Research Progress on the Mechanical Properties of the Biomedical Titanium Alloy Porous Structures Fabricated by 3D Printing Technique
LI Shujun(), HOU Wentao, HAO Yulin, YANG Rui()
Shi -changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
Cite this article:
LI Shujun, HOU Wentao, HAO Yulin, YANG Rui. Research Progress on the Mechanical Properties of the Biomedical Titanium Alloy Porous Structures Fabricated by 3D Printing Technique. Acta Metall Sin, 2023, 59(4): 478-488.
Porous titanium alloys have been used for biomedical implants owing to their low-modulus matching with that of human bones and interconnecting pores with suitable size, which facilitates bone in-growth and satisfies the requirement of a successful implant. Recently, additive manufacturing (3D printing) has emerged as an excellent technology for manufacturing porous implants with accurate designed pore parameters and overcoming processing difficulties caused by high melting temperatures of metals. In this paper, the microstructure and mechanical properties of porous Ti-6Al-4V, commercial pure titanium (CP-Ti), and low-modulus Ti2448 alloys produced by 3D printing, obtained mainly by the authors' group, are reviewed. For Ti-6Al-4V, its fatigue properties are affected by the type of mesh struts and post processing. The better fatigue life of CP-Ti compared to that of Ti-6Al-4V derives from its superior ductility and the strain hardening effect caused by deformation twins. The excellent fatigue life of the low-modulus Ti2448 alloy results from its superelasticity and the high toughness, which increases the crack nucleation life and fatigue crack propagation life, respectively. Future directions of corrosion-fatigue properties of materials in complex physiological environments, surface biological functionalization, and porous material of new metallic alloy systems are discussed.
Fund: National Natural Science Foundation of China(51871220);National Natural Science Foundation of China(U2241245);Key Research Program of Frontier Sciences, Chinese Academy of Sciences(QYZDJ-SSW-JSC031)
Corresponding Authors:
LI Shujun, professor, Tel: (024)83978841, E-mail: shjli@imr.ac.cn;YANG Rui, professor, Tel: (024)23971512, E-mail: ryang@imr.ac.cn
Fig.1 OM image (a), XRD spectrum (b), bright field TEM image (c), dark field TEM images (d, e), and SAED pattern (f) of Ti-6Al-4V mesh struts[11]
Fig.2 Young's modulus of the Ti-6Al-4V meshes with different cell shapes (in which dynamic elastic modulus and static elastic modulus are marked with open and solid symbols, respectively) (a) and compressive strength of the Ti-6Al-4V meshes (b)[13]
Fig.3 Stress-strain curves of the Ti-6Al-4V reticula-ted meshes with different rhombic dodecahedron unit cells (a), the unit cell designed by the Materialize software (b), unit cells designed to increase the bending component of the load applied on the struts (c, d)[13] (P is the load applied to a strut (EF). P1 and P2 are two components of P along the bending and buckling deformation directions)
Fig.4 Maximum stress-fatigue life (S-N) curves of the Ti-6Al-4V mesh arrays with different densities (a) and plots of relative compressive fatigue strength versus relative density (b)[22] (σcomf—compressive fatigue strength of Ti-6Al-4V mesh arrays, σ0—compressive strength of Ti-6Al-4V, ρ—density of Ti-6Al-4V mesh arrays, ρ0—density of Ti-6Al-4V)
Fig.5 Typical variation of accumulated strain with cycle number of the Ti-6Al-4V graded mesh (Insets schematically show the crack initiation and propagation in different constituents during cyclic deformation) (a) and X-ray tomography (XRT) of the graded meshes after being stopped at different stages of cycling shown in Fig.5a (b)[30] (dε1 / dN, dε2 / dN, and dε3 / dN are the cyclic ratcheting rates of graded mesh at different stages during cyclic deformation)
Fig.6 Metallographs of as-fabricated Ti-6Al-4V mesh struts (a), and annealed at 750oC (b) and 950oC (c) for 1 h followed by furnace cooling to room temperature[21]
Fig.7 Compressive engineering stress-strain curves (Inset shows the whole stress-strain curves ) (a) and S-N curves (b) of the as-fabricated and annealed SEBM Ti-6Al-4V meshes[21] (SEBM—selective electron beam melting)
Fig.8 Tensile curves of 3D printed commercial pure titanium (CP-Ti) and Ti-6Al-4V solid cylinders with a diameter of 1.2 mm (a), compressive stress-strain curves of porous CP-Ti and Ti-6Al-4V samples with topology-optimized and rhombic dodecahedron structures (b), and fatigue S-N curves of topology-optimized and rhombic dodecahedron CP-Ti specimens (c)[36]
Fig.9 Morphology of the SEBM Ti2448 porous specimen (a), the single unit of 3D rhombic dodecahedron modeling (b), the surface morphology of hole beam (c), the microstructure of the strut (d), and XRD spectrum of the specimen with the single β phase (e)[42]
Fig.10 Typical compressive stress-strain curves (a), the elastic modulus (b) and the superelasticity (c) for SEBM Ti2448 specimens with different porosities[42] (Inset in Fig.10c shows enlarged curves of retangle area)
Fig.11 S-N curves (a) and normalized S-N curves (b) of the porous Ti2448 and Ti-6Al-4V specimens with different porosities, and the relationship of elastic modulus and the fatigue strength for the SEBM porous Ti2448 and Ti-6Al-4V specimens (c)[42]
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