Tosi, Riccardo;
Leung, Chu Lun Alex;
Tan, Xipeng;
Muzangaza, Emmanuel;
Attallah, Moataz M;
(2022)
Revealing the microstructural evolution of electron beam powder bed fusion and hot isostatic pressing Ti-6Al-4V in-situ shelling samples using X-ray computed tomography.
Additive Manufacturing
, 57
, Article 102962. 10.1016/j.addma.2022.102962.
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J0022_2022 Revealing the microstructural evolution of EBPF and HIP of Ti64 in situ shelling samples using XCT.pdf - Published Version Download (13MB) | Preview |
Abstract
Electron beam powder bed fusion/hot isostatic pressing (E-PBF/HIP), also known as in-situ shelling, is an emerging technology that produces components by only forming their shells whilst retaining sintered powder at the core, and then using HIP to consolidate the entire structure. E-PBF/HIP can boost additive manufacturing productivity, however, the fundamental understanding of the process-microstructure-property correlations remains unclear. Here, we systematically investigate the microstructural evolution of E-PBF/HIP Ti-6Al-4V parts as a function of hatch melting parameters. All HIPped samples achieve full densification, however, their microstructures are significantly different from one another. Using X-ray computed tomography (XCT) and optical microscopy, our results show that the HIPped Ti-6Al-4V microstructure can be controlled by varying the porosity, P (%), pore surface areas and morphology in the as-built parts with a single set of HIP parameters. The HIPped microstructures still exhibit the as-built columnar grains when the as-built porosity, P < 3 % with mainly spherical micro-pores; a mixture of columnar and equiaxed grains when the 3 % < P ≤ 5 % with a tortuous and interconnected pore network; and equiaxed grains when P > 5 % with a highly dense pore network. This work suggests two main drivers for the grain morphology transitions during HIP: (1) a dramatic increase in pore volume increases the localised applied pressure up to 4 times at the core region of the sample and (2) minimise lack-of-fusion pores with high surface energies, promoting dynamic recrystallisation. This study provides a fundamental insight into the E-PBF/HIP technology, showing the feasibility to tailor microstructural properties of E-PBF built parts whilst boosting additive manufacturing productivity.
| Type: | Article |
|---|---|
| Title: | Revealing the microstructural evolution of electron beam powder bed fusion and hot isostatic pressing Ti-6Al-4V in-situ shelling samples using X-ray computed tomography |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.addma.2022.102962 |
| Publisher version: | http://doi.org/10.1016/j.addma.2022.102962 |
| Language: | English |
| Additional information: | This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third-party material in this article are included in the Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ |
| Keywords: | Additive manufacturing, Hot isostatic pressing, Microstructure, Consolidation, X-ray computed tomography |
| UCL classification: | 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 UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10151175 |
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