I'm hoping someone could help me with this problem, or direct me to someone else. I would really appreciate this. Thank you very much for your time. The anodizing method that you have been advised about does not etch the grain boundaries, but does provide a method of showing a contrast between adjacent grains under polarized light illumination. The anodized surface is examined using cross polarizers.
Grains structure is very colorful variations of blues and reds.
I have used this method successfully with 357 Al castings. Another method for grain boundary delineation has been proposed recently by researchers from Kaiser Aluminum. This method utilizes special heat treatments and etching to reveal grain boundaries. The purpose of the inspection was to pinpoint any rapid or abnormal change between boundaries which would indicate fatigue or stress risers in the blade. The alloy of the material of which these blades were manufactured was propriortary.