失配位错层级控制非共格非CSL晶界滑动

中文摘要 AI 辅助

晶界（GB）变形显著影响多晶材料的力学响应，然而大多数原子尺度研究集中于重合位置点阵（CSL）晶界。受原位原子分辨率观察的启发，我们利用原子建模研究了面心立方（FCC）金属中无台阶的非对称非CSL倾转晶界的滑动。在这些非公度晶界中，致密排列的初级失配位错阵列容纳局部界面失配，而间距更宽的次级晶界失配位错阵列容纳残余失配。均匀滑动计算揭示了两个不同的量：最小晶界结构周期λ，由初级晶界失配位错的重复排列定义；以及滑移矢量b，由恢复等效晶界结构的最小位移-移位-完整平移决定。非均匀滑动通过次级晶界失配位错的滑移进行，这些位错携带b并将连续的晶界段在晶体学等效平移状态之间转换。这些次级失配位错分解为不全位错，每个不全位错携带一个不全伯格斯矢量b_p并连接中间界面状态。次级失配不全位错之间的特征间距定义了更长的周期Λ。在无热应力以下，每个不全位错通过两步热激活扭折对机制滑移，使不全位错前进一个结构周期l。这些结果建立了一个统一的晶体学和位错框架，用于理解结构复杂的非对称晶界中应力驱动的滑动。

英文摘要

Grain boundaries (GBs) strongly affect the mechanical response of polycrystalline materials, yet most atomistic studies have focused on coincidence site lattice (CSL) boundaries. Motivated by in situ atomic-resolution observations, we investigate step-free sliding along asymmetric non-CSL tilt GBs in face-centered cubic (FCC) metals using atomistic modeling. In these incommensurate GBs, a dense array of non-glissile primary misfit dislocations accommodates local interfacial mismatch, whereas a more widely spaced array of glissile secondary misfit dislocations accommodates residual mismatch. Uniform-sliding calculations reveal two distinct quantities: the minimum GB structural periodicity λ, defined by the repeating arrangement of primary GB misfit dislocations, and the slip vector b, corresponding to the minimum displacement-shift-complete translation that restores an equivalent GB structure. Nonuniform sliding proceeds through the glide of secondary GB misfit dislocations, which carry b and transform successive boundary segments between crystallographically equivalent translation states. The characteristic spacing between secondary misfit dislocations defines a longer periodicity Λ. For the representative {331}/{111} GB, each secondary misfit dislocation glides through a thermally activated two-step kink-pair mechanism below the athermal stress, advancing by one structural period λ. These results establish a unified crystallographic and dislocation-based framework for understanding stress-driven sliding in structurally complex asymmetric GBs.

发表机构

• Woodruff School of Mechanical Engineering, Georgia Institute of Technology（佐治亚理工学院机械工程学院）
• School of Mechanics and Engineering Science, Peking University（北京大学力学与工程科学学院）
• Institute of Microstructure and Property of Advanced Materials, Beijing Key Lab of Microstructure and Property of Advanced Materials, Beijing University of Technology（北京工业大学先进材料微结构及性能研究所）

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