Overdriven dislocation-precipitate interactions at elevated temperatures

Abstract

The two-dimensional dislocation dynamics approach has been recently used for analyzing plastic deformation in metals and alloys at elevated temperatures. The two-dimensional approach, however, only accounts for the dislocation climbing process, and it assumes that dislocation bypassing and shearing of precipitates are negligible. To examine the validity of this assumption, the present study quantifies dislocation bypassing and shearing of precipitates in terms of critical resolved shear stress, interaction time, and thermal activation energy for various precipitate strength levels, temperatures, and precipitate spacings. This study uses a modified dislocation dynamics approach that accounts for shearable and non-shearable precipitates. Simulations focus on the overdriven dislocation dynamics regime wherein the climbing process is limited by fast interactions between dislocations and precipitates. The results show that even though the resolved shear stress level required for a dislocation to overcome an array of precipitates decreases at higher temperatures, the interaction time between the dislocation and the precipitates increases. In addition, the maximum ratio of thermal activation energy to the precipitate energy barrier is only 0.15.