非线性界面动力学对粗化现象的影响
Effect of non-linear interface kinetics on coarsening phenomena
摘要：
粗化动力学通常使用下面的界面迁移（IM）速率的线性梯度近似来描述，其中界面处的迁移通量随驱动力线性变化。最近的实验研究表明，与传统的抛物线粗化动力学相比，纳米晶界面微结构的粗化出乎意料地稳定。在这里，我们表明，在早期粗化的这些微结构，IM率可以开发一个非线性的驱动力，平均界面曲率的依赖。我们推导了粗化动力学的修正平均场定律。单个晶界的分子动力学模拟揭示了IM速率的次线性曲率依赖性，表明在多晶金属中观察到的缓慢粗化动力学的内在起源。
英文摘要：
Coarsening kinetics is usually described using a linear gradient approximation for the underlying interface migration (IM) rates, wherein the migration fluxes at the interfaces vary linearly with the driving force. Recent experimental studies have shown that coarsening of nanocrystalline interface microstructures is unexpectedly stable compared to conventional parabolic coarsening kinetics. Here, we show that during early stage coarsening of these microstructures, IM rates can develop a non-linear dependence on the driving force, the mean interface curvature. We derive the modified mean field law for coarsening kinetics. Molecular dynamics simulations of individual grain boundaries reveal a sub-linear curvature dependence of IM rates, suggesting an intrinsic origin for the slow coarsening kinetics observed in polycrystalline metals.
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