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<p>This work investigates the impact of various tool pin profiles on the microstructural development and corrosion behavior of AZ61 magnesium alloy during friction stir welding (FSW). Four pin geometries—threaded, hexagonal, square, and triangular—were evaluated under identical welding parameters. Comprehensive characterization using optical microscopy, SEM, and XRD revealed that the tool geometry significantly influences grain refinement, precipitate distribution, and crystallographic features. Among all profiles, the square pin produced the most refined grain structure (3.32&#xa0;µm), the highest precipitate density, and the greatest dislocation content, which promoted extensive dynamic recrystallization and reduced texture intensity. Electrochemical assessments, including immersion tests, open-circuit potential (OCP), and potentiodynamic polarization (Tafel) measurements, confirmed that the square pin exhibited superior corrosion resistance, reflected by the lowest corrosion rate (0.0215&#xa0;mpy) and the most noble potential (-0.85&#xa0;mV). The hexagonal pin also demonstrated good performance, while the threaded and triangular designs yielded relatively coarse microstructures and reduced corrosion resistance. The enhanced corrosion behavior was primarily linked to fine-grained microstructures, uniform precipitate distribution, and the development of a stable passive film.</p>

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Correlation Between Pin-Induced Microstructure and Corrosion Behavior in Friction Stir Welded AZ61 Magnesium Alloy

  • 期刊论文

  • 发表日期：

    2025年12月23日

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  • Mamillapalli Padmanabham,
  • Jai Krishna Sanku,
  • P. Govinda Rao

摘要

This work investigates the impact of various tool pin profiles on the microstructural development and corrosion behavior of AZ61 magnesium alloy during friction stir welding (FSW). Four pin geometries—threaded, hexagonal, square, and triangular—were evaluated under identical welding parameters. Comprehensive characterization using optical microscopy, SEM, and XRD revealed that the tool geometry significantly influences grain refinement, precipitate distribution, and crystallographic features. Among all profiles, the square pin produced the most refined grain structure (3.32 µm), the highest precipitate density, and the greatest dislocation content, which promoted extensive dynamic recrystallization and reduced texture intensity. Electrochemical assessments, including immersion tests, open-circuit potential (OCP), and potentiodynamic polarization (Tafel) measurements, confirmed that the square pin exhibited superior corrosion resistance, reflected by the lowest corrosion rate (0.0215 mpy) and the most noble potential (-0.85 mV). The hexagonal pin also demonstrated good performance, while the threaded and triangular designs yielded relatively coarse microstructures and reduced corrosion resistance. The enhanced corrosion behavior was primarily linked to fine-grained microstructures, uniform precipitate distribution, and the development of a stable passive film.