The brittle-ductile transition (BDT) of tungsten depends heavily on temperature-dependent dislocation mobility. To well understand the underlying mechanism of tungsten fracture behavior, the dislocation activities need to be well described, but the related model remains limited. In this work, a coupled crystal-plasticity and phase-field model (CP-PFM) is developed based on a unified thermodynamic framework, which considers the thermal activated kink-pair mechanism of screw dislocation motion, the evolution of dislocation density, and the coupling effects between the plasticity and the crack propagation. The developed model can well predict the experimental results and is used to study the BDT process of tungsten. Four typical fracture processes are disclosed depending on the temperature, including the brittle fracture, semi-brittle fracture, micro-ductile fracture and ductile fracture. They exhibit different micro-cleavage crack features, induced by the competition between the shielding effect of the plastic zone and the crack propagation near the crack tip zone. In addition, the fracture process of tungsten is found to be significantly influenced by non-Schmid effect in the low and medium temperature regimes.

钨的脆韧转变 (BDT) 在很大程度上取决于温度相关的位错迁移率。为了更好地理解钨断裂行为的潜在机制，需要很好地描述位错活动，但相关模型仍然有限。在这项工作中，基于统一的热力学框架，建立了耦合晶体塑性和相场模型（CP-PFM），该模型考虑了螺旋位错运动的热激活扭结对机制，位错密度的演变以及塑性与裂纹扩展之间的耦合效应。所建立的模型可以很好地预测实验结果，并用于研究钨的 BDT 过程。根据温度，公开了四种典型的断裂过程，包括脆性断裂、半脆性断裂、微观韧性断裂和韧性断裂。它们表现出不同的微解理裂纹特征，这是由塑性区的屏蔽作用与裂纹尖端区附近的裂纹扩展之间的竞争引起的。此外，发现钨的断裂过程在低温和中温条件下受到非施密德效应的显着影响。