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A continuous net-like eutectic structure enhances the corrosion resistance of Mg alloys
the eutectic α phase was enriched in Al. With addition of lowest Al content of 5.89 at.%, which was lower than that
0.25 wt% Ti, more Al-enriched eutectic α phase and less in AZ61 (6.42 at.%) and AZ61-1.0Ti (6.28 at.%). Their
β phase were observed. In AZ61-0.5Ti, the Al-enriched results indicated that the diffusivity of Al was increased
eutectic α phase continuously distributed and constructed with increasing Ti. Besides, Zn was detected in all of
a net-like structure, which was also proved by the EDS the AZ61-Ti alloys. Moreover, a small amount of Ti was
mapping results. Moreover, only a few β phase particles detected in the β phase of AZ61-1.0Ti.
were observed. With Ti further increasing to 0.75 and 1.0 The area fraction of Al-enriched α phase and β phase
wt%, the β phase particles were coarsened and increased, was measured by the Image-Pro Plus 6.0 software, with
which were enriched in Al and Ti, as revealed by EDS results displayed in Table 1. The area fraction of Al-
analysis. enriched eutectic α phase in AZ61 was 17.3%. With
The quantitative elemental compositions were obtained, Ti gradually increased to 0.5 wt%, the area fraction of
as shown in Figure 2B, in which point 1, point 4, and point eutectic α phase gradually increased to 42.0%, which
7 represented position in the vicinity of the Al-enriched indicated that the Al atoms in Mg solute were consumed
eutectic α phase, point 2, point 5, and point 8 represented to constitute more Al-enriched eutectic α phase. With Ti
the position in the β phase, and point 3, point 6, and point further increased to 1.0 wt%, the area fraction of eutectic
9 represented the position in the α-Mg grains, respectively. α phase was reduced to 27.8%. It was believed that excess
It could be seen that the Al contents dissolved in α-Mg Ti reacted with Al to form β phase, thus reducing the Al
grains were 2.92±0.74 wt.%. With Ti increasing to 0.5 content in eutectic.
wt% and 1.0 wt%, the Al contents were dissolved in α-Mg The optical microstructure and the calculated grain
grains gradually decreased to 1.93 ± 0.51 and 1.13 ± 0.46 sizes of the AZ61-Ti are presented in Figures 3A-F. The
at.%, respectively. Similarly, the Al content in β phase grain sizes for the AZ61, AZ61-0.25Ti, AZ61-0.5Ti,
was also decreased with increasing Ti content, which AZ61-0.75Ti, and AZ61-1.0Ti were 16.4 ± 2.3, 12.7 ±
was 20.46 at.% for AZ61, 10.29 at.% for AZ61-0.5Ti, 2.1, 10.4 ± 1.6, 9.5 ± 1.1, and 9.1 ± 0.8 µm, respectively,
and 9.08 at.% for AZ61-1.0Ti. However, the Al content indicating that Ti significantly refined the grain sizes.
in Al-enriched eutectic α phases showed a different trend. The XRD patterns indicated that α-Mg was a major
Al-enriched eutectic α phases in AZ61-0.5Ti exhibited the phase. Moreover, the β phase of AZ61, AZ61-0.25Ti, and

A

B

Figure 2. (A) Microstructure of AZ61-Ti observed under scanning electron microscope and the corresponding elemental distribution of Al;
red arrow indicates the eutectic α phase. (B) Energy dispersive spectroscopy results corresponding to particles in Figure 2A.

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