Determination of Constitutive Equation and Thermo–Mechanical Processing Map for Pure Iridium
Round 1
Reviewer 1 Report
The authors investigated the deformation behaviors of pure Iridium, varying temperatures and strain rates.
- L121 : In Equation (2), What is expC-C-1 ?
- L123 : Make it a form of the fraction notation.
- L169 Figure 7 : There is the gap at both ends and the center.Explain the cause of these gap.
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 1 Comments
Point 1: L121, in Equation (2), What is expC-C-1 ?
Response 1: Thanks for the reviewer’s suggestion. We are very sorry for incorrect writing of Equation (2). It should be and we have made correction and marked it in of the manuscript. (L 113)
Point 2: As for equations (1), (2), (4), (5), (6),(7), (9), (10), (12), (13), (14), make it a form of the fraction notation like A = !".
Response 2: Thanks for the reviewer’s suggestion. We have re-written these equations and marked in the manuscript according to the Reviewer’s suggestion. (L119, L137, L142, L146, L150, L154, L155, L169, L175, L199, L200, L219, L220, L239, L242, L246,)
Point 3: L169 Figure 7, there is the gap at both ends and the center. Explain the cause of these gap.
Response 3: Thanks for the reviewer’s suggestion. The gap at both ends and the center is caused by the larger interval of experimental deformation parameters (T,). Data points in Figure 1 are calculated by mathematic models mentioned in the manuscript. The distribution of these points is related to deformation parameters (T,) and peak stress (σp). Figure 1a shows, at the same deformation temperature (e.g. 1200oC, blue point), data points are nearly linear distribution and the point interval sizes are uniform. When the deformation temperature increases, this group points are moved to the lower left and the point interval sizes become enlarged. Because of the larger temperature interval (100oC), some points gather and the gap is occurred at both ends and the center. In addition, Figure 1b indicates that larger strain rate interval also can result in the gap.
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(a) |
(b) |
Figure 1. Relationship between ln[sinh(ασp)] and lnZ (a) Temperature; (b) Strain rate
Point 4: L145-146 Equation (5), explain a meaning of boundary condition called ασ=0.8. In addition, explain the derivation process of these two equations.
Response 4: Thanks for the reviewers’ suggestion. According to the view point of Liu et al. (Liu, J.W.; Zhao, Z.G.; Lu, S.Q. Microstructure evolution and constitutive equation for the hot deformation of LZ91 Mg alloy[J]. Catalysis Today 2018, 318: 119-125.) , in the low stress level, the relationship between stress σ and strain rate of different materials in plastic deformation process can be described as (1). In the high stress level, both A1 and n1 are full with power exponent relationship and can be expressed as (2). Similarly, the hyperbolic sine constitutive equation as (3) was established to describe the stable state deformation behavior. Where n is the stress exponent and α is a constant, which is full with α = β/n. Comparing Equations (1)-(3), in the low stress level (ασ < 0.8), Equation (3) is close to Equation (1), which shows the exponent relationship. Otherwise, in the high stress level (0.8 ≤ ασ <1.2), Equation (3) is close to Equation (2), which reflects the power exponent relationship. The constants α, β and n1 are full with α = β/n1. The natural logarithm of Equation (1) and (2) are used for solving materials constants β and n1. In addition, the meaning of boundary condition called ασ =0.8 and the derivation process of these two equations have been added to the manuscript and marked in it. (L143-155)
Point 5: The unit of activation energy of Iridium is J/(mol•K). However, the unit of activation energy of molybdenum and Ni super-alloy is J/mol. The unit is different from each other. What is correct unit?
Response 5 : We are very sorry for our negligence. The correct unit of activation energy of Iridium, Molybdenum and Ni super-alloy all is KJ/(mol•K). We have corrected and marked it in the manuscript. (L162, L163, L165)
Author Response File: Author Response.pdf
Reviewer 2 Report
In the manuscript presented, mechanical properties of iridium were investigated theoretically and experimentally. As soon as iridium is one of the rarest metals and extremely difficult to access as large bulk sample each investigation of mechanical properties is important for the community and gives relevant data for further progress of the field. #i recomend to publish work in the current form. I only suggest to discuss also properties of commercial bulk iridium samples as soon as in many cases iridium samples can be only prepared by hot pressing and hot rolling but not melting. Mechanical properties of such samples can be seriously different.
My main concern is about starting materials. Authors use Ir after floating zone melting which is good for characterisation of fundamental properties per ce. But Ir on the market not always made by melting and usually produced by hot rolling and hot pressing which might change its mechanical properties. I suggest to add comments about relevance of the melted Ir to understand properties of pressed Ir parts.
Authors give all necessary calculations which may be too detailed and might be cut off for clarity. At the same time I suggest to give more specific conclusions with several numerical points which might be used as reference information for further studies. I also suggest to give more reference data in tables or supplement. Readers could better extract solid information from the text in its table form.
Mechanical properties of refractory heavy metals were only sporadically investigated and any new information is important for the further progress. Current manuscript address important questions and is highly relevant in broader context. As minor comment I suggest to wright "iridium" or "Ir" in the sentence but not "Iridium".
Author Response
Response to Reviewer 2 Comments
Point 1: My main concern is about starting materials. Authors use Ir after floating zone melting which is good for characterisation of fundamental properties per ce. But Ir on the market not always made by melting and usually produced by hot rolling and hot pressing which might change its mechanical properties. I suggest to add comments about relevance of the melted Ir to understand properties of pressed Ir parts.
Response 1: Thanks for the reviewer’s suggestion. This is certainly that, in order to make reader understand the melted iridium more clearly, the fundamental properties are necessary. The density, relative density and microhardness of melted iridium have been added in Section 2.1. and marked in the manuscript according to the Reviewer’s comments. (L72-73)
Point 2: Authors give all necessary calculations which may be too detailed and might be cut off for clarity. At the same time I suggest to give more specific conclusions with several numerical points which might be used as reference information for further studies. I also suggest to give more reference data in tables or supplement. Readers could better extract solid information from the text in its table form.
Response 2: Thanks for the reviewers’ suggestion. The analysis of calculation model has been taken into account seriously, we believe that some cuts will lead to incomplete of the model, which make reader unable to apply it conveniently. There are similar expressions in the paper of Dong et al.’s (Dong, E.T.; Yu, W.; Cai, Q.W.; Cheng, L.; Ning, Z.; Shi, J. High-temperature deformation behavior of TiNi-Nb hypoeutectic alloy[J]. Materials Science and Engineering & A 2019,764:138228.) and Lin et al.’s. (Lin, Y.C.; Xia, Y.C.; Chen, X.M.; Cheng, M.S. Constitutive descriptions for hot compressed 2124-T851 aluminum alloy over a wide range of temperature and strain rate [J]. Computational Materials Science. 2010, 50(1): 227-233.) In addition, the most important information like microstructure evolution mechanisms under different deformation condition, hot deformation activation energy, the suitable processing window for hot forming of pure iridium have been presented in conclusion. Meanwhile, according to the Reviewer’s comments, we have added the compression yield strength (σs) under different deformation conditions and discussed its variation in Section 3.1(Figure 4d ) and Section 4.1 of the manuscript. (L125-127, L340-343)
Point 3: Mechanical properties of refractory heavy metals were only sporadically investigated and any new information is important for the further progress. Current manuscript address important questions and is highly relevant in broader context. As minor comment I suggest to wright "iridium" or "Ir" in the sentence but not "Iridium".
Response 3 : Thank you for your recognition of our work and we have modified the words in the manuscript according to Reviewer’s comments.
Author Response File: Author Response.pdf
Reviewer 3 Report
Title: Determination of constitutive equation and thermo-mechanical processing map for pure Iridium
Submitted manuscript entitled “Determination of constitutive equation and thermo-mechanical processing map for pure Iridium" described in details behavior of pure Iridium during thermal compression testing with the help of Gleeble thermo-mechanical simulator in the temperature range of 1200°C~1500°C and strain rate range of 10-1 s-1~10-2 s-1. Topic is interesting and I recommend it to publication. I think paper is written in good enough language. Technique, technology and research methods used in the work are adequate. Methods and obtained results prove founded thesis and show originality of the manuscript.
Some small revision of paper is needed.
Line 77, there is writing: “and1500°C)” missing spaces, should be writing: “and 1500°C)”
Line 78: heating rate of 20°C /s is very high even for so small samples like 6x9mm, so I wondering is temperature deviation was only during the heating time or also during the holding at the deformation temperature. Using heating rate of 20°C /s, I also wondering how much was overshooting during getting a deformation temperature. Why so high value of heating rate 20°C /s was set??, whether it has anything to do with the heating rate used for this type of material.
The flowchart shown on figure 1 it is not very well drawn, holding time before deformation is 60s, and after this time it should be mark deformation of the samples e.g. with a spring, also heating rate should be 20°C/s (seconds is missing)
Quality of the figure 2 is very poor and I think it should be corrected, the microstructure shown are not quite "sharp".
Figure 3, Has the sample before deformation shown in Figure 3b been stretched somehow? When we look at this figure it look that diameter is 6mm, but high of the samples looks it is about 12mm, once more longer then diameter, maybe it's just an illusion or maybe the effect of printing to PDF.
Quality of the graphs shown at figure 4 is very poor and I think it should be corrected, the graphs/lines shown are not quite "sharp" are blurry. When we look at the figures 5-10 those graphs are also very blurry, I think that maybe this is a problem of quality of printing to PDF file.
Generally topic is interesting, technique, and research methods used in the work are adequate. Methods and obtained results prove founded thesis and show originality of the manuscript.
Author Response
Response to Reviewer 3 Comments
Point 1: Line 77, there is writing: “and1500°C)” missing spaces, should be writing: “and 1500°C)”
Response 1 : Thanks for the reviewer’s suggestion. We are very sorry for incorrect writing. We have made correction and marked it in the manuscript according to the Reviewer’s comments. (L80)
Point 2: Line 78, heating rate of 20oC/s is very high even for so small samples like 6x9mm, so I wondering is temperature deviation was only during the heating time or also during the holding at the deformation temperature. Using heating rate of 20oC/s, I also wondering how much was overshooting during getting a deformation temperature. Why so high value of heating rate 20oC/s was set??, whether it has anything to do with the heating rate used for this type of material.
Response 2: Thanks for the reviewer’s suggestion. First of all, we consider that phase transformation will not take place during heating and thermal insulation for pure iridium, thus heating rate in this experiment may have a very small impact on results and we can ignore it. In addition, Chaudhuri et al. (Chaudhuri, A.; Sarkar, A.; Suwas, S. Investigation of stress-strain response, microstructure and texture of hot deformed pure molybdenum. International Journal of Refractory Metals and Hard Materials. 2018, 73, 168-182. ) have gotten an perfect experiment results by a heating rate of 20oC/s in the hot compression test of pure molybdenum. Finally, we chose the heating rate of 20oC/s. Temperature deviation was during heating time, which caused by the temperature unstability.Therefore, holding on 60s at deformation temperature is used to obtained the stable and homogenization temperature field for samples.
Point 3: The flowchart shown on figure 1 it is not very well drawn, holding time before deformation is 60s, and after this time it should be mark deformation of the samples e.g. with a spring, also heating rate should be 20°C/s (seconds is missing)
Response 3: Thanks for the reviewer’s suggestion. It is really true as Reviewer suggested and we have made correction (Figure 1) and marked it in the manuscript. The experiment process has been described more clearly than before. (L90)
Point 4: Quality of the figure 2 is very poor and I think it should be corrected, the microstructure shown are not quite "sharp".
Response 4: Thanks for the reviewer’s suggestion. We are very sorry for our negligence. We have corrected the figure 2b and marked it in the manuscript according to the Reviewer’s comments. (L99)
Point 5: Figure 3, Has the sample before deformation shown in Figure 3b been stretched somehow? When we look at this figure it look that diameter is 6mm, but high of the samples looks it is about 12mm, once more longer then diameter, maybe it's just an illusion or maybe the effect of printing to PDF.
Response 5: Thanks for the reviewer’s suggestion. We are very sorry for our negligence of the picture’s distortion in Figure 3b and we have made correction and marked it in the manuscript. (L109)
Point 6: Quality of the graphs shown at figure 4 is very poor and I think it should be corrected, the graphs/lines shown are not quite "sharp" are blurry. When we look at the figures 5-10 those graphs are also very blurry, I think that maybe this is a problem of quality of printing to PDF file.
Response 6: Thanks for the reviewer’s suggestion. We have made the sharper Figures in the manuscript according to the Reviewer’s comments. ( L128, L176, L177, L179, L201, L221, L224 )
Author Response File: Author Response.pdf
