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<p>Nickel–titanium (NiTi) shape memory alloys (SMAs) with a nominal composition of 50.8 at% Ni and 49.2 at% Ti were fabricated using the as-fabricated laser powder bed fusion (LPBF) technique. This study focuses on the impact of post-processing heat treatments—specifically solution annealing and aging at 500&#xa0;°C for 1 and 20&#xa0;h—on phase transformation behavior and functional performance. Phase analysis (XRD) was conducted at room temperature (~ 25&#xa0;°C), while uniaxial tensile testing was performed at both room (~ 25&#xa0;°C) and sub-zero (–20&#xa0;°C) temperatures. Differential scanning calorimetry (DSC) was carried out over a wide temperature range to evaluate the thermal behavior of the material. The results indicate that heat treatment conditions significantly affect transformation temperatures, phase constitution, and mechanical response. Depending on the treatment and test temperature, the microstructure varied from fully austenitic to fully martensitic or mixed-phase states. These variations manifested as distinct features in the stress–strain behavior, particularly in terms of martensitic transformation and superelasticity. The study demonstrates the feasibility of fine-tuning functional properties in LPBF-produced NiTi SMAs through optimized thermal processing strategies.</p> Graphical abstract <p></p>

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Tailoring phase transformation behavior and functional properties of LPBF-fabricated NiTi alloys via post-processing heat treatment

  • 期刊论文

  • 发表日期：

    2026年4月8日

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  • Jerzy Ratajski,
  • Błażej Bałasz,
  • Agnieszka Peła,
  • Paweł Krupski,
  • Kamil Bochenek,
  • Łukasz Major

摘要

Nickel–titanium (NiTi) shape memory alloys (SMAs) with a nominal composition of 50.8 at% Ni and 49.2 at% Ti were fabricated using the as-fabricated laser powder bed fusion (LPBF) technique. This study focuses on the impact of post-processing heat treatments—specifically solution annealing and aging at 500 °C for 1 and 20 h—on phase transformation behavior and functional performance. Phase analysis (XRD) was conducted at room temperature (~ 25 °C), while uniaxial tensile testing was performed at both room (~ 25 °C) and sub-zero (–20 °C) temperatures. Differential scanning calorimetry (DSC) was carried out over a wide temperature range to evaluate the thermal behavior of the material. The results indicate that heat treatment conditions significantly affect transformation temperatures, phase constitution, and mechanical response. Depending on the treatment and test temperature, the microstructure varied from fully austenitic to fully martensitic or mixed-phase states. These variations manifested as distinct features in the stress–strain behavior, particularly in terms of martensitic transformation and superelasticity. The study demonstrates the feasibility of fine-tuning functional properties in LPBF-produced NiTi SMAs through optimized thermal processing strategies.

Graphical abstract