Prediction of a wide variety of linear complexions in face centered cubic alloys

TL;DR

This study uses atomistic simulations to predict various stable linear complexion states at dislocations in face centered cubic alloys, expanding understanding of defect structures and their impact on material properties.

Contribution

The paper introduces a systematic approach to identify and classify new linear complexion states in FCC alloys, including the construction of complexion diagrams and prediction of novel defect structures.

Findings

Identified stable nanoscale complexion states near dislocations in FCC alloys.

Predicted new complexion types such as nanoparticle arrays and layered intermetallic phases.

Constructed complexion diagrams to guide alloy design and defect engineering.

Abstract

Linear complexions are defect states that have been recently discovered along dislocations in body centered cubic Fe-based alloys. In this work, we use atomistic simulations to extend this concept and explore segregation-driven structural transitions at dislocations in face centered cubic alloys. We identify a variety of stable, nanoscale-size structural and chemical states, which are confined near dislocations and can be classified as linear complexions. Depending on the alloy system and thermodynamic conditions, such new states can preserve, partially modify, or completely replace the original defects they were born at. By considering different temperatures and compositions, we construct linear complexion diagrams that are similar to bulk phase diagrams, defining the important conditions for complexion formation while also specifying an expected complexion size and type. Several notable new complexion types were predicted here: (1) nanoparticle arrays comprised of L12 phases in Ni-Fe, Ni-Al, and Al-Zr, (2) replacement of stacking faults with layered complexions comprised of (111) planes from the Cu5Zr intermetallic phase in Cu-Zr, (3) platelet arrays comprised of two-dimensional Guinier-Preston zones in Al-Cu, and finally (4) coexistence of multiple linear complexions containing both Guinier-Preston zones and L12 phases in ternary Al-Cu-Zr. All of these new complexion states are expected to alter material properties and affect the stability of the dislocations themselves, offering a unique opportunity for future materials design.