Dislocation-mediated short-range order evolution during thermomechanical processing

TL;DR

This study uses large-scale atomistic simulations to explore how temperature and strain rate influence dislocation-driven short-range order evolution in alloys during thermomechanical processing, revealing non-equilibrium steady states.

Contribution

It provides a mechanistic, predictive understanding of how processing parameters control dislocation-mediated SRO evolution in complex alloys using advanced simulations and information-theoretic metrics.

Findings

SRO varies systematically with temperature and strain rate.

Two regimes identified: low-temperature weak sensitivity, high-temperature enhanced SRO formation.

Steady-state SRO is far-from-equilibrium, not achievable by thermal annealing.

Abstract

Thermomechanical processing alters the microstructure of metallic alloys through coupled plastic deformation and thermal exposure, with dislocation motion driving plasticity and microstructural evolution. Our previous work (Islam et al., 2025) showed that the same dislocation motion both creates and destroys chemical short-range order (SRO), driving alloys into far-from-equilibrium SRO states. However, the connection between this dislocation-mediated SRO evolution and processing parameters remains largely unexplored. Here, we perform large-scale atomistic simulations of thermomechanical processing of equiatomic TiTaVW to determine how temperature and strain rate control SRO via competing creation ($\Gamma$) and annihilation ($\lambda$) rates. The simulations employ systems containing 2.4 million atoms and utilize a machine learning interatomic potential optimized to capture chemical complexity through the motif-based sampling technique. Using information-theoretic metrics, we quantify that the magnitude and chemical character of SRO vary systematically with processing parameters. We identify two regimes: a low-temperature regime with weak strain-rate sensitivity, and a high-temperature regime in which reduced dislocation density and increased screw character amplify chemical bias and accelerate SRO formation. The resulting steady-state SRO is far-from-equilibrium and cannot be produced by equilibrium thermal annealing. Together, these results provide a mechanistic and predictive link between processing parameters, dislocation physics, and SRO evolution in chemically complex alloys.