Biomedical Engineering Reference
In-Depth Information
The films were then stained with Hematoxylin and eosin. Histological images were
observed on an optical microscope.
2.7 Statistical analysis
A t-test was used to determine whether any significant differences existed between the
mean values of the cytotoxicity and animal tests of the experiment. The statistical
significance was defined as P < 0.05.
3. Results and discussion
3.1 Phase compositions and microstructures evolution of the as-cast Mg-Zn-Ca alloys
3.1.1 The effects of Zn content on phase compositions and microstructures of the
as-cast alloys
In this study, in order to investigated the effects of Zn and Ca on the phase compositions and
microstructures evolution of the as-cast Mg-Zn-Ca alloys, respectively, the initial content of Ca
design as 0 wt. % and then changed the content of Zn to study the effects of Zn on phase
compositions and microstructures. The chemical compositions of the Mg-xZn alloy obtained
by ICP-AES were listed in Table 1. The impurity contents of the Mg-x Zn alloy were very low
for better degradation properties and biocompatibility. X-ray diffraction (XRD) analyses were
used to investigate the existing intermetallic phases in the Mg-x Zn Ca alloys (Fig. 1). As
shown in Fig. 1, there was only α-Mg diffraction peaks phase in the Mg-1.0Zn alloy.
Diffraction peaks from the Mg 2 Zn phase was not detected. With the Zn concentration
increasing, MgZn phase's patterns were began to detect in Mg-5.0 Zn and Mg-6.0 Zn alloy.
Chemical composition (wt.%)
Materials
Al
Zn
Mn
Si
Fe
Mg
Mg-1.0Zn
0.023
0.976
0.058
0.031
0.004
Balance
Mg-2.0Zn
0.033
1.852
0.030
0.039
0.007
Balance
Mg-3.0Zn
0.029
2.732
0.022
0.036
0.007
Balance
Mg-4.0Zn
0.019
3.925
0.021
0.032
0.008
Balance
Mg-5.0Zn
0.027
5.223
0.031
0.034
0.009
Balance
Mg-6.0Zn
0.024
5.977
0.019
0.033
0.012
Balance
Table 1. Chemical compositions of the as-cast Mg-Zn alloy
The microstructures of the as-cast Mg-x Zn alloys were shown in Fig.2. Fig. 2(a) was taken
from Mg-1.0 Zn alloy, in which the microstructure consists of the α-Mg . The maximum
solubility of Zn in the magnesium was about 2 wt. % at room temperature in the
equilibrium state, when no more than 2 wt. % Zn was added, the Zn was solid solution in
Mg matrix. When the contents of Zn was more than 4 wt. % , the microstructure obviously
changed, there were more second phases precipitated and the morphogenesis of second
phases were small particle. As shown in Fig.2 (f), with the increasing of Zn content, lamellar
eutectic appears in the as-cast microstructure. The eutectic structures were very coarse and
mostly distributed in the grain boundary and less in the areas of inter-dendrite,
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