Prakash Aruna, Bitzek Erik
Materials Science and Engineering, Institute I (MSE I), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Martensstrasse 5, Erlangen 91058, Germany.
Materials (Basel). 2017 Jan 23;10(1):88. doi: 10.3390/ma10010088.
Single-crystal Ni-base superalloys, consisting of a two-phase / γ ' microstructure, retain high strengths at elevated temperatures and are key materials for high temperature applications, like, e.g., turbine blades of aircraft engines. The lattice misfit between the and γ ' phases results in internal stresses, which significantly influence the deformation and creep behavior of the material. Large-scale atomistic simulations that are often used to enhance our understanding of the deformation mechanisms in such materials must accurately account for such misfit stresses. In this work, we compare the internal stresses in both idealized and experimentally-informed, i.e., more realistic, / γ ' microstructures. The idealized samples are generated by assuming, as is frequently done, a periodic arrangement of cube-shaped γ ' particles with planar / γ ' interfaces. The experimentally-informed samples are generated from two different sources to produce three different samples-the scanning electron microscopy micrograph-informed quasi-2D atomistic sample and atom probe tomography-informed stoichiometric and non-stoichiometric atomistic samples. Additionally, we compare the stress state of an idealized embedded cube microstructure with finite element simulations incorporating 3D periodic boundary conditions. Subsequently, we study the influence of the resulting stress state on the evolution of dislocation loops in the different samples. The results show that the stresses in the atomistic and finite element simulations are almost identical. Furthermore, quasi-2D boundary conditions lead to a significantly different stress state and, consequently, different evolution of the dislocation loop, when compared to samples with fully 3D boundary conditions.
单晶镍基高温合金由两相/γ'微观结构组成，在高温下仍保持高强度，是高温应用的关键材料，例如航空发动机的涡轮叶片。γ相与γ'相之间的晶格失配会导致内应力，这会显著影响材料的变形和蠕变行为。常用于增强我们对这类材料变形机制理解的大规模原子模拟必须准确考虑这种失配应力。在这项工作中，我们比较了理想化的以及基于实验信息的（即更现实的）/γ'微观结构中的内应力。理想化样本是通过像通常那样假设立方体形γ'颗粒具有平面/γ'界面的周期性排列生成的。基于实验信息的样本来自两个不同来源，以生成三个不同样本——扫描电子显微镜显微照片信息的准二维原子样本以及原子探针断层扫描信息的化学计量和非化学计量原子样本。此外，我们将理想化的嵌入式立方体微观结构的应力状态与纳入三维周期性边界条件的有限元模拟进行了比较。随后，我们研究了所得应力状态对不同样本中位错环演化的影响。结果表明，原子模拟和有限元模拟中的应力几乎相同。此外，与具有完全三维边界条件的样本相比，准二维边界条件导致显著不同的应力状态，从而导致位错环的不同演化。
