Enhanced Plasticity and Corrosion Resistance in Mg-Zn-Ca-Cu Amorphous Alloy Composite via Plasma Electrolytic Oxidation Treatment

Round 1

Reviewer 1 Report

The authors provide a paper dealing with the plasma electrolytic oxidation of Mg-Zn-Ca-Cu. The paper can be of interest for Metals, however MAJOR revisions are requested.

• The authors must comment more on the mechanical properties of the amorphous alloy. This is a very important topic in view of the applicability of amorphous alloys. Specifically, these materials are known to be quite brittle, while interesting mechanical size effects are found for the case of thin films. The authors must refer to the following papers doi.org/10.1016/j.actamat.2021.116955 and doi.org/10.1021/acs.nanolett.0c00869 reporting some example of large mechanical properties while showing different applicability. Moreover, the authors are invited to comment on the mechanical properties of their samples and discuss more what is the physical origin of the stress-strain curve in Fig. 5a. Is it due to the microstructural features of the composite?
• Connecting to the previous point the authors must be aware that there is the possibility to estimate the fracture toughness of the a metallic glasses by measuring the size of the amorphous veins and corrugations as the ones in Fig. 5c, as reported in doi.org/10.1016/j.scriptamat.2014.06.011. This can be a valuable information to add to the paper.
• The authors must provide a better discussion of the XRD as a matter of facts and amorphous halo (band) is not visible in fig. 1b although an amorphous segregation is present as well.
• The authors can explain in a better way what is the origin of the atomic segregation in Fig 2 especially at the grain boundaries. Is this an effect of the composition? How does this is related with the synthesis route?
• The title can be improved making it sounds better in English.

Author Response

Dear Editors and Reviewers,

I am very pleased to resubmit the above-mentioned manuscript for your further consideration for publication as a regular article in Journal of Metals. We greatly appreciate the reviewers’ constructive comments and suggestions. Taking into account the reviewers’ comments, we have carefully revised the manuscript to improve its technical quality and presentation.

The following is a point-to-point response to the reviewer’ comments, and corrections are highlighted in red in the revised manuscript. We hope that the revisions in the manuscript will be sufficient to make our manuscript suitable for publication in Journal of Metals. I am really appreciated for your time and consideration.

Author Response File: Author Response.pdf

Reviewer 2 Report

Strengths

The authors have shows a dendrite-reinforced Mg-based amorphous alloy composite was prepared through in-situ precipitation strategy by using copper-mould injection casting. The results of XRD, SEM and HRTEM demonstrated that the composite material consists of α-Mg solid solution dendrites and glassy matrix. After PEO treatment, the composite exhibits an enhanced average plastic strain of 9.4% and a high fracture strength of 640 MPa, together with significant strain-hardening behavior. The improvement of plasticity may attribute to the in-situ formed coating which can not only serve as propagation barrier for shear bands, but also can introduce nucleation sites for the bands resulting from stress mismatch and compositional heterogeneity. The corrosion density in the SBF solution decreases by three orders comparing with bare composite. The present study provides a fundamental basis for developing high performance biodegradable Mg alloys.

Weakness 

1. It's not clear what's depicted in Figure 2d?
2. There is no reference to Table 1 in the text.
3. The reference contains only 1 link of the authors. Refresh the reference.

 

Author Response

Dear Editors and Reviewers,

I am very pleased to resubmit the above-mentioned manuscript for your further consideration for publication as a regular article in Journal of Metals. We greatly appreciate the reviewers’ constructive comments and suggestions. Taking into account the reviewers’ comments, we have carefully revised the manuscript to improve its technical quality and presentation.

The following is a point-to-point response to the reviewer’ comments, and corrections are highlighted in red in the revised manuscript. We hope that the revisions in the manuscript will be sufficient to make our manuscript suitable for publication in Journal of Metals. I am really appreciated for your time and consideration.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

The manuscript focuses on fabrication of biocompatible Mg-based alloy. First, the Mg based alloy contained antibacterial copper has been synthesized and then, the alloy was treated using plasma electrolytic oxidation (PEO).

The content of the manuscript is relevant to the scope of the journal. However, the motivation is not well specified. On the one hand authors aim is to synthesize Mg alloy with anti-corrosive coating. Then, if the aim is evaluation of corrosion, EIS must be added. On the other hand, authors describe possible application of the alloy in implantation. Then, tests related to biocompatibility should be performed. I would like to ask to clarify this point.

Additionally, here is my specific comments:

1. Please provide the parameters of the XRD analysis (current, voltage, range, scanning rate, etc.). Are bulk and surface were analyzed using the same geometry in XRD? What geometry has been applied?
2. Specify in Materials and Methods what mechanical parameters were examined.
3. You have confused me, in Materials and Methods you have mentioned radius of the rod of 1 mm, while in Results and Discussion the radius of the rod was 2 mm. Please explain.
4. Why did you not detect Zn in XRD pattern in Fig.1? According to your investigations, it has 8.3 wt.%, it must be detected by XRD. Please run again XRD measurement and show which new phases did you find.
5. You have detected a plane (102) in HR-TEM, does it fit the analytical peak around 37 deg in XRD pattern shown in Fig. 1?
6. A very low intensity of the MgO phase is detected in Fig. 3. It can be referred to the formation of amorphous oxide coating. Thus, probably anodizing process was applied in the work and not PEO processing because PEO usually led to formation of crystalline phase. Please explain the obtained results.
7. Fig 3c caption is not appropriate. XRD is used for the crystalline materials and not amorphous. Moreover, I can’t detect any halo referred to the amorphous phase. Please re-write
8. Two XRD patterns have a same analytical peak around 37 deg. However, in Fig. 4b you have detected (100) plane which differs from the (102) plane shown in Fig. 2. How do you explain different HR-TEM images and almost the same XRD patterns?
9. In Fig. 3a the thickness of the coating is 10 microns. Then, you have shown a change in mechanical properties. Do you believe that that thin layer affects mechanical performance of the alloy? Did you reproduce the mechanical properties tests?
10. Where the thickness of 32.4 microns is found (Table 2)? It looks like 10 microns only in Fig. 3a.
11. Several tests must be done to show the results in Table 2. Standard deviation must be added.
12. You have described the coating contained of two sublayer, outer and inner. Electron microscope image of these observations must be added.

Author Response

Dear Editors and Reviewers,

I am very pleased to resubmit the above-mentioned manuscript for your further consideration for publication as a regular article in Journal of Metals. We greatly appreciate the reviewers’ constructive comments and suggestions. Taking into account the reviewers’ comments, we have carefully revised the manuscript to improve its technical quality and presentation.

The following is a point-to-point response to the reviewer’ comments, and corrections are highlighted in red in the revised manuscript. We hope that the revisions in the manuscript will be sufficient to make our manuscript suitable for publication in Journal of Metals. I am really appreciated for your time and consideration.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

-

Reviewer 3 Report

Authors considered all my comments.