Page 462 - IJB-9-4

International Journal of Bioprinting β-Ti21S auxetic FGPs produced by laser powder bed fusion

Figure 3. Lateral and top scanning electron microscopy views showing the details of the auxetic functionally graded porous structures with θ = 15°.

Figure 4. Lateral and top scanning electron microscopy views showing the details of the auxetic functionally graded porous structures with θ = 25°.

considering the pore size. Indeed, an oversizing of 3% and the CAD and printed sample for all the different relative
11% is observed for relative density levels of 0.40 and 0.58, density levels, are reported.
respectively, and an undersizing of 5% for the high relative In general, a lower relative density leads to a lower pore
density level may be due to the too dense structure that
lost the auxetic geometry. The pore geometry of auxetic size and increased strut thickness. The overlap of CAD
structure changes since the opposite inclined struts come on the µ-CT image (Figure 6C, F, I, and Figure 7C, F, I)
in contact with each other. Excess of material on the highlights areas with excess of powder near the corners
connection between struts leads to a lower pore size with of the auxetic structure (grey particles indicated by a gray
respect to the CAD without affecting the strut thickness. arrow) and printed strut smaller than the one of the CAD
This point is discussed in detail in the section 3.3. (yellow arrows). In addition, no deviation of the strut
angles is observed by the superimposition of µ-CT image
3.2. 3D metrological characterization: µ-CT analysis to the CAD. This is an important issue that highlights the
Figures 6 and 7 show the µ-CT images of all auxetic FGPSs good quality of the printed sample without the need of
with θ = 15° and 25°, respectively. Details of the analyzed further thermal treatment to release the residual stress
pore size and strut thickness, as well as the overlap between due to LPBF and avoid geometrical distortions. The

Volume 9 Issue 4 (2023) 454 https://doi.org/10.18063/ijb.728