Temperature dependence of vacancy concentration and void growth mechanism in Al with constant hydrogen concentration: A first-principles study
Temperature dependence of vacancy concentration and void growth mechanism in Al with constant hydrogen concentration: A first-principles study
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DOI：
10.1016/j.engfracmech.2019.106508
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发表时间：
2019-07
影响因子：
5.4
通讯作者：
Pengyu Liu;R. Matsumoto
中科院分区：
文献类型：
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作者：
Pengyu Liu;R. Matsumoto
在本研究中，首次提出了在恒定溶质氢浓度和温度条件下，溶质氢的化学势和各种共存空位（包括原子空位和空位-氢配合物）的热平衡浓度的公式。通过密度泛函理论和晶格振动分析，对方程中随温度变化的物理性质进行评价，得到了溶质氢的化学势和Al中的空位浓度。我们发现氢从空位-氢配合物中溶解形成空位和间隙氢的临界温度约为200-300 K，这取决于溶质氢的浓度。最后，我们利用氢的化学势、空位浓度和原子空位扩散系数估算出的空隙中氢气压力，揭示了两种主要空隙生长机制的运行温度。第一个机制是塑性变形增长，这是由低温下孔隙内部的高压引起的。另一种是空位吸收生长机制，这是由于晶格中弥漫性空位在较高温度下被吸收所致。
In this study, a formulation that yields the chemical potential of solute hydrogen and thermal equilibrium concentrations of various coexisting vacancies, including atomic vacancy and vacancy–hydrogen complexes under the conditions of constant solute hydrogen concentration and temperature, is first proposed. The chemical potential of solute hydrogen and vacancy concentrations in Al are then obtained by evaluating the temperature-dependent physical properties in the equations via density functional theory and lattice vibration analyses. We found that hydrogen disbanded from vacancy–hydrogen complexes to form empty vacancy and interstitial hydrogen at the critical temperature approximately 200–300 K, depending on the solute hydrogen concentration. Finally, we revealed the operation temperatures of two principal void growth mechanisms by using the hydrogen pressure in the voids that are estimated from the chemical potential of hydrogen, vacancy concentrations, and diffusion coefficient of atomic vacancy. The first mechanism is plastic deformation growth, which is caused by high pressure inside the void at lower temperature. The other one is vacancy absorption growth mechanism, which is caused by absorbing diffusive vacancy in the lattice at higher temperature.