Fan, Xianqiang;
(2023)
Magnetic Field Control of Melt Pool Flow and Keyhole Dynamics during Additive Manufacturing.
Doctoral thesis (Ph.D), UCL(University College London).
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Abstract
Metal additive manufacturing (AM), also known as metal 3D printing, is revolutionising our manufacturing industries. However, there are several major concerns with process instability developing during AM, including a complex and intensive flow appearing within the melt pool and keyhole instability. Developing methods to control process instability has been a priority in the AM community. This work investigates the potential use of a magnetic field to control process instability in AM, with a specific focus on using in situ synchrotron X-ray imaging to reveal the magnetic field control mechanisms. Firstly, the results demonstrated that the application of a static magnetic field (0.12 T) to the directional solidification (DS) of a Ga-In alloy can disrupt and potentially prevent solute channel formation through the thermoelectric magnetohydrodynamic (TEMHD) effect. Then, by applying a static magnetic field (0.2 T) to laser directed energy deposition (DED) process of a nickel-based superalloy, the Marangoni flow within the melt pool was observed to be disrupted, and the flow direction was dependent on the magnetic field orientation, which indicates that the TEMHD effect can dominate flow patterns. Furthermore, a magnetic field of 0.6 T was applied to the laser powder bed fusion (LPBF) of Al alloys under keyhole conditions. The findings showed that the keyhole appeared more stable and there was a reduction in keyhole porosity, which can be attributed to the thermoelectric effect stabilising the keyhole when a static magnetic field is applied. These observations and the underlying physics revealed in this research offer a new pathway for using an external magnetic field to control process instability in multiple metal solidification processes, including directional solidification and additive manufacturing. By employing this approach, the microstructure can be tailored, and pores can be minimised during the solidification process.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Magnetic Field Control of Melt Pool Flow and Keyhole Dynamics during Additive Manufacturing |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2023. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Mechanical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10174669 |
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