Fig. 1. Schematic of test device

Fig. 2. Schematics of tensile specimens. (a) Tensile specimen at room temperature; (b) tensile specimen at 1500 ℃ high temperature

Fig. 3. Penetration depth versus laser power at different welding speeds

Fig. 4. Weld morphologies at different welding parameters. (a) P＝1.5 kW, v＝2 m/min; (b) P＝2.0 kW, v＝3 m/min；(c) P＝2.5 kW, v＝2 m/min; (d) P＝4.5 kW, v＝3 m/min

Fig. 5. Surface macroscopic morphologies of Ta-10W butt weld. (a) Front side; (b) back side; (c) enlarged view of point 1 in Fig.5 (a) (magnification of 100)

Fig. 6. Behaviors of splash escaping from molten pool and macroscopic morphology of splashing particles. (a) 0 ms; (b) 1 ms; (c) 2 ms; (d) 3 ms; (e) 4 ms; (f) splashing particles (magnification of 30)

Fig. 7. Microstructure of joint. (a) Macroscopic morphology; (b) upper part of weld center area; (c) lower part of weld center area; (d) upper part of fusion line; (e) middle part of fusion line

Fig. 8. Micro-hardness distribution of butt joint

Fig. 9. Tensile strength of joint

Fig. 10. Fracture of tensile specimen at room temperature. (a) Macroscopic morphology of fracture (35×); (b) enlarged view of point 1 in Fig.10(a) (500×); (c) right morphology of fracture (50×); (d) enlarged view of point 2 in Fig.10 (c) (2000×); (e) middle morphology of fracture (100×); (f) enlarged view of point 3 in Fig.10 (e) (500×)

Fig. 11. Fracture of upper specimen at 1500 ℃ high temperature. (a) Macroscopic morphology of fracture (37×); (b) enlarged view of point 1 in Fig.11 (a) (100×); (c) enlarged view of point 2 in Fig.11 (a) (300×)

Fig. 12. Fracture of lower specimen at 1500 ℃ high temperature. (a) Macroscopic morphology of fracture (40×); (b) enlarged view of point 1 in Fig.12 (a) (300×)