Direct Observation of Cu Clusters and Dislocation Loops by Cs-Corrected STEM in Fe-0.6wt%Cu Alloy Irradiated in BR2

Round 1

Reviewer 1 Report

In this manuscript, the authors described an effort to characterize neutron irradiation effects in Fe-Cu alloys, paying particular attentions to Cu precipitations and dislocation loops. The manuscript contains very valuable information such as neutron irradiation effects after BR2 in-pile irradiation and hardening of the materials after irradiation, and therefore should be published. However, the authors can do much better in the way of presenting these results. Here are some suggestions to improve the overall quality of the manuscript:

1. The quality of tables and figures can be improved. Please use a consistent form to present the tables and consider to enhance the contrast and quality of the figures.
2. The manuscript is very well oriented for readers who are very familiar with TEM characterizations, but not that friendly for those who are not very familiar with such technique. So, it is recommended that the authors spend more time to explain some detailed information regarding TEM, for example, why do the black dots represent dislocation loops? why do the extra spots in the diffraction pattern in Fig 3.b correspond to Cu precipitates?
3. In Fig. 4 the authors marked quite a number of dislocation loops in the figure at the earliest time of electron irradiation, but did not mark all corresponding loops when time is evolved. It is recommended that the authors clearly mark all these loops so to arrive at the conclusion on the interstitial nature of the loops. And by the way, there are also loop like structures whose contrast seem to diminish, making one feel like there are loops that might be shrinking. Please clearly explain all contrast changes on things that may look like a loop, otherwise the judgement on the nature of the loops may not be as solid.
4. The authors need to be a little more specific about the location relationships between loops and Cu precipitates in Fig. 8. The current description does not seem to come through easily.
5. Please make equation 1 better edible than its current form.

Author Response

Please see the attachment. Thank you.   Watanabe

Author Response File: Author Response.pdf

Reviewer 2 Report

As the author believes, the mechanical properties of metal materials under irradiation is an important issue for nuclear reactor safety. Generally, irradiation damage can dramatically affect the microstructure evolution and mechanical behaviour of metall materials, including the generation of defect clusters and the increase of yield stress, reduction of ductility, etc. In this manuscript, neutron irradiation was conducted in BR2 at 290°C for an Fe-0.6wt%Cu alloy. Further, dislocation loops and CRPs were observed and analyzed by Cs-corrected TEM and STEM-EDS. However, these similar results have been described in many previously published articles. In general, the above experimental results do not provide other interesting results and related physical mechanisms, and this manuscript is not innovative. For these reasons I recommend the editor not publish the submission.

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors and Editors,

Here are my questions & comments regarding the manuscript:

• Abstract section does not provide highlights, important data or summary but rather seems to be a part of Experimental section. Maybe it should be revised so that the main ideaof the manuscript could be more understandable for the readers. 
• The Introduction section lacks references, technological context and broad overview of the discussed problems and properties. Its last paragraph, in my opinion, should be also moved to the Experimental section. 
• Tables 1 and 2 are written not in unique format, table 2 has no capture, and the footnotes are written so that the tables are pasted from another manuscript (in this case there is no reference for the previous works).
• Line 86:  at an HVEM in the HVEM Laboratory - maybe there is  unnecessary repetition.
• Fig. 2 Do all figures a-d have the same scale?
• The results section represents a list of figures just one by one with practically no analysis, comparison, discussion and so on. Discussion section also does not contain any citation of the figures from the results section in order to make some summarization, comparison or ana other type of analysis. 
• Conclusions section is also very brief and short and does not provide sufficient summarization of the obtained results and highlights that could be useful for the readers. 

Author Response

Please see the attachment. Thank you.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Compared with previous studies, this manuscript mainly characterized small clusters (such as very small CRPs and dislocation loops) based on Cs-corrected STEM with EDS. In this manuscript, the authors indicate that the size of CRP is about 10 nm. However, as far as the reviewers know, very small (1-3 nm) precipitation can be characterized by atom probe tomography (e.g., Kuksenko V., et al., J. Nucl. Mater. 2013, 432:160-165; Shu et al., Acta Mater. 2018, 146:237-252). So, how small defects can Cs-corrected STEM with EDS measure? What are the specific advantages over other technologies?

Author Response

Thank you. Please see the attachment.

Watanabe Hideo/Kyushu Univ., Japan

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors and Editors,

1. The comments and changes to the manuscipt performed by the authors are rather brief, however they could be considered as appropriate and sufficient. 

2. Table 1 lacks spece symbols between the composition values and element symbols.

Author Response

Thank you for your comments.

Some spaces were inserted between composition values and element symbols.

Thank you again.       Watanabe Hideo/Kyushu Univ.