LLNL links laser scan speed to atomic-scale control in High-Entropy Alloys
In a new study published in Advanced Materials, researchers from Lawrence Livermore National Laboratory (LLNL) and collaborators from several universities have demonstrated a method to guide the settling of atoms as a metal solidifies during Additive Manufacturing.
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By adjusting the laser speed in a High-Entropy Alloy (HEA), the team reportedly controlled the material’s properties directly at the atomic scale.
In ‘Unravelling Microstructure Selection in an Additively Manufactured Eutectic High-Entropy Alloy’, the researchers combined thermodynamic modelling and molecular dynamics to simulate the Additive Manufacturing of HEAs in order to determine how the cooling rate impacts the internal structures.
“By increasing the laser speed, the cooling rate increases and, as the material cools down faster, it has less time to rearrange into a low energy configuration,” explained Thomas Voisin, Deputy Group Lead. “This freezes the material in a non-equilibrium state, which can be used to tune atomic structures and resulting mechanical properties.”
Fast cooling yields a very strong but more brittle alloy; slower cooling yields more flexible, balanced structures. By adjusting the laser speed, the researchers were able to create this range of properties in the single HEA material investigated.
“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,” added Voisin.
The researchers have stated that this development could enable the use of Additive Manufacturing as a platform for producing metals with specially engineered properties.
The paper is available here.
