Project
Segregation at interfaces in lightweight alloys towards tailored mechanical properties
The growing emphasis on energy conservation and environmental sustainability has driven strong interest in developing cost-effective materials for lightweight structural components. Magnesium alloys present a highly promising candidate for these applications due to their low density. However, their limited room-temperature ductility restricts broader industrial adoption. Tailoring their mechanical properties requires a deep understanding of the fundamental deformation mechanisms operating at the atomic scale.
To complement physical experiments, atomistic simulations provide invaluable insights into these fine-scale phenomena. Tracking atomic interactions across diverse material behaviors, such as dislocation mobility, grain boundary migration, solute segregation, and interface-driven plasticity, which requires calculating the physical forces among millions of individual atoms over millions of time steps. High Performance Computing (HPC) is therefore crucial for this research. By leveraging parallel processing across multiple supercomputer nodes, HPC enables large-scale modeling that captures these complex atomic processes, directly bridging computational predictions with experimental observations.
Project Details
Project term
July 23, 2025–July 22, 2026
Affiliations
RWTH Aachen University
Institute
Institute for Physical Metallurgy and Materials Physics
Principal Investigator
Methods
The atomistic simulations were conducted using the open-source code Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). Various classical interatomic potentials for the magnesium system were first benchmarked by evaluating fundamental bulk properties, such as lattice constants and elastic moduli, against experimental data and first-principles calculations.
Following the initial construction of grain boundary structures, molecular statics simulations were employed to scan the structural degrees of freedom, identify stable interface configurations, and calculate per-site atomic segregation energies near the boundary. Distinct types of dislocations were subsequently introduced to investigate dislocation-boundary interactions under quasi-static loading.
To complement experimental micropillar compression testing, large-scale molecular dynamics simulations were applied using single-crystalline and bicrystalline nanopillars constructed with aspect ratios identical to experiments. To isolate twinning deformation mechanisms, tailored structural models were built to decouple the twinning process into distinct stages: twin nucleation, propagation, and thickening. Uniaxial compression was then simulated using virtual indenters while maintaining constant temperature at 10 K.
Results
The project progressed across three phases, with major findings detailed below. Additional exploratory simulations performed using the allocated computing time are documented in the project’s published articles and student theses.
Phase 1 (January 2023 – January 2024): Potential Benchmarking
The initial phase systematically evaluated classical interatomic potentials for magnesium by calculating fundamental bulk properties, grain boundary energies, and dislocation characteristics. This work established a rigorous computational foundation for subsequent large-scale modeling, culminating in a published study titled “Defects in Magnesium and Its Alloys by Atomistic Simulation: Assessment of Semi-Empirical Potentials.”
Phase 2 (March 2024 – May 2025): Interfacial Energetics and Solute Segregation
The second phase systematically investigated grain boundary structures, solute segregation, and interfacial phase formation in magnesium-based alloys. Molecular statics simulations mapped symmetric tilt grain boundaries across 50+ configurations, identifying distinct structural energy minima and evaluating zinc and yttrium segregation behaviors. This work demonstrated that conventional boundary characterization algorithms underestimate the physical extent of the segregation zone, directly affecting thermodynamic solute concentration predictions. Furthermore, hybrid molecular dynamics and Monte Carlo simulations explored segregation in textured magnesium-aluminum alloys. The calculations unveiled a unique bimodal segregation energy distribution and captured the temperature- and composition-dependent nucleation of aluminum-rich intermetallic phases at grain boundaries, offering key insights for alloy microstructure design.
Phase 3 (May 2025 – Present): Large-Scale Nanopillar Compression
Large-scale molecular dynamics simulations successfully reproduced the experimental deformation behavior of single-crystal and bicrystal micropillars under a-axis compression. In single-crystal pillars, the simulations revealed that deformation twinning operates through three distinct stages governed by a descending stress hierarchy: nucleation, propagation, and thickening. Twin nucleation and propagation occur in a high-stress regime driven by shuffle-assisted atomic rearrangements, whereas lateral thickening proceeds in a low-stress regime dominated by disconnection motion. This thickening process is approximately one order of magnitude slower than nucleation and propagation. In bicrystal pillars, a pre-existing twin boundary has limited influence on the onset of plasticity but strongly governs subsequent plastic events through twin-twin boundary interactions and the inhibition of further dislocation transmission.
Discussion
Supported by the High Performance Computing system, the simulation outcomes across all three project phases successfully bridge the gap between atomic-scale deformation mechanisms and macro-level experimental observations. This project clearly elucidated how interface structures, solute segregation, and localized defects alter deformation pathways, thereby governing the overall plasticity of magnesium and its alloys. Executing these computationally intensive tasks, such as mapping dozens of boundary configurations and tracking millions of dynamic atoms, demanded substantial supercomputing capacity. Ultimately, these atomistic simulations provide crucial insights into the structure, energetics, and dynamics of crystallographic defects, paving the way for targeted defect engineering in light alloys.
Building upon this established framework, future work will extend these findings in three key directions: first, benchmarking protocols will be expanded to evaluate machine-learning-based interatomic potentials for large-scale simulations with near-quantum accuracy; second, the constructed grain boundary configurations will serve as initial structures to systematically investigate grain boundary migration dynamics; and third, expanded molecular dynamics simulations will be performed to capture time-dependent kinetic properties, such as long-range solute diffusion.
Additional Project Information
DFG classification: 406-03 Microstructural Mechanical Properties of Materials
Software: LAMMPS
Cluster: CLAIX
Publications
Defects in magnesium and its alloys by atomistic simulation: Assessment of semi-empirical potential,
Hexin Wang, Julien Guénolé, Sandra Korte-Kerzel, Talal Al-Samman, Zhuocheng Xie,
https://dx.doi.org/10.1016/j.commatsci.2024.113025, May 2024
Influence of chemical composition on the room temperature plasticity of C15 Ca-Al-Mg Laves phases,
Martina Freund, Zhuocheng Xie, Pei-Ling Sun, Lukas Berners, Joshua Spille, Hexin Wang, Carsten Thomas, Michael Feuerbacher, Marta Lipinska-Chwalek, Joachim Mayer, Sandra Korte-Kerzel,
https://dx.doi.org/10.1016/j.actamat.2024.120124, September 2024
Beyond Fundamental Building Blocks: Plasticity in Structurally Complex Crystals,
Tobias Stollenwerk, Pia Carlotta Huckfeldt, Nisa Zakia Zahra Ulumuddin, Malik Schneider, Zhuocheng Xie, Sandra Korte-Kerzel,
https://dx.doi.org/10.1002/adma.202414376, December 2024
Grain boundary segregation spectrum in basal-textured Mg alloys: From solute decoration to structural transition,
Anumoy Ganguly, Hexin Wang, Julien Guénolé, Aruna Prakash, Sandra Korte-Kerzel, Talal Al-Samman, Zhuocheng Xie,
https://dx.doi.org/10.1016/j.actamat.2024.120556, January 2025
First-principles insights into the site occupancy of Ta–Fe–Al C14 Laves phases,
Nisa Ulumuddin, Sandra Korte-Kerzel, Zhuocheng Xie,
https://dx.doi.org/10.1016/j.commatsci.2025.113856, May 2025
Thesis:
Investigation of [11-20] symmetric tilt grain boundary properties in magnesium and its alloys using atomisitc simulations,
D. Mahendran,
Master thesis, January 2025
Atomistic simulations of dislocation defects interactions in Mg Alloys,
Jingquan Yang,
Master thesis, December 2025