Microstructure Evolution in a GOES Thin Strip

Round 1

Reviewer 1 Report

The evolution of microstructures has been analyzed at great length in this paper, and the results are plentiful.

1.  The authors need to improve the introduction to include the effect of microstructures on mechanical properties.

2.  How to determine whether the black shape in Fig. 1 is the non-parallel needle-shaped products of austenite decomposition?

3.  Please add color bars for IPF maps.

4.  In Fig.2-Fig.7, microstructures were characterized by optical microscopy. can EDS measurements be performed to identify specific elements in various structures?

Author Response

We would like to thank to the reviewer for expert comments on our manuscript.

The brief answers to the questions are as follows:

1. The effect of microstructure on the mechanical properties.

Decisive properties of GOES sheets are magnetic properties. They depend strongly on the “sharpness” of the Goss texture. In order to control the final texture it is believed that microstructural evolution during processing of GOES is very important. Our paper deals with microstructure evolution in the two-phase (gamma + delta) region and at temperatures below this region. Mechanical properties in magnetically soft materials are not intensively monitored. Information about mechanical properties of GOES in the two-phase region are not publicly available and they are not important from the point of view of practical applications of GOES sheets.

2. How to determine that the black needles are products of austenite decomposition?

GOES primarily solidifies as delta ferrite. Light microscopy revealed that black needles are formed either by pearlite or by a mixture of plate martensite and retained austenite. The only way how could these products appear in the ferritic matrix is the formation of austenite in the two-phase region and subsequent decomposition of austenite to pearlite or plate martensite. These transformations occur at high temperatures and are accompanied by intensive redistribution of carbon – both products of austenite decomposition are close to the eutectoid composition. Morphology of austenite decomposition products proves that the dominant morphology of austenite corresponded to Widmanstätten laths.

3. It has been done.
4. Can EDS measurements be performed to identify specific elements in various structures?

Contents of substitutional elements in products of WA decomposition (pearlite, plate martensite, retained austenite, epitaxial ferrite) are almost the same as in the delta ferrite matrix. Differences in carbon content are large but they cannot be reliably characterized by EDS.

Reviewer 2 Report

The paper presents the characterization of the evolution of microstructure in a grain-oriented electrical steel thin strip after casting. The paper is clearly written and very well organized with enough references to understand the work.

The issues that I recommend the authors to address before submitting the paper are listed below:

Line 62: meaning of WDX

Line 107: Could you please explain the carbon replica preparation methodology?

Lines 119-122: Indicate these regions in the corresponding image

Line 149: Fig 1b (indicate in the image the nucleation sites)

Lines 158-160: Indicate in the image (martensite, retained austenite, perlite)

Lines 208-209: Explain the diffraction pattern shown in Fig 9b

Lines 261-262: Indicate in the figure.

Author Response

We would like to thank to the reviewer for expert comments on our manuscript.

Our  answers to recommendations and questions are as follows:

1. Line 62: Meaning of WDX

We have added the full name of the method:

..wave dispersive X – ray (WDX) microanalysis……

2. Line 107: Carbon replica preparation methodology

.. An etched metallographic sample was coated with a carbon layer with a thickness of 12 nm. Electrolytic etching in a 7% HNO₃ solution in alcohol was applied for releasing of the carbon film from the substrate. The carbon film with minor phase particles was stripped to the water surface and after a thorough rinse in water, pieces of the carbon film were fished out on the backing grid.

3. Lines 119- 122: It has been accepted.
4. Line 149: It has been accepted.
5. Lines 158 – 160: Text fields with names of constituents/phases have been added.
6. Lines 208 – 209: Indexing of spots in the spot diffraction pattern in Fig. 9b has been done.
7. Lines 261 – 262: Retained austenite in the phase map is green – it is clearly defined in the caption.