Making Superalloys Even Better Using Local Phase Transformations at Defects

Abstract:  

Polycrystalline Ni-based superalloys are vital materials for disks in the hot section of aerospace and land-based turbine engines. Improving fuel efficiency and reducing greenhouse gas emissions compel increased performance at higher temperatures. In this presentation, two different approaches to improving high temperature strength and creep resistance are discussed. In the first approach, local ordered phases at stacking faults and microtwins, which are predominant deformation modes at application-relevant temperatures, can be induced by subtle changes to the alloy composition. In the second approach, pre-deformation and then aging can inject a high density of deformation faults, which upon subsequent aging convert to local ordered phases that create strong barriers to subsequent deformation and significantly enhance creep strength. Characterization via electron microscopy methods is critical to revealing these atomic-scale phases, and computational design for promoting these new mechanisms will be discussed.

Bio:

Mills earned his Ph.D. in Materials Science and Engineering at Stanford University in 1985. He joined Ohio State in 1994 as associate professor with tenure after a two-year research associate appointment at the Ecole Polytechnique Federale in Lausanne, Switzerland, and a six-year appointment at Sandia National Laboratories as a senior member of the technical staff. At Ohio State, Mills is the Taine G. McDougal Professor of Engineering and also served as interim chair of the Department of Materials Science and Engineering in 2014-2015.