Fractal analysis of the role of the rough interface between Bi2Sr2CaCu2Ox filaments and the Ag matrix in the mechanical behavior of composite round wires
Fractal analysis of the role of the rough interface between Bi2Sr2CaCu2Ox filaments and the Ag matrix in the mechanical behavior of composite round wires
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DOI：
10.1088/0953-2048/26/5/055016
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发表时间：
2013-04
影响因子：
3.6
通讯作者：
X. Gou;J. Schwartz
中科院分区：
文献类型：
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作者：
X. Gou;J. Schwartz
Bi_2Sr_2CaCu_2 O_x（Bi_2212）超导体在Ag/AgMg基体中的多芯圆线具有复杂的微观结构，对它们的电学和力学行为有很大的影响。Bi 2212/Ag界面，其特征在于在某些位置中Bi 2212生长到Ag基质中，导致粗糙的锯齿状界面，并且在其他位置中其特征在于Bi 2212生长桥接并连接到相邻Bi 2212细丝，被认为是最重要的微观结构特征之一;然而它们的作用还没有很好地理解。在这项工作中，一个基于分形的框架创建在努力理解的作用，在确定Bi 2212 RW的宏观机电行为的个别丝和Bi 2212/Ag界面的结构。从Bi 2212 RW中提取的单个Bi 2212细丝的扫描电子显微照片用于分析粗糙的Bi 2212/Ag界面，并使用Weierstrass-Mandelbrot（W-M）分形函数开发分形模型。然后使用W-M分形函数生成模拟的Bi 2212/Ag微结构。最后，研究了微结构的力学行为。据发现，在Bi 2212运输中发挥重要作用的中间桥不太可能是机电退化和故障的原因。相反，大的应力集中被确定在凹形尖端，发生沿着锯齿状的Bi 2212/Ag界面。特别是，凹头在Bi 2212细丝内的位置是Bi 2212 RW中可能的失效起始点。
Multifilamentary round wires (RWs) of Bi2Sr2CaCu2Ox (Bi2212) superconductor in a Ag/AgMg matrix have complex microstructures that strongly influence their electrical and mechanical behavior. The Bi2212/Ag interfaces, which in some locations are characterized by Bi2212 growths into the Ag matrix that result in rough, jagged interfaces, and in other locations are characterized by Bi2212 growths that bridge and connect to neighboring Bi2212 filaments, are believed to be amongst the most important microstructural features; yet their role is not well understood. In this work, a fractal-based framework is created in an effort to understand the role of the structure of individual filaments and the Bi2212/Ag interfaces in determining the macroscopic electromechanical behavior of Bi2212 RW. Scanning electron micrographs of an individual Bi2212 filament extracted from a Bi2212 RW are used to analyze the rough Bi2212/Ag interface and develop a fractal model using the Weierstrass–Mandelbrot (W–M) fractal function. The W–M fractal function is then used to generate simulated Bi2212/Ag microstructures. Finally, the mechanical behavior of the microstructures is investigated. It is found that the interfilamentary bridges which play a significant role in Bi2212 transport are not likely to be the cause of electromechanical degradation and failure. Instead, large stress concentrations are identified at the concave tips that occur along the jagged Bi2212/Ag interface. In particular, locations where the concave tips are within the Bi2212 filament are the likely initiation points of failure in Bi2212 RWs.