Size-Dependent Solute Segregation at Symmetric Tilt Grain Boundaries in α-Fe: A Quasiparticle Approach Study

Area of Science:

• Materials Science
• Computational Materials Science
• Physical Metallurgy

Background:

• Grain boundaries (GBs) in metals significantly impact material properties.
• Solute segregation at GBs is a critical phenomenon affecting mechanical behavior.
• Understanding solute-GB interactions requires atomistic-level insights.

Purpose of the Study:

• To investigate the general trends of solute segregation at symmetric ⟨100⟩ tilt grain boundaries (GBs) in alpha-iron (α-Fe).
• To elucidate the role of solute atomic size and local hydrostatic stress in segregation behavior.
• To develop and apply a quasiparticle approach (QA) for predicting solute atom positions.

Main Methods:

• Atomistic modeling using the quasiparticle approach (QA).
• Simulation of three solute types (X1, X2, X3) with varying atomic radii (smaller, similar, larger than Fe).
• Analysis of solute segregation at low and high angle GBs (Σ5, Σ29).

Main Results:

• Segregation is primarily governed by atomic size and local hydrostatic stress.
• Smaller solutes (X1) segregate at compressed/dilated area interfaces in low-angle GBs.
• Larger solutes (X2, X3) form Fe9X clusters in high-angle GBs, with depleted zones nearby.
• Specific structural units (SUs) in Σ29 GBs show preferential solute absorption based on size.

Conclusions:

• The developed QA methodology accurately predicts solute atom positions at and near GBs.
• Solute atomic size is a dominant factor controlling segregation behavior and cluster formation.
• Local stress fields and GB structure dictate the precise locations and concentrations of segregated solutes.