Defect recognition in Ti-6Al-4V fabrication by in situ monitoring of directed energy deposition using a laser beam
Abstract
Purpose
This paper aims to investigate the relationship between in situ monitoring characteristics and surface defects in laser-based directed energydeposited Ti-6Al-4V.
Design/methodology/approach
In situ monitoring was conducted to extract and quantify the monitoring characteristics of each frame. A two-dimensional contour map was generated using the quantified characteristics to determine the defect formation locations. Computational thermal-fluid dynamics software was used to determine which surface tension terms or shielding gas had a significant effect on the depression of the molten pool.
Findings
This study has made a significant contribution by revealing the direct correlation between the molten pool size and brightness with defect formation in laser-based DED of Ti-6Al-4V. It was found that in regions of reduced height, the molten pool exhibited increased size and brightness, leading to surface depressions due to vapor recoil pressure flattening the molten pool. Moreover, the results highlighted that the enhanced Marangoni forces, caused by a high-temperature gradient, hindered the proper accumulation of molten metal, exacerbating height reductions. This insight provides a deeper understanding of how molten pool dynamics directly influence surface quality, which is a critical factor in DED processes.
Originality/value
This study contributes to understanding of the relationship between in situ monitoring characteristics and surface defects in laser-based directed energy-deposited Ti-6Al-4V. Additionally, by using in situ monitoring and computational analysis, significant insights were gained into the factors influencing molten pool behavior and subsequent surface defects.
Keywords
Acknowledgements
Funding: This work was conducted under the collaboration research between the Institute for Materials Research, Tohoku University and NIDEC Machine Tool Corporation. This work was partly supported by the Inter-University Cooperative Research Program (Proposal No. 202012-CRKEQ-0416 and 202112-CRKEQ-0408) of the Cooperative Research and Development Center for Advanced Materials, Institute for Materials Research, Tohoku University. This work was supported in part by JST Moonshot R&D Program, Grant Number JPMJMS223B. One of the authors, Lingxiao Ouyang, would like to acknowledge the financial support from the Amano Institute of Technology Scholarship.
Conflict of interest: The authors do not have a conflict of interest to be mentioned for their original work submission.
Citation
Ouyang, L., Wang, H., Aoyagi, K., Imamiya, Y., Zhao, Y. and Chiba, A. (2024), "Defect recognition in Ti-6Al-4V fabrication by
Publisher
:Emerald Publishing Limited
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