About the Memory of Transformation-Induced Plasticity in 35NCD16 Carbon Steel Subjected to Various Thermomechanical Histories

Round 1

Reviewer 1 Report

The authors investigate the role of a preceding thermomechanical loading history on the amount of final TRIP strain as measured by means of standard dilatometric tests. For modeling purposes such a study has some meaning with respect to the calibration of the material parameters contained in typical evolution laws for the TRIP strain, e.g. the one proposed by Leblond et al. In industrial processes phase transformation frequently occurs in materials that have undergone heavy plastic pre-deformation, so the work at hand for sure has some technological relevance. The novelty versus the existing literature is only incremental though. In fact, the authors should go over the literature once again, as most of the provided references are from French groups with some proximity to the authors disregarding the fact that on the international stage many quite similar studies have been performed, e.g. in Japan the seminal works of Tanaka et al. or likewise by some groups in Germany.

Apart from the somewhat incomplete list of references there are some other issues that need to be addressed:

1. Lines 68 to 104: The experimental procedure can be described in a much more concise way, e.g. by means of a table.
2. Figure 2 is too small. It is almost impossible to spot any details of the experimental setup.
3. Equation (1): The question is if TRIP strain in this work is understood as including the “metallurgical strain”, i.e. the strain due to the metallurgical volume change during austenite to martensite transformation (Delta epsMA^Talpha as it is termed on line 364), or if it is understood as the apparent inelastic strain after applying a load. The former interpretation would agree with equation (1) but contradicts the rest of the paper, e.g. Fig. 7b or eq. (8). This has to be clarified.
4. Fig. 7b: How has the curve been determined? It is not so easy as to simply subtract the dilatometric curve under load from the reference curve without load because the martensite start temperature usually shifts to higher values due to the Clapeyron effect. Some more details are desirable.
5. Fig. 7: The vertical axis should be named “strain”. That is the English translation of the French word “deformation”.
6. Figs. 7-21: In the close-up plots (labelled Fig.x b) transformation seems to be triggered at around 50° higher temperatures than what is shown in the complete dilatometric loop on the left hand side (Fig. x a). The abscissa values should be checked once again.
7. Equation (8) technically only holds if the applied stress remains constant (which certainly is the case for the experiment at hand) and it only gives the final TRIP strain value after complete transformation. For more general cases a rate formulation should be used. This should be commented on.
8. Equation (8): What is the motivation to use the index notation (11) in this equation? Again, since it has not been used before it is not necessary to introduce it here.
9. Figure 25 is unnecessary.

General remarks:

1. The TRIP strain seems quite small compared to similar steel grades. Did the authors make sure that the transformation was 100% complete? This could be checked e.g. by analyzing the micrograph of the specimen after completion of the test series. Some comments are expected in a revised version.
2. Please provide the value for Delta eps_12 (=Delta epsMA^Talpha).
3. Using realistic data for Delta eps_12 of around 0.5 - 0.7 % would, according to equation (10), render a larger value of k than what the experiments show. Is there any explanation for that discrepancy?
4. Use consistent nomenclature. The TRIP strain should always be denoted by one and the same symbol. Currently it is different in eq. (1), (2) and (8). Another example is the symbol for the strain jump (the “metallurgical strain”) in line 390 which should be the same as the one mentioned in line 364.

Concluding, the work at hand is of interest to the community but has some deficiencies that need to be attended to before publication. The overall recommendation is “major revision”.

Author Response

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Reviewer 2 Report

In this manuscript, the authors have investigated the TRIP phenomenon in martensitic transformation of 35NCD16 steel. By considering different stress levels(σ_y/2, σ_y/2,3σ_y/4) to analyse memory effect. Meanwhile, the TRIP parameter and kinetics, as well as the relation between the final TRIP and the applied stress are also studied. Based on the criterion of journal, some parts should be improved before publication.

1) The biggest concern of the present paper is the grouping of yield stress at TPIP test, As the authors choosed 1/4 of the yield stress(1/2 and 3/4) in the “Experimental procedure” section, Why authors choose 1/4,1/2,3/4 of the yield stress instead of 1/3 or other stress values.

2) In section 2.1, the experimental details should be shown. For example, the ratio of nitrogen and argon, where is the K-type thermocouples ?

3) How to obtain Equation (1)? Its suggested to add a definition or description of ε^trip.

4) Why does the authors choose the different thermomechanical history order of TRIP test? For example(No limited), In the section of 3.3.3, if the order is FD -  - FD -  - FD  - – FD - , In my opinion, the order of section 3.4.3 should be FD -  - FD -  - FD  - – FD - , this order will be more comparative. However, The order given by the author is FD -  - FD -  - FD  - – FD - . It is confused about thermomechanical history order of TRIP test, Please explain and indicate.

5) The quality and differences of figures should be improved, like Fig. 2. Besides, some lines are overlapped in some figures.

6) In the section of 3.6.4, The sentence of “Note that in literature, it is generally admitted that the relation is linear for applied stresses that are less than 1/2 of the yield limit” need to cite relevant literature.

7) Some figures could be merged to one figure for comparation, like figures 7, 8 and 9.

Author Response

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Reviewer 3 Report

   This manuscript reports “about the Memory of Transformation induced plasticity in 35NCD16 carbon steel subjected to various thermomechanical histories”. To evaluate the TRIP characteristics of 35NCD16 carbon steels, the authors performed TRIP test, considering various thermomechanical histories. Although the experimental procedure was well documented in detail, there are so many figures, tables, and texts, which may cause confusion in understanding the results of this paper. In particular, the logic to support the author’s claims (e.g. to determine the relationship between TRIP characteristics and thermomechanical history) is unclear. For the sake of the readers, present article needs to be rewritten and reorganized concisely by merging the tables and figures shown in Section 3 and rewriting the text.

In addition, the following modifications would be required.

• In 2. Experimental procedure, the stress applied during the TRIP test is expressed as σ_y/4, σ_y/2, 3σ_y/4, respectively. It needs to add the stress values applied during the TRIP test (XX MPa), relating to the estimated yield stress (160MPa).
• Also, in the case of first, second, and third series about thermomechanical histories described in 2. Experimental procedure, it should be summarized in tables, divided into light, medium, and severe thermomechanical history.
• For the description of the equipment in Figure 2, it is appropriate for the reader to change the language of the figure to English.
• In the section of 3.1. Elastoplastic behavior of austenite at temperatures close to Ms, it would be better to move this section to the 2. Experimental procedure.
• In the case of mentioned in Equations 2 and 3 (Section 3.6.1), if it is the same parameter as   in Equation 1, it should be expressed as the same parameter.
• Also, it is necessary to specify in Section 3.6.1 how the value for elastic deformation, , described in Equation 1 was calculated.
• In the case of equation 8 in Section 3.6.2, detailed descriptions of parameters, such as ε^pt₁₁, z, and σ₁₁ are not sufficient. Relevant parameters should be explained in detail.
• In evaluating the TRIP characteristics of the experimental results in Section 3.6.3, it was compared with other evaluation models such as Desalos’ and Leblond’s model. It is necessary to explain why the TRIP characteristics appears differently depending on the applied model.
• In the case of Figure 22 and Figure 23 in Section 3.6.3, it is appropriate to delete Figure 22 and use only Figure 23, and it is necessary to correct the caption.

Author Response

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Round 2

Reviewer 1 Report

The authors responded satisfactorily to the comments of the first review report. There is still a little inconsistency in the nomenclature of \epsilon_tp (equation 9) vs. \epsilon_pt (equation 10). This can be corrected upon final editing.

Author Response

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Reviewer 2 Report

It can be acceptable. It is a small suggestion that the authors could mark the revision parts using other color in the revised manuscript. 

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Reviewer 3 Report

   In the case of the revised manuscript, the experimental results and related TRIP characteristics were explained in detail by comparing them with other models such as Desalos’ and Leblond’s model. However, the revised manuscript still includes many figures and tables, and needs some correction. Especially in figures, there are many duplicate results, and those need to be merged into one figure. Therefore, the present manuscript must be reconstructed concisely again, and the following modifications should be required.

 

• 7, 8, and 9 need to be merged into one, and the results of Fig. 10 overlap with those of Fig. 7(b), Fig. 8(b), and Fig. 9(b), so they need to be deleted.
• With this, it is necessary to merge Section 3.1.2, section 3.1.3., and section 3.1.4 into one.
• In Fig. 11 which shows thermomechanical cycle for a given high strain TRIP test, the specific stress values for ‘high strain’ described in caption of Fig. 11 need to be mentioned. If the corresponding stress is reference T_3σy/4 , it is redundant with Fig. 9(a) and needs to be deleted.
• Likewise, for the case of Fig, 12, it is the same with the test result of Fig. 6, so it needs to be deleted.
• In the case of Fig. 9(b) and 10, which shows TRIP strain vs temperature curve of , the results do not match each other. Please double check the results.
• In addition, minor typos need to be corrected.

Comments for author File: Comments.pdf

Author Response

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Round 3

Reviewer 3 Report

This manuscript has been appropriately revised.