The Effect of TiC and Zr Additions on the Microstructure and Mechanical Properties of Ti-30Mo Alloy
Round 1
Reviewer 1 Report
The submitted manuscript discusses the influence of the TiC and Zr on the the density, tensile strength, and elastic modulus of the Ti-30Mo alloy. The article is very interesting, well written and should be published in the journal after some changes.
There are several points need to be clarified:
- How was mechanical alloying carried out? On what equipment and why do it for 5 hours?
- How is the compact mode selected?
- The alloys were alloyed 0.5 wt.% TiC and 4-12 wt.% Zr. How the TiC and Zr concentration were chosen? Please state that how these values are chosen or calculated.
- The authors present a method of EDS for elemental analysis of the T0, T4Z, T8Z and T12Z alloys. What chemical composition of these alloy was received by this analysis? Authors must provide this missing information.
- Why was the tensile temperature 600°C chosen for? Authors must justify the choice of this temperature for tensile tests. Which strain rate was in the tests? What are high temperature tests used for?
- How many measurements were taken and with what error were determined density and porosity values of alloys after compact? (Table 1). Table 2, Figure 6, Fig. 11 and Figure 12 with mechanical characteristics should also be corrected with errors.
- The authors used titanium hydride, where is hydrogen in the alloy and does it worsen the properties? why not take pure titanium?
- Figure 9(b). The Mo text color needs to be changed to blue, and the color contrast in the picture needs to be edited.
- Figure 13. It is better to remove the stress drop after fail of the samples on the graph.
- From the conclusions, it is not entirely clear what is the optimal composition of the alloy in terms of the high mechanical properties.
- Author Contributions and other details are not presented.
Author Response
Point 1: How was mechanical alloying carried out? On what equipment and why do it for 5 hours?
Response 1: We have supplemented the ball milling parameters in the experimental section (line 68-70). Ball mill (QM-3SP2) as the equipment, due to the high activity of TiH2 powder, it is very easy to be oxidized after high-energy ball milling. Thus, the powder can only be mixed evenly without mechanical alloying by ball milling. And ball milling for 5 h to make the powder mixed as evenly as possible.
Point 2: How is the compact mode selected?
Response 2: Cold isostatic pressing can ensure the uniform density distribution of the compact and obtain high-quality samples.
Point 3: The alloys were alloyed 0.5 wt.% TiC and 4-12 wt.% Zr. How the TiC and Zr concentration were chosen? Please state that how these values are chosen or calculated.
Response 3: In many research works, the mechanical properties of Ti alloys have been significantly improved by adding trace TiC, and while the addition of Zr is less than 15 wt.%, Ti-Mo alloys have excellent mechanical properties. Thus, 0.5 wt.% TiC and 4, 8, 12 wt.% Zr were added to Ti-30Mo alloy.
Point 4: The authors present a method of EDS for elemental analysis of the T0, T4Z, T8Z and T12Z alloys. What chemical composition of these alloy was received by this analysis? Authors must provide this missing information.
Response 4: We have added the chemical composition of matrix phase and particle phase of TxZ alloys, and made a brief analysis (line 222-229).
Point 5: Why was the tensile temperature 600 °C chosen for? Authors must justify the choice of this temperature for tensile tests. Which strain rate was in the tests? What are high temperature tests used for?
Response 5: At present, the service limit temperature of high-temperature titanium alloys is mostly 600 ℃, we choose this temperature to facilitate the performance comparison with high-temperature titanium alloys.
We have mentioned that the initial strain rate was 1 mm/min in the test (line 106).
We have added the application value of materials in high temperature, and the alloys may be developed into an alternative structural material under high temperature conditions in offshore engineering, chemical industry and other fields (line 58, 59).
Point 6: How many measurements were taken and with what error were determined density and porosity values of alloys after compact? (Table 1). Table 2, Figure 6, Fig. 11 and Figure 12 with mechanical characteristics should also be corrected with errors.
Response 6: For performance values, we tested more than three samples of each component to ensure the accuracy of data. And we have corrected mechanical characteristics with errors in Table 1, Table 2, Figure 6, figure. 11 and Figure 12.
Point 7: The authors used titanium hydride, where is hydrogen in the alloy and does it worsen the properties? why not take pure titanium?
Response 7: In the part of experimental procedure, we supplemented the detailed information of material preparation (line 68-70). By holding at 700 ℃ for 2 h, hydrogen was completely removed as far as possible to avoid the deterioration of properties caused by it. In the introduction, we mentioned that TiH2 can improve the sintering densification of the alloys, and TiH2 has a great price advantage over pure titanium (line 35-38).
Point 8: Figure 9(b). The Mo text color needs to be changed to blue, and the color contrast in the picture needs to be edited.
Response 8: We have remade Figure 9, where we changed the Mo text color to blue and edited the color contrast (line 237).
Point 9: Figure 13. It is better to remove the stress drop after fail of the samples on the graph.
Response 9: We have remade the Figure 13, in which the stress drop after fail of the samples is removed (line 306).
Point 10: From the conclusions, it is not entirely clear what is the optimal composition of the alloy in terms of the high mechanical properties.
Response 10: We have further improved the conclusions. It can be seen that Ti-30Mo-0.5TiC has an excellent combination of mechanical properties (line 332, 333)
Point 11: Author Contributions and other details are not presented.
Response 11: We have added author contributions and other details (line 341-351).
Reviewer 2 Report
- English language must be further improved to increase the quality of the manuscript.
- Some of the typographical errors should be rectified.
- Authors must revise the introduction part by adding the possible applications of prepared alloys, why did they choose the ball milling method etc.
- It is recommended to add the ball milling parameters like ball to powder weight ratio, milling media, milling speed etc, in the experimental section.
- In table 1, authors mentioned that relative density and porosity of Ti-30Mo as 91.2 and 11% respectively. Similarly, for Ti-30Mo-0.5TiC the relative density and porosity are found to be 98.3 and 0.3% respectively. How is this possible. There may be mistake because the percentages are increasing more than 100% in first case and less than 100% in second alloy. Please explain this.
- Figure 4, EDS analysis shows very less amount of Mo compared to parental composition. Why?
Author Response
Point 1: English language must be further improved to increase the quality of the manuscript.
Response 1: We feel sorry for our relatively poor English skills. We have thoroughly checked the structure and logic of the sentence. We also seek for help of researchers who are native speakers to revise the language of our manuscript. The necessary corrections and adjustments have been made in the manuscript.
Point 2: Some of the typographical errors should be rectified.
Response 2: We have corrected some of the typographical errors.
Point 3: Authors must revise the introduction part by adding the possible applications of prepared alloys, why did they choose the ball milling method etc.
Response 3: We have added possible applications of prepared alloys (line 51, 52) and the reasons for choosing the ball milling method in the introductions(line 58, 59).
Point 4: It is recommended to add the ball milling parameters like ball to powder weight ratio, milling media, milling speed etc, in the experimental section.
Response 4: We have supplemented the ball milling parameters in the experimental section. During ball milling, the ball to powder weight ratio is 1:1, the cemented carbide ball as grinding ball, and the ball milling speed is 200 r/min (line 68-70).
Point 5: In table 1, authors mentioned that relative density and porosity of Ti-30Mo as 91.2 and 11%, respectively. Similarly, for Ti-30Mo-0.5TiC the relative density and porosity are found to be 98.3 and 0.3% respectively. How is this possible. There may be mistake because the percentages are increasing more than 100% in first case and less than 100% in second alloy. Please explain this.
Response 5: The relative density is the value calculated according to the theoretical density, while the porosity is the result of experimental measurement. These two data are different ways to characterize the densification of the sample. The results confirm each other, and there is no simple superposition relationship.
Point 6: Figure 4, EDS analysis shows very less amount of Mo compared to parental composition. Why?
Response 6: Figure 4 shows the atomic ratio of each elements, and we added the weight ratio (line 139). It can be seen that the proportion of C element reaches 14 wt.%, which is due to the large error in the detection of C element by EDS, and the content of Ti and Mo are less than that of the parental composition.
Reviewer 3 Report
1) It remains unclear from the text of the article how the concentration ranges of TiC and Zr additives were chosen. How and why were these concentrations chosen?
2) How is the stretching temperature selected? Why 600?
How were the samples made? According to what standard were the tests carried out? These samples are not similar to the standard samples.
3) Conclusions need to be improved. It is not entirely clear what is the optimal composition of the alloy in terms of the high mechanical properties.
4)Error scale bar on figure 11 and 12.
Author Response
Point 1: It remains unclear from the text of the article how the concentration ranges of TiC and Zr additives were chosen. How and why were these concentrations chosen?
Response 1: In many research works, the mechanical properties of Ti alloys have been significantly improved by adding trace TiC, and while the addition of Zr is less than 15wt.%, Ti-Mo alloys have excellent mechanical properties. Thus, 0.5 wt.% TiC and 4, 8, 12 wt.% Zr were added to Ti-30Mo alloy.
Point 2: How is the stretching temperature selected? Why 600?
How were the samples made? According to what standard were the tests carried out? These samples are not similar to the standard samples.
Response 2: At present, the service limit temperature of high-temperature titanium alloys is mostly 600 ℃, we choose this temperature point to facilitate the performance comparison with high-temperature titanium alloys.
The samples were prepared by wire cut electrical discharge machining after sintering (line 76). In order to facilitate the installation of extensometer on the sample during the tensile test, we designed a sample size as shown in Figure 2 (line 109), rather than according to a certain standard.
Point 3: Conclusions need to be improved. It is not entirely clear what is the optimal composition of the alloy in terms of the high mechanical properties.
Response 3: We have further improved the conclusions. It can be seen that Ti-30Mo-0.5TiC has an excellent combination of mechanical properties (line 332, 333)
Point 4: Error scale bar on figure 11 and 12.
Response 4: We have added error scale bars to the experimental values on Fig. 11 (line 266) and Fig. 12 (line 267).
Round 2
Reviewer 1 Report
The authors answered all questions
