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

Abstract

We investigate the prolonged plastic deformation of aluminum containing θ’ 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 θ’ 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 θ’ 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 θ’ 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 θ’ phases corresponding to the possible decrease in flow stress is distinguished.

Effect of Copper Segregation at Low-Angle Grain Boundaries on the Mechanisms of Plastic Relaxation in Nanocrystalline Aluminum: An Atomistic Study

“…Classical molecular dynamics is performed with the LAMMPS package [20]. Interactions of atoms are described with an angle-dependent potential (ADP) by Apostol and Mishin [21], which is widely used in the description of the Al-Cu alloy's properties [22][23][24][25][26], since it reproduces with a sufficient accuracy the elastic constants and energies of various defects in both these metals and their intermetallic phases. In addition, this potential is rather resource-efficient, allowing one to use it in MD simulations of systems containing millions of atoms.…”