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Iron-carbon phase diagram. α-Iron is a fairly soft metal that can dissolve only a small concentration of carbon (no more than 0.021% by mass at 910 °C). [133] Austenite (γ-iron) is similarly soft and metallic but can dissolve considerably more carbon (as much as 2.04% by mass at 1146 °C).
Low-pressure phase diagram of pure iron. BCC is body centered cubic and FCC is face-centered cubic. Iron-carbon eutectic phase diagram, showing various forms of Fe x C y substances. Iron allotropes, showing the differences in structure. The alpha iron (α-Fe) is a body-centered cubic (BCC) and the gamma iron (γ-Fe) is a face-centered cubic (FCC).
Cementite (or iron carbide) is a compound of iron and carbon, more precisely an intermediate transition metal carbide with the formula Fe 3 C. By weight, it is 6.67% carbon and 93.3% iron. It has an orthorhombic crystal structure. [4]
Isotopes of carbon are atomic nuclei that contain six protons plus a number of neutrons (varying from 2 to 16). Carbon has two stable, naturally occurring isotopes. [69] The isotope carbon-12 (12 C) forms 98.93% of the carbon on Earth, while carbon-13 (13 C) forms the remaining 1.07%. [69]
Steel is between 0 and 2.06 mass percent of carbon. Cast iron is between 2.06 and 6.67%. Black lines indicate the metastable Fe/Fe3Cphase, red is the stable Fe/Carbon phase This diagram is for illustrative purposes only, and is not thermodynamically accurate.
Iron-carbon phase diagram, showing the conditions under which austenite (γ) is stable in carbon steel. Allotropes of iron; alpha iron and gamma iron. Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. [1]
Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5 wt%) and cementite (12.5 wt%) that occurs in some steels and cast irons. During slow cooling of an iron-carbon alloy, pearlite forms by a eutectoid reaction as austenite cools below 723 °C (1,333 °F) (the eutectoid temperature). Pearlite ...
Martensite is formed in carbon steels by the rapid cooling of the austenite form of iron at such a high rate that carbon atoms do not have time to diffuse out of the crystal structure in large enough quantities to form cementite (Fe 3 C). Austenite is gamma-phase iron (γ-Fe), a solid solution of iron and alloying elements.