Atomistic mechanism and probability determination of the cutting of Guinier-Preston zones by edge dislocations in dilute Al-Cu alloys

Abstract

The interaction between a ${}^{1}/{}_{2}\left[\overline{1}10\right]\left(111\right)$ edge dislocation and a (001) Guinier-Preston (GP) zone in dilute Al-Cu alloys is studied via atomistic modeling. In stark contrast to the previously reported Orowan looping mechanism where the GP zone remains intact after yield, we discover a competing mechanism where the dislocation cuts the GP zone into two pieces. We identify the key atomic process triggering the cutting mechanism and calculate its activation barrier at various strains. In further conjunction with the transition state theory, the occurrence probability of a trigger event is mapped out over a broad range of $T\text{---}\stackrel{\ifmmode \dot{}\else \.{}\fi{}}{\ensuremath{\varepsilon}}$ parameter space. The predictions of the so-constructed mechanism map are validated by parallel MD simulations. The implications of our findings regarding the discrepancies between the existing age hardening model and experiments are also discussed.