{111}<110> Orientation Induced Anisotropy of Shape Memory Effect in NiTiNb Pipe Joints
Round 1
Reviewer 1 Report
The authors present the influence of {111}<110> texture on SME of plates and pipes in textured NiTiNb alloy samples. The experiments are systematic and the results include some novelty. However, the description how to obtain the texture is insufficient. According to manuscript, the final shape for test samples is rod, which has axial symmetry and usually only possesses one dimensional texture, such as <111> fiber to axial direction, remaining a freedom to radius directions. By forging, how did the authors fabricate the rod with the {111}<110> texture? The explanation in details is required.
P.8, Line 209-210,
“maybe including all kinds of orientations such as <111>, <110> and others, “ is not correct. The directions are restricted by a condition to be vertical to <110>. It should be “maybe including many orientations such as <111>, <110> and <001> with different recovery strains, “, for instance.
Author Response
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Author Response.pdf
Reviewer 2 Report
Manuscript Number: Manuscript ID: metals-801857
Review “{111}<110> orientation induced anisotropy of shape memory effect in NiTiNb pipe joints”
Manuscript
The authors investigate the impact of texture evolution on the recoverability in NiTiNb pipe joints and discuss the origin for SME anisotropy as a function of texture intensity.
In the reviewers opinion the authors did a good job in view of the experimental investigations. The current work does provide some new insights into the field of texture evolution, although the impact of texture or crystallographic orientation has been discussed in many studies dealing with NiTi based SMAs. Thus, the experimental investigations in this study somehow verify what is already known. In the reviewers opinion it is not surprising, that a stronger texture results in a higher strain anisotropy and that certain texture components or orientations features higher a reversibility. Somehow, this is the origin of the stress induced martensitic phase transformation.
Please consider revising the following points:
- In general, the syntax of the present manuscript needs to be revised carefully and many typos were found throughout the text.
- The authors show EBSD analysis in Figure 4. They show the IPF maps for ND and LD directions. Besides the he grain size and grain morphology significantly changes with deformation degree. The autors must take this evolution of grain size and morphology into account when discussing dislocation activity, reversibility and “stress plateau length” and maximal strain. Not only texture causes anisotropy but also grain morphology. The authors should discuss this in much more detail.
- The reviewer does not understand why the DSC results are presented in the current study. What is the relation to the overall story of the paper? Where can I see the reverse transformation temperature? Where is As and Af? Please mark the temperatures. What is the reason for the difference in the transformation temperatures of both conditions presented?
- What does an increase in anisotropy mean for a pipe coupling how do the texture components affect the application? The authors should provide for more experimental results on this. Did they do such tests, i.e. testing of the impact of different ED on the application in pipe joints?
The authors discuss the impact of texture in NiTiNb for pipe joint applications. However, they only show pseudoelastic testing. Since it is not surprising, that texture changes critical stresses and the overall recoverability in the reviewers opinion the authors should discuss the impact on the application side in much more detail. What is the impact on the real pipe joint coupling? They should provide for more experimental investigations on this.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
The paper deals with the analysis of NiTiNb pipe couplers with a particular focus on the effects of texture type and intensity. In particular, the anisotropies in the microstructure induced by material and ring processing are analyzed by different investigation techniques, including XRD and EBSD. The response at the macro scale, in terms of shape memory recovery capabilities, were also analyzed by measuring the inner diameter variations of SMA rings.
The paper is well written and organized and the topic is of interest to the SMA community and therefore I think that it deserve publication in Metals. However, I have to say that there is at least another paper (Tabessh et al., JIMMS 2017, DOI: 10.1177/1045389X17730922) where the effects of anisotropies in SMA couplers was analyzed, even if it is related to binary NiTi. The authors of this studies have found similar results in terms recoverable strain in the two investigated directions. In addition, there are also some recent studies related to the design and development of SMA couplers (both NiTiNb and NiTi) in the field of high energy particle physics (Niccoli et al. 2017, Mater Des, DOI: 10.1016/j.matdes.2016.11.101, Niccoli et al. 2017, J. Vac. Sci. Technol., DOI: 10.1116/1.4978044). I do think that these recent reports/studies could be considered in the revised manuscript.
Other minor comments are reported below:
- It is stated that stress-strain curves of Fig. 5 were obtained at -60°C. However, Fig. 7 shows that this temperature is within the thermal hysteresis of the material (Higher than Ms and lower than As). Therefore the microstructure could be either martensite or austenite at -60°C, depending on the previous temperature history. It seems that measurements were carried out after complete cooling
- It seems that the slope of the stress-strain curves in the nominal elastic regime is low (around 5 GPa). Even if this value is not exactely the Young’s modulus of martensite (different mechanisms are involved) this value is extremely low. I suggest the authors to re-check the raw data and/or to comment on this unusual result. It seems that the material has the same composition and a similar thermo-mechanical loading history of that analyzed by Liu and Zhao (Chinese Journal of Aeronautics, 2009, DOI: 10.1016/S1000-9361(08)60138-7) but these authors have found significantly higher moduli.
- The definition “martensite yield point” is not completely correct. In fact, it is just a nominal point as martensite yielding occurs even below this point. For the sake of completeness, I would add a comment to clarify this point.
- I would revise the sentences at lines 129-129 as the term “on the other hand” is repeated.
- At lines 208-210 it is stated that recovery strain of ring couplers in the preferred <110> direction is 8.4%. However, it is maybe valid for single crystal material. Please clarify this point.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
I am not satisfied with the answer from the authors. The more details on forging deformation and on the excision of samples from the forged rods should be described in Experimental Procedures. If excision direction from a rod is rotated 45 degree, for instance, in the axial direction, the texture would change!
Author Response
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Reviewer 2 Report
The authors clearly improved the quality of the paper. However, providing for a direct evidence of an improved application of the textured pipe joints would clearly further improve the results of the paper.
However, I can accept the paper in its current form.
Author Response
Honorable Editors and reviewer 2,
Thanks to the reviewer's positive comment and valuable suggestion. We are very sorry that we failed to provide a direct evidence for an improved application of the textured pipe joints due to the incompleteness of the experimental data obtained so far. Meanwhile, it is too hasty to supplement the data in a short time now. But we are going to complete the corresponding experiments in our future work. We hope it would not affect the value of the article. Thanks again for your valuable suggestion.
Best regards,
Shuke Huang
