Low-Temperature Induced Martensitic Transformation Enhancing Mechanical Properties of Metastable Fe-Ni-P Alloy
Round 1
Reviewer 1 Report
The manuscript titled “Low-temperature Induced Martensitic Transformation Enhancing Mechanical Properties of Metastable Fe-Ni-P Alloy” is presenting investigations on the effect of phosphorous doping of a Fe-Ni alloy, followed by heat treatment, on the mechanical properties and structural development.
This paper is not recommended for publication in the current state.
Following are only some of the issues in the manuscript which are to be seriously addressed:
1. The English language and grammar used in the present manuscript is generally poor. There are plenty of instances where mistakes, misspelled words and/or poorly chosen words (ambiguous) are present. I strongly suggest that the paper should be proofread and double-checked concerning the spelling and phrasing.
2. The experimental details of this research are not clearly explained. In my opinion, the experimental protocol is not reproducible, both regarding the alloy manufacture and the thermal treatments. Was the 875 C temperature used for the alloy manufacture of for the thermal treatment? It is not clear. If the alloy is obtained at 875C, is it sintering or melting?
3. The explanation regarding the metastable nature of the gamma-FeNiP alloy is not clear. Why is it considered metastable?
4. A surface chemical composition mapping would complement the discussion regarding the structure.
5. Even if the readers are specialists, there should be an explanation for each acronym. I am assuming that on row 122 the correct form is BCC, not BBC.
6. The XRD data should be further analyzed, especially considering the discussions related to distortions of the crystalline lattice, which can be inferred from peak shifts on the diffraction patterns.
Author Response
Response to Reviewer 1 Comments
Thank you for your comments concerning our manuscript entitled “Low-temperature Induced Martensitic Transformation Enhancing Mechanical Properties of Metastable Fe-Ni-P Alloy” (metals-538879). Those comments and advises are all valuable and useful for revising and improving this paper, as well as have important guiding significance to our researches. We have studied comments carefully and have made corrections, including the reviewer’s comments and the inaccurate grammar throughout the whole paper. Revised portion are highlighted using yellow background in the revised manuscript. We hope meet with your approval.
Point 1: The English language and grammar used in the present manuscript is generally poor. There are plenty of instances where mistakes, misspelled words and/or poorly chosen words (ambiguous) are present. I strongly suggest that the paper should be proofread and double-checked concerning the spelling and phrasing.
Response 1: Thank you for your comment. We have improved the English expression and corrected inaccurate grammar throughout the whole paper. Some misspelled and inappropriate words have also been avoided. I hope that the English language in this revised manuscript is readable enough to meet your requirement.
Point 2: The experimental details of this research are not clearly explained. In my opinion, the experimental protocol is not reproducible, both regarding the alloy manufacture and the thermal treatments. Was the 875 C temperature used for the alloy manufacture of for the thermal treatment? It is not clear. If the alloy is obtained at 875C, is it sintering or melting?
Response 2: Thank you for your comment. Since we submitted this manuscript as a short communication, we simplified the description of the Materials and Methods section. In the revised manuscript, more details of this part are added. In addition, the 875oC temperature is used for the alloy manufacture (sintering) of Fe-Ni-P alloy. In this work, the sintering process can be identified as semi-liquid phase sintering. This “liquid” does not mean the melting of alloy. This temperature is at the L+α dual-phase region of Ni-P phase diagram. In Fe-Ni-P composite powder, the component with lower melting point (Ni-P plating) is semi-liquid, but the matrix (Fe) is still solid at 875oC temperature.
Point 3: The explanation regarding the metastable nature of the gamma-FeNiP alloy is not clear. Why is it considered metastable?
Response 3: The Fe-Ni alloy is mainly composed of α-phase and γ-phase. When the Ni content in alloy is within a certain range (about 30-35 wt.%), the α-phase will be exactly all converted into the γ-phase (critical state). This γ-phase in the Fe-Ni alloy is therefore unstable, and induced martensitic transformation can occur at a low temperature or under an external force. This unstable structure in Fe-Ni alloy is known as metastable γ-phase. For instance, martensite is produced after quenching of steels, and a small amount of residual austenite is also produced. This residual austenite is metastable and undergoes martensitic transformation during cryogenic treatment. The phase structure of Fe-Ni-P alloys herein at room temperature mainly consists of this γ-phase in critical state. As a ferrite stabilizer, phosphorus will increase the destabilization of this γ-(Fe-Ni-P) phase when it is in a solid solution state and causes lattice distortion of the γ-phase. Martensitic transformation in this γ-(Fe-Ni-P) phase is more prone to occur at a low temperature condition. Thus, the Fe-Ni-P alloy in current work is considered to be metastable. Relevant description has been added in the revised manuscript.
Point 4: A surface chemical composition mapping would complement the discussion regarding the structure.
Response 4: Thank you for your comment. We have conducted the EDS mapping experiments on those γ-(Fe-Ni-P) alloys before/after treatment. Relevant discussion has also been given in the revised manuscript.
Point 5: Even if the readers are specialists, there should be an explanation for each acronym. I am assuming that on row 122 the correct form is BCC, not BBC.
Response 5: We have added a short explanation in the place where each acronym first appears. We have corrected this mistake, as well as other misspelled words, in the revised manuscript.
Point 6: The XRD data should be further analyzed, especially considering the discussions related to distortions of the crystalline lattice, which can be inferred from peak shifts on the diffraction patterns.
Response 6: Thank you for your advice. We have made relevant analysis on XRD results in the revised manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is an interesting and novel study and has merit in being published. I would recommend the authors to look at the after deformation microstructure.
Can authors comment on the increase in slope in the strain hardening rate vs strain plot (after 10% strain in 20 and -20 C).
Did the authors notice twinning of gamma phase after deformation? or transformation to martensite?
Did the authors observe phosphorus enrichment on the grain boundaries?
The following details should be added to the manuscript:
error margins on the hardness values.
how many specimens/locations were tested for compression/hardness values.
Instruments used to conduct mechanical property assessments
the dimensions of the SPS processed materials.
Author Response
Response to Reviewer 2 Comments
Thank you for your comments concerning our manuscript entitled “Low-temperature Induced Martensitic Transformation Enhancing Mechanical Properties of Metastable Fe-Ni-P Alloy” (metals-538879). Those comments and advises are all valuable and useful for revising and improving this paper, as well as have important guiding significance to our researches. We have studied comments carefully and have made corrections, including the reviewer’s comments and the inaccurate grammar throughout the whole paper. Revised portion are highlighted using yellow background in the revised manuscript. We hope meet with your approval.
Point 1: Can authors comment on the increase in slope in the strain hardening rate vs strain plot (after 10% strain in 20 and -20 C).
Response 1: Thank you for your comment. The increase in the strain hardening rate is due to the working hardening and the martensitic transformation during the plastic deformation of Fe-Ni-P alloy. In alloys treated at 20oC and -20oC, highly plastic γ-phase has a high proportion in these alloys. This phosphorus-contained γ-phase has a considerable strength and better plastic deformation ability. It can also be strengthened by deformation-induced martensitic transformation. But in alloy treated at -50oC, α-phase has been the dominated phase in alloy, which leads to these features not obvious. Thus, there is an increase in strain hardening rates of alloys treated at 20oC and -20oC. Relevant discussion has been added to the revised manuscript.
Point 2: Did the authors notice twinning of gamma phase after deformation? Or transformation to martensite?
Response 2: Thank you for your comment. The deformation-induced martensitic transformation is observed during the plastic deformation of Fe-Ni-P alloys. We have found that the phase structure of alloys can transform to martensite and twinning after deformation, and the deformation behavior of Fe-Ni-P alloys can change. We have put an emphasis on this topic in our recent research.
Point 3: Did the authors observe phosphorus enrichment on the grain boundaries?
Response 3: Thank you for your comment. We have obtained the surface composition distributions of Fe-Ni-P alloys before/after cryogenic treatment through EDS mapping (shown in Figure 3 in the revised manuscript). The phosphorus enrichment on the grain boundaries is not observed and phosphorus is uniformly distributed in the alloy matrix in a solid solution state.
Point 4: The following details should be added to the manuscript:
error margins on the hardness values.
how many specimens/locations were tested for compression/hardness values.
Instruments used to conduct mechanical property assessments
the dimensions of the SPS processed materials.
Response 4: Thank you for your comment. We have added these details in the relevant parts of the revised manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I consider that the manuscript entitled “Low-temperature Induced Martensitic Transformation Enhancing Mechanical Properties of Metastable Fe-Ni-P Alloy” has been improved since the previous review and now warrants publication in Metals.
