Fig. 3
From: In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing
Time-series radiographs acquired during LAM of an Invar 36 s layer melt track (MT2) under P = 209 W, v = 13 mm s−1 and LED = 16.1 J mm−1, see details in Supplementary Movie 5. Snapshots of MT2 at various stages of LAM: a formation of a molten pool on the second powder layer; b the growth of MT2 via wetting on MT1; c MT2 undergoes laser-re-melting, where RZ indicates the laser re-melting zone; d, MT2 completely solidifies. (c-d) The large droplet spatter (purple dotted circle) failed to eject from the powder bed. Other key phenomena involved during molten pool wetting: e re-melting of MT1; f an extension of MT2 before wetting on MT1; g entrapment of gas bubble (see yellow dotted circles); and h thin powder layer (see red dotted circles). Three pore evolution mechanisms induced by laser re-melting: i pore coalescence; j pore dissolution; and k pore dispersion into smaller pores. Scale bars = 500 µm
