In a recent study, scientists at U.S. federal research laboratory Lawrence Livermore National Laboratory (LLNL) demonstrated that metal properties in additive manufacturing can be deliberately adjusted during fabrication. By modifying laser scan speed while printing high-entropy alloys, the team showed how cooling rates influence atomic structure as the metal solidifies. The findings indicate that material behavior can be shaped directly through process parameters rather than post-processing or alloy redesign.
The findings directly address a primary barrier to the broader adoption of metal additive manufacturing for certified, end-use applications: uncertainty in material performance.
Metal Additive Manufacturing Struggles With Predictability
While metal additive manufacturing allows the production of complex geometries for aerospace and defense components, its adoption in performance-critical applications remains limited by unpredictable material behavior. Rapid melting and solidification during printing create non-equilibrium microstructures, resulting in significant variation in strength, ductility, and fracture resistance—even under identical nominal process settings.
LLNL noted that high-entropy alloys, which contain multiple principal elements rather than a single base metal, offer a broader design space than traditional alloys. Their complex chemistry allows for a wide range of mechanical responses but also makes them highly sensitive to thermal history during printing. As a result, small differences in cooling rate can substantially alter atomic arrangements and final properties, further reinforcing the challenge of predictability.
Using Laser Speed to Program Atomic Structure
To examine how process parameters influence material behavior, the LLNL-led team combined thermodynamic modeling with molecular dynamics simulations of metal additive manufacturing. The researchers analyzed how laser scan speed affects cooling rates during solidification and, in turn, how atoms arrange themselves within a compositionally complex alloy.
The results showed that faster laser scan speeds increase cooling rates, limiting the time available for atoms to rearrange into low-energy configurations. This locks the material into a non-equilibrium atomic structure. Slower scan speeds allow more atomic reordering, producing structures closer to thermodynamic equilibrium.
This process-level control allows a direct tradeoff between strength and ductility within the same alloy system. Rapid cooling produces higher strength but increased brittleness, while slower cooling yields more balanced mechanical behavior. Rather than changing alloy composition, the approach allows performance to be adjusted by modifying a single printing parameter.
“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 Deputy Group Lead Thomas Voisin.
While the LLNL study demonstrates that atomic structure in metal additive manufacturing can be influenced in-process through control of laser scan speed, the findings are based on thermodynamic modeling and molecular dynamics simulations of high-entropy alloys and have not yet been validated in certified, production-scale parts. Nevertheless, the work suggests that process parameters could be used as deliberate design levers to influence material behavior, rather than treating microstructural variability as an unavoidable outcome.
Why Tunable Properties Matter in Practice
The ability to adjust mechanical properties during metal additive manufacturing addresses a fundamental constraint facing the field: uncertainty in end-use performance. In sectors such as aerospace, defense, and energy, engineers cannot design or certify parts based on a broad range of possible material outcomes. Mechanical properties must be known in advance to meet qualification, safety, and reliability requirements. However, conventional metal AM processes often produce variable microstructures because small differences in heat flow can lead to large differences in atomic structure.
Recent research reflects growing efforts to reduce this uncertainty. Studies have shown how cooling rate in laser powder bed fusion affects grain structure, toughness, and corrosion resistance, while other teams have developed tools to predict and influence microstructure in nickel-based superalloys by adjusting laser power and scan strategy. These approaches aim to align printed material behavior with design intent, but often require extensive parameter optimization or alloy-specific tuning.
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Featured image shows Artist rendering of LLNL’s new additively manufactured high-entropy alloys. Image via LNLL.
