“Phase Dependent Microstructures and their Deformation Mechanisms in Transitional Metal Carbides”

Abstract:

Transitional metal carbides comprise a class of high and ultrahigh melting temperature materials with tremendous thermo-mechanical property potential. Depending on temperature and phase type, brittle behavior to significant plasticity responses can be observed. By tailoring the phase fraction within each carbide, opportunities for benchmark
improvements in thermo-mechanical performance can be achieved through microstructural engineering. This seminar will address the underlying phase stability behavior in these
carbides and how crystallography controls microstructure and deformation mechanisms. In particular, an ab initio investigation will be discussed that reveals a competition between vacancy-ordered and fault forming phases in the group VB metal carbides, with the latter phases becoming more favorable with decreasing carbon content. This competition is less favorable in the group IVB metal carbides because of their inability to yield a stable intrinsic stacking fault on the close packed planes. The consequences of these phases (and the intrinsic stacking fault) on the deformation slip systems are discussed in terms of the anomalous hardness response found in these carbides. The computational results are connected to experimental dynamical electron diffraction experiments to validate and verify the deformation mechanisms and
energy hierarchy of such slip behavior.

Biography:

Professor Gregory B. Thompson joined the faculty in the Department of Metallurgical & Materials Engineering at The University of Alabama as an Assistant Professor in 2003. He was tenured and promoted to Associate Professor in 2008 and promoted to Professor in 2012. In 2018, he was appointed Distinguished Research Professor
for the UA system and currently holds the James R. Cudworth Chair in Engineering. Outside his faculty duties, Thompson serves as the Director for UA’s Alabama Analytical Research Center and the Director for the Materials Science Ph.D. program. Professor Thompson has published over 250 peer-reviewed articles in his research areas of analytical microscopy and phase transformations and has graduated 18 M.S. and 23 Ph.D. students to date. He received his Ph.D. (2003) and M.S. (1998) from The Ohio State University in Materials Science & Engineering
and a B.S. (1996) in Physics from Brigham Young University. He was awarded UA’s Blackmon-Moody Outstanding Professor of the Year in 2014 and was a TMS Brimacombe medalist in 2017. For more information, please visit http://thompsonresearch.ua.edu.