Pearlite

Pearlite

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 [http://www.ariuseickert.com/ScissorTechnicalArticles/EutectoidRegionOfSteel.htm] ; 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.

The appearance of pearlite under the microscope resembles mother of pearl (also a lamellar structure), from which it takes its name.

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.

References

[http://www.msm.cam.ac.uk/phase-trans/2005/pearlite.html Comprehensive information on pearlite]


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  • Pearlite — Pearl ite, Pearlstone Pearl stone , n. (Min.) A glassy volcanic rock of a grayish color and pearly luster, often having a spherulitic concretionary structure due to the curved cracks produced by contraction in cooling. See Illust. under… …   The Collaborative International Dictionary of English

  • Pearlite — Pearlite. См. Перлит. (Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО Профессионал , НПО Мир и семья ; Санкт Петербург, 2003 г.) …   Словарь металлургических терминов

  • pearlite — [pʉrl′īt΄] n. [Fr perlite < perle,PEARL1 + ite, ITE1] Metallurgy a mixture of iron and cementite, which crystallizes during the slow cooling of high temperature steel and cast iron pearlitic [pʉrlit′ik] adj …   English World dictionary

  • pearlite — perlitas statusas T sritis chemija apibrėžtis Kaitinant išpūsti, 5–20 kartų padidėję rūgščiosios vulkaninės uolienos grūdeliai atitikmenys: angl. pearlite; perlite rus. перлит …   Chemijos terminų aiškinamasis žodynas

  • pearlite — perlitas statusas T sritis ekologija ir aplinkotyra apibrėžtis Eutektoidas, susidaręs suskilus austenitui – plieno ir ketaus struktūrinis elementas. atitikmenys: angl. pearlite; perlite vok. Perlit, m rus. перлит, m …   Ekologijos terminų aiškinamasis žodynas

  • pearlite — perlitas statusas T sritis ekologija ir aplinkotyra apibrėžtis Kaitinant išpūsti (5–20 kartų padidėję) rūgščiosios vulkaninės uolienos grūdeliai. atitikmenys: angl. pearlite; perlite vok. Perlit, m rus. перлит, m …   Ekologijos terminų aiškinamasis žodynas

  • pearlite — noun Etymology: French perlite, from perle pearl Date: 1888 the lamellar mixture of ferrite and cementite in slowly cooled iron carbon alloys occurring normally as a principal constituent of both steel and cast iron • pearlitic adjective …   New Collegiate Dictionary

  • pearlite — pearlitic /perr lit ik/, adj. /perr luyt/, n. 1. Metall. a microscopic lamellar structure found in iron or steel, composed of alternating layers of ferrite and cementite. 2. Petrog. perlite. [1885 90; PEARL1 + ITE1] * * * …   Universalium

  • pearlite — noun A two phased lamellar structure composed of alternating layers of alpha ferrite and cementite that occurs in some steels and cast irons, having a pearlescent appearance …   Wiktionary

  • pearlite — Смотри Перлит …   Энциклопедический словарь по металлургии

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