Fig. 1. Microstructure of ST12 galvanized steel sheet matrix and appearance of zinc coating. (a) Microstructure of matrix; (b) appearance of zinc coating

Fig. 2. Schematic of experimental setup and welding path. (a) Experimental setup; (b) welding path

Fig. 3. Schematic of shear tensile specimen. (a) Spot welding; (b) 30 mm laser welding; (c) 15 mm laser welding

Fig. 4. Influence of spot welding velocity on spot weld morphology. (a) 125 mm/s; (b) 105 mm/s; (c) 75 mm/s

Fig. 5. Influence of inter-sheet gap on spot weld morphology

Fig. 6. Influence of inter-sheet gap on spot weld diameter and underfill size

Fig. 7. Fe and Zn elements distribution on the edge of spot weld prepared at different inter-sheet gaps

Fig. 8. Load-displacement curves and macro-profiles of spot weld prepared at different inter-sheet gaps and macro profiles of failure wendment. (a) Load-displacement curves ; (b) macro profiles of failure weldment

Fig. 9. Failure modes. (a) Partial thickness-partial pullout; (b) pollout failure

Fig. 10. Maximum load of spot weld prepared at different inter-sheet gaps

Fig. 11. Fracture profiles. (a) 0.1 mm inter-sheet gap; (b) 0.6 mm inter-sheet gap; (c) enlarged image of pore region c; (d) enlarged image of region d in Fig.11 (c)

Fig. 12. Process parameter of different welding methods and corresponding cross-section of weldments

Fig. 13. Load-displacement curves of weldment welded by different methods