Fig. 1. Groove geometry of workpiece

Fig. 2. Measurement position of microhardness and sampling position of impact sample

Fig. 3. Dimensions of tensile sample

Fig. 4. Macromorphology of welding joint

Fig. 5. Weld pass morphologies in autogenous laser welding. (a) Macromorphology; (b) partially enlarged view of position 1' in Fig. 5(a); (c) partially enlarged view of position 2' in Fig.5 (a)

Fig. 6. Regional division of multi-layer welding joint

Fig. 7. Middle weld pass morphologies in laser welding with filler wire. (a) Macromorphology; (b) partially enlarged view of position A' in Fig. 7(a); (c) partially enlarged view of position B' in Fig. 7(a); (d) partially enlarged view of position C' in Fig.7 (a); (e) partially enlarged view of position D' in Fig. 7(a); (f) partially enlarged view of position E' in Fig. 7(a)

Fig. 8. Top weld pass morphologies in laser welding with filler wire. (a) Macromorphology; (b) partially enlarged view of position 4 in Fig. 8(a); (c) partially enlarged view of position 5 in Fig. 8(a); (d) partially enlarged view of position 6 in Fig. 8(a); (e) partially enlarged view of position 7 in Fig. 8(a); (f) partially enlarged view of position 8 in Fig. 8(a)

Fig. 9. Microhardness distributions of joint

Fig. 10. Fracture morphologies of impact specimen. (a) Macromorphology of base material; (b) partially enlarged view of position 9 in Fig. 10(a); (c) partially enlarged view of position 10 in Fig. 10(a); (d) macromorphology of middle welding joint; (e) partially enlarged view of position 11 in Fig. 10(d); (f) partially enlarged view of position 12 in Fig. 10(d)