Microscopic Phase-Field Simulation of γ′ Precipitation in Ni-Based Binary Alloys Coupled with CALPHAD Method
Round 1
Reviewer 1 Report
In Ni-base superalloys, coherency strains are known to be important. More justification for neglecting elastic stress effects is needed.
Further, 3D modelling of microstructural evolution is also not uncommon. So, it is not clear why the authors have not tried 3D modelling. There is a mention of computational intensity. Are 3D models prohibitively costly? It is not clear.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this work, the authors couple a mean-field model with the Calphad method to calculate the first and second nearest neighbour interaction energies. The ordering and clustering behaviours are also simulated using a kinetic model. However, there are several aspects that need to be clarified and elaborated upon before this article can be considered for publication.
1. There is very little discussion of the results. The following aspects need to be addressed:
(a) What are the advantages and limitations of using this method?
(b) What are the main assumptions? (this needs to be added in the methodology itself)
(c) Is there experimental evidence to support the key results about ordering? If not, can the authors suggest some experiments?
(d) Can the approach be extended for ternary and multicomponent systems?
2. The methodology description is not detailed enough:
(a) no reference is mentioned for Equation 10 or 11
(b) the form of the noise term in Eq. 10 is not mentioned
(c) In Equation 11, how exactly is P_u^alpha(i,j) calculated? Does 'around the (i,j) lattice site' mean the average of the nearest neighbouring lattice sites? Also, P(i,j) is not defined at all.
3. The notations used are very confusing:
(a) many 'k's are defined which refer to different quantities
(b) use of c_a, c_b, etc. for compositions at different temperatures
(c) V^1, V^2, V(0), V(k)
More uniform and systematic notations are required for all the above.
4. In Figure 5, what does 'distance' refer to on the x-axis? The legends for corner and face sites seem to be switched on Figure 5.
5. Are the results concerning the occupation probability of the corner and face sites meant as a validation or is it a prediction from the model? That is, has this already been observed in experiments and the simulations reflect the same?
6. There is a sentence 'Subsequently, the gamma phase begins to disappear and is replaced by a larger domain'. This observation is not clear from the figures. Could the authors explain what is meant here?
7. Finally, the novelty of this work is not clear. Has this approach been attempted before? If yes, then the significance of the present study needs to be established clearly.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
This paper provides a framework to couple CALPHAD with microscopic phase-filed models to determine the first and second nearest-neighbor interaction energies for simulating the γ’ morphological evolution in binary alloys. The paper has been written with a reasonably good structure. However, several major issues are to be addressed by the authors, before this paper can be recommended for publication.
1. In Lines 55-56, the authors have mentioned that “For simplicity, the effect of elastic strain energy on the two-phase morphology is ignored”. The authors need to explain what the effect of elastic strain energy on the morphology is and how ignoring this will affect it.
2. In Line 109-110, it has been mentioned that “V1 and V2 are named in the follow, respectively”. This phrase is not correct and needs to be modified.
3. In Figure 2, the alloy name needs to be specified for each sub-figure for better clarity.
4. In Figure 2, the value of V1 is positive while V2 is negative for all the binary alloys. Why?
5. In Line 128, the reference format for [8] is wrong.
6. In Line 134, it has been mentioned that the main concentration of the solute atom in the alloy is c0=0.175. How was this value chosen? Please include an explanation. Also the unit for the composition is missing which needs to be included.
7. In Line 139, the phrase “grid is a mixture of white and other” needs to be corrected.
8. In Figure 4, the t* value for each image and the alloy system corresponding to each row of subfigures needs to be added for better clarity.
9. The authors need to add an explanation for why different times were chosen (1574 K for Ni-Al, 686 K for Ni-Fe etc.) for each row of subfigures in Figure 4.
10. The alloy system corresponding to each subfigure needs to be mentioned in Figure 5 for better clarity.
11. The conclusions need to be more quantitative based on the results obtained in this work.
12. Titanium is an important alloying element which will influence the γ’ precipitation behavior in Ni-based alloys. Why this element was not considered in this work.
13. Although binary Ni alloys are considered in this work, mixing of different alloying elements in the X site of Ni3X precipitate is also expected. However, there is no mention about this in this work.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Most of the comments have been addressed by the authors. However, more changes in the manuscript are required addressing those comments.
1. The response from the authors to questions 1.c) and d) from my first report must be included in the manuscript also.
2. Figure 5 legends are still incorrect - face and corner sites legends seem to be switched.
3. Responses to questions 5 and 7 from my first report must also be incorporated in the manuscript (5 in the discussion and 7 in the introduction, stating the novelty clearly)
4. In the revised manuscript, in the first point in the conclusion, the term 'interaction energies' can be mentioned along with V^1_alphabeta, V^2_alphabeta .
5. English language editing is required in several places.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The manuscript can be accepted in the current form for publications since all the comments have been addressed.
Author Response
Thank you for your kind cooperation.
