Fig. 1. Surface topography and particle size distribution of Ti-6Al-4V powder. (a) Surface topography; (b) particle size distribution

Fig. 2. Schematic illustration of scanning strategies

Fig. 3. Porous structure stacked by cells with gradient porosity

Fig. 4. Macro morphology of samples printed with SLM

Fig. 5. Yield stress and plastic strain in plastic stage

Fig. 6. Assembly and loading mode of gyroid scaffolds in 5% gradient porosity (45%－50%)

Fig. 7. Computational fluid dynamics (CFD) analysis model of gyroid scaffolds in 45% porosity with illustration of meshing and boundary conditions

Fig. 8. Mises stress and PEEQ of porous structure in uniform porosity (50%) at total strain of 16.7%. (a)－(b) Primitive scaffolds; (c)－(d) gyroid scaffolds

Fig. 9. Mises stress and PEEQ of porous structure in 5% gradient porosity (45%－50%) at total strain of 16.7%. (a)－(b) Primitive scaffolds; (c)－(d) gyroid scaffolds

Fig. 10. Mises stress and PEEQ of porous structure in 10% gradient porosity (40%－50%) at total strain of 16.7%. (a)－(b) Primitive scaffolds; (c)－(d) gyroid scaffolds

Fig. 11. CFD analysis results of powders inside primitive scaffolds in different porosity values. (a)－(b) 50% porosity；(c)－(d) 45% porosity; (e)－(f) 40% porosity

Fig. 12. CFD analysis results of powders inside gyroid scaffolds in different porosity values. (a)－(b) 50% porosity；(c)－(d) 45% porosity; (e)－(f) 40% porosity

Fig. 13. Surface topography of down and side surfaces of scaffolds with uniform porosity. (a)－(b) Primitive scaffolds；(c)－(d) gyroid scaffolds

Fig. 14. Through-hole diameter and minimum strut diameter of primitive and gyroid scaffolds in gradient porosity of 0% (uniform porosity)，5%, and 10%. (a) Through-hole diameter; (b) minimum strut diameter

Fig. 15. SEM image of primitive scaffold

Fig. 16. XRD patterns of primitive scaffold and powder

Fig. 17. Compressive stress-strain curves. (a) Primitive scaffolds; (b) gyroid scaffolds

Fig. 18. Actual and simulated compressive stress-strain curves of primitive scaffold with uniform porosity

Fig. 19. Compression failure modes of two scaffolds. (a)(d) Uniform porosity; (b)(e) 5% gradient porosity；(c)(f) 10% gradient porosity

Fig. 20. Mechanical properties of primitive and gyroid scaffolds. (a) Elastic modulus; (b) yield strength; (c) compressive strength

Fig. 21. Fracture morphologies of primitive and gyroids scaffolds at low magnification. (a)(d) Uniform porosity；(b)(e) 5% gradient porosity; (c)(f) 10% gradient porosity

Fig. 22. Fracture morphologies of primitive and gyroids scaffolds at high magnification. (a)(d) Uniform porosity；(b)(e) 5% gradient porosity; (c)(f) 10% gradient porosity