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Atomistic simulation of creep deformation mechanisms in nickel-based single crystal superalloys

机译：基于镍的单晶超合金蠕变变形机制的原子模拟

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In this paper, the creep deformation mechanisms are investigated in nickel-based single crystal superalloys. Two-dimensional molecular dynamics (MD) simulations are conducted to model various temperatures, stress conditions, and phase interface crystal orientations. Ni-based single-crystal superalloys are of great importance in the aircraft industry due to their excellent high temperature creep resistance. This characteristic mainly originates from two features considered in their structure; firstly, their two-phase micro-structure comprising gamma y and gamma prime γ', and secondly the nature of this superalloy itself, which is a single-crystal. MD is a powerful tool to gain insight into creep behavior at small scales, where dislocations and high-temperature diffusional phenomena are the most critical deformation agents. The parameters considered in the creep deformation are temperature, stress, and phase interface crystal orientation. The simulations are observed in various temperature conditions including 1100, 1200, 1400, 1600, and 1700 K. Stress levels are applied from 0.5 to 5.0 GPa with a sequence of 0.5 GPa, and phase interface crystal orientations are imposed on (001), (011) and (111). Various mechanisms are detected, including the γ' precipitate shearing, micro-twinning, the diffusion-mediated climb that allows the dislocations to bypass the γ' precipitates, and rafting that refers to directional γ' coarsening. The results are shown to be in good agreement with available experimental data. The steady-state creep phase is associated with a constant strain rate, which is calculated for each model. The power-law equation is employed to predict the steady-state strain rate as a function of stress, temperature, the required activation energy, and the stress exponent parameter. Finally, a deformation map is presented for different phase interface models based on the stress exponent parameter values.
机译：本文研究了基于镍的单晶超合金中的蠕变变形机制。进行二维分子动力学（MD）模拟以模拟各种温度，应力条件和相界面晶体取向。由于其优异的高温蠕变性，Ni基单晶高温合金在飞机行业中具有重要意义。这种特性主要来自其结构中考虑的两个特征;首先，它们的两相微结构包括γy和γ原子γ'，其次是该超合金本身的性质，其是单晶。 MD是一种强大的工具，可以在小尺度上深入了解蠕变行为，其中位错和高温扩散现象是最关键的变形剂。在蠕变变形中考虑的参数是温度，应力和相界晶体取向。在包括1100,1200,1400,1600和1700k的各种温度条件下观察到模拟。用0.5GPa的序列施加0.5至5.0GPa的应力水平，并施加相界晶体取向（001），（ 011）和（111）。检测各种机制，包括γ'沉淀剪切，微孪晶，允许脱位绕过γ'沉淀物的升降，并漂流，指向定向γ'粗化。结果显示与可用的实验数据吻合良好。稳态蠕变相与恒定应变速率相关联，该恒定应变速率是针对每个模型计算的。电力规律方程用于预测稳态应变速率作为应力，温度，所需的激活能量和应力指数参数的函数。最后，基于应力指数参数值呈现不同相位接口模型的变形图。

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