Page 62 - MSAM-1-4

Materials Science in Additive Manufacturing LPBF of Mg and its bio-applications

Table 4. Corrosion resistance of the LPBF‑manufactured Mg strength and surface hardness, and good plasticity. Zhang
and its alloys et al. prepared Mg-based amorphous alloys by rapid
[90]
cooling. The results show that the corrosion resistance
Material Soaking Degradation behaviors of the amorphous alloy is obviously better than that of
time
Mg [47] 1 day pH in SBF: ~10.5 the crystalline alloy with the same composition. Zberg
et al. also studied the degradation process of Mg-Zn-Ca
[91]
Mg-6Zn [74] 7 day Evolved H volume in amorphous alloy as a biodegradable medical material
2
SBF: 32.2 mL/cm 2 and found that the corrosion resistance was significantly
ZK60 [41] 2 day H volume evolution rate in improved. Moreover, there was no obvious hydrogen
2
SBF: 0.006 mL/cm /h
2
ZK60-0.2Cu [92] 7 day pH in SBF: 9.49 evolution reaction during the degradation process.
CR in SBF: ~1.01 mm/year 3.3. Biological behavior
ZK60-BG [51] 7 day CR in SBF: 0.51 mm/year Medical implants need to have excellent biocompatibility
WE43 [45] 20 h CR in 0.1 M NaCl solution: 5 [93]
mm/year to avoid toxic effects on the human body . At present,
Amorphous Mg-Zn-Ca [88] / CR for current density in there are little reports on the biocompatibility of additively
SBF: 0.35 mm/year manufactured metal implants. The biocompatibility
SBF and CR represent simulated body fluid and corrosion rate, evaluation of Mg-based degradable metals for AM is still
respectively at the cellular and in vitro levels. The factors affecting
biocompatibility are mainly its chemical properties and
[94]
were effectively refined. Li et al. reported that Zn degradation products. Ouyang et al. reported that
[84]
addition refined the grain size to promote the formation of the large pores of the metal scaffolds were favorable for
passivation films on the substrate, thus providing effective nutrient supply, while the small pores were favorable for
protection for the Mg substrate. Luo et al. found that the cell growth.
[85]
alloying of rare earths significantly reduced the proportion Bioactive ceramics have excellent osteoconductive and
of β phase and promoted the formation of γ phase with a bioactivity. Rojaee et al. synthesized hydroxyapatite
[95]
larger active potential, which reduced the micro-galvanic coating on AZ91 alloy by electrophoretic deposition
corrosion with the Mg matrix. In addition, the introduction process, and its corrosion resistance and biological
of alloying elements improves the stability or structural properties were significantly improved. Razavi et al.
[62]
integrity of corrosion product layer on the substrate surface prepared nanostructured magnesite and diopside coatings
with strong protective ability. Leleu et al. introduced by electrophoretic deposition, which also improved the
[86]
alloying element Y into Mg alloys, which formed a dense corrosion resistance and bioactivity of magnesium alloys.
surface film after immersion in chloride rinsing solution Tian et al. used ammonium bicarbonate particles as a
[96]
and played a significant protective role. Willbold et al. pore-forming agent, and then prepared porous Mg scaffolds
[87]
added rare earth elements (La, Nd, and Ce) to Mg matrix by powder metallurgy process, and coated bioactive
and found that the rare earth oxides formed on the surface ceramics on the surface of Mg scaffolds in a low vacuum
of the Mg alloy to improve the passivation ability of the environment. The results showed that the coated Mg
surface film. Notably, most of rare earth elements have low scaffolds have obvious biological activity, and the coating
solid solubility in Mg matrix, thus excessive addition of effectively delays the degradation rate of magnesium stents
rare earths can cause galvanic corrosion to accelerate the and improves its mechanical integrity.
degradation and bring about cytotoxicity problems.
Rahimi et al. successfully prepared chitosan and
[97]
3.2.3. Amorphous alloy nanofiber coatings on the surface of AZ31 Mg alloy by
Amorphous alloy, also known as metallic glass, is a non- anodizing combined with electrospinning. The coating
equilibrium metal material with excellent corrosion not only has good corrosion resistance but also has good
resistance. Wang et al. prepared Mg 60Zn 33Ca 7 cell adhesion and proliferation ability. However, due to the
[88]
amorphous alloy by melt spin quenching method. The large differences in physical properties and mismatched
corrosion potential shifts positively and the corrosion degradation rates, the surface coating is easy to crack
current density decreases, thus showing excellent or even falls off after implantation, making it difficult to
[98]
corrosion resistance. Chen et al. reported the research achieve long-term effective protection. Dutta et al.
[89]
on Mg-based amorphous alloys, which were processed by prepared Mg/bioglass composites by microwave sintering,
traditional copper mold casting process. The amorphous and the results showed that the corrosion resistance,
alloys possess great glass forming ability, high fracture mechanical properties, and biocompatibility were

Volume 1 Issue 4 (2022) 11 https://doi.org/10.18063/msam.v1i4.24