Effects of Alloying Elements on the Stacking Fault Energies of Ni58Cr32Fe10 Alloys: A First-Principle Study
Round 1
Reviewer 1 Report
The manuscript deals with ab initio determination of the stacking fault energy in NiCrFe-based alloys. I have a few observations which must be addressed before the manuscript is considered for publication. Calculations are carried out at static conditions and include magnetic entropy as the sole thermal effect. Although this is quite common, perhaps some discussion of the missing terms is needed. The static (chemical) SFE corresponds to 0 K theoretical volume. To my understanding, this term is not recalculated for different volumes when considering the effect of thermal expansion. Why? Another question is the magnetic order. What is the ordering temperature of the present alloys? If there are no experimental data, the authors should use mean field estimate to see the level of Tc and how that is affected by temperature. This is crucial to be able to discuss the importance of DLM versus ordered magnetic state. Third, the present DLM adopts a static picture, meaning that no thermal spin fluctuations are taken into account. Although such effects might be minor in the present alloy, it is clear that they are responsible for getting magnetic moment only on Fe atoms in all three structures. Some discussion is needed here as well. Finally, the presentation and language should be improved.
Author Response
Dear professor,
Thank you so much for your constructive advices on my manuscript. We have read your advices very carefully. Many changes, colored in green, have been made in the revised manuscript.
The manuscript deals with ab initio determination of the stacking fault energy in NiCrFe-based alloys. I have a few observations which must be addressed before the manuscript is considered for publication.
Calculations are carried out at static conditions and include magnetic entropy as the sole thermal effect. Although this is quite common, perhaps some discussion of the missing terms is needed.
Response: Thank you for this advice. The following statement was added into the revised manuscript. Page 5 line 158-161.
"It has been demonstrated that the contributions of electronic entropy and phonon were demonstrated relatively small. Although electronic entropy and phonon do influence the SFEs, the computational errors can be cancelled to some extent due to the same group cells being used."
The static (chemical) SFE corresponds to 0 K theoretical volume. To my understanding, this term is not recalculated for different volumes when considering the effect of thermal expansion. Why?
Response: Thank you for this advice. The following statement was added into the revised manuscript to avoid confusion. Page 5 line 161-166.
" For all of the systems considered in this study, we re-calculated the SFE0 with thermal expanded cells. The influence of thermal expansion on the SFE0 is very small (for all of the systems, the influence is smaller than 0.3 mJm-2). Although thermal expansions do increase the energy of cells, the energy difference between fcc, hcp and dhcp structures keep almost unchanged. Thus, only the SFEs0 at 0 K were listed in table 2 and were used in the following discussions. "
Another question is the magnetic order. What is the ordering temperature of the present alloys? If there are no experimental data, the authors should use mean field estimate to see the level of Tc and how that is affected by temperature. This is crucial to be able to discuss the importance of DLM versus ordered magnetic state.
Response: We are sorry for our careless.
The critical temperature for alloy 690 is 370K [34]. Considering that DDC is a high-temperature phenomenon, it is reasonable to discuss the SFEs within the DLM scheme.
This statement was added into the revised manuscript. Page2- 3 line 90-92.
Moreover, reference [34] was added into the revised manuscript.
[34] Lemire, R. J. McRae, G. A. "The corrosion of Alloy 690 in high-temperature aqueous media – thermodynamic considerations." Journal of Nuclear Materials 294, no. 1 (2001): 141-47
Third, the present DLM adopts a static picture, meaning that no thermal spin fluctuations are taken into account. Although such effects might be minor in the present alloy, it is clear that they are responsible for getting magnetic moment only on Fe atoms in all three structures. Some discussion is needed here as well.
Response: Thank you for this advice. The following statement was added into the revised manuscript. Page 6 line 218-221.
"It should be noted that DLM adopts a static picture, meaning that no thermal spin fluctuations are taken into account. However, it is suggested that the computational errors could be cancelled to some extent due to the same group of cells being used."
Finally, the presentation and language should be improved.
Response: We are regret to the English. Many mistakes were removed in the revised manuscript.
Thank you again for your help.
Best wishes,
Yuchen Dou
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This study aims to understand an effect of alloying element on stacking fault energy in Ni58Cr32Fe10 alloy by first principle calculation. However, I regret to say that this paper does not merit for publication in Metals due to mainly the following reasons. For accepting this article in the future, I think the paper strategy should be changed.
1. There are many spell misses in this article. It degrades the reliability of this article.
2. The authors consider that decreasing SFE likely improve ductility. However, in general decreasing SFE leads cross-slip more difficult at grain boundaries, which result in easier formation of voids at grain boundaries due to strain localization. It seems hard for me to understand deterioration in ductility occurs due to only SFE.
3. As authors also comment in their literature, ductility is not only function of SFE, but also grain size, grain boundary segregation, stress-strain trade-off balance etc. So, it is hard to accept this study’s purpose in the relation with ductility of the alloy.
4. In this article A(angstrom) unit is used. But I would like to suggest to use Si unit instead.
Author Response
Dear professor,
Thank you so much for your constructive advices on my manuscript. We have read your advices very carefully. Many changes, colored in green, have been made in the revised manuscript.
1. There are many spell misses in this article. It degrades the reliability of this article.
Response: We are regret to the spell mistakes. Many spell mistakes were removed in the revised manuscript.
2. The authors consider that decreasing SFE likely improve ductility. However, in general decreasing SFE leads cross-slip more difficult at grain boundaries, which result in easier formation of voids at grain boundaries due to strain localization. It seems hard for me to understand deterioration in ductility occurs due to only SFE.
Response: We particularly thank you for this comment and we are so regret for our ambiguous description of the relationship between SFE and DDC. The ambiguous description could get the readers confused.
Yes, you are right. "Decreasing SFE leads cross-slip more difficult…..."
Fundamentally, DDC is a solid-state intergranular hot cracking phenomenon caused by local exhaustion of ductility at stress concentrated area. A more homogeneous deformation process (or a more homogeneous distribution of dislocations) is required to achieve a better DDC resistance.
"It should be pointed out that decreasing the SFE may not increase the global ductility (or macro ductility) but may leads to a more homogeneous distribution of dislocations. "
The above statement was added to avoid confusion. Page 2 line 50-52
3. As authors also comment in their literature, ductility is not only function of SFE, but also grain size, grain boundary segregation, stress-strain trade-off balance etc. So, it is hard to accept this study’s purpose in the relation with ductility of the alloy.
Response: We are sorry again for the ambiguous description of the relationship between SFE and DDC.
"It should be pointed out that decreasing the SFE may not increase the global ductility (or macro ductility) but could potentially leads to a more homogeneous distribution of dislocations."
The above statement was added into the conclusions section. Page 7 line 233-235
4. In this article A(angstrom) unit is used. But I would like to suggest to use Si unit instead.
Response: A(angstrom) is changed into 10-10m3.
Thank you again for your help.
Best wishes,
Yuchen Dou
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Please revise the manuscript, there are some language mistakes. E.g. "It has been demonstrated that the contributions of electronic entropy and phonon were demonstrated relatively small."
Furthermore, neglecting the thermal spin fluctuations does not mean "computational errors". It is an approximation. Please revise this part as well and give references for spin fluctuations in multicomponent alloys (otherwise the reader might not know what you mean here).
Otherwise this is a good contribution that after the minor corrections can be published.
Author Response
Dear professor,
Thank you so much for your help on my manuscript. We have read your advices very carefully. Many changes, colored in green, have been made in the revised manuscript.
Please revise the manuscript, there are some language mistakes. E.g. "It has been demonstrated that the contributions of electronic entropy and phonon were demonstrated relatively small."
Response: We are so regret for this mistake. In the revised manuscript this mistake and are removed. "Researchers have demonstrated that the contributions of electronic entropy and phonon were demonstrated relatively small."
Furthermore, neglecting the thermal spin fluctuations does not mean "computational errors". It is an approximation. Please revise this part as well and give references for spin fluctuations in multicomponent alloys (otherwise the reader might not know what you mean here).
Response: Thank you so much for this constructive advice.
Discussions on the spin fluctuations were updated as the following:
"It should be noted that DLM adopts a static picture, meaning that no thermal spin fluctuations are taken into account. As a consequence, local magnetic moments mainly survive on Fe atom. It is well known that the local magnetic moments in Cr, and Ni survive in their high-temperature paramagnetic states when spin fluctuations were taken into account [41-43]. Fortunately, Dong et al demonstrated that spin fluctuations give limited influence on the SFE [43]."
Three references were added into the revised manuscript.
Dong, Zhihua, Stephan Schönecker, Dengfu Chen, Wei Li, Mujun Long, and Levente Vitos. "Elastic Properties of Paramagnetic Austenitic Steel at Finite Temperature: Longitudinal Spin Fluctuations in Multicomponent Alloys." Physical Review B 96, no. 17 (2017): 174415. Dong, Zhihua, Wei Li, Stephan Schönecker, Song Lu, Dengfu Chen, and Levente Vitos. "Thermal Spin Fluctuation Effect on the Elastic Constants of Paramagnetic Fe from First Principles." Physical Review B 92, no. 22 (2015): 224420. Dong, Zhihua, Stephan Schönecker, Wei Li, Dengfu Chen, and Levente Vitos. "Thermal Spin Fluctuations in Cocrfemnni High Entropy Alloy." Scientific Reports 8, no. 1 (2018): 12211.
Thank you again for your help.
Best wishes,
Yuchen Dou
Reviewer 2 Report
figure 3 --> Figure 3
table 3 --> Table 3
Author Response
Dear professor,
Thank you so much for your help on my manuscript. We have read your advices very carefully. Many changes, colored in green, have been made in the revised manuscript.
figure 3 --> Figure 3
table 3 --> Table 3
Response: Thank you for your help on my manuscript.
figure 3 has been changed into Figure 3. Line 207, 214
table 3 has been changed into Table 3. Line 172
Thank you again for your help.
Best wishes,
Yuchen Dou
