  The yield stress anomaly of L12 intermetallics such as Ni3Al or Ni3Ga is
controlled by the so-called Kear-Wilsdorf lock (KWL), of which the formation
and unlocking are governed by dislocation cross-slip. Despite the importance of
L12 intermetallics for strengthening Ni-based superalloys, microscopic
understanding of the KWL is limited. Here, molecular dynamics simulations are
conducted by employing a dedicated machine-learning interatomic potential
derived via physically-informed active-learning. The potential facilitates
modelling of the dislocation behavior in Ni3Al with near ab initio accuracy.
KWL formation and unlocking are observed and analyzed. The unlocking stress
demonstrates a pronounced temperature dependence, contradicting the assumptions
of existing analytical models. A phenomenological model is proposed to
effectively describe the atomistic unlocking stresses and extrapolate them to
the macroscopic scale. The model is general and applicable to other L12
intermetallics. The acquired knowledge of KWLs provides a deeper understanding
on the origin of the yield stress anomaly.
