A method to characterize the roughness of 2‐D line features: recrystallization boundaries

Summary A method is presented, which allows quantification of the roughness of nonplanar boundaries of objects for which the neutral plane is not known. The method provides quantitative descriptions of both the local and global characteristics. How the method can be used to estimate the sizes of rough features and local curvatures is also presented. The potential of the method is illustrated by quantification of the roughness of two recrystallization boundaries in a pure Al specimen characterized by scanning electron microscopy. Lay description Rough features on various length scales are typical in most materials. Examples are fracture surface, interfaces in composite materials, second phase particles, for example, graphite nodules in cast iron, boundaries surrounding recrystallizing grains and dislocation boundaries. The degree of roughness generally depends on the processing of the materials and may be of importance for the structural evolution and properties of the material. Standard methods to quantify roughness, like profilometer measurement and fractal analysis suffer from serious limitations and in the present paper a new method based on digital image analysis is proposed. The new method is applicable on all length scales, and is not affected by a possible directionality of the objects and it provides global as well as local information. In the paper, the potential of the new method is illustrated by an analysis of boundaries surrounding two recrystallizing grains. The results reveal that the local boundary roughness/curvature may provide local driving force of the same order of magnitude as that from the energy stored in the deformed matrix. This is contradictory to common recrystallization theories.