Grain size analysis measures the grain size of a metallic specimen. An accurate assessment of grain size in the specimen is used to verify the effectiveness of a particular manufacturing process...

Grain size analysis measures the grain size of a metallic specimen. An accurate assessment of grain size in the specimen is used to verify the effectiveness of a particular manufacturing process, such as heat treating or tempering.

To prepare the specimen a technician mounts a cross section, polishes it and etches it. The grain is revealed by the etching. Next they create a photomicrograph and perform one of the following procedures:

• Comparison Procedure—The photomicrograph is scaled to 100x and compared to a reference chart.
• Intercept Procedure—A concentric circle graph is superimposed on the image and the technician counts the number of interceptions on the circles with grain boundaries. 
• Planimetric Procedure—A circle is superimposed on the image. The technician counts the number of grains found within the circle, and divides the area of the circle by the number of grains to find the average grain size.

Grain size analysis is performed according to ASTM E112 Determining Average Grain Size.