Abstract

In view of the effect of hydrogen on the mechanical behavior of nanocrystal materials, a hydrogen embrittlement model is proposed based on the method of continuous distribution dislocation from the perspective of fracture mechanics. The effects of hydrogen on mechanical parameters such as surface energy, lattice friction, shear modulus, and atomic bonding force are analyzed to investigate the effects of crack tip (CT) dislocation emission on crack propagation rate, CT plastic zone and dislocation free zone size, as well as the initiation of nanocracks at grain boundaries (GBs) and within grains under hydrogen conditions. The results show that under the presence of hydrogen, it can reduce the resistance of dislocation movement, promote the emission of crack-tip dislocations, enlarge the plastic zone at the CT, and reduce the dislocation-free zone. In addition, hydrogen atoms can accumulate at GBs and inside grains to form hydrides, reducing the surface energy of the material and making it easier for nanocracks to nucleate at GBs and inside grains. Moreover, hydrogen can exacerbate the stress concentration at the CT, resulting in an accelerated crack propagation rate. This work provides a reasonable explanation for the microscopic mechanism of hydrogen induced fracture failure of metal materials.

中文翻译：

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氢气条件下纳米晶金属的特殊疲劳断裂行为

摘要

针对氢对纳米晶材料力学行为的影响，从断裂力学的角度提出了基于连续分布位错方法的氢脆模型。分析氢对表面能、晶格摩擦力、剪切模量和原子键合力等力学参数的影响，研究裂纹尖端（CT）位错发射对裂纹扩展速率、CT塑性区和无位错区尺寸的影响，以及在氢条件下在晶界 (GB) 和晶粒内引发纳米裂纹。结果表明，氢存在下，可以降低位错运动的阻力，促进裂尖位错的发射，扩大CT处的塑性区，减少无位错区。此外，氢原子可以在晶界和晶粒内部积聚形成氢化物，降低材料的表面能，使纳米裂纹更容易在晶界和晶粒内部成核。此外，氢会加剧CT处的应力集中，导致裂纹扩展速率加快。该工作为金属材料氢致断裂失效的微观机制提供了合理的解释。