Fig. 1. Morphologies of experimental powders under scanning electron microscope. (a) TC4 spherical powders; (b) boron powders; (c) TC4/B mixed powders under low-power scanning electron microscope; (d) TC4/B mixed powder under high-power scanning electron microscope

Fig. 2. Dimension of formed specimen and standard smooth bar specimen for low-cycle fatigue test. (a) Laser melting deposited sample; (b) standard specimen for low-cycle fatigue test

Fig. 3. Low-cycle fatigue strain-life curves of solid solution-aged boron-modified TC4 titanium alloy deposited via laser melting

Fig. 4. Strain life curves of solid solution-aged boron-modified TC4 titanium alloy deposited via laser melting and annealed TC4 forging

Fig. 5. Microstructures of TC4 titanium alloys. (a) Annealed TC4 forging; (b) solid solution-aged boron-modified TC4 titanium alloy deposited via laser melting

Fig. 6. Schematics of crack propagation of two microstructures. (a) Basket microstructure; (b) two-state microstructure

Fig. 7. Hysteresis loops at different strain amplitudes and cyclic softening ratio as a function of strain amplitude. (a) Hysteresis loop at 0.45% strain amplitude; (b) hysteresis loop at 0.6% strain amplitude; (c) hysteresis loop at 0.7% strain amplitude; (d) hysteresis loop at 0.8% strain amplitude; (e) hysteresis loop at 1.0% strain amplitude; (f) cyclic softening ratio as a function of strain amplitude

Fig. 8. Variations of maximum stress and plastic strain amplitude with cycle numbers. (a) Variation of maximum stress with cycle numbers; (b) variation of plastic strain amplitude with cycle numbers

Fig. 9. Low-cycle fatigue fracture morphologies of solid solution-aged boron-modified TC4 titanium alloy obtained via laser melting deposition. (a) Overall morphology of fracture; (b) fatigue crack source area morphology

Fig. 10. Fracture morphologies of low-cycle fatigue crack growth zone. (a) Gradually wide fringe spacing; (b) secondary cracks

Fig. 11. Fracture morphologies of low-cycle fatigue specimens in the transient fracture zone. (a) Macromorphology of transient fracture zone; (b) dissociation steps under scanning electron microscope

Fig. 12. Fatigue fractures of normal and abnormal failure specimens. (a)(b) Normal specimens; (c)(d) abnormal failure specimens

Table 1. Main chemical composition of TC4 powders

Table 2. Laser melting deposition parameters of TC4 titanium alloy

Table 3. Measured room temperature low-cycle fatigue property of solid solution-aged boron-modified TC4 titanium alloy deposited via laser melting