Skeletonisation to Find the Centre of Dendrites Traced from a 2D Microstructural Image

As three-dimensional analysis of dendritic microstructures (such as Ni-superalloys) has become more prevalent with the use of techniques such as Robomet, synchrotron and computerised tomography, there has been a greater need for accurate and efficient methods to characterise dendrites in three dimensions. One parameter which is needed for a variety of further calculations is the primary dendrite arm spacing (λ_1). This parameter can be calculated by finding the distances between all of the centres of the dendrites on a single plane. However before this can be computed the locations of all these centres must be obtained. One technique which has often been used in the literature is the centre of geometry method, which simply determines the centre of gravity of each dendrite as seen in a micrograph. However, this method has some major drawbacks. For instance it can assign the centre outside of a dendrite, which often applies to irregular shaped dendrites. As a result another technique shall be presented using skeletonisation. It is shown here that this technique represents good improvement over the centre of geometry method; however it also has drawbacks in certain specific conditions. Combined use of all these methods however shows promise in the search for a reliable method to identify the centres of differently shaped dendrites.