The Microstructure and Mechanical Properties of 5083, 6005A and 7N01 Aluminum Alloy Gas Metal Arc-Welded Joints for High-Speed Train: A Comparative Study

Round 1

Reviewer 1 Report

The paper titled “The Microstructure and Mechanical Properties of 5083, 6005A 2 and 7N01 Aluminum Alloy Gas Metal Arc Welded Joints for 3 High-speed Train：A Comparative Study” fits the scope of journal it is interesting and written very well, the paper can be accepted after minor revisions.

The following my comments:

Line 129: the authors state : “The tensile strength was tested at 128 room temperature with a strain rate of 2 mm/min”, I think that the tensile tests were carried out in displacement control therefore the authors should change their sentence with “The tensile tests were carried out in displacement control with crosshead speed of 2 mm/min”.

The authors should give more information about tensile test. The capacity of load cell, the testing machine, if they used extensometer to measure the strain.

The caption of figure 11 is wrong. Change “(a)(b) 5083; (c)(d) 6005A; (e)(f) 7N01” with “(a)(d) 5083; (b)(e) 6005A; (c)(f) 7N01” also in the text lines 289-295 there is the same error.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper systematically discusses the microstructural and mechanical properties of three types of welded commercial Al-alloys.

The article has been properly prepared, modern characterization methods have been used, and the latest literature in this field has been studied. The introduction, main explanation and summary are clearly described.

 The article is primarily a professional study and has less scientific input. The results are expected.

I give some recommendations that the authors can use in this or in future studies.

2. Table1: How the chemical composition of the alloys was determined, or only the supplier's information is given.
3. Some detailed information about the equipment is missing: Type of scanning microscope and EBSD detector, DSC and tensile machine.
4. the title 3.1 Morphology of macrostructure is not precise and I suggest three other variants:

• Morphology of macrostructural components
• Macrostructure of the weld 
• Macrostructure

4. Microstructural characterization was done at low magnifications with SEM and large magnifications with TEM. Microstructural analysis is insufficient, mainly phase analysis is missing. Types of precipitations have been identified, other phases are given only descriptively (eutectic, dendritic ...)
5. Measuring the microhardness in one or more lines over the weld as prescribed by standards for scientific purposes is not sufficient. Comprehensive information on the microhardness of the weld can be obtained with a network of measurements with micro- or nanoindentation (microhardness map).

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The Microstructure and Mechanical Properties of 5083, 6005A and 7N01 Aluminum Alloy Gas Metal Arc Welded Joints for High-speed Train：A Comparative Study’. Work is described in a good manner with good novelty. Suggestions are listed below:

1. The abstract section is written poorly. Remove the unnecessary information and add the key finding of the works.
2. Discuss the novelty and application of the work in a separate section.
3. The introduction section is very weak. Try to add a few current published works and make a bridge between previously published work with current work. Add a few currently published works.
4. Provide the image of the experimental setup and welded plate.
5. The selection of the groove design is not clear. Provide a detailed description of groove selection.
6. Provide the mechanical properties of each material in a separate table.
7. The details about tensile test specimens and testing parameters are missing.
8. Discuss the mechanism of the PMZ formation.
9. Improve the quality of the optical image, i.e., HAZ. If possible, provide an SE image instead of an optical image.
10. The major problems come across the interface region but detailed discussion about the interface is missing. Provide the elemental analysis across the interface. How will it affect the mechanical properties? Refer to the following: 10.1016/j.matchar.2011.02.003; https://doi.org/10.1016/j.ijpvp.2021.104443.
11. In the stress-strain curve, the PLC effect mainly comes at a slow strain rate. However, in the present investigation the extension rate was 2 mm/min. Still, the author gets the PLC effect. Discuss it in detail.
12. Provide the tensile test results in a separate table and also add the joint efficiency results: https://doi.org/10.1016/j.jmapro.2019.10.002. From Fig. 10 it is not clear whether the sample was standard or not.
13. Provide a detailed discussion about the fracture surface: Dimples, cleavage facets and voids are not marked properly in the figure. Also, the test results and fracture surface study shows the ductile fracture while from the fractured specimen as the ductile fracture is associated with neck formation. Discuss it in detail. Refer to the following: https://doi.org/10.1016/j.engfailanal.2008.09.003; https://doi.org/10.1016/j.engfailanal.2017.06.044;
14. Mark each region of the weldments in hardness variation with proper discussion. Try to relate the hardness and tensile test results with the microstructure evolution.
15. Discuss the softening mechanism in 6005A.
16. Shorten the length of the conclusion section.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Revision is satisfactory and can be accepted for publication. 

Author Response

Thank you very much for your comments on our manuscript.