Effect of Void Defects on the Indentation Behavior of Ni/Ni3Al Crystal
David Singh
Round 1
Reviewer 1 Report
The authors report molecular dynamics simulation of a Ni/Ni3Al interface with void under an indenter. The results may be publishable, but some improvements are needed.
They have a long and very generic broad introduction that seems repetitive of literature and does not get to the essential point: how important are voids in practice for superalloys? what is the state of the art in producing material without voids? what is known about the effect of voids on mechanical properties from previous experiments and theory? These issues should be the subject of the introduction. The review type on general aspects of superalloys could be shortened a lot and reduced to perhaps reference to a few review articles or books on the subject.
The importance of the Ni/Ni3Al interface as opposed to for example interfaces of ordered and disordered Ni3Al should be discussed better.
Details about the model construction and why they choose the particular interface orientation should be provided.
Some more information about the EAM model for Ni3Al should be provided along with its reliability, e.g. for predicting mechanical properties of pure Ni3Al etc.
The English is generally acceptable but there are minor problems. Please proof read it.
Author Response
Dear Editor and Reviewers,
Re: Manuscript Revision for Nanomaterials. (Manuscript ID: nanomaterials-2453852) –Effect of void defect on the indentation behavior of Ni/Ni3Al crystal
Thank you for forwarding the reviewers’ comments on the above manuscript, which are valuable for our revision. We have carefully revised the manuscript accordingly (the revised text is in red color). The attached report provides the details of the revision and the responses to the reviewers’ comments.
We hope that the revised manuscript is now satisfactory for publication in Nanomaterials. Thank you very much for your kind assistance.
With best regards!
Sincerely yours,
Kun Sun (Corresponding author)
Revisions and responses to the comments of the reviewers (nanomaterials-2453852)
Reviewers' comments:
Reviewer #1: The authors report molecular dynamics simulation of a Ni/Ni3Al interface with void under an indenter. The results may be publishable, but some improvements are needed.
Comment: They have a long and very generic broad introduction that seems repetitive of literature and does not get to the essential point: how important are voids in practice for superalloys? what is the state of the art in producing material without voids? what is known about the effect of voids on mechanical properties from previous experiments and theory? These issues should be the subject of the introduction. The review type on general aspects of superalloys could be shortened a lot and reduced to perhaps reference to a few review articles or books on the subject.
Response: Thank you for your advice and comments.
The geometrical stress concentrations created by microstructure defects, like microvoids and microcracks, play a significant role in the localization of the structural response of Ni-based superalloys. Liu et al. (C.P. Liu, X.N. Zhang, L. Ge, S.H. Liu, C.Y. Wang, T. Yu, Y.F. Zhang, Z. Zhang, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 682 (2017) 90-97.) observe that the microvoids are often formed at the intersection of two sets of slipping dislocations. Yu et al. (Z.Y. Yu, X.Z. Wang, Z.F. Yue, X.M. Wang, Mater. Sci. Eng. A-Struct. Mater. Prop. Microstruct. Process., 697 (2017) 126-131.) find that microvoids caused local stress concentration so as to the crack propagation, finally resulting in the fast fracture. Thus, in this work, we study the effect of void defect on the indentation behavior of Ni/Ni3Al crystal.
In this paper, the state of the art in producing material without voids is not considered for the time being. Your opinion is quite good. In the following work, we will consider more about this aspect.
The void defects unavoidably introduce during IN 718 superalloy preparation, which not only affected the mechanic properties but also changed the deformation mechanism. Both experimental and simulation have been employed to reveal the essence of the effect of voids on the mechanical properties of IN 718. Wang et al. (J.P. Wang, J.W. Liang, Z.X. Wen, Z.F. Yue, Comput. Mater. Sci., 160 (2019) 245-255.) report the dislocations initially nucleate on the surface of void and the mechanical properties are controlled by the interaction between void and interface. Shang et al. (J. Shang, F. Yang, C. Li, N. Wei, X. Tan, Comput. Mater. Sci., 148 (2018) 200-206.) discover the interaction between void and interface trigger the varying dislocation nucleation and plastic deformation patterns. Cui et al. (C. Cui, X.G. Gong, L.J. Chen, W.W. Xu, L.J. Chen, Int. J. Mech. Sci., 216 (2022) 10.) find the slipped dislocation can swimmingly enter into the γ′ phase along the periphery of void so as to cause the reduction of mechanical strength.
The above questions have been revised in the manuscript.
Comment: The importance of the Ni/Ni3Al interface as opposed to for example interfaces of ordered and disordered Ni3Al should be discussed better.
Response: Thank you for your advice and comments.
In this paper, the effect of voids is major investigated, so the ordered and disordered of Ni/Ni3Al interface are less discussed. This will be the focus of our next work.
Comment: Details about the model construction and why they choose the particular interface orientation should be provided.
Response: Thank you for your advice and comments.
To establish the initial models, the Swiss-army knife of atomic simulation (ATOMSK) (P. Hirel, Comput. Phys. Commun., 197 (2015) 212-219.) is employed to merge the γ phase and γ′ phase together along the Y-axis. Furthermore, large amounts of experiments and theoretical analysis show that the γ-Ni and γ′-Ni3Al are usually have a interface dependency along the direction of (001)γ || (001) γ′ (T.M. Pollock, A.S. Argon, Acta Metall. Mater., 42 (1994) 1859-1874.; X.L. Liu, S.L. Shang, Y.J. Hu, Y. Wang, Y. Du, Z.K. Liu, Mater. Des., 133 (2017) 39-46.).
And we have added this information to the manuscript.
Comment: Some more information about the EAM model for Ni3Al should be provided along with its reliability, e.g. for predicting mechanical properties of pure Ni3Al etc.
Response: Thank you for your advice and comments.
In this work, the EAM potential (NiAl_Mishin_2004.eam.alloy) is suitable for Ni-Al alloy system proposed by Mishin et al. and it is widely employed to explore the mechanical properties of Ni3Al single and Ni/Ni3Al composite system. Therefore, NiAl_Mishin_2004.eam.alloy potential is reliability for the Ni3Al and Ni/Ni3Al system (J.J. Zhou, Y.L. He, J.C. Shen, F.A. Essa, J.G. Yu, Nanotechnology, 33 (2022) 10.; J. Xiong, Y.X. Zhu, Z.H. Li, M.S. Huang, Acta Mech. Solida Sin., 30 (2017) 345-353.; R. Seymour, A. Hemeryck, K. Nomura, W.Q. Wang, R.K. Kalia, A. Nakano, P. Vashishta, Appl. Phys. Lett., 104 (2014) 4.).
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In their paper "Effect of void defect on the indentation behavior ...", Longlong Yang and Kun Sun computationally explore mechanical properties and dislocations for indented Ni/Ni3Al with a void. The methodology of simulating the behavior of the model system seems scientifically sound, and results depending on void size and position are definitely of interest for the readers of "nanomaterials".
Some minor points have to be corrected, before the paper is ready for publication.
1. line 104: "... system is controlled by at 0.1 K" - please rephrase
2. Figure 2: points A and B should be explained in the figure caption.
3. line 128: How exactly can one see that "the penetration depth and load first increase and then decrease as the void radius increases." in Figure 2?
4. Table 1: It seems that the number of digits is too large for all calculated quantities.
5. line 198: there seem to be no yellow lines in the figure.
6. Figure 5: "v_ams" is not defined.
7. Figure 6: How are the points C, D, E defined? How can one see they there the curves begin to diverge???
8. Table 2: same as Table 1
9. Figure 7: The penetration depth is constant for most part of (b)?
10. Line 264, 265: Too many digits for the percentages.
11. Line 266: rephrase the part "... so the atomic structure incompleteness and chaos under the indenter."
Some sentences have to be rephrased.
Author Response
Dear Editor and Reviewers,
Re: Manuscript Revision for Nanomaterials. (Manuscript ID: nanomaterials-2453852) –Effect of void defect on the indentation behavior of Ni/Ni3Al crystal
Thank you for forwarding the reviewers’ comments on the above manuscript, which are valuable for our revision. We have carefully revised the manuscript accordingly (the revised text is in red color). The attached report provides the details of the revision and the responses to the reviewers’ comments.
We hope that the revised manuscript is now satisfactory for publication in Nanomaterials. Thank you very much for your kind assistance.
With best regards!
Sincerely yours,
Kun Sun (Corresponding author)
Revisions and responses to the comments of the reviewers (nanomaterials-2453852)
Reviewers' comments:
Reviewer #1: In their paper "Effect of void defect on the indentation behavior ...", Longlong Yang and Kun Sun computationally explore mechanical properties and dislocations for indented Ni/Ni3Al with a void. The methodology of simulating the behavior of the model system seems scientifically sound, and results depending on void size and position are definitely of interest for the readers of "nanomaterials".
Some minor points have to be corrected, before the paper is ready for publication.
(1) Comment: line 104: "... system is controlled by at 0.1 K" - please rephrase
Response: Thank you for your advice and comments.
line 104: "... system is controlled by at 0.1 K" has been replaced by “ In addition, in the simulation of exploring the effect of void location and radii, the MD simulations are carried out at 0.1 K to avoid the effect of thermal fluctuation on dislocation processes.”
(2) Comment: Figure 2: points A and B should be explained in the figure caption.
Response: Thank you for your advice and comments.
We have explained the points A and B in the figure caption. “A point represents the yield depth and B point represents the point at an indentation depth of 2 nm.”
(3) Comment: line 128: How exactly can one see that "the penetration depth and load first increase and then decrease as the void radius increases." in Figure 2?
Response: Thank you for your advice and comments.
Fig.2 shows the trend of depth and load of pop-in change with the increase of void radius, and Table 1 shows the specific value. Therefore, in the manuscript, I revised this sentence to “as shown in Fig.2 point A and Table 1, the depth and load of pop-in first increase and then decrease as the void radius increases.”
(4) Comment: Table 1: It seems that the number of digits is too large for all calculated quantities.
Response: Thank you for your advice and comments.
We have revised the data in Table 1 and Table 2 to keep two digits.
(5) Comment: line 198: there seem to be no yellow lines in the figure.
Response: Thank you for your advice and comments.
As shown in Fig.1, there are fewer dislocation lines of the yellow line (Hirth dislocation) in the MD models at the penetration depth of 2 nm. And the dislocation length of Hirth dislocation are 143.09 Å, 35.53 Å, 34.91 Å, 0 Å, 17.15 Å, 30.66 Å, respectively. On the other hand, it is difficult to observe the Hirth dislocation line due to the different observation positions. Thus, although the yellow lines (Hirth dislocation) are not directly observable in Fig. 4 of the manuscript, they are present in the MD models.
The Hirth dislocation in MD models.
(6) Comment: Figure 5: "v_ams" is not defined.
Response: Thank you for your advice and comments.
In Fig.5, the “v_ams” is not defined and we have removed it as shown in the below Figure.
Cross-section view of von-Mises stresses at penetration depth h=2 nm
(7) Comment: Figure 6: How are the points C, D, E defined? How can one see they there the curves begin to diverge?
Response: Thank you for your advice and comments.
In Fig.6, the points C, D and E are defined based on the appearance of an evident distinction in flow stress during the plastic deformation stage in the load-depth curve. These points show the influence of different void distances on the flow stress in the plastic deformation stage.
(8) Comment: Table 2: same as Table 1
Response: Thank you for your advice and comments.
Table 1 and Table 2 are not the same. Although MD calculated the elastic parameters as the same, Table 1 is the different radii of the void, and Table 2 is the different distances of the void.
(9) Comment: Figure 7: The penetration depth is constant for most part of (b)?
Response: Thank you for your advice and comments.
This is a mistake in Fig.7 (b). We have revised the manuscript and the new Figure as shown below.
(10) Comment: Line 264, 265: Too many digits for the percentages.
Response: Thank you for your advice and comments.
According to your comment, we have revised the manuscript.
(11) Comment: Line 266: rephrase the part "... so the atomic structure incompleteness and chaos under the indenter."
Response: Thank you for your advice and comments.
According to your comment, we have rephrased the part to “…that is, before penetrating into the substrate, some regions of the model below the indenter have appeared incomplete and chaotic atomic structure.”
Author Response File: Author Response.pdf
Reviewer 3 Report
The work of Sun et al. is devoted to the computetional investigation of the effect of void defect in Ni/Ni3Al crystal on its mechanical properties.The work is undoubtedly relevant in view of the fact that such materials have superior mechanical properties. The work can be accepted for publication after answering the following questions:
1) as a model, the authors chose a crystal in which the phase boundary lies in the xz plane.Why is this orientation chosen, and not the orientation with the phase boundary oriented parallel to the xy plane?Is there any practical rationale for this?
2) please provide a reference for the value used in the article for the constant K of Equation 3
3) line 127, the authors write:"Firstly, about the pop-in at the load-depth curve, as shown 127 in Fig.2 point A, the penetration depth and load first increase and then decrease as the void radius increases".This is true if the results for a void-free sample are not taken into account; however, if a void-free sample is concidered as a sample with a void of the smallest radius (i.e. R=0), then this statement no longer describes the data obtained.
4) fig.2. Authors should define point A on the curve
5) fig.3. as I understand it, the inserts in the figures are a zoom of certain areas.For greater clarity, it is worth indicating which zones were zoomed.So, for example, for a and b, the appearance of the red areas in the inserts does not at all correlate with their appearance in the main picture.What is it connected with?
6) Fig. 6 and line 220. The letter D, which denotes a certain point on the graph, coincides with the parameter D, which determines the position of the empty volume in the sample.the latter in some cases is written in italics (in the text after line 210), and in some cases it is not (up to line 210 and in Figure 6)
7) it is better to use the same units in the text of the article. At the moment, for example, there are both 20A and 2nm values
Author Response
Dear Editor and Reviewers,
Re: Manuscript Revision for Nanomaterials. (Manuscript ID: nanomaterials-2453852) –Effect of void defect on the indentation behavior of Ni/Ni3Al crystal
Thank you for forwarding the reviewers’ comments on the above manuscript, which are valuable for our revision. We have carefully revised the manuscript accordingly (the revised text is in red color). The attached report provides the details of the revision and the responses to the reviewers’ comments.
We hope that the revised manuscript is now satisfactory for publication in Nanomaterials. Thank you very much for your kind assistance.
With best regards!
Sincerely yours,
Kun Sun (Corresponding author)
Revisions and responses to the comments of the reviewers (nanomaterials-2453852)
Reviewers' comments:
Reviewer #3: The work of Sun et al. is devoted to the computational investigation of the effect of void defect in Ni/Ni3Al crystal on its mechanical properties. The work is undoubtedly relevant in view of the fact that such materials have superior mechanical properties. The work can be accepted for publication after answering the following questions:
1) As a model, the authors chose a crystal in which the phase boundary lies in the xz plane. Why is this orientation chosen, and not the orientation with the phase boundary oriented parallel to the xy plane? Is there any practical rationale for this?
Response: Thank you for your advice and comments.
From previous experiments, it can be known that the organizational configuration of the γ/γ′ phase is shown in Figure (a) (Q.Q. Ding, S.Z. Li, L.Q. Chen, X.D. Han, Z. Zhang, Q. Yu, J.X. Li, Acta Mater., 154 (2018) 137-146.). Due to a strongly anisotropic lattice misfit between the γ precipitate phase and γ′ precipitate phase, the γ/γ′ phase exhibit pronounced lath-like microstructure. Voids are usually formed at the phase boundary, thus in this work, void is preset at the phase boundary, and the indenter penetrates into the substrate at the phase boundary. The phase boundary is parallel to the XY plane, that is, various preset void and penetration locations. Which is the key consideration direction of next work.
2) Please provide a reference for the value used in the article for the constant K of Equation 3
Response: Thank you for your advice and comments.
We have provided references for the value for the constant K of Eq.3 in the manuscript.
H.T. Luu, S.L. Dang, T.V. Hoang, N. Gunkelmann, Appl. Surf. Sci., 551 (2021) 13.
- Ziegenhain, H.M. Urbassek, A. Hartmaier, J. Appl. Phys., 107 (2010) 6.
3) line 127, the authors write:"Firstly, about the pop-in at the load-depth curve, as shown 127 in Fig.2 point A, the penetration depth and load first increase and then decrease as the void radius increases".This is true if the results for a void-free sample are not taken into account; however, if a void-free sample is concidered as a sample with a void of the smallest radius (i.e. R=0), then this statement no longer describes the data obtained.
Response: Thank you for your advice and comments.
In this work, the void-free model is mainly used as a reference, and the mechanical properties of the void-free model are not involved in the analysis and discussion. It is an oversight in the discussion. We have modified it in the manuscript. “Fig.2 point A, the depth and load of pop-in first increase and then decrease as the void radius increases, regardless of the void-free model.”
4) Fig.2. Authors should define point A on the curve
Response: Thank you for your advice and comments.
We have explained the points A and B in the figure caption. “A point represents the yield depth and B point represents the point at an indentation depth of 2 nm.”
5) Fig.3. as I understand it, the inserts in the figures are a zoom of certain areas. For greater clarity, it is worth indicating which zones were zoomed. So, for example, for a and b, the appearance of the red areas in the inserts does not at all correlate with their appearance in the main picture. What is it connected with?
Response: Thank you for your advice and comments.
In Fig.3, the inserts in the Fig. 3 (a) and (b) are the zoomed of the dislocation embryo region, but the angle of view is adjusted. To avoid misunderstanding, we have modified Fig.3, and the new figure is shown in below.
6) Fig. 6 and line 220. The letter D, which denotes a certain point on the graph, coincides with the parameter D, which determines the position of the empty volume in the sample. The latter in some cases is written in italics (in the text after line 210), and in some cases it is not (up to line 210 and in Figure 6)
Response: Thank you for your advice and comments.
The letter D on the graph coincides with the parameter D, thus the certain points in Fig.6 have been modified “….in points C, E and F in Fig.6 ”. And all the parameter D have been written in italics in the manuscript.
7) It is better to use the same units in the text of the article. At the moment, for example, there are both 20A and 2nm values
Response: Thank you for your advice and comments.
In this work, the units of indentation depth used to calculate Young’s modulus according to Hertzian contact model is nm, so there are two units Å and nm. We have already unified the units to Å in the manuscript.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have responded to the reviewer comments. This can now be published.
