2024 Investiture Information

All Thayer Events

Jones Seminar: Forging a Sustainable Future with Solid-State Metal Additive Manufacturing

Oct

13

Friday
3:30pm - 4:30pm ET

Spanos Auditorium/Online

Optional ZOOM LINK
Meeting ID: 966 7432 5736
Passcode: 043997

The mainstream fusion-based metal additive manufacturing processes face persistent challenges like porosity, residual stress, hot cracking, and high energy cost because of melting and rapid solidification. In this presentation, I will introduce an emerging solid-state metal additive manufacturing process as a solution: additive friction stir deposition, which enables location-specific printing, cladding, and repair without melting the feedstock. Through in-situ monitoring, tracer flow investigation, and process modeling, this forging-based additive manufacturing process is found to be characterized by rapid and large plastic deformation at elevated temperatures. Substantial material flow occurs under such extreme thermomechanical conditions, leading to fully dense material in the as-printed state with refined, equiaxed grain structures due to dynamic recrystallization.

Without modifying feedstock chemistry, forging-standard mechanical properties have been achieved in aerospace Ti alloys (as-printed) and Al alloys (after proper aging). Regarding niche applications, the extensive material flow during printing allows for rapid conversion of metal scraps into fully dense components, as demonstrated in upcycling of cast Al chips. This process has also shown unmatched capabilities in repairing deep, volumetric damage, such as through-holes in high-performance 7xxx Al structures, while maintaining comparable or even superior post-repair fatigue performance—by delaying crack initiation through dynamic microstructure evolution. Moreover, the compression and shear forces enhance the printing stability, enabling operation under austere conditions, as demonstrated by underwater printing of SS304. Overall, the non-melting nature, full print density, forging-like material performance, and circular economy applications make additive friction stir deposition a promising avenue for advancing metal sustainability, characterized by short lead time, low energy consumption, and minimal carbon footprint.

Hosted by Professor Jifeng Liu.

About the Speaker(s)

Hang Yu
Professor of Materials Science and Engineering, Virginia Tech

Hang Yu

Hang Z. Yu is an associate professor in the Department of Materials Science and Engineering at Virginia Tech. He earned his BS in physics from Peking University and his PhD in materials science and engineering from MIT. He conducted postdoctoral research at MIT prior to joining the Virginia Tech faculty in 2016. Yu’s research focuses on materials processing and manufacturing science, emphasizing the underlying process physics, mechanics, and kinetics. His work also aims to leverage the process fundamentals to drive material sustainability to new heights, eg., via solid-state metal recycling, structural repair, and austere condition-resilient manufacturing. Pioneering the research in solid-state metal additive manufacturing, Yu has authored a monograph titled 'Additive Friction Stir Deposition' and co-edited a book: Solid- State Metal Additive Manufacturing: Physics, Processes, Mechanical Properties, and Applications (to be published by Wiley-VCH in 2024). Yu is a recipient of the DARPA Young Faculty Award and currently serves as an editor for Materialia.

Contact

For more information, contact Amos Johnson at amos.l.johnson@dartmouth.edu.