On the Effects of High and Ultra-High Rotational Speeds on the Strength, Corrosion Resistance, and Microstructure during Friction Stir Welding of Al 6061-T6 and 316L SS Alloys
Round 1
Reviewer 1 Report
Dear Authors,
I have read your paper "Analysis of high rotation speed and ultra-high rotational-speed parameters effects on friction stir welded dissimilar joints of aluminum alloy and steel", which has been submitted to Coatings journal.
This paper is well written, however, some modifications could be performed. My suggestions are listed below.
Introduction:
- This section is really well written. You have supported indtroduction with newly published articles, which allows to present scientific background for your investigations.
- The topic of joining aluminium with stainless steel (SS) is very important. You have presented relevant scientific background. However, one issue has not been mentioned. The induction heating during FSW of aluminium and SS is in scientific interests nowadays (e.g., https://doi.org/10.2478/adms-2021-0015).
Materials and Methods:
- Please show the dimensions of used plates. Now, only thickness of both materials is presented.
- Table 1 - the source of presented values is unknown. Have you analyzed these compositions? Or values were taken from standard/manufacturer data? Please add this information in the paper.
- Table 2 - thy these parameters were chosen? Have they been used in preeliminary investigations, previous paper or taken from literature?
- You have presented metallographic tests, hardness measurements and tensile strength test. However, I cannot find any information about used requirements from relevant standards. Have you performed these test following any standards? If yes, please add their numbers, if not, please describe why you have not used standards' requirements.
Results and Discussion:
- Results are presented and analyzed well. Congratulations.
- Fig. 4 - there is no information about used etchant. Moreover, the scale bars are hard to read.
- In section 3.1. I cannot find sceintific discussion (except line 243). You should compare wider your results with results from literature. The same in rest of sections.
- Line 258 - move first letters to capital letters
- Section 3.5. - I propose to modify the name of section to "Tensile strength test". the "joint strength" does not allow to get straingth information, which strength do you mean.
Conclusions:
- I propose to present the most important conclusions in points. It will be more readalbe.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This manuscript presents a thorough experimental characterization of the microstructure, mechanical strength, and corrosion resistance of dissimilar metals joint using friction stir welding (FSW). The effect of rotation speed and welding speed in the FSW process is investigated systematically for an aluminum alloy/ stainless steel joint. There has been a rapidly growing interest in the use of FSW for joining dissimilar metals, particularly sheet metals, for the automotive, railway and shipbuilding industries. While the vast majority of existing work on FSW has focused on dissimilar metals with similar thermomechanical properties, there remain open questions regarding the microstructure (i.e., intermetallic compound formation), strength and corrosion resistance of FSW-joint dissimlar metals with differing thermomechanical properties. This work addresses this knowledge gap. Given the interest in FSW in the broad research community of advanced metals, I believe this work will be a good fit within the scope of the journal Coatings submitted to section: Corrosion, Wear and Erosion.
I would, however, like the authors to address the following comments:
- The English language needs extensive editing - there are several grammatical errors that need to be fixed and sentence structure needs to be improved. For example, the title should be changed to "Analysis of the effects of high rotation speed and ultra-high rotation speed parameters on strength, corrosion resistance and microstructure of the friction stir welded aluminum alloy-steel joints.", or something along those lines.
- Figure 14 - the caption says "Stress-Strain" curve when the data in the plot show the "Strength vs. Displacement" - please convert to engineering stress-vs. engineering strain.
- For future outlook, what are FSW process parameters need further investigation. A more thorough discussion is needed.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 3 Report
- Why you choose this Special Issue? The article no contains nothing of corrosion.
- Add more current references (2020 – 2021).
- Add DOI for each article on references. Make uniform the bibliography, they are written in many ways, check suggestion from the Coatings manuscript.
- Improve the introduction with data about application for Al-Fe plates from the literature.
- Which is the novelty of the work?
- What is the status of the literature according to your work? Make a comparison between the results obtained by you and other previous research.
- Figure 1. Make the image clearer, at a higher resolution. Delete the numbering a) and b) at the top of the image
- Figure 2. Number the pictures and add explanations.
- Figure 3. Number the pictures and add explanations.
- Figure 5. Number the pictures and add explanations.
- Figure 6. Number the pictures and add explanations.
- Figure 7. Number the pictures and add explanations.
- Figure 8. Number the pictures and add explanations.
- Figure 9. Number the pictures and add explanations.
- Figure 11. Add explanations for a) and b).
- Figure 15. Number the pictures and add explanations.
- Add more conclusions
- Generally, the quality of the writing could be improved.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 4 Report
Overall, the paper is very poorly and carelessly written. Many sentences do not make any sense from English language point of view. Most of the time, there is no coherency and flow in the information provided by the authors, which has made their work very difficult to understand. The authors have demonstrated a very poor level of English proficiency and scientific writing. The paper MUST be re-written completely and accessed by someone proficient in English.
Line 11: “In this study, using friction stir welding ….welding speed of 400 mm/min.” The first sentence is too long and not clear. Rewrite it please. Avoid using long sentences, as it makes it difficult to understand/read them.
Line 17: “The lower tool offset only forms 2 Micron…” use small m for microns.
Line 36: “…have been often used in various applications” mention the applications with references.
Line 39: “the thickness of the intermetallic compound (IMC)” authors did not provide any background which IMC they are talking about? And how it is formed?
Line 40-43: “Therefore, the combi-40 nation of the above two materials has attracted….” This is again out of context. Authors must provide a scientific background from literature before making such a statement.
Line 52 – 53 is one sentence, which is almost impossible to understand. Use short meaningful sentences. Same problem for Line 60-63. “X. Liu 60 et al….”
Line 63 and Line 66: “and a higher rotational speed can increase the strain rate of the 63 material under the normal rotational speed.” and “a higher rotational speed under conventional rotational speed” not clear at all what is the meaning of “under”.
Line 75 -77: “High rotational speed micro friction sti…..receiving more and more attention.” These are written in a way that these are disconnected sentences. The is a lack of flow and coherence in the writing style of the authors, which has made their work very difficult to understand.
Line 79 – 81: Again very poor sentence structuring and flow, I am unable to understand what is beneficial to the engineering applications.
In the introduction section authors have not defined any range of rpm for HRW and for Ultra-HRW from literature.
Line 82 – 84: The sentence does not make any sense from English point of view.
Line 85-86“welding brass（H62）and copper（T2）with thickness of 0.6 mm…” whose thickness is 0.6 mm? Brass or copper or total thickness?? Is Zhang et at work on HRW or Ultra-HRW?
Line 88-89: “the effect of the welding process parameters of 88 the thin plate on the quality of welding was greater….” wrong sentence, must be rewritten correctly.
Line 103: “However, in all the above-mentioned studies, Al-Fe welding has been studied…” Not at the above discussed studies are for Al-Fe!
Overall, the introduction is very poorly written. There is no coherency and flow in the introduction. Authors have demonstrated very poor level of English proficiency. The introduction MUST be re-written completely and accessed by someone proficient in English.
Line 123: “the FSW.As” add a space
Line 127: “and a certain degree of plasticity.” Is the tool plasticity required in FSW process? Add explanation WHY?
Line 128: “et al[6].” Inconsistent reference citation format.
Line 130: Define RS before first use.
Line 134: “Fig. 2.Because” add a space.
Line 140: “Because the thermal conductivity of alumi-140 num alloy is much higher than that of steel,…” Which steel? Rephrase the whole sentence accordingly.
Line 142-143: “the hole circled in red in Fig. 1 is 142 inserted into the K-type thermocouple,…” So did the thermocouple go in the hole or did the hole go into the thermocouple?
Line 143: Which standard authors followed to choose the 3 mm distance and WHY?
Line 146: “signals were synthesized…” We do not synthesize the signals…do not know what authors meant by synthesized here?
Line 148: “in this study is a new type of HRS-FSW equipment developed….” If the equipment was HRS only than how it was used for Ultra-FSW?
Line 156-157: “was set as 18000 rpm -400 mm/min in Ultra-HRS FSW…” what 1800 rpm – 400 mm/min means?
Line 153 – 157: Based on what the welding parameters were selected?
Line 162-163: “Zeiss high temperature metallographic microscope….” Define what is a high temperature microscope??!! I never heard of it. If there is no Zeiss high temperature metallographic microscope, then this shows how carelessly the paper is written.
Line 165 – 168: “The size of the working electrode…” What this process is used for? The previous sentence is talking about the SEM and this next sentence about electrodes?
Line 170: Which ASTM standard or other standard was followed for tensile test?
Line 171: “The microhardness at the top, middle and bottom in the thickness direction…” Provide more specific details (dimensions) what is meant by top and bottom?
How authors have compared the results of HRS with Ultra-HRS because both use different welding speeds along with the different rotational speeds of course? So two parameters are varying at the same time. Why authors have not used the same welding speed for HRS with Ultra-HRS? This must be elaborated in the paper.
Line 181 – 188: Due to poor English usage, poor sentence structuring it is unclear what authors are trying to communicate here.
At this point, I will stop my review because it is not possible for me to understand the paper because of the lack of adequate English standards required for scientific writing.
The paper must be re-written completely following the standard of scientific writing.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
The paper has been improved, it can be published.
Reviewer 4 Report
Avoid using repetition of the same words in the title, e.g., rotational speed is used twice. The suggested title is
On the effects of high and ultra-high rotational speeds on the strength, corrosion resistance, and microstructure during friction stir welding of AL 6061-T6 and 316L SS alloys
Overall, the authors have addressed the comments satisfactorily.
