Improving Mechanical Properties of Mg–Sc Alloy by Surface AZ31 Layer
, Yanchun Zhao 1, Tingzhuang Han 4, Guangang Wang 5, Liang Wu 5 and Guangsheng Huang 5
Round 1
Reviewer 1 Report
Page 2, line 48
Expression repeated with two different acronyms:
…”by using surface mechanical grinding (SMAT), surface mechanical grinding (SMGT)”
Page 2, line 51-53
The authors give a contradictory comment just before the following lines:
“Furthermore, Lu [14] prepared gradient nano-structure materials with coarse-grained cores on the surface of nanocrystalline through surface processing technology. The strength was significantly improved and the elongation was as high as 60%, thus obtaining good matching of the strength and ductility.”
It is recommended that the authors interpret the discrepancy between different published results regarding whether the so-mentioned surface treatments increase or decrease the ductility while increasing the strength.
Page 2, line 59
Correction in English:
“A small amount of researches [16-18] …”
It is recommended that the authors re-word this sentence. For example: “few investigations…” or “small number of studies…”
Page 2, line 64-65
“The effect of different extrusion temperatures on microstructure of the alloys was characterized, and the effect of AZ31 surface fine grain layer on the mechanical properties of Mg-Sc alloy was investigated.”
The sentence above may better read as follows:
“The effect of different extrusion temperatures on the microstructures of the alloys was characterized, and the effect a fine-grained surface layer of AZ31 on the mechanical properties of Mg-Sc alloy investigated.”
Please note that not all points that need correction to the English of the text have been indicated. The suggested corrections above are limited to the Introduction section. The rest of the text must be checked for English for better reading.
Technical and Scientific Comments:
Line 76
The authors expressed that “Since the high temperature hardness of AZ31 alloy is much higher than that of Mg-Sc binary alloy, …”
If correct, a reference must be given for this claim. The bonding in the experimental method used may not require such a hardness difference necessarily.
XRD:
The glancing angle scanning must be adjusted so that the bonding layer between the two different alloy systems is targeted. Otherwise, AZ31 and Mg-Sc alloys can easily be predicted in terms of their respective individual phase constituents. There is no point in scanning the bulk of these two alloys individually. What is interesting is the phase constituents at the bond layer.
The authors used a very fast scanning during XRD. The step size and the dwell time must be given separately. Although the overall scan range is appropriate, the step size must be kept small (e.g. 0.02 degree and dwell time around 5sec.)
Tensile test:
The authors must express the international standards used for selecting the tensile test samples, and preferably show with a schematic drawing the orientations chosen when obtaining the test samples.
Conclusions:
The authors are relating the strength of the layered materials solely to the presence of the AZ31 layer with different grain sizes and textured morphology. Since they are neglecting the possibility of presence of precipitate phases in Mg-Sc system, their assumption can not be taken for granted. The XRD work is not detailed enough to include or exclude this possibility. Scientific results should not b based on poor experimental evidence or assumptions.
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The authors investigated composites with gradient structure in a magnesium alloy. A short, but fairly complete introduction allows you to understand the aim of the study. Methods for studying alloy characteristics are well described. The article can be published in the journal, but there are a few comments to consider.
1. The choice of temperatures for extrusion is not clear. Please give an explanation in the text
2. Errors (grain size, strength) are not indicated everywhere.
3. The study is mainly based on the EBSD analysis, to save space, some results should be summarized for example in Figures 6-9.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
I have carefully reviewed the manuscript entitled “Improving mechanical properties of Mg-Sc alloy by surface AZ31 layer”. The authors have discussed their distinct fabrication approach which focuses on improving the mechanical properties of Magnesium (Mg) alloys by gradient grain structuring. The manuscript is well organized and certainly has merits and thus can be considered for publication with minor changes. 1. Abstract should be improved. It is not very clear on the scientific originality. 2. The introduction is very weak and should emphasize more on the available literature. The current introduction does not provide a clear state of the art in the field. 3. The abbreviations used must be defined properly at their first use. 4. Many typos in the manuscript need to be removed. One of such is CO2. Please write it properly. 5. The XRD results were not analyzed properly. Please use the below references and cite to expend XRD analysis. Try to calculate the crystallite size and strain. i. https://www.sciencedirect.com/science/article/abs/pii/S0254058421002595 ii. https://www.mdpi.com/2079-4991/11/11/3009 iii. https://pubs.rsc.org/en/content/articlelanding/2020/dt/d0dt01318h/unauth iv. https://pubs.rsc.org/en/content/articlehtml/2020/na/d0na00156b v. https://www.sciencedirect.com/science/article/abs/pii/S0304885319309679 vi. https://scholar.google.com.au/citations?view_op=view_citation&hl=th&user=vPcct9gAAAAJ&sortby=pubdate&citation_for_view=vPcct9gAAAAJ:4OULZ7Gr8RgC 6. Figure captions should be more informative rather than just providing the elementary details. 7. For all the figures, the inside captions of the figure should be of the same size and font as the whole paper. 8. Please expand the conclusion. 9. Please use the new references as well and add their discussion in the introduction as much of the literature cited is very old. Overall, I am happy to suggest the manuscript be accepted with suggested changes.Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The investigation is based on an interesting technique to create a sandwich structure made up of two different magnesium alloy systems. A comment or a detailed evaluation on the applicability regarding the selection of different magnesium alloys to be employed in the same technique would have been appreciated.
