the micrograph below is of a medium carbon steel, the grain size looks too coarse to be bainite - could this be acicular ferrite produced by a 2 stage cooling?
I am not sure what fine or coarse grain size has to do with bainite.
The ferrite is acicular in those photographs. There also appears to be bainite. Is there some reason you are not telling us the chemical composition? Just saying, ”a medium carbon steel", leaves a lot out. And, what is the 2 stage cooling?
Understanding the composition and thermal cycles are imperative to interpreting a microstructure.
