On the Grain Microstructure–Mechanical Properties Relationships in Aluminium Alloy Parts Fabricated by Laser Powder Bed Fusion

Round 1

Reviewer 1 Report

1) The authors have reported the EBSD maps for the 3 orientations and the related grain structure analysis. Moreover, it has been stated that the grains have almost random orientation. However, would the authors also add the Inverse pole Figures and the Pole Figures of the surface, side and cross-section for each different specimen orientation and comment them?

2) In Fig. 7, for the as-printed and polished conditions, the sample with XZ orientation shows a higher strain values than the ZX and XY orientations. On the contrary the XZ orientation reveals the lower strain after sandblasting. Would the authors better expalin this bevahviour? How many tensile tests have been preformed for each conditions?

Author Response

Authors would like to thank the reviewers for the detailed comments and suggestions for the manuscript. We believe that the comments have identified important areas which required improvement. After completion of the suggested edits, the revised manuscript has benefitted from an improvement in the overall presentation and clarity. Below, you will find a point-by-point description of how each comment was addressed in the manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors examine the effect of surface treatments on the orientation-dependent properties of Al alloy parts manufactured by selective laser melting.  The experimental work is systematic.  Recommendation is minor revisions (no additional review is necessary).

Specific comments:

• Explain the horizontal axis on Figure 6 (both in the text and in the figure caption).
• The authors use ellipsis in a strange way (e.g., 60…70 MPa). It is usual (standard?) to use the hyphen (60-70 MPa).
• The authors’ reporting of experimental observations is good, but the discussion of (possible and known) mechanisms is very short and dry. Perhaps more thought should be given to the questions of why certain treatment affect certain property in a specific way?  (If rigorous explanations are lacking, speculations are OK.)

Author Response

Authors would like to thank the reviewers for the detailed comments and suggestions for the manuscript. We believe that the comments have identified important areas which required improvement. After completion of the suggested edits, the revised manuscript has benefitted from an improvement in the overall presentation and clarity. Below, you will find a point-by-point description of how each comment was addressed in the manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

In this paper, the selective laser melting technology was used to prepare 3D printed Al-Mg-Si RS-333 alloy, and the microstructure characteristics and mechanical properties of different preparation directions were studied. The research necessity is sufficient, the research methods are advanced, and the research content is informative. In this paper, the mechanical properties of materials after 3D printing, surface polishing and sand blasting were systematically analyzed. And further research contents were excavated according to the existing phenomena. But part of the statement is not clear enough, easy to produce self-contradiction. Therefore, it is necessary to modify the expression of the writing.

1. The topic is not specific enough. The title of the paper should be specific and clear to clarify the research content of this paper, while "Some Aspects" is not specific enough, so it is suggested to modify it. The full name of SLM is recommended in the title.
2. The introduction and application of selective laser melting technology occupy too much space in the abstract part.
3. The English tense needs to be modified. For example, the past tense should be used in the following statements in the abstract: “Surface polishing to reduce Young’s modulus and yield strength, but improves ductility, whereas the influence of sand blasting is more controversial. The experimental results are dis-cussed in connection with the grain morphology and orientation.”
4. In the EBSD Map of XY printing orientation, the size of the columnar grains parallel to the growth direction looks smaller, and there are more fine equiaxed crystals, but it corresponds to a lower Young's modulus value. The author needs to explain the reasons.
5. The author mentioned that the hardness of ZX surface and side is isotropic (about 0.8g), but the grain morphology of the two are equiaxed and columnar, respectively. The Young's modulus values of the two are also different in Fig. 3. Why do different grain morphologies have the same hardness values?
6. Lines 326-328 in the manuscript mentioned: "The same general mechanical response for all printing orientations studied is inherited after mechanical polishing, bringing tensile strength characteristics and ductility to somewhat higher values and reducing, however, Young's modulus and yield strength. "And lines 335-336 mentioned: "The presence of tensile residual stresses in the superficial layer would reduce apparent yield strength and, perhaps, elongation till rupture." The author believes that surface defects may lead to lower apparent yield strength, however Why does the yield strength of the material decrease after removing the surface?
7. The conclusion is too lengthy; The conclusion is a brief summary of the research results obtained in this paper. It’s not suitable to expect too much for further research. The conclusions are based on one's own research, usually without references.
8. Please check out the English grammar and spelling carefully.

Author Response

Authors would like to thank the reviewers for the detailed comments and suggestions for the manuscript. We believe that the comments have identified important areas which required improvement. After completion of the suggested edits, the revised manuscript has benefitted from an improvement in the overall presentation and clarity. Below, you will find a point-by-point description of how each comment was addressed in the manuscript.

Author Response File: Author Response.pdf