FINITE ELEMENT ANALYSIS OF THE EFFECT OF PARTICLE ALIGNMENT ON THE DEFORMATION BEHAVIOR FOR A DUCTILE MATRIX CONTAINING HARD PARTICLES SAFAK YILMAZ and AHMET ARAN Faculty of Mechanical Engineering, Istanbul Technical University, Gumussuyu-Taksim, 80191, Istanbul, Turkey (Received 1 April 1999 ; in revised form 1 August 1999 ; accepted 1 August 1999) AbstractÐThe goal of this work is to determine the role of the particulate alignment on the overall de- formation behavior of metal matrix composites. Stress±strain behavior of hard particle-ductile matrix materials were analyzed using ®nite elements method. The eects of volume fraction and distribution geometry of particles were investigated. The composite microstructure was assumed to be a 3-D in®nite periodic array of spherical particles embedded in the matrix. Transversely aligned and staggered unit cell approximations were used for analyzing the particle distribution geometry eects. The eect of par- ticle alignment on the overall stress±strain behavior of the composites was followed through unit cells having dierent aspect ratios. The strengthening and strain hardening in the hard particle-ductile matrix composite system were found to be controlled primarily by the volume percent reinforcement. Distri- bution geometry of reinforcement as represented by that the ratio of particle diameter to distance between nearest neighbor particles also has great eect on deformation behavior. # 1999 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved. Re sume ÐLe but de ce travial est de deÂterminer le roÃle de l'alignement des particules sur le comporte- ment global de deÂformation de composites aÁ matrices meÂtalliques. On a analyse le comportement de contrainte±deÂformation de mateÂriaux aÁ particule dure et aÁ matrice ductile en utilasant la meÂthode aux eÂleÂments ®nis. On a eÂvalue les eets de la fraction de volume et de la fraction de volume et de la geÂo- metrie de distribution des particules. On a assume que la microstructure du composite consistait en un arrangement peÂriodique in®ni aÁ 3-D de particules spheÂriques encastreÂes dans la matrice. On a utilise des approximations d'uniteÂs cellulaires aligneÂes transversalement et en zigzag pour analyser les eets de la geÂomeÂtrie de la distribution. On a suivi l'eet de l'alignement des particules sur le comportement glo- bal de contrainte±deÂformation des composites, aÁ travers les uniteÂs cellulaires ayant diverses proportions. On a trouve que le renforcement et le durcissement par contrainte du systeÁme composite particule dure- matrice ductile eÂtaient controÃleÂs principalement par le pour-cent en volume du renforcement. La geÂomeÂ- trie de distribution du renforcement, telle que repreÂsenteÂe par le rapport du diameÁtre de particule aÁ la distance entre les particules voisines le splus proches, avait aussi un grand eet sur le comportement de de formation. # 1999 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved. INTRODUCTION Materials with a ductile matrix containing hard particles are attractive materials for many engineering applications. Dual phase alloys and particle-reinforced metal matrix composites are examples of such materials. The ductility and fracture toughness of hard particle-ductile matrix materials are lower, compared with that of the unreinforced matrix materials, but improvements can be achieved in their elastic moduli and strength depending on stiness of the hard particle [1]. The strengthening arises mainly due to the constraint deformation of the matrix because of the hard phases [2, 3]. In order to predict the overall stress±strain behavior of composite materials or to design new materials, the eects of microstructural parameters on the composite behavior should be well understood. The properties of dual phase materials depend on ``natural'' and ``geometrical'' parameters of microstructures [4]. The mechanical properties of constituent phases and character of the interface are classi®ed as ``natural parameters''. The ``geometrical parameters'' are the volume fraction, shape, size and distribution geometry of the phases. Experimental studies [5, 6] and ®nite element analyses [3, 7] have shown that non-homogeneous stress and strain distributions occur in the composite microstructure due to the dierences in the phase behaviors. The stress and strain distribution occurs non-homogeneously not only between two constituents but also in the same phase. There are two main approaches for interpreting the mechanical properties of these materials. One is the ``micro-mechanistic'' approach Canadian Metallurgical Quarterly, Vol. 38, No. 3, pp. 201±205, 1999 # 1999 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd Printed in Great Britain. All rights reserved 0008-4433/99 $19.00+0.00 PII: S0008-4433(99)00017-8 *Corresponding author. E-mail: s-yilmaz@nwu.edu. 201