Ti-Fe-Based Alloys Modified with Al and Cr for Next-Generation Biomedical Implants

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work is of undoubted interest for understanding the influence of the composition of various titanium-iron alloys on their properties, which is important for practical application in various fields. However, the article needs to be revised. There are a number of comments.

1. The abstract should provide more specific data with numerical indicators. For example, it is unclear what amount of aluminum and chromium was in the titanium-iron alloys and at what temperature they were obtained. This information is important for understanding the influence of these metals on the properties of the alloys.
2. The introduction should clearly justify the need to introduce aluminum and chromium into the alloys, and also explain the fundamental differences between the alloys obtained by the authors and those already known.
3. The methods should clearly reflect the conditions and for what samples (initial powders or finished alloys) the tests were carried out, since the correct interpretation of the results depends on this. Particular attention should be paid to the description of the corrosion test, since there is no description of the environment in which the polarization curves were taken.
4. It is necessary to move the descriptions of the methods for determining density and corrosion rate from Section 3 to Section 2.
5. It is unclear in the method what amount of additives were in the alloys. For example, an alloy of 97% titanium - 7% iron, i.e. 114% instead of 100%, etc.
6. It is necessary to improve the quality of Figure 2. When describing this figure, it is also desirable to indicate not only the shape, but also the average size of the particles.
7. It is unclear what the authors mean by the phrase alloy with "best density" (line 189).
8. It is necessary to improve the quality of Figure 5, since the size scale is not visible.
9. The authors indicate that the obtained alloys have higher strength than bone. Will this affect the surrounding tissues in the body?
10. The conclusions need to be edited, since the presented form describes the results, but without summarizing the conclusions.
11. It is unclear how the authors draw a conclusion about the corrosion behavior of the obtained alloys in the body, since biological fluids also contain enzymes that affect processes in the body.
12. In the list of references, references 4 and 9 are identical.

Author Response

Manuscript ID: ENG- 3858010

Type of manuscript: Article

Title: Ti-Fe-Based Alloys Modified with Al and Cr: A Powder Metallurgy Approach for Biomedical Applications

 

REPLY TO REVIEWERS' COMMENTS

 

We are thankful to the reviewers for their constructive and important comments. By taking in account of their suggestions, some sections of the manuscript have been modified for clarity (highlighting with yellow those parts that have been modified). Below, we give our rebuttal to their comment.

 

 

Reviewer 1

 

This work is of undoubted interest for understanding the influence of the composition of various titanium-iron alloys on their properties, which is important for practical application in various fields. However, the article needs to be revised. There are a number of comments.

 

1. The abstract should provide more specific data with numerical indicators. For example, it is unclear what amount of aluminum and chromium was in the titanium-iron alloys and at what temperature they were obtained. This information is important for understanding the influence of these metals on the properties of the alloys.

Answer: The abstract included the most relevant data on alloy processing and the results obtained.

 

2. The introduction should clearly justify the need to introduce aluminum and chromium into the alloys, and also explain the fundamental differences between the alloys obtained by the authors and those already known.

Answer: The use of Al and Cr in the Ti-Fe alloy was justified in the introduction.

 

3. The methods should clearly reflect the conditions and for what samples (initial powders or finished alloys) the tests were carried out, since the correct interpretation of the results depends on this. Particular attention should be paid to the description of the corrosion test, since there is no description of the environment in which the polarization curves were taken.

Answer: The experimental section included the medium used for the corrosion tests.

 

4. It is necessary to move the descriptions of the methods for determining density and corrosion rate from Section 3 to Section 2.

Answer: This suggestion was implemented.

 

5. It is unclear in the method what amount of additives were in the alloys. For example, an alloy of 97% titanium - 7% iron, i.e. 114% instead of 100%, etc.

Answer: There was a numerical error here. Instead of 97% titanium, it should say 93% titanium. This has already been corrected in the manuscript.

 

6. It is necessary to improve the quality of Figure 2. When describing this figure, it is also desirable to indicate not only the shape, but also the average size of the particles.

Answer: The images have been enhanced and a description of the approximate size of the powder is included in the text.

 

7. It is unclear what the authors mean by the phrase alloy with "best density" (line 189).

Answer. The term “best” was changed to the term “highest,” which is correct.

 

8. It is necessary to improve the quality of Figure 5, since the size scale is not visible.

Answer The quality of figure 5 was improved, now size scale is visible.

 

9. The authors indicate that the obtained alloys have higher strength than bone. Will this affect the surrounding tissues in the body?

Answer: Certainly, the strength of manufactured alloys is greater than that of bone. However, their value is not so significantly high as to affect the functioning of bone in the human body.

 

10. The conclusions need to be edited, since the presented form describes the results, but without summarizing the conclusions.

Answer: A brief introduction to the conclusions was added in order to summarize them in the results obtained.

 

11. It is unclear how the authors draw a conclusion about the corrosion behavior of the obtained alloys in the body, since biological fluids also contain enzymes that affect processes in the body.

Answer: A solution widely used in literature was employed to simulate bodily fluids. Of course, for this material to be used in the body, much more in-depth biocompatibility studies would have to be carried out. So far, it has been established that the alloys studied offer promising possibilities for use as biomaterials, but as already mentioned, much more research is needed in this area.

 

12. In the list of references, references 4 and 9 are identical.

Answer: There was an error, but the correct reference has now been added.

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks to the author's efforts, but I have some comments:

1. Increase the reference numbers in the results and discussion.
2. Abstract: The microhardness test is not a physical test. it is a mechanical test.
3. Too many even references in one sentence in the introduction.
4.   Figs. 2, 4, and 5 need the font to be increased.
5. magnification (optical microscope at 10x magnifica-196 tion of the microstructure of the three alloys.) not correct because it differs from one microscope to another. The authors can write the scale bar in microns.
6. Why don't these phases appear in XRD as written in the microstructure (mixture of α-Ti and α-Fe phases) and (a mixture of α and β phases of titanium, and the precipitates formed most likely correspond to the Ti3Al intermetallic)  as expected phases from the phase diagram?
7.  Mention the relative density with microhardness and corrosion. where increasing the relative density in Ti-Fe-Cr led to the highest microhardness, besides the mentioned reasons. 
8. Fig. 9 is wrong in drawing. It needs to be redrawn again because it is not logical to have the same potential for the three alloys 
9.  Define all abbreviations, such as RHE, reference electrode.
10. Add a table for the electrochemical parameters.
11. Add references to the equations 
12. Add an introduction to the conclusions.

Author Response

Manuscript ID: ENG- 3858010

Type of manuscript: Article

Title: Ti-Fe-Based Alloys Modified with Al and Cr: A Powder Metallurgy Approach for Biomedical Applications

 

REPLY TO REVIEWERS' COMMENTS

 

We are thankful to the reviewers for their constructive and important comments. By taking in account of their suggestions, some sections of the manuscript have been modified for clarity (highlighting with yellow those parts that have been modified). Below, we give our rebuttal to their comment.

 

 

Reviewer 2

 

Thanks to the author's efforts, but I have some comments:

 

1. Increase the reference numbers in the results and discussion.

Answer: It was done

 

2. Abstract: The microhardness test is not a physical test. it is a mechanical test.

Answer: we modified that in te abstract

 

3. Too many even references in one sentence in the introduction.

Answer: This is because there several works related with the subjet, therefor we don not considerd that this is wrong.

 

4. Figs. 2, 4, and 5 need the font to be increased.

Answer: These figures were improved.

 

5. magnification (optical microscope at 10x magnifica tion of the microstructure of the three alloys.) not correct because it differs from one microscope to another. The authors can write the scale bar in microns.

Answer: In the three images of figure 4, there is the size scale bar

 

6. Why don't these phases appear in XRD as written in the microstructure (mixture of α-Ti and α-Fe phases) and (a mixture of α and β phases of titanium, and the precipitates formed most likely correspond to the Ti3Al intermetallic) as expected phases from the phase diagram?

Answer: The peaks in the diffraction patterns were identified with the corresponding phases.

 

7. Mention the relative density with microhardness and corrosion. where increasing the relative density in Ti-Fe-Cr led to the highest microhardness, besides the mentioned reasons.

Answer: A conclusion was added highlighting this situation.

 

8. Fig. 9 is wrong in drawing. It needs to be redrawn again because it is not logical to have the same potential for the three alloys

Answer: The potencial in figure 9 is different in the three alloys, and it is show in figure. So we don not undestand what referee ia meaning?

 

9. Define all abbreviations, such as RHE, reference electrode.

Answer: the meaning of the corresponding abbreviation was added

 

10. Add a table for the electrochemical parameters.

Answer: The requested information has been added to a results table.

 

11. Add references to the equations

Answer: The corresponding reference was added

 

12. Add an introduction to the conclusions.

Answer. This was done.

Reviewer 3 Report

Comments and Suggestions for Authors

This paper should be revised . These comments should be addressed in the content of the paper. 

1. The abstract is a complete qualitative summary. The quantitative data should be highlighted as the results of the paper.
2. It is unnecessary to show error bars in cumulative graphs; you can mention the standard deviation and the number of repetitions in the caption.
3. In Figure 1, the broad PSD in Ti-Fe-Cr is said to aid optimal packing. Can the authors provide quantitative compaction density data to support this claim?
4. In Figure 1, does the overlap of error bars between alloys indicate no statistically significant differences in particle size distributions? Was ANOVA or t-testing performed?
5. The authors may also wish to review and use the findings from studies related to biomedical implants made by powder metallurgy that could strengthen the background or discussion section. DOI: 10.1016/j.jallcom.2018.07.261 and https://doi.org/10.1016/j.mspro.2015.11.134
6. It would be better for the authors to delete this part of the title and propose a new title: A Powder metallurgy Approach for Biomedical Applications. This is not very scientific.
7. In the Ti-Fe spectrum, peaks at ~44.7°, 65°, and 82.3° are attributed to BCC Fe phases. Were JCPDS card numbers used to confirm these assignments? Please add the plans index.
8. Was any peak broadening analysis, such as the Scherrer equation, performed to estimate crystallite size, especially since the study discusses structure?
9. Did the authors perform quantitative phase analysis to determine relative phase fractions, such as α-Ti, Fe₂Ti, Ti₃Al, and BCC Cr?
10. In Ti-Fe-Al, the text mentions the presence of Ti₃Al. Which specific peaks in the diffractogram confirm the formation of Ti₃Al?
11. Both Ti-Fe and Ti-Fe-Al show multiple secondary peaks with moderate intensity. Could this suggest higher microstrain or lattice distortion compared to Ti-Fe-Cr?
12. The error bars in Figure 7 appear asymmetric in length. Are they standard deviations, standard errors, or confidence intervals? Clarification is needed.
13. Ti-Fe-Cr shows the highest hardness at approximately 1150 HV. Is this solely due to Cr substitutional strengthening or also due to reduced porosity (21% vs. 26% in Ti-Fe)?
14. Do the hardness values, ranging from approximately 500 to 1150 HV, agree with previously reported values for Ti-Fe, Ti-Fe-Al, and Ti-Fe-Cr systems in powder metallurgy studies? Some published Ti-Fe alloys report much lower HV, between 200 and 400 HV.
15. Please include a strain-stress graph of the samples and then conclude the Young's modulus.
16. The weight loss graph needs error bars.
17. The curves flatten after about 6 days for Ti-Fe-Al, suggesting passivation. Was the formation of protective oxides confirmed by SEM, EDS, or XPS?

Author Response

Manuscript ID: ENG- 3858010

Type of manuscript: Article

Title: Ti-Fe-Based Alloys Modified with Al and Cr: A Powder Metallurgy Approach for Biomedical Applications

 

REPLY TO REVIEWERS' COMMENTS

 

We are thankful to the reviewers for their constructive and important comments. By taking in account of their suggestions, some sections of the manuscript have been modified for clarity (highlighting with yellow those parts that have been modified). Below, we give our rebuttal to their comment.

 

 

Reviewer 3

 

This paper should be revised . These comments should be addressed in the content of the paper.

 

1. The abstract is a complete qualitative summary. The quantitative data should be highlighted as the results of the paper.

Answer: The abstract has been modified.

 

2. It is unnecessary to show error bars in cumulative graphs; you can mention the standard deviation and the number of repetitions in the caption.

Answer: The reason for placing the error bars in Figure 1 is answered in question 4 of the reviewer's comments.

 

3. In Figure 1, the broad PSD in Ti-Fe-Cr is said to aid optimal packing. Can the authors provide quantitative compaction density data to support this claim?

Answer: A reference was added to the study related to powder packing and its effect on densification during sintering, in order to support our assertion.

 

4. In Figure 1, does the overlap of error bars between alloys indicate no statistically significant differences in particle size distributions? Was ANOVA or t-testing performed?

Answer: Indeed, in this figure, the error bars indicate that there is no significant difference in the measurements taken, which were carried out in triplicate, and what is reported is the average obtained with the respective standard deviation. Unfortunately, we do not perform an ANOVA or T-testing.

 

5. The authors may also wish to review and use the findings from studies related to biomedical implants made by powder metallurgy that could strengthen the background or discussion section. DOI: 10.1016/j.jallcom.2018.07.261 and https://doi.org/10.1016/j.mspro.2015.11.134

Answer: Thanks for the references, ther were added in the intoroduction section.

 

6. It would be better for the authors to delete this part of the title and propose a new title: A Powder metallurgy Approach for Biomedical Applications. This is not very scientific.

Answer: we attend this suggestion and actually the title of the manuscript was modified.

 

7. In the Ti-Fe spectrum, peaks at ~44.7°, 65°, and 82.3° are attributed to BCC Fe phases. Were JCPDS card numbers used to confirm these assignments? Please add the plans index.

Answer: All peaks in the diffraction patterns were identified with the corresponding phases.

 

8. Was any peak broadening analysis, such as the Scherrer equation, performed to estimate crystallite size, especially since the study discusses structure?

Answer: This action was not carried out.

 

9. Did the authors perform quantitative phase analysis to determine relative phase fractions, such as α-Ti, Fe₂Ti, Ti₃Al, and BCC Cr?

Answer: This action was not carried out, because we don not have the program to do this cuantification.

 

10. In Ti-Fe-Al, the text mentions the presence of Ti₃Al. Which specific peaks in the diffractogram confirm the formation of Ti₃Al?

Answer: Actually the corresponding peks to Ti₃Al were identified in the corresponding diffraction pattern.

 

11. Both Ti-Fe and Ti-Fe-Al show multiple secondary peaks with moderate intensity. Could this suggest higher microstrain or lattice distortion compared to Ti-Fe-Cr?

Answer: It is considered that there should be a slight distortion of the crystal structure of Ti-Fe and Ti-Fe-Al alloys due to the formation of secondary phases and precipitates as observed in the microstructure, unlike the Ti-Fe-Cr system where the formation of the BCC structure is very stable.

 

12. The error bars in Figure 7 appear asymmetric in length. Are they standard deviations, standard errors, or confidence intervals? Clarification is needed.

Answer: Those lines correspond to standart deviation, now it is clarified in the mansucript.

 

13. Ti-Fe-Cr shows the highest hardness at approximately 1150 HV. Is this solely due to Cr substitutional strengthening or also due to reduced porosity (21% vs. 26% in Ti-Fe)?

Answer: A conclusion was added at the end stating that due to the improved densification of the Ti-Fe-Cr alloy, this was what obtained the best mechanical performance.

 

14. Do the hardness values, ranging from approximately 500 to 1150 HV, agree with previously reported values for Ti-Fe, Ti-Fe-Al, and Ti-Fe-Cr systems in powder metallurgy studies? Some published Ti-Fe alloys report much lower HV, between 200 and 400 HV.

Answer. In the reference No. 29, which corresponds to a review of many articles related to the application of titanium-based systems, several studies with properties similar to those stated here are reported. In the discussion of the results of the mechanical properties, this reference was added.

 

15. Please include a strain-stress graph of the samples and then conclude the Young's modulus.

Answer. The Young´s modulus was measured by the ultrasónic method, therefore we don´t have the strain-stress graphs for their determination.

 

16. The weight loss graph needs error bars.

Answer: No error bars were included in Figure 1 because the test was repeated five times and no significant changes in the weight loss of the alloys were observed.

 

17. The curves flatten after about 6 days for Ti-Fe-Al, suggesting passivation. Was the formation of protective oxides confirmed by SEM, EDS, or XPS?

Answer: Something similar is also observed for the Ti-Fe alloy. In reality, we did not confirm the formation of any oxide here, which is what causes alloys to become passive. However, we researched the literature and confirmed passivation due to the formation of surface oxides, we discuss this in the manuscript and added the corresponding reference.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

In the new version of the article, the authors took into account the comments and recommendations. It is recommended to publish the article after minimal editing, and "Minimal editing" means checking from the point of view of the English language.

Reviewer 3 Report

Comments and Suggestions for Authors

Comments were addressed, and the paper can be accepted by the journal