Characterizing Changes in Grain Growth, Mechanical Properties, and Transformation Properties in Differently Sintered and Annealed Binder-Jet 3D Printed 14M Ni–Mn–Ga Magnetic Shape Memory Alloys

Round 1

Reviewer 1 Report

Dear Authors,

the manuscript is much improved in its form and content, although the data reported could be supported by further measurements.

However, I appreciate the effort made by the authors for satisfying the referees' requests. 

For this reason, I accept the manuscript in its current form.

Author Response

Reviewer 1 Response:

Thank you for your comments and review of our manuscript. The authors appreciate your support.

Reviewer 2 Report

In this manuscript entitled "Characterizing Changes in Grain Growth, Mechanical Properties, and Transformation Properties in Differently Sintered and Annealed Binder-Jet 3D Printed 14M Ni-Mn-Ga Magnetic Shape Memory Alloys", the authors have investigated the microstructure and related physical properties ( e.g. mechanical and magnetic properties) of the binder-jet 3D printed Ni50Mn30Ga20 using EDS, AFM, MFM, Neutron diffraction, DIC micrographs, DSC and Magnetization curves, etc. The research of this work is impressive and interesting. But some revisions are needed to make the work acceptable.

1. The authors claim that the clusters are observed. However, the clusters can not be clearly seen in Fig. 2 and/or Fig. 3. Can the authors mark them in these figures?

2. Some structure characterizations such as SEM and XRD are expected to be provided.

3. SEM and particle size, saturation magnetization, and magnetic coercivity have been studied in some related papers (Journal of Applied Physics131, 043901 (2022); Journal of Physics: Condensed Matter 33 (2021) 285802;Journal of Applied Physics 115, 233911 (2014) ). The authors should refer to these references and cite them in the Results and Discussion part.

4. "magnetic coercivity approximately 30 mT are observed for the non-heat-treated samples, ...and reduces magnetic coercivity to approximately 5 mT. "30 mT？5 mT？These values are obviously inconsistent with the data in the figures. The authors are advised to recheck the coercivity valuecarefully. The calculation method of coercivity can be obtained in references recommended above and the authors can refer to these references.

Author Response

Reviewer 2 Response:

Point 1: The authors claim that the clusters are observed. However, the clusters can not be clearly seen in Fig. 2 and/or Fig. 3. Can the authors mark them in these figures?

Response 1: Exemplary neutron diffraction area detector clusters have been marked in figure 2 using arrows.

Point 2: Some structure characterizations such as SEM and XRD are expected to be provided.

Response 2: One of the main objectives of this manuscript was to confirm the XRD findings from the previous study (ref. [24]) via neutron diffraction which provides much more accurate lattice parameters and easy modulation identification for Ni-Mn-Ga modulated and non-modulated martensites. Thus, we refer to the ref 24 for XRD patterns. We added SEM micrographs as supplementary figure S1 which show some microstructural details, but are not a visually appealing do to carbon contamination.

Point 3: SEM and particle size, saturation magnetization, and magnetic coercivity have been studied in some related papers (Journal of Applied Physics131, 043901 (2022); Journal of Physics: Condensed Matter 33 (2021) 285802;Journal of Applied Physics 115, 233911 (2014) ). The authors should refer to these references and cite them in the Results and Discussion part.

Response 3: The papers suggested here are interesting, but we find that the only reference of related to our paper is (Journal of Physics: Condensed Matter 33 (2021) 285802) and their discussion on coercivity measurement. We have added that reference as ref. [53].

Point 4: “magnetic coercivity approximately 30 mT are observed for the non-heat-treated samples, ...and reduces magnetic coercivity to approximately 5 mT. "30 mT？5 mT？These values are obviously inconsistent with the data in the figures. The authors are advised to recheck the coercivity valuecarefully. The calculation method of coercivity can be obtained in references recommended above and the authors can refer to these references.

Response 4: The authors appreciate this finding and suggested paper, used the information in the paper and corrected the coercivity values.

Reviewer 3 Report

In the manuscript, the authors presented systematic comparisons in microstructural, mechanical and transformation properties of binder-jet Ni-Mn-Ga shape memory alloys in as-sintered and annealed conditions. The results indicate the 10°C difference in sintering temperatures (1080°C vs 1090°C) can lead to significant difference in grain size, hardness, porosity, martensitic transformation temperatures etc in the Ni-Mn-Ga alloys. Overall this manuscript is very good written and the topic matches well the scope and aims of Metals. There are a few minor points that the authors may want to address to make the manuscript easier to follow. 

1) The clusters for grain with large enough size counted from the neutron diffraction patterns shows good agreement with the grain size evolution in the two sintered samples (1080°C vs 1090°C). Could the author add a few sentences to address the criteria (contrast, brightness etc) used to count the clusters?

2) How many nanoindentation tests were preformed on each sample and what is the spacing used? As indicated by the authors, the harness value is orientation-dependent. Consider the grain size (~40-90um) and the indentation depth (400nm),  indentation spacing must be large enough to get a meaningful comparison between the average hardness of different samples.

3) It is hard to distinguish the grain boundaries/morphologies from Figure 4, especially for the 1080°C sintered samples. Could the author highlight the grain boundaries or provide any other data (e.g. SEM, EBSD etc) to show grain morphologies in these samples?

4) In terms of the hardening effects (Page 7, Paragraph 2), could the author comment whether the twinning and martensitic transformation can contribute to the hardening in the Ni-Mn-Ga alloys, and if so, how this could lead to the different hardening behaviour in the 1080°C and 1090°C sintered samples?  

5) Could the author add the SEM images to show the indents. The image was described in the manuscript (page 8, paragraph 2), but i can not find it in the current manuscript.

Author Response

Reviewer 3 Response:

Point 1: The clusters for grain with large enough size counted from the neutron diffraction patterns shows good agreement with the grain size evolution in the two sintered samples (1080°C vs 1090°C). Could the author add a few sentences to address the criteria (contrast, brightness etc) used to count the clusters?

Response 1: Cluster counting was not performed utilizing software or automation, but rather by visual inspection. Although subject to human bias/error, there was over 45 images counted for each sample, with nearly 70 distinct clusters identified for the 1090 °C sintered samples, and approximately 25 counted for 1080 °C sintered samples. Due to experimentation variability and brightness variation, software counting for this step would have been largely up to the operator to determine what constituted a cluster as well. For this reason, qualitative interpretation was performed for all four samples to determine, to a general degree, the presence of distinct and bounded clusters on the neutron diffraction area detector images. There is a brief addition to the manuscript to address this.

Point 2: How many nanoindentation tests were preformed on each sample and what is the spacing used? As indicated by the authors, the harness value is orientation-dependent. Consider the grain size (~40-90um) and the indentation depth (400 nm), indentation spacing must be large enough to get a meaningful comparison between the average hardness of different samples.

Response 2: In this study, we performed 10 indents per sample spaced at least 100 µm apart to cover the entire sample. We additionally took extra precaution to make sure indents were taken at varying distances from the pores and in respective and distinct grains. This was unclear in the current manuscript, but text has been added correspondingly.  

Point 3: It is hard to distinguish the grain boundaries/morphologies from Figure 4, especially for the 1080°C sintered samples. Could the author highlight the grain boundaries or provide any other data (e.g. SEM, EBSD etc) to show grain morphologies in these samples?

Response 3: We have included a new figure (supplementary figure S2) showing exactly this. These SEM images should provide adequate representation of the grain boundaries for respectively sintered samples.

Point 4: In terms of the hardening effects (Page 7, Paragraph 2), could the author comment whether the twinning and martensitic transformation can contribute to the hardening in the Ni-Mn-Ga alloys, and if so, how this could lead to the different hardening behavior in the 1080°C and 1090°C sintered samples? 

Response 4: It was determined that the twinning effects were largely absent in any significant way on the calculated hardness values. We state this from the lack of significant pop-in event in the stress-strain curves obtained from the nanoindentation curves as well as lack of characteristic twinning surface topography in SEM micrographs of the indentations except for one indent that we are showing in supplementary figure S3(a).

Nevertheless, the effect of grain orientation on hardness and indentation behavior needs to be studied in general for modulated Ni-Mn-Ga to evaluate if statistically significant differences can be found. This is not focus of this study.

Point 5: Could the author add the SEM images to show the indents. The image was described in the manuscript (page 8, paragraph 2), but i can not find it in the current manuscript.

Response 5: We included two SEM micrographs as supplementary figure S3.

Round 2

Reviewer 2 Report

The manuscript has been revised according to the Reviewer's comments.  It can be accepted in present form.

Author Response

Dear Reviewer, thank you very much for your positive feedback.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript entitled “AAA” dealing with AAA has been reviewed with great attention. Please comments are listed below:

1. Expand the section on materials and methods by adding more info about the binder jetting machine.
2. Make the wording in Figure 5 smaller.
3. The wording in Figure 6 is too big. Sort this out.
4. Figure 7 doesn’t have a scale bar. Add the scale bar for sub-figures.
5. Expand the conclusions. Suggesting to add some wording about the results in the conclusions.
6. Read comprehend and add the following updated references to the introduction.

Li, J., R. Yan, Y. Yang, and F. Xie, Water-based binder preparation and full-color printing implementation of a self-developed 3D printer.

Lopez Taborda, L.L., H. Maury, and J. Pacheco, Design for additive manufacturing: a comprehensive review of the tendencies and limitations of methodologies.

Singh, S.N., V.S.S. Venkatesh, and A.B. Deoghare, A review on the role of 3D printing in the fight against COVID-19: safety and challenges.

7. Compare the quality of the binder jetting to material jetting presented in the following articles.

Cheng, Y.-L. and T.-W. Tseng, Study on driving waveform design process for multi-nozzle piezoelectric printhead in material-jetting 3D printing.

Kardel, K., A. Khoshkhoo, and A.L. Carrano, Design guidelines to mitigate distortion in material jetting specimens.

Author Response

The authors appreciate the comments of reviewer 1. Here are detailed answers.

Point 1: Expand the section on materials and methods by adding more info about the binder jetting machine.

Response 1: More information regarding the printing parameters is explored in the revised version. This was mostly taken from ref. 24 which provided the samples utilized in this study. Included parameters of layer height, spread speed, feed/built powder ratio, drying time, saturation, and binder composition was added.

Point 2: Make the wording in Figure 5 smaller.

Response 2: Noted are inconsistencies in the text sizing throughout the paper. These will be addressed for all figured, however the primary culprits were Figures 5 and 6.

Point 3: The wording in Figure 6 is too big. Sort this out.

Response 3: See above comment, has been addressed.

Point 4: Figure 7 doesn’t have a scale bar. Add the scale bar for sub-figures.

Response 4: The scale has been stated in the figure text as 20 x 20 µm² for the size of the red rectangles. However, scale bars will still be added to the figure to guide the reader.

Point 5: Expand the conclusions. Suggesting to add some wording about the results in the conclusions.

Response 5: The conclusion has been slightly modified to include additional specifics regarding the results of this study, as well as some clarification on various differences between the measured samples.

Point 6: Read comprehend and add the following updated references to the introduction.

Response 6: Although the introduction of the binder jetting technique in the text could be possibly expanded, the references suggested are unrelated to the present work. Even though the current COVID-19 pandemic highlights the possible usage of 3D-printing in the current market for effective mask filtration, this is not appliable to the topic of this article. Also, all the other mentioned references are unrelated to the presented work, except for certain keywords in the title.

Point 7: Compare the quality of the binder jetting to material jetting presented in the following articles.

Response 7: Similarly to above, material jetting is not introduced and it is assumed the reader understands the difference between the various additive manufacturing mechanisms.

Reviewer 2 Report

The paper “Characterizing Changes in Grain Growth, Mechanical Properties, and Transformation Properties in Differently Sintered and Annealed Binder-Jet 3D Printed 14M Ni-Mn-Ga Magnetic Shape Memory Alloys“ deals with a  study of Ni-Mn-Ga Heusler alloy prepared by binder-jet 3D printing. It continues previous studies and completes them with some new results. 

My selected comments:

Section 1

Page 2, lines 73 - 75

The sentence beginning “Finally, the microstructural magnetic landscape is presented by magnetic force microscopy and magnetization curves presented using vibrating sample magnetometry.“ is somewhat funny. I would say that magnetic force microscopy (MFM) scans the sample and reflects the magnetic structure of the sample surface and vibrating sample magnetometer is used for a measurement of magnetization curves. “Landscape” is possible to see, e.g. from a plain.

Section 2

Page 4, lines 148 - 150

Vibrating sample magnetometer does not produce magnetization curves. It is used for measurement of magnetization curve from which the saturation (remnant) magnetization and coercivity can be determined. What do the authors mean with “hysteresis width”?

The hysteresis curves are depicted in Fig. 8 on page12 where mixed SI and cgs units are used. It is inaccessible. This is valid also for units used in the text below.

Section 3

Page 5 , line 180

No information concerning c/a ratio and 14M pseudo-orthorhombic martensitic structure is present in Ref [22].

Page 6, lines 196 – 199

The sentence beginning “The results suggest that ………” is not clearly formulated and it is grammatically incorrect. It should be corrected. From the next sentence “Furthermore, it also shows….” it is not clear, to what “it” is related. Please improve it.

Page 7, lines 216 – 218

The statement of authors in the sentence beginning “It was seen that…..“ is vague. Please reformulate it.

Lines 245 –247: I would say that after the sintering at 1090 °C the relative density is higher compared to the sintering at the temperature 1080 °C.

The whole paragraph between lines 238 – 249 should be rewritten into correct and comprehensible English.

Similarly, the text on page 8 contains several grammatically incorrect and often difficult comprehensible sentences or expressions. For example: lines 282 – 283, what does is mean that the samples were not previously trained? Should it be “strained” or “mechanically treated”? Next line 302: what does it mean physically “compounded error”?

Page 9, lines 315:

The text in paragraph beginning “Clearly, indentation tests….” is not clear. It should be corrected.

Line 327: caption of figure 5: what does it mean “Larger displacement in the 1080 °C”?

Page 10

Figure 6 shows the DSC curves at increasing and decreasing temperature. This could be denoted by arrows on the curves. The curves reflect very probably transformation temperatures and not “transformative properties”. These temperatures are somewhat different compared to those published in Ref. [24] even if the samples are, according authors statement, equivalent and the heating and cooling rates of 5 °C/min were also the same. Could the author comment it?

Similarly, the not very clear statements are also present on pages 11 and 12. Please read the paper carefully and correct it from the physical as well as English viewpoints.

I do not recommend the paper for publication in the present state.

Author Response

The authors appreciate the constructive and detailed comments of reviewer 2. Please find the answers to each point below.

Point 1: Section 1, Page 2, lines 73 – 75, The sentence beginning “Finally, the microstructural magnetic landscape is presented by magnetic force microscopy and magnetization curves presented using vibrating sample magnetometry.“ is somewhat funny. I would say that magnetic force microscopy (MFM) scans the sample and reflects the magnetic structure of the sample surface and vibrating sample magnetometer is used for a measurement of magnetization curves. “Landscape” is possible to see, e.g. from a plain.

Response 1: This point is taken and agreed with. The ‘magnetic landscape’ is omitted in the revised sentence and follows instead to be: “Finally, magnetic force microscopy (MFM) was utilized to observe surface magnetism characteristics and vibrating sample magnetometry (VSM) performed to obtain magnetization curves within a modest applied magnetic field.”

Point 2: Page 4, lines 148 – 150, Vibrating sample magnetometer does not produce magnetization curves. It is used for measurement of magnetization curve from which the saturation (remnant) magnetization and coercivity can be determined. What do the authors mean with “hysteresis width”?

Response 2: This point is taken and agreed with that the wording is largely misleading. It was implied that the magnetic hysteresis width is the distance of the hysteresis curves at zero magnetization, but this is simply the coercivity. A unifying nomenclature is adopted for the remainder of this paper and ‘hysteresis width’ is omitted going forward.

Point 3: The hysteresis curves are depicted in Fig. 8 on page12 where mixed SI and cgs units are used. It is inaccessible. This is valid also for units used in the text below.

Response 3: For both the Figure and the text, consistent SI units will be used. All instances of G has been adjusted to T (or mT).

Point 4: Section 3, Page 5 , line 180, No information concerning c/a ratio and 14M pseudo-orthorhombic martensitic structure is present in Ref [22].

Response 4: We appreciate this finding, this reference was incorrectly typed. Reviewing the references for this paper, this has been adjusted in the revision.

Point 5: Page 6, lines 196 – 199, The sentence beginning “The results suggest that ………” is not clearly formulated and it is grammatically incorrect. It should be corrected. From the next sentence “Furthermore, it also shows….” it is not clear, to what “it” is related. Please improve it.

Response 5: This has been noted and edited accordingly. In particular, it was suggesting that the ‘cluster counting’ step indicates the following results, but the lack of clarity is observed and rewritten.

Point 6: Page 7, lines 216 – 218, the statement of authors in the sentence beginning “It was seen that…..“ is vague. Please reformulate it.

Response 6: This is more adequately conveyed in the revision. The sentence was rewritten to be more succinct in the revised version.

Point 7: Lines 245 –247: I would say that after the sintering at 1090 °C the relative density is higher compared to the sintering at the temperature 1080 °C.

Response 7: The revised version has been adjusted to accommodate this point. It is agreed that it would be more efficient to state this than is does in the current state. Most of the paragraph was rewritten.

Point 8: The whole paragraph between lines 238 – 249 should be rewritten into correct and comprehensible English.

Response 8: See previous comment. Most of the paragraph has been rewritten to flow better and convey the major points more effectively. Much of the previous text did not flow well.

Point 9: Similarly, the text on page 8 contains several grammatically incorrect and often difficult comprehensible sentences or expressions. For example: lines 282 – 283, what does is mean that the samples were not previously trained? Should it be “strained” or “mechanically treated”? Next line 302: what does it mean physically “compounded error”?

Response 9: This page has been reviewed and edited to improve the grammar and English. In particular, the section regarding mechanical training refers to the uniformization of the twin variants via pre-service mechanical loading. The authors have referred the reader to ref. 21 for more information on the training process. Regarding “compounded error”, this is omitted in the revision due to lack of clarity, originally pointing to the result of various sources of error accumulated during experimentation.

Point 10: The text in paragraph beginning “Clearly, indentation tests….” is not clear. It should be corrected.

Response 10: The purpose of this sentence is to highlight the difference between macro-indentation and nanoindentation for the respective interaction with the porous network. It is understood that this sentence is unclear and was revised accordingly.

Point 11: Line 327: caption of figure 5: what does it mean “Larger displacement in the 1080 °C”?

Response 11: This has been revised, instead stating ‘deformation’ instead of ‘displacement’, as well as elaborating on which sample exactly was used in this graphic.

Point 12: Figure 6 shows the DSC curves at increasing and decreasing temperature. This could be denoted by arrows on the curves. The curves reflect very probably transformation temperatures and not “transformative properties”. These temperatures are somewhat different compared to those published in Ref. [24] even if the samples are, according authors statement, equivalent and the heating and cooling rates of 5 °C/min were also the same. Could the author comment it?

Response 12: On the newest revision of this document, Figure 6 has been slightly edited to improve the font size, but will also include arrows to denote which direction is upon heating and which direction is upon cooling. Additionally, the point is taken regarding ‘transformative properties’ versus ‘transformation temperatures’, as the latter is less ambiguous. These are revised throughout the paper. Finally, regarding the comparison of samples with our previous paper (ref. [24]), the authors state that the samples are equivalent but not identical. In particular, the severe compositional sensitivity of Ni-Mn-Ga alloys and their phase transformation temperatures is the reason for differences in DSC results to our previous paper. For example, slight compositional variation during the alloying step could impact the solidus temperature and in turn affecting the liquid-phase sintering behaviour and potential Mn segregation at the grain boundaries. Our results in this paper reflect the literature assuming non-negligible Mn segregation (see ref. [51]) on the martensitic phase transformation temperature.

Point 13: Similarly, the not very clear statements are also present on pages 11 and 12. Please read the paper carefully and correct it from the physical as well as English viewpoints.

Response 13: The end of the paper has been reviewed in detail to improve any ambiguous statements. In particular, the section reviewing transformation temperatures has been largely revised to flow better with improved and comprehensible English. English language has been reviewed for the entire manuscript by the native English-speaking authors of this manuscript.

Reviewer 3 Report

Aaron Acierno  et al. report the microstructural, mechanical and magnetic characterization of a couple of as-sintered and post annealed 14M Ni-Mn-Ga samples, fabricated by  binder Jet 3D printing.

The research area is relevant and interesting : these additive manufactured polycrystalline MSMA have recently attracted extensive attention due to the significantly high MFIS they can develop by properly tailor the porous microstructure. All the preparation and post treatment parameters aimed to enhance the magneto-structural properties of these materials are then relevant and interesting.

The same authors, in ref [24], studied a very large number of samples and identify three sintering areas in which the systems have different morphological and structural characteristics. In that very interesting paper, the mechanisms of microstructural changes by varying the sintering temperature and their effects on the magnetic properties have been clearly shown.

The present manuscript concerns the characterization of two samples of the same series presented in ref [24] and the characterization of each, after a post annealing treatment. The relevant results emerged from the microstructural and magnetic characterization (eg 14M lattice parameters, grain size, porosity, density, saturation magnetization, martensitic temperature) have been clearly presented and well discussed in [24]. Although a new technique, neutron diffraction, has been used for the crystallographic characterization of polycrystals, it does not provide additional information to the previously published XRD data. In fact, the discussion on neutron diffraction maps, which is given much prominence for the qualitative determination of the particle size, although interesting from the didactic point of view, is superfluous.

One of the novelties concerns the partial recovery of the martensitic transition temperature with post annealing for the sample at 1090 ° C. This evidence is attributed to the improvement of chemical homogeneity in the sample, but not experimentally demonstrated. In any case, it is not enough, in my opinion, to support the concept of tailoring which requires, instead, a systematic study in a wider range of temperatures.

Finally, the mechanical property results obtained from indentation experiments are not supported by sufficient measurements and considerations. In fact, given the complexity of the materials studied, factors such as crystallographic anisotropy, grain orientation with respect to the indentation direction, local chemical inhomogeneities must be rigorously investigated. For example, the authors attribute the shift in transition temperature in the 1090 ° C sample to chemical inhomogeneity and precipitation of Mn: hardness and elastic moduli calculated from local measurements such as indentation are certainly affected by such variations. Since they do not study the length scale of chemical inhomogeneity, it is not possible to draw conclusions about the average mechanical properties. In addition, due to the porosity of the samples, the size of the indentations relative to the length scale of the porous microstructure must also be taken into account for the determination of the average mechanical properties.

So I'm sorry to report that my opinion is that there isn't enough new material or enough insights to support a publication in this Journal.

Round 2

Reviewer 1 Report

The paper is ready for publishing in this journal.

Author Response

The authors want to thank Reviewer 1 for their constructive comments about the text, figures, and references. In particular, the figure comments regarding text size and format were extremely useful in guaranteeing that the figures convey information effectively and clearly to the reader while maintaining the original intent of the text. The authors appreciate the time taken to review the paper twice, and the comments provided to improve the overall scope of the paper.

Reviewer 2 Report

The comments are summarized in an enclosed report.

Comments for author File: Comments.pdf

Author Response

General Response: The authors want to thank Reviewer 2 for all the comments. As most concerns are regarding language considerations, this version has been reviewed by another native English speaker and revised accordingly. The authors hope that convoluted and unclear language has been remove or improved.

Point 1:

Abstract

Page 1

Lines 22-26

I cite: “Through nanoindentation, a greater resistance to plasticity and larger elastic

modulus was noted in 1090 °C sintered samples compared to the less densified (~95%

1. ~80% density) 1080 °C sintered samples.”

1) “was” should be replaced by “were”;

2) “samples compared to the less densified (~95% vs. ~80% density) 1080 °C sintered

samples” should be replaced, e.g., by ”samples of density ~95% compared to the

samples sintered at 1080 °C yielding lower density (~80%)”.

3) “Analysis of transformation temperatures presented a decreased martensite phase

transformation temperature for samples sintered at 1090 °C, but was partially increased

by a heat-treatment step.” This sentence is unclear and should be reformulated. Lines

28-30:

“This study asserted that a 10 °C sintering temperature difference can largely affect the

microstructure and mechanical and transformation temperatures while still allowing for the presence of magnetic twin variants in the resulting modulated martensite. “ should be probably “This study has shown that..”. My question is: which mechanical temperature(s) were affected (line 29)?

Response 1: All of these have been considered and revised. Additionally, the entire abstract has been revised where unclear English is presented.

Point 2:

Section 1

Page 2, lines 73 - 75

The word “utilized” should be replaced by “used” or “applied”. MFM is used in a study of the

“surface magnetism” or “surface magnetic structure”; “surface magnetism structure” is not

correct.

Response 2: This section regarding MFM surface magnetic structure has been revised, as well as the entirety of section 1 where English is unclear.

Point 3:

Page 3, lines 85 – 88

The inserted sentence (red colour) does not describe the printing process in the proper and

understandable way. For example. What does it mean “Printing was performed at a layer height of 100 µm…”? Does it mean that the thickness of one layer is 100 µm? Similarly, the sentence beginning “Layers were bound utilizing….” Do the authors mean that the prepared powder was mixed with a binder adjusted for printing procedure and subsequently printed under defined conditions?

My remark to the sample denotation. The authors should consider to simplify the sample

denotation in the sect 2. For example: the sample sintered at 1080 °C might be denoted as S1080 and after additional treatment as S1080t, the other ones as S1090 and S1090t. This could simplify the sentences and make the text more understandable.

Page 4, lines 153-155

The magnetization (or better hysteresis) curves were measured using vibrating sample

magnetometer in the external magnetic field ±1.5T (not for the magnetic field). The values of

saturation magnetization and coercivity are determined (not identify) from the measured curves.

Response 3: The printing parameters listed here provide most of the essential information required to characterize the printing step for our samples. More information regarding these parameters can be found in review papers for readers unclear. With regards to the comments above, layer thickness (now corrected from layer height) is 100 µm, and the binder was deposited on a virgin layer.

The comment regarding sample denotation is taken but will not be pursued. There are some muddy points through the revised paper that follow from poor English, but these have been majorly corrected throughout the manuscript and the manuscript should flow much better without the sample ID rewrite. The authors think that it may be easier for a reader to not have to remember a sample ID and what it means, but to provide the full sample description. We used samples IDs in the past in several papers and had each time reviewers that requested changes to full sample descriptions instead.

Regarding the VSM section, these have been improved, and the overall English in section 2 has been revised.

Point 4:

Section 3

Page 6, lines 199 – 206

The paragraph beginning “A cluster counting ….” should be reformulated. The sentences are

too long and not clear. The corrected sentence beginning “The large difference in ………” is

still not clearly formulated. How does the cluster counting relate to the grain size?

Response 4: This section, especially the beginning of the paragraph, has been largely rewritten to flow better and contain more comprehensible English.

Point 5:

Page 7, lines 225 – Page 8 lines 228

The optical microscopy has made the individual grains visible and allowed to determine their

number at an area of defined size which, as I hope, was the same for all samples. It should be

mentioned. Only in a such a way it is possible to make a comparison among individual states

of the samples.

Response 5: This has been added, as well as the paragraph edited for more appropriate English.

Point 6:

The whole paragraph between lines 248 – 260 should be rewritten from the viewpoint of physics and comprehensible English. Nanoindentation is one method yielding information concerning hardness and the measurements should be done on a well-prepared surface. Did the authors consider this effect? The Archimedes' principle is another method used for determining the volume and therefore the density of predominantly irregularly shaped objects. My note: this method is not mentioned in section 2. To a certain level, the results of nanoindentation measurements can be discussed in the connection with density of samples. The authors try to do it but their discussions (not only in this case) are often connected with large number of detailed results of other authors which, together with weak English formulations, makes the paper long and unnoticed

Response 6: This entire section has been rewritten and reviewed to present more comprehensible English. The samples were prepared prior to nanoindentation through polishing, so it is assumed that all samples are unbiased in terms of sample preparation. The method of Archimedes’ principle was added to section 2 in order to introduce the method prior to discussion. The reference regarding Hertzian contact mechanics from Latella et al. was determined extraneous and was removed.

Point 7:

A general note: The experimental methods, e.g., MFM or microscopy are used (applied) for

studies but not “performed”.

Response 7: This has been addressed throughout the body of the text.

Point 8:

Page 9, line 273

In the sentence beginning: “In this study, particular emphasis is placed on….” should be

probably “is devoted“ or “is paid” instead of “placed”.

Response 8: This sentence has been removed.

Point 9:

Lines 274-276

The sentence I cite: “For example, Latella et al. [36] showed that Vicker’s hardness deviated

from Hertzian approximations both as the load increased and porosity was incorporated in

alumina ceramics.” is unclear. Please, reformulate it.

Response 9: This reference and corresponding sentence has been removed and reformulated in an alternative manner.

Point 10:

In a similar way I can continue through the whole text of the revised paper. It is highly important to correct English and make the results and their discussion more transparent.

Response 10: The authors appreciate the insight into the weak English of this paper. As stated throughout prior responses, the entirety of the paper has been reviewed by another external native English speaker to improve the flow, increase coherency, and remove extraneous and convoluted text while improving the overall English. We hope that this revision addresses all the major points suggested by the reviewer and is closer to publication in the next revision.

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

The second time revised version of the paper

“Characterizing Changes in Grain Growth, Mechanical Properties, and Transformation Properties in Differently Sintered and Annealed Binder-Jet 3D Printed 14M Ni-Mn-Ga Magnetic Shape Memory Alloys“.

I have to state that a certain improvement of the paper was done. Nevertheless, I think that authors who contributed to the results and to the text, should avoid the incorrectness’s and errors. I do not believe that the English of this revised version was corrected by English native speaking colleagues as the authors stated. The paper contains still many incorrect expressions and whole sentences, unclear description of results being difficult to understand. I have mentioned only several of them below leading to my final conclusion “reject”.  

Section 2

Page 3, line 101: The polycrystalline ingots were produced using high-purity elemental Ni, Mn, and Ga powder. It means that Ga was in a form of powder. My question is what the forms of Ni and Mn were?

Line 103: Ni49.7± 0.5Mn 30.0±1.0 Ga 20.3±0.6 at.%. It should be better to write: Ni49.7± 0.5Mn 30.0±1.0 Ga 20.3±0.6 (at. %). Similarly, on page 2, line 87.  

Lines 126-127, line 131: “data” is plural; therefore, it should be: “Area detector raw data were extracted using in-house plotting software…”.

Page 5, Lines 193-197:

The sentence “To identify magnetic properties and characteristics of the bulk sample, vibrating sample magnetometry (VSM, Lakeshore series 7400 model) magnetization curves in an external magnetic field ± 1.5 T were analyzed to determine saturation magnetization and magnetic coercivity.” is not grammatically correct.

It should be: “To identify magnetic properties and characteristics of the bulk sample, vibrating sample magnetometry (VSM, Lakeshore series 7400 model) was used. The magnetization curves measured in an external magnetic field ± 1.5 T were analyzed to determine the saturation magnetization and magnetic coercivity.”

Lines 201-202: “Atomic force microscopy (AFM) and magnetic force microscopy (MFM) was performed …” it should be “were performed”.

Page 6, line 245: Table 1: The samples were: binder-jet printed Ni-Mn-Ga and not Ni-Mn-Ga binder jetted.

Page 7, lines 251-253: “Each Ω image was processed as described above, and distinct and coherent clusters in the area detector diffraction images.” This sentence is not clear.  Please correct.

“Through this procedure, nearly three times the number of distinct clusters were identified in the 1090 °C sintered samples compared to the 1080 °C sintered samples.” What did the authors want to say? It should be “three times higher number of...” or “triple number of …”

Page 8, 279-281: “Optical microscopy was applied to visually identify grain boundaries and distinguish individual grains on various cross-sectional areas of magnification identical for all samples (see Table 1 for average equivalent grain diameter).” It should be: ”Optical microscopy was applied to visually identify grain boundaries and to distinguish individual grains…..”

Page 9, lines 297-300: “Clearly, both grain size and porosity percentage can be adjusted through the introduction of a sintering step, however interplay between grain size and pore-size should be explored as a function of sintering temperature to further optimize MFIS.” It should be: “Clearly, both grain size and porosity percentage can be adjusted through the introduction of a sintering step, however, an interplay between grain-size and pore-size should be explored as a function of sintering temperature to further optimize MFIS.”

Lines 304-306: The author’s statement concerning the nanoindentation results is not exact. According to the values in Table 1 the sample sintered at 1080 °C and not treated has the lowest value of hardness contrary to both states of the next sample, sintered at 1090 °C and subsequently heated, which embody higher values of the hardness as well as of the reduced elastic moduli.

Lines 312-317: The following text “Increased hardness suggests that densification of the sample is resulting in a strengthening of the matrix, while opposing the effect of Hall-Petch. The results obtained here on the relative density are comparable to our previous paper [24] and suggest large densification is possible once the solidus temperature is achieved, and corresponding increase in relative density resulting from partial super-solidus liquid phase sintering was reflected in the reduced elastic modulus increase.” is not clear. Please rewrite.

Page 10, lines 352-355: I cite: “Further work by Kustov et al. [40] reported a significant softening (five to ten times lower) of the elastic modulus values depending on crystallographic direction and temperature for Ni-Mn-Ga. We note that nanoindentation had been performed in this study on mechanically ground, polished, and etched samples, through which minor surface stress and roughness likely accumulated.” The last sentence is not grammatically correct. Please rewrite.

Lines 352-362: I cite: “Further work by Kustov et al. [40] reported a significant softening (five to ten times lower) of the elastic modulus values depending on crystallographic direction and temperature for Ni-Mn-Ga. We note that nanoindentation had been performed in this study on mechanically ground, polished, and etched samples, through which minor surface stress 355 and roughness likely accumulated. Chmielus et al. [42] discussed surface mechanics and 356 twin boundary motion in Ni-Mn-Ga single crystals, where it was mentioned that mechan-357 ical polishing partially negates the surface hardening of cut samples and reduces twinning 358 stress. It should also be noted that the samples in this study have not been previously mechanically trained (see [21] for more details regarding the training process), further increasing failing to reduce the twinning stress in this study and reducing twin boundary motion compliancy.” My note concerns the usa of “in this study”:  the first one is probably connected with the Ref. [40], but it is not clear, to which studies the second and third ones are related. Moreover, the samples can be mechanically strained but not trained. Please reformulate these sentences to be clear and correct.

Lines 363-382: It is possible to understand what probably the authors wanted to express. Nevertheless, the description of results is absolutely incomprehensible from the technical and English viewpoints.     

Page 11, lines 384 – 410: A connection between nanoindentation testing and results of authors and those obtained by other authors is somewhat vague.

Page 13, line 435: How can the Curie temperature be determined by DSC measurements?

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