Fig. 1. Experimental setup for filler wire laser welding test with laser focus rotation

Fig. 2. Shape and size of the test piece subjected to tensile test

Fig. 3. Morphologies of weld front and cross-section under different focus rotation radii r and frequencies f

Fig. 4. Images taken in filler wire laser welding with laser focus rotation by using a high-speed camera. (a) t+0 ms; (b) t+1 ms; (c) t+2 ms; (d) t+3 ms; (e) t+4 ms; (f) t+5 ms; (g) t+6 ms; (h) t+7 ms

Fig. 5. Images taken in filler wire laser welding without laser focus rotation by using a high-speed camera. (a) t+0 ms; (b) t+1.5 ms; (c) t+3 ms; (d) t+4.5 ms; (e) t+6 ms; (f) t+7.5 ms; (g) t+9 ms; (h) t+10.5 ms

Fig. 6. Weld morphologies and pore distributions under two welding processes. (a) Cross-section of the weld in filler wire laser welding; (b) cross-section of the weld in filler wire laser welding with focus rotation (f=150 Hz, r=0.6 mm); (c) welded joint in filler wire laser welding without focus rotation; (d) welded joint in filler wire laser welding with focus rotation; (e) dispersed pores of large sizes in the weld; (f) tiny pores around the fusion line

Fig. 7. Microstructures of welded joint around the fusion lines under different welding processes. (a) Filler wire laser welding without focus rotation; (b) filler wire laser welding with focus rotation

Fig. 8. Microstructures of welded joint prepared by filler wire laser welding without focus rotation. (a) Near fusion line; (b) between fusion line and weld center; (c) weld center

Fig. 9. Microstructures of welded joint prepared by filler wire laser welding with focus rotation. (a) Near fusion line; (b) between fusion line and weld center; (c) weld center

Fig. 10. Back-scattered electron images of welds center. (a) Filler wire laser welding without focus rotation; (b) filler wire laser welding with focus rotation

Fig. 11. Surface distributions of elements in central areas of welds prepared with two different welding processes. (a) Filler wire laser welding without focus rotation; (b) filler wire laser welding with focus rotation

Fig. 12. Secondary electron images of welds center.(a) Filler wire laser welding without focus rotation; (b) filler wire laser welding with focus rotation

Fig. 13. XRD patterns of two welds

Fig. 14. Microhardness of two welded joints

Fig. 15. Tensile stress-strain curves of test pieces in two welding processes

Fig. 16. SEM images of tensile fracture of test pieces prepared by filler wire laser welding without focus rotation. (a) Area a; (b) area b; (c) area c; (d) pore

Fig. 17. SEM images of tensile fracture of test pieces prepared by filler wire laser welding with focus rotation. (a) Area a; (b) area b; (c) area c; (d) pore