Potential Function-Based Molecular Dynamics Simulation of Al-Cu-Li Alloys and Comparison with Experiments

Area of Science:

• Materials Science
• Metallurgy
• Computational Materials Science

Background:

• Aluminum-copper-lithium (Al-Cu-Li) alloys are vital in aerospace due to their high specific strength and low weight.
• The three-stage creep aging (CA) process is key for balancing formability and performance in these alloys.
• Understanding atomic-scale microstructural evolution during complex heat treatments is crucial but under-researched.

Purpose of the Study:

• To investigate the microstructural evolution of Al-Cu-Li alloys during multi-stage low-high-low temperature CA.
• To explore the relationship between microstructure and performance at the atomic scale using molecular dynamics (MD) simulations.
• To validate MD simulation reliability through comparison with experimental findings.

Main Methods:

• Multi-stage low-high-low temperature creep aging (CA) experiments.
• Molecular dynamics (MD) simulations utilizing a neuroevolutionary machine learning potential (NEP) function.
• Analysis of atomic segregation, precipitation phase enrichment, and material performance.

Main Results:

• Lithium atom segregation is unstable at high temperatures, diminishing as the second-stage aging temperature increases.
• Low-temperature aging in the third stage promotes atomic segregation and property recovery, albeit with limitations.
• High-temperature aging in the second stage negatively impacts material performance, while third-stage low-temperature aging aids recovery.
• Experimental precipitation phase enrichment correlates with simulation findings on atomic segregation and temperature effects.

Conclusions:

• MD simulations accurately predict microstructural evolution in Al-Cu-Li alloys under complex CA conditions.
• The study provides insights into optimizing CA processes for enhanced Al-Cu-Li alloy performance.
• Findings offer a valuable reference for microstructural design and performance enhancement in aerospace materials.