Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of alpha-ferrite (88 wt%) and cementite (12%) that occurs in some steels and cast irons. It forms by a eutectoid reaction as austenite is slowly cooled below 727°C. The eutectoid composition of Austenite is approximately 0.8% carbon ; steel with less carbon content will contain a corresponding proportion of relatively pure ferrite crystallites that do not participate in the eutectoid reaction and cannot transform into pearlite.
A similar structure with lamelle much smaller than the wavelength of visible light lacks this pearlescent appearance. Called bainite, it is prepared by more rapid cooling. Unlike pearlite, whose formation involves the diffusion of all atoms, bainite grows by a displacive transformation mechanism.
Agency Reviews Patent Application Approval Request for "Non-Quenched and Tempered Steel Having Ultrafine Grained Pearlite Structure and Method of Manufacturing the Same"
Dec 27, 2012; By a News Reporter-Staff News Editor at Politics & Government Week -- Hyundai Motor Company has been issued patent application...