Influence of θ′ Phase Cutting on Precipitate Hardening of Al-Cu Alloy during Prolonged Plastic Deformation: Molecular Dynamics and Continuum Modeling

We investigate the prolonged plastic deformation of aluminum containing theta' phase with a multistage approach combining molecular dynamics (MD), continuum modeling (CM) and discrete dislocation dynamics (DDD). The time of performed MD calculations is sufficient for about a hundred dislocation-precipitate interactions. With this number of interactions, the inclusion of theta' is not only cut, but also scattered into individual copper atoms in an aluminum matrix. Damage to the crystal structure of inclusion and activation of the cross-slip of dislocation segments cause a decrease in acting stresses in the MD system. The rate of this effect depends on theta' diameter and occurs faster for small inclusions. The effect of decreasing the resistance of precipitate is further introduced into the dislocation-precipitate interaction CM by reducing the precipitate effective diameter with an increase in the number of interactions. A model of dislocation-precipitate interaction accounting for the softening of inclusions is further implemented into DDD. Dependences of flow stress in aluminum with theta' phases on volume fraction and typical diameter of precipitates are obtained. Manifestation of inclusion softening is possible in such an alloy, which leads to the flow stress decrease during deformation. The range of volume fractions and typical diameters of theta' phases corresponding to the possible decrease in flow stress is distinguished.

Automated summary

The study investigates the prolonged plastic deformation of aluminum containing theta' phase using a multistage approach combining MD, CM, and DDD. It is found that damage to the crystal structure of inclusions and activation of cross-slip of dislocation segments lead to a decrease in acting stresses in the MD system. The softening effect of inclusions is further introduced into the dislocation-precipitate interaction, causing a decrease in flow stress during deformation.