In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing

Chu Lun Alex Leung, Sebastian Marussi, Robert C. Atwood, Michael Towrie, Philip Withers, Peter Lee

    Research output: Contribution to journalArticlepeer-review

    Abstract

    The laser-matter interaction and solidification phenomena associated with laser additive manufacturing (LAM) remain unclear, limiting its applications and process optimisation. Here, through in situ and operando high-speed synchrotron X-ray imaging, we reveal the underlying physical phenomena during the deposition of the first and second layer melt tracks. We show that the laser-induced gas/vapour jet promotes the formation of melt tracks and denuded zones via spattering (at velocities of 1 m s-1). We also uncover new mechanisms of pore migration by Marangoni-driven flow (at velocities of 0.4 m s-1), pore dissolution and dispersion by laser re-melting. We develop a mechanism map for predicting the evolution of melt features, including changes in melt track morphology from a continuous hemi-cylindrical track to disconnected beads with decreasing linear energy density; and improved molten pool wetting with increasing laser power. Our results clarify aspects of the physics behind LAM, which are critical for its development.
    Original languageEnglish
    Article number1355
    JournalNature Communications
    Volume9
    Early online date10 Apr 2018
    DOIs
    Publication statusPublished - 2018

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