraction (EBSD) and differential scanning calorimetry (DSC). The results indicated that the 90° rotation strategy resulted in a robust &lt; 001 &gt; fiber texture, which in turn resulted in a superior SE recovery (~ 6%) and minimal plastic strain. In contrast, the hexagonal and island strategies, despite reducing transformation onset stress, exhibited incomplete recovery and retained martensite as a result of elevated austenite end temperatures (~ 32–34&#xa0;°C). These strategies were found to promote equiaxed grains with a weakened texture, as evidenced by the EBSD analysis and the lower residual stress levels that were confirmed through indentation-based estimation. This work emphasizes the importance of scan path design as a critical process parameter, as it allows for the customization of functional behavior in NiTi alloys without affecting the alloy chemistry or energy input. Consequently, it provides new opportunities for the application-specific optimization of shape memory materials.</p>

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Exploring the Impact of Scan Strategies on the Superelastic Behavior of NiTi Alloys Fabricated by Laser Powder Bed Fusion

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年9月8日

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  • Nasrin Taheri Andani,
  • Shiva Mohajerani,
  • Alireza Behvar,
  • Keyvan Safaei,
  • Ahu Celebi,
  • Mohammad Elahinia

摘要

This study examines the impact of laser powder bed fusion (LPBF) scan strategies on the superelastic (SE) behavior of NiTi shape memory alloys (SMAs), with a particular focus on the distribution of residual stress, phase transformation characteristics, and microstructural evolution. Five unique scan strategies, including spatially varied island and hexagonal patterns and rotation angles (45°, 67°, 90°), were implemented to produce specimens with a consistent energy input. The mechanical response was assessed using compression experiments in conjunction with digital image correlation, while the crystallographic texture and phase transformation temperatures were characterized using electron backscatter diffraction (EBSD) and differential scanning calorimetry (DSC). The results indicated that the 90° rotation strategy resulted in a robust < 001 > fiber texture, which in turn resulted in a superior SE recovery (~ 6%) and minimal plastic strain. In contrast, the hexagonal and island strategies, despite reducing transformation onset stress, exhibited incomplete recovery and retained martensite as a result of elevated austenite end temperatures (~ 32–34 °C). These strategies were found to promote equiaxed grains with a weakened texture, as evidenced by the EBSD analysis and the lower residual stress levels that were confirmed through indentation-based estimation. This work emphasizes the importance of scan path design as a critical process parameter, as it allows for the customization of functional behavior in NiTi alloys without affecting the alloy chemistry or energy input. Consequently, it provides new opportunities for the application-specific optimization of shape memory materials.