High entropy alloys (HEAs) based on refractory elements have shown a great potential for high temperature structural applications. In particular, the ones containing Al, exhibits a microstructure similar to the γ-γ' in Ni-based superalloys. While these alloys exhibit impressive strengths at room temperature (RT) and at elevated temperatures, the continuous B2 matrix in these alloys is likely to be responsible for their brittle behavior at RT. Phase stability of five such alloys are studied by thermo-mechanical treatments and characterization techniques using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Two of these alloys showed an inverted microstructure, where the disordered BCC phase becomes continuous, and therefore, they were characterized in detail using SEM, TEM, atom probe tomography (APT) and synchrotron x-ray diffraction experiments. The phenomenon of phase inversion lead to a better combination of strength and ductility as compared to the non-inverted microstructure.To enhance the stability of B2 intermetallic phase which provides the strength when present in a BCC matrix, multicomponent B2 phase compositions stable at 1000°C in some of the above studied alloys, were melted separately. The aim was to establish a single phase B2 at 1000°C and understand the mechanical behavior of these single-phase multicomponent B2 intermetallic alloys. These alloys exhibited a ductile behavior under compression and retained ~1 GPa yield strength at temperature up to 600°C. The ductile nature of these alloys is attributed to the change in bonding nature form directional to metallic bonding, possibly resulting from a significantly high configurational entropy compared to binary or ternary stoichiometric B2 compounds.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc1538735 |
| Date | 08 1900 |
| Creators | Soni, Vishal |
| Contributors | Banerjee, Rajarshi, Srivilliputhur, Srinivasan G., Mishra, Rajiv S., Mukherjee, Sundeep, Scharf, Thomas, Fraser, Hamish |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | xii, 132 pages, Text |
| Rights | Use restricted to UNT Community, Soni, Vishal, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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