Evolution of dislocations during the rapid solidification in additive manufacturing.

Area of Science:

• Materials Science
• Metallurgy
• Manufacturing Engineering

Background:

• Fusion-based additive manufacturing (AM) materials exhibit high dislocation densities and cellular structures, impacting performance.
• Current post-mortem analyses of AM materials limit understanding of dynamic dislocation evolution during manufacturing.
• This gap hinders advancements in AM techniques and product qualification.

Purpose of the Study:

• To investigate the dynamic evolution of dislocation density during wire-laser directed energy deposition of 316L stainless steel.
• To provide mechanism-based insights into dislocation generation and evolution under rapid cooling and thermal cycling.
• To enhance guidance for improving AM processes and certifying AM products.

Main Methods:

• Operando high-energy synchrotron X-ray diffraction experiments were performed.
• A unique experimental configuration enabled semi-quantitative probing of dislocation density.
• Integration with multi-physics simulation, in-situ neutron diffraction, and multi-scale electron microscopy was employed.

Main Results:

• Operando synchrotron experiments successfully tracked dislocation density changes during solidification and cooling.
• The study revealed dynamic dislocation evolution influenced by rapid cooling and thermal cycling.
• A comprehensive mechanistic understanding of dislocation behavior in AM 316L stainless steel was achieved.

Conclusions:

• Operando synchrotron X-ray diffraction is a powerful tool for studying dynamic microstructural evolution in AM.
• Understanding dislocation dynamics is crucial for optimizing AM processes and material properties.
• This research provides foundational data for the qualification and certification of additive manufactured components.