Fig. 1. Laser welding system

Fig. 2. Tensile specimen of welded joint

Fig. 3. Side bend specimen of welded joint

Fig. 4. Appearances of welded joint. (a) Front surface of weld; (b) back surface of weld; (c) macroscopic cross-sectional morphology of weld

Fig. 5. Metallographic microstructures of base material at different magnifications

Fig. 6. SEM images of base material at different magnifications

Fig. 7. TEM morphologies of base material at different magnifications

Fig. 8. Metallographic microstructures of weld at different magnifications

Fig. 9. SEM images of weld at different magnifications

Fig. 10. TEM images of weld at different magnifications

Fig. 11. Metallographic microstructures of HAZ. (a)(b) At different magnifications; (c) HAZ around fusion line

Fig. 12. SEM images of HAZ at different magnifications

Fig. 13. TEM images of HAZ at different magnifications

Fig. 14. Residual stress of welded joint

Fig. 15. Morphologies of tensile fractures.(a) Macroscopic fracture; (b)(c)(d) microscopic morphologies at different areas of fracture

Fig. 16. Microhardness on upper surface of welded joint

Fig. 17. Microhardness in middle of welded joint

Fig. 18. Microhardness in root of welded joint

Fig. 19. Morphologies of impact fracture. (a)(c)(e) Macroscopic morphologies; (b)(d)(f) microscopic morphologies