Casting Homogeneity of Scaled-Up Multiprincipal Component Alloys

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Brief Summary

This paper investigates the casting of a Cu-Zn-Mn-Ni alloy. This study builds on previous lab scale work by assessing the impact of scale up on the developed properties. Given the properties measured there is an investigation into observed differences using modelling. Reasonable conclusions are drawn on the likely effects of micro-segregation on hardness.

General comments

The paper describes and demonstrates the issues which are associated with casting scale up. Given the reliance on the the hardness data and EDX I have two comments:

1) Can there be some analysis of significance of the hardness data? A T-Test (in Excel?) would allow the reader to see how significant the differences are.

2) Given the scale of the dendrite arms (5-10 microns across) it would be worth commenting on the electron interaction volume for EDX and likely sampling of different phases sub-surface. Also, as the results are quoted to 1 d.p. a standard deviation from all the readings of a particular phase in a particular layer would be helpful. For example Phase 1, upper layer Ni 26.5+/-X.Y. This would help with the significance of the differences.

Also, given the discussion around cooling rates then the other check here would be grain size and morphology. This would be similarly impacted and give a clue to relative cooling rates. However, I do understand that this work may not have been done. Next paper?

Specific comments

Line 73. Discussion starts around multicomponent brasses but ref [19] is not a brass. Maybe change the word brasses to alloys?

Line 83 Conventional cast process; is this sand, metal mould, investment? For some brass castings this is plaster.

Line 82. It is not totally clear that the second sentence in the paragraph is still referring to ref [5]. It could be the start of the experimental work for this paper.

Line 85. 'We estimate' could become 'it is estimated that'.

Line 125. Would it be possible to annotate Figure 1 with casting orientation and where the subsequent slices were taken from? Given that a 75x80x70mm block becomes a 10x15x20mm block and then becomes three slices. I am assuming that the three slices are not from the smaller block but this is not clear, hence, a request for mark-up on Figure 2.

Line 130 Check consistency of notation with line 124; 75x80x70mm vs 10mm x 15mm x 20mm.

Line 233. Any reason the plots of top, middle and bottom are drawn bottom, middle, top? Not crucial to fix.

Author Response

Casting Homogeneity of Scaled-up Multi-Principal Component Alloys, Gbenga. J. Adeyemi, C Utton, Y Azakli and R. Goodall

Response to reviewers

We thank the editorial team and reviewers for their attention to our manuscript, and apologize for the delay in completing these revisions, due to the combined effect of the Christmas vacation, and the principal author relocating to Nigeria after a research visit to the UK.  We appreciate the time taken developing the reviews, and have attempted to respond to all of the comments in this document, also indicating the changes in the manuscript in red text.

Review 1

Brief Summary

This paper investigates the casting of a Cu-Zn-Mn-Ni alloy. This study builds on previous lab scale work by assessing the impact of scale up on the developed properties. Given the properties measured there is an investigation into observed differences using modelling. Reasonable conclusions are drawn on the likely effects of micro-segregation on hardness.

General comments

The paper describes and demonstrates the issues which are associated with casting scale up. Given the reliance on the the hardness data and EDX I have two comments:

• Can there be some analysis of significance of the hardness data? A T-Test (in Excel?) would allow the reader to see how significant the differences are.

Thank you for this suggestion, which is indeed feasible with the data we have.  Performing the test gives a t-value of t(16) = 5.984, p<0.00001 when comparing middle and top datasets, and a t-value of t(16) = 5.046, p<0.00001 for the comparison between middle and bottom datasets, both of which indicate that both of these pairs are different.  On the other hand, the t-value comparing the top and bottom is only t(16) = 0.746, p=0.23045, indicating the two groups are similar.

We have included this information with the discussion of the hardness data.

2) Given the scale of the dendrite arms (5-10 microns across) it would be worth commenting on the electron interaction volume for EDX and likely sampling of different phases sub-surface. Also, as the results are quoted to 1 d.p. a standard deviation from all the readings of a particular phase in a particular layer would be helpful. For example Phase 1, upper layer Ni 26.5+/-X.Y. This would help with the significance of the differences.

Thank you; we are happy to make some comments on the interaction volume size, and the potential for this to impact on the results.  Having examined our data, we have seen that, likely by statistical chance, the low deviation in these results values, would give a value for the standard deviation that appears low.  However, we feel that it would be misleading to include this, as the number of repeat measurements we made was small, and the accuracy is likely to be more significantly limited by the fundamental accuracy of the equipment, made worse by the potential for phase overlap referred to in this comment.  For these reasons, rather than present the standard deviations in the data, we have chosen to add an enhanced discussion of the EDX data accuracy, and to reflect on this in our discussions, which essentially means that there is no conclusive evidence of macrosegregation (as we had concluded from the XRF results), with any compositional differences between the centre and the upper and lower regions being related to differences in microsegregation.

Also, given the discussion around cooling rates then the other check here would be grain size and morphology. This would be similarly impacted and give a clue to relative cooling rates. However, I do understand that this work may not have been done. Next paper?

As noted below, one of the other reviewers also commented on grain size, and we of course recognise the importance of this parameter.  We have endeavoured to include more information on this in the paper, but the number of images we have been able to take in the microscope thus far does not allow us to give this to great accuracy (we nevertheless report what we have at this time).  We will indeed seek to gain more data to facilitate a more accurate measure for future work.

Specific comments

Line 73. Discussion starts around multicomponent brasses but ref [19] is not a brass. Maybe change the word brasses to alloys?1a

Thank you, we have slightly reordered the text here to avoid this confusion.

Line 83 Conventional cast process; is this sand, metal mould, investment? For some brass castings this is plaster.

In this case this was a metal mould, and we have added this to the text

Line 82. It is not totally clear that the second sentence in the paragraph is still referring to ref [5]. It could be the start of the experimental work for this paper.

This line is indeed referring to our new experimental work, and we have reworded for clarity on this point.

Line 85. 'We estimate' could become 'it is estimated that'.

Thank you, this is changed

Line 125. Would it be possible to annotate Figure 1 with casting orientation and where the subsequent slices were taken from? Given that a 75x80x70mm block becomes a 10x15x20mm block and then becomes three slices. I am assuming that the three slices are not from the smaller block but this is not clear, hence, a request for mark-up on Figure 2.

Thank you, we have done this, and agree that it makes the description clearer.

Line 130 Check consistency of notation with line 124; 75x80x70mm vs 10mm x 15mm x 20mm.

This has been checked; the two dimensions refer to the original ingot, and then the size of the blocks that were taken from it for characterization.  We have improved the wording to make this clear.

Line 233. Any reason the plots of top, middle and bottom are drawn bottom, middle, top? Not crucial to fix.

Our apologies for this; it is somewhat confusing with the juxtaposition of the position in the figure and the position in the cast ingot.  We have moved these traces.

Review 2

The purpose of the research should be clearly expressed – at the end of introduction is the best to write it.

Apologies for not setting this out clearly originally.  We have clarified the end of the introduction to clearly focus on the purpose of the research we are describing.

You need to explain why one bar is enough for your assessment.

We agree that this is important information.  We have elected to include a statement on the reasoning behind this at the start of the section where we discuss the ingot processing, detailing the motivation and also the limitations that this decision leads to.

Why did you choose the bar dimensions used in your research and not others? Does this have anything to do with the production of some components in practice?

There is not a strong link to a particular component that made us choose the sizes that we did, it is more around the general dimensions, and the capabilities of our equipment.  We have also discussed this in the new writing at the start of the ingot processing section.

Can you evaluate the size of the grains in all three areas of ingot?

As we were not able to collect a large number of images of the grains under SEM, we had refrained from doing this.  However, we agree that this is an important measure, and useful in the current context, so we have performed this analysis, and included the data in the manuscript, along with the statistical significance.

Figure 8. All peaks should be marked with identified phases. You need to correct drawing caption.

Thank you, we have made these changes.

Review 3

The manuscript provides an experiment for Casting Homogeneity of Scaled-up Multi-Principal Component Alloys. I believe that the topic of the article is very important for many industrial applications and may be of interest to a large group of readers. Overall, I rate the article positively, but some corrections should be made before publication:

1. The abstract mentions a range of hardness values but does not specify the actual values or the extent of the variation. Including these details would provide a clearer snapshot of your findings and their significance.

Thank you for your overall positive comments.  For this specific point, we have put the numbers in the abstract as suggested.

2. The research objective must be clearly written in the abstract.

We have made a clear statement of the objective in the abstract.

3. As there is a lot of similar work available, the novelty of the work is not explained clearly. Emphasize what sets this study apart from existing research.

We have attempted to do this with a clearer statement at the end of the introduction, rather than putting it in the abstract and making this section over long.

4. While the introduction provides a good overview of traditional and multicomponent brass alloys, it lacks a detailed explanation of why scaling up the casting process is crucial. Elaborate on the practical implications and challenges associated with larger-scale processing.

We have added some more discussion on this part of the background.

5. The introduction part includes a short story until it comes to the main objective of this paper. It should be written with more details to make it clear and exact.

This was also commented on by another reviewer, and we have made changes to the end of the introduction to clarify the specific objectives of our work.

6. The literature review could be strengthened by integrating more recent studies on high entropy alloys (HEAs) and their scaling challenges. This would better position your work within the current research landscape and highlight its novelty.

We have searched again for reports on scale up attempts for high entropy alloys; these do not appear plentiful in the literature, but we have managed to find some examples, which we include in the literature review:

Puglielli F, Mussi V, Cugini F, Sarzi Amadè N, Solzi M, Bennati C, Fabbrici S and Albertini F (2020) Scale-Up of Magnetocaloric NiCoMnIn Heuslers by Powder Metallurgy for Room Temperature Magnetic Refrigeration. Front. Energy Res. 7:150. doi: 10.3389/fenrg.2019.00150

Kumar, J., Nayan, N., Gupta, R.K. et al. High Entropy Alloys: Laboratory to Industrial Attempt. Inter Metalcast 17, 860–873 (2023). https://doi-org.sheffield.idm.oclc.org/10.1007/s40962-022-00811-y

7. The reviewer recommends the authors to rewrite the last paragraph of the introduction section in a way to stress the novelty.

We have made significant modifications to this section to address this, and earlier comments.

8. The methodology section is detailed, but the description of the casting process could benefit from more precise information about the induction melting parameters and cooling rates. This would enhance the reproducibility of your study.

We have revised the section on the casting to supply as much information on the approach as possible  Unfortunately, the cooling rates have not been measured for this set up, but we hope that the data provided means that the work will be reproducible.

9. The criteria of materials used in this study are not explained. Provide detailed information on the selection and preparation of materials.

We have added further information to the end of the introduction and to the methodology on the reasons for selecting the present alloy for this study.

10. Please remove figures 3, 4, and 5. Other figures need to be set to higher quality, e.g., figure 7.

The required figures have been removed, and the figures following renumbered.  Figures in general have also been enhanced where possible, including adding the details requested by the earlier reviewer.

11. The discussion on hardness variability is somewhat superficial. Delve deeper into the potential causes of the observed differences, such as micro-segregation patterns and cooling rate variations, and how these factors specifically influence the mechanical properties.

We have attempted to deepen the discussion here, including referring to the suggested aspects.  Note that we have placed this in the general discussion section, rather than alongside our interpretation of these results, as it better allows the hardness to be discussed in the context of the other findings.

12. The microstructural analysis is well-presented, but the interpretation could be more nuanced. Discuss the implications of the observed dendritic and inter-dendritic structures on the alloy's performance, particularly in relation to its mechanical properties.

Thank you this is an effect that we had not previously discussed, which we have now included in the revised version of the paper.

13. The XRD phase analysis is informative, but the discussion could be expanded to compare the experimental results with theoretical predictions more thoroughly. Address any discrepancies and explore their potential causes in detail.

We have re-examined our XRD discussion.  We find that the observed phases are consistent with the expectations, both from literature results and from our own modelling.  We have in any case added to the discussion of the XRD results, but we have not observed any noteworthy differences that we are able to comment on.

14. The composition analysis shows consistency across the ingot, but the discussion on the impact of minor compositional variations on the material properties could be more detailed. Consider the role of these variations in the observed hardness differences.

We agree that this is an important aspect of the behaviour seen, and we have enhanced the discussion of this point (once again focussing this in the discussion section, rather than the interpretation of the composition results).

15. The use of Thermo-Calc software for phase predictions is a strong point, but the paper would benefit from a more detailed explanation of the non-equilibrium Scheil simulation results and their relevance to your experimental findings. Discuss how these predictions align or diverge from your observations.

Thank you; it is of course possible to make a range of interpretations from thermodynamic modelling, though it is always important to return to the comparison with experiments to validate findings.  In the current case our main use in the non-equilibrium Scheil predictions is with trying to identify the occurrence of solidification rate-driven segregation, and we have added further explanation to be clear on this point.

16. Authors are advised to draw comparisons with previous literature to justify the results.

We have tried, where possible, to refer back to relevant previous literature, though noting the comment from our response to point 6, there is it appears a rather limited array of literature in this area.

17. The conclusions are not concise. Please write the most important conclusions as brief points.

We have tried to write our conclusions in brief sentences (not quite going as far as bullet points) and to focus the section on the most important of our observations.

Reviewer 2 Report

Comments and Suggestions for Authors

The purpose of the research should be clearly expressed – at the end of introduction is the best to write it.

You need to explain why one bar is enough for your assessment.

Why did you choose the bar dimensions used in your research and not others? Does this have anything to do with the production of some components in practice?

Can you evaluate the size of the grains in all three areas of ingot?

Figure 8. All peaks should be marked with identified phases. You need to correct drawing caption.

Author Response

Casting Homogeneity of Scaled-up Multi-Principal Component Alloys, Gbenga. J. Adeyemi, C Utton, Y Azakli and R. Goodall

Response to reviewers

We thank the editorial team and reviewers for their attention to our manuscript, and apologize for the delay in completing these revisions, due to the combined effect of the Christmas vacation, and the principal author relocating to Nigeria after a research visit to the UK.  We appreciate the time taken developing the reviews, and have attempted to respond to all of the comments in this document, also indicating the changes in the manuscript in red text.

Review 1

Brief Summary

This paper investigates the casting of a Cu-Zn-Mn-Ni alloy. This study builds on previous lab scale work by assessing the impact of scale up on the developed properties. Given the properties measured there is an investigation into observed differences using modelling. Reasonable conclusions are drawn on the likely effects of micro-segregation on hardness.

General comments

The paper describes and demonstrates the issues which are associated with casting scale up. Given the reliance on the the hardness data and EDX I have two comments:

• Can there be some analysis of significance of the hardness data? A T-Test (in Excel?) would allow the reader to see how significant the differences are.

Thank you for this suggestion, which is indeed feasible with the data we have.  Performing the test gives a t-value of t(16) = 5.984, p<0.00001 when comparing middle and top datasets, and a t-value of t(16) = 5.046, p<0.00001 for the comparison between middle and bottom datasets, both of which indicate that both of these pairs are different.  On the other hand, the t-value comparing the top and bottom is only t(16) = 0.746, p=0.23045, indicating the two groups are similar.

We have included this information with the discussion of the hardness data.

2) Given the scale of the dendrite arms (5-10 microns across) it would be worth commenting on the electron interaction volume for EDX and likely sampling of different phases sub-surface. Also, as the results are quoted to 1 d.p. a standard deviation from all the readings of a particular phase in a particular layer would be helpful. For example Phase 1, upper layer Ni 26.5+/-X.Y. This would help with the significance of the differences.

Thank you; we are happy to make some comments on the interaction volume size, and the potential for this to impact on the results.  Having examined our data, we have seen that, likely by statistical chance, the low deviation in these results values, would give a value for the standard deviation that appears low.  However, we feel that it would be misleading to include this, as the number of repeat measurements we made was small, and the accuracy is likely to be more significantly limited by the fundamental accuracy of the equipment, made worse by the potential for phase overlap referred to in this comment.  For these reasons, rather than present the standard deviations in the data, we have chosen to add an enhanced discussion of the EDX data accuracy, and to reflect on this in our discussions, which essentially means that there is no conclusive evidence of macrosegregation (as we had concluded from the XRF results), with any compositional differences between the centre and the upper and lower regions being related to differences in microsegregation.

Also, given the discussion around cooling rates then the other check here would be grain size and morphology. This would be similarly impacted and give a clue to relative cooling rates. However, I do understand that this work may not have been done. Next paper?

As noted below, one of the other reviewers also commented on grain size, and we of course recognise the importance of this parameter.  We have endeavoured to include more information on this in the paper, but the number of images we have been able to take in the microscope thus far does not allow us to give this to great accuracy (we nevertheless report what we have at this time).  We will indeed seek to gain more data to facilitate a more accurate measure for future work.

Specific comments

Line 73. Discussion starts around multicomponent brasses but ref [19] is not a brass. Maybe change the word brasses to alloys?1a

Thank you, we have slightly reordered the text here to avoid this confusion.

Line 83 Conventional cast process; is this sand, metal mould, investment? For some brass castings this is plaster.

In this case this was a metal mould, and we have added this to the text

Line 82. It is not totally clear that the second sentence in the paragraph is still referring to ref [5]. It could be the start of the experimental work for this paper.

This line is indeed referring to our new experimental work, and we have reworded for clarity on this point.

Line 85. 'We estimate' could become 'it is estimated that'.

Thank you, this is changed

Line 125. Would it be possible to annotate Figure 1 with casting orientation and where the subsequent slices were taken from? Given that a 75x80x70mm block becomes a 10x15x20mm block and then becomes three slices. I am assuming that the three slices are not from the smaller block but this is not clear, hence, a request for mark-up on Figure 2.

Thank you, we have done this, and agree that it makes the description clearer.

Line 130 Check consistency of notation with line 124; 75x80x70mm vs 10mm x 15mm x 20mm.

This has been checked; the two dimensions refer to the original ingot, and then the size of the blocks that were taken from it for characterization.  We have improved the wording to make this clear.

Line 233. Any reason the plots of top, middle and bottom are drawn bottom, middle, top? Not crucial to fix.

Our apologies for this; it is somewhat confusing with the juxtaposition of the position in the figure and the position in the cast ingot.  We have moved these traces.

Review 2

The purpose of the research should be clearly expressed – at the end of introduction is the best to write it.

Apologies for not setting this out clearly originally.  We have clarified the end of the introduction to clearly focus on the purpose of the research we are describing.

You need to explain why one bar is enough for your assessment.

We agree that this is important information.  We have elected to include a statement on the reasoning behind this at the start of the section where we discuss the ingot processing, detailing the motivation and also the limitations that this decision leads to.

Why did you choose the bar dimensions used in your research and not others? Does this have anything to do with the production of some components in practice?

There is not a strong link to a particular component that made us choose the sizes that we did, it is more around the general dimensions, and the capabilities of our equipment.  We have also discussed this in the new writing at the start of the ingot processing section.

Can you evaluate the size of the grains in all three areas of ingot?

As we were not able to collect a large number of images of the grains under SEM, we had refrained from doing this.  However, we agree that this is an important measure, and useful in the current context, so we have performed this analysis, and included the data in the manuscript, along with the statistical significance.

Figure 8. All peaks should be marked with identified phases. You need to correct drawing caption.

Thank you, we have made these changes.

Review 3

The manuscript provides an experiment for Casting Homogeneity of Scaled-up Multi-Principal Component Alloys. I believe that the topic of the article is very important for many industrial applications and may be of interest to a large group of readers. Overall, I rate the article positively, but some corrections should be made before publication:

1. The abstract mentions a range of hardness values but does not specify the actual values or the extent of the variation. Including these details would provide a clearer snapshot of your findings and their significance.

Thank you for your overall positive comments.  For this specific point, we have put the numbers in the abstract as suggested.

2. The research objective must be clearly written in the abstract.

We have made a clear statement of the objective in the abstract.

3. As there is a lot of similar work available, the novelty of the work is not explained clearly. Emphasize what sets this study apart from existing research.

We have attempted to do this with a clearer statement at the end of the introduction, rather than putting it in the abstract and making this section over long.

4. While the introduction provides a good overview of traditional and multicomponent brass alloys, it lacks a detailed explanation of why scaling up the casting process is crucial. Elaborate on the practical implications and challenges associated with larger-scale processing.

We have added some more discussion on this part of the background.

5. The introduction part includes a short story until it comes to the main objective of this paper. It should be written with more details to make it clear and exact.

This was also commented on by another reviewer, and we have made changes to the end of the introduction to clarify the specific objectives of our work.

6. The literature review could be strengthened by integrating more recent studies on high entropy alloys (HEAs) and their scaling challenges. This would better position your work within the current research landscape and highlight its novelty.

We have searched again for reports on scale up attempts for high entropy alloys; these do not appear plentiful in the literature, but we have managed to find some examples, which we include in the literature review:

Puglielli F, Mussi V, Cugini F, Sarzi Amadè N, Solzi M, Bennati C, Fabbrici S and Albertini F (2020) Scale-Up of Magnetocaloric NiCoMnIn Heuslers by Powder Metallurgy for Room Temperature Magnetic Refrigeration. Front. Energy Res. 7:150. doi: 10.3389/fenrg.2019.00150

Kumar, J., Nayan, N., Gupta, R.K. et al. High Entropy Alloys: Laboratory to Industrial Attempt. Inter Metalcast 17, 860–873 (2023). https://doi-org.sheffield.idm.oclc.org/10.1007/s40962-022-00811-y

7. The reviewer recommends the authors to rewrite the last paragraph of the introduction section in a way to stress the novelty.

We have made significant modifications to this section to address this, and earlier comments.

8. The methodology section is detailed, but the description of the casting process could benefit from more precise information about the induction melting parameters and cooling rates. This would enhance the reproducibility of your study.

We have revised the section on the casting to supply as much information on the approach as possible  Unfortunately, the cooling rates have not been measured for this set up, but we hope that the data provided means that the work will be reproducible.

9. The criteria of materials used in this study are not explained. Provide detailed information on the selection and preparation of materials.

We have added further information to the end of the introduction and to the methodology on the reasons for selecting the present alloy for this study.

10. Please remove figures 3, 4, and 5. Other figures need to be set to higher quality, e.g., figure 7.

The required figures have been removed, and the figures following renumbered.  Figures in general have also been enhanced where possible, including adding the details requested by the earlier reviewer.

11. The discussion on hardness variability is somewhat superficial. Delve deeper into the potential causes of the observed differences, such as micro-segregation patterns and cooling rate variations, and how these factors specifically influence the mechanical properties.

We have attempted to deepen the discussion here, including referring to the suggested aspects.  Note that we have placed this in the general discussion section, rather than alongside our interpretation of these results, as it better allows the hardness to be discussed in the context of the other findings.

12. The microstructural analysis is well-presented, but the interpretation could be more nuanced. Discuss the implications of the observed dendritic and inter-dendritic structures on the alloy's performance, particularly in relation to its mechanical properties.

Thank you this is an effect that we had not previously discussed, which we have now included in the revised version of the paper.

13. The XRD phase analysis is informative, but the discussion could be expanded to compare the experimental results with theoretical predictions more thoroughly. Address any discrepancies and explore their potential causes in detail.

We have re-examined our XRD discussion.  We find that the observed phases are consistent with the expectations, both from literature results and from our own modelling.  We have in any case added to the discussion of the XRD results, but we have not observed any noteworthy differences that we are able to comment on.

14. The composition analysis shows consistency across the ingot, but the discussion on the impact of minor compositional variations on the material properties could be more detailed. Consider the role of these variations in the observed hardness differences.

We agree that this is an important aspect of the behaviour seen, and we have enhanced the discussion of this point (once again focussing this in the discussion section, rather than the interpretation of the composition results).

15. The use of Thermo-Calc software for phase predictions is a strong point, but the paper would benefit from a more detailed explanation of the non-equilibrium Scheil simulation results and their relevance to your experimental findings. Discuss how these predictions align or diverge from your observations.

Thank you; it is of course possible to make a range of interpretations from thermodynamic modelling, though it is always important to return to the comparison with experiments to validate findings.  In the current case our main use in the non-equilibrium Scheil predictions is with trying to identify the occurrence of solidification rate-driven segregation, and we have added further explanation to be clear on this point.

16. Authors are advised to draw comparisons with previous literature to justify the results.

We have tried, where possible, to refer back to relevant previous literature, though noting the comment from our response to point 6, there is it appears a rather limited array of literature in this area.

17. The conclusions are not concise. Please write the most important conclusions as brief points.

We have tried to write our conclusions in brief sentences (not quite going as far as bullet points) and to focus the section on the most important of our observations.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript provides an experiment for Casting Homogeneity of Scaled-up Multi-Principal Component Alloys. I believe that the topic of the article is very important for many industrial applications and may be of interest to a large group of readers. Overall, I rate the article positively, but some corrections should be made before publication:

1. The abstract mentions a range of hardness values but does not specify the actual values or the extent of the variation. Including these details would provide a clearer snapshot of your findings and their significance.
2. The research objective must be clearly written in the abstract.
3. As there is a lot of similar work available, the novelty of the work is not explained clearly. Emphasize what sets this study apart from existing research.
4. While the introduction provides a good overview of traditional and multicomponent brass alloys, it lacks a detailed explanation of why scaling up the casting process is crucial. Elaborate on the practical implications and challenges associated with larger-scale processing.
5. The introduction part includes a short story until it comes to the main objective of this paper. It should be written with more details to make it clear and exact.
6. The literature review could be strengthened by integrating more recent studies on high entropy alloys (HEAs) and their scaling challenges. This would better position your work within the current research landscape and highlight its novelty.
7. The reviewer recommends the authors to rewrite the last paragraph of the introduction section in a way to stress the novelty.
8. The methodology section is detailed, but the description of the casting process could benefit from more precise information about the induction melting parameters and cooling rates. This would enhance the reproducibility of your study.
9. The criteria of materials used in this study are not explained. Provide detailed information on the selection and preparation of materials.
10. Please remove figures 3, 4, and 5. Other figures need to be set to higher quality, e.g., figure 7.
11. The discussion on hardness variability is somewhat superficial. Delve deeper into the potential causes of the observed differences, such as micro-segregation patterns and cooling rate variations, and how these factors specifically influence the mechanical properties.
12. The microstructural analysis is well-presented, but the interpretation could be more nuanced. Discuss the implications of the observed dendritic and inter-dendritic structures on the alloy's performance, particularly in relation to its mechanical properties.
13. The XRD phase analysis is informative, but the discussion could be expanded to compare the experimental results with theoretical predictions more thoroughly. Address any discrepancies and explore their potential causes in detail.
14. The composition analysis shows consistency across the ingot, but the discussion on the impact of minor compositional variations on the material properties could be more detailed. Consider the role of these variations in the observed hardness differences.
15. The use of Thermo-Calc software for phase predictions is a strong point, but the paper would benefit from a more detailed explanation of the non-equilibrium Scheil simulation results and their relevance to your experimental findings. Discuss how these predictions align or diverge from your observations.
16. Authors are advised to draw comparisons with previous literature to justify the results.
17. The conclusions are not concise. Please write the most important conclusions as brief points.

Author Response

Casting Homogeneity of Scaled-up Multi-Principal Component Alloys, Gbenga. J. Adeyemi, C Utton, Y Azakli and R. Goodall

Response to reviewers

We thank the editorial team and reviewers for their attention to our manuscript, and apologize for the delay in completing these revisions, due to the combined effect of the Christmas vacation, and the principal author relocating to Nigeria after a research visit to the UK.  We appreciate the time taken developing the reviews, and have attempted to respond to all of the comments in this document, also indicating the changes in the manuscript in red text.

Review 1

Brief Summary

This paper investigates the casting of a Cu-Zn-Mn-Ni alloy. This study builds on previous lab scale work by assessing the impact of scale up on the developed properties. Given the properties measured there is an investigation into observed differences using modelling. Reasonable conclusions are drawn on the likely effects of micro-segregation on hardness.

General comments

The paper describes and demonstrates the issues which are associated with casting scale up. Given the reliance on the the hardness data and EDX I have two comments:

• Can there be some analysis of significance of the hardness data? A T-Test (in Excel?) would allow the reader to see how significant the differences are.

Thank you for this suggestion, which is indeed feasible with the data we have.  Performing the test gives a t-value of t(16) = 5.984, p<0.00001 when comparing middle and top datasets, and a t-value of t(16) = 5.046, p<0.00001 for the comparison between middle and bottom datasets, both of which indicate that both of these pairs are different.  On the other hand, the t-value comparing the top and bottom is only t(16) = 0.746, p=0.23045, indicating the two groups are similar.

We have included this information with the discussion of the hardness data.

2) Given the scale of the dendrite arms (5-10 microns across) it would be worth commenting on the electron interaction volume for EDX and likely sampling of different phases sub-surface. Also, as the results are quoted to 1 d.p. a standard deviation from all the readings of a particular phase in a particular layer would be helpful. For example Phase 1, upper layer Ni 26.5+/-X.Y. This would help with the significance of the differences.

Thank you; we are happy to make some comments on the interaction volume size, and the potential for this to impact on the results.  Having examined our data, we have seen that, likely by statistical chance, the low deviation in these results values, would give a value for the standard deviation that appears low.  However, we feel that it would be misleading to include this, as the number of repeat measurements we made was small, and the accuracy is likely to be more significantly limited by the fundamental accuracy of the equipment, made worse by the potential for phase overlap referred to in this comment.  For these reasons, rather than present the standard deviations in the data, we have chosen to add an enhanced discussion of the EDX data accuracy, and to reflect on this in our discussions, which essentially means that there is no conclusive evidence of macrosegregation (as we had concluded from the XRF results), with any compositional differences between the centre and the upper and lower regions being related to differences in microsegregation.

Also, given the discussion around cooling rates then the other check here would be grain size and morphology. This would be similarly impacted and give a clue to relative cooling rates. However, I do understand that this work may not have been done. Next paper?

As noted below, one of the other reviewers also commented on grain size, and we of course recognise the importance of this parameter.  We have endeavoured to include more information on this in the paper, but the number of images we have been able to take in the microscope thus far does not allow us to give this to great accuracy (we nevertheless report what we have at this time).  We will indeed seek to gain more data to facilitate a more accurate measure for future work.

Specific comments

Line 73. Discussion starts around multicomponent brasses but ref [19] is not a brass. Maybe change the word brasses to alloys?1a

Thank you, we have slightly reordered the text here to avoid this confusion.

Line 83 Conventional cast process; is this sand, metal mould, investment? For some brass castings this is plaster.

In this case this was a metal mould, and we have added this to the text

Line 82. It is not totally clear that the second sentence in the paragraph is still referring to ref [5]. It could be the start of the experimental work for this paper.

This line is indeed referring to our new experimental work, and we have reworded for clarity on this point.

Line 85. 'We estimate' could become 'it is estimated that'.

Thank you, this is changed

Line 125. Would it be possible to annotate Figure 1 with casting orientation and where the subsequent slices were taken from? Given that a 75x80x70mm block becomes a 10x15x20mm block and then becomes three slices. I am assuming that the three slices are not from the smaller block but this is not clear, hence, a request for mark-up on Figure 2.

Thank you, we have done this, and agree that it makes the description clearer.

Line 130 Check consistency of notation with line 124; 75x80x70mm vs 10mm x 15mm x 20mm.

This has been checked; the two dimensions refer to the original ingot, and then the size of the blocks that were taken from it for characterization.  We have improved the wording to make this clear.

Line 233. Any reason the plots of top, middle and bottom are drawn bottom, middle, top? Not crucial to fix.

Our apologies for this; it is somewhat confusing with the juxtaposition of the position in the figure and the position in the cast ingot.  We have moved these traces.

Review 2

The purpose of the research should be clearly expressed – at the end of introduction is the best to write it.

Apologies for not setting this out clearly originally.  We have clarified the end of the introduction to clearly focus on the purpose of the research we are describing.

You need to explain why one bar is enough for your assessment.

We agree that this is important information.  We have elected to include a statement on the reasoning behind this at the start of the section where we discuss the ingot processing, detailing the motivation and also the limitations that this decision leads to.

Why did you choose the bar dimensions used in your research and not others? Does this have anything to do with the production of some components in practice?

There is not a strong link to a particular component that made us choose the sizes that we did, it is more around the general dimensions, and the capabilities of our equipment.  We have also discussed this in the new writing at the start of the ingot processing section.

Can you evaluate the size of the grains in all three areas of ingot?

As we were not able to collect a large number of images of the grains under SEM, we had refrained from doing this.  However, we agree that this is an important measure, and useful in the current context, so we have performed this analysis, and included the data in the manuscript, along with the statistical significance.

Figure 8. All peaks should be marked with identified phases. You need to correct drawing caption.

Thank you, we have made these changes.

Review 3

The manuscript provides an experiment for Casting Homogeneity of Scaled-up Multi-Principal Component Alloys. I believe that the topic of the article is very important for many industrial applications and may be of interest to a large group of readers. Overall, I rate the article positively, but some corrections should be made before publication:

1. The abstract mentions a range of hardness values but does not specify the actual values or the extent of the variation. Including these details would provide a clearer snapshot of your findings and their significance.

Thank you for your overall positive comments.  For this specific point, we have put the numbers in the abstract as suggested.

2. The research objective must be clearly written in the abstract.

We have made a clear statement of the objective in the abstract.

3. As there is a lot of similar work available, the novelty of the work is not explained clearly. Emphasize what sets this study apart from existing research.

We have attempted to do this with a clearer statement at the end of the introduction, rather than putting it in the abstract and making this section over long.

4. While the introduction provides a good overview of traditional and multicomponent brass alloys, it lacks a detailed explanation of why scaling up the casting process is crucial. Elaborate on the practical implications and challenges associated with larger-scale processing.

We have added some more discussion on this part of the background.

5. The introduction part includes a short story until it comes to the main objective of this paper. It should be written with more details to make it clear and exact.

This was also commented on by another reviewer, and we have made changes to the end of the introduction to clarify the specific objectives of our work.

6. The literature review could be strengthened by integrating more recent studies on high entropy alloys (HEAs) and their scaling challenges. This would better position your work within the current research landscape and highlight its novelty.

We have searched again for reports on scale up attempts for high entropy alloys; these do not appear plentiful in the literature, but we have managed to find some examples, which we include in the literature review:

Puglielli F, Mussi V, Cugini F, Sarzi Amadè N, Solzi M, Bennati C, Fabbrici S and Albertini F (2020) Scale-Up of Magnetocaloric NiCoMnIn Heuslers by Powder Metallurgy for Room Temperature Magnetic Refrigeration. Front. Energy Res. 7:150. doi: 10.3389/fenrg.2019.00150

Kumar, J., Nayan, N., Gupta, R.K. et al. High Entropy Alloys: Laboratory to Industrial Attempt. Inter Metalcast 17, 860–873 (2023). https://doi-org.sheffield.idm.oclc.org/10.1007/s40962-022-00811-y

7. The reviewer recommends the authors to rewrite the last paragraph of the introduction section in a way to stress the novelty.

We have made significant modifications to this section to address this, and earlier comments.

8. The methodology section is detailed, but the description of the casting process could benefit from more precise information about the induction melting parameters and cooling rates. This would enhance the reproducibility of your study.

We have revised the section on the casting to supply as much information on the approach as possible  Unfortunately, the cooling rates have not been measured for this set up, but we hope that the data provided means that the work will be reproducible.

9. The criteria of materials used in this study are not explained. Provide detailed information on the selection and preparation of materials.

We have added further information to the end of the introduction and to the methodology on the reasons for selecting the present alloy for this study.

10. Please remove figures 3, 4, and 5. Other figures need to be set to higher quality, e.g., figure 7.

The required figures have been removed, and the figures following renumbered.  Figures in general have also been enhanced where possible, including adding the details requested by the earlier reviewer.

11. The discussion on hardness variability is somewhat superficial. Delve deeper into the potential causes of the observed differences, such as micro-segregation patterns and cooling rate variations, and how these factors specifically influence the mechanical properties.

We have attempted to deepen the discussion here, including referring to the suggested aspects.  Note that we have placed this in the general discussion section, rather than alongside our interpretation of these results, as it better allows the hardness to be discussed in the context of the other findings.

12. The microstructural analysis is well-presented, but the interpretation could be more nuanced. Discuss the implications of the observed dendritic and inter-dendritic structures on the alloy's performance, particularly in relation to its mechanical properties.

Thank you this is an effect that we had not previously discussed, which we have now included in the revised version of the paper.

13. The XRD phase analysis is informative, but the discussion could be expanded to compare the experimental results with theoretical predictions more thoroughly. Address any discrepancies and explore their potential causes in detail.

We have re-examined our XRD discussion.  We find that the observed phases are consistent with the expectations, both from literature results and from our own modelling.  We have in any case added to the discussion of the XRD results, but we have not observed any noteworthy differences that we are able to comment on.

14. The composition analysis shows consistency across the ingot, but the discussion on the impact of minor compositional variations on the material properties could be more detailed. Consider the role of these variations in the observed hardness differences.

We agree that this is an important aspect of the behaviour seen, and we have enhanced the discussion of this point (once again focussing this in the discussion section, rather than the interpretation of the composition results).

15. The use of Thermo-Calc software for phase predictions is a strong point, but the paper would benefit from a more detailed explanation of the non-equilibrium Scheil simulation results and their relevance to your experimental findings. Discuss how these predictions align or diverge from your observations.

Thank you; it is of course possible to make a range of interpretations from thermodynamic modelling, though it is always important to return to the comparison with experiments to validate findings.  In the current case our main use in the non-equilibrium Scheil predictions is with trying to identify the occurrence of solidification rate-driven segregation, and we have added further explanation to be clear on this point.

16. Authors are advised to draw comparisons with previous literature to justify the results.

We have tried, where possible, to refer back to relevant previous literature, though noting the comment from our response to point 6, there is it appears a rather limited array of literature in this area.

17. The conclusions are not concise. Please write the most important conclusions as brief points.

We have tried to write our conclusions in brief sentences (not quite going as far as bullet points) and to focus the section on the most important of our observations.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The paper is revised accordingly and can be accepted for publication.