Atomistic-continuum hybrid analysis of dislocation behavior in spinodally decomposed Fe-Cr alloys

Akiyuki Takahashi,Motoyasu Kanazawa

doi:10.1051/matecconf/201710101018

Akiyuki Takahashi, Motoyasu Kanazawa

Open Access

https://doi.org/10.1051/matecconf/201710101018

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Abstract

In this study, we first present the molecular dynamics (MD) simulation of dislocation behavior in a spinodally decomposed Fe-Cr alloy. The MD simulation is used for exploring the nature of the interaction between a dislocation and the spinodal decomposition without any specific assumptions. In order to classify the interaction mechanism, dislocation dynamics (DD) simulations of the interaction between a dislocation and the spinodal decomposition are performed. In the simulations, we controlled the interaction mechanism by adding and removing the atomistic mechanism. The simulation results clearly illustrate that the atomistic mechanism can be negligible in determining the critical resolved shear stress (CRSS) of spinodally decomposed Fe-Cr alloys, and the internal stress generated by the lattice constant mismatch is a dominant mechanism. These findings are very useful for simplifying the analysis of the mechanism of material strength change due to the spinodal decomposition. Particularly in the analysis using the DD simulations, the required computational effort for simulating the dislocation behavior is greatly reduced by taking into account only the internal stress without the atomistic dislocation core influence.

Highlights

Duplex stainless steels consisting of ferrite and austenite phases have a high material strength, the corrosion resistance, and are used as a material of primary coolant pipes in nuclear power plants
The information obtained by the studies is variable in clarifying the dislocation behavior in the internal stress field, and due to the complexity and limitation of the theoretical approach to the problem, the information is limited for dislocations with a simple shape, even though the dislocation shape must be changed a lot by the interaction with the internal stress field
Because the molecular dynamics (MD) simulation is based on the interatomic potential, the MD simulations can account for all the mechanism given by the spinodal decomposition, such as elastic interaction and atomistic dislocation core influence

Summary

Introduction

Duplex stainless steels consisting of ferrite and austenite phases have a high material strength, the corrosion resistance, and are used as a material of primary coolant pipes in nuclear power plants. In order to investigate the material strength degeneration mechanism, an equation for the internal stress distribution arisen from the phase separation has been derived [1]. Takahashi and Ghoniem have developed a dislocation dynamics-based computational method for dislocationprecipitate interaction problems, and investigated the interaction of dislocations with precipitates in terms of elasticity [6]. They developed a hybrid atomistic-continuum method for investigation of dislocation cores [7,8]. The type of simulation method could be a powerful tool for investigating the material strength degeneration mechanism due to the spinodal decomposition involving both the continuum and atomistic mechanisms. We discuss the importance of the continuum and atomistic mechanism on the material strength change due to the spinodal decomposition

Molecular dynamics method

Dislocation dynamics method

Molecular dynamics simulation results

Dislocation dynamics simulation results

Findings

Conclusions