In Situ CT Tensile Testing of an Additively Manufactured and Heat-Treated Metastable ß-Titanium Alloy (Ti-5Al-5Mo-5V-3Cr)

Round 1

Reviewer 1 Report

In this paper, the in-situ CT tensile testing was carried out, and the failure-critical defects were detected, analyzed and monitored. The defect growth behavior was analyzed from various angles, which was very interesting. However, the manuscript was not well organized and the logic was not clear. There are several small problems :

1. The language should be improved, many careless mistakes exist in the manuscript. For example, Line 14 in the abstract "were" should be "where", Line 26, there should have a comma after the phrase "Regarding their fracture mechanisms", line 52, typo of “Ti-5Al-5-Mo-5V-3Cr”.
2. Combined with the a & b figure, it was found that the solution temperature at this time is closer to the phase transition point, and perhaps the performance will be better if the solution temperature is lower.
3. In line 322, the main influence of the theory on mechanical properties is the fraction of two Ti phases found in Ti-5553, but the volume fraction is not studied in this paper.
4. In line 336, it showed that each sample had defects, and the influence of the mentioned curve previously was nice, but the influence of defects cannot be guaranteed to be consistent on each sample. How to analyze the relationship between performance and microstructure on the same basis is a question.
5. There were only two experimental samples in this study, but the difference between the two samples was quite large. In the later mechanism analysis, how to determine the impact of the previous treatment or the impact of the latter treatment deserves careful consideration. 

 

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Reviewer 2 Report

"By applying a BASCA heat  219  treatment, the mechanical strength is almost unaffected, but the elongation at break rises" But, their elongation doesn't change.

It is better to give the expansion of defects in FIgs.9 and 10. Those defects are all of the defects or just some of them? Or the whole view is given as the size of Fig.9? what is the window size of x ray?

Please mark z direction in Fig.12 and what is the z expansion refered in Fig.11?
Please discribe the defects in Fig. 12 are exposed to surface or totally inside the specimen.
The stress-strain curves for in-situ CT tension should be given.

“It can be assumed, that the  257  solution step does not dissolved the as built microstructure completely and a fraction of  258  the original αS  remains as part of the microstructure”. it should be αp?

In page 2, line 59, bbc should be bcc.

What is the difference between Fig.2b and 2d?

The specimens for conventional and in-situ test are from the same batch of EB-PBF manufacturing?

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Reviewer 3 Report

This manuscript mainly presents an analysis of the mechanical properties of Ti-5Al-5Mo-5V-3Cr (Ti-5553) manufactured by EB-PBF after different heat treatments. As Ti-5553 shows great potential to be used for in small, highly complex and load-bearing parts, research on its material properties also has been a hot spot in recent years.

The content of this paper is within the scope of Energies. However, there are some issues should be addressed. Generally, my opinion is this manuscript can be considered for publication in Energies after a Major revision.

Some more detailed comments and suggestions are as follows:

1. The current “Introduction” section of this paper is not good enough. Even though the authors have done strong background of their research, they still failed to clearly indicate the scientific gap their current work filled in comparing with the previous (work). Therefore, the significance and motivation of this paper seems not clear. The authors should add more details here. Moreover, the literature review in the “Introduction” is not adequate enough. The authors didn’t refer to the most recent and appropriate work. Some more last work on the topic of microstructure, texture and mechanical properties of Ti-5553 should be cited. E.g. “In-situ measurement of α formation kinetics in a metastable β Ti-5553 alloy using laser ultrasonics. Journal of Alloys and Compounds, 2021, 866. "
2. The authors should further check and polish the language of this manuscript to correct some grammatical mistakes and typos.
3. In “Industrial Computer Tomography” it should focus on the innovation proposed by the authors when using this method, such as the optimization strategy mentioned in lines 330 to 334, rather than the basic background introduction.
4. There should be clearer annotations in Figure 2 to illustrate.
5. Engineering drawings like Figure 4 and Figure 6 can be more clear.
6. In Fig6, if there are threads on both ends of the test specimens, the circle with the second largest diameter in the side view should be represented by a three-quarter circle with a thin solid line.
7. Can the stress/strain graph mentioned in line 246 can be add to this paper and explained in combination with Fig10?
8. Is the value of Fig12 (d) written correctly?
9. The “Conclusions” section should be illustrated by several key points for description. Meanwhile, pay attention to the difference between the “Conclusions” and the “Discussion”. It is recommended to sort out the “Conclusions” and “Discussion” and restate them.

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Reviewer 4 Report

In this research, authors have conducted a groundwork for in-situ tensile test and defect tracking to further investigate the effect of defects in additive manufactured parts. Here, the industrial µ-CT, equipped with the Deben CT5000, was used to investigate the changes of defects in the tensile testing, and also the mechanical properties were compared with the conventional testing method. Authors have done the interesting tests and found some meaningful conclusions. Here, I have some problems.

1. Figure 12. Please ensure that the comparison was conducted with the same position of specimen. There are some red zones around the red defect in Figure 12b. But it cannot be found in another pictures.
2. Please give some description for the accurate extraction of defect in specimen. The overlap of threshold between air and material may happen for the material at the boundary of specimen and inner air in the sample.
3. For the conclusion, can you give them point by point for the better understanding?

 

 

 

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Reviewer 5 Report

I have reviewed the article entitled, "In-situ CT tensile testing of an additive manufactured......" and how found that it needs significant improvement, both in the writing and the scientific experiments.

The paper needs significant copy editing. There are misspelled words, sentence fragments, missing comma's, in incorrect verb usage. Figure scale bars need to be improved. Additionally, first usage of acronyms must be spelled out. I have attached a print out of my written comments, but these are not all of the copy editing issues. I don't know the journal preference, but 'in situ' should not have a hyphen nor should 'situ' be capitalized according to the ACS style guide.

On page 14, the authors discuss how the results of the in situ experiment is different from the conventional tests. It would be a great place to explain why and show experimentally. For example, the authors can put the flat in situ samples into the conventional testing rig and show how the geometry behaves. And, they should take a CT of the conventional testing rig specimen before and after testing (ex situ). Electron microscopic images of the surfaces would have also helped to see the differences between the specimens.

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Round 2

Reviewer 2 Report

The illustration of Fig2. is not clear. Their histograms should
be the same, only different  critical values are selected, then
the resulta fig2a and 2c are different. So, this logic should 
be clearified. The axises of histagram should be given. And 
what is the meaning of the gradally changing of background 
color?

In Fig.9 the STAcon. sample is of cavity inside (seen from the fracture surface), so maybe its elongation is also high.
The elongation is sensitive with cavities or pores. For small section, there is big effect of pores, so the elongation is poor. It is better to give discussions about it.
Maybe the elongation of the conventional one is correct. For STAcon. maybe more samples can prove its high elongation.
Still some mistakes of spelling or gramma.

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Reviewer 3 Report

My opinion is this manuscript can be considered to accept in present form.

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