Fig. 1. Thermo-physical parameters of pure tungsten varying with temperature. (a) Thermal conductivity of bulk tungsten^[22] and tungsten powder(porosity is about 40%) varying with temperature; (b) density of bulk tungsten^[22] and tungsten powder (porosity is about 40%) varying with temperature; (c) specific heat of tungsten^[22] varying with temperature

Fig. 2. Flow chart of temperature field in SEBM numerical simulation

Fig. 3. Computational model for analytical solution verification

Fig. 4. Comparison of numerical solution and analytical solution. (a) Temperature distributions along the scanning direction when time is 10 ms; (b) thermal cycle curves at coordinate point (5，0，0)

Fig. 5. Influence of scanning rate on molten pool and temperature field. (a) Molten pool shapes and sizes at four scanning rates; (b) thermal cycle curves at different scanning rates; (c) sizes of molten pool varying with scanning rates

Fig. 6. Influence of electron beam radius on molten pool and temperature field. (a) Thermal cycle curves at different radii; (b) sizes of molten pool varying with beam radii

Fig. 7. Influence of heat source power on molten pool and temperature field. (a) Thermal cycle curves at different powers; (b) sizes of molten pool varying with heat source powers

Fig. 8. Two-layer multi-track scanning computational model

Fig. 9. Temperature field and molten pool when the electron beam scans to different positions (The enlarged molten pool is in the upper right corner; the dotted line is the scanning center line). (a)(c) Midpoint of the first track, the sixth track and the eleventh track of the first layer; (d)(f) midpoint of the first track, the sixth track and the eleventh track of the second layer

Fig. 10. Thermal cycle curves at the midpoint of each track for the two-layer multi-track scanning. (a) Thermal cycle curves of the midpoint of each track in the first layer; (b) thermal cycle curves of the midpoint of each track in the second layer

Fig. 11. Comparison between the simulated upper surface molten pool evolution and experimental scanning line morphology of pure tungsten samples formed by SEBM. (a) Scanning line morphology of the upper surface of tungsten samples; (b) simulation of the evolution of molten pools on the upper surface

Fig. 12. Two-layer molten pool profile crossing the plane A-A in Fig.8

Fig. 13. Molten pool sizes at the midpoint of each track for two layers varying with the number of scanning tracks