What is a grain? (metallurgical definition)

[maleck]

I am trying to elliminate skiwed points in a EBSD grain size measurement analysis. Before eliminating those, I have to define what is a grain.

I know that a grain is "a three dimensional crystalline volume within a specimen that differs in crystallographic orientation from its surroundings". A grain is considered made of grain boundaries with disorientation superior to 15 degrees.

Correct me if I am wrong or complete as much as possible the above definition.

Thanks for any comments and for your time,
Maleck

 

[TVP]

ASTM E 7 Standard Terminology Relating to Metallography uses the following definitions:

grain—an individual crystallite in metals.

grain boundary—an interface separating two grains, where
the orientation of the lattice changes from that of one grain to that of the other. When the orientation change is very small the boundary is sometimes referred to as a subboundary.

crystallite—a crystalline grain not bounded by habit planes.

habit plane—crystallographic plane in a parent phase along
which a new phase (or phases) is (are) generated.

 

[CoryPad]

The 15-degree misorientation is used widely, though it is arbitrary. That should be listed as an assumption or initial condition for your analysis.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[maleck]

Thank you TVP, mixing the definitions you've found with the tips from CoryPad I think people will have a clear understanding of my text and analysis.

Best wishes !
Maleck