Large scale point covariance analysis of homogeneity in TiB2-Fe composites
Abstract
Image analysis of a sintered TiB2-Fe hard material has been performed. The porosity dispersion is discussed from size and covariance function measurements. An extension of the usual point covariance analysis was made by implanting series of 10 contiguous segmentation fields, and making measurements of the linear covariance function in the direction of field alignment. The maximum correlation distance of the analysis was then increased by a factor of 10, as compared to a usual analysis with the same resolution. The method is an alternative to the regularized covariance analysis (Hersant and Jeulin, 1976).
A two scale boolean model is proposed to interpret variations of the measured covariance function from the origin to its asymptotic limit. Using the model, porosity can be represented either by 20-30 µm clusters, or by the complementary phase of 30-50 µm (grains+binder) clusters, which should have been formed during the elaboration process.