Effect of Deep Cryogenic Treatment on the Artificial Aging Behavior of 6082 Aluminum Alloy

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors, this paper indeed is very interesting, and the cryogenic treatments on aluminum alloys of the 6000 series family concerns to a very useful enhancement approach. However, some minor revisions are required for publishing in this prestigious journal:

1.      The chemical composition of the alloy is reported, however it is unclear whether this composition was acquired from a data sheet or through tests conducted by the authors.

2.      Although it is evident that the sample geometry corresponds to test standards, presumably the ASTM E8 or its ISO equivalent, there is no reference to the specific standard used. Please accurately cite the standard.

3.      The heat treatments were performed using two different furnaces. While the authors mention the type of furnaces, they do not clearly state whether these furnaces were lab-made or of a specific brand. This information is vital for readers who might consider using same equipment for their own treatments.

4.      The cryogenic treatment process is performed in a liquid nitrogen container. It is assumed that this is a common nitrogen container, but it is better not to make such assumptions. Please clarify whether the container is a standard model, has special features, or is of a specific brand.

5.      In the experimental section, it is unclear how many replicates were tested for each condition. In Figure 4, where the stress-strain curves are depicted, it is not clear whether the curves represent individual tests or the average or median results. Please clarify this in the methodology and provide precise details in the results.

6.      In the analysis and discussion of Figure 5, I noticed the error bars on the curves, but it is not specified how many replicates were performed. Please revise and provide this information.

The conclusions describe the findings, however they would be more meaningful and contribute to the body of knowledge if additional rationale were provided. Please add more detailed explanations to the conclusions, relating to the behind phenomena responsible for the enhancement.

Comments on the Quality of English Language

I consider that the English language is good.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

 

Thank you for the opportunity to get familiar with your work entitled “Effect of Deep Cryogenic Treatment on the Artificial Aging Behavior of 6082 Aluminum Alloy”. The paper is well-organized, it consists of 5 typical section: abstract, introduction, materials and experimental methods, results and discussion, conclusions. I enjoyed reading your work and below  you will find my remarks regarding individual sections, which do not dimish the value of your paper.

Introduction

Half of the introduction is devoted to aluminum alloys series 7xxx which are not the focus of this paper. In my opinion it should be shortened to the most important ones as this is not part of the study.

Line 108 - 109 – “Sonia et al. [16] conducted deep cryogenic treatment at 183 °C on 6082 aluminum alloy…” it was at negative 183°C

Lines 131 – 138 – please explain what the Authors mean by composite heat treatment repeated a couple of times in these lines only

Materials and Experimental Methods

Regarding Table 1 – according to my knowledge and accessible data in for instance matweb database the content of Cu in 6082 aluminum alloy cannot be higher than 0.1 mass % and in your case it is 0.2 mass %. Was the chemical composition analysis conducted by the Authors or was it provided by the manufacturer? Perhaps it is a different 6xxx alloy than the Authors think. It might be worth to recheck it with a spectrometer.

Line 154 – regarding the choice of times for the cryogenic treatment. I believe it is important to provide the results for the reference samples, meaning the samples subjected to the same heat treatment procedure with no cryogenic treatment. If the experiment is conducted in the way it is now the Reader will not know if the effect is positive or negative in regard to the traditional sample with no cryogenic treatment.

Figure 2 – according to the provided chart it seems that the samples were placed in the furnace at ambient temperature and heated along with the furnace up to 550°C, is that correct? The figure suggests that the samples were supersaturated directly to cryogenic temperature, and according to line 152 the samples were “quenched in water and then promptly immersed in liquid nitrogen”. It would be good to rethink the diagram to better represent the actual state of the experiment.

Was the temperature measured inside of the “dedicated liquid nitrogen container” (line 159) for the whole duration of the experiment, ergo up to 24 hours? Was the temperature constant and at exactly negative 193°C throughout the whole experiment?

Results and Discussion

Fig. 4 and 5, as I mentioned above, it would be beneficial to provide results for samples with no cryogenic treatment which would be obtained from the same sheet, to prove that there is a reason to conduct cryogenic treatment at all.

Is the 3mm sheet considered a final product? Maybe it would be beneficial to check whether it is possible to further roll the sheet after the cryogenic treatment and artificial aging. (optional)

 Conclusions

The conclusions are well-written and supported by the obtained results

References

There are 29 reference entries and only 1 is self-cited. I like the fact that the cited papers are mostly not older than 5 years. If you were to look for additional references for your future work in cryo conditions I suggest papers published in Cryogenics journal (ISSN 0011-2275) as there are many interesting and quality papers on that topic and since you did not cite any papers from that journal I think you might not be familiar with it.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf