This work examines the interaction of screw dislocations with Guinier–Preston zones using atomistic simulations. Both Orowan looping and cross-slip mechanisms were found to control the interactions. The orientation dependence, and its dependence upon temperature, provided a micromechanical explanation for the experiments of Muraishi et al. (2002). The atomistic simulations highlighted the importance of dislocation cross-slip in precipitation hardening. It was found that cross-slip could either decrease or increase the hardening effect of precipitates, depending upon whether the cross-slip plane was impeded by the precipitate. Cross-slip was observed to occur at both 0 and 300K, suggesting that it could occur in the absence of thermal activation. The importance of cross-slip in precipitation hardening was highlighted when considering the simulation results in the context of experimental data which could not be explained solely by edge dislocation precipitate interactions. When cross-slip did not occur or did not provide an unimpeded plane for the dislocation to overcome the precipitate, Orowan looping was observed in 0K simulations. Considering that the precipitates were Guinier–Preston zones, this was in contrast to the long-held continuum view that dislocations overcome small precipitates by cutting. This analysis, in combination with previous work, laid the foundation for the atomistic-based modelling of age-hardening.

Atomistic Simulations of Dislocation–Precipitate Interactions Emphasize Importance of Cross-Slip. C.V.Singh, A.J.Mateos, D.H.Warner: Scripta Materialia, 2011, 64[5], 398-401