Fig. 1. Ti-6Al-4V powder particle size distribution

Fig. 2. Scan strategy of Zig-Zig

Fig. 3. Ti-6Al-4V alloy formed by SLM. (a) Fatigue specimen; (b) cylindrical drawing specimen

Fig. 4. Stress-strain curves of static tensile specimen before and after 840 ℃/2 h/AC heat treatment

Fig. 5. Fracture surface morphologies of samples after different heat treatments. (a) Untreated; (b) 840 ℃/2 h/AC

Fig. 6. Fatigue life of Ti-6Al-4V alloy under different treatments at a constant stress of 330 MPa

Fig. 7. Fracture surface morphologies of fatigue samples after different treatments. (a) As-built; (b) polished; (c) heated and polished

Fig. 8. Microstructure. (a) OM photo and SEM photo of the untreated sample; (b) OM photo and SEM photo of Ti-6Al-4V after 840 ℃/2 h/AC annealing treatment. In (a) and (b), the α' phase is light and the β phase is dark

Fig. 9. XRD patterns of Ti-6Al-4V samples fabricated by SLM

Fig. 10. Stiffness as a function of cycle number of fatigue life for as-built sample, polished sample and polished sample after heat treatment

Fig. 11. Surface defects of SLM specimen

Fig. 12. Fatigue fracture morphologies of directly formed fatigue specimens with different cycles of fatigue life. (a) Fatigue life is 23397 cycle; (b) fatigue life is 24118 cycle; (c) fatigue life is 24039 cycle; (d) fatigue life is 19934 cycle; (e) fatigue life is 26018 cycle

Fig. 13. Correspondence between initial fatigue cracking defect and fatigue life of polished sample and polished sample after heat treatment

Fig. 14. Three-dimensional morphologies of the scanning line at 180 W and poor overlap defects on the XOY plane. (a) Scanning line in the X direction; (b) scanning line in the Y direction; (c) poor overlap defects on the XOY plane