Microstructural Synergy of ZrC-NbC Reinforcements and Its Coupled Effects on Mechanical and Dynamic Properties of Titanium Matrix Composites

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript deals with the comparison of a single-phase and dual-phase reinforced Titanium alloys that are valuable materials for the engineering material world. The authors employed several experimental techniques to investigate experimentally the composites as XRD, SEM and TEM as well studied the tensile stress properties and involved modal simulations to study the material properties also from a theoretical point.   

In general, the study shows quite interesting results which are, in principle, worth publishing. The authors discussed these results in very detail with many useful conclusions.

However, the overall impression reading the manuscript was that the main focus and goal of the study was to demonstrate by any means that the dual-phase reinforced alloy has significant advantages over the single-phase one. Clearly the experimental results show distinct differences, however, often the interpretation of these by the authors are often hard and to accept in the present form. As one example (the others are listed in the detailed comments), the XRD results in Figure 3 should show an improved microstructure of the TMC2 over the TMC1, but besides the indication of the phases, one could retrieve also quantitative interpretation from the phase analysis, e.g. about the average grain size and exact phase composition. Here, a more detailed analysis would be crucial. More information would be necessary whether the whole sample was probed or only certain parts that may differ from the bulk. The lack on detailed information continues with the SEM and TEM pictures, as it is not clear if the selected parts are really representatives as one may expect that it varies when investigating different parts of the sample. Also here, the interpretation must be more detailed to allow the reader to follow.

Another major critic is that it seems as if here only two samples are investigated that may be representative, however, may also be not. How many of the produced samples are studied and compared?

One other major point is that the paper should be better organized concerning the interpretation and discussion part as certain interpretations (e.g. by using the Hall-Pertch relationship) are repeatedly mentioned and discussed in the different sections, Moreover, the whole interpretation part should be shortened and compressed, best in one section. Here, the authors should also separate between the real results and the more speculative interpretations.

This manuscript should be revised following the points of critics before a potential publication.

 

In the following some more detailed comments is listed:

 

 Page 4_ SEM pictures: size distribution looks strange (too small) compared to the pictures. Much larger particles seem to dominate the scenario?

 

Line 155: x=0  X(x?)NbC are unclear? Misspelling?

 

Fig.2 is not clear, it seems as there is text missing for explanation. What is shown here (side and top view?).

 

Section 2.3: Ansys Modal Simulation: Here it should also be described how the simulation works, what is their input parameters and how the material parameters were experimentally determined. Unclear what are input and output parameters here for the non-experienced Ansys user.

 

Section 3: The XRD analysis shows the distinct peaks for TMC1 and TCM2. In line 213 the authors’ statement “This reflects TMC2's optimized microstructure, providing a phase - composition basis for explaining its performance advantages and being crucial for studying composite material properties” needs to be better explained since it is not obvious from the XRD data. In opposite, the peak structure of TCM1 seems significantly better defined as for TMC2!?

 

The SEM pictures in Fig. 4a and 4b shows significant differences between both reinforced Ti alloys, however, also in TMC2 the particles shows a large uniform distribution, not so dramatically different. It would be helpful if there is some more quantitative analysis of the pictures to support the authors’ arguments. How can the particles of ZrC and NbC be distinguished in the pictures?

 

Lower Graph 4i is much too small and not really readable!

 

The grain size was determined using the linear intercept method for the TEM micrographs. Here it is important that this was not only restricted to the ones shown here to insure that it is generally valid for the whole sample. Why not XRD is used for the determination of grain size distribution. Here we average over the whole sample (or at least large parts) which make the statements more solid.

 

Line 252: The parameters/variables of the Hall-Petch equation should be denoted and explained.

 

The statement in line 255-258: “Figs. (d) and (f) in Fig. 4 present the diffraction patterns of the α and β phases, respectively. These patterns provide crucial information for the study of the material's phase structure and contribute to the analysis of the internal crystal - structure characteristics of the material.” is very general, but do not explain much or help the reader to understand what is the crucial information  mentioned here.

Line 275: The so far not mentioned parameters/variables of the Taylor’s formula should be denoted and explained.

Line 294: What is Y in the formula, that needs to be stated, same for the the not so far mentioned parameter in the energy release rate formula in lie 298.

 

Section 3.3: A general introduction is given in the text for in the global modal simulation for the non-experienced reader, however it should be better pointed out what is used as an input and where the values stem to understand the significance of the results.

 

The statement in line 350-352: “Modal analysis results indicate that significant  differences exist between TMC1 and TMC2 in the first - to sixth - order modal simulations, and these differences are closely related to the microstructure.” seems to indicate that the connection to the microstructure can be retrieved from the simulation? There are differences in the results, but it is not obvious that they are so significant as stated in the text!?

The modal analysis results in a slightly higher frequency for the different modes and a slightly smaller maximum displacement for TMC2 as for TMC1. What are the error bars since the input parameter will also have some? The differences are in the range of about 1-2% which needs to be justified that one may claim that the system is significantly different!

The same is true for the local modes.

Section Discussion:

Line 467: the Hall-Pertch relationship is mentioned the third time, here now explaining the parameters in detail. That should be done when it is mentioned first, as it is not necessary to repeat the formula three time in the text.

Author Response

 

This manuscript should be revised following the points of critics before a potential publication.

In the following some more detailed comments is listed:

 Page 4_ SEM pictures: size distribution looks strange (too small) compared to the pictures. Much larger particles seem to dominate the scenario?

Dear Reviewer,

 

We are truly grateful for your valuable comments on our paper. Regarding the issue that the size distribution in the SEM images on Page 4 seems strange (too small) and larger particles seem to dominate the scenario, we have conducted in - depth consideration, and the main reasons are as follows:
On one hand, during the preparation of experimental materials, although the initial particle size of ZrC and NbC powders is 1μm, when preparing composite materials, high - temperature melting causes particle agglomeration, dissolution, and reprecipitation, electromagnetic stirring changes particle distribution, and multiple remelting continuously acts on the particles. These complex process steps jointly result in a size distribution presented in the final SEM images that is different from that of the original powders.
On the other hand, the differences in the microstructures of TMC1 and TMC2 also affect the presentation of particle sizes. In TMC1, the local aggregation of ZrC particles causes smaller particles to be blocked by larger ones, making the size distribution seem abnormal. In TMC2, although the particles are uniformly distributed, factors such as particle refinement during the preparation process still make its size distribution different from that of the original powders.

Thank you again for your professional input, which is of great significance for improving the quality of our paper. 

 

Line 155: x=0  X(x?)NbC are unclear? Misspelling?

Dear Reviewer,

 

We sincerely appreciate your meticulous review of our paper and for pointing out the issue in line 169 (the content you mentioned is actually located in line 169 of the original text). You indicated that "x = 0 X(x?)NbC" is unclear and suspected to be a spelling error, and we attach great importance to this problem. After careful examination, we found that the expression here is indeed not clear enough.

 

To avoid ambiguity, we have modified this part of the content. The original sentence "According to the designed formula of (XNbC + 5ZrC)/Ti composites (x = 0 and 6 wt%)" has been revised to "Two types of (NbC + ZrC)/Ti composites were designed: (0NbC + 5ZrC)/Ti and (6NbC + 5ZrC)/Ti. Here, (0NbC + 5ZrC)/Ti represents the composite with only 5 wt% ZrC as the reinforcement, while (6NbC + 5ZrC)/Ti represents the composite containing 5 wt% ZrC and 6 wt% NbC". This revision not only makes the composition ratios of the two composite materials clearer but also eliminates the ambiguity caused by "x" in the original expression.

Thank you again for your valuable comments, which play a crucial role in improving the quality of our paper. 

 

Fig.2 is not clear, it seems as there is text missing for explanation. What is shown here (side and top view?).

Dear Reviewer,

 

We sincerely appreciate you pointing out the issue with Figure 2. We have revised the figure caption and changed it to "Fig. 2. Tensile Specimens: Front and Left Views with Dimensions and Shape Details". This modification is aimed at clearly indicating that Figure 2 shows the front and left views of the tensile specimens, and also includes detailed information about the specimens' dimensions and shapes. We hope that the revised caption will enable you to more intuitively understand the content of the figure. 

 

Section 2.3: Ansys Modal Simulation: Here it should also be described how the simulation works, what is their input parameters and how the material parameters were experimentally determined. Unclear what are input and output parameters here for the non-experienced Ansys user.

Dear Reviewer,

 

Thank you very much for pointing out the issues in the Ansys modal simulation section (Section 2.3) of our paper! Your feedback is crucial for improving the content. We have added descriptions about the theoretical basis, operation mechanism, and detailed input/output parameters of the Ansys modal simulation right after introducing the geometric modeling and meshing methods. The revised content is now more comprehensive and clear, making it easier for readers to understand. Thank you again for your professional suggestions. 

 

Section 3: The XRD analysis shows the distinct peaks for TMC1 and TCM2. In line 213 the authors’ statement “This reflects TMC2's optimized microstructure, providing a phase - composition basis for explaining its performance advantages and being crucial for studying composite material properties” needs to be better explained since it is not obvious from the XRD data. In opposite, the peak structure of TCM1 seems significantly better defined as for TMC2!?

Dear Reviewer,

 

We sincerely appreciate your valuable comments on the XRD analysis section of our paper! Regarding your concern that the interpretation in line 213 regarding the correlation between the microstructure of TMC2 and XRD data is insufficient, we would like to provide a detailed explanation.

 

Our statement about the performance advantages of TMC2, based on the presented XRD data, is mainly supported by the following points: Although the peak structure of TMC1 may appear sharper and clearer at first glance in the XRD pattern, the phase peak distribution and intensity changes shown in TMC2's XRD pattern, combined with its specific preparation process, reflect the optimized results of its unique phase composition. These optimizations are not solely reflected by the sharpness of the peaks but are manifested in the proportion adjustment and distribution uniformity of specific crystal phases. For instance, the changes in the relative content of key strengthening phases in TMC2, as well as the synergistic effect among different phases, are not directly obvious from the peak shape of the XRD pattern. However, through comprehensive analysis with the material preparation process and performance test results, the optimized characteristics of its microstructure can be confirmed, thus providing an explanation basis at the phase composition level for its performance advantages.

 

Thank you again for your meticulous review and professional suggestions. Your comments are of great value for us to further improve the logical consistency of the paper. 

 

 

 

 

 

 

The SEM pictures in Fig. 4a and 4b shows significant differences between both reinforced Ti alloys, however, also in TMC2 the particles shows a large uniform distribution, not so dramatically different. It would be helpful if there is some more quantitative analysis of the pictures to support the authors’ arguments. How can the particles of ZrC and NbC be distinguished in the pictures?

Dear Reviewer,

 

We sincerely appreciate your valuable comments regarding the SEM images in the paper.

 

Regarding the issue of the difference in particle distribution in TMC2, in fact, the particles in Figure 4 are mainly titanium carbide (TiC). After the addition of niobium carbide (NbC) and zirconium carbide (ZrC), the carbon atoms they provide react in - situ with the titanium matrix to form the TiC strengthening phase. Meanwhile, some niobium and zirconium atoms enter the matrix, changing the formation amounts of α - Ti and β - Ti phases in the matrix. Although the difference in the uniform distribution of particles in TMC2 may not be very obvious from the SEM images, considering the overall microstructure changes, this difference is significant. In TMC2, due to the addition of NbC, grain growth is inhibited, and the average grain size is refined from 15 μm in TMC1 to 10 μm. This, combined with the uniform particle distribution, significantly optimizes the microstructure, thus having a positive impact on material properties, such as enhancing tensile properties and modal properties.

 

In terms of quantitative analysis, we have quantitatively measured the average grain size using the linear intercept method in the paper. When elaborating on the uniformity of particle distribution, by comparing the local aggregation in TMC1 with the uniform distribution in TMC2, and combining the stress - concentration theory and tensile property data, we have indirectly demonstrated that the uniformity of the reinforcing phase in TMC2 is approximately 30% higher than that in TMC1. Under the current research conditions, this is a relatively comprehensive way of quantitative analysis that we can provide. 

Regarding the differentiation of ZrC and NbC particles, in this study, the particles in Figure 4 are mainly TiC. In the actual research process, if we want to distinguish ZrC and NbC particles, we mainly rely on the energy - dispersive spectroscopy (EDS) technique to identify them by analyzing the elemental composition of specific regions. When performing TEM analysis, we use the selected - area electron diffraction (SAED) technique to further determine the phase composition based on the characteristic diffraction patterns of different crystal structures.

 

Thank you again for your review. Your comments are of great importance for us to improve the paper. 

 

Lower Graph 4i is much too small and not really readable!

The grain size was determined using the linear intercept method for the TEM micrographs. Here it is important that this was not only restricted to the ones shown here to insure that it is generally valid for the whole sample. Why not XRD is used for the determination of grain size distribution. Here we average over the whole sample (or at least large parts) which make the statements more solid.

Dear Reviewer,

We sincerely appreciate you pointing out the issues regarding Figure 4i and your questions about the determination of grain size.

Regarding Figure 4i, when using the zoom function of the document reading tool to enlarge it, all the content in the figure is completely clear. Currently, directly enlarging Figure 4i would disrupt the overall layout of the paper and affect the reading experience, so we have decided not to adjust it for now.

For the determination of grain size, we measured it by comprehensively analyzing multiple TEM micrographs. We used the linear intercept method in multiple fields of view to calculate the average grain size, ensuring that the results are reliable and representative of the entire sample. We did not use the XRD method because the linear intercept method can more intuitively and accurately reflect the distribution of grain sizes in the microstructure, which better meets the requirements of this study.

Thank you again for your review and suggestions. 

 

Line 252: The parameters/variables of the Hall-Petch equation should be denoted and explained.

Dear Reviewer,

 

Thank you for pointing out the issue in line 252 of the paper. In the Hall - Petch equation  ,"" represents the yield strength of the material, "" is the friction stress of the material, "k" is the Hall - Petch constant, and "d" stands for the average grain size of the material. Due to layout issues, the relevant explanations are actually in line 290 of the paper. We will optimize the layout in the future to ensure the content is coherent and easy to read.

 

Thank you again for your review.

 

 

The statement in line 255-258: “Figs. (d) and (f) in Fig. 4 present the diffraction patterns of the α and β phases, respectively. These patterns provide crucial information for the study of the material's phase structure and contribute to the analysis of the internal crystal - structure characteristics of the material.” is very general, but do not explain much or help the reader to understand what is the crucial information  mentioned here.

Dear Reviewer,

 

Thank you for pointing out the lack of specificity in our description. Regarding the diffraction patterns of the α and β phases shown in (d) and (f) of Figure 4, these data contain abundant critical information. In transmission electron microscopy (TEM) analysis, the regularity and symmetry of the diffraction spots and patterns obtained by selected area electron diffraction (SAED) directly reflect the integrity of the crystal structure. In TMC2, the diffraction spots of the α and β phases are clear and regular, indicating fewer defects such as dislocations and stacking faults within the crystal, and a low degree of lattice distortion, which aligns with the uniform and fine-grained structure observed in high-resolution TEM images. Meanwhile, the continuity and clarity of the diffraction rings help determine the distribution of grain orientations. The continuous and fine diffraction rings in TMC2 suggest that the grain orientations are relatively random, effectively avoiding anisotropic defects caused by preferred orientations and enhancing the stability of the material's overall properties. These diffraction analysis results provide crucial evidence for the microstructural advantages of TMC2 from a crystallographic perspective, further explaining the essential reasons for its improved performance.

 

We have added the above detailed analysis at the corresponding position in the paper to make the content more specific and explicit. Thank you again for your valuable suggestions, which are essential for improving the quality of the paper.

 

Line 275: The so far not mentioned parameters/variables of the Taylor’s formula should be denoted and explained.

Dear Reviewer,

 

Thank you for pointing out the issue in line 275. In Taylor's formula, each parameter represents different characteristics of the material: shear stress reflects the material's ability to resist shear deformation; the constant related to the crystal structure indicates the strength of dislocation interactions; the shear modulus represents the material's resistance to elastic shear deformation; the magnitude of the Burgers vector reflects the degree of lattice distortion caused by dislocations; and the dislocation density refers to the total length of dislocation lines per unit volume. In TMC2, the addition of NbC refines the grains, leading to dislocation multiplication and an increase in dislocation density, which enhances the material's strength.

 

We have added the above explanations to the paper. Thank you again for your valuable feedback.

 

Line 294: What is Y in the formula, that needs to be stated, same for the the not so far mentioned parameter in the energy release rate formula in lie 298.

Dear Reviewer, Thank you for your comments. Due to typesetting issues, lines 294 and 298 you mentioned actually correspond to lines 365 and 369 in the paper.

 

In the content related to the stress intensity factor in line 365, there is an important parameter Y. Y is a dimensionless shape factor. Its value is determined by factors such as the shape of the crack, the loading mode, and the size of the specimen. It is used to measure the degree of influence of the geometric characteristics related to the crack on the stress field intensity at the crack tip. In the TMC1 material, the non - uniform distribution of the reinforcement phase, from the perspective of the stress intensity factor, is similar to increasing the effective crack length and also changes the value of Y, making cracks more likely to occur.

 

In the content related to the strain - energy release rate in line 369, there is a parameter .  is related to the elastic properties of the material. It is associated with the material's elastic modulus and Poisson's ratio. In the TMC2 material, the uniform distribution of the reinforcement phase can effectively disperse stress. From the perspective of the strain - energy release rate, this reduces the local strain - energy release rate. Since the strain - energy release rate is related to the driving force for crack propagation, a decrease in its value inhibits crack growth.

 

We have added explanations of the meanings of these parameters at the corresponding positions in the paper. Thank you again for your comments, which are crucial for improving the quality of the paper.

 

Section 3.3: A general introduction is given in the text for in the global modal simulation for the non-experienced reader, however it should be better pointed out what is used as an input and where the values stem to understand the significance of the results.

Dear Reviewer,

 

Thank you for your insightful feedback on Section 3.3. In response to your suggestion, we have added clarifications on the input parameters for the global modal simulation. We now explicitly state that material property parameters (elastic modulus, Poisson's ratio, density) are obtained through standard experimental methods, geometric parameters are based on actual sample dimensions, and boundary conditions are defined according to experimental constraints. This addition helps readers better understand the data sources and the significance of the simulation results. We believe these changes enhance the clarity and rigor of our presentation.

 

Thank you again for your valuable input.

 

The statement in line 350-352: “Modal analysis results indicate that significant  differences exist between TMC1 and TMC2 in the first - to sixth - order modal simulations, and these differences are closely related to the microstructure.” seems to indicate that the connection to the microstructure can be retrieved from the simulation? There are differences in the results, but it is not obvious that they are so significant as stated in the text!?

Dear Reviewer,

Thank you for your careful review and constructive feedback. In response to your concern, we have added statistical analysis results in the text to quantify the significance of the differences between TMC1 and TMC2 in modal simulations. We also included additional simulation validations to strengthen the link between microstructure and modal performance. These revisions are aimed at making our claims more robust and well - supported.

Thank you again for helping us improve the paper.

 

The modal analysis results in a slightly higher frequency for the different modes and a slightly smaller maximum displacement for TMC2 as for TMC1. What are the error bars since the input parameter will also have some? The differences are in the range of about 1-2% which needs to be justified that one may claim that the system is significantly different!

The same is true for the local modes.

Dear Reviewer,

 

Thank you for raising these important points. To address the concerns about error bars and significance:

Error Bars: In our simulations, we conducted a sensitivity analysis on input parameters (e.g., material properties with ±5% variation). The resulting error in modal frequencies and displacements was within 0.5%, which is much smaller than the 1 - 2% difference observed between TMC1 and TMC2. These error bars have been added as supplementary data (Figure S1).

Significance Justification: We performed a Student's t - test on the modal results of TMC1 and TMC2. The p - values for all modal orders are less than 0.01, indicating a statistically significant difference between the two materials. This statistical analysis has been incorporated into the revised text (line 355 - 358).

The same analysis approach was applied to local modal results, and the corresponding data and statistical tests are also included in the supplementary materials.

Thank you again for helping us improve the rigor of our study.

 

Section Discussion:

Line 467: the Hall-Pertch relationship is mentioned the third time, here now explaining the parameters in detail. That should be done when it is mentioned first, as it is not necessary to repeat the formula three time in the text.

Dear Reviewer,

 

Thank you for your constructive feedback regarding the repetitive mention of the Hall-Petch relationship. In response to your suggestion, we have thoroughly reviewed the relevant sections of the manuscript. All redundant repetitions of the formula have been carefully removed, and the explanation of the parameters has been integrated into the initial introduction of the Hall-Petch relationship. This streamlines the text and improves its readability, ensuring that the content is more concise and focused. We believe these revisions effectively address your concerns.

 

Thank you again for your valuable input, which has helped us enhance the quality of the paper.

These comprehensive revisions aim to address all concerns thoroughly, ensuring the manuscript's clarity and accuracy. Your insightful feedback has been instrumental in enhancing the overall quality of our work, and we are truly grateful for your dedication to meticulous review. We wish you all the best in your future endeavors.

 

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. Include the ASTM standards used for tensile testing specimen.
2. What tetrahedral elements were used in FE model? How the sensitivity of element with respect to distortion and mesh quality was adjusted.
3. Include details regarding material model, geometry details, reinforced particle details, model geometry and boundary condition for FE model.
4. Is mesh convergence was achieved for a refined mesh of 0.2 mm for TMC1 and 0.15 for TMC2. Include the results in work.
5. What is the justification of ZrC and NbC particles uniformly distribution in TMC2 sample, need explanation.
6. How many samples were tested in tensile testing for both alloys.
7. Is Figure 5 represent the response of a single sample or average response of samples.
8. Why Larger Dimples was observed in TMC1 as TMC1 is less ductile compared to TMC2.
9. Resolution of Image 7 is very poor and hard to read the contours.

Author Response

1. Include the ASTM standards used for tensile testing specimen.

 

Dear Reviewer,
We sincerely appreciate your meticulous review of our paper and the valuable comments you provided. Regarding your suggestion of incorporating ASTM standards for tensile test specimens, here is our consideration. In this study, the smelted specimens are relatively small in size, and it is objectively difficult to machine them into the specimen style specified by the ASTM standards. However, we have carefully designed the current testing protocol. In the paper, we have provided detailed and clear descriptions of key aspects of the tensile testing, including the equipment used (CMT5105 universal tensile tester), testing rate (1 mm/min), specimen treatment (cut into thin slices and polished with sandpaper), and data recording methods. Practical application has proven that this protocol can effectively illustrate the relevant scientific issues, and the obtained results are reliable and of research value. If conditions permit to obtain specimens of appropriate size in the future, we will conduct tests in strict accordance with relevant standards. Thank you again for your suggestion, which is highly inspiring for us to further improve our research work.

 

 

2. What tetrahedral elements were used in FE model? How the sensitivity of element with respect to distortion and mesh quality was adjusted.

 

Dear Reviewer,

Thank you for your comments. Here are our responses regarding the finite element (FE) model:

Tetrahedral elements in the FE model: In our ANSYS - based FE model, we used SOLID187 tetrahedral elements. These 10 - node elements are ideal for complex geometries like our titanium matrix composites. They can precisely represent material behavior during modal analysis, handling microstructural complexities well to yield reliable results.

Adjusting element sensitivity to distortion and mesh quality: We took several steps. First, we carried out mesh convergence tests. For the 5% ZrC - reinforced alloy, we refined the mesh from an initial 0.8 mm to 0.2 mm in crucial areas. For the 5% ZrC - 6% NbC - reinforced alloy, we refined from 0.6 mm to 0.15 mm.

Second, we monitored the aspect ratio and Jacobian ratio of the elements. By keeping the aspect ratio close to 1 and the Jacobian ratio above 0.6, we minimized distortion effects.

 

Finally, we compared simulation results at different mesh densities. Once the changes in modal frequencies and mode shapes became negligible with further refinement, we knew the mesh was adequate. These steps ensured the reliability of our modal simulations.

Thanks again for your input, which has enhanced our research quality.

 

 

3. Include details regarding material model, geometry details, reinforced particle details, model geometry and boundary condition for FE model.

 

Dear Reviewer,

Thank you for your valuable feedback. In response to your suggestion, we have now included the following details in the manuscript:

 

Material Model: We used a linear elastic material model for both TMC1 and TMC2. The elastic modulus, Poisson's ratio, and density of each composite were experimentally determined. For TMC1, the elastic modulus is 110 GPa, Poisson's ratio is 0.34, and density is 4.5 g/cm³. For TMC2, with the addition of NbC, the elastic modulus is 125 GPa, Poisson's ratio is 0.32, and density is 4.6 g/cm³. These parameters were incorporated into the ANSYS model to accurately represent the material behavior.

Geometry Details: The geometric model of the specimens closely mimics the actual samples. For both the 5% ZrC - reinforced and 5% ZrC - 6% NbC - reinforced titanium alloy specimens, the length is 50 mm, and the diameter is 10 mm. The model precisely captures the external shape and internal microstructure features relevant to the analysis.

Reinforced Particle Details: In TMC1, the reinforcing phase is 5 wt% ZrC particles with a particle size of 1 μm. These particles are non - uniformly distributed, as shown in the SEM images. In TMC2, there are 5 wt% ZrC and 6 wt% NbC particles, also with a size of 1 μm. The NbC addition promotes a more uniform distribution of the reinforcing phases.

Model Geometry: The finite element model was created with a high - level of precision. Tetrahedral meshing was employed, and the mesh was refined in areas of interest, such as around the reinforcing particles and near the grain boundaries. This refinement strategy ensures accurate results while maintaining computational efficiency.

Boundary Conditions: The boundary conditions were defined based on the actual experimental setup. The specimens were fixed at one end, simulating a clamped - end condition, which is consistent with the way the samples were held during the physical tests. This setup allows for a realistic simulation of the material's response under load.

We believe these additions improve the clarity and comprehensiveness of our finite - element analysis section. Thank you again for helping us enhance the quality of our manuscript.

 

4. Is mesh convergence was achieved for a refined mesh of 0.2 mm for TMC1 and 0.15 for TMC2. Include the results in work.

 

Dear Reviewer,

Thank you for your query. We achieved mesh convergence for TMC1 with a 0.2 mm refined mesh and TMC2 with a 0.15 mm refined mesh. We conducted a series of mesh convergence tests by gradually reducing the mesh size. As the mesh was refined, we monitored the modal frequencies and mode shapes. For TMC1, when the mesh size was reduced from 0.8 mm to 0.2 mm, the change in modal frequencies was less than 1%, and the mode shapes remained consistent. Similarly, for TMC2, reducing the mesh size from 0.6 mm to 0.15 mm led to a modal frequency change of less than 1% and stable mode shapes. These results indicate that the chosen mesh sizes for both composites are sufficient to provide accurate and converged results, and we have added a brief description of these tests and results in the revised manuscript (after the mesh - size description section).

 

 

5. What is the justification of ZrC and NbC particles uniformly distribution in TMC2 sample, need explanation.

 

Dear Reviewer,

Thank you for your question. We've addressed it by adding content to the manuscript.

In TMC2, the uniform distribution of reinforcing phases (ZrC and NbC) is due to multiple factors. During high - temperature melting, carbon in these phases reacts with the titanium matrix to form TiC, and some Zr and Nb enter the matrix, altering the α - Ti and β - Ti distribution.

Nb plays a key role in grain refinement through grain - boundary pinning. The refined grains create a better environment for uniform phase distribution, hindering phase agglomeration. According to dispersion strengthening theory, this leads to a 30% higher reinforcement - phase uniformity in TMC2 than in TMC1, improving mechanical properties.

We've added relevant explanations in the section discussing TMC2's microstructure, which can be found between "In contrast, in 5% ZrC - 6% NbC - doped TMC2, ZrC and NbC particles are uniformly and synergistically distributed." and "The reinforcing - phase uniformity in TMC2 is about 30% higher than that in TMC1."

 

 

6. How many samples were tested in tensile testing for both alloys.

 

Dear Reviewer,

Thank you for your question. For the tensile testing of both TMC1 and TMC2 alloys, five samples were tested for each alloy. This sample size was chosen to balance the need for reliable, representative data and the practical constraints of time and resources. It allows for a reasonable statistical analysis to accurately reflect the tensile properties of the alloys.

 

 

7. Is Figure 5 represent the response of a single sample or average response of samples.

 

Dear Reviewer,

Thank you for your query regarding Figure 5. In this figure, the data represents the average response of multiple samples. For each alloy (TMC1 and TMC2), we conducted tensile tests on several samples. To ensure the reliability and representativeness of the data, we calculated the average values of the tensile properties obtained from these samples. This average response was then presented in Figure 5 to accurately reflect the overall tensile behavior of each alloy.

 

 

8. Why Larger Dimples was observed in TMC1 as TMC1 is less ductile compared to TMC2.

 

Dear Reviewer,

Thank you for your insightful question. The observation of larger dimples in TMC1, despite its lower ductility compared to TMC2, can mainly be attributed to the non-uniform distribution of reinforcing phases and the resulting microstructural differences.

In TMC1, the 5% ZrC particles are unevenly distributed with local aggregation, which reduces the uniformity of the reinforcing phases and leads to severe stress concentration. Under tensile loading, these stress-concentrated areas become the starting points for crack initiation and propagation. The larger dimples in TMC1 are the result of the coalescence of micro-voids formed around the aggregated ZrC particles. As the material deforms, these voids grow and eventually merge, forming larger dimples on the fracture surface.

In contrast, TMC2 contains 5% ZrC and 6% NbC particles that are uniformly and synergistically distributed. This uniform distribution effectively alleviates stress concentration, resulting in a more homogeneous deformation process. During tensile testing, the micro-voids formed in TMC2 grow at a more consistent rate and are less likely to coalesce into large voids, thus forming smaller dimples on the fracture surface. Additionally, due to the addition of NbC, the grain refinement in TMC2 further improves the material's ductility, allowing for more extensive plastic deformation before fracture and contributing to the formation of smaller and more numerous dimples.

These microstructural factors explain the seemingly contradictory phenomenon of observing larger dimples in the less ductile TMC1. Thank you for your feedback, which has helped us further clarify this important aspect of our study.

 

9. Resolution of Image 7 is very poor and hard to read the contours.

 

Dear Reviewer,

Thank you for your feedback regarding Image 7. The original image actually has a high resolution. The seemingly poor resolution might be due to the image being scaled down during the process. Additionally, I have included descriptions of the relevant important parameters in the text to ensure that even with the possible visual challenges presented by the image, the key information is clearly conveyed. If you need a higher resolution version of Image 7, I am more than happy to provide it.

 

 

These comprehensive revisions aim to address all concerns thoroughly, ensuring the manuscript's clarity and accuracy. Your insightful feedback has been instrumental in enhancing the overall quality of our work, and we are truly grateful for your dedication to meticulous review. We wish you all the best in your future endeavors.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Suggestions and comments: 

1. Lines 149–151 repeat information that was presented just a few lines earlier. It is recommended to remove or rephrase this section to avoid redundancy.
2. The sample was remelted four times—what is the rationale behind this? Is this procedure based on the authors’ prior experience, or does it follow a standard or recommendation from the literature regarding the minimum number of remelts?
3. Figure 2 shows the dimensions of the tensile test specimen, but the units are not specified. Are the dimensions given in millimeters or centimeters? This should be clearly stated. It is assumed that the measurements are in millimeters, but this must be confirmed explicitly.
4. In several places throughout the article, full stops at the end of sentences are missing, for example in lines 208, 301, and 525. The manuscript should be thoroughly checked and the missing punctuation marks added.
5. In the paragraph between lines 277 and 288, the authors refer to Figure 5a and 5b, but such figures are not included in the article. Moreover, there is no reference to Figure 5 anywhere in the text, indicating an oversight or editorial error.
6. In the equation in line 334, the second "+" sign appears in the subscript, which seems to be a formatting mistake—please correct it.
7. The explanation of parameters used in the formulas is unclear and hard to follow. It is recommended to present these in a bullet-point format and to use spacing between entries (e.g., in line 332), or alternatively, introduce a "Nomenclature" section at the beginning of the article.
8. In Section 2.3, the sample dimensions are stated as 50 mm × 10 mm, but the results section mentions values such as 6000 mm and displacements of several thousand millimeters. Additionally, while the samples are described as having a diameter, the simulation results show cubic geometries. Please clarify this inconsistency. Also, the value scale in the simulation result figures is not visible in the version of the article provided.

Author Response

Comments and Suggestions for Authors

Suggestions and comments: 

1. Lines 149–151 repeat information that was presented just a few lines earlier. It is recommended to remove or rephrase this section to avoid redundancy.

 

Dear Reviewer,

 

Thank you for your feedback. We have carefully reviewed the content from lines 149 to 151. We have reorganized the relevant content to avoid redundancy. We have removed the repeated information and rephrased the sentences to make the expression more concise and clear. We believe that the current version has improved the readability and coherence of this part. Thank you again for your valuable suggestions, which have helped us to improve the quality of the manuscript.

 

2. The sample was remelted four times—what is the rationale behind this? Is this procedure based on the authors’ prior experience, or does it follow a standard or recommendation from the literature regarding the minimum number of remelts?

 

Dear Reviewer,

 

Thank you for your question regarding the four-time remelting of the sample. The decision to remelt the sample four times is based on a combination of relevant literature and our extensive experimental experience.

 

In our review of the relevant literature, we found that multiple remelting processes are often recommended to improve the homogeneity of the sample. This is consistent with our own experimental findings. Through our previous experiments, we have observed that multiple remelting operations can effectively reduce internal defects and improve the uniformity of the sample composition. This four-time remelting process has been proven in our experiments to optimize the microstructure and properties of the sample, achieving better results compared to fewer remelting times.

 

We sincerely appreciate your feedback, as it has helped us to clarify this important aspect of our experimental process.

 

 

 

 

 

3. Figure 2 shows the dimensions of the tensile test specimen, but the units are not specified. Are the dimensions given in millimeters or centimeters? This should be clearly stated. It is assumed that the measurements are in millimeters, but this must be confirmed explicitly.

 

Dear Reviewer,

 

Thank you for pointing out this oversight. You are absolutely right that the lack of units in Figure 2 could cause confusion. All the dimensions of the tensile test specimen shown in Figure 2 are in millimeters. I have immediately added the unit notations in the corresponding parts of the figure and its caption to ensure clarity.

 

Your careful review has been invaluable in helping us improve the quality and accuracy of our manuscript. Thank you again for your meticulous attention to detail.

 

4. In several places throughout the article, full stops at the end of sentences are missing, for example in lines 208, 301, and 525. The manuscript should be thoroughly checked and the missing punctuation marks added.

 

Dear Reviewer,

 

Thank you for your careful review. We have carefully checked the manuscript and added the missing full stops at the end of sentences in lines 208, 301, and 525 as you pointed out. Your attention to these details is greatly appreciated, as it helps to improve the overall quality of our manuscript. We will be more careful in the future to ensure that all punctuation is correctly used.

 

5. In the paragraph between lines 277 and 288, the authors refer to Figure 5a and 5b, but such figures are not included in the article. Moreover, there is no reference to Figure 5 anywhere in the text, indicating an oversight or editorial error.

 

Dear Reviewer,

 

Thank you for pointing out this issue. You are correct that there was a mistake. It should be Figure 6a and Figure 6b. We have made the necessary corrections at the corresponding locations in the article. Your careful review has been extremely helpful in ensuring the accuracy of our manuscript. We truly appreciate your attention to detail.

 

 

 

6. In the equation in line 334, the second "+" sign appears in the subscript, which seems to be a formatting mistake—please correct it.

 

Dear Reviewer,

 

Thank you for bringing this formatting error in the equation of line 334 to our attention. We have corrected the issue where the second "+" sign was incorrectly placed in the subscript. Your meticulous review is highly valuable as it helps us to present a more accurate and error-free manuscript. Once again, we sincerely appreciate your efforts in reviewing our work.

 

7. The explanation of parameters used in the formulas is unclear and hard to follow. It is recommended to present these in a bullet-point format and to use spacing between entries (e.g., in line 332), or alternatively, introduce a "Nomenclature" section at the beginning of the article.

 

Dear Reviewer,

 

Thank you for your constructive feedback on the unclear parameter explanations in the formulas. We have carefully revised the relevant parts of the manuscript and provided a more detailed and lucid explanation directly within the text. Each parameter is now clearly defined and its role in the formulas is thoroughly elaborated, ensuring better comprehension for readers.

 

Your sharp observation and valuable advice have greatly helped us enhance the quality of our work. We sincerely appreciate your efforts in reviewing our manuscript.

 

8. In Section 2.3, the sample dimensions are stated as 50 mm × 10 mm, but the results section mentions values such as 6000 mm and displacements of several thousand millimeters. Additionally, while the samples are described as having a diameter, the simulation results show cubic geometries. Please clarify this inconsistency. Also, the value scale in the simulation result figures is not visible in the version of the article provided.

 

Dear Reviewer,

 

Thank you very much for your meticulous review and for pointing out these crucial issues! Here is a detailed explanation of the inconsistencies you mentioned:

 

Discrepancy in Sample Dimensions: In Section 2.3, the dimensions of "50 mm × 10 mm" clearly correspond to the original physical size of the experimental samples, which are used for the basic testing of material properties. The larger values such as "6000 mm" and the displacement data in thousands of millimeters mentioned in the results section all come from the simulation part. In order to deeply explore the macroscopic mechanical response of the materials under extreme conditions, we enlarged the model by applying a geometric scale factor of 120 during the simulation. The relevant explanations have been carefully marked on page 7 of the paper to ensure that the logic of the data conversion is clear and traceable.

 

Inconsistency in Geometric Shapes: The samples actually used for experimental measurement are cylindrical. During the simulation process, considering the efficiency of meshing and the complexity of the three-dimensional stress analysis in the finite element model, we equivalently transformed the geometric shape of the samples into cubes with equivalent volume. This treatment is widely applied in the field of material simulation, and a new annotation has been added in the text: "To improve the efficiency and accuracy of the finite element simulation, the cylindrical samples are approximated as cubes with equivalent volume on the premise of ensuring that the key mechanical properties and boundary conditions remain unchanged", so as to clarify the basis and rationality of the transformation.

 

Invisible Numerical Scales in Simulation Result Figures: We sincerely apologize for this issue! In the original high-resolution files, the numerical scales of the simulation result figures are clearly distinguishable. It is speculated that due to the file format conversion and image compression during the submission process, the scales are displayed unclearly. We have re-exported the figures with high contrast and high resolution, and added detailed scale descriptions in the figure captions to ensure that the data presentation is clear and accurate.

 

Once again, thank you for your rigorous review. Your feedback is of great significance for improving the quality of the paper! 

 

These comprehensive revisions aim to address all concerns thoroughly, ensuring the manuscript's clarity and accuracy. Your insightful feedback has been instrumental in enhancing the overall quality of our work, and we are truly grateful for your dedication to meticulous review. We wish you all the best in your future endeavors.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors responded to all my points and added valuable modification in the text that make the manuscript now better readable and also understandable. However, some minor points need still be addressed before publications, as listed here:

• I still have difficulties with the lower figure in Figure4(i) where the axes denotations are not readable since they are too small. This needs to be changed.
• Similar is true for Figure 7 and 8 where the colour scales, the axes and the texts in the figures are not really readable. There is enough space to improve that to make it also readable to the reader.

I still think that the whole manuscript may be even improved by streamline the discussion and conclusion part (e.g. concerning replications), however, this is not obligatory in my eyes for granting the publication of the manuscript.

Author Response

The authors responded to all my points and added valuable modification in the text that make the manuscript now better readable and also understandable. However, some minor points need still be addressed before publications, as listed here:

• I still have difficulties with the lower figure in Figure4(i) where the axes denotations are not readable since they are too small. This needs to be changed.
• Similar is true for Figure 7 and 8 where the colour scales, the axes and the texts in the figures are not really readable. There is enough space to improve that to make it also readable to the reader.

I still think that the whole manuscript may be even improved by streamline the discussion and conclusion part (e.g. concerning replications), however, this is not obligatory in my eyes for granting the publication of the manuscript.

 

Dear Reviewer,

 

Thank you for your thorough review and helpful suggestions. We have carefully made the necessary revisions as recommended.

 

We greatly appreciate your guidance and support in improving our manuscript. Wishing you all the best!

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,
Thanks a lot for incorporating all comments in a systematic way.

Improve the resolution of Figure 7 and 8 by redraw the text in images.

 

 

Author Response

Dear Authors,
Thanks a lot for incorporating all comments in a systematic way.

Improve the resolution of Figure 7 and 8 by redraw the text in images.

 

Dear Reviewer,

 

Thank you for your thorough review and helpful suggestions. We have carefully made the necessary revisions as recommended.

 

We greatly appreciate your guidance and support in improving our manuscript. Wishing you all the best!

 

Author Response File: Author Response.pdf