Precipitation Behavior of Orthorhombic Phase in Ti-22Al-25Nb Alloy during Slow Cooling Aging Treatment and Its Effect on Tensile Properties
, Xiaofei Chen 1, Qin Xu 1, Shuaijin Zhang 3, Hongchao Kou 1 and Jinshan Li 1Round 1
Reviewer 1 Report
The authors have investigated the effect of heat treatment parameters on the microstructures and tensile properties of Ti-22Al-25Nb and clarified the mechanism of O phase formation. The manuscript has a high quality of presentation, however there are two minor revisions:
- Table 1 show the chemical composition proposed or obtained? How they measured the chemical composition of the alloy?
- Have to decide if the affiliation of the authors is written with numbers or with letters.
Author Response
Dear Reviewer,
Firstly, we would like to express our sincere appreciation to you for carefully reviewing our manuscript. Your suggestions and comments have made our manuscript clearer and more concise. Our reply to each comment is listed below. The comments are in Italic font, and our replies are
shown in bold font.
Reviewer 1’s comments:
- Table 1 show the chemical composition proposed or obtained? How they measured the chemical composition of the alloy?
- Have to decide if the affiliation of the authors is written with numbers or with letters.
Reply: Thank you very much for your careful reading.
- The chemical composition of the alloy was measured by Electron - coupled plasma atomic emission spectrometry (ICP-AES).
- We have just corrected the mistakes in the manuscript and the affiliation of the authors is written with numbers.
We appreciate for Editors/Reviewers' warm work earnestly and hope that the correction will meet with approval.
Sincerely
Bin Tang on behalf of all co-authors
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors of the manuscript studded the effect of heat treatment parameters on the precipitation behavior of orthorhombic Ti2alNb phase (O phase) during the slow cooling aging treatments of a Ti-22Al-25Nb alloy and a relationship between the content of the O phase and tensile properties of the alloy. X-ray diffraction method as well as the optical microscopy and scanning electron microscope equipped with EBSD system were used for microstructure characterization. Mechanical properties were studded by tensile tests at room temperature. It were found correlations between volume fraction/precipitation behavior/nucleation mechanism of the O phase and temperature/time of aging as well as correlation between condition of the O phase precipitation and the tensile properties of the alloy. In my opinion the manuscript is original, provides interesting results, is written carefully, clearly and in good English. I recommend publishing this manuscript after minor corrections.
- Please specify the sentence “the level of technology maturity of Ti2AlNb based alloys only reaches 3~5…” of what? (line 46).
- What is the method of chemical composition measurement and its error (table 1)?
- Authors state that the globular O phase only exists at grain boundaries when the aging temperature reaches 950°C (line 114). What is the grain size of this phase and what are the small precipitates observed inside grains of the matrix in Fig.4c, which are close to size of the O phase?
- In my opinion, the Fig 8a) and 8b) do not represent the inverse pole figures. These are orientation maps. Please correct it and present the IPF color map for each phase.
- Please take into account, that the abbreviation OLGB entered in line 5, is later not mentioned either in the figures or in the text.
Author Response
Dear Reviewer,
Firstly, we would like to express our sincere appreciation to you for carefully reviewing our manuscript. Your suggestions and comments have made our manuscript clearer and more concise. Our reply to each comment is listed below. The comments are in Italic font, and our replies are
shown in bold font.
Reviewer 2’s comments:
- Please specify the sentence “the level of technology maturity of Ti2AlNb based alloys only reaches 3~5…” of what? (line 46).
- What is the method of chemical composition measurement and its error (table 1)?
3.ï‚· Authors state that the globular O phase only exists at grain boundaries when the aging temperature reaches 950°C (line 114). What is the grain size of this phase and what are the small precipitates observed inside grains of the matrix in Fig.4c, which are close to size of the O phase?
- In my opinion, the Fig 8a) and 8b) do not represent the inverse pole figures. These are orientation maps. Please correct it and present the IPF color map for each phase.
- Please take into account, that the abbreviation OLGB entered in line 5, is later not mentioned either in the figures or in the text.
Reply: Thank you very much for your valuable advice.
- We have changed the manuscript to “the level of thermomechanical processing maturity of Ti2AlNb based alloys only reaches 3~5 till date.” The meaning of this sentence is that the thermomechanical processing of Ti2AlNb based alloys is immature.
- The chemical composition of the alloy was measured by Electron - coupled plasma atomic emission spectrometry (ICP-AES).
- The size of O phase which Precipitates at 950°C is about 5μm. For Figure 4c, we have changed to a clearer picture.
Fig. 4 Microstructure of Ti-22Al-25Nb alloy held for 30 min at different temperatures. (a) 900°C, (b) 930°C, (c) 950°C, (d) Statistical results for the volume fraction of O phase.
- In my opinion, the Fig 8a) and 8b) revealedthat some O phase variants nucleate in the vicinity of OGB. Different orientations represent different O phase variants.
Fig. 8 The IPF maps (a) of O phase and (b) of B2 phase. (c) The {110}, <111> pole figures of B2 phase and the {001}, <110> pole figures of O variants
- We have changed the manuscript to “The O phase precipitated from the grain boundaries is named OGB. OG1, OG2, and OG3 refer to the OGB. Also, it was found that some O phase variants nucleate in the vicinity of OGB and then grow into the β grains. O1 is a variant nucleated at OG1, and O2, O3 are the variants nucleated at OG2.”
We appreciate for Editors/Reviewers' warm work earnestly and hope that the correction will meet with approval.
Sincerely
Bin Tang on behalf of all co-authors
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors presented new results regarding the nucleation mechanism of O phase and its effect on tensile properties of the Ti-2 22Al-25Nb alloy.
The Conclusion part can be improved, in the present version it seems short and similar to the scientific report.
Author Response
Dear Reviewer,
Firstly, we would like to express our sincere appreciation to you for carefully reviewing our manuscript. Your suggestions and comments have made our manuscript clearer and more concise. Our reply to each comment is listed below. The comments are in Italic font, and our replies are
shown in bold font.
Reviewer 3’s comments:
The Conclusion part can be improved, in the present version it seems short and similar to the scientific report.
Reply: Thank you very much for your comments.
We have further improved the conclusion. The conclusions are listed below.
- Conclusion
(1) The acicular O phase precipitated from both the grain boundaries and the intragranular when aging at 900°C. Increase the temperature to 930°C, the acicular O phase tends to precipitate from the grain boundaries. In addition, the average size of O phase at 930°C is larger than that at 900°C. When aging at 950°C, only a few globular O phases could be found at grain boundaries.
(2) Under the condition of B2 slow cooling aging, there are two modes of nucleation mechanism of O phase from grain boundaries, sympathetic nucleation, and interface instability nucleation.
(3) With the increase of aging temperature, the volume fraction of O phase decreased and the strength of the alloy increased. The strength of the alloy decreases with the increase of aging time when ageing at 900°C and 930°C. When ageing at 950°C, strength experiences a first increase then decrease process. The reasonable match between strength could be obtained at 950°C /1h.
We appreciate for Editors/Reviewers' warm work earnestly and hope that the correction will meet with approval.
Sincerely
Bin Tang on behalf of all co-authors
Author Response File: Author Response.pdf
