Atomistic insight into Al-Mg friction stir welding process via molecular dynamics simulation

Area of Science:

• Materials Science
• Computational Materials Science
• Mechanical Engineering

Background:

• Friction stir welding (FSW) is a solid-state joining process known for producing high-quality welds with unique microstructures.
• Molecular dynamics (MD) simulations are increasingly used to investigate FSW at the atomic level, but the influence of tool geometry is often overlooked.

Purpose of the Study:

• To investigate the dissimilar welding of Mg-Al joints using MD simulations.
• To examine the effects of tool travel speed, rotation speed, and tool pin geometry on Mg-Al weld formation.

Main Methods:

• Dissimilar welding of Mg-Al was simulated using molecular dynamics.
• Parameters varied included tool travel speed (500-2000 m/s), rotation speed (12 rad/ps), and tool pin geometries (rectangular prism, cone, triangular, tube).
• Atomic strain distribution, temperature zones, and amorphous fraction were analyzed.

Main Results:

• Aluminum atoms exhibited greater mixing into the magnesium plate compared to magnesium atoms in the aluminum plate.
• Increased travel speed led to higher atomic strain, temperatures up to 1000 K, and an 18.8% amorphous fraction.
• Higher rotation speeds amplified plastic deformation and high-temperature zones, with peak atomic mixing at 12 rad/ps.
• Rectangular prism and cone tool geometries resulted in higher heating, while triangular and tube geometries improved stirring.

Conclusions:

• Tool pin geometry and process parameters critically affect atomic mixing and microstructure evolution in Mg-Al FSW joints.
• MD simulations provide valuable atomic-level insights into the mechanics of FSW.
• Future research should explore the impact of offset distance and tool angle on material flow.