Prediction of Complex Metals' and Alloys’ Response to Temperature and Deformation via Handshake Between Experiments and Modeling

Project Overview

Environmental challenges, energy cost, and difficulty mining metallic elements require next-generation structural materials to be stronger, lighter, and easier to process. Recent progress in metals additive manufacturing (AM) have allowed scientists and engineers to produce near-net shape parts with unprecedented design complexity. This has opened a door to drastically reduce components' weight via design optimization. On the other hand, AM techniques such as laser powder bed fusion (LPBF), where a laser is used to locally melt pre-alloyed metallic powder and build, layer by layer, full parts with high spatial resolution, have a strong effect on material atomic structures and can be used to improve their properties. Simply put, LPBF allows us to reduce a part weight by optimizing its design, or by making the material stronger so less material is needed in the end. However, before LPBF materials can be certified prior to fielding, it is necessary to understand the reasons for properties improvements and be able to predict them with simulations to maintain complete control of future parts behaviors. Using stainless steel, one of the most studied materials for LPBF, we understood the improvement in strength came from specific atomic-scale material self-organization in response to the very rapid and local cooling rates encountered in LPBF. However, the complexity of these novel structures required us to use complex characterization techniques and simulations to understand and predict their response to mechanical deformation. In this project, we have focused on calibrating the experimental measurements that were conducted using high-energy x-ray diffraction techniques at synchrotrons using model metals, and then developed state-of-the-art 3D simulations capable of accounting for local evolution of LPBF stainless steel atomic structures during mechanical loading. Not only are we now understanding stainless steel mechanical properties improvement after LPBF but we are also capable of simulating these properties with process-aware models. This knowledge was then used to develop new LPBF metallic alloys with unprecedented high strength. More generally, this project increased our knowledge of metals deformation behavior and demonstrate how LPBF can be used to develop next generation structural materials that are stronger, lighter, and easier to process.

Mission Impact

This project and its results have enhanced the fundamental understanding of metals deformation mechanisms and our capabilities to predict materials response to external mechanical load. This is directly relevant to the Stockpile Stewardship program. Predictive simulations of additively manufactured materials' mechanical properties are lacking but required so AM parts can be implemented in a controlled fashion into LLNL and more broadly DOE/NNSA program's applications. This research has focused on developing science and technology tools and capabilities to meet future national security challenges.

Publications, Presentations, and Patents

Monchoux, J.-P. et al., 2021. "Elaboration of Metallic Materials by Sps: Processing, Microstructures, Properties, and Shaping." Metals 11, no. 2 (2021): 322. https://www.mdpi.com/2075-4701/11/2/322.

Ren, J. et al., 2022. "Strong yet Ductile Nanolamellar High-Entropy Alloys by Additive Manufacturing." Nature 608, no. 7921 (2022/08/01 2022): 62-68. https://doi.org/10.1038/s41586-022-04914-8.

Voisin, Thomas. "Characterization of Microstructures and Deformation Mechanisms in Additively Manufactured 316L Stainless Steels." Invited seminar at the University of Illinois Urbana-Champaign. Urbana, IL. 2022. LLNL-PRES-840186.

Voisin, Thomas. "Characterization of Microstructures and Deformation Mechanisms in Additively Manufactured 316L Stainless Steels." Invited plenary session talk, 3D Materials Science International Conference. Washington, DC. June 2022. LLNL-PRES-836729.

Voisin, Thomas. "Effect of Rapid-Solidification Structures on the Deformation Behavior and Thermal Stability of an AM 316L Stainless Steel." Spring MRS International Conference in Honolulu, HI. May 2022. LLNL-PRES-834979.

Voisin, Thomas. "Experiment/Simulation Integration Approach to Investigate Microstructure and Plastic Deformation of AM 316L Stainless Steels." Spring MRS International Conference in Honolulu, HI. May 2022. LLNL-PRES-834978.

Voisin, Thomas. "Investigation of the Microstructure and Plastic Deformation of AM 316L Stainless Steels." TMS23 International Conference in Anaheim, CA. Feb. 2022. LLNL-PRES-832177.

Voisin, Thomas. "New Insights on Cellular Structures Strengthening Mechanisms and Thermal Stability of L-PBF Stainless Steel 316L."TMS22 International Conference. Virtual. March 2021. LLNL-PRES-820374.