An atomistic investigation of the interaction of dislocations with Guinier-Preston zones in Al-Cu alloys

TL;DR

This study uses atomistic simulations to analyze how dislocations interact with Guinier-Preston zones in Al-Cu alloys, revealing shearing behavior and thermodynamic factors influencing dislocation motion.

Contribution

It provides a detailed atomistic analysis of dislocation-precipitate interactions, including thermodynamic functions and activation energies, advancing understanding of deformation mechanisms in Al-Cu alloys.

Findings

Guinier-Preston zones are sheared by dislocations.

Dislocation overcoming rate is controlled by activation energy.

Thermodynamic data estimate initial shear flow stress.

Abstract

The interaction between edge dislocations and Guinier-Preston zones in an Al-Cu alloy was analyzed by means of atomistic simulations. The different thermodynamic functions that determine the features of these obstacles for the dislocation glide were computed using molecular statics, molecular dynamics and the nudged elastic band method. It was found that Guinier-Preston zones are sheared by dislocations and the rate at which dislocations overcome the precipitate is controlled by the activation energy, $\Delta U$, in agreement with the postulates of the harmonic transition state theory. Moreover, the entropic contribution to the Helmholtz activation free energy was in the range 1.3-1.8$k_b$, which can be associated with the typical vibrational entropy of solids. Finally, an estimation of the initial shear flow stress as a function of temperature was carried out from the thermodynamic data provided by the atomistic simulations. Comparison with experimental results showed that the effect of the random precipitate distribution and of the dislocation character and dislocation/precipitation orientation has to be taken into account in the simulations to better reproduce experiments.