Study on Hot Deformation Behavior and Texture Evolution of Aluminum Alloy 7075 Based on Visco-Plastic Self-Consistent Model
Round 1
Reviewer 1 Report (New Reviewer)
In the paper "Study on Hot deformation behavior and texture Evolution of Aluminum Alloy 7075 based on Visco-plastic self-consistent Model", the authors have investigated hot deformation behaviour of the aluminium alloy using improved visco-plastic self-consistent (VPSC) model. The constructed model shows a good accordance between predicted results of the improved VPSC model and the experimental findings. The presented results seem to be interesting. However, some parts of the manuscript are needed to be modified accordingly following comments:
1. The most of the cited references is too old. It is recommended to consider the ore last references devoted to the hot deformation and processing mapping of the Al-Zn-Mg alloys (e.g., 10.1016/j.jallcom.2022.163690, 10.3390/app11104587, etc).
2. The first and second conclusions provide well-known information about hot deformation behaviour of metallic materials. The conclusions should be removed from the text. Other conclusions should be significantly reduced and should provide only the main findings.
3. Unfortunately, the paper lacks any statistical analysis of the measured characteristics (e.g. the for partition fraction of the different texture components in Table 5). It does not let to recognize the significance of the difference between values.
4. It is unclear how were obtained the values of the elastic tensor (Eq. 12). Why did the authors use constant values for all considered temperatures? It is known that the elastic modulus is significantly decreases with temperature increase.
5. The texture of the most grains in Figure 7c is not recognized. Only 24 % of the microstructure were analyzed. The provided values in Table 5 mean that the same situation is also for deformed samples. It makes overall analysis incorrect. The crystal orientation distributions of the deformed samples should be included to the manuscript.
Author Response
The author is very grateful for these professional comments on the manuscript. The author has revised the article in detail according to the reviewer's opinions, and the response letter has been uploaded to the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (New Reviewer)
Quite good paper. Major revisions are in order for the authors to address the comments detailed in the points below:
“The friction force causes the sample to deform unevenly during hot compression”: can this be predicted?
“The difference caused by the linearization method is mainly reflected in the treatment of the interaction tensor, and the self-consistent results obtained by different linearization methods are different”: more details on this is necessary please.
“The current linearization methods include Secant, Affine, Tangent, and Meff.”: what is this?
“The results show that the change of deformation conditions will lead to significant changes in flow stress”. But was already expected correct?
“This may be due to the fact that the formation of dynamic recrystallization is a thermal activation process”: was this evaluated somehow?
“When the material is heated at low heating rate, the material has enough time for dynamic recovery and dynamic recrystallization during the heating pro”: what is the threshold for low or high heating rate in this case? Detail please.
Have the authors checked the KAM maps? Any meaningful changes?
Author Response
The author is very grateful for these professional comments on the manuscript.The author has revised the article in detail according to the opinions of the reviewer, and the response letter has been uploaded to the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report (New Reviewer)
The authors have answered previous comments and significantly improved the manuscript. The paper may be accepted for publication.
Reviewer 2 Report (New Reviewer)
Accept
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The paper presents an experimental and computational study of the (deformation) texture evolution during various hot compression (strain, strain rate and temperature) conditions of an AA7075 aluminium alloy. The texture evolution was characterized by the EBSD technique, and the data analysis was made by combining the use of TSL-OIM, Matlab and the MTEX software. The experimental textures were compared with the texture predictions by the Visco-plastic self-consistent model (VPSC). The motivation was to test the applicability and validity of the VPSC model to predict the texture evolution for the material and processing conditions investigated.
The paper presents a large number of experimental results and related simulation results, which seem mainly well conducted and presented. However, I do question the novelty of the results presented, and moreover, the paper has some obvious weaknesses and is clearly not satisfactory in several respects, including the fact that important information and results are not included.
The initial material already has a distinct microstructure and texture (Fig. 5 and 7) and must have been subject to some pre-processing (deformation process ?) that is not described at all. However, this information can be important for the subsequent processing and analysis and understanding of the results and should therefore be included.
I take it for granted that it is the initial texture given in Fig. 6 that is used as the starting texture for the VPSC texture predictions?
In this context it would have been useful and important to include a grain structure micrograph of the initial structure to show what type of grain structure this is (e.g. fibrous, partially or fully recrystallized) – difficult to judge only from Fig. 5 and 7.
The authors also discuss their results in terms of the microstructure evolution (sec. 4.3. and 4.4) and even refer to results in Sec. 4.4. about the microstructure evolution, which are not shown (Sec. 4.4:. Based on the analysis of grain size and orientation difference angle, it is found that the effect of dynamic recovery and dynamic recrystallization composite softening mechanism becomes more evident with increasing temperature, the proportion of grain boundary with slight angle gradually decreases, and the proportion of large grain size, which is higher than the average grain size, gradually increases). Here both grain structure micrographs and corresponding results to Fig. 7 are missing (at least it would be preferred to include some selected variants to illustrate distinct variations as discussed in the text).
In this context the authors also indicate a certain degree of dynamic (partial?) recrystallization of the deformed microstructures (and reiterated in Conclusions bullet pt.4). If this is the case (although not explicitly documented or shown), it is (close to) meaningless to compare and discuss the texture predictions by the VPSC model with the experimental textures, - i.e. a clear flaw of the paper. VPSC is indeed only a deformation texture model and does not include anything that allows for any predictions of possible recrystallization texture evolution (and which can be very different from the deformation texture)! A speculation, but this might also be the main cause of the discrepancies between the experimental and simulated textures? On the other hand, dynamic recrystallization is not considered to so common in aluminium alloys (due to, in most cases, fast recovery).
It is well known that deformation textures generally develop with increasing deformation (strain) (typically sharpens up to a certain (large) strain) and that all texture models (including Taylor and Sachs) accounts for this. In the present work the authors also experimentally varies the deformation temperature and strain. The classical Taylor model does not have any strain rate or temperature sensitivity, and it is not clear to me to in what way and/or to what extent any temperature or strain rate sensitivity is part of the (classical) VPSC model (?), and thus making such an investigation meaningful?
Another comment to the problem/experimental design is also the somewhat limited variations in deformation/strain. To really test the validity of the VPSC model a broader span in deformation would have been more sensible and preferred in my opinion.
Another weakness of the paper is a number of strange and awkward phrasing, some also incomprehensible and/or incorrect – some examples below:
p.5, line 176: On the crystal axis, ……..
Not meaningful to me !
p.6, l. 178: Decompose the velocity gradient into strain rate and spin rate:
-> The velocity gradient can be decomposed into strain rate and spin rate as follows:
The same ‘strange’ sentence structure is also used several other places in Sec. 3.1 (e.g. l. 206; l. 209; l. 219)
p. 9, l. 260: Comparing the experimental curve with the curve predicted by the model, it is found that the VPSC model and the corresponding hardening parameters are better at predicting the hot compression stress and strain of the aluminum alloy 7075.
Strange formulation - better than what?
The same formulation is used several places in the manuscript!
p. 9, l.264-265:
After the flow stress reaches its peak, active recovery softening and dynamic recrystallization softening of the material occur.
Any evidence that dynamic recrystallization actually takes place?
p.10, l. 275: maintenance time
Strange use of ‘maintenance’ ……..
Leave out ‘maintenance’. Use just ‘time’ or perhaps ‘extension time’
p.10, l. 2778-279: ….. the relatively active motion of atoms at high temperatures favors dislocations, ……
Strange sentence – what is the meaning of ‘favors dislocations’.
p. 12, l. 331: peak density -> peak intensity
p.12, l. 332 the increase in deformation leads to an increase in dislocation density, the accumulation of dislocations, ……
Same thing said twice, - ‘accumulation of dislocations’ leads to increased dislocation density
p. 12, l. 345: ….. the nucleation of texture becomes more divergent.
Meaning of ‘nucleation of texture’ in this sentence?
p. 12., l. 351 …
This phenomenon may be since the dislocation density and the accumulation of dislocations in the grains increases with increasing temperature.
Not correct statement! Increase in temperature would lead to less accumulation of dislocations, due to faster/more recovery at higher temperatures
p. 14., l. 362: but can still form cores during recrystallization
Not meaningful sentence to me – what is the meaning of ‘cores’ in this sentence
p. 17, l. 460: A high strain rate accelerates the growth rate of dislocations
What is ‘growth rate’ of dislocations?
Some additional issues are indicated in the attached marked copy of the manuscript.
In general, the manuscript would benefit from a careful revision of the English language!
Then a few more technical issues:
In my opinion it is unnecessary to include both Table 2 and Table 3, including the same data, just presented differently. One of these is redundant.
The rather extensive and detailed presentation of the VPSC model seems also somewhat unnecessary. This VPSC model is well known and well described elsewhere in literature, and unless the present authors have made any modifications to the original model, one can mainly refer to relevant literature and previous presentations.
Eq. (4) and Eq. (7) seems to be the same!? Not necessary to include twice!
Some of the figures are quite small (e.g. Figs. 5 and 6), and the legends are not possible to read.
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
Scope of the work is to investigate the hot deformation behavior of aluminum alloy 7075 and to investigate the capability of the VPSC model to predict the experimental results.
The manuscript is clear and written in a well-structured manner. The manuscript is scientifically sound and the experimental design is appropriate to test the hypothesis. The conclusions are consistent with the evidence and arguments presented.
Author Response
Thank you for your approval of this study. The author has revised the article in detail according to the opinions of other reviewers. Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments for author File: Comments.pdf
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
See attached files!
Comments for author File: Comments.pdf
