High-Temperature Mechanical Behavior of an As-Extruded Al-5Zn-2Mg-0.3Cu (in wt.%) Alloy

Round 1

Reviewer 1 Report

The authors made a huge work and interested paper. Nevertheless, I would like to ask following:

1. I did not see what instruments were used during the work. Please, add

2. The authors did not give the name of the alloy producer

3. The authors did not describe ICP-MS analysis (how the alloy was dissloved and analyzed); how much is Al content? ~92%?

4. The quality of Figure 7 and Figure 8 is very poor. It must be improved

5. In Lines 170-182 were described microfractures. I do not see good explanations of their formation during the testings

The authors used a very recent literature.  

Author Response

The authors made a huge work and interested paper. Nevertheless, I would like to ask following:

1. I did not see what instruments were used during the work. Please, add

Response: Thanks for your comment. We have added the instruments in the experimental section.

2. The authors did not give the name of the alloy producer

Response: Thanks for your comment. We have added the name of the alloy producer in the experimental section.

3. The authors did not describe ICP-MS analysis (how the alloy was dissolved and analyzed); how much is Al content? ~92%?

Response: Thanks for your comment. The chemical composition analysis was conducted by the testing center of our institute. We just send the sample to them and they conduct the testing. Thus, we do not know how the alloy was dissolved and analyzed. Based on the measured result, the content of Al of the alloy is 91.18%. We have revised the Table 1 accordingly.

4. The quality of Figure 7 and Figure 8 is very poor. It must be improved

Response: Thanks for your comment. We have revised the Figure 7 and Figure 8.

5. In Lines 170-182 were described microfractures. I do not see good explanations of their formation during the testings

Response: Thanks for your comment. The formation of crack formation is closely related to the cracking of brittle α-Al₁₅(MnFe)₃Si₂ phase particles. The relevant explanations of their formation are provided in the Section 4.2.

Reviewer 2 Report

The article examines the mechanical properties and failure mechanisms of a commercially obtained 7N01 Al alloy at elevated temperatures. Tensile testing was performed at relatively high homologous temperatures, after which the fracture surfaces were investigated for determining the main crack propagation. The investigation methodology is well presented. Some aspects of the investigation may be improved:

1. The quality of the images in Figure 8 is quite poor and needs to be improved for better visibility. The images should also be marked as surfaces 2mm and 5mm from the fracture surface, as well as with the tensile testing temperature. It is not very clear which surfaces these are on the tensile testing sample. A visual model of the sample with marked investigated surfaces would improve clarity.

2. Only cracks within the brittle α-phase particles are seen in the provided SEM images, while cracks at the particle/matrix interface are also discussed in the conclusions. What is the proportion of these two types of cracking with regards to the testing temperature? Is it possible to determine the dominant cracking mechanism for the investigated temperatures?

3. What is the argument for choosing to investigate surfaces that are 2 and 5 mm from the fracture surface? Is there a difference in the cracking between these investigated surfaces, which is not presented in the discussion (number of cracks, type of cracks – in the brittle particles, or on the particle/matrix interface, etc.)?

Author Response

The article examines the mechanical properties and failure mechanisms of a commercially obtained 7N01 Al alloy at elevated temperatures. Tensile testing was performed at relatively high homologous temperatures, after which the fracture surfaces were investigated for determining the main crack propagation. The investigation methodology is well presented. Some aspects of the investigation may be improved:

1. The quality of the images in Figure 8 is quite poor and needs to be improved for better visibility. The images should also be marked as surfaces 2mm and 5mm from the fracture surface, as well as with the tensile testing temperature. It is not very clear which surfaces these are on the tensile testing sample. A visual model of the sample with marked investigated surfaces would improve clarity.

Response: Thanks for your comment. We have marked the distance from the fracture surface and the testing temperature in Figure 8.

2. Only cracks within the brittle α-phase particles are seen in the provided SEM images, while cracks at the particle/matrix interface are also discussed in the conclusions. What is the proportion of these two types of cracking with regards to the testing temperature? Is it possible to determine the dominant cracking mechanism for the investigated temperatures?

Response: Thanks for your comment. It is difficult to determine the numbers and proportion of these two types of cracking with regards to the testing temperature because only one side of surface of different samples was observed. Although two types cracking modes can be observed on the surfaces of tensile tested samples, it is hard to determine whether they are the dominant cracking mechanisms because no crack propagation around these two types of initiated cracks can be observed.

3. What is the argument for choosing to investigate surfaces that are 2 and 5 mm from the fracture surface? Is there a difference in the cracking between these investigated surfaces, which is not presented in the discussion (number of cracks, type of cracks – in the brittle particles, or on the particle/matrix interface, etc.)?

Response: Thanks for your comment. The reason for choosing to investigate surfaces that are 2 and 5 mm from the fracture surface has been added in Section 2.4. In addition, the difference in the cracking between these investigated surfaces has been added in the Section 4.2.

Reviewer 3 Report

(1) The abstract effectively communicates the significant findings, precisely the temperature-dependent mechanical properties of the Al-5Zn-2Mg-0.3Cu alloy. This information is crucial for understanding the scope and importance of the study.

(2) The mention of ductile dimples on fracture surfaces and necking during testing provides essential insights into the material's behavior. However, it would be beneficial to elaborate on the implications of these observations, such as their relevance to material design or practical applications.

(3) The explanation of microcrack initiation due to the self-cracking of brittle phase particles and at the interface with the Al matrix is valuable. It helps readers understand the root causes of material failure, but consider expanding on how this information contributes to the broader field of materials science.

(4) The abstract is generally concise. Still, you might explore opportunities to further condense sentences related to mechanical properties at different temperatures, ensuring the abstract remains brief while conveying all necessary information.

(5) Including a sentence about potential future research directions or practical implications of the findings would enhance the conclusion's completeness and help readers see the broader context of the study.

(6) Make sure to check and include any necessary references in the abstract, mainly if the study builds upon previous work or methodology from other sources.

(7) Proofread the manuscript carefully for language and grammar issues.

(8) To provide a more comprehensive understanding of the corrosion behavior of the Al-7000 series alloy studied in this manuscript, I recommend that the authors consider citing relevant papers investigating the corrosion properties of aluminum 7000 series alloys in the introduction. This would strengthen the background information and contextualize the current study within the existing literature on this alloy series: https://doi.org/10.1016/j.matpr.2018.04.177; https://doi.org/10.3390/ma15010360.

Minor editing of English language required!

Author Response

• The abstract effectively communicates the significant findings, precisely the temperature-dependent mechanical properties of the Al-5Zn-2Mg-0.3Cu alloy. This information is crucial for understanding the scope and importance of the study.

Response: Thanks for your comment. We have modified the abstract accordingly.

• The mention of ductile dimples on fracture surfaces and necking during testing provides essential insights into the material's behavior. However, it would be beneficial to elaborate on the implications of these observations, such as their relevance to material design or practical applications.

Response: Thanks for your comment. We have added their relevance to the microstructure.

• The explanation of microcrack initiation due to the self-cracking of brittle phase particles and at the interface with the Al matrix is valuable. It helps readers understand the root causes of material failure, but consider expanding on how this information contributes to the broader field of materials science.

Response: Thanks for your comment. We have added more information in the Section 4.2.

• The abstract is generally concise. Still, you might explore opportunities to further condense sentences related to mechanical properties at different temperatures, ensuring the abstract remains brief while conveying all necessary information.

Response: Thanks for your comment. We have revised the abstract and make it concise.

• Including a sentence about potential future research directions or practical implications of the findings would enhance the conclusion's completeness and help readers see the broader context of the study.

Response: Thanks for your comment. We have added a sentence about potential future research directions.

• Make sure to check and include any necessary references in the abstract, mainly if the study builds upon previous work or methodology from other sources.

Response: Thanks for your comment. We have checked it.

• Proofread the manuscript carefully for language and grammar issues.

Response: Thanks for your comment. We have modified the grammar mistakes.

• To provide a more comprehensive understanding of the corrosion behavior of the Al-7000 series alloy studied in this manuscript, I recommend that the authors consider citing relevant papers investigating the corrosion properties of aluminum 7000 series alloys in the introduction. This would strengthen the background information and contextualize the current study within the existing literature on this alloy series: https://doi.org/10.1016/j.matpr.2018.04.177; https://doi.org/10.3390/ma15010360.

Response: Thanks for your comment. We have added these two reference papers.

Reviewer 4 Report

- Long title, please shorten.

- First two or three sentences in Abstract should be about topic itself. Reader should get clue about topic generally.

- In abstract should be mention motivation for this research.

- In the end of Introduction should be describe novelty of this manuscript. Also usage in praxe, in what kind of industries?

- In Fig. 6 should be clear that it is detail of first picture.

- Name of Fig. 8 is weird. Please make (a), (b)... mor clear.

- Green text in Fig. 8 is not readable.

- There is not written ISO norm for tensile testing and also none for tensile specimen.

 

Author Response

1. Long title, please shorten.

Response: Thanks for your comment. We have shortened the title into “High temperature mechanical behavior of an as-extruded Al-5Zn-2Mg-0.3Cu (in wt.%) alloy”.

2. First two or three sentences in Abstract should be about topic itself. Reader should get clue about topic generally.

Response: Thanks for your comment. We have modified the abstract accordingly.

3. In abstract should be mention motivation for this research.

Response: Thanks for your comment. The motivation of this research has been added in the abstract.

4. In the end of Introduction should be describe novelty of this manuscript. Also usage in praxe, in what kind of industries?

Response: Thanks for your comment. We have added the novelty and the usage of obtained data in the end of Introduction.

5. In Fig. 6 should be clear that it is detail of first picture.

Response: Thanks for your comment. We have added the description about the locations of high magnification images in the low magnification images accordingly.

6. Name of Fig. 8 is weird. Please make (a), (b)... mor clear.

Response: Thanks for your comment. We have modified it.

7. Green text in Fig. 8 is not readable.

Response: Thanks for your comment. We have modified it.

8. There is not written ISO norm for tensile testing and also none for tensile specimen.

Response: Thanks for your comment. The samples used in the experiment are non-standard samples. Due to the limitation of the tensile testing machine and the equipped high temperature environmental furnace, the standard sample is not suitable.

 

 

Round 2

Reviewer 1 Report

Since the authors have obeyed all reviewer's comments, I would like to suggest acceptance of the paper. 

Reviewer 3 Report

The authors corrected the paper following the reviewer's advice and improved the quality of the manuscript. It can be accepted as it is.

Reviewer 4 Report

Author improved his manuscript.