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Mechanism for corrosion protection of β-TCP reinforced ZK60 via laser rapid solidification

matrix. Meanwhile, the conventional processes, also 2. Materials and Methods
including powder metallurgy [13] , are difficult to prepare
porous Mg alloys with complex shapes. 2.1 Materials
In the present study, laser melting technology is β-TCP powder with a size of approximately 200 nm
proposed to overcome the agglomeration of incorporated (Figure 1A) was obtained from Kunshan Chinese
bioceramic. Laser melting technology is a typical rapid Technology New Materials Co. Ltd., China. Spherical
solidification which has an extremely high cooling rate ZK60 powder was purchased from Tangshan Weihao
5
over 10 K/s, which allows the solidification can be Materials Co. Ltd., China. The chemical composition
completed in an extremely short period of time [14] . In was as follows: 6.63 wt. % of Zn, 0.56 wt. % of Zr and
this condition, the ceramic particles which orig i nal ly balanced Mg. The size of the ZK60 powder was <50 μm
(Figure 1B). The ZK60 alloy powder was composited
uniformly dispersed in the liquid pool cannot ag glom er- with 0, 4, 8 and 12 wt. % of β-TCP powder, respectively,
ate in such a short time, thus homogenously distributing followed by ball milling under a protective gas (0.3
in the matrix. Meanwhile, the rapid solidification is able vol. % SF 6 and 99.7 vol. % CO ) at a rotation speed of
2
to refine the microstructure, which is also beneficial 150 rpm. After ball milling for 2 h, the small β-TCP
to enhance the corrosion re sis tance of Mg alloys [15] . particles uniformly adhered to the surface of large ZK60
Another study on Ti–TiB com posites further confirmed particles (Figure 1C and Figure 1D). The homogeneity
that laser melting was an ef fec tive method that could of the powder could improve the flowability and allow
for improved packing of powder, thus reducing the
produce almost fully dense composites with bioceramic formation of defects .
[19]
enforcement [16] . On the other hand, laser melting tech-
[17]
no lo gy can fabricate porous Mg alloys . To the best of 2.2 Fabrication of the Composites
our best knowledge, there are few publications studying The ZK60/xβ-TCP (x = 0, 4, 8 and 12 wt. %) composites
on the corrosion behavior of laser rapidly solidified were fabricated by a home-made laser melting system,
biocaremic reinforced Mg alloys. which comprised of a powder delivery device, a three-
[17]
In this study, β-TCP was introduced to ZK60 to dimensional motion platform and a fiber laser . In the
improve its degradation behavior via laser rapid so- laser melting process, a high energy laser beam scanned
lid i fi cation. β-TCP had good bioactivity as well as the powder layer, forming a solid layer. Then, the formed
good wettability with the Mg alloy [18] . ZK60/β-TCP solid layer was covered with a new layer of powder. The
cycle continued before the samples (8×8×8 mm ) were
3
composites with different contents of β-TCP (0–12 wt. achieved. The samples were fabricated at a laser power
%) were prepared. And the microstructure features, of 80 W, a scanning rate of 300 mm·s and a layer
-1
degradation behavior and mechanical properties were thickness of 0.1 mm. All procedures were performed
investigated. under a protective argon atmosphere.
A B

C D

Figure 1. Original powders: (A) β-TCP powder; (B) ZK60 powder; (C) ZK60/8β-TCP (wt. %)
mixed powder; and (D) the surface on ZK60 particle in mixed powder.

2 International Journal of Bioprinting (2018)–Volume 4, Issue 1