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<p>This study systematically investigates the solute-vacancy coupling diffusion mechanisms in aluminum alloys using atomic kinetic Monte Carlo simulations for 50 solute elements. The calculated self-diffusion coefficient of Al and solute diffusion coefficients agree well with density functional theory with harmonic transition state theory predictions and experimental data, validating the simulation reliability. Contrary to conventional understanding, transition metals (excluding IB/IIB groups) exhibit non-vacancy-mediated diffusion due to repulsive solute-vacancy interactions and high exchange barriers. Analysis of solute-vacancy drag ratios reveals that Mg consistently shows negative drag ratios (indicating inverse Kirkendall behavior), while other solutes transition from positive (vacancy drag) to negative (inverse Kirkendall) ratios with increasing temperature, following a Boltzmann function. The drag transition temperature correlates linearly with solute-vacancy binding energy (except for Cu). Lifetime analysis of solute-vacancy pairs identified optimal microalloying elements (such as Ge, In, Se, La) for aging control, demonstrating effective vacancy trapping during natural aging and millisecond-scale release during artificial aging. This work provides theoretical guidance for alloy design and heat treatment while elucidating the atomic-scale mechanisms of solute-vacancy dynamic coupling in aluminum alloys.</p>

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Atomic Kinetic Monte Carlo Simulations Reveal Solute-Vacancy Dynamics in Aluminum and Their Governing Role in Precipitation Aging

  • 期刊论文

  • 发表日期：

    2025年9月24日

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  • Shuiqing Jing,
  • Xiangshan Kong,
  • Cunsheng Zhang,
  • Guoqun Zhao,
  • Liang Chen

摘要

This study systematically investigates the solute-vacancy coupling diffusion mechanisms in aluminum alloys using atomic kinetic Monte Carlo simulations for 50 solute elements. The calculated self-diffusion coefficient of Al and solute diffusion coefficients agree well with density functional theory with harmonic transition state theory predictions and experimental data, validating the simulation reliability. Contrary to conventional understanding, transition metals (excluding IB/IIB groups) exhibit non-vacancy-mediated diffusion due to repulsive solute-vacancy interactions and high exchange barriers. Analysis of solute-vacancy drag ratios reveals that Mg consistently shows negative drag ratios (indicating inverse Kirkendall behavior), while other solutes transition from positive (vacancy drag) to negative (inverse Kirkendall) ratios with increasing temperature, following a Boltzmann function. The drag transition temperature correlates linearly with solute-vacancy binding energy (except for Cu). Lifetime analysis of solute-vacancy pairs identified optimal microalloying elements (such as Ge, In, Se, La) for aging control, demonstrating effective vacancy trapping during natural aging and millisecond-scale release during artificial aging. This work provides theoretical guidance for alloy design and heat treatment while elucidating the atomic-scale mechanisms of solute-vacancy dynamic coupling in aluminum alloys.