Next-generation technology requires next-generation materials that can be tailored to exact mission requirements. Additive manufacturing, or 3D printing, has already revolutionized industries like aerospace engineering by enabling previously unthinkable component designs. However, this technique has been largely limited to pre-existing metallic alloys. This is due to the inherent complexity of the process that leads to far-from-equilibrium microstructures and results in mechanical properties that are hard to predict.
In a new study, scientists at Lawrence Livermore National Laboratory and their collaborators demonstrate a method to overcome the challenges of the traditional additive manufacturing process. By adjusting the speed of the laser in a compositionally complex alloy (also called high-entropy alloy), the team discovered a method to guide how the atoms settle as the metal solidifies, controlling the material's properties directly at the atomic scale.
The team combined thermodynamic modeling and molecular dynamics to simulate the 3D printing of high-entropy alloys, a promising class of metal materials, to determine how the cooling rate impacts the internal structures. Their finding revealed that the speed of the laser scan could control for how the atoms lock into place.
"By increasing the laser speed, the cooling rate increases," explained Deputy Group Lead Thomas Voisin, "and as the material cools down faster, it has less time to rearrange to a low energy configuration. This freezes the material in a non-equilibrium state, which can be used to tune atomic structures and resulting mechanical properties."
Fast cooling makes the alloy very strong but more brittle, while slower cooling allows more flexible, balanced structures to form. This allows the researchers to harness the unique versatility of high-entropy alloys, tailoring their properties to meet specific needs.
It's like tuning between a rigid ceramic tile and a bendable paperclip: one resists force but breaks suddenly, the other yields and flexes. By simply adjusting laser speed with this specific metallic alloy, the researchers created this entire spectrum of properties within a single material.
The result is a breakthrough in how metal materials can be designed. Instead of relying on trial-and-error recipes, additive manufacturing could become a platform for engineering metals with properties programmed into them.
"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," said Voisin.
This approach points to a new era of materials science, one in which additive manufacturing is not just a production tool but an engine for discoveries in national security and commercial industries.
