Revealing the Epitaxial Interface between Al₁₃Fe₄ and Al₅Fe₂ Enabling Atomic Al Interdiffusion

Area of Science:

• Materials Science
• Surface Science
• Computational Materials Science

Background:

• Steel is a widely manufactured material, with properties enhanced by aluminum hot-dip coating.
• The aluminum-iron (Al∥Fe) interface contains intermetallic compounds (Al5Fe2, Al13Fe4) critical for performance.
• Understanding the atomic structure of this interface is key to optimizing coated steel.

Purpose of the Study:

• To develop a consistent atomic-scale model of the Al13Fe4(010)∥Al5Fe2(001) interface.
• To identify factors governing the stability of the Al∥Fe interface.
• To elucidate the formation mechanism of intermetallic phases at the Al∥Fe interface.

Main Methods:

• Surface X-ray diffraction.
• Theoretical calculations using density functional theory (DFT).
• Molecular dynamics (MD) simulations.

Main Results:

• A consistent atomic-scale model for the Al13Fe4(010)∥Al5Fe2(001) interface was established.
• Epitaxial relationships were determined: [130]Al∥[010]Al and [11̅0]Al∥[100]Al.
• Lattice mismatch and interfacial composition were identified as primary drivers of interface stability.
• Aluminum diffusion was proposed as the mechanism for forming Al13Fe4 and Al5Fe2 phases.

Conclusions:

• The study provides a detailed atomic-level understanding of the Al∥Fe interface structure and stability.
• Lattice mismatch and chemical composition are critical parameters for interface engineering.
• Aluminum diffusion plays a significant role in the formation of protective intermetallic layers during hot-dip coating.