Achieving High Self-Lubricating Performance of Al-Bi-Sm-Ti Alloys Based on the Intermetallic Compounds

Round 1

Reviewer 1 Report

24. Immiscible alloys, just application is shortly discussed, should be discussed in detail possible with graph/charts etc

63. Why do you prefer an Ar atmosphere over a vacuum atmosphere in an induction furnace?

103. Based on the discussion, BiSm intermetallic compounds obtained the best Wetablity test; the author should add results/graphs/charts/images for the wettability test.

109. Unfirm distribution is discussed and does not show uniformity; authors should use high-resolution/magnification images to justify uniformity at 30 microns, which is not justifiable.

113. EDS, from range 0 to 2 KeV, has various peaks with apparent intensity; what are those peaks? They do not satisfying the uniformity of intermetallic and should be addressed in detail

 

 

English can be improved depending upon editor detailed review

Author Response

Dear editor:
    I am very grateful to your comments for the manuscript. According with your advice, we amended the relevant part in the manuscript. Below are answers to the points raised. Changes are highlighted in red in the manuscript. 

24. Immiscible alloys, just application is shortly discussed, should be discussed in detail possible with graph/charts etc.

Thank you for your advice. We have amended and highlighted in red in the manuscript. 

63. Why do you prefer an Ar atmosphere over a vacuum atmosphere in an induction furnace?

Thank you for your advice. The Ar atmosphere was used to protect the alloys from oxidization. The Bi phase has a low melting point. Meanwhile, the Ar atmosphere would restrain the evaporation of the Bi phase.

103. Based on the discussion, BiSm intermetallic compounds obtained the best Wetablity test; the author should add results/graphs/charts/images for the wettability test.

Thank you for your advice. The wettability test of BiSm intermetallic compounds was difficulty due to the in-situ formed. As shown in the Fig.1d, The BiSm intermetallic compounds are located inside the Bi-rich droplets due to their best wettability with the Bi-rich droplets.

109. Unfirm distribution is discussed and does not show uniformity; authors should use high-resolution/magnification images to justify uniformity at 30 microns, which is not justifiable.

Thank you for your advice. The microstructure of Al-Bi-1Sm-2Ti alloy was shown in Fig.1b. The white droplets are the Bi-rich phase. From the figure, the Al-Bi-1Sm-2Ti alloy shows a much finer dispersion of the Bi-rich droplets compared with the Al–Bi alloys.

113. EDS, from range 0 to 2 KeV, has various peaks with apparent intensity; what are those peaks? They do not satisfying the uniformity of intermetallic and should be addressed in detail.

Thank you for your advice. The EDS analyses indicates that the rod-like intermetallic compounds consist of Al、Bi and Sm element. However, the content of Al was low. Analyze the content of element, the intermetallic compounds were intended to be BiSm phase.

 

 

Reviewer 2 Report

The current paper reports the study on high self-lubricating performance of Al-Bi-Sm-Ti alloys based on the intermetallic compounds. The literature review section is very poor without the critical analysis of the available results in literature. The experimental section also lacks the details which hinder complete evaluation of the manuscript. The results and discussion are not scientifically convincing. Co-efficient of fiction of about 0.20 is not considered as ‘high self-lubricating’ as claimed by the authors. Based on these shortcomings, I suggest to reject the manuscript. If the authors can improve the quality of the manuscript substantially, then they are encouraged to re-submit it as a new submission.

The other comments are as follows:

1.     Moderate language correction is necessary. For example, ‘as excellent candidates for self-lubricating wear materials’ does not make any sense. It will be ‘wear resistance material’ and so on in the rest of the manuscript.

2.     Line 14: Does not make any sense/hard to understand.

3.     The introduction section needs a good overhaul. Currently it is too descriptive in nature without any critical analysis of the results and discussion on co-efficient of friction and wear of such alloys based on the information available in literature. As the authors have focused on the eutectic composition of the alloys, it is recommended to include the portion of a phase diagram and indicate which composition in the phase diagraph the authors are exploring here.

4.     What is the novelty/justification of the current work?

5.     The experimental section lacks details of the alloy preparation. For example, ‘proper amount of Bi was added into the melt’—this is not the way to write a scientific manuscript. The major aim of the experimental procedure is that, someone else will be able to replicate the results by following the description provided by the authors. In the form, none of the crucial information on that was included in the experimental section. Same for the XRD and wear test details. No details were provided. The authors are suggested to read the manuscript published by other researchers and then modify their way of writing accordingly.

6.      The SEM images are poor quality and it was not possible to deduce anything from those SEM images except imagination! I do not see any microstructure in those SEM images. These needs to be rectified before the paper can be accessed, as results of the result and discussion  will be based on that.

7.     Authors are encouraged to include elemental mapping of the specimens.

8.     Please remove non-English content from Fig. 2.

9.     It is important to include the SEM/optical micrographs of the residual imprints.

10.  It was NOT possible to evaluate the rest of the manuscript (friction and wear section) as not enough experimental information was provided. For example, what was the counterbody used? Different types of counterbody will show different types of friction evaluation.

11.  On what basis the authors are claiming the alloys as ‘high self-lubricating’? The lowest values of coefficient of friction was repore4tde as 0.20-0.21. I don’t think this can be consider as high self-lubrication.

12.  Details of the wear rate calculation procedure is required.

13.  Evolution of coefficient of friction with time must be included.

14.   Better analysis of the wear tracks are mandatory after the wear tests.

 Moderate editing of English language required

Author Response

Dear editor:
    I am very grateful to your comments for the manuscript. According with your advice, we amended the relevant part in the manuscript. Below are answers to the points raised. Changes are highlighted in red in the manuscript. 

1. Moderate language correction is necessary. For example, ‘as excellent candidates for self-lubricating wear materials’ does not make any sense. It will be ‘wear resistance material’ and so on in the rest of the manuscript.

Thank you for your advice. We have amended and highlighted in red in the manuscript.  

2. Line 14: Does not make any sense/hard to understand.

Thank you for your advice. We have amended and highlighted in red in the manuscript.

3. The introduction section needs a good overhaul. Currently it is too descriptive in nature without any critical analysis of the results and discussion on co-efficient of friction and wear of such alloys based on the information available in literature. As the authors have focused on the eutectic composition of the alloys, it is recommended to include the portion of a phase diagram and indicate which composition in the phase diagraph the authors are exploring here.

 

Thank you for your advice. We have amended and highlighted in red in the manuscript.

4. What is the novelty/justification of the current work?

Thank you for your advice. In this work, the solidification behavior and properties of Al-Bi-Sm-Ti immiscible alloy were investigated for the first time. The intermetallic compounds formed during solidification and improved the wear properties. The solidification process of Al-Bi-Sm-Ti immiscible alloy was numerically simulated to discuss in detail.

 

5. The experimental section lacks details of the alloy preparation. For example, ‘proper amount of Bi was added into the melt’—this is not the way to write a scientific manuscript. The major aim of the experimental procedure is that, someone else will be able to replicate the results by following the description provided by the authors. In the form, none of the crucial information on that was included in the experimental section. Same for the XRD and wear test details. No details were provided. The authors are suggested to read the manuscript published by other researchers and then modify their way of writing accordingly.

Thank you for your advice. We have amended and highlighted in red in the manuscript.

6. The SEM images are poor quality and it was not possible to deduce anything from those SEM images except imagination! I do not see any microstructure in those SEM images. These needs to be rectified before the paper can be accessed, as results of the result and discussion  will be based on that.

 

Thank you for your advice. The SEM images are poor quality because of the contrast of different atom. It can’t appear cleanly at the same time. We have added the EDX analyses of Bi-rich droplets in the manuscript. From the Fig.2b, it shows cleanly the BiSm intermetallic compounds in the Bi-rich droplets.

7. Authors are encouraged to include elemental mapping of the specimens.

Thank you for your advice. We have amended in the manuscript.

8. Please remove non-English content from Fig. 2.

Thank you for your advice. We have amended in the manuscript. 

9. It is important to include the SEM/optical micrographs of the residual imprints.

Thank you for your advice. We will replenish the SEM of residual imprints in the next work. 

10. It was NOT possible to evaluate the rest of the manuscript (friction and wear section) as not enough experimental information was provided. For example, what was the counterbody used? Different types of counterbody will show different types of friction evaluation.

 

Thank you for your advice. The counterbody were 45 steel. The different types of counterbody will lead to different types of friction evaluation. We will carry this work in follow-up study.

11. On what basis the authors are claiming the alloys as ‘high self-lubricating’? The lowest values of coefficient of friction was repore4tde as 0.20-0.21. I don’t think this can be consider as high self-lubrication.

 

Thank you for your advice. We have compared with other literatures. We also have compared with our preliminary work. The coefficient of friction of Al-Bi immiscible alloys achieved 0.2 to exhibit the excellent self-lubricating materials.

 

12. Details of the wear rate calculation procedure is required.

 

Thank you for your advice. The equation of wear rate has listed in the manuscript.

13. Evolution of coefficient of friction with time must be included.

 

Thank you for your advice. The variations in the coefficients of friction with time were tested in Fig. 4. The sliding distance in abscissa were calculated by time.

14. Better analysis of the wear tracks are mandatory after the wear tests.

Thank you for your advice. We have amended in the manuscript. 

 

Reviewer 3 Report

1) Segregaed microstructure; analysis.

2) Marangoni effect; influence on the structure.

3) Why the COF increases up to 100m200m distance?

4) The difference between adhesive and abrasive wear is not clear.

5) Why the Bi area moves to wear surface?

Author Response

Dear editor:
    I am very grateful to your comments for the manuscript. According with your advice, we amended the relevant part in the manuscript. Below are answers to the points raised. Changes are highlighted in red in the manuscript. 

（1） Segregaed microstructure; analysis.

Thank you for your advice. The Bi-rich droplets of Al-Bi immiscible alloys were large and unevenly distributed. The size of the Bi-rich droplets gradually increases from top to bottom, which is a typical microstructure of immiscible alloys. A majority of the large Bi-rich droplets appear mainly at the bottom of the ingot because of gravitational sedimentation, which indicates the occurrence of liquid–liquid phase separation prior to the solidification. Large Bi-rich droplets tend to coalesce and segregate, leading to phase separation.

2) Marangoni effect; influence on the structure.

Thank you for your advice. The segregation should be attributed to the different types of fluid flow, such as Marangoni convection induced by the interface tension. The droplets collide with each other and combine, forming a new droplet through the process of the Marangoni convection. The segregation is formed owing to the collisions and coagulations between droplets.

3) Why the COF increases up to 100m200m distance?

Thank you for your advice. The soft self-lubricating film will be worn during wear process lead to increase the coefficient of friction. But the coefficient of friction of the Al-Bi-1Sm-2Ti alloy is almost unchanged due to the BiSm and Al₃Ti intermetallic compounds.

4) The difference between adhesive and abrasive wear is not clear.

Thank you for your advice. The worn surface of particle packing was adhesive wear. The groove in the worn surface was abrasive wear.

5) Why the Bi area moves to wear surface?

Thank you for your advice. During the wear process, the soft Bi phase was extruded to form the self-lubricating film. The continuous film was easy to form during to the ductility of Bi phase.

Round 2

Reviewer 1 Report

Thanks for your replies.

Author Response

Thank you for your replies.

Reviewer 2 Report

The revised version Is not up to the mark, as pointed out below. Most of recommendations in the previous round of review was ignored or just touched, which is not acceptable. For example, previous recommendation regarding critical analysis of available literature and etc. The authors were given the opportunity to improve the manuscript, however, it seems that they have ignored it. Based on that, I reject the present manuscript. The details are as follows :

1.       The introduction section does not include critical analysis of the literature (previous suggestion was ignored).

2.       The composition of the alloy is vague and unclear without any proof against it (previous suggestion was ignored).

3.       The SEM images are not detail enough and the author’s excuse on that is not valid (previous suggestion was ignored).

4.       The counterbody of the tribology tests was not mentioned in the revised manuscript (previous suggestion was ignored).

Minor editing of English language required

Author Response

Dear editor:
   We are very sorry for the trouble for the manuscript. According with your advice, we amended the relevant part in the manuscript. Changes are highlighted in red in the manuscript. 

 

1. The introduction section does not include critical analysis of the literature (previous suggestion was ignored).

 

Thank you for your advice. We have amended and highlighted in red in the manuscript.

2. The composition of the alloy is vague and unclear without any proof against it (previous suggestion was ignored).

 

Thank you for your advice. We have added the phase diagram of Al-Bi alloys in the manuscript.

3. The SEM images are not detail enough and the author’s excuse on that is not valid (previous suggestion was ignored).

 

Thank you for your advice. We have changed the images in Fig.2 in the manuscript.

4. The counterbody of the tribology tests was not mentioned in the revised manuscript (previous suggestion was ignored).

 

We are sorry for wrongdoing. We have added the counterbody and highlighted in red in the manuscript.

 

Author Response File: Author Response.pdf