Fig. 1. Total fatigue strain of the Ti2448 meshes with 72.5% porosity under the applied cyclic stress of 6 MPa (a) and the effect of fatigue cycle on the stress-strain loops of the studied specimens (b) [27].

Fig. 2. Optical microstructures of the EBM Ti-6Al-4V foams with density of 0.37 (a) and 0.44 g/cm3 (b) and the meshes with density of 0.62 (c) and 1.68 g/cm3 (d) [48].

Fig. 3. SEM images of the EBM Ti-6Al-4V foam and the mesh with density of 0.44 (a) and 0.62 g/cm3 (b) respectively, where the arrows denote the measurement of thickness and length of the strut [48].

Fig. 4. S-N curves of the EBM Ti-6Al-4V meshes with different densities (a) and the plots of relative fatigue strength versus relative density (b) [35].

Fig. 5. Cubic, G7 and rhombic dodecahedron elements in the materialize software (a-c) and the corresponding Ti-6Al-4V prototype blocks fabricated by the EBM method (d-f), (g-i) are the schematics to depict the buckling and bending vectors of the load applied on the studied cell struts. (j) S-N curve of the studied meshes with cubic, G7 and rhombic dodecahedron structures [67].

Fig. 6. Optical micrographs of EBM Ti-6Al-4V mesh struts under different conditions: (a) As-fabricated and annealed at (b) 750 °C, (c) 850 °C and (d) 950 °C for 1 h followed by furnace cooling to room temperature. (e) XRD patterns of the studied samples after different annealing. In (b)-(d), the α and β phases are bright and dark colors, respectively [71].

Fig. 7. Compressive engineering stress-strain (a) and S-N curves (b) of the as-fabricated and annealed EBM Ti-6Al-4V meshes [71].

Fig. 8. (a) Typical variation of the accumulated strain against the number of cycles of the EBM graded Ti-6Al-4V mesh. (b) CT scan images of the graded meshes after being stopped at different stages of cycling shown in (a). Slices A, B, C and D are cross-section of the 2D X-ray tomography (XRT) located at G3, G2 and G1 part shown in the 3D morphology view of the samples, respectively. The numbers 0, 1, 2, 3, 4 indicate that the slice was examined respectively, at various stages of cyclic loading. A-0, B-0, C-0, D-0 are original morphologies of slices A, B, C and D before fatigue tests, respectively. Comparing with the original morphologies, the colored dash cycles indicate the cracks detected in the mesh struts after a certain number of cycles. The schematic figures inserted in (a) summarize crack initiation and propagation in G1, G2 and G3 mesh, respectively with cycles based on the XRT observation in (b) [39].

Fig. 9. Schematic drawings of the graded mesh with n constituents (1, 2, 3, …, M, …, n) [39].

Fig. 10. Comparison of the fatigue strength and the absorption of the graded meshes with the uniform reticulated EBM Ti-6Al-4V meshes and metallic cellular structures. The numbers in parentheses indicate the densities of the cellular structures [39].

Fig. 11. Examples of porous Ti-6Al-4V alloy implants fabricated by electron beam melting.