In Situ 3D-µ-Tomography on Particle-Reinforced Light Metal Matrix Composite Materials under Creep Conditions
Round 1
Reviewer 1 Report
- The reviewer is concerned about the possible overlap with other published material. The creep damage seems to have been reported before in Ref. 39, i.e. Huppmann, M.; Camin, B.; Pyzalla, A.R.; Reimers, W. In-situ observation of creep damage evolution in Al–Al2O3 MMCs by synchrotron X-ray microtomography. IJMR 2010, 101, 372–379.
- "Cavity", "cavitation" or "void" are usually used to describe creep damage while "pore" and "porosity" are often used to describe defects in alloys produced by casting or powder metallurgy. The reviewer is not comfortable with the use of "pore" and "porosity" for creep damage.
- (Line 183-186) The authors claimed "For the Ti-MMCs however,
the growth function of the porosity is not proportional to the strain (Figure 6b), when considering the entire creep curve. When taking a closer look at the development of porosity in the early creep stage
of the Ti-MMC, a proportionality of porosity to creep strain is visible here, too (Figure 6c).". This seems to be self-contradictory. Which one is true? - The authors claimed that "the creep damage is defined by pore formation in the early stage" for the Al-MMCs in subsection 3.2.2.1. It would be more convincing if direct evidence (Fig. 15, etc.) can be provided in this section. What stages are the images in Fig. 7 referred to?
- It would be good if tomography images showing creep damage at different stages can be provided for the Ti-MMCs in the Results section, i.e. subsection 3.2.2.2.
Author Response
Dear Reviewer 1,
thank you for the review of our manuscript, all your advices and the time you spent for it.
Please see the attachment for my response.
Best regards
Bettina Camin
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper is interesting and it is recomended for publication after having solved the following points:
Line 36-39: Comment - this simplified creep description is almost correct, but unusual and picturesque for creep description. It is suggested to introduce the concept of stable steady phase (or secondary creep) where the deformation is linear (you call it “early”) and acceleration phase (non-linear) third stage (you call it “late”) where the deformation rate is continuously accelerating till rupture. This is why the “early creep-stage” some time is correlated to the very early initial stage (primary creep) where an accelerating deformation rate is recorded from zero up to the stable-deformation rate of secondary linear creep stage.
Line 42-45: please be more clear: creep is a well defined complex phenomenon that includes vacancies diffusion (Nabarro Herrings), atoms and vacancies at grain boundary (Cooble) and disclocation creep depending on temperature/time…more complex chemical reaction (such carbide complex M23C6 precipitation ..i.e.).. In MMC the “creep-detachment model” has been proposed several years ago, to describe the interface particle-matrix poor bonding… but please, re-edit or cancel the concept that creep means “porosity in metals”. The vacancies agglomerates in nanodefects that can growth in internal pores….as you explain.
Line 72: according to my knowledge, in metallurgy the word “porosity” is not commonly used for describing the creep-voids formation, you are referring. Porosity is generic word that describe, i.e. the gas-defects during primary processing or dendritic interspace defects. It is suggested to adopt “voids” or “creep-voids” instead porosity.
Line 81: T6 is a well known artificial ageing treatment, but it has several parameters that can be adjusted, as you say “overageing”, please describe the thermal treatment adopted in detail. Use the concept od ageing treatment not only T6 treatment.
Fig 3: please add a reference marker in microns, some label is of very poor quality cancel or improve.
Table 2: add rupture time column
Fig 5: The inverse creep curve that you have recorded is not commented even if it is not common and probably it is not clear why you have seen such experimental result. The paper focus is not on creep testing, but on creep damage, but such kind of curves are disorienting and many question on reliability of testing apparatus arise. Please, give here a clear and detailed explanation of the inverse creep curve (very early creep or inverse creep-strain). The figure should be improved in order to show more clear the different tests.
Author Response
Dear Reviewer 2,
thank you for the review of our manuscript, all your advices and the time you spent for it.
Please see the attachment for my response.
Best regards
Bettina Camin
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors
Dear Authors,
I have to read your manuscript with great attention and interest:
The Title: In situ 3D-μ-Tomography on Particle Reinforced MMC-Lightweight Materials under Creep Conditions
The application covers the scope of the magazine and is full original, and I have attention, so I publish it after MINOR REVISION.
Keywords:
I suggest keyword: Al-MMC, Ti-MMC, particles reinforced, creep mechanism, in-situ experiment, 3D tomography
Introduction:
34- [5-12] there are no such simplifications, please indicate the condition, which will be relevant for the Experimental chapter
Materials and methods:
89 Figure 3 improve the quality, the magnification
161 explain what the different number of tomograms made results from
Results
187 Fig.6.c put information about sample: Titan + 15% SiC?
233 Figure 8. To many data in this diagrams, there is no reason to put data in one diagram, the more so that the relationship between parameters is not visible
237 where is Fig. S2? Supplementary Materials: The following are available online at www.mdpi.com/xxx/s1, it doesn’t work
261 Figure 9. To many data in this diagrams and Fig. 10, Fig. 11.
383-400 on what basis was the crystallized and unchanged structure indicated only for microstructure tests?
Author Response
Dear Reviewer 3,
thank you for the review of our manuscript, all your advices and the time you spent for it.
Please see the attachment for my response.
Best regards
Bettina Camin
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The Reviewer is satisfied with the changes made.
Reviewer 2 Report
It is a pleasure for me recommend the paper for publication.
