Influence of Heat Treatments, Parameters and Machining Conditions on Machinability in the Turning of Recycled 6061 Aluminum Alloy

Round 1

Reviewer 1 Report

Figure 2: Are the black dots paint additionally into images? If yes, maybe, the circles might be more appropriate. Or are the black dots some inclusions? How is the porosity? How many pores are in area/volume? Can you estimate that? Pores are unwanted as decreasing the mechanical properties. Letters (a) and (b) are too large compared to text.

For how purposes is the recycled aluminium alloy intended? Can you compare the yield stress and/or ultimate stress for virgin 6061 and recycled aluminium alloy?

Tables 1, 7, 8: In the pdf file of a manuscript, the tables are damaged  (columns are in several lines). Please, check it.

Line 132: /8 ", 100kgf. Please, use SI units.

Table 2: Is there some conversion table between HRE and standard units of hardness, i.e. HB, HRC, HRB, HV?

Figure 3: Caption is in French.

Lines 233, 237, 277, 280,317, 320: Please, check captions of figures.

The comparison of your results with virgin aluminium would be beneficial.  

The mass concentration of the metal particles – how is it in the case of virgin aluminium alloy. Is it a specific quantity for a recycled aluminium alloy?

 

Figures with graphs should be of higher resolution.

There are two terms for f: Advance and feed rate, in the manuscript. Please, unify.

Preferably cutting speed is v_c (small letter v, c lower index).

Shavings and chips, Do you want to express some difference that you use two different words?  

Author Response

• Figure 2: The black dots in these images are indeed inclusions, which make up the pores we are talking about. The quantification of these pores has not been studied. Here, it is simply a question of pointing out its inclusions. The size of letters (a) and (b) has been reduced. The word diameter will be removed. In fact, this is the longer side.
• Recycled aluminum alloy is intended for many uses. In our research axis, we want to use these alloys for the manufacture of mechanical parts. This is why we are studying their machinability.
• Tables 1, 7, 8 have been readjusted. Regarding the elastic limit resistance comparison and / or ultimate stress between virgin and recycled 6061 alloy, an experimental study is currently underway.
• Line 132: The modification is made, everything is written in standard units kgf in N, inch in mm and HRE in HV.
• Figure 3 has been corrected.
• Lines 233, 237, 277, 280, 317, 320: the legend has been modified.
• Comparison between recycled alloy and virgin alloy

The surface roughness of these recycled alloys has been compared to that of the virgin alloy. Note that for the virgin alloy and the recycled alloy, the lead is the common factor with the greatest significant influence. But, machined under the same conditions, the surface finish of the virgin alloy is much better. The surface finish of the machined 6061 R-T6 alloy with lubrication approximates that of the virgin alloy.

 

The mass concentration of metal particles of these recycled alloys has been compared to that of the virgin alloy. Machined under the same conditions, the mass concentration of the metal particles has practically the same evolution, but the production of these particles is higher for the virgin alloys.

 

The morphology of the chips was also compared and a big difference was observed when the machining is done under the same conditions. The virgin alloy chips are long, they do not break quickly, and they deteriorate the surface finish. In contrast, the shavings of the recycled alloy are shorter for the recycled alloy.

 

• Graphics resolution has been improved.
• Between the terms forward and forward speed, unification has been made. We consider the term advance.
• The cutting speed symbol has been changed.
• No difference is expressed between Chips and Chips.

Reviewer 2 Report

Authors have improved the paper with many changes and the information is presented ina  better way. Results discussion have been rewritten and presented in a better way. The paper can be published.

Author Response

• Figure 2: The black dots in these images are indeed inclusions, which make up the pores we are talking about. The quantification of these pores has not been studied. Here, it is simply a question of pointing out its inclusions. The size of letters (a) and (b) has been reduced. The word diameter will be removed. In fact, this is the longer side.
• Recycled aluminum alloy is intended for many uses. In our research axis, we want to use these alloys for the manufacture of mechanical parts. This is why we are studying their machinability.
• Tables 1, 7, 8 have been readjusted. Regarding the elastic limit resistance comparison and / or ultimate stress between virgin and recycled 6061 alloy, an experimental study is currently underway.
• Line 132: The modification is made, everything is written in standard units kgf in N, inch in mm and HRE in HV.
• Figure 3 has been corrected.
• Lines 233, 237, 277, 280, 317, 320: the legend has been modified.
• Comparison between recycled alloy and virgin alloy

The surface roughness of these recycled alloys has been compared to that of the virgin alloy. Note that for the virgin alloy and the recycled alloy, the lead is the common factor with the greatest significant influence. But, machined under the same conditions, the surface finish of the virgin alloy is much better. The surface finish of the machined 6061 R-T6 alloy with lubrication approximates that of the virgin alloy.

 

The mass concentration of metal particles of these recycled alloys has been compared to that of the virgin alloy. Machined under the same conditions, the mass concentration of the metal particles has practically the same evolution, but the production of these particles is higher for the virgin alloys.

 

The morphology of the chips was also compared and a big difference was observed when the machining is done under the same conditions. The virgin alloy chips are long, they do not break quickly, and they deteriorate the surface finish. In contrast, the shavings of the recycled alloy are shorter for the recycled alloy.

 

• Graphics resolution has been improved.
• Between the terms forward and forward speed, unification has been made. We consider the term advance.
• The cutting speed symbol has been changed.
• No difference is expressed between Chips and Chips.

 

Round 2

Reviewer 1 Report

In the previous review, it was written: Shavings and chips, Do you want to express some difference that you use two different words? The answer is: No difference is expressed between Chips and Chips. However, in text there are still "shavings" and "chips" used.

The resolution of Figures 3-9 is still low.

Figure 3 would show shorter measure length and more detailed. 

The topic of the paper is interesting and actual. A large portion of work was done. The presentation would be better.

 

Author Response

Indeed there is no difference between the words Chips and chips. Lines 577, 606 and 639 chips with the word capital letter C, because we believe this is the beginning of sentences. We have also pluralized all the words "chip".

The resolution of Figures 3 to 9 has been completely revised.

Figure 3 has been modified. The measuring length depends on the stroke of the probe of the measuring device.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript evaluated the machinability in turning of recycled 6061 aluminum alloys from surface roughness, mass concentration of metal particles and chips morphology and analyzed the influence of heat treatments, cutting parameters and machining conditions. However, this manuscript looks like an evaluation report, with no innovative research methods and mechanisms. So I don’t recommend publication in this journal.

Reviewer 2 Report

In this work, the authors study the machinabiliy of two recycled aluminum alloys in turning opetrations. They analyze the influence of the cutting parameters, the lubrication and the heat treatments.

The document is well organised, easy to follow and with clear desciption of the methodology and the results. However english should be reviewed because I found some sentences grammatically incorrect, in particular in the introduction section (i.e line 101 "At the end of .....")(line 104 "... bars in the process IS shown...")

Graphics and table are clear but one of the recommendations is to change the captions but in most of the cases they are too simplified. I.e. in Table 1 change "chemical composition" by "chemical compostion of recycled aluminium alloys" or somenthing similar. Also in this table the simbol % should be added. In table 2, change the caption by "hardness measured for each recylced aluminum alloy" and the caption in table 3 by "Cutting parameters used in the experimentas tests" or similar. These are some examples but please, review all  captions because some of them should be improved.

In line 115 you mentiones that allys have pores of different sizes and shapes. Please include this information of the pores because in the Figure 2 they look equal for both cases. Include some numercial information and try to expalin how the pores size is related with the material hardness becuase in line 123 you say this is related with pores. How?

Line 125 type Table 1 and not Table I.

In line 132 again you mention that the pores in recycled alloys are larger than pores found in normal alloys. Quantify it please. How much longer? Is it relevant in the properties? etc.

What is the criterion to stablish the cutting parameters in Table 3?

The hardenss and roughness values measured in the material should include the standar desviation if they are measured more than once. Or at leats, the error of the measure.

I do not understand in Table 4 why some cutting conditions are repeated and others are not. Also I recommed to included the statistical analysys tables.

In the conclusion sections, the results that are discussed are clearly those expected due to the existing literature. What are the results that this study provides as novel?

Reviewer 3 Report

Please, check the manuscript in accordance with the template.

English technical terms should be corrected. For example, please, make clear in the use of words advance and feed, and others.

The English language has to be edited.

MQL abbreviation is not explained.

Figure 2: A scale factor is missing. Maybe, it is not visible.

Symbols in equations are not explained.

Some roughness profile of the measured sample/s would be appropriate to show.

Table 1: Units are unknown.

Table 2: Why do you use unit HRE?

The cutting tool should be described in detail. Indication: CPGT09T308HP is not enough suitable for a manuscript.

Table 4: Units are unknown.

Line 209: „Models 6 to 9 ...“ Does it mean a number of samples? If yes, it should be mentioned in section 2. Materials and Methods. However, in that section in line 137 is mentioned „The tests were carried out on six identical samples ...“

Figure 7: The vertical axis of the graph is Ra, units micrometres. Do you think it is right? Ra 4000 μm??? Why did you use the only feeds up to 0.2 mm/rev?

Figure 8: Please check the vertical axis.

Figure 9: The photos should be improved.

The conclusions are too general. The contribution of a manuscript is not clear.

The first part of the study is the evaluation of the presence of pores before and after heat treatment. The meaning of this part of the study is lost in the rest of the manuscript.

The comparison of your results with virgin aluminium would be beneficial.