Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs)
The study is devoted to the investigation of the nanomechanical behavior of nanostructured BCC high entropy alloys processed through High-pressure Torsion (HPT). An understanding of the mechanical behavior of nanocrystalline HfNbTiZr HEA with single-phase BCC structure is obtained. Equimolar HfNbTiZ...
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| Format: | Final Year Project (FYP) |
| Language: | English |
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Nanyang Technological University
2021
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| Online Access: | https://hdl.handle.net/10356/150873 |
| _version_ | 1811695228683288576 |
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| author | Nanasekaran, Pritiba |
| author2 | Upadrasta Ramamurty |
| author_facet | Upadrasta Ramamurty Nanasekaran, Pritiba |
| author_sort | Nanasekaran, Pritiba |
| collection | NTU |
| description | The study is devoted to the investigation of the nanomechanical behavior of nanostructured BCC high entropy alloys processed through High-pressure Torsion (HPT). An understanding of the mechanical behavior of nanocrystalline HfNbTiZr HEA with single-phase BCC structure is obtained. Equimolar HfNbTiZr BCC HEA samples were processed through HPT with ¼,1, 2, and 5 number of turns at RT. The microstructure of HPT processed HEA samples were observed through the analysis of SEM, TEM, XRD, Nanoindentation and Vickers Hardness test results. It was found that the mean grain sizes of HfNbTiZr HPT samples decrease as a function of the quantity of HPT turns, and a nanocrystalline microstructure was obtained. XRD results reveal that the HPT processing decreases the grain size of the HfNbTiZr without changing phase, remaining as a single-phase BCC. Vickers Hardness and Nanoindentation experiments reveal that the hardness of the HfNbTiZr HPT samples increases significantly as the number of HPT turns increases, proving the Hall-Petch grain strengthening ability of the HEA. The HfNbTiZr HPT samples also exhibit a comparable deformation mechanism to that of conventional BCC metals. The activation volume, 𝑉∗ of the HfNbTiZr samples corresponded to the literature on the BCC metals where the 𝑉∗ values are commonly reported to be at the order 10𝑏³. The HfNbTiZr samples are assumed to have a thermally activated double-kink mechanism as a rate-controlling deformation mechanism. This reveals that the screw dislocations of the BCC HfNbTiZr samples are controlled by a thermally activated kink-pair nucleation process. |
| first_indexed | 2024-10-01T07:20:08Z |
| format | Final Year Project (FYP) |
| id | ntu-10356/150873 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T07:20:08Z |
| publishDate | 2021 |
| publisher | Nanyang Technological University |
| record_format | dspace |
| spelling | ntu-10356/1508732021-06-03T08:42:52Z Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs) Nanasekaran, Pritiba Upadrasta Ramamurty School of Mechanical and Aerospace Engineering uram@ntu.edu.sg Engineering::Materials::Nanostructured materials Engineering::Mechanical engineering The study is devoted to the investigation of the nanomechanical behavior of nanostructured BCC high entropy alloys processed through High-pressure Torsion (HPT). An understanding of the mechanical behavior of nanocrystalline HfNbTiZr HEA with single-phase BCC structure is obtained. Equimolar HfNbTiZr BCC HEA samples were processed through HPT with ¼,1, 2, and 5 number of turns at RT. The microstructure of HPT processed HEA samples were observed through the analysis of SEM, TEM, XRD, Nanoindentation and Vickers Hardness test results. It was found that the mean grain sizes of HfNbTiZr HPT samples decrease as a function of the quantity of HPT turns, and a nanocrystalline microstructure was obtained. XRD results reveal that the HPT processing decreases the grain size of the HfNbTiZr without changing phase, remaining as a single-phase BCC. Vickers Hardness and Nanoindentation experiments reveal that the hardness of the HfNbTiZr HPT samples increases significantly as the number of HPT turns increases, proving the Hall-Petch grain strengthening ability of the HEA. The HfNbTiZr HPT samples also exhibit a comparable deformation mechanism to that of conventional BCC metals. The activation volume, 𝑉∗ of the HfNbTiZr samples corresponded to the literature on the BCC metals where the 𝑉∗ values are commonly reported to be at the order 10𝑏³. The HfNbTiZr samples are assumed to have a thermally activated double-kink mechanism as a rate-controlling deformation mechanism. This reveals that the screw dislocations of the BCC HfNbTiZr samples are controlled by a thermally activated kink-pair nucleation process. Bachelor of Engineering (Mechanical Engineering) 2021-06-03T08:42:51Z 2021-06-03T08:42:51Z 2021 Final Year Project (FYP) Nanasekaran, P. (2021). Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs). Final Year Project (FYP), Nanyang Technological University, Singapore. https://hdl.handle.net/10356/150873 https://hdl.handle.net/10356/150873 en application/pdf Nanyang Technological University |
| spellingShingle | Engineering::Materials::Nanostructured materials Engineering::Mechanical engineering Nanasekaran, Pritiba Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs) |
| title | Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs) |
| title_full | Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs) |
| title_fullStr | Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs) |
| title_full_unstemmed | Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs) |
| title_short | Nanomechanical behaviour of nano-structured BCC high entropy alloys (HEAs) |
| title_sort | nanomechanical behaviour of nano structured bcc high entropy alloys heas |
| topic | Engineering::Materials::Nanostructured materials Engineering::Mechanical engineering |
| url | https://hdl.handle.net/10356/150873 |
| work_keys_str_mv | AT nanasekaranpritiba nanomechanicalbehaviourofnanostructuredbcchighentropyalloysheas |