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<p>The present study investigates the metallurgical processing and corrosion behavior of NiTi shape-memory alloys fabricated via powder metallurgy. NiTi alloy pellets were compressed and sintered at 950°C for 1 h in an argon atmosphere, followed by aging at 550°C for 1, 2, and 3 h. Microstructural characterization (SEM, EDS, XRD) and electrochemical testing were performed to evaluate phase formation, porosity, and corrosion resistance, and the results revealed the presence of NiTi, Ti<sub>2</sub>Ni, and Ni<sub>3</sub>Ti phases, with progressive oxide (TiO<sub>2</sub>) formation during aging. Increasing aging time reduced porosity from 25.6% (sintered-only) to 24.2% (3-h-aged) and enhanced corrosion resistance, with the corrosion rate decreasing from 0.880 mpy to 0.162 mpy. Electrochemical impedance spectroscopy confirmed improved passivation behavior in the aged samples. Hardness measurements indicated precipitation hardening due to secondary phase formation. This study provides the first integrated evaluation of phase evolution, TiO<sub>2</sub> growth, porosity refinement, and electrochemical behavior in powder-metallurgy NiTi subjected to controlled aging. Unlike previous work focused mainly on cast NiTi, our results quantitatively link oxide formation and pore reduction to improved corrosion resistance in PM-processed alloys.</p>

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Corrosion Behavior and Phase Evolution of NiTi Alloys Fabricated by Powder Metallurgy and Aging Treatments

  • 期刊论文

  • 发表日期：

    2026年4月16日

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  • Suleiman Ibrahim Mohammad,
  • Asokan Vasudevan,
  • Ozodbek Nematov,
  • Rustam Turakulov,
  • A. Anderson

摘要

The present study investigates the metallurgical processing and corrosion behavior of NiTi shape-memory alloys fabricated via powder metallurgy. NiTi alloy pellets were compressed and sintered at 950°C for 1 h in an argon atmosphere, followed by aging at 550°C for 1, 2, and 3 h. Microstructural characterization (SEM, EDS, XRD) and electrochemical testing were performed to evaluate phase formation, porosity, and corrosion resistance, and the results revealed the presence of NiTi, Ti2Ni, and Ni3Ti phases, with progressive oxide (TiO2) formation during aging. Increasing aging time reduced porosity from 25.6% (sintered-only) to 24.2% (3-h-aged) and enhanced corrosion resistance, with the corrosion rate decreasing from 0.880 mpy to 0.162 mpy. Electrochemical impedance spectroscopy confirmed improved passivation behavior in the aged samples. Hardness measurements indicated precipitation hardening due to secondary phase formation. This study provides the first integrated evaluation of phase evolution, TiO2 growth, porosity refinement, and electrochemical behavior in powder-metallurgy NiTi subjected to controlled aging. Unlike previous work focused mainly on cast NiTi, our results quantitatively link oxide formation and pore reduction to improved corrosion resistance in PM-processed alloys.