Early Stages of Plastic Deformation in Low and High SFE Pure Metals

Round 1

Reviewer 1 Report

The article is devoted to the study of the evolution of microstructure and microhardness in pure metals at the early stages of severe plastic deformation realized by torsion under high pressure. Copper with a low stacking fault energy (SFE) and aluminum with a high SFE were selected as objects for comparative studies.

The authors performed the analysis at a high methodological level, applied simulations to analyze the contribution of various parameters to the strength of the studied materials at various stages of deformation.

Disadvantages:

Copper with a purity of 99.99% and aluminum with a purity of 99.9999% were selected for research, but the choice of materials based on the level of contamination is not justified.

The choice of such different ranges of degrees of deformation (Cu - from 0.40 to 1.21, Al - from 0.02 to 0.10) for the comparative study of materials is not justified.

The role of high pressure in the evolution of microstructure and microhardness in high pressure torsion is not discussed.

The possibility of slippage during at HPT is not specified and controlled.

The reasons for comparative analysis of microstructures of the materials under study for different distances from the axis of rotation are not specified. It is unclear what was the crystallographic orientation of the grains for which statistics were recruited, how representative was the statistics of given grain orientation.

The authors neither controlled nor discussed the role of vacancies and diffusion processes during the evolution of microstructure at deformation under applied high pressure.

The authors do not discuss the influence of high purity of metals on the recovery in the course of HPT.

The authors do not discuss the importance of regularities for the subsequent formation of increased properties of the studied materials at later stages of the HPT.

Line 158 uses the SSD and GND designations, which are introduced much later in the text.

In line 167, the GBS designation is entered without decryption.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper presents very interesting fundamental studies,  which focus on a comparison of two pure alloys with different SFE after  SPD deformation by means of HPT. 

Paper is clearly written and well organized. 

Some comments below:

1) My suggestion is to split Figure 2 into two separate figures for each alloy. It will improve visibility. I would like to recommend to add exemplary Kikuchi patterns for each material. 

2) Table 5 is not clearly presented - possible wrong data for strain levels for 6NAl

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Very nice work and paper

Author Response

Not need to be replied.