发表机构
Tsinghua University; Beijing University of Technology（清华大学; 北京工业大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过统一晶体塑性-断裂框架，揭示了应力依赖的晶间与穿晶蠕变开裂机制转变，并量化了微观断裂机制与宏观蠕变断裂行为（如延性和寿命）的联系。
AI 中文摘要
金属在高温下的蠕变由于变形和失效机制在多尺度上的复杂相互作用而仍然具有挑战性。晶间开裂与穿晶开裂之间的权衡主导着金属材料蠕变断裂行为的转变。然而，这种转变的微观力学基础及其与蠕变断裂行为中宏观脆性到韧性转变的联系仍未解决。在此，通过一个统一的晶体塑性断裂框架，揭示了应力依赖的晶界空穴化与滑移诱导的晶内开裂之间的竞争。该框架在显式多晶微结构中整合了晶体塑性、晶界空穴化和晶体学裂纹扩展。微观尺度计算揭示了从高应力水平下的穿晶主导开裂，到中等应力下的晶间与穿晶混合开裂，再到低应力下的晶间主导开裂的转变，并伴随着不同的损伤局部化模式和裂纹路径从晶界扩展到晶粒内部的演变。结果进一步量化了微观断裂机制与宏观蠕变断裂行为之间的联系，包括断裂延性和蠕变寿命的变化。在高应力条件下，变形驱动的穿晶损伤局部化通过广泛的应变积累促进韧性断裂，而在低应力条件下，时间依赖的晶界损伤积累通过局部晶间断裂导致准脆性断裂。
英文摘要
High-temperature creep in metals remains challenging due to the complex interplay of deformation and failure mechanisms across multiple length scales. The trade-off between inter- and trans-granular cracking governs the transition of creep rupture behaviour in metallic materials. However, the micromechanical basis of the transition and its linkage to the macroscopic brittle to ductile transition in creep rupture behaviour remain unresolved. Here, the stress-dependent competition between grain-boundary cavitation and slip-induced intragranular cracking is revealed via a unified crystal plasticity fracture framework. The framework incorporates crystal plasticity, grain-boundary cavitation, and crystallographic crack propagation within an explicit polycrystalline microstructure. The microscale computation reveals the transition from trans-granular-dominated cracking at high stress levels to mixed inter- and trans-granular cracking at intermediate stresses and inter-granular-dominated cracking at lower stresses, accompanied by distinct damage localization modes and the evolution of crack paths from grain boundary to grain-interior propagation. The results further quantify the linkage between microscopic fracture mechanisms and macroscopic creep rupture behaviour, including changes in rupture ductility and creep life. Under high-stress conditions, deformation-driven trans-granular damage localization promotes ductile rupture through extensive strain accumulation, whereas under lower-stress conditions, time-dependent grain-boundary damage accumulation leads to quasi-brittle rupture through localized inter-granular fracture.
