Amorphous phase should appear as non indexed points or randomly indexed points depending on used EBSD system. If you would show maps here it would be easier to say.

If this amorphous layer is very thin (i.e.

This is highly related to the software you are using but generally, the quality of image (the q factor or whatsoever) is related to the crystallite size and the soundness of the crystal (i.e. inversely to the defect density). Below the crystallite size of [almost] 20nm the kikuchi pattern is almost vanished and some softwares start randomly index the image and some don't. You may generate a map of image quality and set a threshold for it. Bellow that threshold you may consider the pixel amorphous.

Farzad Hamdi Tijmen Vermeij and Grzegorz Cios

Many thanks for your helpful answers.

One of my kind colleagues answers that

"There are generally several factors for un-indexing or dark regions. Grain size being smaller than BS electron interaction volume is one of those factors. So, no! It shouldn't be assumed that the dark region is amorphous although many researchers carelessly make that conclusion and publish. To be accurate, the dark region simply means that it is un-indexed or pattern quality is low. This could be due to sample preparation or edge effect as well as fine grains"

Dear Shokouh,

your colleague is right. But you have asked us

"How the amorphous phase appears in EBSD images?" not how to recognize if there is amorphous phase using EBSD.

This is whole different story when you know there is amorphous phase and when you don't know it.

Shokouh,

It is supposed to have a well prepared, electropolished, damage free sample. Anyhow the question was about the appearance of the amorphous regions. The appeareance is as we described, but yes indeed there are many other parameters determining the image quality and you MUST take care of them if you want to use this method for measuring the volume fraction of amorphous regions: the first consideration is using smallest possible spot size, and if you work with a Zeiss or Jeol, using smallest obj aperture and long dwell time.

And should you get EBSD service and you are not the microscopists (i.e. your colleague is doing it for you): forget about getting reliable results. It is a matter of time and huge try and errors and constant learning and understanding. Sample defects and more specifically "edge effects" are definitely distinguishable after spending enough time with the microscope.

Grzegorz Cios , Farzad Hamdi

You are right, I know the question is different but I want to share the answer the people who might have encounter the same problem. I really appreciate your help!