Theory of history-dependent multi-layer generalized stacking fault energy- A modeling of the micro-substructure evolution kinetics in chemically ordered medium-entropy alloys

In this study, a chemical order related concept history-dependent multi-layer generalized stacking fault energy (HDML-GSFE) was proposed, and it was then demonstrated by employing the recent, very interesting multi-principal element alloy (CoCrNi medium-entropy alloys; MEA) with different chemical short-range order (CSRO) levels using a density functional theory (DFT)-based neural network interatomic potential. To demonstrate the impacts of the history dependency and interlayer (atomic interlayers of the slip system) coupling effect on the GSFE of CSRO MEAs, HDML-GSFEs were computed for different shear deformation pathways of the MEAs with different CSRO levels, such as interlayer multiple-time slipping, twin growth, and gamma - epsilon (FCC-HCP) phase transformation. It was demonstrated that multiple-time slipping induces CSRO collapse, leading to local shear softening due to the history dependency of GSFE. In addition, it was found that the slipping of neighboring atomic interlayers is affected by the slipping resulting from the induced CSRO collapse of present interlayers because of the interlayer coupling effect of GSFE. Eventually, by employing a novel kinetic Monte Carlo (kMC) simulation method based on dislocation/disconnection loop nucleation events and using the HDML-GSFE with the history dependency and interlayer coupling effect, we proposed a laminated micro-substructure evolution that involves twinning and gamma - epsilon phase transformations subject to a finite shear strain rate and finite temperature. (C) 2021 The Authors. Published by Elsevier Ltd on behalf of Acta Materialia Inc.& nbsp;

Automated summary

This study proposes a chemical order related concept of history-dependent multi-layer generalized stacking fault energy and validates it using a neural network interatomic potential. The impacts of history dependence and interlayer coupling effect on the alloy structure are demonstrated by computing the fault energy for different shear deformation pathways.