Fig. 1. Experimental principle. (a) Modulation of light; (b) planar scanning welding

Fig. 2. Images of keyhole at different laser powers. (a) 3 kW; (b) 4 kW; (c) 6 kW

Fig. 3. Variation of size of two parts of deep penetration keyhole with laser power

Fig. 4. Images of keyhole at different light output time. (a) 1 ms; (b) 4 ms; (c) 7 ms; (d) 10 ms

Fig. 5. Cross-section morphology of keyhole/weld at different light output time. (a) 1 ms; (b) 4 ms; (c) 7 ms; (d) 10 ms

Fig. 6. Influence of laser power on closing time of keyhole

Fig. 7. Relationship between solidification time of molten pool with laser output time at different laser powers

Fig. 8. Solidification time of molten pool at different laser induced melting depth

Fig. 9. Schematic of small hole morphology under the action of laser