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The interaction between edge dislocations and Guinier-Preston zones in anAl-Cu alloy was analyzed by means of atomistic simulations. The differentthermodynamic functions that determine the features of these obstacles for thedislocation glide were computed using molecular statics, molecular dynamics andthe nudged elastic band method. It was found that Guinier-Preston zones aresheared by dislocations and the rate at which dislocations overcome theprecipitate is controlled by the activation energy, $\Delta U$, in agreementwith the postulates of the harmonic transition state theory. Moreover, theentropic contribution to the Helmholtz activation free energy was in the range1.3-1.8$k_b$, which can be associated with the typical vibrational entropy ofsolids. Finally, an estimation of the initial shear flow stress as a functionof temperature was carried out from the thermodynamic data provided by theatomistic simulations. Comparison with experimental results showed that theeffect of the random precipitate distribution and of the dislocation characterand dislocation/precipitation orientation has to be taken into account in thesimulations to better reproduce experiments.

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