Welding Properties of Dissimilar Al-Cu Thin Plate by a Single-Mode Fiber Laser
Round 1
Reviewer 1 Report
This manuscript studied the weld shape, joint cross-sections, composition distribution, and the tensile shear strength of Al–Cu dissimilar metal laser welding by 5 kW single-mode laser. The effects of the laser-irradiated base material and the welding speed were detailed analyzed. Even though the article's subject and content are interesting, there are some significant issues with the results and conclusions that the authors should address before the paper could be considered for publication. Please consider the following comments and open questions.
1. The paper is more focused in the influence of the laser-irradiated material to Cu or Al. But the paper doesn’t obtain a sound weld, how to obtain an optimum welding parameters?
2. In different welding parameter, why the change of shear performance is not obvious?
3. In this paper, why the single-mode laser was used in Al–Cu dissimilar material welding?
4. In the case of Al–Cu dissimilar welding, why does the majority of pores form inside the Al layer. Please explain the reason by experiment analysis.
Author Response
Thank you for your comments and suggestions. The manuscript has been revised and changed according to your suggestions. Responses to your comments are listed below.
This manuscript studied the weld shape, joint cross-sections, composition distribution, and the tensile shear strength of Al–Cu dissimilar metal laser welding by 5 kW single-mode laser. The effects of the laser-irradiated base material and the welding speed were detailed analyzed. Even though the article's subject and content are interesting, there are some significant issues with the results and conclusions that the authors should address before the paper could be considered for publication. Please consider the following comments and open questions.
1) The paper is more focused in the influence of the laser-irradiated material to Cu or Al. But the paper doesn’t obtain a sound weld, how to obtain an optimum welding parameters?
Response: The optimal welding parameters were found to be 400 mm/s with Al on top and 400-800 mm/s with Cu on top. Through these results, it was confirmed that welding at a wider range of speed is possible when laser is irradiated to Cu than when irradiated to Al. In order to find more accurate parameters in terms of strength, we plan to experiment with thicker specimens so that the base material does not break easily.
2) In different welding parameter, why the change of shear performance is not obvious?
Response: The reason why the change in shear performance is not obvious is mostly because of good welding. The change in performance is not obvious because the fracture occurred earlier in the Al than in the joint. We confirmed that the thickness of the base material was necessary compared to the range of joint area, and we plan to design an experiment to check the change in shear performance without breaking the base material.
3) In this paper, why the single-mode laser was used in Al–Cu dissimilar material welding?
Response: At the same output, the reflectivity of Cu is higher than that of Al, so even if Al absorbs the laser and melts, Cu may not melt. It was used to weld both Cu and Al at the same power by increasing the energy density of the laser beam.
4) In the case of Al–Cu dissimilar welding, why does the majority of pores form inside the Al layer. Please explain the reason by experiment analysis.
Response: In the 4.1 Molten pool part, the formation of pores and molten pools in the weld area, which is related to the process in which pores are formed inside Al, has been described.
Revisions to all suggestions were reflected in the revised paper.
Reviewer 2 Report
Dear Authors,
I have reviewed your paper titled: "Welding Properties of Al–Cu Thin Plate Dissimilar Welding Using a Single-Mode Fiber Laser".
The paper fulfils the aims and scope of Metals journal, and can be considered for potential publication. However, it needs some improvements. I have some minor suggestions, which are listed below.
General remarks:
- Please add the quantitative results into the abstract.
- You have presented 24 references. Only 7 of them have been published in last three years. I suggest to support your work with newly published references more. It will increase the visibility of your work in scintific databases
Introduction:
- Line 45 " identical materials" - I propose change to "materials from the same material group".
- One of th newly described methods, which allow to join dissimilar materials is usage of a high entropy alloys as a filler material during laser welding (e.g., https://doi.org/10.3390/app12062849).
- Please underline the novelty of your work. What new has been propoed in this investigations?
Materials and Methods:
- I propose to change the order of 2.1. and 2.2.. Following the name of the paragrapth, materials should be described firstly.
- Table 1 - please describe, why these parameters were used. It should be clear for potential readers.
- Section 2.2. - please list basic mechanical properties of used metals (yield point, mechanical properties, elongation).
- Macroscopic and microscopic tests are standarized tests. However, I cannot find any information about used standard(s). Please list them.
Results:
- Fig. 2 - except "porosity" other welding imperfections could be observer. Please nam them in the picture. Moreover, they should be described in the text (lines 136-156). Now, the description is not connected with pictures.
- Subsection 3.2.2. - I cannot find any analysis of fractures. Please show broken surface for analysis. Now, I cannot find prove about type of fracture. Especially Fig. c, in which crack appeared in weld metal. What type of fracute was observed?
Discussion:
- Please support equation with relevant reference.
- Part is described very well.
Conclusions:
- Please list the most imporatnt conclusions in points. Moroever, they should be supported with the quantitative results. It will be more readable for potential readers.
Author Response
Thank you for your comments and suggestions. The manuscript has been revised and changed according to your suggestions. Responses to your comments are listed below.
I have reviewed your paper titled: "Welding Properties of Al–Cu Thin Plate Dissimilar Welding Using a Single-Mode Fiber Laser".
The paper fulfils the aims and scope of Metals journal, and can be considered for potential publication. However, it needs some improvements. I have some minor suggestions, which are listed below.
General remarks:
1) Please add the quantitative results into the abstract.
Response: Quantitative results were added to the abstract and revised throughout.
2) You have presented 24 references. Only 7 of them have been published in last three years. I suggest to support your work with newly published references more. It will increase the visibility of your work in scintific databases.
Response: 5 newly published references were added to the paper, and the contents of the references were added to the manuscript.
Introduction:
3) Line 45 " identical materials" - I propose change to "materials from the same material group".
Response: The manuscript has been revised according to your suggestion.
4) One of th newly described methods, which allow to join dissimilar materials is usage of a high entropy alloys as a filler material during laser welding (e.g., https://doi.org/10.3390/app12062849).
Response: It was mentioned in the text with reference to the brazing using the high entropy alloy you suggested. In this experiment, no filler metal was used, but the use of filler metal is positive in terms of damage to the Al base material.
5) Please underline the novelty of your work. What new has been propoed in this investigations?
Response: There have already been many studies on the dissimilar welding of Al-Cu. However, in most studies, the laser was irradiated to Al rather than Cu to weld. This is because it is difficult to reach sufficient heat input due to the high reflectivity of Cu. In terms of thermal damage, irradiating a laser to Cu rather than irradiating a laser to Al may be advantageous in terms of damage to the base material.
Of course, research on Cu-Al dissimilar welding by irradiating a laser on the Cu side is also being conducted in various ways. When performing dissimilar welding by irradiating Cu with laser, coating Ni on the copper surface for bonding, controlling laser pulses, using wobble pattern, or brazing using filler metal is used.
In this study, a high-quality, high-density single laser was used and the laser was irradiated to Cu with a thin plate capable of welding with at least the amount of heat input to perform dissimilar welding. Weldability was studied when irradiating a laser to Cu and irradiating Al with a similar heat input without any treatment on Cu.
Materials and Methods:
6) I propose to change the order of 2.1. and 2.2.. Following the name of the paragrapth, materials should be described firstly.
Response: The order of 2.1. and 2.2. have been changed so that the material part is described firstly.
7) Table 1 - please describe, why these parameters were used. It should be clear for potential readers.
Response: The experiment was carried out by decreasing the welding speed by 200mm/s from the speed of 1000mm/s, where welding was not possible. The above has been added to the paper.
8) Section 2.2. - please list basic mechanical properties of used metals (yield point, mechanical properties, elongation).
Response: The mechanical properties are listed in Table 1.
9) Macroscopic and microscopic tests are standarized tests. However, I cannot find any information about used standard(s). Please list them.
Response: The referenced standard test (ISO 14329:2000) is list in the text.
Results:
10) Fig. 2 - except "porosity" other welding imperfections could be observer. Please nam them in the picture. Moreover, they should be described in the text (lines 136-156). Now, the description is not connected with pictures.
Response: Other Welding imperfections are named to Fig. 2 and these are described in the text.
11) Subsection 3.2.2. - I cannot find any analysis of fractures. Please show broken surface for analysis. Now, I cannot find prove about type of fracture. Especially Fig. c, in which crack appeared in weld metal. What type of fracute was observed?
Response: Subsection 3.2.2 describes the fracture part rather than the analysis of the fracture. The text has been edited to fit the content.
As a type of fracture, it was confirmed that ductile fracture was caused by necking at Al fracture. In addition, please see the attached fracture surface photos.
Discussion:
12) Please support equation with relevant reference.
Response: Unfortunately, it takes more time to apply and support the equations of relevant references to this paper.
- Part is described very well.
Conclusions:
13) Please list the most imporatnt conclusions in points. Moroever, they should be supported with the quantitative results. It will be more readable for potential readers.
Response: The conclusion section has been revised to be more concise and contain the quantitative results.
Revisions to all suggestions were reflected in the revised paper.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
In this study, Al–Cu dissimilar welding was performed using a 5 kW single-mode laser. The effect of welding parameters on the sectional morphology and the mechanical properties were investigated.
The title is suggested as “Welding Properties of Dissimilar Al–Cu Thin Plate by a Single-Mode Fiber Laser”
Introduction Section, the novelty and necessity of the work was not elaborated clearly. What is the gap between existing wore and authors’ work?
Page 2, Line 87, “The wavelength of the laser beam was 1070 μm” . “1070 μm” should be “1070 nm” ?
For Figure 2, how to define “length of the melted Al area”. From the figure, the length is not uniform.
For Table 2, the unit of the variables should be given. For the tensile shear strength, how many samples were tested for each set of parameters? In addition, how to calculate the contact area?
For Figure 4, the welding parameters should be given.
Section 3.2.2. “Fracture cross-sectional analyses” was suggested as “Fracture morphology”.
Conclusion Section, the content is not concise and conclusive enough.
The English needs to be improved further.
Author Response
Thank you for your comments and suggestions. The manuscript has been revised and changed according to your suggestions. Responses to your comments are listed below.
In this study, Al–Cu dissimilar welding was performed using a 5 kW single-mode laser. The effect of welding parameters on the sectional morphology and the mechanical properties were investigated.
1) The title is suggested as “Welding Properties of Dissimilar Al–Cu Thin Plate by a Single-Mode Fiber Laser”
Response: The manuscript has been revised according to your suggestion.
2) Introduction Section, the novelty and necessity of the work was not elaborated clearly. What is the gap between existing wore and authors’ work?
Response: There have already been many studies on the dissimilar welding of Al-Cu. However, in most studies, the laser was irradiated to Al rather than Cu to weld. This is because it is difficult to reach sufficient heat input due to the high reflectivity of Cu. In terms of thermal damage, irradiating a laser to Cu rather than irradiating a laser to Al may be advantageous in terms of damage to the base material.
Of course, research on Cu-Al dissimilar welding by irradiating a laser on the Cu side is also being conducted in various ways. When performing dissimilar welding by irradiating Cu with laser, coating Ni on the copper surface for bonding, controlling laser pulses, using wobble pattern, or brazing using filler metal is used.
In this study, a high-quality, high-density single laser was used and the laser was irradiated to Cu with a thin plate capable of welding with at least the amount of heat input to perform dissimilar welding. Weldability was studied when irradiating a laser to Cu and irradiating Al with a similar heat input without any treatment on Cu.
3) Page 2, Line 87, “The wavelength of the laser beam was 1070 μm” . “1070 μm” should be “1070 nm” ?
Response: "μm" is corrected to "nm".
4) For Figure 2, how to define “length of the melted Al area”. From the figure, the length is not uniform.
Response: The region of molten Al was defined by EDS as the portion containing a trace amount of copper inside the aluminum. The length of the molten area was measured as the length of the part where the Al was exposed to the outside. The length of the molten Al region is the average of three random point measurements of the joint.
5) For Table 2, the unit of the variables should be given. For the tensile shear strength, how many samples were tested for each set of parameters? In addition, how to calculate the contact area?
Response: The unit of the variable is indicated. For each parameter, the tensile shear strength was tested three times. This collections have been added to the manuscript.
The strength of laser welding is determined by the contact area, chemical composition of joint and defects in the joint. Unlike other welding, it is affected by the laser beam size, so the control of the contact area is limited. Depending on the welding conditions, the bonding strength increases as the contact area increases. Although the area of ​​the contact can be calculated through cross-section, dividing the measured strength by the contact area resulted in the same strength of all specimens. This is because the contact area has a much greater effect on the bonding strength than the other factor.
The IMC existed in the joint became a major variable in determining the fracture area and had no significant effect on the strength compared to the contact area. For this reason, the tensile shear strength is not divided by the contact area, only the force is measured and shown in the table.
6) For Figure 4, the welding parameters should be given.
Response: The welding parameters were added to the manuscript.
7) Section 3.2.2. “Fracture cross-sectional analyses” was suggested as “Fracture morphology”.
Response: The manuscript has been revised according to your suggestion.
8) Conclusion Section, the content is not concise and conclusive enough.
Response: The conclusion section has been revised to be more concise.
9) The English needs to be improved further.
Response: By requesting an English editing company, the overall English of the manuscript has been improved. Please see the attachment.
Revisions to all suggestions were reflected in the revised paper.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I think that the author has dealt with all of the points raised by reviewer. The work discusses the weldability and mechanical properties of dissimilar Al-Cu thin plate by a single-mode Fiber laser, and it is suggested to be accepted for publication.
Reviewer 3 Report
The authors answered the questions from the reviewer and made corrections based on the comments, and the manuscript can be accepted now.
