ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2025 8 METALS | POLYMERS | CERAMICS large-scale, 3D-printed polymer parts. Large-format additive manufacturing (LFAM) enables direct printing of meter-scale structures for aerospace, automotive, and defense tooling applications. However, widespread adoption has been limited by voids that weaken printed parts. Reducing porosity is key to improving strength, durability, and overall performance. ORNL researchers addressed this challenge with a unique approach: The team integrated a vacuum hopper during the extrusion process to remove trapped gases and minimize void formation in fiber-reinforced materials. These materials are widely used in LFAM for their stiffness and low thermal expansion but often suffer from intrabead porosity that limits part quality. The new system reduced porosity to less than 2%, even with varying fiber content. “Using this innovative technique, we are not only addressing the critical issue of porosity in large-scale polymer prints but also paving the way for stronger composites,” says researcher Vipin Kumar. “This is a significant leap forward for the LFAM industry.” Although the current method is designed for batch processing, ORNL developed a patent-pending concept for continuous deposition systems, which will be the focus of future research. ornl.gov. NEW ALLOY DESIGN ENHANCES ALUMINUM Researchers from the Max Planck Institute for Sustainable Materials in Germany, along with partners in Japan and China, developed a new alloy design technique that overcomes the challenge of embrittlement, which leads to cracking and failure when aluminum alloys are exposed to hydrogen. Key to this breakthrough is a size-sieved precipitation strategy in scandium-added aluminum-magnesium alloys. By using a two-step heat treatment, the researchers engineered fine Al3Sc nanoprecipitates on which a shell of a highly structurally complex Al3(Mg,Sc)2 forms in situ. These dual nanoprecipitates are distributed throughout the alloy to serve two key purposes. The Al3(Mg,Sc)2 phase traps hydrogen and increases resistance against hydrogen embrittlement, while the fine Al3Sc particles boost strength. “Our new design strategy solves this typical trade-off. We no longer have to choose between high strength and hydrogen resistance—this alloy delivers both,” says researcher Baptiste Gault. The results show a 40% increase in strength and a five-fold improvement in hydrogen embrittlement resistance compared to scandium-free alloys. The material also achieves a record uniform tensile elongation in hydrogen-charged aluminum alloys at relatively high hydrogen loading. Atom probe tomography measurements carried out at the Max Planck Institute were essential in verifying the role of the Al3(Mg,Sc)2 phase in hydrogen trapping at the atomic level, offering insights into how the alloy design works on a fundamental scale. The researchers tested their approach across various Al alloy systems and demonstrated scalability by using water-cooled copper mold casting and thermomechanical processing methods. www.mpg.de. VACUUM-ASSISTED EXTRUSION FOR POLYMER PRINTS Researchers at the DOE’s Oak Ridge National Laboratory (ORNL), Tenn., developed a vacuum-assisted extrusion method that reduces internal porosity by up to 75% in Emirates Global Aluminum chose Oklahoma as the site for the first new primary aluminum production plant to be built in the U.S. in 45 years. The $4 billion project will create 1000 direct jobs and 1800 indirect jobs. The facility will produce billets, sheet ingots, high-purity aluminum, and foundry alloys. www.ega.ae. BRIEF Complex nanoprecipitates can trap hydrogen inside aluminum alloys while maintaining their strength. Courtesy of Nature, 2025, doi.org/10.1038/S41586025-08879-2. A vacuum-assisted extrusion is used in large-scale additive manufacturing to reduce porosity in printed parts. Courtesy of Vipin Kumar/ORNL, U.S. Dept. of Energy.
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