Leff A C, Weinberger C R, Taheri M L
Department of Materials Science & Engineering, Drexel University, Philadelphia, PA, USA.
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
Ultramicroscopy. 2015 Jun;153:9-21. doi: 10.1016/j.ultramic.2015.02.002. Epub 2015 Feb 10.
The Nye tensor offers a means to estimate the geometrically necessary dislocation density of a crystalline sample based on measurements of the orientation changes within individual crystal grains. In this paper, the Nye tensor theory is applied to precession electron diffraction automated crystallographic orientation mapping (PED-ACOM) data acquired using a transmission electron microscope (TEM). The resulting dislocation density values are mapped in order to visualize the dislocation structures present in a quantitative manner. These density maps are compared with other related methods of approximating local strain dependencies in dislocation-based microstructural transitions from orientation data. The effect of acquisition parameters on density measurements is examined. By decreasing the step size and spot size during data acquisition, an increasing fraction of the dislocation content becomes accessible. Finally, the method described herein is applied to the measurement of dislocation emission during in situ annealing of Cu in TEM in order to demonstrate the utility of the technique for characterizing microstructural dynamics.
奈伊张量提供了一种基于对单个晶粒内取向变化的测量来估计晶体样品几何必要位错密度的方法。在本文中，奈伊张量理论被应用于使用透射电子显微镜（TEM）获取的进动电子衍射自动晶体取向映射（PED - ACOM）数据。所得的位错密度值被映射，以便以定量方式可视化存在的位错结构。这些密度图与从取向数据近似基于位错的微观结构转变中局部应变依赖性的其他相关方法进行了比较。研究了采集参数对密度测量的影响。通过在数据采集期间减小步长和光斑尺寸，越来越多的位错含量变得可获取。最后，本文所述方法被应用于TEM中铜原位退火过程中位错发射的测量，以证明该技术在表征微观结构动力学方面的实用性。
