Fig. 3: Analysis of surface and internal flow velocity of the keyhole molten pool.

The flow velocity of EN and EP on the trajectory of a single tracer particle calculated from X-ray imaging. a–c Trajectories on the surface (red colour) and inside (blue colour). d–f Flow velocity of EP and EN stage on the two trajectories. The thicknesses of base metal are 5 mm (a, d), 8 mm (b, e), 10 mm (c, f). Error bars represent one standard deviation (SD) from the mean.