Effect of Ag and Cu Content on the Properties of Zn-Ag-Cu-0.05Mg Alloys
and Carlos González-Rivera *Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe design and results in this study is reasonable. However, there are also some mistakes or doubts that should be solved. Here are some proposed suggestions:
1. In this study, the authors adjust the content of Ag and Cu to regulate the microstructures and properties of alloys. However, it should be stated why the author selected the Mg content as 0.05 wt.%.
2. In page 2, paragraph 2, the sentence “After being aged at room temperature for eight months, its mechanical properties increased by about 10%, which implies good anti-aging ability.” Actually, the aging problems for Zn alloys usually leads to its lower elongation after storage at room temperature for certain periods. This problem should be explained clearly.
3. For the introduction section, the chapter is not well organized, and it should be reorganized.
4. In section “2.3. Mechanical Properties Testing”, the detailed information on the tensile specimens (such as gauge length, cross section areas and etc.) should be added.
5. In section “2.5. Antibacterial Test”, why was the box incubated at 35 ℃. Typically, the box used for measuring antibacterial behavior should be incubated at 37 ℃ for about 24 h.
6. In section “2.6. Cytotoxicity Tests”, the authors state that “The cytotoxicity of the alloy with the highest content of alloying elements, alloy A4, was evaluated, assuming that the results obtained with this alloy can represent the rest of the experimental alloys.” It is curious to know how can the alloy A4 can represent the rest of the experimental alloys. In my opinion, the cytotoxicity evaluation on other alloys should also be conducted.
7. Some obvious mistakes should be avoided in this manuscript.
For example, in section “2.6. Cytotoxicity Tests”, line 201, “minimal essential medium (EMEM) with 10% FBS at 37 o C and 5% CO2 until they reached”. The subheadings are in the wrong order, eg. there is repetitive 3.3 but no 3.4 and 4.
8. In addition, the seeded cell amount in 96 well plates are 20000 cells/well. In my opinion, the cell density is too high.
9. In figure 7, it seems that the XRD patterns of AgZn4 is the same with CuZn4, please explain it clearly.
10. The corrosion potential difference between (Ag, Cu)Zn4 and Zn matrix should be discussed. Besides, the distribution and amount of (Ag, Cu)Zn4 may play a significant role on the corrosion behavior of Zn alloys. The increase of (Ag, Cu)Zn4 phases may also protect the corrosion of Zn matrix.
11. In my opinion, the control group should be added in Fig. 9.
12. Ag element has also been added in biodegradable Mg alloys, which influences mechanical and corrosion properties. The related reference “Effect of Ag addition on microstructure, mechanical and corrosion properties of Mg-Nd-Zn-Zr alloy for orthopedic application, Acta Metallurgica Sinica (English Letters), 2023, 36: 295-309” is recommended to cite.
Author Response
Answer to Reviewer 1
All the authors of this work thank the reviewer for his time and the detailed and professional nature of his review and suggestions that have allowed us to substantially improve the article, as can be seen in the revised version that we attach.
The design and results in this study is reasonable. However, there are also some mistakes or doubts that should be solved. Here are some proposed suggestions:
- In this study, the authors adjust the content of Ag and Cu to regulate the microstructures and properties of alloys. However, it should be stated why the author selected the Mg content as 0.05 wt.%.
Reply: Please see response to your comment 3 below
- In page 2, paragraph 2, the sentence “After being aged at room temperature for eight months, its mechanical properties increased by about 10%, which implies good anti-aging ability.” Actually, the aging problems for Zn alloys usually leads to its lower elongation after storage at room temperature for certain periods. This problem should be explained clearly.
Reply: Please see response to your comment 3 below
- For the introduction section, the chapter is not well organized, and it should be reorganized.
Reply: We rewrote an important part of the introduction to improve it based on your suggestions and comments, to include the reasons behind the selection of the 0.05% Mg content for the microalloying and also to clearly explain the aging problem, the difference in its manifestations in the mechanical properties presented by the Zn-1.5Cu-1.5Ag alloy of Chen et al. contrasted with the marked reduction in elongation, from 29.3 to 12.5%, presented by the Zn-0.08%Mg alloy after nine days of storage at room temperature reported by Jin et. Al.[25]
We also link to this discussion the mitigation of this problem reported by Ardakani et al.[26] and K. Cheng et al.[24] in the case of Zn-Mg micro alloys (<0.1wt% Mg) as a result of the presence of Cu and Ag as alloying agents. These elements act by delaying the diffusion of Mg in the Zn matrix, its arrival at the grain boundaries, and thus significantly delaying the formation of Mg2Zn11 precipitates responsible for the loss of ductility during aging.
To this end, we moved the paragraph that originally referred to the work of Chen et. al. and the anti-aging ability that you mentioned in point 2 of your observations and moved this paragraph to line 93, page 2, of the revised version, and it is from here that we made the improvements mentioned above, addressing points 1, 2, and 3 of your review, with the improvements included from line 95, page 2, to line 148 of page 3 in the revised version.
- In section “2.3. Mechanical Properties Testing”, the detailed information on the tensile specimens (such as gauge length, cross section areas and etc.) should be added.
Reply: In the revised version we included that information
- In section “2.5. Antibacterial Test”, why was the box incubated at 35 ℃. Typically, the box used for measuring antibacterial behavior should be incubated at 37 ℃ for about 24 h.
Reply: It was a typo, the tests were carried out at 37oC for 24 hours. We corrected this issue in the revised version, line 217 page 5 of the revised version
- In section “2.6. Cytotoxicity Tests”, the authors state that “The cytotoxicity of the alloy with the highest content of alloying elements, alloy A4, was evaluated, assuming that the results obtained with this alloy can represent the rest of the experimental alloys.” It is curious to know how can the alloy A4 can represent the rest of the experimental alloys. In my opinion, the cytotoxicity evaluation on other alloys should also be conducted.
The assumption is based on the analysis of the corrosion rate results of the alloys under study, and the results of cytotoxicity reported by Cheng et al. which support the following reasoning:
If the highest corrosion rate occurs in the alloy with the highest alloying content,
A greater quantity of alloying agents dissolves more quickly, and this alloy will release the constituent alloying metal ions in greater quantities and more quickly.
If these alloying element ions present cytotoxicity, this cytotoxicity will be more easily detectable in alloy A4.
Chen et al. [22] found that the Zn1.5Ag1.5Cu alloy exhibited superior cytotoxicity to that shown by Zn, as seen in Figure 14 of his paper.
- Some obvious mistakes should be avoided in this manuscript. For example, in section “2.6. Cytotoxicity Tests”, line 201, “minimalessential medium (EMEM) with 10% FBS at 37 o C and 5% CO2 until they reached”. The subheadings are in the wrong order, eg. there is repetitive 3.3 but no 3.4 and 4.
Reply: We carefully reviewed all errors and typos present in the original version, and identified, and corrected these errors to write the revised version.
- In addition, the seeded cell amount in 96 well plates are 20000 cells/well. In my opinion, the cell density is too high.
Reply: The cytotoxicity tests were carried out according to ISO 10993-5:20091 as indicated in the original version of the article. We are not able to repeat these tests because they were carried out at the UNIPREC of the UNAM and were very expensive despite the considerable and exceptional discount they gave us for belonging to the same institution and considering the low budget of our project.
- In figure 7, it seems that the XRD patterns of AgZn4 is the same with CuZn4, please explain it clearly.
Reply: The ternary phase (Ag, Cu)Zn4 is formed by a mixture of AgZn3 and CuZn4, so the peaks of these three microconstituents present some similar and/or overlapping characteristic diffraction peaks.
- The corrosion potential difference between (Ag, Cu)Zn4 and Zn matrix should be discussed. Besides, the distribution and amount of (Ag, Cu)Zn4 may play a significant role on the corrosion behavior of Zn alloys. The increase of (Ag, Cu)Zn4 phases may also protect the corrosion of Zn matrix.
We rewrote the corrosion results section and included the following paragraphs, included on page 12, from line 382 to 403
In the case of Zn-Ag-Cu base alloys, Chen et al. [22] reports for the Zn-1.5Ag-1.5Cu alloy that during the immersion test there is a weak passivation process indicating the formation of a poorly protective passive layer when the alloy is immersed in Hank solution. As the standard potential of the secondary phase is usually higher than that of the zinc matrix, when the film breaks, the zinc matrix in contact with the secondary phase dissolves by micro galvanic corrosion and that this corrosion behavior has been observed in many Zn-based alloy systems.
Niu et al.[19] studied the corrosion of Zn4 wt% Ag wt%1 Cu, Zn4 wt% Ag wt%1 Mn, and Zn4wt% Ag in Hanks solution and found that the alloys under study presented an initial dissolution process followed by the formation of a protective passive film of corrosion products. This film causes a decrease in the corrosion rate of the three alloys as the test time passed. They also found that the alloy that presented the most corrosion products was Zn4 wt% Ag wt%1 Mn, which presented the highest corrosion rate and the highest percentage of the second phase followed by the Zn4 wt% Ag wt%1 Cu alloy. Given the above, they concluded that the role of corrosion products may be twofold, causing on the one hand an accumulation of corrosion products that inhibited the process and on the other hand, with their disintegration, allowing the Zinc and the second phases form micro galvanic cells and promoting corrosion, which depended on the relative content and distribution of the second phases formed.
The results in Table 3 indicate that the increase in the second phase (Ag, Cu)Zn4 promoted the formation of more micro galvanic cells counteracting any possible protective effect of the corrosion products formed during the immersion test.
- In my opinion, the control group should be added in Fig. 9.
Reply: The results shown in this work were obtained to document a Mexican patent application, where the time factor, as we know, is pressing in terms of its viability. It is for this reason that we decided that since the A1 alloy did not meet the requirements for biomedical applications as expected due to its nature of control alloy, it would no longer be subjected to antibacterial tests against S. Aureus. We explain this reason in the article, presenting the same justification that we considered during the development of the pending patent.
- Ag element has also been added in biodegradable Mg alloys, which influences mechanical and corrosion properties. The related reference “Effect of Ag addition on microstructure, mechanical and corrosion properties of Mg-Nd-Zn-Zr alloy for orthopedic application, Acta Metallurgica Sinica (English Letters), 2023, 36:295-309” is recommended to cite.
Reply: Indeed, the addition of Ag in other biomedical alloy systems is relevant due to its unique properties, the paper cited above is closely related to our work, and this is why we included this article as a reference in the revised version in the introductory section.
Reviewer 2 Report
Comments and Suggestions for AuthorsStandardize consistently:
- Subscripts for chemical data/formula
- Spaces between numbers and units
- Units not in [] (especially in the diagrams)
- Check whether the information/units in the diagrams are consistent
- Observe bracketing in tables (unit in (), not property, e.g. Table 3)
- Please convert Spanish terms into English (especially in the tables, e.g. Table 3/4)
- Use the spelling “behavior” or “behavior”
- Use the spelling “Zinc”, “zinc” or “Zn”
- Use the spelling “S.Aureus” or “S. Aureus
Please do not use “we thought, we....” (e.g. line 194)
Table 1: Specification in weight or atomic percent?
The scales are not recognizable/legible in all figures
Please use SI units (especially in Figure 1 - technical drawings are dimensioned in mm) and add diameter symbols
Please use standardized line widths in Figure 1
The description for c) is missing in the caption for Figure 5
Why are some details written in bold? (e.g. lines 271-272, lines 324-326)
Ensure the units are stated consistently in the text (e.g. line 197, line 201).
Figure 5 is much too small
All abbreviations must be explained before use (e.g. SEM and XRD, line 220)
Comments on the Quality of English Languageonly moderate revision is necessary
Author Response
Answer to Reviewer 2
Comments and Suggestions for Authors
Standardize consistently:
- Subscripts for chemical data/formula
Reply: All subscripts in the chemical data/formula are set through all the revised manuscript
- Spaces between numbers and units
Reply: We add spaces between numbers and units through all the revised manuscript.
- Units not in [] (especially in the diagrams)
Reply: Figure 8 was modified not using units in []
- Check whether the information/units in the diagrams are consistent
Reply: Done
- Observe bracketing in tables (unit in (), not property, e.g. Table 3)
Reply: Table3 and Table 4, as well as some text, were corrected in this regard in the revised manuscript.
- Please convert Spanish terms into English (especially in the tables, e.g. Table 3/4)
Reply: we corrected Spanish word “aleación” and “año” and used “alloy” and “year” in Tables 3,4 in the revised manuscript.
- Use the spelling “behavior” or “behavior”
Reply: We checked and homogenized this spelling in the revised manuscript.
- Use the spelling “Zinc”, “zinc” or “Zn”
Reply: We checked and homogenized this spelling (zinc, but not in chemical formula, where we used Zn) in the revised manuscript
- Use the spelling “S.Aureus” or “S. Aureus
Reply: We checked and homogenized this spelling in the revised manuscript (S. Aureus).
Please do not use “we thought, we....” (e.g. line 194)
Reply: That line was modified in the revised manuscript.
Table 1: Specification in weight or atomic percent? The scales are not recognizable/legible in all figures
Reply: weight percent. We used wt% all through the revised manuscript.
The scales are not recognizable/legible in all figures
Reply: this issue was solved in the new Figures 2,3 and 9 with new, legible scales.
Please use SI units (especially in Figure 1 - technical drawings are dimensioned in mm) and add diameter symbols
Reply: Done in new Figure 1
Please use standardized line widths in Figure 1
Reply: Done in new Figure 1
The description for c) is missing in the caption for Figure 5
Reply: Ony the lable (c) was missing, the description was there.
Why are some details written in bold? (e.g. lines 271-272, lines 324-326)
Reply: We modified those formulas to standar text.
Ensure the units are stated consistently in the text (e.g. line 197, line 201).
Reply: We stated consistently units in the text. It has to be mentioned that the common units in the corrosion field are expressed degradation of surfaces in millimeters per year.
Figure 5 is much too small
Reply: The figures (a), (b), (c) were enlarged in the revised manuscript.
All abbreviations must be explained before use (e.g. SEM and XRD, line 220)
Reply: On pager 3 we explain SEM. XRD was defined in that line.
Comments on the Quality of English Language
only moderate revision is necessary
Submission Date
18 May 2024
Date of this 31 May 2024 10:57:18 review
Reviewer 3 Report
Comments and Suggestions for Authors1. Very short abstract. It should contain a short introduction to the topic, the novelty, the objectives, the methodology and the conclusions. Keywords are almost the same thing as the abstract.
2. What exactly is new about this study?
3. What are the dimensions of the Four Zn-Ag-Cu-0.05%Mg quaternary alloys?
4. Were all four samples used in all tests? How many tests were performed in each condition?
5. Materials supplied by whom?
6. Before a table or figure, text must appear to call the table or figure.
7. Figures 2 and 3 – the elements must be identified in the figure.
8. Line 264 - "could be" - authors should try to find justification in the open literature, it should not be "could be". They are an example of what appears throughout the text.
9. Figure 8 – Average values? A curve representative of all the others?
10. Line 349 – Why? How can the authors justify this observation?
11. Poor discussion with open literature. The conclusions may be questionable.
Author Response
Answer to reviewer 3
First, we, the authors of this manuscript would like to thank the reviewer for his professional job in suggesting changes and criticizing the original manuscript helped us to significantly improve our paper as you may notice in the revised manuscript.
Below you will find a detailed response to all queries expressed by reviewer 3.
- Very short abstract. It should contain a short introduction to the topic, the novelty, the objectives, the methodology and the conclusions. Keywords are almost the same thing as the abstract.
Reply: The abstract was completely rewritten including the elements you mention in your observations in point 1.
The abstract that appears in the revised version begins by mentioning that although Zn-Ag-Cu base alloys have aroused much interest as alloys for biomedical applications, they have not achieved the required mechanical properties. It also includes that our work seeks to improve these properties by exploring the effect of increasing the Ag and Cu contents in Zn-Ag-Cu alloys with a 0.05wt% Mg micro-alloy, the methodology followed to obtain the experimental alloys, manufactured in an electric furnace and hot extruded, as well as the most relevant conclusions.
Furthermore, In the revised version, the introduction was also improved. We rewrote an important part of the introduction, to include the reasons behind the selection of the 0.05% Mg content for the microalloying We also link to this discussion the mitigation of this problem reported by Ardakani et al. and K. Cheng et al. in the case of Zn-Mg micro alloys (<0.1wt% Mg) as a result of the presence of Cu and Ag as alloying agents. These elements act by delaying the diffusion of Mg in the Zn matrix, its arrival at the grain boundaries, and thus significantly delaying the formation of Mg2Zn11 precipitates responsible for the loss of ductility during aging. To this end, we moved the paragraph that originally referred to the work of Chen et. al. and the anti-aging ability present On page 2, paragraph 2 of the original manuscript and moved this paragraph to line 93, page 2, of the revised version, and it is from here that we made the improvements mentioned above, addressing the need to ameliorate the introduction of this article, with the improvements included from line 93, page 2, to line 146 of page 3 of the revised version.Keywords were reformulated according to the new abstract and introductory section as can be seen in the revised version.
- What exactly is new about this study?
Reply: There are several points of originality
For the first time in the open literature, Zn-Ag-Cu base alloys are reported that more than meet the mechanical property requirements for biomedical alloys by showing YS values ​​> 300MPa, UTS close to 400MPa and elongations between 18 and 26%.
For the first time, the joint effect of increasing amounts of the second phase (Ag, Cu)Zn 4 and a micro-alloy with 0.05% Mg is explored as measures to improve mechanical properties and meet the requirements for biomedical applications.
For the first time, the manufacture of a Zn-based heteromaterial is reported, whose microstructure and mechanical behavior achieve a synergy of strength and flexibility that allows these alloys to achieve the properties required for biomedical applications.
Finally, another point of originality lies in the fact that the results obtained show that it is possible to adjust the properties of the family of alloys defined by the ranges of Cu and Ag contents studied in this work by changing the Ag and Cu contents used as alloying agents.
- What are the dimensions of the Four Zn-Ag-Cu-0.05%Mg quaternary alloys?
Reply: for the as-cast cylindrical ingots, dimensions are diameter= 4cm and length=6cm. In the manuscript is explained that the extruded products of experimental alloys were machined into several discs 4 mm high and 1 cm in diameter for the antibacterial, corrosion, and cytotoxicity tests. Finally, the dimensions for the tensile test are shown in Figure 1..
- Were all four samples used in all tests? How many tests were performed in each condition?
Reply: No, Cytotoxicity was evaluated only for extruded A4 alloy, Antibacterial tests were performed only for extruded A2, A3, and A4 alloys by triplicate. The four extruded alloys were tested for mechanical properties by triplicate, corrosion rate by immersion test also by triplicate. In the case of MO and SEM the four alloys were examined in the cast, homogenized, and extruded condition using samples in triplicate. DRX characterization was performed on one sample for each extruded alloy
This information was added into the revised manuscript.
- Materials supplied by whom?
Reply: Local Suppliers were contacted to provide the following materials.
|
Material |
Supplier |
|
Zn 99.99 |
Industrias Peñoles |
|
Ag 99.99 |
Industrias Peñoles |
|
Mg 99.90 |
Elmet S.A .de C.V. |
|
Cu Electrolytic Cooper C11000 |
Mexicana de Cobre |
These suppliers guarantee high-quality materials.
The master alloys were manufactured in our laboratory using an induction furnace with a protective Argon atmosphere.
- Before a table or figure, text must appear to call the table or figure.
Reply: We agree and in the revised version we tried to comply with this basic rule of writing by trying to place text, figures, and tables in the best possible way. However, the distribution of our text and figures together with the nature of the edition of the template used to cast the manuscript resulted in the distribution of content present in the revised version.
- Figures 2 and 3 – the elements must be identified in the figure.
Reply: We consider that given the different nature of the two microconstituents presented in these figures, the fact that the second phase is presented as clear bands deformed in the direction of extrusion surrounded by dark zones of the Zn matrix allows the reader to easily identify them based on the description of these figures included in page 8, lines 270 to 278 of the revised version.
- Line 264 - "could be" - authors should try to find justification in the open literature, it should not be "could be". They are an example of what appears throughout the text.
Reply: We agree with the reviewer, we set the proper reference to support our discussions. We found four similar cases to the example given by the reviewer. In all of them, proper references were set in the revised manuscript..
- Figure 8 – Average values? A curve representative of all the others?
Reply: The determination of mechanical properties was carried out at least in triplicate and the results shown in Table 4 were obtained. Based on these results, the experimental curve that came closest to these results was selected to be included in Figure 8. Therefore, although they are not averages, they are representative of all the replicas. In the revised version, this is indicated in the caption of Figure 8..
10.-Line 349 – Why? How can the authors justify this observation?
Reply: The marked difference between the mechanical behaviors of alloys A2, A3, and A4 compared to A1 can only be due to the absence or presence of the second phase, which produces a mechanical behavior that is similar between the alloys that present a second phase and different from alloy A1, which only presents a recrystallized zinc matrix.
In the paragraphs following line 139 of the original article, the behavior of alloys A2, A3, and A4, which present a second phase and which, due to their microstructural characteristics and mechanical behavior, correspond to discontinuous laminar heteromaterials, is explained in detail. The presence of mechanical behavior is explained based on the classic references that have been published on the subject of hetero-materials and that explain said behavior. The reasons for the mechanical behavior of alloy A1, which presents, in addition to the yield point phenomenon, the Portevin Le Chatelier phenomenon, are also explained in the original manuscript.
11.-Poor discussion with open literature. The conclusions may be questionable.
Reply: The original version of the manuscript required many improvements and we have made every effort to ensure that the revised version allows the reader to identify the originality and contributions of this work.
Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors answered to all my questions.
