I think electro-polishing is suite for this steel and also cheap, convenient.

Hi. Different steps of mechanical polishing were discussed by detail in this paper. Ion milling and electropolishing are also suitable as post mechanical polishing process.

Dear Kaixuan Gu ,

Thanks for your response. In the following, do you aware of voltage and time quantity during high- strength low- alloyed steel electro-polishing? also about the solution combination of electrolytic?

Dear Maryam Soleimani ,

Thanks for your response, it was very helpful. Although, have you ever heard about light- etch light- polishing method?

The Kikuchi lines tend to be more clear when the surface has no deformation, so the polishing must be light and gentle. Diamond and colloidal silicon polishing are suitable. Even if after these methods you were unable to get Kikuchi pattern, the light etch with Nital for low carbon steel is helpful. Also the solution for electropolishing is 40% perchloric acid and 60% Ethanol.

Dear Maryam Soleimani ,

The mentioned solution for electropolishing tried and the surface became mostly dull. Our first suggestions were to reduce the percent of perchloric up to 4%, although the dull surface remained. Do you know a new solution for electropolishing? and in your opinion can we consider skipping the electropolishing part and only focus on light- etch light- polishing?

For low carbon steel, this solution is common. But some parameters like temperature, time, voltage and current can be changed. This papers also may be helpful.

Dear Mr. Amirjani,

I recommend studying the latest version of the ASTM E1558: '''Standard Guide for Electrolytic Polishing of Metallographic Specimens''.

A solution consisting of 20 vol.% HClO4 and 80 vol.% C2H5OH was successfully applied in our study on a similar type of steel with the following conditions:

• Solution temperature: approximately 25 C
• Voltage: 15 V
• Current density: approximately 10 mA/mm2
• Electropolishing time: 1 min

Immediately clean the electropolished samples in an ultrasonic bath containing C3H6O for 1 min. When you observe the prepared samples by an optical microscope you probably would see a bright very-light-etched surface without scratches, which seems good for EBSD characterizations.

Try to polish the samples mechanically before the electropolishing process to get much better results, although you may jump directly from a fine grinding step.

The proper conditions in your case of study will be attained by some trial and error experiments.

I hope you find the comments useful.

Sincerely,

Amir Sabet

Dear Amir Sabet Ghorabaei ,

I already read the ASTM E1558 and ASM Metals Handbook, Vol 9 - Metallography and Microstructures. As you mentioned, every alloy has it's trial and error experiment procedures that we have faced. I appreciate your information, but our last try with perchloric of 4% with acetic acid additive showed a dull surface.

Dear Prof. Hamed Mirzadeh ,

Thank you for your guidance, it is very helpful.

Section and mount the sample

• Grind until planar using 240 grit SiC paper

• 400 grit SiC paper between 100 and 150N Force for about 15-20 seconds

• 600 grit SiC paper between 100 and 150N Force for about 15-20 seconds

• 800 grit SiC paper between 100 and 150N Force for about 15-20 seconds

• 1200 grit SiC paper between 100 and 150N Force for about 15-20 seconds (this step may be repeated 2-3 times)

• 9 micron diamond solution 5-10 minutes

• 3 micron diamond solution 5-10 minutes

• 1 micron alpha alumina solution anywhere from 5-20 minutes

• 0.3 micron alpha alumina solution 5-15 minutes

• 0.05 micron colloidal silica solution anywhere from 1 minute to several hours (~30min with max 100rpm and low force (~10-15N) is the best)

Proposed by TSL EDAX (Available online at http://www.edax.com/snippet.cfm?Snippet_Id=1452)

Dear Roumen Petrov ,

We are highly appreciated for your response and we will, admittedly, consider it in our research projects.

Yours faithfully,

Nemat.

Dear Nemat Amirjani,

For a plain carbon or low carbon steel, electro-polishing is the best method to achieve a good image quality (good hit rate during rastering/scanning). Before going to that you must prepare your sample by grinding and polishing (from 240 (coarse) to 3200 (fine) grit size emery paper, then with diamond paste, and finally with colloidal silica) in order to obtain a mirror-like surface finish. Then you should go for electropolishing using a solution made of 40% Perchloric acid and 60% Ethanol at room temperature. The electrolytic reagent should be fresh and must be kept in the refrigerator before going for the electro-polish. Choosing a suitable voltage and polishing time is the hardest part. But, it's an entirely trial and error method. Better to start with a lower voltage (say 8-10 V) and for a shorter duration (say 5 s) and keep increasing the parameters one at a time until desired surface preparation is done.

If you are not having the electro-polishing unit, then you can leave the sample up to the polishing stage (final polishing with colloidal silica) but with an even better surface finish (since it is the last stage). By this method also I could obtain a scan rate of about 90% in plain-C and stainless steel.

However, etching is not a good idea for EBSD sample preparation. If you polish well with colloidal silica and make the sample almost scratch-free, you should be able to see the grain boundaries in SEM

Dear Arka Mandal ,

Thank you for your well-established response. This response matters due to the considering all aspects and methods of preparation EBSD samples.

With best wishes,

nemat.