Author ORCID Identifier
https://orcid.org/0000-0002-8037-0612
Date Available
5-15-2025
Year of Publication
2025
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Engineering
Department/School/Program
Chemical and Materials Engineering
Faculty
Dr. T. John Balk
Faculty
Dr. Fuquain Yang
Abstract
Multi-principal element alloys (MPEAs)/high-entropy alloys (HEAs) are a class of materials that provide novel and superior combinations of properties, with promise for use in challenging application areas that many of the current established materials cannot fit. With a higher number of constituent elements, many of the newly created alloys are compositionally complex in nature, known to contain combinations of relatively soft FCC phases, hard BCC phases, and, in some cases, even harder intermetallic phases. Microstructural study of these new materials is essential to understanding the enhanced properties they may possess, but their complexity can make this study much more challenging than for a typical single-phase alloy.
Characterizing an alloy’s microstructure is vital to understanding the mechanisms that govern its properties. While there are many methods of characterization, microscopy is one of the most widely applicable fields such as biology, medicine, art, archeology, and of course, material science. Several techniques make up the microscopy characterization suite: a. Imaging at all levels through optical microscopy, SEM, and TEM b. Elemental analysis through EDS in SEM and TEM c. Crystallographic analysis through EBSD and TKD in SEM, and diffraction in TEM. All of these characterization methods combine and complement each other to facilitate robust understanding of a material’s microstructure.
In this dissertation, the WMoFeNi alloy system is studied in depth through various forms of microscopy-based characterization. The general alloy system and its 3 constituent phases are each studied through complementary characterization methods, including most of the techniques outlined above, to further understanding of the system and its mechanisms, particularly ones that govern its deformation. Microscopic imaging at all levels, EDS, and EBSD are all utilized in-depth to further understand the formation and deformation mechanisms of the constituent phases of the WMoFeNi alloy system and the FCC phase in particular. Then the application of EBSD to this alloy system is tested through multiple studies encompassing metallographic preparation, software settings, and post-processing methods. Recommendations are made on how to optimize EBSD analysis of this alloy system in all of these categories, as well as future studies that will further the application of EBSD to this material system. A relationship between computational and experimental tests is established and its use to aid development of a crystal structure model for two of the characteristic phases in this alloy system is demonstrated.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2025.203
Funding Information
Research was sponsored by DEVCOM-Army Research Laboratory and was accomplished under Cooperative Agreement Number W911NF-21-2-0075. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory or the United States Government. The United States Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.
This work was performed in part at the University of Kentucky Electron Microscopy Center, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (NNCI-2025075).
Recommended Citation
Allamon, Alexandra, "Microstructural Characterization of Complex Metal Alloy Systems with a Focus on Electron Microscopy" (2025). Theses and Dissertations--Chemical and Materials Engineering. 175.
https://uknowledge.uky.edu/cme_etds/175
