Formation and Thermal Stability of the ω-Phase in Ti–Nb and Ti–Mo Alloys Subjected to HPT

Round 1

Reviewer 1 Report

• There are many articles of titanium alloys with good mechanical properties. The following references are recommended. [1] Preliminary Tests for Ti-Mo-Zr-Ta Alloys as Potential Biomaterials; [2] In-depth assessment of new Ti-based biocompatible materials; [3] Mechanical tests for Ti-based alloys as new medical materials.
• Show the novelty of the paper compared to the literature, however there is still much work on this topic.
• Show the novelty of the paper compared to the literature, however there is still much work on this topic.
• Why you choose these alloys?
• Add a table of EDS test for alloys.
• In the Introduction section, the last paragraph should contain the scientific contribution and scientific hypotheses of your research. Complete, further elaborate the scientific contribution and scientific hypotheses of your research. Be explicit. In addition to the goal of the research (which was written), the novelty in the context of the scientific contribution should be pointed out. Scientific contributions should be written based on the shortcomings of previous research in the literature. In this way, the authors will better emphasize novelty and scientific soundness.
• The "2. Materials and Methods" section should not only list materials and methods. Every choice should be explained. Complete this section in detail.
• Analyze and discuss possibilities of practical application.
• Complete the conclusions with the limitations of the proposed methodology. Also write future research.
• Generally, the quality of the writing could be improved.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

In this manuscript, four different alloys were produced and deformed through the HPT process. Phase transformation during the plastic deformation and following heat treatment was studied. The paper is well-structured and experiments are described precisely. A huge amount of data is reported; however, the discussion on data in some parts is short and shallow. Overall, the paper brings sufficient novelty for publication, however, the following shortcoming should be resolved:

 

Comments:

1. A short review of previous research working on the effects of studied parameters on the phase transformation needs to be included in the Introduction section.
2. Font size has changed repeatedly in the Material and methods section.
3. How is it that, the peaks related to the β phase before HPT are marked as both α and ω phases after HPT?
4. Please use the same template for the figure captions. Figure 4
5. A simple calculation shows that the results presented in table 1 do not match. Please check the results again.
6. Please explain which method was used for the calculation of phase composition.
7. In three different parts of the manuscript, the authors claimed that: "Since it is easier to deform a two-phase or single-phase structure with a fine grain size than a single-phase coarse-grained structure". What does easier mean? Please clarify. In addition, it was revealed that lower grain size increases the resistance to the martensitic transformation. How you can support your conclusion?

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The paper is describing the effect of Severe plastic deformation using HPT in two different Ti alloys and discusses the features of the ω-phase formation. The paper has some interesting results but there are some problems that need to be addressed as follows:

1) In the Material and methods section: How many passes of HPT used for processing the Ti alloy. More details are needed to make it clear for the reader.

2) In the results and discussion there are some problems:

a) ‘The grain size varies from 0.5 to 1.5 mm.’ I think the authors mean µm not mm. another thing how authors evaluated the range grain size if the grain shape is elongated. The range of grains is representing the length or width or what, that needs to be clear.

b) There is no description of the SAED in Fig. 2 in the context.

c) Fig. 3 description is repeated in the context.

d) I am confused in line 153, It was mentioned HPT was performed at RT then what makes transformation to ω phase? I believe there is a paper mentioned later that describe the reason or mechanism of the transformation, but it needs to be clear here first as its confusing to the reader.

e) line 159 its mentioned that there was a grain refinement after HPT. Where is the prove? I cannot see any grain boundaries. Only some dislocation cells.

f) Fig. 4 how alfa and beta were identified.

g) Line 182 there is a false conclusion. TEM samples are too small and HRTEM image is from a very small area to conclude the absence of the beta phase grains. Later assumption based in this conclusion would be also wrong. Related corrections or more prove of the absence of the phase grains is essential.

h) line 379, what does inhomogeneous microstructure mean ?? need to clarify as this word is confusing to the reader.

i) line 381, fig. 13 d is diffraction why included in the dislocation density description?

Author Response

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Reviewer 4 Report

The authors observed that  the thermal stability of the ω- 24
phase in Ti–Nb and Ti-Mo alloys increases with increasing the concentration of Nb or Mo.  The article is interesting. The following points need to be addressed carefully.

1. Authors need to clarify the novelty of the work.
2. How the influence of microstructure morphology has been performed?
3. Add the measuring instrument figure in section 2.
4.  More explanation is needed in fig. 2, c,d,e
5.  What is the need for XRD analysis?
6. Authors mentioned that ' It is also possible that the ω- 455
   phase with a high content of the alloying element will contain more defects in the crystal structure caused by SPD' How it is valid?
7. Synchrotron XRD curves of the Ti–3wt.% Nb needs more explanation.
8. How the grain size of the microstructure also affects the phase transformation?

 

 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The presented data are original and interesting. The manuscript has been significantly improved and is suitable for publication in the present Journal. 

Reviewer 2 Report

The authors have provided convincing explanations in the revised version. In my opinion, the current version of the paper can be considered for publication.

Reviewer 4 Report

The article is now accepted and recommended for publication.