A dual in-situ monitoring of multiphase dynamics during laser wire fusion process with synchrotron radiation and visible light

The keyhole formed during laser deep penetration welding significantly improves laser energy efficiency. However, this process involves complex interactions of multiphase, making it susceptible to welding defects like spattering and porosity. In-situ monitoring during welding can help identify key factors influencing welding stability. Nevertheless, current monitoring methods have limitations that prevent establishing a clear relationship between the vapor plume and the keyhole for accurate welding mode identification. To address these challenges, this study introduces a novel real-time multimode in-situ monitoring technology that combines ultrafast synchrotron radiation imaging with high-speed visible light imaging, allowing simultaneous observation of multiphase dynamics during laser welding. The research establishes a connection between the internal keyhole and the surface vapor plume evolution in metals. It also finds that vapor plume fluctuations indicate keyhole mode transition, challenging the traditional belief that bright vapor plume emergence signifies this transition. Additionally, the study observes keyhole oscillation frequency ranging from 3.75 kHz to 7.5 kHz, with the frequency increasing as laser power rises.