Some Problems on Grain Boundary Dynamics

Fadi Abdeljawad, PhD
Associate Professor
Department of Materials Science and Engineering 
Lehigh University

Abstract: Nearly all structural and functional materials are polycrystalline systems, their microstructures are composed of differently oriented crystalline grains that are internally joined at grain boundaries (GBs). It is well accepted that GBs play a critical role in controlling the observable properties of engineering materials. In this talk, which is delivered in two parts, we present our recent work dealing with GB dynamics in advanced materials.

We first start by examining a GB-driven instability that has direct implications to additively manufactured lattice materials. We demonstrate a morphological instability, in which a polycrystalline micro- or nano-rod breaks up at GBs into an array of isolated domains. We show that GBs play a destabilizing role in which the critical wavelength for the instability decreases with increasing the GB energy. Computational studies predict temporal evolution of interfacial profiles in quantitative agreement with experimental observations.

We then direct our attention to high entropy alloys (HEAs), which are a class of materials consisting of multiple principal elements in equiatomic or near equiatomic concentrations. Recent experimental findings revealed segregation of elemental species to GBs in several HEAs, which is suggested to be the mechanism for the observed sluggish grain coarsening in these alloys. We present computational studies of GB segregation in HEAs and its impact on GB migration. Our results reveal a plethora of possible segregation profiles that are dependent on alloy-alloy interactions within the GB. In broad terms, our approach provides avenues to employ GB segregation as a strategy to design HEAs with tailored microstructures.

Biography: Dr. Fadi Abdeljawad is an Associate Professor in the Department of Materials Science and Engineering at Lehigh University. Prior to joining Lehigh in 2023, he was an Assistant-then-Associate Professor (2018-2023) at Clemson University. From 2014-2018, Dr. Abdeljawad was a Staff Scientist in the Computational Materials and Data Science Department at Sandia National Laboratories. He obtained his M.A. (2010) and Ph.D. (2014) from Princeton University with a primary focus on theoretical and computational materials science. He is a recipient of the 2020 Army Research Office Young Investigator Program Award; 2022 TMS Early Career Faculty Fellow Award; and 2019 Ralph E. Powe ORAU DOE Award. Abdeljawad’s research is funded by DOD, DOE, NSF, and U.S. National Laboratories.