Activation Behavior of {10-12}-{10-12} Secondary Twins by Different Strain Variables and Different Loading Directions during Fatigue Deformation of AZ31 Magnesium Alloy
Round 1
Reviewer 1 Report
The paper considers the influence of the process of cyclic loading on the change in the structure of a magnesium alloy. In my opinion, the authors did a lot of work for this material and discussed the results. I have only minor comments on the article:
From the description of the experimental procedure, it is not clear in what state the AZ31 alloy was investigated (cast, deformed, heat-treated…)?
How many samples were tested?
"...polished with AC2 polishing solution" what is this solution? need to be explained or referenced.
Author Response
We truly appreciate your professional and informative comments regarding the manuscript. This manuscript has been carefully revised based on each comment. Detailed responses to your comments and suggestions are provided in the following section. For clarity, we have listed the comments below and have addressed them individually.
Reviewer 1：The paper considers the influence of the process of cyclic loading on the change in the structure of a magnesium alloy. In my opinion, the authors did a lot of work for this material and discussed the results. I have only minor comments on the article:
Comment 1. From the description of the experimental procedure, it is not clear in what state the AZ31 alloy was investigated (cast, deformed, heat-treated…)?
Response: Thanks for your carefully review. The material used in the current study was a commercial hot-rolled AZ31 (3wt% Al-1wt% Zn) magnesium alloy plate. The state of AZ31 alloy have now been added to the revised manuscript.
Comment 2. How many samples were tested?
Response: Thanks for reminding us. At least three specimens were tested in each condition. The description have been added to the revised manuscript.
Comment 3. "...polished with AC2 polishing solution" what is this solution? need to be explained or referenced.
Response: Thanks for your suggestion. The AC2 solution have explained in the revised manuscript.
Reviewer 2 Report
The paper clarifies the formation of secondary twins in magnesium specimens cut along ND and RD directions. The conclusions drawn from the results are logical ones.
However it is not prefectly clear how the authors performed EBDS investigations of the fractured surfaces. It is not an obvious task, so a little more detailed description should be included.
Author Response
We truly appreciate your professional and informative comments regarding the manuscript. This manuscript has been carefully revised based on each comment. Detailed responses to your comments and suggestions are provided in the following section. For clarity, we have listed the comments below and have addressed them individually.
Reviewer 2：The paper clarifies the formation of secondary twins in magnesium specimens cut along ND and RD directions. The conclusions drawn from the results are logical ones. However it is not perfectly clear how the authors performed EBSD investigations of the fractured surfaces. It is not an obvious task, so a little more detailed description should be included.
Response:
Thanks very much for your kindly advice. The area near the crack was seriously deformed. We have tried to characterize it with EBSD, but the indexed frequency was very low, so the grain orientation cannot be determined. But the fracture morphology by SEM can also reflect the differences of sample. The experimental results were based on the combination analysis of SEM and EBSD. In the subsequent work, we will continue to try to carry out EBSD investigations on the fractured surfaces.
Reviewer 3 Report
The manuscript is devoted to the activation of {10-12}-{10-12} secondary twinning during fatigue loading at different direction and strain levels in the well-known AZ31 Mg alloy. It is rather concise but well-organized and clear. It can be considered for further publication after some minor and major changes such as:
1. The introduction part is rather poor. The deeper analysis of literature references should be made and addressed to the description of dominating deformation mechanism (especially twinning modes) in Mg alloys under cyclic loading considering the loading directions (RD, TD or ND) and strain levels. There are only two cases described more deeply in the introduction part - references 11 and 12. Besides, it is just mentioned that "secondary twinning is related to the grain size, loading direction and strain amplitude". It should be said how they affect secondary twinning, in what ranges of grain size or strain amplitude etc. - there are a lot of references about such popular AZ31 Mg alloy.
2. The results section starts with a description of hysteresis loops and the dominant twinning mechanisms affecting their shape with respect to the c-axis direction etc., but there is no mention about the initial microstructure (grain size) and crystallographic texture. It should added to the manuscript, e.g. in the form EBSD maps.
3. There are no literature references mentioned in the Table 1.
4. The numbers of figures 3-7 should be checked and corrected in the text.
5. The misorientation angle distributions of all analyzed samples (loaded along ND and RD at 1 and 0.5%) should be added to the manuscript. The quantitative analysis of EBSD maps should be also made, i.e. the fraction of different twinning mechanisms should be calculated as well to clearly show the tendency obtained in the research.
6. The following sentence in the last paragraph of section 2.2 should be rephrased: "The size of the {10-12} primary twin becomes thinner with increasing cycle cycles".
7. It is mentioned in the conclusions that "The thickness of the primary {10-12} twin at 1% strain is large enough to activate the {10-12}-{10-12} secondary twin." Could You estimate the minimum size / width of those primary {10-12} twins that undergo the secondary twinning in this research based on the EBSD measurements? It would be a very interesting result for other researchers in the field.
Author Response
We truly appreciate your professional and informative comments regarding the manuscript. This manuscript has been carefully revised based on each comment. Detailed responses to your comments and suggestions are provided in the following section. For clarity, we have listed the comments below and have addressed them individually.
Reviewer 3：The manuscript is devoted to the activation of {10-12}-{10-12} secondary twinning during fatigue loading at different direction and strain levels in the well-known AZ31 Mg alloy. It is rather concise but well-organized and clear. It can be considered for further publication after some minor and major changes such as:
Comment 1. The introduction part is rather poor. The deeper analysis of literature references should be made and addressed to the description of dominating deformation mechanism (especially twinning modes) in Mg alloys under cyclic loading considering the loading directions (RD, TD or ND) and strain levels. There are only two cases described more deeply in the introduction part - references 11 and 12. Besides, it is just mentioned that "secondary twinning is related to the grain size, loading direction and strain amplitude". It should be said how they affect secondary twinning, in what ranges of grain size or strain amplitude etc. - there are a lot of references about such popular AZ31 Mg alloy.
Response:
Thanks for your constructive suggestion. The authors have re-written the introduction section.
Comment 2. The results section starts with a description of hysteresis loops and the dominant twinning mechanisms affecting their shape with respect to the c-axis direction etc., but there is no mention about the initial microstructure (grain size) and crystallographic texture. It should added to the manuscript, e.g. in the form EBSD maps.
Response: Thanks for your carefully review. The AZ31 magnesium alloy plate used in this experiment was consistent with those used in our previous paper (Yang P F, Yang Z Y, Li L, Qi S, Li T, Ma X K, Zhu M H. Towards understanding double extension twinning behaviors in magnesium alloy during uniaxial tension deformation[J]. Journal of Alloys and Compounds, 894(2021)162491). The microstructure of original material presented a twin-free feature and the average grain size was about 35 µm. We have added the description in the manuscript.
Comment 3. There are no literature references mentioned in the Table 1.
Response: Thanks for reminding us. We have now added the reference in the Table 1.
Comment 4. The numbers of figures 3-7 should be checked and corrected in the text.
Response: Thanks for your carefully review. We have checked and corrected the numbers of figures 3-7 in the revised manuscript.
Comment 5. The misorientation angle distributions of all analyzed samples (loaded along ND and RD at 1 and 0.5%) should be added to the manuscript. The quantitative analysis of EBSD maps should be also made, i.e. the fraction of different twinning mechanisms should be calculated as well to clearly show the tendency obtained in the research.
Response: We have added the misorientation angle distributions of all analyzed samples in the manuscript and calculated the fraction of different twinning mechanisms.
Comment 6. The following sentence in the last paragraph of section 2.2 should be rephrased: "The size of the {10-12} primary twin becomes thinner with increasing cycle cycles".
Response: Thanks for your kind, we have rephrased the sentence according to your suggestion. "Cycle cycles " has replaced by "cycle numbers ".
Comment 7. It is mentioned in the conclusions that "The thickness of the primary {10-12} twin at 1% strain is large enough to activate the {10-12}-{10-12} secondary twin." Could You estimate the minimum size / width of those primary {10-12} twins that undergo the secondary twinning in this research based on the EBSD measurements? It would be a very interesting result for other researchers in the field.
Response:
Thank you for your excellent suggestion. Our goal is to find the minimum width of a primary {10-12} twin that activates a {10-12}-{10-12} secondary twin in the future. However, only such a trend has been found at present. We still need to do more experimental to get more accurate results in the future.
We have carefully checked the References list, and some mistakes were corrected.
With best regards from all of the authors,
Sincerely Yours
Li Tan
Associated Prof., Ph.D.
School of Materials Science and Engineering,
Chongqing University of technology,
Chongqing 400000, China
E-mail: [email protected]
Round 2
Reviewer 3 Report
All my comments have been addressed by authors. The manuscript can be accepted in the present form.
P.S. Some minor mistakes can be improved at the proof stage, i.e. line 50 "grain size, loading direction and ...."; line 64 "has been little work"; line 76 "And the samples were..."; line 204 "twin can be observed only..."; extra brackets "[" in lines 204 and 205 should be removed.
Author Response
Thanks for your carefully review. We have corrected the mistakes and revised the title of the paper.
