Effects of Partial Replacement of Si by Al on Cold Formability in Two Groups of Low-Carbon Third-Generation Advanced High-Strength Steel Sheet: A Review

Round 1

Reviewer 1 Report

In this review article, the author has summarized decades of data on the effects of Partial Replacement of Si by Al in AHSS steel sheets. Such information and perspectives drawn from this summary are useful for the scientific community. However I feel that the article can be further improved by making few minor changes, suggested below.

1) The motivation for the need for this review article is not clearly stated in the introduction. For example, can you comment on how can the perspectives drawn in this article be used by other researchers to advance this field?

2) The author is suggested to review the entire article for linguistic inconsistencies. Several sentences in the article are confusing. For example,

a) in abstract, page 1, lines 11-12, "In this paper, ... into two groups, “Group I” and “Group II”." Consider breaking down into two sentences.

b) in abstract, page 1, lines 17 "enhances further" to "further enhances"

c) Page 2, lines 83-84, "In addition, the content is limited because Al is a ferrite-stabilizing ability element [69].". It is unclear what the content is referring to and the word "ability" is not required.

d) page 7, line 250, "In general, austenite former elements". "forming" or "stabilizing", is more suited here instead of "former"? "former" appears in many places.

Author Response

Thank you so much for your kind review. Following your comments, the authors reply as follows. The revised word and sentences are highlighted by the yellow ribbons or bands in the revised manuscript.

In this review article, the author has summarized decades of data on the effects of the Partial Replacement of Si by Al in AHSS steel sheets. Such information and perspectives drawn from this summary are useful for the scientific community. However, I feel that the article can be further improved by making a few minor changes, suggested below.

1) The motivation for the need for this review article is not clearly stated in the introduction. For example, can you comment on how can the perspectives drawn in this article be used by other researchers to advance this field?

[Reply]　To make the need for this review clear, the following sentence was added on line 85.

To promote the application of galvanized AHSS sheets to automotive parts, many researchers investigate the effect of partial replacement of Si by Al on the microstructural and mechanical properties such as tensile property and formability in low-carbon TBF [12-14], Q&P [21,22,24], CFB [28,31,32,34], D-MMn [38,42], BF-MMn [45], Q&P-MMn [47,49], and TM [55]  steels, in the same manner as the first-generation AHSSs such as TRIP-aided polygonal ferrite (TPF) [70-78] and TRIP-aided annealed martensite (TAM) steels [75,78] (Table 1).

2) The author is suggested to review the entire article for linguistic inconsistencies. Several sentences in the article are confusing. For example,

1. a) in abstract, page 1, lines 11-12, "In this paper, ... into two groups, “Group I” and “Group II”." Consider breaking down into two sentences.

[Reply]　Unfortunately, it is difficult to divide the sentence into two sentences. So, the sentence was revised as follows,

In this paper, the effects of the partial replacement on the microstructure, tensile property, and cold formability are introduced in the AHSS sheets which are classified into two groups, “Group I” and “Group II”.

1. b) in abstract, page 1, lines 17 enhances further" to "further enhances"

[Reply]　Following your comment, the sentence was revised as follows. In the same way, the sentence of line 767 was also revised.

A complex addition of Al and Nb/Mo further enhances the stretch-flangeability.

1. c) Page 2, lines 83-84, "In addition, the content is limited because Al is a ferrite-stabilizing ability element [69].". It is unclear what the content is referring to and the word "ability" is not required.

[Reply]　“a ferrite-stabilizing ability element” was changed to “a ferrite-stabilizing element”.

1. d) page 7, line 250, "In general, austenite former elements". "forming" or "stabilizing", is more suited here instead of "former"? "former" appears in many places.

[Reply]　“former” was changed to “stabilizing”.

That’s all

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript is relatively comprehensive and worth publishing.

Author Response

Thank you so much for your kind review.

Reviewer 3 Report

The manuscript summarize the different microstructural and mechanical aspects of III generation of AHSS steel. In my opinion the paper could be published, after concerning the small issues mentioned bellow:

1/ Figure 2a. The graph concerning the one-step Q&P process is not correct in my opinion. The quenching and partitioning process is used to, firstly form selected martensite fraction and then carry out the partitioning stem in the same or higher temperature. However on this figure the line don’t cross the M_s temperature, so non martensite will form in the microstructure before partitioning. This will create the bainitic matrix with some fraction of retained austenite.  

2/ Figure 4. It would be good to add the legend concerning the dark and white dots on it. Right now it is hard to determine if for example black dots corresponded to volume fraction or carbon concentration.

3/ In the chapter 6.1. About the bendability of C-Si-Mn steel the chemical composition from the work [29] does not fully correspond to the third generation of AHSS steel (medium-manganese steels). How the analysis carried out in this chapter correspond to the steels with 3, 4 or higher manganese content. Are there any works corresponding to the medium-manganese steel which are more typical associated with III generation of the AHSS steel? 

4/ In the position [45]: Morawiec, M.; Ruiz-Jimenez, V.; Garcia-Mateo, C.; Jimenez, J.A.; Grajcar, A. Study of the isothermal bainitic transformation and austenite stability in an advanced Ai-rich medium-Mn steel. Arch. Civil Mech. Eng. 2022, 22, 152. The Ai in Ai-rich, should be changed to Al (aluminum). 

Author Response

Thank you so much for your kind review. Following your comments, the author replies as follows. The revised word and sentences are highlighted by the blue ribbons or bands in the revised manuscript.

The manuscript summarizes the different microstructural and mechanical aspects of III generations of AHSS steel. In my opinion, the paper could be published, after concerning the small issues mentioned below:

1/ Figure 2a. The graph concerning the one-step Q&P process is not correct in my opinion. The quenching and partitioning process is used to, firstly form selected martensite fraction and then carry out the partitioning stem in the same or higher temperature. However on this figure the line don’t cross the Ms temperature, so non martensite will form in the microstructure before partitioning. This will create the bainitic matrix with some fraction of retained austenite. 

[Reply] Thank you so much for the important comment. The one-step Q&P process is incorrect as per your comment. Figure 2b was revised as follows. Regarding this, a part of the caption of Figure 3 was also revised.

Figure 3. Illustration of the typical microstructure of various third-generation AHSSs [83]. (a): TBF, CFB, one-step Q&P and BF-MMn steels (T_IT > M_s), (b): TBF, CFB, one-step Q&P, and BF-MMn steels (T_IT ＝ M_s −  M_f), and two-step Q&P and two-step Q&P-MMn steels (T_IT > M_s), (c): TM and M-MMn steels (T_IT < M_f). α_bf, α_m, α_m*, γ_R, θ, and MA represent bainitic ferrite, primary coarse soft martensite, secondary fine hard martensite, retained austenite, carbide, and MA phase (a mixture of αm* and film-like γ_R), respectively.

2/ Figure 4. It would be good to add the legend concerning the dark and white dots on it. Right now it is hard to determine if for example black dots corresponded to volume fraction or carbon concentration.

[Reply] To understand the initial volume fraction and carbon concentration of retained austenite, marks (● and ○) were added in the caption, as follows.

Figure 4. Variations in initial volume fraction (fγ₀, ●) and carbon concentration (Cγ₀, ○) of retained austenite as a function of isothermal transformation temperature (T_IT) in 0.20C-1.59Si-1.50Mn-0.05Nb (mass%) TBF and TM steels [51]. The holding time of the IT process is 1000 s. This figure is reproduced based on Ref. [51].

3/ In the chapter 6.1. About the bendability of C-Si-Mn steel the chemical composition from the work [29] does not fully correspond to the third generation of AHSS steel (medium-manganese steels). How the analysis carried out in this chapter correspond to the steels with 3, 4 or higher manganese content. Are there any works corresponding to the medium-manganese steel which are more typical associated with III generation of the AHSS steel?

[Reply] Figure 17 corresponds to the results of CFB steel, not MMn steel. The chemical composition of this steel is incorrect and was revised as follows. The chemical composition in the manuscript was also revised (line 666).

Figure 17. Variations in (a) average bending angle, (b) yield stress (YS), ultimate tensile strength (UTS), and total elongation (TE), and (c) volume fractions of retained austenite and martensite as a function of austempering temperature in 0.34C-1.65Si-1.94Mn-9.07Cr1.07Cr CFB steel [29]. M_s of the steel is 329 °C.

4/ In the position [45]: Morawiec, M.; Ruiz-Jimenez, V.; Garcia-Mateo, C.; Jimenez, J.A.; Grajcar, A. Study of the isothermal bainitic transformation and austenite stability in an advanced Ai-rich medium-Mn steel. Arch. Civil Mech. Eng. 2022, 22, 152. The Ai in Ai-rich, should be changed to Al (aluminum).

[Reply]　The “Ai” in Ai-rich was changed to “Al”. Thank you.

That’s all

Author Response File: Author Response.pdf