High-Pressure Torsion for Synthesis of High-Entropy Alloys

Round 1

Reviewer 1 Report

The paper is acceptable for publication with some english corrections.

Mostly article mistakes, omitted articles,... really a lot of them.

The necessary corrections are as comments in the pdf.: Red are deletes, Green inserts, Yellow questions/comments.

Comments for author File: Comments.pdf

Author Response

Please see the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Although the HPT method has long been known and used to obtain interesting nonequilibrium microstructures and related properties, the present work contains useful information as well. A review of different in composition and nature high entropy materials (HEAs)  obtained by SPD / HPT and exhibiting attractive properties, such as high mechanical strenght, hydrogen storage capacity, electrocatalysts for Hydrogen production , light absorbers, etc. Important studies of a number of authors who have used in recent years SPD methods for the synthesis of new functional materials are cited.

In conclusion, I think that the article contains useful information and can be published in Metals.

Before that, however, the following notes should be addressed:

• It is good to rewrite the abstract. The first 3 sentences are unclear.
• Purpose: …the main achievement are reviewed (not is reviewed). Please, replace ”achieving” in the same sentence.
• 4 - to stretch the abscissa.
• There is generally some negligence in writing. Examine the text once more.

Comments for author File: Comments.pdf

Author Response

Please see the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper under review is devoted to a review of the state of the art in the synthesis of high-entropy alloys (HEAs) for the production and storage of hydrogen. HEAs were synthesized using the high-pressure torsion (HPT) method of severe plastic deformation (SPD).

The paper is well organized, structured, written in a clear and literate scientific language.

Notes:

The paper argues that as a result of the HPT it is possible to achieve high shear strains over 1,000. At the same time, the thickness of the deformable blanks becomes very small and, in order to achieve by sheared phases of the very small thickness, the use of open heads without grooves is required. Moreover, a diagram of the implementation of the HPT with heads having grooves is presented in Fig. 1.

The paper does not explain what is the physical meaning of the shear strains over 1,000? There is no explanation why such high degrees of deformation lead to the consolidation of deformable blanks. The role of pressure, temperature, strain rate, and dynamic recrystallization processes during HPT is not discussed.

HPT leads to the formation of nanosized grains, which are responsible for high strength, even after degrees of deformation equal to 10-100. Why does an increase in the degree of deformation to values ​​above 1000 lead to an increase in strength if the grain size does not change? If this is associated with an increase in configurational entropy, then appropriate quantitative estimates, evidence and explanations should be provided.

HPT with very large shear deformations over 1000 requires very large energy and time costs, leads to wear of the heads. How is this problem supposed to be solved?

What is the principle of choosing chemical elements and their percentage to obtain optimal properties? How to achieve the optimal alloy composition?

What is the reason for the influence of HPT on hydrogen storage and production properties?

What parameter of the structure formed as a result of HPT is critical for increasing the ability to store or produce hydrogen? How do the HPT parameters affect these properties?

What are the next steps in the research of HEAs using HPT?

Comments for author File: Comments.pdf

Author Response

Please see the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The authors of the article fully took into account the comments made. The article is recommended for publication.