Effect of Cooling Rate on Microstructure and Properties of Twin-Roll Casting 6061 Aluminum Alloy Sheet

Round 1

Reviewer 1 Report

The examined conditions of the casting-rolling process are of fundamental importance. Unfortunately, the authors do not provide any reliable figures regarding precipitation size, grain size and their distribution. For the modelling, crystallographic orientations in the interface between matrix and precipitation and more precise statements on the structural change of the precipitated phases with different cooling rates and precipitation sizes are also of interest. The results presented are as expected and do not provide any significant scientific contribution. It is recommended to extend the presentation of the investigations and to provide reliable figures for the modelling. The investigation methods used allow a significantly deeper analysis than indicated. Figures 1-5 show typing errors.

Author Response

Answers: The whole article has been revised and improved, including “Introduction”, “Experimental procedures”, some performance data processing and so on. Figures 1-5 have been modified as well.

Reviewer 2 Report

The manuscript (MS) focuses on the impact of applying different cooling rates during the solidification of the 6061 aluminum alloy. OM, SEM and XRD were used to analyze microstructural evolution. Mechanical properties of this alloy at various conditions were obtained utilizing hardness measurement and tensile testing. Obtained mechanical properties and microstructural analysis are interesting for researchers and readers. The introduction of the current manuscript needs to be improved. Many papers focusing on the cooling rate and solidification in aluminum alloys. The authors should refer to previously published papers. Besides, the authors should emphasize the novelty of present research work. It should also be noted that in the experimental procedure, some details regarding mechanical testing are missing. The missing points should be added to the text. Below, there are some comments which need to be addressed before publication:

 

Lines 27-48: “Introduction” section of the present research work is very short and brief. The authors should emphasize the novelty of present research compared to the previous ones. There are several recent studies on the aluminum alloys that can be cited and discussed. Some examples can be seen below:

• Benjunior et al., Effect of Different Cooling Rates Condition on Thermal Profile and Microstructure of Aluminium 6061, Procedia Engineering 184 (2017) 298–305. https://doi.org/10.1016/j.proeng.2017.04.098.
• Jatimurti et al., Effect of Degassing Time and Cooling Rate on Microstructure and Porosity of Aluminum 6061 Alloy Using Sand Casting Method, Materials Science Forum 964 (2019) 124-129. https://doi.org/10.4028/www.scientific.net/MSF.964.124.
• V. Sajadifar et al., Performance of Thermo-Mechanically Processed AA7075 Alloy at Elevated Temperatures—From Microstructure to Mechanical Properties, Metals 10 (7) (2020) 884-.                 https://doi.org/10.3390/met10070884.
• G. Shabestari and M. Malekan, Thermal analysis study of the effect of the cooling rate on the microstructure and solidification parameters of 319 aluminum alloy Canadian Metallurgical Quarterly, 44 (3) (2005) 305-312. https://doi.org/10.1179/cmq.2005.44.3.305.
• V. Sajadifar et al., Effect of Tool Temperature on Mechanical Properties and Microstructure of Thermo-Mechanically Processed AA6082 and AA7075 Aluminum Alloys, HTM Journal of Heat Treatment and Materials 75 (3) (2020) 177-191. https://doi.org/10.3139/105.110412.
• V. Sajadifaret al., On the Effect of Quenching on Postweld Heat Treatment of Friction-Stir-Welded Aluminum 7075 Alloy, Journal of Materials Engineering and Performance 28 (2019) 5255-5265. https://doi.org/10.1007/s11665-019-04252-3.

Lines 49-69: Some details should be added to the “Experimental procedure” before publication.

• There are no details regarding tensile testing. What was the geometry of samples for tensile testing? Were the experiments carried out at ambient temperature? How many tensile experiments were conducted per condition? What were the standard deviations?
• In hardness measurements, what were the load and duration for each indentation? How many indents were conducted per condition? What were the standard deviations?

Some minor comments:

The English of the manuscript is good although some points need to be modified before publication. An example can be seen below:

Lines 18-20: The authors stated, “The results show that the larger the cooling rate, the smaller the grain size of the alloy and the smaller the number of precipitated phases in the matrix.” The adjectives “larger and smaller” are not appropriate for the cooling rate. Researchers usually use “higher and lower cooling rates”. I suggest the authors use higher and lower throughout the text.

 

Lines 158 and 159: The scale bar should be corrected in Fig. 9a. It is hardly readable in the submitted PDF file.

Lines 224 & 225: Standard deviations should be reported for the yield point, tensile strength and elongation.

Author Response

The manuscript (MS) focuses on the impact of applying different cooling rates during the solidification of the 6061 aluminum alloy. OM, SEM and XRD were used to analyze microstructural evolution. Mechanical properties of this alloy at various conditions were obtained utilizing hardness measurement and tensile testing. Obtained mechanical properties and microstructural analysis are interesting for researchers and readers. The introduction of the current manuscript needs to be improved. Many papers focusing on the cooling rate and solidification in aluminum alloys. The authors should refer to previously published papers. Besides, the authors should emphasize the novelty of present research work. It should also be noted that in the experimental procedure, some details regarding mechanical testing are missing. The missing points should be added to the text. Below, there are some comments which need to be addressed before publication:

Lines 27-48: “Introduction” section of the present research work is very short and brief. The authors should emphasize the novelty of present research compared to the previous ones. There are several recent studies on the aluminum alloys that can be cited and discussed. Some examples can be seen below:

Benjunior et al., Effect of Different Cooling Rates Condition on Thermal Profile and Microstructure of Aluminium 6061, Procedia Engineering 184 (2017) 298–305. https://doi.org/10.1016/j.proeng.2017.04.098.

Jatimurti et al., Effect of Degassing Time and Cooling Rate on Microstructure and Porosity of Aluminum 6061 Alloy Using Sand Casting Method, Materials Science Forum 964 (2019) 124-129. https://doi.org/10.4028/www.scientific.net/MSF.964.124.

10. Sajadifar et al., Performance of Thermo-Mechanically Processed AA7075 Alloy at Elevated Temperatures—From Microstructure to Mechanical Properties, Metals 10 (7) (2020) 884-.                 https://doi.org/10.3390/met10070884.
11. Shabestari and M. Malekan, Thermal analysis study of the effect of the cooling rate on the microstructure and solidification parameters of 319 aluminum alloy Canadian Metallurgical Quarterly, 44 (3) (2005) 305-312. https://doi.org/10.1179/cmq.2005.44.3.305.
12. Sajadifar et al., Effect of Tool Temperature on Mechanical Properties and Microstructure of Thermo-Mechanically Processed AA6082 and AA7075 Aluminum Alloys, HTM Journal of Heat Treatment and Materials 75 (3) (2020) 177-191. https://doi.org/10.3139/105.110412.
13. Sajadifaret al., On the Effect of Quenching on Postweld Heat Treatment of Friction-Stir-Welded Aluminum 7075 Alloy, Journal of Materials Engineering and Performance 28 (2019) 5255-5265. https://doi.org/10.1007/s11665-019-04252-3.

Answers: “Introduction” section has been reorganized and overall enriched by summarizing research findings in this field, adding several references.

Lines 49-69: Some details should be added to the “Experimental procedure” before publication.

There are no details regarding tensile testing. What was the geometry of samples for tensile testing? Were the experiments carried out at ambient temperature? How many tensile experiments were conducted per condition? What were the standard deviations?

In hardness measurements, what were the load and duration for each indentation? How many indents were conducted per condition? What were the standard deviations?

Answers: The dimensional drawing of tensile specimens has been insert in the “Experimental procedures” part. The mechanical properties were measured at room temperature(20℃) with a strain rate of 1mm/min. The hardness was measured with a test load of 3N and a dwell time of 15 seconds. In addition, all the tests results were averaged from three effective values, and the error bars have been added in the results. The whole“Experimental procedures” part has been modified.

Some minor comments:

The English of the manuscript is good although some points need to be modified before publication. An example can be seen below:

Lines 18-20: The authors stated, “The results show that the larger the cooling rate, the smaller the grain size of the alloy and the smaller the number of precipitated phases in the matrix.” The adjectives “larger and smaller” are not appropriate for the cooling rate. Researchers usually use “higher and lower cooling rates”. I suggest the authors use higher and lower throughout the text.

Answers: “larger and smaller”, which are used to describe cooling rate, have been replaced with “higher and lower” throughout the text

Lines 158 and 159: The scale bar should be corrected in Fig. 9a. It is hardly readable in the submitted PDF file.

Answers: The scale bars in Fig. 9 have been re-edited.

Lines 224 & 225: Standard deviations should be reported for the yield point, tensile strength and elongation.

Answers: All the tests results were averaged from three effective values, and the error bars have been added in the results.

Reviewer 3 Report

English is not suitable for publication. The text contains numerous grammatical and lexical errors. The punctuation and use of the articles "a /an" and "the" are especially bad. The paper can only be printed after proper proofreading.

Author Response

English is not suitable for publication. The text contains numerous grammatical and lexical errors. The punctuation and use of the articles "a /an" and "the" are especially bad. The paper can only be printed after proper proofreading.

Answers: Our manuscript has been checked by a native English speaking colleague, especially for the point of "a, an and the". All the changes we have made have been marked in red

Round 2

Reviewer 2 Report

The authors successfully addressed my comments. 

Author Response

Answers: Thank you very much for your fair, professional and meticulous review of our papers. We learned a lot during the process of revising paper. In addition, the English language and style of our paper has further improved.

Reviewer 3 Report

The article contains typos that need to be corrected, for example: there are typos in the reference to the literature in items 1, 2, 3. Incorrect punctuation marks were found in the text. Requires a thorough check of the text before printing.

Author Response

Answers: Thank you very much for your fair, professional and meticulous review of our papers.

Errors in references (1, 2 and 3) have been changed. We have checked the text thoroughly, including grammar, diction, chart, format, and punctuation.