Fig. 1. Schematics of laser-arc hybrid welding. (a) Arc-leading; (b) laser-leading

Fig. 2. Relationship between welding current and wire feeding speed

Fig. 3. Spectral line distribution of Fe I

Fig. 4. Spectral line profile of Ar II at 482.4 nm

Fig. 5. Plasma morphologies under different laser powers and welding modes. (a) Arc-leading, 4000 W;(b) arc-leading, 4500 W; (c) arc-leading, 5000 W;(d) laser-leading, 4000 W; (e) laser-leading, 4500 W;(f) laser-leading, 5000 W

Fig. 6. Variance of plasma with laser power. (a) Electron temperature; (b) electron density

Fig. 7. Relationship between weld penetration and laser power

Fig. 8. (a) Arc-leading, schematic; (b)(c)(d) arc-leading, coupling mechanism;(e) laser-leading, schematic; (f)(g)(h) laser-leading, coupling mechanism

Fig. 9. Plasma morphologies under different wire feeding speeds and welding modes. (a) Arc-leading, 7.5 m·min-1;(b) arc-leading, 8.0 m·min-1; (c) arc-leading, 8.5 m·min-1;(d) laser-leading, 7.5 m·min-1; (e) laser-leading, 8.0 m·min-1; (f) laser-leading, 8.5 m·min-1

Fig. 10. Variance of plasma with wire feeding speed. (a) Electron temperature; (b) electron density

Fig. 11. Relationship between weld penetration and wire feeding speed

Fig. 12. (a) Arc-leading, schematic; (b)(c)(d) arc-leading, coupling mechanism; e) laser-leading, schematic; (f)(g)(h) laser-leading, coupling mechanism

Fig. 13. Cross-sectional morphologies of welded joints.(a) Arc-leading, macro-morphology; (b) laser-leading, acro-morphology; (c) arc-leading, micro-morphology; d) laser-leading, micro-morphology

Fig. 14. Schematics of micro-hardness measurement points. (a) Arc-leading, (b) laser-leading

Fig. 15. Micro-hardness distributions of welded joints. (a) Upper arc zone; (b) lower laser zone

Fig. 16. Stress-strain tensile curves