θ′ Precipitates strengthening in Al-Cu alloy considering orientation and spatial distribution: A discrete dislocation dynamics study

Abstract

Precipitates contribute significantly to the strength of many common engineering aluminum alloys. The stress orienting effect of disk-shaped θ′ precipitates in Al-Cu alloy may lead to varying orientation distribution of the precipitates and, thus, varying critical resolved shear stress (CRSS) and macroscopic mechanical properties. In this work, θ′ precipitates was incorporated into discrete dislocation dynamics (DDD) simulation software ParaDiS. This approach was applied to systematically investigate how CRSS is affected by the orientation distribution and spatial distribution of the θ′ precipitates which has a considerable effect on the CRSS but has received less attention in previous research. As a simplification, the orientation distribution of a one-dimensional equidistantly distributed sequence of precipitates are taken as the research object. By varying the orientation of each precipitate, DDD simulations with wide range of overall orientation distributions can be obtained. Based on this, we propose an orientation factor that can adequately define the relationship between the orientation distribution and the CRSS. A modified Orowan model considering orientation distribution with parameters calibrated by dislocation dynamics simulations is suggested in light of these investigations, enabling rapid prediction of CRSS. Subsequently, the spatial distribution of precipitates was described using the extreme distribution, and a spatial factor was created by examining the mean and variance. This model was extended to the case of complex precipitate distributions by considering the spatial factor. The accuracy of the extended model was verified through DDD simulation results for randomly distributed precipitates and the prediction accuracy was greatly improved. This work makes it possible to calculate precipitation strengthening in Al-Cu alloys quantitatively and precisely while accounting for specific orientation distribution and spatial distribution.