Origin of the yield stress anomaly in L12 intermetallics unveiled with physically informed machine-learning potentials

The yield stress anomaly of L1 2 intermetallics such as Ni 3 Al, Ni 3 Ga, Co 3 (Al,W) 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 this anomalous behavior in L1 2 -strengthened alloys, 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 modeling of the dislocation behavior in Ni 3 Al 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 L1 2 intermetallics. The acquired knowledge of KWLs provides a deeper understanding on the origin of the yield stress anomaly.