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首页> 外文期刊>Journal of engineering materials and technology >High-Resolution Methods for Characterizing Mesoscale Dislocation Structures
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High-Resolution Methods for Characterizing Mesoscale Dislocation Structures

机译：表征中尺度位错结构的高分辨率方法

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It has become apparent through experimentation at the micro- and nanolevels that the crystalline defects known as dislocations have significant effects on a material's properties. Accordingly, a complete material state description must include the characterization of the dislocated state. However, this characterization presents a twofold problem: resolution and representation. In general, high-resolution microscopy techniques are only useful for considering a few dislocations at a time, but automated high-speed methods are only capable of resolving dislocation densities well above the average density in a typical annealed metal. The second challenge is developing a method of representation for the dislocated state. Unlike most state quantities, dislocation lengths are not conserved and complete representation would require tracking of position, momentum, and interactions, as well as the creation and annihilation of dislocations. Such a scheme becomes unwieldy when considering the large numbers of dislocations involved in common crystal plasticity. In 1970, Kroner ("Initial Studies of a Plasticity Theory Based Upon Statistical Mechanics," Inelastic Behaviors of Solids (Materials Sciences and Engineering), M. F. Kanninen et al, eds., McGraw-Hill, New York, pp. 137-147), a pioneer in the continuum representation of dislocations, proposed a statistical method using n-point correlations to classify the dislocated state in a compact form. In addition to providing a convenient form, the correlations naturally identify dipoles, multipoles, and other higher order structures, such as cells, networks, and braids. As formulated, Kroner's method would require high-resolution microscopy techniques, which limits its utility for experimental measurements. The current work presents a modification to Kroner's method that would allow it to be used within the currently available resolution limits of bulk microscopy. Furthermore, in this work, newly developed microscopy techniques are employed to refine those resolution limits to more significant levels. The high-resolution bulk dislocation characterization is applied to a well-annealed nickel specimen and the results including visualizations of mesoscale structures are presented.
机译：通过在微米和纳米水平上的实验，已经很明显地发现了称为位错的晶体缺陷会对材料的性能产生重大影响。因此，完整的材料状态描述必须包括位错状态的特征。但是，这种表征存在两个问题：分辨率和表示。通常，高分辨率显微镜技术仅可用于一次考虑几个位错，但是自动高速方法只能分辨位错密度，该位错密度远高于典型退火金属的平均密度。第二个挑战是开发一种表示脱位状态的方法。与大多数状态量不同，位错长度是不守恒的，并且完整的表示将需要跟踪位置，动量和相互作用以及位错的产生和and灭。当考虑到普通晶体可塑性中涉及的大量位错时，这种方案变得笨拙。 1970年，Kroner（“基于统计力学的可塑性理论的初步研究”，固体的非弹性行为（材料科学与工程），MF Kanninen等编辑，纽约麦格劳-希尔出版社，第137-147页）位错连续表示的先驱，提出了一种统计方法，该方法使用n点相关性以紧凑形式对位错状态进行分类。除了提供方便的形式外，相关还可以自然地识别偶极子，多极子和其他更高阶结构，例如单元，网络和辫子。按照规定，克罗纳方法需要高分辨率的显微镜技术，这限制了其在实验测量中的实用性。当前的工作提出了对Kroner方法的修改，该方法将允许在当前可用的大体积显微镜分辨率范围内使用它。此外，在这项工作中，采用了新开发的显微技术将分辨率极限提高到更重要的水平。将高分辨率的整体位错表征应用于退火良好的镍试样，并给出了包括中尺度结构可视化的结果。

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