Effect of Particle Size Distribution on the Response of Metal-Matrix Composites
An enhanced continuum model for ceramic particle reinforced metal matrix composites (MMCs) is used to explore the effect of particle size distribution on the variability in deformation response of heterogeneous microstructures. The model incorporates part
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Effect of Particle Size Distribution on the Response of Metal-Matrix Composites Brandon McWilliams, K.T. Ramesh, and C. Yen
Abstract An enhanced continuum model for ceramic particle reinforced metal matrix composites (MMCs) is used to explore the effect of particle size distribution on the variability in deformation response of heterogeneous microstructures. The model incorporates particle size dependent strengthening through a “punched” zone around the particles that is the result of an increase in dislocation density due to geometrically necessary dislocations generated by the mismatch in coefficients of thermal expansion of the particle and matrix. In this work, these zones are explicitly accounted for in mesoscale finite element simulations of representative heterogeneous composite microstructures consisting of randomly distributed particles in a metal matrix. Additionally, particle-matrix interface decohesion is incorporated through the use of cohesive zones. The results demonstrate that in the absence of material failure, the mean particle size of a distribution is sufficient to predict the elastic–plastic response with nominal variance in the response of the composite. The effect of interface strength on particle stresses is quantified and shown to reduce particle fracture in distributions containing large particles. Keywords Metal matrix composite • MMC • Modeling • Particle reinforcement
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Introduction
Ceramic particle reinforced metal matrix composites (MMCs) offer the potential for enhanced stiffness and yield strength over conventional lightweight structural alloys. A tradeoff in properties typically develops because high stiffness and/or strength is achieved by increasing the volume fraction of reinforcement particles, which often results in a significant decrease in ductility of the composite. This reduced ductility has thus limited the use of MMCs in structural applications. Therefore it is desirable to identify and understand the effect of heterogeneous microstructure design variables such as particle size, particle size distributions, particle morphology, and spatial distributions of particles, to narrow the design space and achieve higher strength/stiffness along with enhanced ductility. The main strengthening mechanism in MMCs is load transfer from the matrix to the reinforcement and can be successfully modeled using classical continuum homogenization techniques [1]. However, for a given volume fraction of reinforcement it has been experimentally shown that the magnitude of strengthening is inversely proportional to the reinforcement size [2, 3]. Particle size dependent strengthening arises from several sources, which include the inherent size dependence of the strength of the ceramic particles due to the higher probability of larger particles more likely to have flaws of critical size, and from quench hardening (dislocation punching) due to mismatch between the coefficients of thermal expansion of the particles and matrix [2]. The dominant mechanism for particle size dependence at small s
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