Atomistic Assessment of Solute-Solute Interactions during Grain Boundary Segregation.

Christopher A. Schuh,Thomas P. Matson

doi:10.3390/nano11092360

Christopher A. Schuh, Thomas P. Matson

Open Access

https://doi.org/10.3390/nano11092360

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Abstract

Grain boundary solute segregation is becoming increasingly common as a means of stabilizing nanocrystalline alloys. Thermodynamic models for grain boundary segregation have recently revealed the need for spectral information, i.e., the full distribution of environments available at the grain boundary during segregation, in order to capture the essential physics of the problem for complex systems like nanocrystalline materials. However, there has been only one proposed method of extending spectral segregation models beyond the dilute limit, and it is based on simple, fitted parameters that are not atomistically informed. In this work, we present a physically motived atomistic method to measure the full distribution of solute-solute interaction energies at the grain boundaries in a polycrystalline environment. We then cast the results into a simple thermodynamic model, analyze the Al(Mg) system as a case study, and demonstrate strong agreement with physically rigorous hybrid Monte Carlo/molecular statics simulations. This approach provides a means of rapidly measuring key interactions for non-dilute grain boundary segregation for any system with an interatomic potential.

Highlights

Nanocrystalline metals exhibit a wide range of useful properties that often exceed what is achievable at the microscale [1,2,3,4,5,6,7,8,9,10]. They are often in unstable, nonequilibrium states due to a high concentration of grain boundaries (GBs) that contribute to the free energy of the system and create an increasingly large driving force for grain growth at the nanoscale [11,12,13,14]
Alloying can provide a means of thermodynamically stabilizing the nanocrystalline state by lowering the grain boundary energy via grain boundary solute segregation [11,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]
A major shortcoming of most all such models is their use of a single segregation energy to characterize the entire grain boundary network, which in reality has a complex diversity of segregation sites

Summary

Introduction

Nanocrystalline metals exhibit a wide range of useful properties that often exceed what is achievable at the microscale [1,2,3,4,5,6,7,8,9,10]. Alloying can provide a means of thermodynamically stabilizing the nanocrystalline state by lowering the grain boundary energy via grain boundary solute segregation [11,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30] This thermodynamic approach has been gaining increased attention in recent years compared to kinetic methods of stabilization [31,32,33,34,35,36], due to its reliability and relatively simple design space, which requires only thermodynamic knowledge of the alloy system.

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Conclusion