Effect of Carbon Content in Retained Austenite on the Dynamic Tensile Behavior of Nanostructured Bainitic Steel
Round 1
Reviewer 1 Report
The paper is well written and presents interesting results. The following comments are given by the reviewer:
- Abstract and Conclusions: Should be supported with quantitative data.
- Dynamic tensile testing set-up: For quasi-static tensile tests, usually standardised specimen geometries with a defined initial measurement length apply. The strain is thereby measured with an extensiometer. On which basis is the presented specimen geometry defined and why is not an extensiometer used for a comparative strain measurement?
- Figure 5: In line 84 it is stated that two samples for each strain rate are used. Why is only one curve shown for each test and not two? How much is the scattering between the two tests for each strain rate?
Author Response
Response to Reviewer Comments
Point 1: Abstract and Conclusions: Should be supported with quantitative data.
Response 1: It has been revised in the text according to the review comments.
Point 2:Dynamic tensile testing set-up: For quasi-static tensile tests, usually standardised specimen geometries with a defined initial measurement length apply. The strain is thereby measured with an extensiometer. On which basis is the presented specimen geometry defined and why is not an extensiometer used for a comparative strain measurement?
Response 2: A servo-hydraulic high speed tensile testing machine (Zwick HTM 5020) was used to conduct the dynamic tensile test. Standard: ISO26203-2. Metallic materials-Tensile testing at high strain rates-Part2:Servo-hydraulic and other test systems.
We cut the samples according the ISO26203-2 and the Zwick HTM 5020 machine.
Point 3: Figure 5: In line 84 it is stated that two samples for each strain rate are used. Why is only one curve shown for each test and not two? How much is the scattering between the two tests for each strain rate?
Response 3: we choose one sample because the two curves for each test are near, and we use the table to represent the average value and standard deviation of each value. the standard deviation is not too big.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is a significant paper on an important subject and should be published.
Specific suggestions: On line 45 Ms presumably means martensitic start temperature (which isn't defined until line 66)---or is it short for mechanical stability?; this should be made explicit.
How are the values of Ms in Table 1 reconciled with the much lower numbers for austenite in line 212? Presumably the compositions differ; please explain.
On lines 45--46, please explain the relation between the effect of carbon content on mechanical stability and the dependence of Ms on chemical composition.
Author Response
Response to Reviewer Comments
Point 1: On line 45 Ms presumably means martensitic start temperature (which isn't defined until line 66)---or is it short for mechanical stability?; this should be made explicit.
Response 1: It has been revised in the text according to the review comments.
Point 2:How are the values of Ms in Table 1 reconciled with the much lower numbers for austenite in line 212? Presumably the compositions differ; please explain.
Response 2: Table 1 is for the steel, in line 212, Assuming that all alloying elements except carbon were homogeneously distributed during slow cooling, isothermal process . we just use the MS for different austenite stability. Because there carbon different for different austenite , there MS different and the lower Ms , the higher stability of the austenite.
Point 3: On lines 45--46, please explain the relation between the effect of carbon content on mechanical stability and the dependence of Ms on chemical composition.
Response 3: . Carbon enrichment of the austenite during intercritical annealing and bainite transformation was very effective in retaining austenite.
C is the most important value for Ms.
when the temperature goes below Ms, the RA is not thermally stable and transforms to martensite without plastic straining. At temperatures above Ms, the RA is not mechanically stable, and may transform to martensite with plastic
the lower Ms , the higher stability of the austenite.
So MS IS the improtant value for stablity.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors investigated the effects of the carbon content in retained austenite on dynamic tensile properties in a nanostructured bainitic steel. There are fruitful results.
(1) In Table 3, the EI of Q&P gradually increased with increasing he strain rate. On the contrary, the EI of B3 at the strain rate of 100 s-1is larger than that of 50 , 200 and 500 s-1. Please explain why becomes so.
(2) Please make a figure of the strain rate vs. UTS × EI in Table 3 for each treatment.
(3) Please indicate the meaning of Ms (L45) and Q&P (L59) in the sentence. The meaning of each word was written in the later chapter.
(4) Please make expression of the strain rate equivalence, s-1or /s. I think s-1is better. In Figure 5 (a), please change 200s/s to 200 s-1or 200 /s.
Author Response
Response to Reviewer Comments
Point 1: In Table 3, the EI of Q&P gradually increased with increasing he strain rate. On the contrary, the EI of B3 at the strain rate of 100 s-1is larger than that of 50 , 200 and 500 s-1. Please explain why becomes so.
Response 1: it indicate the plastic is better in 100 s-1. And considering a comprehensive property , 100 and 500 s-1 are both good and all are high than QP sample at the same strain rate
Point 2:Please make a figure of the strain rate vs. UTS × EI in Table 3 for each treatment.
Response 2: we have make three figures before ,and we did not use it because we use table replace it
Point 3: Please indicate the meaning of Ms (L45) and Q&P (L59) in the sentence. The meaning of each word was written in the later chapter.
Response 3: It has been revised in the text according to the review comments.
Point 4: Please make expression of the strain rate equivalence, s-1or /s. I think s-1is better. In Figure 5 (a), please change 200s/s to 200 s-1or 200 /s..
Response 4: It has been revised in the text according to the review comments.
Author Response File: Author Response.pdf
