A novel method for the characterisation of directionally solidified dendritic arrays

Abstract

The primary dendrite arm spacing (PDAS) is one of the main characteristic parameters of directionally solidified dendritic structures. It is widely used to characterise as-cast structures and to correlate them with the local solidification conditions. Although, common use seems to refer to a unique relationship between solidification conditions and PDAS, it has been widely accepted that there exists a distribution of spacings in a dendritic array. In the present work a novel method for the determination of the PDAS is proposed, which yields the average PDAS, its distribution and the number of nearest neighbours. These quantities - which can be used to characterise dendritic arrays - are obtained by determining the centre of gravity of all dendrites in the array under consideration and then applying a specially designed algorithm to identify the nearest neighbours of each dendrite. The characteristics of the method are demonstrated by applying it to test structures and dendritic structures obtained from directional solidification experiments.