Relation between Mechanical Milling Parameters in Phase Transformation and Oxygen Content in Ti–Nb–Mo Powders for Posterior Sintering

Round 1

Reviewer 1 Report

(1) XRD can only be qualitatively analyzed, but Table 1 gives very accurate data. Moreover, XRD is difficult to detect low content substances.

(2) How is the microhardness of powder detected? Need to tell the detailed method.

(3) Powder ball milling has high strain and stress after 40h and 60h. How can it be directly formed under the pressure of 1000MPa, considering the elastic after-effect?

(4) In Figure 3, it is directly marked which are alpha titanium and which are beta niobium, lack of evidence.

(5) How to measure the oxygen content after sintering? The sampling method has an effect on the oxygen content, and the process needs to be given.

Author Response

Dear reviewer, thank you very much for all suggestions and corrections. The comments can be found in the file submit.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is too long. I would suggest to divide it into 2 parts: the effect of milling time to phase transformation and the second: suitability of medium milling time to manufacturing beta-Ti items for orthopedic application. The second part of manuscript on effects of sintering is less interesting, presented in a more chaotic way. There is only 1 conclusion from this part apart from a large number of characterization results.

There are several mistakes, errors etc. in the present form of manuscript. Examples: vers 129-141 are repeated in section 3.1. No descriptions of some characterization methods: size of samples for mechanical testing, specific surface area measurement, grain size measurement, pore size distribution. No units for particle size (v.367). Caption of Fig.5 should be completed with milling time. table 3: lack of units for particle size. For better presentation of milling results I would suggest to add XRD results of the mixed batch before milling to fig.1. There are 2 controvercial sentences: v.183 and v.201. Caption of Fig.2- "sintering" is not correct in this place. 

Additionally: I cannot agree with sentence v.277-288 that powders milled for 40 h in the continous mode contained 9% (wt%???) more oxygen in comparizon to powder milled for 40 h because the results are within experimental error. If you compare oxygen content in all specimen with their errorrs the you culd see that only a sligh increase oxygen contant occurred with increasing milling time. At the same time I cannot agree with conclusion No 4.

I am not sure if your powders could be called as nanopowders, since their particle size after milling is in the micrometer range. They are rather highly defective in nanoscale. Discussion on sintering requires deeper analysis of this process.

Author Response

Dear reviewer, thank you very much for all suggestions and corrections. The comments can be found in the file submit.

Author Response File: Author Response.pdf

Reviewer 3 Report

In this manuscript, the authors describe the relationship between mechanical milling of TiNbMo powders and the resulting changes in microstructure. This is an interesting sample system that is used e.g. in medicine. Several methods, mainly XRD, are used to characterize the samples.

Unfortunately, some of the conclusions are not comprehensible. Therefore, I cannot recommend the publication of the manuscript.

For example, the analysis of the XRD data is based on the method of Williamson and Hall. However, a linear course of the reflex widths, as would be expected from this method, cannot be seen in most of the data sets (see e.g. Fig2 b, c, d e, Fig. 8 a b.). The quantities derived from these figures have too large errors, which unfortunately is not indicated by the authors.

When analyzing reflex widths, the contribution of the diffractometer must also be given in any case. Especially using a commercial diffractometer often the instrumental resolution dominates, which leads to wrong crystallite sizes. The resolution can be determined for example with a known sample (e.g. LaB6).

In such an analysis, the diffractograms of the feedstock powders should also always be taken into account.

Errors for mass fractions should be reported for the Rietveld analysis.

Which parameters were varied in the analysis?

The ICSD files used in the analysis of the data should be cited.

Maud also supports peak width analysis, why was this method not chosen?

Why is there no Nb reflection seen in the XRD data?

No errors are also reported in the determination of particle sizes.

Another key issue is the determination of hardness. Within the error bars, the samples do not seem to differ significantly.

The presentation in Figure 9 is not optimal.

In Figure 12 there are no axis labels.

The values in Figure 14 do not seem to differ significantly.

Author Response

Dear reviewer, all the authors are grateful for all the comments and suggestions that improve significantly the quality of this manuscript. All the responses can be found in the file submitted.

Author Response File: Author Response.pdf

Reviewer 4 Report

The paper presents a work on Relation between mechanical milling parameters in phase transformation and interstitial oxygen content in Ti-Nb-Mo powders for posterior sintering. The manuscript must be amended in order to be considered for publication. Many sentences must be revised to make sense and many results must be clarified. Attached is the file with the notes that should be changed.

Comments for author File: Comments.pdf

Author Response

Dear reviewer, thank you very much for your contribution to this manuscript. All the authors are grateful. The responses for the comments can be found in the file submitted.

Author Response File: Author Response.pdf

Reviewer 5 Report

This paper studied mechanical milling parameters in phase transformation and interstitial oxygen content in Ti-Nb-Mo powders for posterior sintering and can be rejected for publication because the following many flaws in this paper:

1. Introduction didn’t talk about open vessel ball milling. Author need to explain how open vessel ball milling carried with reference papers.

2. Why the mass percentage is chosen as 35Nb (wt%) and 6Mo (wt%) ?

3. 2.4 Mechanical characterization second paragraph and 3.1 XRD and crystallographic analyses first paragraph repeated. Author need check before submission to the journal.

4. Ball milling done open vessel for 12 hours. But XRD results show no oxides formation. Can author explain the reason why there is no oxide formed?   

5. Author should clarify which one is the α phase and which one is the β phase because there is more confusion to find out. As per Figure 1, the following sentence is not correct “the α peaks related to planes {110}, {112}, and {201} were absent”.

6. Study of table 2 and figure 2 is not mentioned. As data from table, size got reduced but explanation was not correlated properly.

7. How the author defines the α and β phases in the microstructure (Fig. 3)?

8. Which hour of ball milled samples Elemental mapping done (Figure 5)? Mo wt% is considered only lower. But EDS image seems its is spread all over and it seems edited. Author need to provide elemental composition percentage of EDS image.

9. The whole paragraph from lines 129 to 141 should be removed because it has appeared in the Results and discussion.

10. From line 185 explanation related to crystallite size was confusing. Please make it clear.

11. XRD studies, SEM studies provide no oxide formation but line no. 276 to 282 and table 4 showed increase in oxygen content. Why?

12. Author says no significant increase in microhardness during 40h milling. But figure says value got increased from 421 HV to 425HV.

13. Line 309 what is Nthe? Explanation related to Table 5 is not satisfactory. As per that table it is not twice, author need to check and rewrite.

14. Fig. 10 with one SEM image, author explained EDS results of three different ball milling hours. There is no evidence of author saying presence of Nanopore.

15. Fig. 14 title and unit in figure didn’t match. Values are inappropriate

16. How could the author differ both niobium (Nb) and molybdenum (Mo) from the other non-toxic materials for the synthesis of Ti alloys?  

17. What is the relationship between the dislocation density and microstrain?

18. What is the reason for the Particle size difference at different milling times?

19. Pores (indicated by arrows) were significantly present in our samples in which figure? And how the % of pores were calculated?

20. Normally, for metallic materials, the microhardness has a linear relationship with strength. Why does the microhardness decrease but the bending strength increase?

21. The figure numbers and the texts were wrong in some places.

Author Response

Dear reviewer, thank you very much for your contribution to this manuscript. All the authors are grateful. The responses for the comments can be found in the file submitted.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Are you sure the  pressure is 1000MPa？After the powders were ball-milled, the lattice distortion and work hardening are relatively obvious, and the elastic after-effect of pressing at 1000MPa will be very large, and it is difficult to press successfully. 

“Then they were compacted at 1,000MPa in cold-pressing universal testing Shi- 100 madzu Autograph AG-X plus equipment, with a maximal load of 100 kN machine”.   

Author Response

Dear reviewer, thank you very much for your observation and contribution for improve this work.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is somehow improved but I reccommend rejection.

Comments for author File: Comments.pdf

Author Response

Dear reviewer,

Thank you very much for making time to review this work. All authors appreciate your feeedbacks and comments.

Sincerely,
Mariana Rossi, PhD

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have significantly revised their manuscript, raising the quality. However, there are still some points that need to be clarified (see below). I would like to apologize for the fact that there are still so many comments and partly new comments that were not mentioned in the first draft. This is due to the structure of the first version, which made it difficult to write a comprehensive report.

-The authors say that the instrumental resolution was disregarded in the analysis (line 115). However, in the response to the first report they show a reference spectrum. So it seems that they included the instrumental resolution. If not, they should briefly comment that this tends to lead to an underestimation of the crystallite sizes.

-  (line 114) The microstrain and crystallite size values was also quantify and before, the instrumental width was disregarded.

…were also quantified….  What does ‘before’ mean?

- In figure 1 b the authors should include the MAUD fits

-In line 157 the authors mention the 110, 112 and 201 reflections, however the 110 and 112 reflections are not indicated in figure 1b.

-In figure 1b the alpha 100 reflection appears two times, this is not possible

-The authors argue that the absence of the 110, 112 and 201 reflections indicate the transformation alpha to beta. However, they still see the alpha 101 peak. Thus, they should mention in line 157 that the transformation is incomplete.

-In figure 1b the authors should shift the times on the corresponding dataline.

-The authors should give a definition of Rwp and Rexp

-In table 1 12 h alpha Ti please correct 34.=9….

-When comparing crystallite sizes in table 2 it would be useful to include also the size/strain of the feedstock powders (xrd pattern in fig 1a).

-In table 2 the authors give the crystallite size in nm. However, the standard output in MAUD is given in Angströms. From the enormous peak width, I would also speculate that the values are given in Angströms and not in nm.

-In table 2 the strain is given in % so the values are in the order of 0.00005. Is this correct? I do not see that the MAUD output is given in %.

-In section 3.3 the authors should give a definition of the different d(x.x) values. In table 3 the values of the 60 h measurement have no errors.

- Line 294 ‘It was clear that when contamination was not significant when opening the vessels.’ What does the sentence mean?

-‘It was clear that microhardness increased with a longer milling time.’

It is clear… ?

- In section 3.7 the authors say ‘From the XRD profile, the intensity of the α-Ti- 327

002, 101 and 102 peaks decreased’   In what relation do the intensities decrease?

Furthermore, the authors say that the 112 reflection is absent. However, this reflection is still visible in the figure.

-‘In the sintered samples obtained after 60 h of milling, the content in the α phase was basically twice that of the others, which corresponds to higher oxygen content during MA process contamination.’

I do not see the factor of 2 and where is the connection between the alpha phase fraction and the oxygen content?

-Table 6: Please check again if the values are given in nm and %.

-‘The relation between grain size and milling time during the heat treatment of the microcrystalline powders for the samples sintered at 1,300ºC before being milled at 40 h, 60 h and 40 h in the continuous mode was clear.’

It is unclear what do the authors mean.

-In Line 387 the authors should add a citation for the oxygen effect on the alpha phase.

-In Figure 10, one should label x and y axis and add a legend. As an alternative Figure 10 and discussion can be removed because no difference was found.

-In line 428: Figure 11b should be Figure 9b

-The discussion of Figure 11 is difficult to follow. One should show only the pole figures which show a clear difference and from which one draws conclusions.

-In Line 471 the sentence ‘The microhardness values of the sintered samples made with powders milled for 40 h, 60 h, and 40 h direct were measured and presented a minimum and maximum value of 154.7 and 170.2 HV’ should be reformulated. Maybe exchange ‘presented’ by ‘show’.

Author Response

Dear reviewer, all the authors are grateful for all corrections, contributions and suggestions for improve this work.

Author Response File: Author Response.pdf

Reviewer 4 Report

The paper can be accepted 

Author Response

Dear reviewer, some modifications has been made in order to improve the quality of the paper. All changes are highlighted. Thank you so much for contribution to improve the quality of the work.

Round 3

Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

All comments have been addressed. The new informations inserted in the manuscript are highlighted. Once again, all authors are grateful for the careful and insightful review of manuscript that improved its quality.

Sincerely yours,

Mariana Rossi, PhD

Author Response File: Author Response.pdf

Reviewer 3 Report

The authors have edited the noted points accordingly. I have no more comments so far. However, I recommend having the manuscript revised by a native speaker. I do not need a resubmission.

Author Response

Dear reviewer,

all authors are grateful for your careful reading of the manuscript and their constructive remarks. the manuscript has been edited by a native english speaker. The invoice related to this revision can be found attached.

Sincerely,

Mariana Rossi

Author Response File: Author Response.pdf