Abstract
In the present study, cellular lattice structures for implant applications are reported for the first-time incorporating copper directly by in-situ alloying in the laser powder bed fusion process. The aim to incorporate 3 at.% Cu into Ti6Al4V(ELI) is selected for improved antibacterial properties while maintaining appropriate mechanical properties. Previously, topologically optimized Ti6Al4V(ELI) lattice structures were successfully designed, manufactured and studied for implant applications. The development of a new alloy produced by in-situ alloying of elemental powder mixture of Ti6Al4V(ELI) and pure Cu powders was used here for the production of identical lattice structures with improved antibacterial properties. One of the same as-designed CAD models was used for the manufacturing of these lattices compared to previous work on pure Ti6Al4V(ELI) lattices, making direct comparison of mechanical properties possible. Similar manufacturability highlights the applicability of this alloying technique to other lattice designs. Microstructural characterization was performed by optical and electron microscopies, as well as microCT. Mechanical characterization was performed by means of compression tests and hardness measurements. Results showed that in-situ alloying with copper leads to the formation of localized Cu-rich regions, refinement of martensitic phase and the formation of CuTi2 intermetallic precipitates, which increased the hardness and strength of the material. Deviations in wall thickness between the as-designed and as-manufactured lattices led to anisotropy of the mechanical properties of the lattices. Higher compressive strength values were obtained when thicker walls were oriented along the loading direction. Nevertheless, alloying with Cu had a higher impact on the compressive strength of lattice structure than the wall thickness deviations. The direct in-situ alloying of copper in Ti6Al4V(ELI) is a promising route for direct manufacturing of antibacterial implants.
Highlights
Laser powder bed fusion (L-PBF) is an additive manufacturing pro cess that allows freedom in design, which is beneficial for the manufacturing of complex geometries, e.g. cellular lattice structures (CLS)
The same trend was found in our previous work of Ti6Al4V (ELI) CLS, wall thickness deviations were lower compared to Ti6Al4V(ELI)-3 at.% Cu CLS
The present study is focused on the microstructural and mechanical characterization of in-situ alloyed Ti6Al4V(ELI)- 3 at.% Cu CLS designed for implant applications
Summary
Laser powder bed fusion (L-PBF) is an additive manufacturing pro cess that allows freedom in design, which is beneficial for the manufacturing of complex geometries, e.g. cellular lattice structures (CLS). Geometrical and structural factors of CLS such as connectivity, pore size and relative density are important for the design of implant prostheses with suitable mechanical and biological properties (Maco nachie et al, 2019). Light-weight Ti6Al4V CLS allows the decrease in effective elastic modulus closer to the human bone, being beneficial by decreasing/avoiding stress shielding and promoting bone in-growth (Yanez et al, 2016; Onal et al, 2018). Different approaches for CLS design, such as CAD-based and image-based, have arisen to merge the structural and mechanical needs for implant prostheses with desired relative densi ty/porosity, as well as effective elastic modulus (Xu et al, 2019; Vilar dell et al, 2019). Theoretical and experimental analyses demonstrated the possibility to vary such architectural features without dramatically altering the mechanical performance of the structure (Maietta et al, 2019)
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