Effect of Rotational Speed on Static and Fatigue Properties of Rotary Friction Welded Dissimilar AA7075/AA5083 Aluminium Alloy Joints

Round 1

Reviewer 1 Report

Comments:

1. Fig 5. is dimension: "9" should be "Φ9"
2. Fig 6. is dimension: "8" should be "Φ8"
3. Introduction should be extended to the issues of numerical analysis of the friction welding process. Add some references in this scope, for example:

M. Maalekian, E. Kozeschink, H. P. Brantner, and H. Cerjak, “Comparative analysis of heat generation in friction welding of steel
bars,” Acta Mater., 56, No. 12, 2843–2855 (2008);

A. Vairis, G. Papazafeiropoulos, and A. M. Tsainis, “A comparison between friction stir welding, linear friction welding, and rotary friction
welding,” Adv. Manuf., 4, 296–304 (2016);

E. Bouarroudj, S. Chikh, S. Abdi, and D. Miroud, “Thermal analysis during a rotational friction welding,” Appl. Therm. Eng., 110, 1543–1553 (2017);

Łukaszewicz A. "Nonlinear numerical model of heat generation in the rotary friction welding", Journal of Friction and Wear, Vol. 39 (6), 476-482 (2018);

Łukaszewicz A. "Temperature field in the contact zone in the course of rotary friction welding of metals", Materials Science, Vol. 55 (1), 39-45 (2019);

Author Response

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Reviewer 2 Report

This paper focuses on the effect of rotational speed on microstructure, strength and fatigue behaviours of rotary friction dissimilar AA7053/AA5083 weld joint.

This topic is important considering the increasing application of welded components. The existing literature is actual and it is well cited.

The paper contains the results of experimental research. Overall, it is a very interesting contribution to the field of rotary friction welding of aluminium alloy rods. I would like to recommend this paper for publication in "Metals" journal after revision.

1. The temper state of aluminium alloys tested should be specified. It allow others to replicate and build on published results.
2. Table 2: Has the method for testing basic mechanical properties been standardized? Please explain how many repetitions were done. If possible, include some statistical analysis.
3. Section 2.1: The place of hardness measurement has not been indicated. Did the samples show an isotropy of the mechanical properties on the cross-section?
4. It is not completely explained why rotating speed with constant values of the rest parameters was changed.After all, the heating temperature and the strength of the joint may strongly depend on the friction time or forging pressure.It is better to use Design of Experiment to find optimal welding parameters.
5. It is not known why the well-known analytical equations (3) - (5) were added in the section presenting the results.After all, the authors did not use these equations.
6. Lines 230-231: The authors sat that "It can be seen that an increase in the rotational speed increases burnt-off length [...]". It is a trivial conclusion since the burnt-off length may be reduced by reduction in friction pressure or forging pressure. See my comment no. 4.
7. Figure 17: Description of subfigures (a)-(d) should be included in caption.
8. Conclusions should be improved in term of future direction of research.
9. Several abbreviations have been defined many times in the manuscript. One definition is sufficient.
10. The „Results and Discussion” section: The discussion of the results should be more strongly supported by information from the literature.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Current work aims at exploring the relationship between rotational speed and the properties of dissimilar AA7075/AA5083 RFW joints, which can be helpful to optimize welding parameters. To make the current work more convincing and informative, authors need to address the comments. Some paper writing norms deserve more attention as well.

1. Authors should use the past tense when citing others’ literature and stating their research. For examples: “Results show that at higher rotational speeds, typically 540 rpm or above, the dissimilar AA7075/AA5083 rotary friction weld joints reveal static fracture in the AA5083 base metal side indicating the joint efficiency is more than 100% (line 17-19).”, “Subsequently, the work of Uday et al. [15] suggests that … (line 60-62)”. Authors should check the manuscript carefully.
2. Some grammatical errors can be found in the manuscript, such as “In this work, dissimilar rotary friction welding of AA7075/AA5083 aluminium alloy rods having diameter of 15 mm was performed at varying rotational speeds …(line 12-13)", “Some researchers [24, 25] have studied fatigue behaviours of rotary friction welded 6061 aluminium alloy joints with the results show that the fatigue strength of the weld joint is slightly lower than that of 6061 aluminium alloy base metal and the fracture origin occurs near the weld interface. (line 74-77)” Other errors are not listed here.
3. There are some errors about the use of abbreviation, authors should use abbreviation in the following description after it is first defined, such as rotary friction welding (RFW).
4. Please use the researchers’ name directly instead of “other researchers” when authors cite reference 14. (line 57-60)
5. Please condense the introduction section and reorganize it to be more logical, some expressions are not necessary in this paper, such as the basic process of RFW. The detail application of AA7075/AA5083 structure needs to be clearly addressed in the introduction. Please emphasize the novelty in the introduction and explain what scientific issues are this research focused on.
6. It is not necessary to place Figure. 2 in this paper because there is no special design in this equipment. Likewise, the description of this equipment can be omitted. Fig. 5 and Fig. 6 can be merged.
7. Line 277-280 has already been mentioned before. Repeating it is not necessary.
8. Different zones can be indicated in Figure 11, Figure 13 and Figure 17 (b). In addition, to manifest the grain refinement and analyze more detailed characteristics, SEM or EBSD should be considered because OM is not enough.
9. The analysis of AA7075 precipitation does not have any explanation. Authors should provide relevant data and description.
10. In this paper, the mechanism of fatigue fracture is not clear enough. Authors should discuss microstructure, residual stress and fatigue fracture together in more details.
11. Current work lacks innovation. Authors should emphasize the novelty of current work and explore more novel ideas in this experiment.

12.  Some of the references are out-of-date. Checking the following new paper may be useful to your manuscript.   https://doi.org/10.1016/j.corsci.2021.109800

Author Response

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Author Response File: Author Response.pdf