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<p>This study investigates the microstructural evolution of cold-worked AZ61 magnesium alloy under non-isothermal conditions to optimize thermomechanical processing for lightweight and energy-related applications. Solution-treated specimens were subjected to 15 and 30% cold deformation and were characterized by dilatometry, differential scanning calorimetry (DSC), x-ray diffraction (XRD), optical microscopy, and nanoindentation. The as-quenched alloy exhibited <i>γ</i> phase (Mg<sub>17</sub>Al<sub>12</sub>) precipitation between 200 and 320&#xa0;°C, followed by dissolution above 330&#xa0;°C. Cold deformation introduced high dislocation density and lattice strain, significantly modifying the thermal response. Dimensional changes resulted from the combined effects of <i>γ</i> phase precipitation/dissolution, recovery, and recrystallization. Continuous <i>γ</i> phase precipitation initiated at low temperatures along dislocations, causing slight contraction, while discontinuous precipitation occurred at higher temperatures, forming Mg-rich and Mg-poor solid solutions. Recovery taking place between 180 and 400&#xa0;°C induced alternating expansion and contraction due to strain annihilation, whereas recrystallization and <i>γ</i> phase dissolution dominate above 400&#xa0;°C, resulting in a small net expansion. Hardness evolution confirmed these transformations, showing initial strengthening followed by softening. Overall, the results demonstrate a strong coupling between deformation history and non-isothermal microstructural evolution. The identified transformation ranges provide a basis for optimizing heat-treatment parameters, improving mechanical strength, thermal stability, and corrosion resistance, and enhancing the alloy’s potential in lightweight structural and Mg-based energy storage systems.</p>

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Microstructural Transformations in Cold-Worked AZ61 Mg Alloy During Non-Isothermal Heating

  • 期刊论文

  • 发表日期：

    2026年2月13日

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  • Abdelali Hayoune,
  • Jamal Fajoui,
  • Ahmed Noumi,
  • Yasser Mahfoud Ghimouze

摘要

This study investigates the microstructural evolution of cold-worked AZ61 magnesium alloy under non-isothermal conditions to optimize thermomechanical processing for lightweight and energy-related applications. Solution-treated specimens were subjected to 15 and 30% cold deformation and were characterized by dilatometry, differential scanning calorimetry (DSC), x-ray diffraction (XRD), optical microscopy, and nanoindentation. The as-quenched alloy exhibited γ phase (Mg17Al12) precipitation between 200 and 320 °C, followed by dissolution above 330 °C. Cold deformation introduced high dislocation density and lattice strain, significantly modifying the thermal response. Dimensional changes resulted from the combined effects of γ phase precipitation/dissolution, recovery, and recrystallization. Continuous γ phase precipitation initiated at low temperatures along dislocations, causing slight contraction, while discontinuous precipitation occurred at higher temperatures, forming Mg-rich and Mg-poor solid solutions. Recovery taking place between 180 and 400 °C induced alternating expansion and contraction due to strain annihilation, whereas recrystallization and γ phase dissolution dominate above 400 °C, resulting in a small net expansion. Hardness evolution confirmed these transformations, showing initial strengthening followed by softening. Overall, the results demonstrate a strong coupling between deformation history and non-isothermal microstructural evolution. The identified transformation ranges provide a basis for optimizing heat-treatment parameters, improving mechanical strength, thermal stability, and corrosion resistance, and enhancing the alloy’s potential in lightweight structural and Mg-based energy storage systems.