Very Low Carbon Steel
Chris McCowan (NIST)

Cross-sectioned, polished, acid-etched
Micrograph showing ferrite crystals in a very low carbon steel, referred to as Interstitial Free (IF) steel. IF steel is an affordable high quality material used for applications ranging from automotive body to electronic components. This steel theoretically does not have any interstitial atoms in the crystal lattice (such as carbon, hydrogen, oxygen, or nitrogen), which results in a steel with extraordinary formability and ductility. The parallel lines within the crystals are referred to as “banding”. The length of the scale bar at the center left is 10 microns. Contrast the carbon rosettes visible in higher-carbon materials like cast iron (see the micrograph of cast iron from the US Capitol Dome).