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by
  • Lingxiao Hu 1,
  • Xingfu Wang 1,* and
  • Juhua Liang 2,*
  • et al.

Reviewer 1: Anonymous Reviewer 2: Anonymous

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article concerns enhancing the mechanical and corrosion resistance properties of Fe-25Mn-12Cr-0.3C TWIP steels via N alloying and processing optimization. The article is based on 36 references. It has a typical structure. The introduction presents the current state of knowledge, and the remaining chapters contain a description of the materials tested, the research methods used, a discussion of the research results, and conclusions. The authors compare two steel grades in two different treatments. They examine mechanical properties and conduct electrochemical corrosion and microstructural studies. In my opinion, some chapters require additions or corrections. I have summarized my comments and questions below.

Detailed comments and questions:

  1. The article lacks references to the authors' previous works. Do the authors have scientific experience in this field?
  2. Table 1: The sum of all elements does not equal 100%. Please, complete the table.
  3. How many samples were subjected to static tensile tests?
  4. Table 2: Please, add the standard deviation.
  5. Fig. 5: Please, change the color of the descriptions on the figures as they are difficult to read.
  6. Page 5 and conclusion no. 1: In my opinion, the authors do not confirm the presence of carbides in the microstructures. Please, provide additional research.
  7. Were corrosion products tested?
  8. The figure should be on the same page as the figure caption (Fig. 4).
  9. Please, complete the statements (Author Contributions, etc.).

Author Response

  1. The article lacks references to the authors' previous works. Do the authors have scientific experience in this field?

Response: We sincerely thank the reviewer for this valuable comment. We have supplemented the citation of our previous systematic works on high-Mn TWIP steels in the introduction section, and clearly stated our long-term research experience in this field. Our previous studies have comprehensively covered strength-ductility synergy enhancement, additive manufacturing, and corrosion resistance improvement of TWIP steels [3,4,6,7,12,15], which have laid a solid methodological and theoretical foundation for the present study. The relevant content has been added to Page 2, Paragraph 2 of the revised manuscript, and all corresponding references have been supplemented in the reference list.

  1. Table 1: The sum of all elements does not equal 100%. Please, complete the table.

Response: We apologize for the omission. We have added the Fe (balance element) column in Table 1, and recalculated the mass fraction of Fe to ensure the total sum of all elements is 100%. The revised Table 1 is shown in Page 3 of the revised manuscript.

  1. How many samples were subjected to static tensile tests?

Response: Thank you for this comment. Static tensile tests were performed on 3 parallel samples for each processing condition to ensure the reliability of the results. We have supplemented this information in Section 2.3 (Page 4) of the revised manuscript.

  1. Table 2: Please, add the standard deviation.

Response: We have added the standard deviation of all mechanical property data in Table 2, which were calculated from 3 parallel tests.

  1. 5: Please, change the color of the descriptions on the figures as they are difficult to read.

Response: We apologize for the poor readability of the descriptions. We have revised all the descriptions in Fig. 5: the text has been changed to bold black with enlarged font size.

  1. Page 5 and conclusion no. 1: In my opinion, the authors do not confirm the presence of carbides in the microstructures. Please, provide additional research.

Response: We sincerely thank the reviewer for this constructive comment. We have supplemented EDS elemental mapping and quantitative point analysis (new Table 2) of the grain boundary precipitates, which confirm they are Cr-rich carbides.

All relevant descriptions in the manuscript have been revised to use the precise term "Cr-rich carbides" to maintain scientific rigor. The new characterization results have been added to Section 3.1 (Pages 6), and the statement in Conclusion 1 has also been updated accordingly.

  1. Were corrosion products tested?

Response: Thank you for this valuable comment. We have supplemented XPS analysis of the corrosion products, which clarify the phase composition and surface chemical states of the corrosion products for the TWIP steel samples.

The corresponding test method has been added to Section 2.2, and the relevant results and discussion have been added to Section 3.3 (Page 12) of the revised manuscript.

  1. The figure should be on the same page as the figure caption (Fig. 4).

Response: We have adjusted the typesetting of the manuscript to ensure that Fig. 4 and its caption are on the same page, which strictly follows the typesetting guidelines of the journal.

  1. Please, complete the statements (Author Contributions, etc.).

Response: We have supplemented the statement sections required by the journal, such as Author Contributions, Declaration of Competing Interest, Acknowledgments. These sections have been added after the Conclusion section of the revised manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors
  1. The highlights section is overly long and contains rather general statements.
  2. The abstract is too long; experimental details are not mentioned, and numerical results are not provided.
  3. The introduction is quite short and insufficient in terms of providing a comprehensive background for the study.
  4. The effect of nitrogen (solid solution strengthening and pitting resistance) is already well known in the literature; therefore, the study appears to lack novelty. The final paragraph of the introduction should more clearly and explicitly state the contribution of this work to the literature.
  5. What are the standards used for the mechanical and corrosion tests?
  6. All samples should be presented in a table, including their compositions and corresponding codes.
  7. It is stated that all tests were repeated three times; however, error values are not provided in Table 2.
  8. Performing passive film analysis would significantly improve the quality of the study.
  9. What is the evidence for the statement “N promotes Cr enrichment in the passive film”? Surface analyses such as XPS and EDS should be provided.
  10. The texts in Figure 5 should be made clearer and more readable.

Author Response

  1. The highlights section is overly long and contains rather general statements.

Response: We have revised the highlights section according to the journal's requirements. The revised highlights are shown in the front page of the revised manuscript.

  1. The abstract is too long; experimental details are not mentioned, and numerical results are not provided.

Response: We have rewritten the abstract to be more concise. The specific experimental parameters and core quantitative results have been supplemented, and the structure is clear with purpose, method, results and conclusion. The revised abstract is shown in the front page of the revised manuscript.

  1. The introduction is quite short and insufficient in terms of providing a comprehensive background for the study.

Response: We have expanded the introduction section from four dimensions: application pain points of TWIP steels, research status of performance optimization, and existing research gaps. The comprehensive background fully demonstrates the necessity of this work.

  1. The effect of nitrogen (solid solution strengthening and pitting resistance) is already well known in the literature; therefore, the study appears to lack novelty. The final paragraph of the introduction should more clearly and explicitly state the contribution of this work to the literature.

Response: We sincerely thank the reviewer for this critical comment. We have rewritten the final paragraph of the introduction, and clearly proposed three core innovations and academic contributions of this work, which distinguish our study from the existing literature. We have clarified that this work systematically reveals the coupling regulation mechanism of N alloying and thermomechanical processing on the strength-ductility-corrosion resistance synergy of Fe-25Mn-12Cr-0.3C TWIP steel, which has not been reported in previous studies.

  1. What are the standards used for the mechanical and corrosion tests?

Response: We have supplemented the specific standards adopted for tensile tests and electrochemical corrosion tests in Section 2.3 (Page 4) of the revised manuscript.

  1. All samples should be presented in a table, including their compositions and corresponding codes.

Response: We sincerely thank the reviewer for this practical suggestion. We have supplemented and improved the Table 1 by adding the detailed processing state for the samples.

The revised Table 1 now summarizes the designation, chemical composition and corresponding processing conditions of all samples, and is located on Page 3 of the revised manuscript for readers' convenient reference.

  1. It is stated that all tests were repeated three times; however, error values are not provided in Table 2.

Response: We have supplemented the standard deviation (error values) of all data in the original Table 2 (renumbered as Table 3), which are calculated from 3 parallel tests.

  1. Performing passive film analysis would significantly improve the quality of the study.

Response: We fully agree with the reviewer's valuable suggestion. We have supplemented detailed passive film characterization using XPS analysis.

The results demonstrate that N alloying facilitates the formation of a denser, more stable passive film enriched in Cr2O3, which is the key mechanism for the enhanced corrosion resistance of the steel. The relevant results and in-depth discussion have been added to Section 3.3 (Page 12) of the revised manuscript.

  1. What is the evidence for the statement “N promotes Cr enrichment in the passive film”? Surface analyses such as XPS and EDS should be provided.

Response: We have supplemented detailed XPS spectrum analysis of the passive films formed on N-alloyed and N-free steels. The quantitative XPS results directly confirm that the Cr/Fe atomic ratio and the relative proportion of protective Cr2O3 in the passive film of N-alloyed steel are significantly higher than those of N-free steel, which provides solid evidence that N promotes Cr enrichment in the passive film.

  1. The texts in Figure 5 should be made clearer and more readable.

Response: We have revised the descriptions in Fig. 5. All labels have been optimized for readability, and the high-resolution image has been replaced in the revised manuscript.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors answered nine of my questions (or comments). I have no comments on seven of the answers. Only two questions require further commentary.

Comment no. 1: The article lacks references to the authors' previous works. Do the authors have scientific experience in this field?

Response: We sincerely thank the reviewer for this valuable comment. We have supplemented the citation of our previous systematic works on high-Mn TWIP steels in the introduction section, and clearly stated our long-term research experience in this field. Our previous studies have comprehensively covered strength-ductility synergy enhancement, additive manufacturing, and corrosion resistance improvement of TWIP steels [3,4,6,7,12,15], which have laid a solid methodological and theoretical foundation for the present study. The relevant content has been added to Page 2, Paragraph 2 of the revised manuscript, and all corresponding references have been supplemented in the reference list.

Reviewer: The authors listed several articles in which they are authors. I am unable to identify the authors of the three articles below. Please, explain the discrepancies.

No. 3:

Zhang WX, Wang J, Wan J, et al. Improved yield strength-ductility synergy of a high Mn TWIP steel by grain refinement and partial recrystallization. Materials Science and Engineering A, 916 (2024): 147355

Authors of this article: W.X. Zhang, J. Wang, J. Wan, Y.B. Cong, C. Li, Y.Z. Chen

https://www.sciencedirect.com/science/article/abs/pii/S0921509324012863

No. 4:

Wang W, Wang D, Han FS, et al. Study on the mechanical behavior of twinning-induced plasticity steel processed by warm forging and annealing. Journal of Materials Science, 53 (2018): 14645-14656.

Authors of this article: Wen Wang, Dan Wang & Fusheng Han

https://link.springer.com/article/10.1007/s10853-018-2597-5

No. 12:

Wang K, Wei AP, Tong X, et al. Improvement of the anti-corrosion property of twinning-induced plasticity steel by twin-induced grain boundary engineering. Materials Letters, 211 (2018): 118-121

Authors of this article: Kun Wang, Aiping Wei, Xian Tong, Jixing Lin, Lufan Jin, Xintao Zhong, Dan Wang

https://www.sciencedirect.com/science/article/abs/pii/S0167577X17314477

Comment no. 2: Table 1: The sum of all elements does not equal 100%. Please, complete the table.

Response: We apologize for the omission. We have added the Fe (balance element) column in Table 1, and recalculated the mass fraction of Fe to ensure the total sum of all elements is 100%. The revised Table 1 is shown in Page 3 of the revised manuscript.

Reviewer: The authors completed the table.

Comment no. 3: How many samples were subjected to static tensile tests?

Response: Thank you for this comment. Static tensile tests were performed on 3 parallel samples for each processing condition to ensure the reliability of the results. We have supplemented this information in Section 2.3 (Page 4) of the revised manuscript.

Reviewer: The authors supplemented the article in this regard.

 Comment no. 4: Table 2: Please, add the standard deviation.

Response: We have added the standard deviation of all mechanical property data in Table 2, which were calculated from 3 parallel tests.

Reviewer: The authors added the standard deviation.

 Comment no. 5: Fig. 5: Please, change the color of the descriptions on the figures as they are difficult to read.

Response: We apologize for the poor readability of the descriptions. We have revised all the descriptions in Fig. 5: the text has been changed to bold black with enlarged font size.

Reviewer: The authors corrected the descriptions.

Comment no. 6: Page 5 and conclusion no. 1: In my opinion, the authors do not confirm the presence of carbides in the microstructures. Please, provide additional research.

Response: We sincerely thank the reviewer for this constructive comment. We have supplemented EDS elemental mapping and quantitative point analysis (new Table 2) of the grain boundary precipitates, which confirm they are Cr-rich carbides.

All relevant descriptions in the manuscript have been revised to use the precise term "Cr-rich carbides" to maintain scientific rigor. The new characterization results have been added to Section 3.1 (Pages 6), and the statement in Conclusion 1 has also been updated accordingly.

Reviewer: In my opinion, the authors did not confirm the presence of carbides - there is no information about the type of carbides (chemical formula). Please, provide further research or provide relevant literature.

Comment no. 7: Were corrosion products tested?

Response: Thank you for this valuable comment. We have supplemented XPS analysis of the corrosion products, which clarify the phase composition and surface chemical states of the corrosion products for the TWIP steel samples.

The corresponding test method has been added to Section 2.2, and the relevant results and discussion have been added to Section 3.3 (Page 12) of the revised manuscript.

Reviewer: The authors added research.

Comment no. 8: The figure should be on the same page as the figure caption (Fig. 4).

Response: We have adjusted the typesetting of the manuscript to ensure that Fig. 4 and its caption are on the same page, which strictly follows the typesetting guidelines of the journal.

Reviewer: The authors supplemented the article in this regard.

Comment no. 9: Please, complete the statements (Author Contributions, etc.).

Response: We have supplemented the statement sections required by the journal, such as Author Contributions, Declaration of Competing Interest, Acknowledgments. These sections have been added after the Conclusion section of the revised manuscript.

Reviewer: The authors supplemented the article in this regard.

Author Response

Reviewer: The authors listed several articles in which they are authors. I am unable to identify the authors of the three articles below. Please, explain the discrepancies.

Response: We sincerely thank the reviewer for your careful verification and valuable comment. We sincerely apologize for the confusion caused by our imprecise and inaccurate expression in the original manuscript.

The three studies mentioned were conducted by Dr. Dan Wang, Dr. Kun Wang and other researchers who previously worked at the Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences. We have maintained long-term academic exchanges with this research group, but it was completely inappropriate to directly refer to these works as "our previous systematic works".

  • We have adjusted the citation logic of references [3,4,12] in the introduction section, changing all first-person "we" to third-person objective citations to accurately reflect the independent research contributions of the original authors.
  • We have re-clarified and accurately stated the original research achievements of our research group (Prof. Xingfu Wang's group and Prof. Juhua Liang's group) as the solid research foundation of this work, including:
  • Our systematic study on the effect of Cr addition on the corrosion behavior of Fe-Mn-C TWIP steels [14,15];
  • Our research on the composition design, microstructure regulation and comprehensive performance optimization of high-strength corrosion-resistant TWIP steels [14].

The above revisions have been completed on Page 2, Paragraph 2 of the revised manuscript, and all references have been double-checked to ensure their accuracy. We greatly appreciate your rigorous academic attitude, which has helped us correct the inappropriate expression and significantly improve the academic standardization of the manuscript.

Reviewer: In my opinion, the authors did not confirm the presence of carbides - there is no information about the type of carbides (chemical formula). Please, provide further research or provide relevant literature.

Response: We sincerely thank the reviewer for this constructive comment. While exact crystal structure determination requires SAED or HRTEM analysis, our quantitative EDS point analysis (Table 2) combined with well-established literature evidence enables us to reliably identify the grain boundary precipitates as (Cr,Fe,Mn)23C6-type complex carbides:

First, atomic ratio calculation (excluding oxygen and trace silicon) yields a metal-to-carbon ratio of approximately 4.25:1, which is close to the theoretical stoichiometric ratio of 3.83:1 for M23C6-type carbides. The slight deviation is well within the widely recognized 10-20% quantitative error of EDS for light elements such as carbon.

Second, the elemental distribution (54.68 wt.% Cr, 25.32 wt.% Fe, 11.17 wt.% Mn) is characteristic of M23C6 carbides in high-Mn high-Cr austenitic steels, and thermodynamic studies have confirmed this is the only stable Cr-rich carbide phase under the hot forging conditions employed in this work [18,19,23].

Our core conclusion that grain boundary carbide precipitation causes Cr depletion and subsequent intergranular corrosion has been directly verified by our EDS analysis. We have revised the relevant descriptions in Section 3.1 and Conclusion 1 to reflect this accurate identification.

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors

The authors clarified my doubts. I recommend the article for publication.