Microstructure Refinement of 301 Stainless Steel via Thermomechanical Processing

Round 1

Reviewer 1 Report

Extensive literature is available on thermo-mechanical processing of 301 SS for microstructure refinement. It has been shown by various researchers that the stability of the austenite phase varies under different deformation conditions i.e. room or sub zero temperature deformation. It is well known that under subzero deformation the kinetics of strain-induced transformation is accelerated resulting in the near complete formation of martensitic microstructure. This aids phase reversion to austenite leading to grain refinement (Conclusion 1 by authors). The formation of bimodule grain size distribution is well documented for phase reversion treatment (Conclusion 2). The deformation mechanism under sub zero treatment is well understood and well documented in various literatures.
Therefore, I believe this manuscript lacks in novelty.

Author Response

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Reviewer 2 Report

Khaled J. Al-Fadhalah et al. studied microstructure refinement of 301 stainless steel via thermo-mechanical processing. The work presents intersting results and can be considered for acceptance after proper revision.

 

1. "HABs are depicted in black, austenite is depicted in blue, ε-martensite is depicted in yellow, and α'-martensite is depicted in red." How do you distinguish the different phases in EBSD? More introduction and discussion are needed.

2. A schematic is suggested to better reflect the material preparation process and the characteristics of samples.

3. The authors show a large number of EBSD maps. Whether TEM images have been tested to observe more subtle structural features such as precipitated phases?

4. What are the differences and similarities between the curves of three different strain hardening stages compared with conventional materials? What's the reason? Please discuss in detail.

5. Ruler length values for all EBSD images should be relabeled, currently too small.

6. How does this material exhibit properties compared to other materials?  

7. Some references are too old. Authors need to review and cite the related work in the last two years. Here are some recent works for your reference.

[1] Trans. Nonferrous Met. Soc. China 2021, 31, 1205−1216. DOI: 10.1016/S1003-6326(21)65572-3 

[2] Rare Metals. 2022, 41(1), 209–217. DOI: 10.1007/s12598-021-01744-x

[3] Scripta Materialia 2022, 217, 114767.  DOI: 10.1016/j.scriptamat.2022.114767 

8. It is suggested that different lines in Figure 9 should be displayed in different colors to make it easier to distinguish.

9. Materials and Methods. line 14. 

"-3" and "-1" in "1×10-3 s-1" should be superscript.

Author Response

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Reviewer 3 Report

1. The abstract section of the text is confusing. It is recommended that it be re-crafted to highlight the innovative nature of the article.

2. In the text 3.1. the phase transformation section suggests that "Increasing TMP cycles enhanced the formation of α'-martensite during tensile deformation, implying that austenite stability against strain-induced martensitic transformation has weakened." Is there a relevant quantitative explanation?

3.What is the mechanism of formation of shear type reversion from martensite to austenite. How the shear band of austenite is represented on the way in the text.

Author Response

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Reviewer 4 Report

Reviewer #1: This manuscript is an important and interesting study to produce refined austenitic microstructure for improving strength and hardness in 301 stainless steel via Thermo-Mechanical Processing. However, some clarifications must be made before publication.

 

1. Page 4. In " Materials and Methods " part, The test method for the chemical composition of the samples using XRF may not be accurate, especially for elements N and C. Other methods should be considered to obtain accurate values.

 

2. Page 4. In " Materials and Methods " part, "… The first scheme involved three cycles of 0.15 tensile-strain deformation at -50 ° C, The second used two cycles of tensile deformation of at -50 ° C to a strain of 0.20, And the third applied one cycle of tensile deformation of at -50 ° C to a strain of 0.30…." confused description , please rewrite them such as “The first scheme involved three cycles of 0.15 tensile-strain deformation at -50 ° C and annealing once after each deformation …… ”

 

3. Page 4. In " Materials and Methods " part, authors mentioned that "the samples were gradually heated up to 850 ° C and remained at this temperature for 5 min to allow phase reversion and recrystallization." The annealing process is ambiguous. the samples were heated up along with furnace or were put into furnace after reaching the setting temperature? If it is the former, please provide the heating rate.

 

4. Page 5. In " Materials and Methods " part, changing "S3, S9, and S27 ……" to "……Σ3,Σ9, and Σ27 ……".

 

5. Please supplement EBSD phase map of as-received sample.

 

6. Page 5. In " Phase Transformation " part, " with a volume fraction of 97.4% for

both ε- and α'-martensite" should be changed to " with a volume fraction of 97.4% for ε- and α'-martensite"

7. The scale of all the EBSD diagrams in this paper is fuzzy. Please redrawn them.

 

8. Page 17. In " Conclusions (iii)" part, "…The change in the mechanism of α'-martensite formation/deformation is marked by stage-III hardening, characterized by a decrease in strain hardening rate and hardness.", What is the test temperature for hardness? If the hardness was measured at room temperature, the tensile analysis at -50 ℃ by hardness at room temperature is unreasonable. please clarify it.

Author Response

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Reviewer 5 Report

Abstract - missing broader implications.

Excellent - detailed introduction. 

Clear overview of materials and methods provided.

Table 1 - details could be separated out - repetitive in places.

Scale bars on micrographs too small to see - please crop and add larger.

Fig 9  seems very noisy - how have you separated the three sections?

Generally a well written paper, with a few minor corrections required.

 

Author Response

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Round 2

Reviewer 1 Report

I appreciate author's effort in improving the science content of the manuscript

Author Response

The authors take this opportunity to thank the reviewer for the valuable comments.

Reviewer 2 Report

The authors addressed the reviewer's concerns and made changes as requested. In this case,  the article can be considered for acceptance.

Author Response

The authors take this opportunity to thank the reviewer for the valuable comments.