A phase mixture model of a particle reinforced composite with fine microstructure

A phase mixture model is considered in which a mechanically alloyed, particle reinforced metal matrix composite with ultrafine microstructure is treated as a mixture of a matrix phase, a reinforcing particle phase and a boundary phase. The finite element method is employed in conjunction with a unit cell of the composite to investigate the compressive and tensile behaviour of the system. The reinforcing ceramic particles are taken to be elastic. A unified constitutive model based on dislocation density evolution is used to describe the plastic flow behaviour of the matrix; grain size effects are included. A yield criterion for porous materials, including the evolution of density, is applied to the boundary phase. The boundary phase is assumed to have the mechanical properties of a quasi-amorphous material. The effects of the volume fraction of the reinforcing particles, overall effective density, grain size of the matrix, and the density of the boundary phase on the overall mechanical properties are discussed. The calculated stress-strain curves based on the unit cell model are used to simulate an indentation test and are compared with experimental measurements on Al-alumina composites. (C) 2000 Elsevier Science S.A. All rights reserved.