The measurement of the dislocation density using TEM

The line intercept method is well developed for estimating the dislocation density in metals, but its application is limited by the intersection counting, which is deeply depending on the TEM image quality. Manual interscetion counting is quite time and labor consuming. If most of the dislocations has good contrast and homogenous background in an image, it is possible to perform automatic counting by the computer program. In this work a series of imaging conditions were investigated on a slightly deformed IF steel thin foil. Though the invisibility criterion remains applicable for both the conventional transmission electron microscopy (CTEM) and the scanning transmission electron microscopy (STEM), the STEM images revealed more dislocations and had more homogenous background than the CTEM images. The STEM bright field (BF), annular dark field (ADF) and annular bright field (ABF) images at a low index zone axis contained the most dislocations visible and were suitable for automatic intersection counting of dislocations.