相场模拟晶体缺陷相互作用与塑性变形机理研究

Investigating the nonplanar movement of the crystal lattice dislocations with the associated changes of their core structures, especially the effects of a complex stressed state and the presence of solute diffusion, is of scientific interest and utmost important for engineering applications. We are to perform systematically molecular dynamic simulations to study the effect of solute distribution on generalized stacking fault energy in magnesium crystal, then to construct a three-dimensional crystal energy functional which could take into account the dislocation reaction occurred at the intersection line of two planes, and finally to propose a three-dimensional phase field model based on the Peierls -Nabarro concept. We are to focus on elucidating the role of stress and solute diffusion on the mechanisms of dislocation ensemble movement by using the improved phase field model. The problems we are interested in include but not limit to cross slip, dislocation junctions and dislocation-interface reaction. We expect that the obtained results are helpful to deepen the understanding of the cross-scale interactions among crystal defects and the related strengthening and toughening mechanisms.

研究复杂应力状态和溶质原子影响下，典型晶体位错的核结构和非共面运动规律具有重要的学术意义和工程价值。我们拟利用分子动力学模拟系统研究溶质原子分布影响的层错能，进而构造能描述相交面交线处位错反应的三维晶体能函数，改进三维相场派纳模型。重点应用改进的相场派纳模型揭示复杂应力状态和溶质原子扩散对位错非共面运动包括位错交滑移、位错锁与位错界面反应的影响机制。所得结果有助于深入理解晶体缺陷之间的跨尺度相互作用及相关的强韧化变形机理。

研究复杂应力状态和溶质原子扩散影响下，典型晶体位错芯组态变化和运动规律具有重要的学术意义和工程价值。我们提出了一种改进的位错相交的相场模型，该方法可以更好地预测金属晶体的位错相互作用和塑性流动；我们建立了描述溶质原子扩散、位错和孔洞、沉淀相相互作用的相场模型，应用于辐照体系，揭示了辐照金属中氦泡在半共格界面处的分布规律和扩展位错穿越孔洞和夹杂相的规律；我们提出了一种集成DFT计算的相场晶体模型，应用于石墨烯-金属表面体系，该方法可以更好地同时描述界面的堆垛结构和位错网络。已发表标注论文21篇，培养了已毕业博士生 3 名，已毕业硕士生 3 名。所得结果有助于深入理解晶体缺陷之间的跨尺度相互作用及相关的强韧化变形机理。