Additive grain boundary (GB) engineering holds significant potential for developing materials and structures with excellent mechanical properties by precisely controlling GB structure. The GBs that can be eliminated by plastic behavior activities prior to crack cleavage are ideal special ones for resisting intergranular fracture. Through molecular dynamics simulation, this work constructs special boundaries and studies the intrinsic characteristics of GB elimination. The results show that GB elimination phenomenon significantly depends on crack growth direction and GB plane. The classical theory developed by Rice fails to identify the mechanisms of two dependent characteristics. According to shear forces on atoms at crack tip, this work finds that the dependence of GB elimination on crack growth direction is attributed to the change of atomic slip characteristics. GB elimination occurs in specific growth directions where atomic slip is driven by the system of $\left(1\overline{1}2\right)\left[\overline{1}11\right]$. By considering T stress effect, GB elimination and its dependence on GB plane are well explained. The dependence of GB elimination on GB plane is attributed to the complex changes in critical stress intensity factors for twinning formation, perfect dislocation nucleation, and cleavage. GB elimination occurs on specific GBs where T stress makes the critical stress intensity factors for twinning and dislocation nucleation significantly lower than that for cleavage. The identified intrinsic characteristics of GB elimination provide references for GB design.

中文翻译：

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bcc 铁晶间微裂纹前塑性变形诱导晶界消除的本质特性


通过精确控制 GB 结构，增材晶界 （GB） 工程在开发具有优异机械性能的材料和结构方面具有巨大潜力。在裂纹解理之前可以通过塑性行为活动消除的 GB 是抵抗晶间断裂的理想特殊 GB s。通过分子动力学模拟，本工作构建了特殊边界，研究了 GB 消除的内在特性。结果表明：GB 消除现象显著依赖于裂纹扩展方向和 GB 平面;赖斯提出的经典理论未能确定两个依赖特征的机制。根据裂纹尖端原子的剪切力，本工作发现 GB 消除对裂纹扩展方向的依赖性归因于原子滑移特性的变化。GB 消除发生在特定的生长方向上，其中原子滑移由 $\left(1\overline{1}2\right)\left[\overline{1}11\right]$ 系统驱动。通过考虑 T 应力效应，很好地解释了 GB 消除及其对 GB 平面的依赖性。GB 消除对 GB 平面的依赖性归因于孪晶形成、完美位错成核和裂解的临界应力强度因子的复杂变化。GB 消除发生在特定的 GB 上，其中 T 应力使孪晶和位错成核的临界应力强度因子显著低于裂解。已确定的 GB 消除的内在特征为 GB 设计提供了参考。