Microstructural characterization and modeling of discontinuously-reinforced aluminum composites

Models for predicting the constitutive behavior of spatially-heterogeneous microstructures such as discontinuously-reinforced aluminum (DRA) and other metallic matrix composites based on unit cell approaches generally do not incorporate higher-order microstructural features such as degree of homogeneity and spatial anisotropy of the reinforcement phase. Moreover, more complex numerical models rarely encompass the volumes of material necessary to ensure statistical relevance. The present contribution offers an alternative approach for quantifying and then incorporating the microstructural homogeneity of these materials within an elastic-plastic finite element code. An attempt is made to model both the micromechanical length scale associated with the individual reinforcement particles and the microstructural length scale associated with their spatial distribution, at a greatly-reduced computational expense, by using a volume-averaged, discretized approach. A key assumption in this approach is that below the length scale of the discretization, the microstructure can be modeled by a uniform array of reinforcement particles. The effect of the level of discretization on predictions of microstructure-property relationships are not addressed directly in the present work. Detailed comparisons of the present model with discretely-modeled matrix-particle geometries will therefore form the basis of a subsequent publication. Nevertheless, several microstructure-property relationships are developed which reveal empirical relationships between microstructural homogeneity and the elastic-plastic response.