Figure 4
Tracking of powder motion during the laser powder bed fusion process of Ti-6Al-4V. (a) Dynamic X-ray images collected at different times, with red arrows indicating the velocity of each individual powder particle. In this case, the laser power and beam size are 520 W and ~220 µm (1/e2), respectively. The particle size is in the range of 5–45 µm, and the powder layer thickness is ~100 µm. The full tracking procedure for two laser power conditions are shown in Supplementary Videos 5 and 6. (b) Moving trajectories of five different particles P1–P5, which are marked out using cyan dashed squares in (a). The dimensions of (b) and each image in (a) are identical. The vertical and horizontal cyan dashed lines specify the location of the laser beam and the top surface of the powder bed, respectively. The insets of (b) show a particle merging process. All the scale bars in (a) and (b) are 100 µm. (c,d) Statistics of the powder moving velocity. Distributions of (c) ejection speed and (d) ejection angle of particles outside the powder bed under the laser power of 340 W and 520 W are shown in blue and red colors, respectively.
