Brittle-Ductile Transition in Laser 3D Printing of Fe-Based Bulk Metallic Glass Composites
Round 1
Reviewer 1 Report
The effect of the processing parameters on the microstructure and mechanical properties of Fe-based BMG composites is studied in this work. In my opinion the paper is interesting and could deserve publication provided some changes are made.
First of all, English language should be corrected. There are many mistakes: sentences without verbs, wrong prepositions, etc...
In the results section, the authors identify two peaks as bcc-Fe (110) and (200). In Cu-radiation experiments, (110) peak should be at 45º and (200) at 65º, which are not observed in those positions in fig 1b. Are the XRD patterns correctly identified?
Author Response
Point 1: First of all, English language should be corrected. There are many mistakes: sentences without verbs, wrong prepositions, etc...
Response 1: The full text of English language was corrected in the resubmitted manuscript.
Point 2: In the results section, the authors identify two peaks as bcc-Fe (110) and (200). In Cu-radiation experiments, (110) peak should be at 45º and (200) at 65º, which are not observed in those positions in fig 1b. Are the XRD patterns correctly identified?
Response 2: The XRD has been recalibrated in the resubmitted manuscript. The right-ward shift of the peaks could possibly be due to the residual stress or defects of the microstructure.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors provide a paper dealing with the brittle-ductile transition in laser 3D printing of Fe-based bulk metallic glass composites. The paper can be of interest for Metals, but it needs serious improvements.
1. Avoid the use of symbols in the abstract if they are not defined.
2. The nanoindentation data must be improved in the continuous stiffness measurement configuration in which the H and E are provided as a function of the indentation depth. This would be better to analyze the trend of these properties avoiding artifacts.
3. A comment must be made about the typical size of the 3D printed objects. Specifically, the authors must comment how the size of this materials affect the crystallization behavior and the mechanical properties. Concerning the first point the authors must be aware that increasing the size of the specimen there is the possibility that the core of the BMG will stay amorphous. Instead concerning the second point the authors must be aware that the mechanical properties of metallic glass are strongly size dependent. The authors must be helped by the following paper which is worth to discuss doi.org/10.1016/j.actamat.2017.03.072 and doi.org/10.1016/j.actamat.2015.02.038 where they can see that reducing the size of the specimen, there is an increment of mechanical properties for thin film metallic glass. This is also something which could happen for small scale 3D printed materials.
4. I would like that the authors comment about the typical materials shape and the maximum size which can be obtained with 3D printing of Fe-based metallic glass avoiding crystallization.
Author Response
Point 1: Avoid the use of symbols in the abstract if they are not defined.
Response 1: Corrected in the resubmitted manuscript.
Point 2: The nanoindentation data must be improved in the continuous stiffness measurement configuration in which the H and E are provided as a function of the indentation depth. This would be better to analyze the trend of these properties avoiding artifacts.
Response 2: The hardness and elastic modulus are provided as a function of the indentation depth is shown in Figures 5(a) and 5(b) in the resubmitted manuscript.
Point 3: A comment must be made about the typical size of the 3D printed objects. Specifically, the authors must comment how the size of this materials affect the crystallization behavior and the mechanical properties. Concerning the first point the authors must be aware that increasing the size of the specimen there is the possibility that the core of the BMG will stay amorphous. Instead concerning the second point the authors must be aware that the mechanical properties of metallic glass are strongly size dependent. The authors must be helped by the following paper which is worth to discuss doi.org/10.1016/j.actamat.2017.03.072 and doi.org/10.1016/j.actamat.2015.02.038 where they can see that reducing the size of the specimen, there is an increment of mechanical properties for thin film metallic glass. This is also something which could happen for small scale 3D printed materials.
Response 3:
First point: From the SEM images of the cross section of the samples, it can be seen that with the increase of the thickness of the sample, the cooling rate becomes slower and the crystalline phase increases gradually. This was discussed in the section 3.1 in the resubmitted manuscript (marked in red).
Second point: There is no doubt that the mechanical properties of metallic glass are related to the size. However, with the increases of the thickness of the samples, the volume fraction of crystalline phase increases gradually, and the effect of crystallization on the mechanical properties of the sample becomes more and more prominent. In this paper, we mainly study the effect of crystalline phase on the mechanical properties of metallic glass. This is discussed in the section 3.2 in the resubmitted manuscript (marked in red).
Point 4: I would like that the authors comment about the typical materials shape and the maximum size which can be obtained with 3D printing of Fe-based metallic glass avoiding crystallization.
Response 3: The shape and size of the samples are supplemented in detail in the section 2. In our present experimental conditions, we can print completely amorphous on the surface of printed ordinary crystal components, which greatly releases the limitation of the size of Fe-based amorphous components.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The manuscript has been improved and may deserve publication.
Reviewer 2 Report
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