Dislocation dynamics analysis of the strengthening induced by shearable and non-shearable precipitates in the presence of dislocation pile-ups

Abstract

The effect of dislocation pile-ups on the critical resolved shear stress necessary to overcome a regular distribution of circular precipitates has been analyzed by means of dislocation dynamics simulations. Both precipitates that can and cannot be sheared by dislocations have been considered. Hardening increases with the number of dislocations in the pile-up in the case of impenetrable precipitates due to the back-stress while shearable precipitates are eventually cut by dislocations if enough Orowan loops are piled-up against the precipitate. Analytical expressions for the critical resolved shear stress to overcome both impenetrable and shearable precipitates were developed based on the concept of an effective diameter as a function of the number of dislocations in the pile-up and of the friction stress to shear the precipitate.