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Traction-separation relationships for hydrogen induced grain boundary embrittlement in nickel via molecular dynamics simulations

机译:氢在镍中引起的晶界脆化的牵引分离关系的分子动力学模拟

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A statistical approach combined with molecular dynamics simulations is used to study the influence of hydrogen on intergranular decohesion. This methodology is applied to a Ni ∑3(112)[110] symmetric tilt grain boundary. Hydrogenated grain boundaries with different H concentrations are constructed using an energy minimization technique with initial H atom positions guided by Monte Carlo simulation results. Decohesion behavior is assessed through extraction of a traction-separation relationship during steady-state crack propagation in a statistically meaningful approach, building upon prior work employing atomistic cohesive zone volume elements (CZVEs). A sensitivity analysis is performed on the numerical approach used to extract the traction-separation relationships, clarifying the role of CZVE size, threshold parameters necessary to differentiate elastic and decohesion responses, and the numerical averaging technique. Results show that increasing H coverage at the Ni ∑3(112)[110] grain boundary asymmetrically influences the crack tip velocity during propagation, leads to a general decrease in the work of separation required for crack propagation, and provides a reduction in the peak stress in the extracted traction-separation relationship. The present framework offers a meaningful vehicle to pass atomistically derived interfacial behavior to higher length scale formulations for intergranular fracture.
机译:统计方法与分子动力学模拟相结合,用于研究氢对晶间脱粘的影响。该方法应用于Ni ∑3(112)[110]对称倾斜晶界。使用能量最小化技术构建具有不同H浓度的氢化晶界,并通过Monte Carlo模拟结果指导初始H原子位置。通过在统计上有意义的方法中提取稳态与裂纹扩展过程中的牵引力-分离关系来评估脱粘行为,该方法基于先前的工作,采用了原子内聚区体积元素(CZVE)。对用于提取牵引力-分离关系的数值方法进行了敏感性分析,阐明了CZVE尺寸的作用,区分弹性和内聚力响应所必需的阈值参数以及数值平均技术。结果表明,Ni ∑3(112)[110]晶界处的氢覆盖率的增加非对称地影响了裂纹扩展过程中的裂纹尖端速度,导致裂纹扩展所需的分离功普遍降低,并降低了峰值。提取的牵引分离关系中的应力。本框架提供了一种有意义的手段,可以将原子衍生的界面行为传递给用于晶间骨折的更高尺度的配方。

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