Finite Element analyses of the effect of particle size on the stress and strain fields in an Al-22 wt pct Si alloy (d=100um) are performed. The alloy was ,modified by a nucleant to obtain a more refined structure with smaller particle size (d=251.im). The general interaction between the inhomogeneity and matrix is characterized by: firstly, a hard inclusion creates a high perturbation of triaxial stress at the poles along the line of loading; secondly a hard inhomogeneity carries higher stress than the matrix; the stress level in the particle is determined by the misfit of the two phases; thirdly all the perturbation fields are scaled by inclusion size; finally a correlation has been made between the stress concentration in the matrix and the size of the in homageneity.