Materials Science and Engineering A265 (1999) 153 – 173 Three dimensional characterization and modeling of particle reinforced metal matrix composites: part I Quantitative description of microstructural morphology M. Li a , S. Ghosh a, *, O. Richmond b , H. Weiland b , T.N. Rouns b a Ohio State Uniersity, Department of Aerospace Engineering, Applied Mechanics and Aiation, 209 Boyd Laboratory, 155 West Woodruff Aenue, Columbus OH 43210, USA b ALCOA Technical Center, Pittsburgh PA 15069, USA Received 24 June 1998; received in revised form 16 November 1998 Abstract In this first of a two part sequence of papers, 3-D microstructures of Si particle reinforced aluminum matrix composites are computationally constructed by assembling digitally acquired micrographs obtained by serial sectioning. The material samples considered vary in volume fraction and in particle size. Furthermore, equivalent microstructures with actual particles replaced by ellipses (in 2-D) or ellipsoids (in 3-D) are computationally simulated for efficiency. The equivalent microstructures are tessellated by a particle surface based algorithm into a mesh of Voronoi cells. Various 3-D characterization functions are developed to identify particle size, shape, orientation and spatial distribution in the actual materials and to compare with 2-D micrographs. Through this analysis, differences between 2- and 3-D characterization are established. Results indicate that it may not be sufficient to use 2-D section information for characterizing detailed microstructural features like particle shapes, orientations and near-neighbor distances. The second part of this sequence of papers will describe the important relationship of these features to damage evolution in these same materials. This sequence of papers is perhaps one of the first on 3-D physical characterization of the phase and damage structure for this class of materials. © 1999 Elsevier Science S.A. All rights reserved. Keywords: Composites; Matrix; Microstructure; Morphology 1. Introduction Particle and fiber reinforced composite materials have received considerable attention for use in many engineering systems due to their potential in improving mechanical properties, as well as in reducing life-cycle costs through enhanced thermomechanical stability and weight reduction. The degree of property enhancement depends on morphological factors such as volume frac- tion, size, shape and spatial distribution of the rein- forcements, in addition to the constituent material and interface properties. Various experimental and numeri- cal studies have established that the deformation and damage behavior of multi-phase materials can be highly sensitive to local morphology, especially by its effect on nonhomogeneous deformation. For example, Brocken- brough et. al. [1] have concluded that the effect of fiber distribution is significant at lower volume fractions, Christman et. al. [2] have shown that clustering has a significant effect in reducing flow stress and strain hardening and Nan and Clark [3] have revealed that deformation response is affected by size, size distribu- tion and volume fraction of particles. Using the Voronoi cell finite element model, Ghosh and Moorthy [4,5] have examined the effect of various morphologies on the damage initiation and evolution process in duc- tile matrix composites. In the experimental studies of Hunt and co-workers [6,7], Lewandowski and co-work- ers [8–16], Llorca et. al. [17], Mummery et. al. [18] and Embury-and co-workers [19], the effect of particle vol- ume fraction, size, shape, spatial distribution, material properties and stress state on deformation, damage and failure processes of ductile matrix composites are * Corresponding author. Tel.: +1-614-2922599; fax: +1-614- 2927369. E-mail address: ghosh@osu.edu (S. Ghosh) 0921-5093/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved. PII:S0921-5093(98)01132-0