AEROSPACE ENGINEERING

Abstract

Nearly all structural materials are polycrystalline systems. They are composed of differently oriented crystalline grains that are joined at internal interfaces, termed grain boundaries (GBs). It is well accepted that GB dynamical processes play a pivotal role in controlling the mechanical properties of structural alloys. Even minute amounts of intended or unintended impurities at GBs result in profound changes to GB dynamical processes. Recent experimental findings demonstrated GB solute segregation as a technique to mitigate grain growth and thermally stabilize the grain structures of nanocrystalline (NC) metallic alloys. In this talk, we discuss our recently developed solute drag model in NC alloys that incorporates solute-solute interactions in both bulk grain and GBs and capture effects such as monolayer, multilayer, and nonsymmetrical segregation. GB solute drag pressure is shown to exhibit a self-similar behavior, in which the maximum drag scales with the GB heat of mixing. A new drag-velocity relation is proposed and used to perform quantitative analysis, demonstrating the chief role that solute drag plays in the experimentally-observed thermal stability of NC alloys.

Speaker

Dr. Fadi Abdeljawad

Assistant Professor in the Department of Mechanical Engineering at Clemson University with a joint appointment in the Department of Materials Science and Engineering. Prior to joining Clemson in 2018, he was a Senior Member of Technical Staff in the Computational Materials and Data Science Department at Sandia National Laboratories. He received his M.A. (2010) and Ph.D. (2014) from Princeton University with a primary focus on Theoretical and Computational Materials Science. His research strives to develop theoretical and computational models to tackle moving boundary problems in materials science, including phase transitions, interface thermodynamics, and microstructural evolution. His research is funded by several agencies including NSF, DOD, and DOE.