Page 60 - IJB-5-2

A continuous net-like eutectic structure enhances the corrosion resistance of Mg alloys
the AZ61-Ti extracts exhibited improved cell viability increase of Ti, the microhardness gradually increased to
compared with AZ61 as the cell density (number of cells) 90.1 ± 4.0 HV for AZ61-0.25Ti, 95.2 ± 3.4 HV for AZ61-
was enhanced. Specifically, AZ61-0.5Ti exhibited the 0.5Ti, 96.3 ± 3.1 HV for AZ61-0.75Ti, and 97.8 ± 4.3 HV
best cell viability. There were few apoptotic cells (red for AZ61-1.0Ti, respectively (Figure 9B).
fluorescence in the nuclei) in each group for all culture
periods. Moreover, cells exhibited similar shape after 4. Discussion
culturing for 24 h and 72 h. Clearly, AZ61-0.5Ti exhibited
improved biocompatibility as compared with AZ61. It was 4.1 Microstructure and Mechanical
believed that the enhanced corrosion resistance should Properties
be responsible for the improved biocompatibility . For
[26]
AZ61-0.5Ti, the enhanced corrosion resistance resulted in In the present study, the incorporation of moderate Ti
a reduced degradation rate, thus decreasing the corrosion induced the formation of continuous net-like eutectic
products, which might alleviate the cytotoxicity . α phase. It was believed that Ti, which had low solid
[27]
solubility in Mg, would be first rejected into the
3.4 Mechanical Properties interdendritic liquid phase during the solidification of the
[28]
The compressive strength and microhardness of AZ61- molten pool . From the perspective of thermodynamics,
Ti are displayed in Figure 9. AZ61 exhibited a relatively Ti in the interdendritic liquid would catch the Al atoms
low compressive strength of 110.4 ± 15.2 MPa. With Ti in Mg solute to form the second phase due to the high
[15]
gradually increasing to 0.5 wt%, the compressive strength affinity between Ti and Al . Thus, the diffusivity of Al
was gradually improved to 175.6±21.3 MPa. However, would be enhanced during the solidification, resulting in
with Ti content further increasing to 0.75 wt% and 1.0 an increased Al content near the eutectic location. With
wt%, the compressive strength was decreased to 145.3 ± the liquid phase cooling to the eutectic temperature and
30.9 MPa and 123.9 ± 34.7 MPa, respectively. AZ61 had the Al content close to eutectic composition, the eutectic
a relatively low microhardness of 84.8 ± 3.7 HV. With the reaction would occur to form the eutectic phases.

A B

C

Figure 7. (A) pH of the extracts; (B) Mg and Zn concentration in the extracts; (C) relative viability of MG63 cells culture in AZ61-Ti
extracts.

56 International Journal of Bioprinting (2019)–Volume 5, Issue 2