Cementite


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Related to Cementite: austenite, martensite

cementite

[si′men‚tīt]
(metallurgy)
Fe3C A hard, brittle, crystalline compound occurring as lamellae or plates in steel. Also known as iron carbide.

Cementite

 

an iron carbide, Fe3C; a phase and structural component of iron-carbon alloys (seeIRON-CARBON ALLOYS). Cementite has an orthorhombic crystal lattice. It is very hard and brittle and is slightly magnetic at temperatures up to 210°C. It is a metastable phase; the formation of the stable phase—graphite—is in many cases difficult. Cementite is precipitated from a melt consisting of austenite and ferrite. Depending on the crystallization conditions and subsequent treatment, it can have various forms, such as equiaxial grains, lattices along grain boundaries, and plates; it can also exhibit a Widmannstatten structure. Cementite is a constituent of the structural components of steel and cast iron—ledeburite, pearlite, bainite, and tempered sorbite.

REFERENCE

Bunin, K. P., and A. A. Baranov. Metallografiia. Moscow, 1970.
References in periodicals archive ?
However, it should be taken into account that the steel studied has already been severely deformed before ECAP, the cementite particles have been fragmented, and this would cause the unusual behavior.
Baumann (1998) also holds that an extremely high level of deformation and shearing stress leads to dissolution of cementite and diffusion of carbon.
Image analysis of pearlite spheroidization based on the morphological charact-erization of cementite particles.
9b in the centre of the photograph, surrounded by residual cementite inclusions).
The Cementite or Martensite and the Acicular Ferrite (AF) in the part between the center and the fusion line have higher hardness than Polygonal Ferrite (PF) in the weld seam center.
White Cast Iron: White cast iron occurs when all of the carbon in the casting is combined with iron to form cementite.
If we make an equivalence between steel and polypropylene, Austenite is equivalent to molten polypropylene, Ferrite and Cementite to [alpha]-monoclinic polypropylene, Martensite to the smectic form.
At different heats, the molecules in steel change their nature--actually becoming different minerals with such names as austenite and cementite.
Moreover, according to the classical nucleation theory, there are the fluctuations of composition, microstructure and energy in the interfaces between cementite and ferrite, which is beneficial to form an austenite nucleus.
However, since martensite is a non-equilibrium stage of the iron-iron carbide phase diagram, it has not been exposed that warming the part after the cryogenic treatment results in the re-transformation of the induced martensite back to austenite or to ferrite plus cementite, negating the hardening result.
The initial microstructure consisted of pearlite with a small amount of cementite precipitated along prior austenite boundaries (Fig.