Shape Change and Crystal Orientation of B19 Martensite in Equiatomic TiPd Alloy by Isobaric Test
Round 1
Reviewer 1 Report
The present manuscript reports on shape change and crystal orientation of B19 martensite in equiatomic TiPd alloy by isobaric test. The manuscript has a meaningful results and discussion. The topic is technologically interested in the shape memory alloy field, and the results would be useful for processing. However, there are some questions to be addressed and some revision is required.
Comment:
1. In Fig.2 and 119 line in page 2, authors mentioned that shape of the crystal grain in old parent phases was columnar crystal in equiatomic TiPd alloy from the EBSD results of both 90 and 0 degree sample. However, Fig. (a-1) and (b-1) exhibited large difference in the grain size of parent phase, although both figures were obtained different cutting direction. Please describe why the samples show large difference of grain size in both directions.
2. In Fig. 3, the elastic strain before detwinning and yielding of both samples is so much higher than previous reported Ti-Pd HTSMA. Although it is enough to describe detwinning stress and yielding point, the authors have to support correct experimental data to avoid argument.
Author Response
Dear editor and reviewer 1,
Thank you very much for your valuable comments concerning our manuscript entitled “Shape change and crystal orientation of B19 martensite in equiatomic TiPd alloy by isobaric test”. We have studied your comments carefully and have made corrections, which we hope will meet with your approval. Revised portions are written in red.
[Reviewer #1 Comments]
The present manuscript reports on shape change and crystal orientation of B19 martensite in equiatomic TiPd alloy by isobaric test. The manuscript has a meaningful results and discussion. The topic is technologically interested in the shape memory alloy field, and the results would be useful for processing. However, there are some questions to be addressed and some revision is required.
[Comments]
(1) In Fig.2 and 119 line in page 2, authors mentioned that shape of the crystal grain in old parent phases was columnar crystal in equiatomic TiPd alloy from the EBSD results of both 90 and 0 degree sample. However, Fig. (a-1) and (b-1) exhibited large difference in the grain size of parent phase, although both figures were obtained different cutting direction. Please describe why the samples show large difference of grain size in both directions.
[Answer] As you pointed out, both samples have large difference of grain size. This may be due to the solidification from hearth side by arc-melting, leading to the long columnar crystals. We have therefore added the following sentence.
Page 3, Line 127: From these results, it was found that the shape of the crystal grains in old parent phases was the long columnar crystal according to the solidification from the hearth side by arc-melting,
[Comments]
(2) In Fig. 3, the elastic strain before detwinning and yielding of both samples is so much higher than previous reported Ti-Pd HTSMA. Although it is enough to describe detwinning stress and yielding point, the authors have to support correct experimental data to avoid argument.
[Answer] Firstly, based on your comments, we remade the stress-strain curve at room temperature by calibrating the compression test results. In our testing machine, the deformation strain always includes the deformation of sample holders or other parts of the testing machine. If the strain is directly measured by image analysis using CCD, the strain becomes half. However, the testing machine using in this study does not have CCD camera. So it is difficult to remove the strain obtained from the machine. Since the stress is considered to be accurate in this test and the purpose of the compression test is to know the detwinning stress and the yield stress, we think this data can be used in the paper. We added some explanation of detwinning stress and yielding stress clearly.
Page 2 Line 79: The strains of the samples were measured by the stroke of the compression testing machine.
Page 5 Line 159: In the martensitic phase at room temperature, only single yielding was observed. The detwinning and yield stress of TiPd in the previous study at 758 K [4, 5] were 249 and 617 MPa, respectively. Then, it is considered that the single yielding of 390 MPa obtained at room temperature is the detwinning stress. It seems that the yield point was not obtained due to brittleness of TiPd at room temperature because fracture occurred during increasing stress.
We greatly appreciate both your help and that of the referees concerning improvements to this paper. We hope that the revised manuscript is now suitable for publication.
Yours sincerely,
Mitsuhiro Matsuda
Reviewer 2 Report
The work try to investigate some aspect of correlation between texture and deformation due to thermoelastic martensitic transition. Neverthless the context of the investigation is not well proposed and the reference in the introduction are few, starting from the general description of SMA and NiTi alloys.
In the introduction please explain better what mean "strain recovery rate" in percent.
lines43-44: the shrinking phenomenon is related to reverse transition not to martensitic transformation
T Please correct thermoS-mechanical in thermo-mechanical
Lines 77-78 : the cooling and heating rate of the strain recovery test are very high! It is difficult to mantain precise the rate control of temperature and there are shift in the transition region. Do you have used some correction of the experimental data? Do the authors considered the thermal expansion of the equipment? Please explain
Moreover It could be interesting to see more cycles of strain recovery to better assest the transition and the related structure orientation
Figure 1: how the authors explain the crossing of the curves before and after the transition?
Please the authors explain better if the compression test and strain recovery test help to clarify the disagreement introduced in line 143-144
The EBSD measurement are able to see also the plastic deformation introduced with strain recovery measures?
Author Response
Dear editor and reviewer 2,
Thank you very much for your valuable comments concerning our manuscript entitled “Shape change and crystal orientation of B19 martensite in equiatomic TiPd alloy by isobaric test”. We have studied your comments carefully and have made corrections, which we hope will meet with your approval. Revised portions are written in red.
[Reviewer #2 Comments]
(1) The work try to investigate some aspect of correlation between texture and deformation due to thermoelastic martensitic transition. Neverthless the context of the investigation is not well proposed and the reference in the introduction are few, starting from the general description of SMA and NiTi alloys.
[Answer] Following your suggestion, in introduction, we have added the following sentence, and cited the paper.
Page 2, Line 51: It is well known that shape memory effects depend on the crystal orientations. Effect of texture orientation on shape memory strain and martensite deformation in TiNi alloys have been clarified so far [12-14]. In addition, it is reported that the texture orientation significantly influences the stress-strain curve and shape memory effects in Cu-based shape memory alloy [15,16].
References:
- Inoue; N. Miwa; N. Inakazu. Texture and shape memory strain in TiNi alloy sheets. Acta Materialia, 1996, 44(12), 4825–4834.[CrossRef]
- Liu; Z.L. Xie; J. Van Humbeeck; L. Delaey. Effect on texture orientation on the martensite deformation of NiTi shape memory alloy sheet. Acta Materrialia, 1999, 47(2), 645–660.[CrossRef]
- Otsuka; X. Ren. Physical metallurgy of Ti-Ni-based shape memory alloys. Progress in Materials Science, 2005, 50, 511-678. [CrossRef]
- C. Shu; K. Bhattacharya. The influence of texture on the shape memory effect in polycrystals. Acta Materialia, 1998, 46(15), 5457-5473. [CrossRef]
- Sutou; T. Omori; K. Yamauchi; N. Ono; R. Kainuma; K. Ishida. Effect of grain size and texture on pseudoelasticity in Cu-Al-Mn-based shape memory wire. Acta Materialia, 2005, 53, 4121-4133. [CrossRef]
[Comments]
(2) In the introduction please explain better what mean "strain recovery rate" in percent.
[Answer] Following your suggestion, we have added the following information.
Page 1 Line 34: It has been also reported that equiatomic TiPd has a shape recovery ratio of about 60%, using the following equation: shape recovery ratio = (L’’-L’)/ (L’-L0) x 100, where is L0: initial length of sample, L’: deformed sample length, and L’’: recovered sample length.
[Comments]
(3) ines43-44: the shrinking phenomenon is related to reverse transition not to martensitic transformation
[Answer] As you pointed out, the shape-recovery is originated from the reverse martensitic transformation. We have therefore modified the word.
Page 1 Line 44: There are some reports on the shape change due to the reverse martensitic transformation related to shape-recovery.
[Comments]
(4) T Please correct thermoS-mechanical in thermo-mechanical
[Answer] Sorry, as you pointed out, we have corrected the words.
[Comments]
(5) Lines 77-78 : the cooling and heating rate of the strain recovery test are very high! It is difficult to mantain precise the rate control of temperature and there are shift in the transition region. Do you have used some correction of the experimental data? Do the authors considered the thermal expansion of the equipment? Please explain
[Answer] The testing temperature in this study are accurately measured by a small thermocouple attached to the sample. Furthermore, in the isobaric test the shape change the sample is measured using a CCD camera. Therefore, we believe this rate is fine, and we have added the information concerning the equipment and method.
Page 2 Line 83: The strains of the samples were measured by direct observation using the CCD camera in the compression testing machine.
[Comments]
(6) Moreover It could be interesting to see more cycles of strain recovery to better assest the transition and the related structure orientation
[Answer] As you suggested, definitely, it could be very interesting to see more cycles of strain recovery. We will work on it in the future.
[Comments]
(7) Figure 1: how the authors explain the crossing of the curves before and after the transition?
[Answer] As you pointed out, the curves in Fig. 1 cross before and after transition. As a possibility, this may be to be due to thin sample thickness with 0.5 mm and the oxidation at high temperature. Therefore, we have added these comments.
Page 3 Line 102: The origin of the crossing the curves before and after the transformation on both samples may be originated from thin sample thickness with 0.5 mm and the oxidation at high temperature.
[Comments]
(8) Please the authors explain better if the compression test and strain recovery test help to clarify the disagreement introduced in line 143-144
[Answer] As you pointed out, transformation strain calculated by EBSD results shown in Table 1 is in disagreement with TMA measurement. As we described in the next sentences, it needs to perform more extensive EBSD measurements as much as possible to compare correctly transformation strain and TMA results. On the other hand, TMA results are in good agreement with transformation strain calculated by EBSD results of isobaric tested sample, as listed in Table 2.
[Comments]
(9) The EBSD measurement are able to see also the plastic deformation introduced with strain recovery measures?
[Answer] As you suggested, The EBSD measurement can estimate roughly the plastic strain; such as Kernel Average Misorientation: KAM value. This is now under study.
We greatly appreciate both your help and that of the referees concerning improvements to this paper. We hope that the revised manuscript is now suitable for publication.
Yours sincerely,
Mitsuhiro Matsuda
Round 2
Reviewer 2 Report
The work was significantly improved, even if I'm some doubt about the rate change in temperature during the strain recovery test...
The work is now suitable for publication
