Discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened (ODS) steels

A discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened (ODS) steels was described. Parametric dislocation dynamics (PDD) simulation of the interaction between an edge dislocation and randomly distributed spherical dispersoids (Y₂O₃) in bcc iron was performed for measuring the influence of the dispersoid distribution on the critical resolved shear stress (CRSS). The dispersoid distribution was made using a method mimicking the Ostwald growth mechanism. Then, an edge dislocation was introduced, and was moved under a constant shear stress condition. The CRSS was extracted from the result of dislocation velocity under constant shear stress using the mobility (linear) relationship between the shear stress and the dislocation velocity. The results suggest that the dispersoid distribution gives a significant influence to the CRSS, and the influence of dislocation dipole, which forms just before finishing up the Orowan looping mechanism, is substantial in determining the CRSS, especially for the interaction with small dispersoids. Therefore, the well-known Orowan equation for determining the CRSS cannot give an accurate estimation, because the influence of the dislocation dipole in the process of the Orowan looping mechanism is not accounted for in the equation.