Generation of a Strength Gradient in Al-Cu-Ca Alloy Foam via Graded Aging Treatment
Round 1
Reviewer 1 Report
The manuscript studies effect of gradient heat treatment on compressive property of Al-Cu-Ca foam. The manuscript needs to address the following comments before it can be accepted for publication.
- What is the cell size and strut thickness. The macrostructure image of foam shown in Figure 1 is not high quality to show this. Need a better quality image.
- Figure 2 is impossible to read the EDS readings with the image background. Better to include it as a separate table.
- Studies on gradient foams have used DIC to show the variation in foam deformation across the foam thickness. Figure 3 as such its difficult to observe the variation in deformation across the thickness. DIC could help in showing the variation in strain levels across the foam thickness.
- Energy absorption is an important design parameter for metal foams. It would be better to compare the energy absorption until densification strain for the gradient and untreated foams.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is a very short communication type article with some preliminary results. My comments are as follows:
FIg.1 has a low quality, please improve its resolution.
Line 97, ‘undergoed’ should be ‘underwent’.
It’s better to show some quantified results of amount of Al2Cu precipitates in Fig a-c.
Line 106, redundant ‘aging sample 1’
The temperature gradient should have generated different residual stresses within the foams, which will have effects on mechanical properties, especially stress-strain curves. However, this has not been studied. I suggest either add experiments for residual stress measurement, or mention this as a future work and add some relevant studies, e.g. Materials Science and Engineering: A 622 (2015) 82-90.
Line 125-127, I believe the orientation should be ‘strength gradually increases from top to bottom, not the other way round.
It is not obvious from Fig. 3 that ‘collapse of cellular structure initiated and accumulated in the top portion of the sample until the deformation of 50%’, actually I cannot see that the top first collapses.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The paper has an original and novel idea about the processing of advanced Al-based alloys that match with the Journal's scope. The novelty of the subject is adequate for the submission as a "Communication" contribution. However, there are some points that it is important to be checked:
- The English grammar and Writing style are good enough. There are just some minor words that should be revised and are indicated in the annotated manuscript attached.
- Fig 1a: I consider a high magnified image of the porous is very important, once it could provide details about their shape, size, and distribution.
- EDS elemental mapping could also provide more interesting results about the distribution of the alloying elements along with the phases.
- As a "communication" contribution, it is plausible that the study provides a novel idea with some accurate results. From the results of Figs 2 and 3, it is not clear the changes in the samples after the aging treatments. Perhaps, it could be a result of the aging parameters chosen (temperature and time), which did not produce noticeable microstructural modifications. The authors must check this issue.
- Advanced characterization techniques (such as FE-SEM and TEM) are required to evaluate the real changes in the phase proportion and morphology in the samples. They will be very important to support the original idea about the strength gradient.
Having all of this into account, I believe that the paper needs a major revision for acceptance.
Comments for author File: Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have addressed most of the reviewer comments, but manuscript still needs a minor revision.
- The image in Figure 1a of revised manuscript, seems to be the same as the original version of the manuscript. Better to include a higher magnification image.
- If DIC is not utilized, atleast use other programs for strain mapping such as Matlab to identify area undergoing large deformation with the existing set of images.
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
I have no further comments on the research contents, but some spell check still needs to be done, such as 'after underwent (should use 'undergoing' here) low temperature ageing', 'which will study (should use ' will be stuided' here) etc. Please also try to improve the figure quality.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The revised paper exhibited corrections for all points indicated earlier. The cover letter also clarified the main issues pointed by the last revision process.
Regarding the EDS results, I recommend the authors evaluate if it could be plausible to insert them as a supplementary material.
I consider the paper suitable for publishing in the Journal.
Author Response
Thank you for recognising our work. Regarding to the EDS results, the Al-Cu-Ca alloy changes composition with aging temperature, so the results have been added as a supplement to illustrate the effect of aging on precipitates. This is why the addition of this result is necessary.
