Page 91 - IJB-7-1

Xie, et al.

Figure 12. X-ray photoelectron spectroscopy analysis of corrosion products on SLMed ZK30-0.2Cu-0.8Mn.

if the Mn content was less than 0.8wt%, due to the content as described above. As a consequence, for SLMed
rapid solidification by the SLM processing and formed ZK30-0.2Cu-xMn, the influence of grain refinement and
supersaturated solid solutions. In contrast, a Mn content the relatively protective manganese oxide layer on the
>0.8 wt% resulted in the formation of a small amount of increase of the biodegradation resistance counteracted the
Mn phase, which could not dissolve in the Mg matrix and influence of the undissolved Mn phase on the decrease
precipitated after the rapid solidification. The precipitated of biodegradation resistance; therefore, SLMed ZK30-
Mn phase served as a cathode and the Mg matrix as 0.2Cu-0.8Mn has the lowest biodegradation rate.
anode formed a galvanic couple, which increased the
biodegradation rate. Consequently, the biodegradation 5. Conclusion
rate first decreased, with Mn content increased and Novel antibacterial ZK30-0.2Cu-xMn alloys with fine
reached a minimum while Mn content was 0.8 wt% and equiaxed grains were successfully fabricated by SLM.
then increased with the Mn content. Furthermore, the Alloying with Mn has an evident influence on grain
precipitated Mn phase formed a weak interface with size, hardness, and biodegradation rate of SLMed ZK30-
the adjacent Mg where the cracks were easily initiated.
Figure 7D and 7E shows some microcracks on the 0.2Cu-xMn alloys. Alloying with Mn decreases the grain
size and produces a relatively protective manganese oxide
corroded surfaces of SLMed ZK30-0.2Cu-1.2Mn and
SLMed ZK30-0.2Cu-1.6Mn, which were generated due film, which significantly decreases the biodegradation
to the dehydration of the corrosion product layer by rate of SLMed ZK30-0.2Cu-xMn alloys. Undissolved Mn
drying . The existence of microcracks caused the matrix increases the biodegradation rate of SLMed ZK30-0.2Cu-
[39]
to contact the SBF directly and accelerated the corrosion. xMn. The optimum Mn content is 0.8 wt.%. SLMed
The microcracks of the corroded surfaces became larger ZK30-0.2Cu-0.8Mn has the lowest biodegradation rate.
and deeper when Mn content increased from 1.2 wt% to SLMed ZK30-0.2Cu-0.8Mn exhibits strong antibacterial
1.6 wt%, accompanied by an increased biodegradation ability and good cytocompatibility, indicating their future
rate. Even so, for SLMed ZK30-0.2Cu-1.6Mn, some local prospects for bone implants.
areas presented microcracks, while some other areas were Conflict of interest
still covered by an integrated compact surface corrosion
layer (Figure 7E), which was formed due to the Mn There are no conflicts of interest to declare.

International Journal of Bioprinting (2021)–Volume 7, Issue 1 87