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<p>The damping properties of additively manufactured NiTi alloys are strongly influenced by phase transformation behavior and pore defects, both of which are highly sensitive to process parameters. This study investigates the effects of energy density on the damping behavior of laser powder bed fusion (LPBF) fabricated NiTi alloys by analyzing the evolution of microstructure and phase transformation behavior. As energy density increases from 72.7 to 240.0&#xa0;J/mm³, relative density decreases from 99.55 to 98.67% due to the transformation of small spherical gas pores (~ 35&#xa0;μm) into larger irregular keyhole pores (&gt; 100&#xa0;μm), which increases the overall pore volume. Meanwhile, the martensitic transformation finish temperature (<i>M</i><sub>f</sub>) temperature increases from − 41&#xa0;°C to 40&#xa0;°C with energy density increases from 72.7 to 240.0&#xa0;J/mm³, resulting in an increase in martensite fraction until the sample transformed into a full martensite state at room temperature. Internal friction (IF) at room temperature initially increases from 0.034 to 0.057 as energy density increases to 171.4&#xa0;J/mm<sup>3</sup> and then decreases to 0.050 at 240.0&#xa0;J/mm<sup>3</sup>. This variation arises from the synergistic effects between pore defects and martensitic fraction. The highest internal friction (IF = 0.057, at a strain amplitude of 0.1% and frequency of 1&#xa0;Hz) is observed at 171.4&#xa0;J/mm<sup>3</sup>, corresponding to a high martensitic fraction and numerous fine pores. These findings provide insights into optimizing the damping performance of LPBF fabricated NiTi alloys.</p> Graphical Abstract <p></p>

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Effects of Phase Transformation Behavior and Pore Defects on the Damping Performance of NiTi Alloys Fabricated by Laser Power Bed Fusion

  • 期刊论文

  • 发表日期：

    2025年12月5日

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  • Qin Yang,
  • Mingzheng Huo,
  • Zheng Xiang,
  • Mingyan Sun,
  • Xianfeng Shen,
  • Shuke Huang,
  • Jie Chen

摘要

The damping properties of additively manufactured NiTi alloys are strongly influenced by phase transformation behavior and pore defects, both of which are highly sensitive to process parameters. This study investigates the effects of energy density on the damping behavior of laser powder bed fusion (LPBF) fabricated NiTi alloys by analyzing the evolution of microstructure and phase transformation behavior. As energy density increases from 72.7 to 240.0 J/mm³, relative density decreases from 99.55 to 98.67% due to the transformation of small spherical gas pores (~ 35 μm) into larger irregular keyhole pores (> 100 μm), which increases the overall pore volume. Meanwhile, the martensitic transformation finish temperature (Mf) temperature increases from − 41 °C to 40 °C with energy density increases from 72.7 to 240.0 J/mm³, resulting in an increase in martensite fraction until the sample transformed into a full martensite state at room temperature. Internal friction (IF) at room temperature initially increases from 0.034 to 0.057 as energy density increases to 171.4 J/mm3 and then decreases to 0.050 at 240.0 J/mm3. This variation arises from the synergistic effects between pore defects and martensitic fraction. The highest internal friction (IF = 0.057, at a strain amplitude of 0.1% and frequency of 1 Hz) is observed at 171.4 J/mm3, corresponding to a high martensitic fraction and numerous fine pores. These findings provide insights into optimizing the damping performance of LPBF fabricated NiTi alloys.

Graphical Abstract