Team discovers method for guiding how atoms settle as metal solidifies, giving direct property control at the atomic scale
Researchers at Lawrence Livermore National Laboratory (LLNL) have developed a method to control the atomic-scale structure of metals during additive manufacturing by varying the speed of laser scanning.
The team at LLNL worked with academic collaborators to tackle a longstanding limitation in metal 3D printing, which results in far-from-equilibrium microstructures causing unpredictable mechanical properties.
AM had already advanced aerospace, defense, and energy applications significantly, but it relied on a limited number of pre-existing metallic alloys, ones that were not originally designed for the rapid heating and cooling cycles that come with laser-based 3D printing.
The team focused on compositionally complex materials – known as high-entropy alloys – a promising class of metal materials, and combined thermodynamic modeling and molecular dynamics to simulate their 3D printing. This allowed them to study how different laser scan speeds affected solidification during the printing process, and by modeling the rapid cooling process, the team evaluated how atoms arranged themselves under different thermal conditions.
“By increasing the laser speed, the cooling rate increases, and as the material cools down faster, it has less time to rearrange to a low energy configuration,” stated Thomas Voisin, Deputy Group Lead at Lawrence Livermore National Laboratory. “This freezes the material in a non-equilibrium state, which can be used to tune atomic structures and resulting mechanical properties.”
Their results suggested that rapid cooling produced alloys that were stronger but more brittle, while slower cooling led to structures that were less strong but more flexible and balanced.
“We are now at a place where we can effectively design new materials that take full advantage of the additive manufacturing features like the very rapid cooling rate,” Voisin added.
The work suggested that additive manufacturing could evolve from a production technique into a materials discovery platform. By linking process parameters to atomic-scale outcomes, researchers could design metals tailored for specific operational requirements in aerospace, national security, and commercial industrial systems.
