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The iron-carbon phase diagram. While cementite is thermodynamically unstable, eventually being converted to austenite (low carbon level) and graphite (high carbon level) at higher temperatures, it does not decompose on heating at temperatures below the eutectoid temperature (723 °C) on the metastable iron-carbon phase diagram.
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.
English: Iron-carbon binary phase diagram: metastable (cementite) in plain line; stable (graphite) in dashed line. Caption: Fe 3 C: cementite (iron carbide); L: liquid; α: ferrite (alpha iron), body-centered cubic; δ: delta-iron, body-centered cubic; γ: austenite (gamma iron), face-centered cubic; solvus A 1: lower limit of existence of ...
Iron-carbon phase diagram, showing the iron-carbon phase diagram (near the lower left). In iron and steel metallurgy, ledeburite is a mixture of 4.3% carbon in iron and is a eutectic mixture of austenite and cementite. Ledeburite is not a type of steel as the carbon level is too high although it may occur as a separate constituent in some high ...
The A 2 line forms the boundary between the beta iron and alpha fields in the phase diagram in Figure 1. Similarly, the A 2 boundary is of only minor importance compared to the A 1 , A 3 and A cm critical temperatures. The A cm, where austenite is in equilibrium with cementite + γ-Fe, is beyond the right edge in Fig. 1.
A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions (pressure, temperature, etc.) at which thermodynamically distinct phases (such as solid, liquid or gaseous states) occur and coexist at equilibrium.
Pearlite occurs at the eutectoid of the iron-carbon phase diagram (near the lower left). 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.
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] In plain-carbon steel , austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures.