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Functional Multi-Principal Element Alloys: Mechanical, Magnetic, and Electrochemical Properties
Nawaz, Tahir
Nawaz, Tahir
Date
2025-11
Author
Advisor
Type
Dissertation
Degree
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29.330-2025.03a Tahir Nawaz-COMPRESSED.pdf
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Description
A Doctor of Philosophy Dissertation in Materials Science and Engineering by Tahir Nawaz entitled, “Functional Multi-Principal Element Alloys: Mechanical, Magnetic, and Electrochemical Properties”, submitted in November 2025. Dissertation advisor is Dr. Mehmet Egilmez and dissertation co-advisor is Dr. Wael Abuzaid. Soft copy is available (Dissertation, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Abstract
Functional multi-principal element alloys (MPEAs) have emerged as a transformative class of materials due to their vast compositional freedom, tunable defect chemistry, and coupled physical phenomena. However, despite extensive progress in their structural applications, the composition-structure-property relationships governing their mechanical, magnetic, and electrochemical functionality remain insufficiently understood. This thesis systematically investigates two families of MPEAs to establish fundamental links between alloy chemistry, microstructural evolution, and functional response.The first part of this work examines FeMnAlNi-based shape memory alloys alloyed with vanadium. Through cyclic heat treatment and controlled aging, abnormal grain growth and a dominant BCC superelastic phase were achieved, enabling recoverable strains up to ~6% and transformation stress of 1GPa with stable hysteresis. The second part explores disorder-driven ferromagnetism in equiatomic NiCoFeCr high-entropy alloy. Magnetic measurements reveal a complex interplay between itinerant magnetism and chemical disorder, with a suppressed Curie temperature (Tc ≈ 92 K) and a secondary magnetic anomaly at 125 K, consistent with cluster freezing. Critical exponent analysis confirms deviation from mean-field behavior, aligning with a three-dimensional Heisenberg model. The final part investigates CoNiFe(Cr/V)-based MPEAs as bifunctional electrocatalysts. V incorporation reduces charge transfer resistance and enhances hydrogen evolution kinetics, achieving competitive overpotentials in both alkaline and acidic media. Collectively, this work establishes compositionally tunable pathways to engineer multifunctional MPEAs, advancing their potential in adaptive structures, spin-based technologies, and energy conversion systems.