Graduate Student Seminar

Oxide Dispersion Strengthening via Additive Processing: A Revolutionary New Approach for High Temperature Alloys

For decades, it has been known that oxide dispersion strengthening (ODS) is one of the most effective means of producing creep-resistant alloys.  However, the widespread deployment of ODS has been limited by the complex, conventional processing route to create these alloys involving mechanical alloying and subsequent thermomechanical processing.  A new additive ODS process using laser powder bed fusion has recently been developed by collaborators at NASA Glenn Research Center and enables the synthesis of ODS alloys in a single step.  This route has been utilized to design an ODS solid solution alloy (GRX-810) which has exceptional high temperature properties when compared with other solid solution Ni-base superalloys.  Detailed electron microscopy analysis has been performed to characterize the structure and composition of the oxide dispersoids, and other minor grain boundary phases.  In addition, diffraction contrast imaging STEM imaging reveals that a large dislocation density is created during the build process, and the oxide dispersoids contribute to a remarkable stabilization of the dislocation substructure, even after long time at high temperature.  These microstructure insights are being used to understand the significantly improved creep resistance of GRX-810 in comparison to a model NiCoCr ODS alloy.  The present status of this work, understanding of strengthening mechanisms, and prospects for developing a wider range of ODS strengthened alloys will be discussed.

Michael Mills 
Chair, Department of Materials Science and Engineering
Taine G. McDougal Professor of Engineering
Center for Electron Microscopy and Analysis (CEMAS)
The Ohio State University

Professor Mills earned his Ph.D. degree in Materials Science and Engineering at Stanford University in 1985. After a two-year research associate appointment at the Ecole Polytechnique Federale-Lausanne, Switzerland, and a six-year appointment as Senior Member of Technical Staff at Sandia National Laboratories, Livermore, he joined the Department of Materials Science and Engineering at the Ohio State University in 1994.  Mills was promoted to Professor in 2000 and was appointed as the McDougal Professor of Engineering in 2004.  Since 2019, he has been serving as Chair of the Department of Materials Science and Engineering at OSU (he was Interim Chair in 2014-2015). Mills and his group are developing new insights into the mechanical behavior of several important metallurgical systems through a detailed understanding of elementary deformation mechanisms. Recent research has included studies of deformation behavior in commercial titanium and zirconium alloys, strengthening mechanisms in aluminum alloys and novel ferritic steels, dislocation processes and microstructure development in nickel-based superalloys, and deformation mechanisms in high entropy alloys.  This understanding forms the foundation for models of behavior that have significant basic science content and are also relevant to industrial applications through the development of Integrated Computational Materials Engineering tools.  He is a Fellow of the American Society for Metals, was inducted as Fellow of TMS in 2015, and has received the Oleg D. Sherby Award from TMS for research in high temperature materials. Mills received the Alexander Von Humboldt Research Fellowship in 1996 and in 2019 he received the Alexander von Humboldt Research Award.  In 2021, he was awarded the Heyn Medal of Honor from the DGM (Deutsche Gesellschaft für Materialkunde) for achievements in the field of materials science and engineering, and he holds honorary doctorate from the Ruhr University, Bochum, which was awarded in March 2022.