Multiscale Modeling of Inclusions and Precipitation Hardening in Metal Matrix Composites: Application to Advanced High-Strength Steels

Abstract

The strengthening effect of precipitates in metals is investigated within a multiscale approach that utilizes models of various length scales; namely, molecular mechanics (MM), discrete dislocation dynamics (DD), and an equivalent inclusion method (EIM). In particular, precipitates are modeled as particles whose stress fields interact with dislocations. The stress field resulting from the elastic mismatch between the particles and the matrix is accounted for by using the EIM, whereas the MM method is employed to develop rules for the DD method for short range interactions between a single dislocation and an inclusion. The DD method is used to predict the strength of the composite structure resulting from the interaction between ensembles of dislocations and particles. As an application to this method, the mechanical behavior of advanced high strength steel is investigated and the results are compared to the experimental data published in previous studies. The results show that the finely dispersive precipitates can strengthen the material by pinning the dislocations up to a threshold shear stress and retarding the recovery, in addition to annihilating the dislocations. The DD results show that strengthening due to nanosized particles is a function of the density and size of the precipitates. This size effect is explained by using a mechanistic model developed on the basis of dislocation particle interaction.