Fig. 1. Schematic of laser deep penetration welding process

Fig. 2. Overall tensile strength versus heat input^[26]

Fig. 3. Schematic of laser filler welding process

Fig. 4. Application of laser brazing in automotive industry^[33]. (a) Laser joining of hatchback parts; (b) principle diagram of laser brazing

Fig. 5. Principle diagram of trifocal laser brazing^[39]

Fig. 6. Thermal imaging in brazing process^[39]. (a) Monofocal brazing; (b) trifocal brazing

Fig. 7. Microstructures at selected regions for joints obtained with different filler metals^[43] . (a)-(c) Pure Al; (d)-(f) AlSi5; (g)-(i) AlSi12

Fig. 8. Schematic of laser-arc hybrid welding process^[45]

Fig. 9. Weld morphologies under different welding schemes^[46] . (a) Laser guided arc; (b) arc guided laser

Fig. 10. Formation of laser-dominated region and laser-MIG hybrid-dominated region^[48]. (a) Laser-dominated region in laser welding process; (b) MIG-dominated region in MIG welding process; (c) laser-MIG hybrid-dominated region in laser-MIG hybrid welding process

Fig. 11. Weld appearance and microstructures for laser-MIG hybrid welding^[48]. (a) Weld appearance; (b) fine dendrite in laser-MIG hybrid-dominated region; (c)-(e) morphologies of fusion line between laser-MIG hybrid-dominated region and laser-dominated region; (f) coarse dendrite in laser-dominated region

Fig. 12. Schematic for detection-compensation-tracking of weld seam ^[56]

Fig. 13. DIGI-LAS/MDL system used for roof welding^[58]

Fig. 14. Relationship model between keyhole-induced porosity and multi-sensing signals^[61]. (a) Relationship between keyhole depth variation and porosity; (b) CNN-based porosity detection with keyhole opening morphological characteristics

Fig. 15. Schematic for detection of laser welding defects based on laser vision^[65]