3D Printing of Mg-Based Bulk Metallic Glasses with Proper Laser Power and Scanning Speed

Round 1

Reviewer 1 Report

The current manuscript studies the effect of SLM process parameter on the quality of 3d printed Mg-based metallic glasses. The title is attractive and timely. However, there are a lot of significant issues to be considered as follows:

- The introduction section lacks a critical review of literature studies to illustrate the issues for processing the bulk metallic glasses using traditional or 3d printing techniques.

- The authors should refer to the source for selecting the applied process parameters.

- What is the standard used to select the sample size and geometry?

- The experimental work lacks a lot of tests and measurements that should be done to justify the authors' claims; such as relative density, microhardness test, tensile test, and microstructure SEM images through the sample's cross-section at higher magnification.  

- The resolutions and contrast of the presented images should be improved, figures 3 and 4.

- The Figures numbering should be revised through the text, eg. at line #111.

- Authors stated that "Sharp crystalline peaks appear on the XRD curves", what is the indication of that, please illustrate that through the manuscript?

- There is no comparison or evidence (images or measurements) of the difference in pore formation through each set of the applied process parameters.

- Compression test is not sufficient to characterize the mechanical properties, what about microhardness measurements and tensile test?

- Relative density should be measured to validate the optimum SLM process parameters, in addition to the SEM images through the sample's cross-section.

- Generally, the manuscript should refer to the most recent publications of the current study research area. 

- For the conclusion section, it is recommended to use the bullet points style to focus on the main results, significant contribution, and novelty of the current work. 

Author Response

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Reviewer 2 Report

The manuscript is of scientific interest, but it requires major revision before publishing.

Introduction does not explain, why authors chose such composition of the alloy. This should be added.

Authors do not provide detailed information about applied Methods (XRD, SEM). It is unclear did authors check the initial powder material before SLM? Or information in fig.1 was provided by distributor of the powder?

"Materials and methods" part does not contain any information about compressive tests. This should be corrected.

Authors writing about "more" or "less" crystalline phases according to the results of XRD. Authors shoul calculate the crystallinity according to the XRD results and provide the obtained data within the manuscript in the view of plot, columns or table. Such not-very-hard-to-calculate addition will make the obtained and described results more accurate and clear.

Authors found the mode of SLM, which allows to form crack-free samples. In my oppinion, this mode should be described as one of the main results of this manuscript.

Author Response

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Reviewer 3 Report

Manuscript numbered “metals-1795234” has been reviewed:

The introduction needs some improvements.

Please add a suitable scale bar for figures.

Please use the standard terminologies of ASTM/ISO 52900 for the correct terminologies of the Additive Manufacturing process. Use Laser-based powder bed fusion (LB-PBF) instead of selective laser melting (SLM).

Please add a section related to the economy of the process.

Please add the process parameter in a table.

Please add a comprehensive statistical study for results.

Fallowing papers are suggested for the introduction and result section:

3D printing in tissue engineering: a state of the art review of technologies and biomaterials

Additive manufacturing a powerful tool for the aerospace industry

Multimaterial powder bed fusion techniques

Author Response

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Round 2

Reviewer 1 Report

The revised version did not cover all the issues of the review comments and recommendations. There are a shortage of the experimental data to justify and validate the authors claims as reported before. 

The title, abstract , and conclusion are not completely supported with supported by the presented results. The presented data for a crack free samples are not sufficient. Also, the investigation method of determining the crystallinity percentage is not presented in detail.      

The claims from authors are not supported experimentally in a sufficient way. So, there should be an addition of the recommended experimental results; or they should adjust the title, abstract, and conclusion to be compatible with the presented results (in this case a re-evaluation of the manuscript should be conducted).   

Author Response

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Reviewer 2 Report

Authors significantly improved their manuscript, however they did not provide the detailed information about XRD and SEM methods (scanning angle range, acquisition time, scanning step for XRD, which mode of SEM was applied, type of detector, like mapping, or area analysis with SE or BSE detectors, etc.). Also, authors added data about crystallinity of measured samples, but he did not explain in "Materials and Methods", how was crystallinity calculated. Also, it is unclear, how did authors determined microhardness by optical microscopy? As far as I know, microhardness is measured by indentation; optical microscopy methods do not allow to measure microhardness. There must be some misprint? Authors should carefully check part 2 Materials and Methods.

Authors provide strss-strin curves. There one can see that the ductility of produced samples is very low. Authors should comment this within the text.

Author Response

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Reviewer 3 Report

The authors have addressed the issues raised previously, and the manuscript is suitable for publication in its current form.

Author Response

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Round 3

Reviewer 1 Report

The revised manuscript does not cover the experimental data that were recommended through the previous review reports.

As reported in the title, abstract, and conclusion that authors optimizes the processing parameters for the 3d printing of "crack-free Mg-based bulk metallic glasses". Please note that the presented data in the experimental results section did not justify or validate the title content. 

The lab closure in September is not an accepted reason to waive an academic work that should be a published reference.

The suggestion is to adjust the title, abstract, and conclusion to be compatible with the presented results and describe the current work content which is the investigation of processing parameters effect on the 3d printed Mg-based metallic glasses. Or, to add the experimental results that accurately describe the title, abstract, and conclusion. 

Best regards,   

Author Response

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Reviewer 2 Report

The manuscript was improved. I would recommend authors carefully check english one more time before publication.

Author Response

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Round 4

Reviewer 1 Report

The revised does not include any technical editing according to the review comments and recommendations.

Please note that the presented work is interesting, however, the purpose of the previous review notes is to evaluate the manuscript and to help to publish the current work in justified technical and academic way.

As reported by authors that there is no chance to apply more experimental tests. It is recommended to remove the word "Crack-free" from the title and the conclusion because there is no validation of the crack-free case.

The title, abstract, and conclusion should focus only on the validated data presented in the results and discussion section. Also, please note that the results and claims should be validated by two independent methods or by referring to the literature studies.    

Author Response

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