A Method for the Determination of Ferrite Grains with a Surface Normal close to the (111) Orientation in Cold Rolled Steel Samples with Color Etching and Optical Microscopy

Abstract

Cold rolled steel specimens were investigated by color etching. We proved that in this sample ferrite grains with a surface normal close to the (111) orientation are etched with the slowest speed with Beraha-I type color etchant, and that after a sufficient over-etching these specific grains could be distinguished based on this feature. It was demonstrated, that it is possible to stop the color etching in a phase when only grains with (111) orientation show color due to the layer interference, while all the other grains are dull gray due to a thick and transparent layer. This observation was utilized to develop a method to identify and quantify ferrite grains with (111) orientation in cold rolled steel samples with the application of color etching, optical microscopy and digital image post-processing.