Microstructure, Mechanical Properties and Deformation Behavior of Fe-28.7Mn-10.2Al-1.06C High Specific Strength Steel
Round 1
Reviewer 1 Report
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Comments for author File: 
Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
Fe-Mn-Al-C steels are generating a lot of interest with potential applications for structural parts in the automotive industry due to low density and average strength. The authors of the paper "Microstructure, Mechanical Properties and Deformation Behavior of Fe-28.7Mn-10.2Al-1.06C High Specific Strength Steel" have investigated the microstructure and room temperature deformation behavior of the light-weight steel. The authors show the decrease of the steel strength with increasing the annealing temperature. Unfortunately, the manuscript is not well written and lacks scientific novelty. I cannot recommend the paper for publication in its current state due to the following reasons:
- The reading of the paper is very hard due to poor language. It is recommended to significantly improve English before the next submission.
- The Introduction part is very limited. It is needed to analyse more papers about microstructure and properties of the Fe-Mn-Al-C steels (e.g. 10.1016/j.pmatsci.2017.05.002).
- The authors describe generally known facts about the deformation mechanisms of the fcc-metals and the influence of the annealing temperature on the microstructure and mechanical properties. There is no scientific novelty in the paper.
- The authors wrote that “the specific strength has increased by more than 15% compared with other steels”. What does mean the term “other steels”, low-alloyed, high-strength, etc.?
- To improve the scientific part of the manuscript it is recommended to compare obtained mechanical properties with the properties of the similar Fe-Mn-Al-C steels with another composition.
- The authors should add to Table 1 the values of the yield strength and grain size of the steel after different annealings. The application of the Hall-Petch law may be useful for the analysis of the influence of grain size on the yield strength of the investigated steel.
- It is unclear from Figure 4 why the strain-hardening rate drastically drops at the strain of approximately 0.07 while the angle on the stress-strain curve does not change significantly at this moment. In my opinion, there is a significant error in the calculations.
- How the authors did calculate the true stress and true strain for the tensile curves? It is hard to do without a transverse extensometer due to deformation localization.
- How many samples were used for the determination of the mechanical properties? It is required to add the standard deviations to the values of mechanical properties in Table 1.
Author Response
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Reviewer 3 Report
This paper studied the microstructure and mechanical properties according to the annealing temperature of high specific strength steel. Interpretation of the experimental results and conclusions are appropriate. The following minor modifications are required.
1) In Figure 5, the density of the micro strip increased with the annealing temperature. It is necessary to add an explanation for the reason (e.g. the effect of grain size).
2) On page 4, You mentioned that 'Compared with other steels with 1000MPa, 30GPa·% strength-plastic product and 7.8 g/cm3 density [16], and the specific strength increased by more than 15%'.
Information (for example, composition) of the compared steel should be added. Is it similar type of materials?
3) In Figure 1, require typo correction, Inteysity → Intensity
Author Response
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Round 2
Reviewer 1 Report
The authors took into account most of the reviewer's comments, but they ignored some questions and not all the corrections made have contributed to improving the quality of the article.
Comments and Suggestions for Authors
The Figures. All figures except for the 1-st and 7-th have improper sizes. Please, increase the size of Figure 2a and its resolution (make it the same as in the cover letter file). After editing, the size of this figure has decreased! Increase the brightness in Figure 2 b. Increase the size of Figure 3. The same applies to Figure 4. The size of the figure with stress-strain curves has been reduced in the corrected version of the article. The yellow curve is hard to see in Figure 5, please change the color. Please, add diffraction patterns to Figures 6 and 7.
Table 1. “Grain size at different annealing time”. No time. Please change to temperature.
The authors avoided answering the question about additional reflections in the diffraction pattern. What phase (or phases) traces give these additional reflections? Please, discuss this, at least in a hypothetical way.
The reviewer strongly recommends discussing the results obtained in comparison with other works on lightweight high manganese steels in the discussion section. In particular, questions about a purely austenitic structure without carbide phases were left without any discussion. Such a high (1.06 wt %) carbon content can favor the precipitation of carbide phases.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The authors of the paper "Microstructure, Mechanical Properties and Deformation Behavior of Fe-28.7Mn-10.2Al-1.06C High Specific Strength Steel" have particially answered previous comments and did not make necessary modification of the manuscript. The paper should be improved accordingly following comments:
- Response 2: The Introduction part is very limited. It is needed to analyse more papers about microstructure and properties of the Fe-Mn-Al-C steels (e.g. 10.1016/j.pmatsci.2017.05.002).
Comment: It is not enough just to cite one recommended paper. The Introduction part is still very poor. It is needed to consider more papers about microstructure and properties of the Fe-Mn-Al-C steels and analyze this works in the Introduction part.
- Response 3: I have modified as follows: “The Fe-Mn-Al-C high specific strength steel studied in this paper has high tensile strength, elongation and low density. This characteristic is used in automobile industry to manufacture automobile steel plate, which can greatly reduce the body weight, reduce fuel consumption, resist plastic deformation caused by collision, and greatly improve the safety of automobile. In recent years, some correlation studies have been carried out on Fe-Mn-Al-C high specific strength steels in China and abroad, but there are still many problems to be solved. In order to further understand the mechanical properties and deformation behavior of Fe-Mn-Al-C high specific strength steel, this paper mainly obtained Fe-28.7Mn-10.2Al-1.06C high specific strength steel with excellent mechanical properties through reasonable composition design and optimization of annealing treatment process. The microstructure and mechanical properties of Fe-28.7Mn-10.2Al-1.06C high specific strength steel were analyzed, and the deformation behavior of the experimental steel after annealing was discussed in depth. It provides theoretical guidance for the development of Fe-Mn-Al-C series high specific strength steel with good comprehensive performance in composition design, deformation mechanism discussion and industrial production.”
Comment: This information was not added to the text of the manuscript. At the same time presented information cannot be an answer on the previous comment #3. The authors should improve the discussion part about the microstructure and mechanical properties of the investigated steel.
- Response 6: I have modified as follows: “The grain of the experimental steel grows after annealing. According to the Hall-Petch equation : σs = σ0 + Kd−0.5, it can be seen that with the increase of grain size, the yield strength decreases, and the grain boundary area per unit volume decreases. During plastic deformation, the grain boundary hinders dislocation slip, resulting in the decrease of strength.”
Comment: The authors should plot the graph YS vs d−0.5 and approximate it by the Hall-Petch equation.
- Response 9: I have modified as follows: “For each annealing process, three samples were used for the determination of mechanical properties.”
Comment: This information was not added to the text of the manuscript. It should be added to the Materials and methods part.
Author Response
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Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
The authors have answered previous comments and slightly improved the manuscript. I may recommend the manuscript for publication. One more improvement may be done: it is better to add the standard deviations for the YS and grain size values in Figure 5.
Author Response
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Author Response File: Author Response.pdf
