Analysis of Phase Transformations in Fe-Ni-Al Alloys Using Diffusion Couples of Fe/Fe-33at.%Ni-33at.%Al Alloy/Ni
and Victor M. Lopez-Hirata *Round 1
Reviewer 1 Report
This work investigated the precipitation behavior within a diffusion couple of Ni/Fe-Ni-Al/Fe, and the evolution of microstructure is rationalized by thermodynamic and kinetic calculation. The results will contribute to understanding the mechanical property and alloy design. However, there are many phases in this work, and they are mixed in the context. The authors should check the paper carefully. The concerns with this work are as follows.
1) The meaning of n in Eq.(2)
2) I cannot find the diffusion path from Fig. 2b, particularly beta’ + gamma
3) In lines 176-183, there is no gamma’ in Figs 4a-b.
4) Line 177, “which also agrees with the ternary phase diagram at 1100 °C, Fig. 2 (b)”, I could not find the gamma’ in Fig. 2b for Fe/FeNiAl diffusion couple.
5) Fig.4 shows the beta phase which may be beta’.
6) Line 197, says “SEM micrographs of Figs. 5 (a and b) correspond to the Ni/Fe-Ni-Al alloy side”, but the caption of Fig. 5 shows Fe/Fe-Ni-Al.
7) The aging is carried out at 750 °C, why the calculation by TC-Prisma is for 550 °C?
Author Response
Dear Reviewer,
First, we thank you for all your comments and suggestions to improve our paper. According to the mandatory revisions and additional requests, the modifications and corrections are blue highlighted, and they are as follows:
The reviewer pointed out that there are many phases in this work, and they should check in the paper carefully,
Answer: The position of each phase in the manuscript was carefully verified. Besides, a new table, Table 2, was included to clarify the chemical and structural characteristics of each phase.
1) The meaning of n in Eq. 2.
Answer: The meaning of n is the number of components. This was specified in line 96 of the manuscript.
2) I can not find the diffusion path from Fig 2b, particularly beta´+ gamma
Answer: There was a misprint in the diffusion path (1). There is no beta´+ gamma region, and thus it was deleted from the diffusion path, as shown in line 166.
3) In lines 176-183, there is no gamma in Figs 4a-b.
Answer: The gamma phase is clearly shown in Figs 4 (a and b). It seems that the correction is related to Figs. 2(a and b). The gamma phase was clearly indicated in Fig. 2.
4) Line 177, “which also agrees with the ternary phase diagram at 1100 °C, Fig 2(b), I could not find the gamma´ in Fig. 2b for Fe/Fe-Ni-Al diffusion couple.
Answer: The gamma phase was indicated in Fig. 2.
5) Fig. 4 shown the beta phase which may be beta´.
Answer: There was a misprint, and beta prime was corrected in Figs. 4.
6) Line 197, says “ SEM micrographs of Figs. 5 (a and b) correspond to the Ni/Fe-Ni-Al side, but the caption of Fig. 5 shows Fe/Fe-Ni-Al.
Answer: The caption figure corresponds to Ni/Fe-Ni-Al alloy, and it was modified.
7) The aging is carried out at 750 °C, why the calculation by TC prisma is for 550 °C.
Answer: The chemical compositions change from point to point in the diffusion couple. Thus, we select only two compositions, Fe-10at.%Ni-15at.%at.% and Fe-33at.%Ni-33at.%at.%, to study the inverse and normal precipitation reactions, respectively. However, the activation energy at 750 °C for the inverse precipitation is too high, and the TC-Prisma simulation is difficult to carry out. Therefore, the optimum temperature for the precipitation simulation was 550 °C in both alloys. This fact is explained in the manuscript in lines 294-298.
Reviewer 2 Report
This paper reports γ’ and β’ precipitations and phase transformations in the diffusion coupling system, Ni/Fe-Ni-Al/Fe, by comparing with experimental measurement and CALPHAD simulation.
However, this paper can not be normally red to the last by some fatal mistakes. In line 175, “Figs. 4 (a and b) illustrate the most representative SEM micrographs for Ni/FeNiAl alloy diffusion couple side.” is explained, but caption of Fig.4 shows “SEM micrographs of the Fe/Fe-Ni-Al alloy diffusion couple side”. It seems that figure for Ni/FeNiAl alloy diffusion couple side does not exist. Furthermore, in line 197, “SEM micrographs of Figs. 5 (a and b) correspond to the Ni/Fe-Ni-Al alloy side aged at 750 °C for 100 and 250 h, respectively” is showed, but “the Fe/Fe-Ni-Al alloy diffusion couple side” appears in the caption. This paper is hard to be understood by the confusion.
This paper must be carefully rewritten from scratch. I recommend that this paper will be rejected.
Author Response
Dear Reviewer,
First, we thank you for all your comments and suggestions to improve our paper. According to the mandatory revisions and additional requests, the modifications and corrections are yellow highlighted, and they are as follows:
1) In line 175, “Figs. 4 (a and b) illustrate the most representative SEM micrographs for Ni/FeNiAl alloy diffusion couple side.” is explained, but caption of Fig.4 shows “SEM micrographs of the Fe/Fe-Ni-Al alloy diffusion couple side”. It seems that figure for Ni/FeNiAl alloy diffusion couple side does not exist.
Answer: There was a misprint in the caption of Fig. 4, which was corrected. That is, the figure caption corresponds to Ni/FeNiAl alloy, as-shown in line 248.
2) Furthermore, in line 197, “SEM micrographs of Figs. 5 (a and b) correspond to the Ni/Fe-Ni-Al alloy side aged at 750 °C for 100 and 250 h, respectively” is showed, but “the Fe/Fe-Ni-Al alloy diffusion couple side” appears in the caption.
Answer: There was a misprint in the caption of Figs. 5 and Fig. 6, they were corrected. That is the figure caption corresponds to Ni/FeNi-Al alloy and Fe/Ni-Fe-Al, respectively, as shown in lines 250 and 253.
Besides, we carried out several modifications such as more information, more references, more tables, and better analysis in order to show more comprehensive results and discussion section, as well as the conclusions.
Reviewer 3 Report
In this work the authors have studied the solid state diffusion and related phase transformations in Fe/Fe-33Ni-33Al/Ni diffusion couples. The work is interesting and worthy of publication subject to revision. The authors should consider the following comments:
1.You should provide a comprehensive table with denominations of the various phases described in the introduction (α, β, γ, L21, …). You should specify their crystal structure (space group) and chemical composition ranges.
2.The authors studied diffusion couples; however, they haven’t calculated diffusion coefficients. The diffusion coefficients should be estimated from the concentration profiles (Fig. 1) and compared with the literature.
3.The SEM images show only the interfaces (Figs. 3, 4, 5, 6). You should also show the cross sections.
4.SEM images need to be supplemented with EDS results. Furthermore, you should provide X-ray diffraction patterns to confirm phases.
5.Section 4 (Discussion) includes results (see Figs. 7, 8, Table 3). As such, it should be combined with the results section and titled Results and Discussion.
Author Response
Dear Reviewer,
First, we thank you for all your comments and suggestions to improve our paper. According to the mandatory revisions and additional requests, the modifications and corrections are yellow highlighted, and they are as follows:
1) You should provide a comprehensive table with denominations of the various phases described in the introduction (α, β, γ, L21, …). You should specify their crystal structure (space group) and chemical composition ranges.
Answer: A new table, Table 2, was included to specify the main characteristics of all phases as requested.
2) The authors studied diffusion couples; however, they haven’t calculated diffusion coefficients. The diffusion coefficients should be estimated from the concentration profiles (Fig. 1) and compared with the literature.
Answer: The diffusion coefficients for the diffusion-couple analysis with Dictra were taken from the database MOBNi9 from Thermo-Calc, and the used reference, 34-41, were included in the manuscript. This fact was explained in lines 111-118.
3) The SEM images show only the interfaces (Figs. 3, 4, 5, 6). You should also show the cross sections.
Answer: The SEM micrographs correspond to areas located in Fe, Ni and Fe-33at.%Ni-33at.%Al alloy regions and not at the interface. This was explained in lines 184.
4) SEM images need to be supplemented with EDS results. Furthermore, you should provide X-ray diffraction patterns to confirm phases.
Answer: The chemical composition changes from point to point in the diffusion couple, and thus the present phases are different, while the XRD analysis corresponds to a specimen area. Therefore, XRD analysis seems to be not applicable to this case.
5) Section 4 (Discussion) includes results (see Figs. 7, 8, Table 3). As such, it should be combined with the results section and titled Results and Discussion.
Answer: Results and discussion section were merged as requested.
Reviewer 4 Report
This manuscript discusses the results of an investigation on the phase transformation in Fe-Ni-Al alloys. They report that the aging treatment at 750 C promoted inverse precipitation reactions such as beta' -> beta + alpha. The article appears to have potential although I have a few comments:
1. For the Vickers hardness tests details are missing such as how the indents were spaced and how many indents were performed. Was the dwell time 12 s? Please mention this.
2. Please provide references for the TCFE11 and MOFE6 databases.
3. Please do not use both green and red colored lines in the same graph, such as used in Figure 1.
4. In the caption of Figure 4, please define what the greek symbols are.
5. Same thing with Figures 5 and 6.
6. In Figure 7, only one indent per distance value? If this is true, the authors must perform multiple indents at each depth.
7. In the Conclusions section, please better explain how your work resulted in an advance rather than just providing a list of findings.
There are several grammatical errors in the manuscript that need to be fixed.
Author Response
Dear Reviewer,
First, we thank you for all your comments and suggestions to improve our paper. According to the mandatory revisions and additional requests, the modifications and corrections are yellow highlighted, and they are as follows:
1) For the Vickers hardness tests details are missing such as how the indents were spaced and how many indents were performed. Was the dwell time 12 s? Please mention this.
Answer: This detail was included in the experimental section, line 141.
2) Please provide references for the TCFE11 and MOFE6 databases.
Answer: The references are already included in lines 111-118.
3) Please do not use both green and red colored lines in the same graph, such as used in Figure 1.
Answer: Figure 1 was modified as requested.
4) In the caption of Figure 4, please define what the greek symbols are.
Answer: The word phase was included after each Greek letter.
5) Same thing with Figures 5 and 6.
Answer: The word phase was included after each Greek letter,
6) In Figure 7, only one indent per distance value? If this is true, the authors must perform multiple indents at each depth.
Answer: The microhardness procedure was included in lines 140-141.
7) In the Conclusions section, please better explain how your work resulted in an advance rather than just providing a list of findings.
Answer: The conclusion numbers 4 and 5 were improved, as shown in lines 345-351.
8) There are several grammatical errors in the manuscript that need to be fixed.
Answer: The manuscript was revised to correct grammatical errors.
Round 2
Reviewer 1 Report
No.
Author Response
There are no requirements.
Reviewer 2 Report
Please confirm and/or modify “Fe/FeNiAl”, “Fig.4” and “Fig.3” in lines 208-210 by comparing with captions of Figure 3, Figure4 and Figure 5, again.
Author Response
Dear Reviewer,
First, we thank you for all your comments and suggestions to improve our paper. According to the mandatory revisions and additional requests, the modifications and corrections are yellow highlighted, and they are as follows:
1) Please confirm and/or modify “Fe/FeNiAl”, “Fig.4” and “Fig.3” in lines 208-210 by comparing with captions of Figure 3, Figure4 and Figure 5, again.
Answer: There were misprints in this part of the manuscript, and they were corrected in lines 186-187 and 190-192.
Reviewer 3 Report
Authors answered some of my previous comments and improved their paper. Several issues have been clarified. However, there are still a couple of points that need a significant attention:
1.I understand that you used previously published diffusion coefficients to calculate the theoretical concentration profiles. However, Fig. 1 clearly shows that there was a difference between the theoretical (calculated) and experimental concentration profiles. Therefore, you should obtain the diffusion coefficients from your experimental data and compare them with literature. The experimental diffusion coefficients are the most valuable data from your work. If the experimental D values are provided, it will elevate the importance and significance of your work. You should use an analytical function to fit the experimental concentration profiles of Al, Fe and Ni and obtain the inter-diffusion coefficients. There are plentiful references on obtaining the experimental diffusion coefficients, see, e.g., https://doi.org/10.1007/s10853-020-04805-1 or https://doi.org/10.1016/j.ssi.2011.09.003.
2. You should clearly indicate from where exactly the SEM images have been taken. It is not enough to mention that they were taken from the Fe/Fe-Ni-Al side (Fig. 2). Make a sketch of the Fe/Fe-Ni-Al/Ni sandwich in the inset and indicate the position clearly. Is the SEM image taken from the bulk of Fe, bulk of Fe-Ni-Al or from the interface? If it is taken from the bulk, how far was it from the interface? Indicate it clearly. The same applies to Figs. 4, 5 and 6.
Author Response
Dear Reviewer,
First, we thank you for all your comments and suggestions to improve our paper. According to the mandatory revisions and additional requests, the modifications and corrections are yellow highlighted, and they are as follows:
Authors answered some of my previous comments and improved their paper. Several issues have been clarified. However, there are still a couple of points that need a significant attention:
1)I understand that you used previously published diffusion coefficients to calculate the theoretical concentration profiles. However, Fig. 1 clearly shows that there was a difference between the theoretical (calculated) and experimental concentration profiles. Therefore, you should obtain the diffusion coefficients from your experimental data and compare them with literature. The experimental diffusion coefficients are the most valuable data from your work. If the experimental D values are provided, it will elevate the importance and significance of your work. You should use an analytical function to fit the experimental concentration profiles of Al, Fe and Ni and obtain the inter-diffusion coefficients. There are plentiful references on obtaining the experimental diffusion coefficients, see, e.g., https://doi.org/10.1007/s10853-020-04805-1 or https://doi.org/10.1016/j.ssi.2011.09.003.
Answer: We carefully read the interesting paper of Zhong et al. in J. Mater. Sci. (2020). We noticed that the following conditions are necessary for the calculation of interdiffusion coefficients: 1) a single-phase region and 2) two diffusion paths with at least one common interception point in the same single-phase region to be able to apply the different calculation methods, such as Boltzman-Matano, Matano-Kirkaldy, etc. In the present work, we only have one diffusion path in a single-phase region for the beta prime phase, as shown in Fig. 2 (b), and thus there is no common interception point. This paper mentioned that the diffusion paths should be designed in a single-phase; however, our experiment was designed to study the phase formation in Fe-Ni-Al alloys. In the case of the pseudobinary method, the composition of one element must be kept constant to obtain the interdiffusion coefficients; however, this is not the case in our experiments. Thus, it seems no possible to calculate the interdiffusion coefficients of Fe-Ni-Al system, which are important to the process design and understanding of the material properties.
2) You should clearly indicate from where exactly the SEM images have been taken. It is not enough to mention that they were taken from the Fe/Fe-Ni-Al side (Fig. 2). Make a sketch of the Fe/Fe-Ni-Al/Ni sandwich in the inset and indicate the position clearly. Is the SEM image taken from the bulk of Fe, bulk of Fe-Ni-Al or from the interface? If it is taken from the bulk, how far was it from the interface? Indicate it clearly. The same applies to Figs. 4, 5 and 6.
Answer: The SEM observation zones are indicated by F3, F4, F5 and F6, which correspond to Figs. 3,4, 5, and, 6, respectively. This notation was also used for explanation in lines 186-187, 190-191, 212-213, and 236-237.
Reviewer 4 Report
Accept.
Author Response
There are no requirements.
Round 3
Reviewer 3 Report
Authors answered my comments and improved their paper. It can be accepted for publication.
