TTwo sample materials with different graphite distributions were investigated with two-dimensional local number analysis (LN2D) and Voronoi tessellation. The first was a sample with general graphite distribution, and the other was a sample with abnormal graphite distribution such as closely lineated graphite particles, which was obtained by graphitized heat treatment of chilled sample castings. The randomness and alignment of distributed spherical graphite particles have been reported to be effectively quantified by LN2D. In this study, the randomness and alignment of distributed graphite in Voronoi analysis were effectively quantified by the average and standard number of deviations of that area. In addition, the values of graphite distribution in Voronoi analysis were evaluated by comparing with impact characteristics. When the distributed graphite particles were highly aligned, the impact characteristics showed a higher ratio of crack initiation energy to impact absorption energy, resulting in increased brittleness of spheroidal graphite cast iron. Numerous secondary cracks were observed in the area where distributed graphite particles were highly aligned in the samples after impact test. It was concluded that such aligned distribution of graphite morphology causes brittleness in spheroidal graphite cast iron.
