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by
  • Fulong Chen 1,
  • Kaidi Li 1 and
  • Jinshan Li 1,2
  • et al.

Reviewer 1: Anonymous Reviewer 2: Anonymous Reviewer 3: Anonymous

Round 1

Reviewer 1 Report

In the paper "Deformation behavior and microstructural evolution of Inconel 625 superalloy plates during hot compression process", the authors investigate and model the hot deformation behaviour of superalloy using a thermomechanical simulator and microstructural investigations. The authors construct the Arrhenius-type model for the description of the dependence of the peak stress on the deformation conditions. The microstructure evolution model was also constructed. The presented results seem to be interesting. However, the paper is needed to be corrected accordingly following comments:

  1. A large amount of the articles about the hot deformation behaviour of the superalloys were published last time. The authors should analyse more papers devoted to the modelling of the hot deformation behaviour and microstructure evolution of the superalloys and add the comparison of their result with already published. It is recommended to consider following papers [10.3390/met11040605, 10.1007/s11041-019-00326-0, 10.1016/j.msea.2016.03.044].
  2. The chemical composition of the investigated material should be added to the manuscript.
  3. Why the end true strain for 800 ºC and 1 1/s has a lower value than 0.9?
  4. The reason for the absence of the stress-strain curve at 850 ºC and 1 1/s should be described.
  5. The first peak on the stress-strain curves at 950 – 1050 ºC and 0.001 – 0.01 1/s is due to a methodological error during testing. At the beginning of the deformation, the die has a higher velocity than it is needed. As the result, the strain rate at the beginning of the deformation has a significantly higher value than preassigned. This peak should be smoothed to prevent misleading the readers. For the next tests, it is recommended to manually change the die’s racing in the script file (or maybe by another way).
  6. Xdrx should be in the left part of Eqs. (16) and (17).
  7. The value of the Avrami constant shows the mechanism of the dynamic recrystallization. The analysis of the influence of the temperature and strain rate on the DRX mechanism should be added to the manuscript.
  8. The model of the strain rate and temperature dependence of the peak strain should be added to the manuscript.
  9. The term “incubation period” in conclusion (3) cannot be applied to the DRX process. It is correct to use the term “critical strain”. The conclusion should be changed.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Remarks to paper: Deformation behavior and microstructural evolution of Inconel 625 superalloy plates during hot compression process

  1. It would be better to associate grain growth with precipitates.

3 Deformation behavior and microstructural evolution of Inconel 625 superalloy plates during the hot compression process

18-20, 383-388 The formation of deformation twins at temperatures above 800C is unlikely, and in this work, it can be considered unproven or attributed to annealing twins, despite rapid cooling, or can be proved using transmission microscopy.

80-88 The purpose of the work requires clarification, and the paragraph should be rewritten and should contain only the purpose of the work.

93 φ - is not a symbol of diameter

109 ? STUER? – misprint

It will be better if the chemical and phase composition of Inconel 625 was presented.

119-123 – is an Experimental procedure and need to transfer to section2

135-136 - Graphs waviness (spasmodic) can only be explained by errors or incorrect calculation of the results (800°C- 0.001 s-1, 850°C – 0.01, 0.001 s-1, 900°C -0.1, 0.01 s-1).

139-142 In Ref. [21] was studied gamma prime precipitated superalloy, and the mechanism of DRX can be another.

149 Initial yield strength is determined according to ASTM.

238-239 …of other elements in Ni superalloy,…

239 …such as Al (269kJ/mol) and Ti (256kJ/mol). Al and Ti are not key elements in IN625 alloy.

276-280 The grain misorientations shown in enlarge parts exhibit that twin-related DRX occurs during the compressing process. TBs produced in the parent grains due to the migration of grain boundaries accompanied by the grain boundary bulging.  …probably only, need TEM and HRTEM images to show deformation twins.

280 bugling – bulging?

291-292 How was defined the fraction of sub-grain boundaries (SGBs) and LAGBs by Channel 5? How was determined difference between SGBs and LAGBs? To Section 2.

295 Fig. 8  It is not clear how the deformation twins and annealing twins were separated.

 

Fig. 10, 11 - test temperature not specified. 1000°C?

334 335 - When complete DRX occurs, the ratios between LAGB, HAGB, and TB remain basically constant. What is the ratio?

373 What did the averaging of n and k give?

293 …continuum continuous DRX

The statement requires clarification:

293 It can be seen that the intensity of cDRX decreases with the increases of the temperature.

387-388 The intensity of cDRX decreases with the increases of the temperature. 

386 …and the annealing twin is dominant when the temperature is above 900℃. Or 950°C as in Fig. 8?

390  inhibited shortened

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The authors studied the deformation behavior and grains evolution of Inconel 625 under the hot compression process.

In my opinion, the manuscript is interesting. 

However, some parts need to be modified/better explained:

 

Introduction

  • for the sentence : "However, the twin-related DRX is not studied in detail."

 

The authors should clearly explain the crucial role of this investigation to improve the quality of the manuscript.

 

Materials and methods

 

  • How was selected the annealing treatment at 960 °C? the heat treatment was followed by fast air cooling or air cooling?
  • Please provide the chemical composition of the alloy

 

 

Paragraph 3.2

 

  • Please explain the selection of TB 60 ± 3°, providing some references
  • Figure 8: appear the SGBs and LGBs. Since both are related to misorientation angles less than 15°, I would recommend explaining the difference between SGBs and LAGBs. This will help the readers better understand the manuscript. Moreover, the figures should also report the evolution of the HAGBs.
  • When discussing Figure 10, it would be interesting to insert a graph for comparing the grain size distribution and average grain size for the different conditions.
  • When possible compare the results with the available literature to show similarities or differences. 

 

Conclusion

Please provide possible industrial applications or future studies related to the current work in order to highlight the positive and innovative aspects of this work.

 

Based on my previous comments, I suggest a minor revision.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors mainly answered the previous comments. However, some points should be cleared:

  1. Point 3: Why the end true strain for 800 ºC and 1 1/s has a lower value than 0.9? Response 3: Thank you for this useful comment. The reason why the end true strain for 800 ℃ and 1s-1 has a lower value than 0.9 is that under this condition, the sample cannot be further deformed.

What does it mean that the sample cannot be further deformed? Is the sample was broken before 0.9 strain or is it not enough of the testing machine power or was it another reason? The details should be added to the manuscript.

  1. Point 4: The reason for the absence of the stress-strain curve at 850 ºC and 1/s should be described.

Response 4: Thank you for this useful comment. The reason for the absence of the stress-strain curve at 850 ℃ and 1/s is that under this condition, the compressor cannot work normally, so the sample cannot be deformed normally.

What does it mean that the sample cannot be deformed normally? The stress-strain curve at 850 ℃ and 1/s should be added and “abnormality” of the deformation should be described in the manuscript.

  1. Point 8: The model of the strain rate and temperature dependence of the peak strain should be added to the manuscript.

Response 8: Thanks for your useful suggestion. The focus of this work is to study microstructural evolution and DRX. Peak strain is not our research point, so it will not be described here and will be discussed in detail in our next work.

The peak strain is directly related to microstructural evolution and DRX. The critical strain is proportional to the peak strain. The model of the strain rate and temperature dependence of the peak strain should be added to the current manuscript.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Remarks to paper: Deformation behavior and microstructural evolution of Inconel 625 superalloy during the hot compression process

118 DED – if is used in one place.

The aim of the work is to …..

132 the softening effect caused by DRX was proposed. The remainder

133 of  this  paper  is  organized  as  follows:  Section  2  provides

134 information about the sample preparation and the, compression

135 tests, and the characterization of the micro-scale.

136 Section  3  analyze  the  deformation  behavior  and  the

137 microstructural evolution of IN625 alloy under different deformation behavior

138 and  introduces  the  constitutive  model  considering  the  DRX

139 phenomenon in detail kinetics. , and Section 4 concludes the pap

 

206 0.01s-1), the curve has obvious fluctuations (Fig.2 (a-c)), which is

371 and 488 How twin morphology (Σ3) changes a little were detected and at what figure we can see it?

373 SGBs are special? LAGBs (Σ?) with a low misorientation (2°-5°).

When the
406 strain rate is small, DRX is completed and the grains have plenty
407 of time to grow (during annealing?) and vice versa.

So, there are many elongated
408 grains in the microstructure when the strain rate is 0.1s-1 or 1s-1 (during self-heating at a high strain rate?)
409 (Fig.10(c)(d)). It can also be seen from Fig.10(e) that when the
410 strain rate is large, the fraction of small-sized grains is large.

419, 422 - grain size and grain diameter are not the same. It is not clear how the grain size was calculated for Figure 10e. If these data were taken from EBSD analysis, this is unreal data and requires confirmation by another method.

Author Response

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Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

The authors have answered the comments from second review and improved the manuscript. The last comment is following:

1. The value of effective activation energy in Zener-Hollomon parameter (Eq. 19) should be added to the paper. It is hard to use this equation without the Qp value. 

Author Response

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Author Response File: Author Response.pdf