In this study, the influence of particles size on the work hardening of low carbon steels with composite-type microstructures has been studied. A micromechanical model has been developed to predict the isotropic and kinematic contributions to work hardening of these steels based on the microstructural features including the particles radius and volume fraction as well as the matrix grain size. It was found that for the same volume fraction of particles, the isotropic work hardening caused by fine particles is greater than that of coarse particles. On the other hand, coarse particles exhibit the main contribution to kinematic work hardening as a result of the relaxation of a relatively lower amount of plastic misfit strain. The effect of bimodal particle size distribution on the work hardening was also evaluated. Although the addition of a certain amount of fine particles to the steel microstructures containing coarse particles has a main role in the enhancement of isotropic contribution to work hardening, they have a slight influence on the uniform strain. In addition, the isotropic and kinematic contributions to work hardening behavior of fine particles increase in the presence of coarse particles.

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