Dislocation transmission across grain boundary (GB) and activation of dislocation source in adjacent grains are considered common features of dislocation-GB interactions in regulating the mechanical properties and behaviors of metallic materials and structures. However, it is currently unclear which of dislocation transmission and dislocation source activation plays the dominant role in regulating dislocation-GB interaction. To study the competition between dislocation transmission and dislocation source activation, a theoretical framework is established based on a dislocation pile-up model. It is found that both dislocation transmission and dislocation source activation exhibit strong dependence on the GB misorientation angle. The critical transmission stress derived based on an energy method also depends on the grain size in a scaling form similar to the Hall-Petch relation. The outgoing slip systems during dislocation transmission are successfully predicted and agree with experimental observations. Regarding the dislocation source activation, the critical activation stress is investigated by examining the local stress fields generated by single and multiple slip dislocation pile-ups. It is found that compared with single slip dislocation pile-up, the result of multiple slip dislocation pile-ups displays lower critical activation stresses and exhibits feature of sensitivity to loading direction, interpreting the reported results of dislocation source activation in polycrystals. Further comparison between dislocation transmission and dislocation source activation for ⟨100⟩ tilt GBs indicates that the dislocation transmission prevails at low angle GB, while dislocation source activation is prone to occur at high angle GB. Our theoretical studies quantify the dislocation-GB interaction induced by dislocation pile-ups, shed light on the competition between dislocation transmission and dislocation source activation, and might provide essential guidance for high-performance metallic material design.

跨晶界（GB）的位错传递和相邻晶粒中位错源的激活被认为是位错-GB相互作用在调节金属材料和结构的力学性能和行为中的共同特征。但是，目前尚不清楚位错的传递和位错源的激活在调节位错-GB相互作用中起主要作用。为了研究位错传递与位错源激活之间的竞争，基于位错堆积模型建立了理论框架。发现位错传输和位错源激活均表现出对GB取向角的强烈依赖性。基于能量方法得出的临界传输应力也取决于晶粒尺寸，该尺寸类似于霍尔-皮奇关系的缩放形式。错位传输过程中的传出滑移系统已成功预测并与实验观察结果一致。关于位错源的活化作用，通过研究由单次和多次滑脱位错堆积产生的局部应力场来研究临界活化应力。发现与单滑脱位堆积相比，多滑脱位堆积的结果显示出较低的临界活化应力，并且表现出对加载方向敏感的特征，这解释了多晶中位错源活化的报道结果。对于transmission100°倾斜GBs，位错传输和位错源激活之间的进一步比较表明，位错传输在低角度GB时占优势，而位错源激活在高角度GB时容易发生。我们的理论研究量化了位错堆积引起的位错-GB相互作用，阐明了位错传递与位错源活化之间的竞争，并可能为高性能金属材料设计提供重要指导。