Effect of grain boundary character on segregation-induced structural transitions

TL;DR

This study uses atomistic simulations to explore how grain boundary character influences segregation and structural transitions in Cu-Zr alloys, revealing that boundary type and solute excess determine complexion behavior.

Contribution

It provides new insights into how grain boundary character affects segregation patterns and complexion transitions, emphasizing the role of solute excess over energy or misorientation.

Findings

Disordered complexions form at critical compositions depending on temperature.

High solute excess boundaries undergo gradual disordering, low excess boundaries transition abruptly.

Grain boundary character significantly influences segregation and structural transitions.

Abstract

Segregation-induced structural transitions in metallic grain boundaries are studied with hybrid atomistic Monte Carlo/molecular dynamics simulations using Cu-Zr as a model system, with a specific emphasis on understanding the effect of grain boundary character. With increasing global composition, the six grain boundary types chosen for this study first form ordered complexions, with the local segregation pattern depending on the grain boundary core structure, then transform into disordered complexions when the grain boundary composition reaches a critical value that is temperature dependent. The tendency for this transition to a disordered interfacial structure consistently depends on the relative solute excess, instead of the grain boundary energy or misorientation angle. Grain boundaries with high relative solute excess go through gradual disordering transitions, whereas those with low relative solute excess remain ordered until high global Zr concentrations but then abruptly transform into thick disordered films. The results presented here provide a clear picture of the effect of interface character on both dopant segregation patterns and disordered intergranular film formation, showing that all grain boundaries are not equal when discussing complexion transitions.