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

Aug 5, 2026

The yield stress anomaly of L12 intermetallics such as Ni3Al, Ni3Ga, and Co3(Al,W) is governed by the Kear–Wilsdorf lock (KWL), whose formation and unlocking are controlled by dislocation cross-slip. To address limited microscopic understanding, dedicated molecular dynamics simulations are performed using a physically informed machine-learning interatomic potential derived via active learning. The simulations reproduce Ni3Al dislocation behavior near ab initio accuracy, reveal KWL formation/unlocking, and show unlocking stress with strong temperature dependence. A phenomenological model is proposed to describe atomistic unlocking and extrapolate to macroscopic scales.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages10

Reading Time25 min

AccessFree to download

Introduction

Yield stress anomaly and its technological context

Kear–Wilsdorf lock and dislocation core evolution

Existing analytical models and limitations

Need for atomistic simulations and machine-learning potentials

| Full length article
Origin of the yield stress anomaly in L12 intermetallics unveiled with physically informed machine-learning potentials
Xiang Xu a,b,∗, Xi Zhang a,∗, Erik Bitzek c, Siegfried Schmauderb, Blazej Grabowski aa Institute for Materials Science, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
b Institute for Materials Testing, Materials Science and Strength of Materials, University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart, Germany c Computational Materials Design, Max Planck Institute for Sustainable Materials, Max –Planck-Straße 1, 40237, Düsseldorf, Germany | | | | --- | --- | --- | | A R T I C L E I N F O | A B S T R A C T
The yield stress anomaly of L12 intermetallics such as Ni3Al, Ni3 Ga, Co3 (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 L12-strengthened alloys, microscopic understanding of the KWLis 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 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. | | | Dataset link: [https://doi.org/10.18419/darus-4](https://doi.org/10.18419/darus-4)[ ](https://doi.org/10.18419/darus-4)480 | | | | Keywords:
Yield stress anomaly
Dislocation cross-slip
L12 intermetallics
Molecular dynamics simulations Machine-learning potentials | | | 1. Introduction Ni-based superalloys are used for turbine blades because they withstand thermal mechanical loading under high turbine-entry temperatures [1,2]. Over several generations of these superalloys and corresponding thermal barrier coatings, the turbine-entry temperatures have increased by 700 K [3], significantly improving the thermodynamic efficiency of aircraft engines. The outstanding thermal resistance mainly originates from a high volume fraction of L12-ordered precipitates. In contrast to common structural materials, the yield stress of certain L12 intermetallics, e.g., Ni3Al [4], Ni3 Ga [5], or Co3 (Al,W) [6], increases with temperature, typically accompanied with an anomalously increasing work-hardening rate. As this so-called yield stress anomaly (YSA) is pivotal for strengthening advanced alloys, the steady increase of understanding YSA has been a key ingredient to the evolution of Nibased superalloys [1,2,7] and Co-based superalloys [8–10], and also for the development of L12 strengthened high-entropy alloys [11,12]. However, the origin of YSA is still not satisfactorily clarified [7]. What is known from transmission electron microscopy (TEM) on samples deformed in the temperature region of the YSA [13,14] is that the dislocations in Ni3Al exhibit a unique non-planar dislocation core structure—nowadays referred to as the Kear–Wilsdorf lock (KWL). The dislocation core was shown to evolve through cross-slip [15,16] in which three planar defects are involved: two antiphase boundaries (APBs) on the (100) and (111) planes plus a complex stacking fault (CSF). Several analytical models [17–23] have been proposed to comprehend KWLs and their relation to YSA, considering factors like the difference between the formation energies of the (111)APB and (100)APB [17], and torque interactions between the superpartials [18]. The ‘‘APB-jump’’ phenomenon observed i

FAQs

What causes the yield stress anomaly in L12 intermetallics like Ni3Al?

It is controlled by the Kear–Wilsdorf lock (KWL), whose formation and unlocking are governed by dislocation cross-slip.

How does the study model dislocation behavior at the atomistic level?

It uses molecular dynamics simulations with a dedicated machine-learning interatomic potential derived via physically informed active learning, enabling near ab initio accuracy.

What key finding challenges existing analytical assumptions about KWL unlocking?

The unlocking stress shows a pronounced temperature dependence, contradicting the athermal unlocking assumption in existing models.

Aug 5, 2026

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