Novel methods for dislocation density estimation in highly compacted tangles

Dislocation lines are usually observed in thin foil images obtained by transmission electron microscopy (TEM). Based on conventional methods involving stereological relationship and line counting, dislocation densities have been calculated in distinct materials, mostly in plastically deformed metals and alloys. However, under certain plastic deformation conditions, such as those associated with dynamic strain aging (DSA), dislocation arrangements may develop highly compact tangles. Inside DSA dense tangles, the individual identification of lines for stereological counting becomes impracticable. In the present work, two novel methods to estimate dislocation densities in highly compact tangles are proposed. The first method is exemplified in TEM images of cells and banded walls substructure of an austenitic stainless steel plastically deformed under DSA condition. In a second method, the average dislocation density of such TEM images is proposed to be calculated by the proportional sum of area fractions multiplied by corresponding dislocation densities of visible dislocation and highly compact tangle areas as well as dislocation-free area.