Fig. 1. Schematic of tensile specimen

Fig. 2. Weld appearances under different welding speeds. (a) 2 m·min-1; (b) 3 m·min-1; (c) 4 m·min-1

Fig. 3. SEM images of welded joint. (a) Macro-morphology; (b) microstructure of weld center; (c) microstructure of weld boundary; (d) microstructure in FZ

Fig. 4. (a) SEM image of microstructure and (b) linear scanning curves of elements in FZ

Fig. 5. (a)(d) Weld center, (b)(e) SMZ, and (c)(f) HAZ of welded joint

Fig. 6. XRD images. (a) WZ; (b) BM and HAZ

Fig. 7. Microhardness distribution of welded joint

Fig. 8. Stress-strain curves. (a) BM; (b) welded joint

Fig. 9. Macroscopic cross section of fracture. (a) BM; (b) welded joint

Fig. 10. Morphologies of tensile fracture. (a) BM; (b) local magnification of M zone in Fig.10(a); (c) local magnification of strengthening phase in Fig.10(a); (d) intergranular fracture of weld; (e) microporous segregation of weld