Author ORCID Identifier
Date Available
5-22-2026
Year of Publication
2025
Document Type
Doctoral Dissertation
Degree Name
Doctor of Philosophy (PhD)
College
Engineering
Department/School/Program
Materials Science and Engineering
Faculty
Thomas John Balk
Faculty
Fuqian Yang
Abstract
Multi-principal element alloys (MPEAs) have garnered significant attention in materials science due to their potential for exhibiting a combination of desirable properties stemming from their unique configurational entropy. While early research focused on equiatomic compositions, recent studies have indicated that non-equiatomic MPEAs may offer superior mechanical performance. However, the identification of optimal non-equiatomic compositions remains challenging due to the vast compositional space and the reliance on time-consuming and computationally expensive methods. This dissertation presents a combinatorial thin film approach as a rapid and efficient strategy for discovering two types of materials: nanoporous and bulk MPEAs.
The first study explores the fabrication of nanoporous refractory multi-principal element alloy (np-RMPEA) thin films by combinatorial screening of 2D gradient films. Nanoporous materials with 3D interconnected networks are conventionally fabricated through dealloying of a binary precursor. This approach has been extended to refractory multi-principal element alloys (RMPEAs), which are promising candidates for high-temperature applications.In this chapter, np-RMPEAs were synthesized from magnetron-sputtered magnesium-based thin films. A novel vacuum thermal dealloying (VTD) technique, involving the sublimation of a high vapor pressure element, was employed to mitigate oxidation during the fabrication process.Upon heating VMoNbTaMg under vacuum, the high vapor pressure element (Mg) sublimated, resulting in the formation of a nanoporous structure with ligament size in the range of only 10-12 nm. X-ray photoelectron spectroscopy (XPS) depth profiling revealed reduced ligament oxidation during VTD compared to conventional dealloying methods.Then the nanoporous structures were subjected to vacuum heating for various durations to identify the ligament coarsening kinetics. Analysis of the coarsening behavior revealed that surface diffusion is the dominant mechanism controlling the process.The np-RMPEAs exhibited exceptional resistance to coarsening, maintaining ligament sizes of approximately 25-30 nm even after prolonged exposure to elevated temperatures (700°C for 48 hours). This work demonstrates the potential of the combinatorial thin film approach and VTD for the development of advanced nanoporous materials for high-temperature applications.
The second study demonstrates the successful identification of a single-phase non-equiatomic MnFeCoNiCu alloy exhibiting enhanced hardness, tensile strength, and corrosion resistance compared to its equiatomic counterpart. The combinatorial thin film approach, coupled with characterization techniques such as X-ray diffraction, nanoindentation, and corrosion testing, enabled a systematic rapid screening of a wide range of compositions. The identified non-equiatomic thin film composition exhibited improved mechanical properties and corrosion resistance while maintaining single-phase face centered cubic (FCC) crystal structure at elevated temperature. This superior performance of the non-equiatomic alloy thin film was validated through bulk casting and subsequent mechanical and corrosion testing. In bulk alloy form, the identified non-equiatomic composition maintained the desirable properties that had been measured for thin films samples.
The third study describes the processing conditions for the non-equiatomic alloy identified in chapter two. Hot compression tests were carried out at different temperatures and strain rates. A constitutive equation was derived from the stress-strain curves and can predict flow stress behavior at any temperature and strain rate. By analyzing power dissipation parameter (η) and instability parameter (ξ)- optimum regions were identified for best processing conditions. This optimized processing route paves the way for potential industrial applications of the alloy.
Overall, this dissertation highlights a systematic combinatorial thin film approach for accelerating the discovery and development of novel MPEAs with tailored properties in nanoporous and bulk forms. The successful identification of a high-performance non-equiatomic MnFeCoNiCu alloy and the fabrication of thermally stable np-RMPEAs underscore the versatility and potential of this approach for advancing the field of materials science.
Digital Object Identifier (DOI)
https://doi.org/10.13023/etd.2025.252
Funding Information
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award # DE-SC0019402
Access to electron microscopy and related equipment was provided by the Electron Microscopy Center at the University of Kentucky, a member of the National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the National Science Foundation (ECCS-1542164).
Recommended Citation
Das Gupta, Tibra, "COMBINATORIAL THIN FILM APPROACH TO ACCELERATE MATERIALS DISCOVERY: DEVELOPMENT OF NANOPOROUS AND BULK MULTI-PRINCIPAL ELEMENT ALLOYS" (2025). Theses and Dissertations--Chemical and Materials Engineering. 176.
https://uknowledge.uky.edu/cme_etds/176
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Metallurgy Commons, Nanoscience and Nanotechnology Commons, Other Materials Science and Engineering Commons, Structural Materials Commons
