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Ferrite (iron)
 
 
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Ferrite or alpha iron (a-Fe) is a materials science
Materials science

Materials science or materials engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering....
 term for iron
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
, or a solid solution
Solid solution

A solid solution is a solid-phase solution of one or more soluble in a solvent. Such a mixture is considered a solution rather than a Chemical compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single wiktionary:Homogeneous phase ....
 with iron as the main constituent, with a body centred cubic crystal structure
Crystal structure

In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a motif, a set of atoms arranged in a particular way, and a lattice....
. It is the component which gives steel
Steel

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight , depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten....
 and cast iron
Cast iron

Cast iron usually refers to Gray iron, but also identifies a large group of ferrous alloys, which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy....
 their magnetic properties, and is the classic example of a ferromagnetic
Ferromagnetism

Ferromagnetism is the basic mechanism by which certain materials form permanent magnets and/or exhibit strong interactions with magnets; it is responsible for most phenomena of magnetism Magnet#Common uses of magnets ....
 material.

Practically speaking, it can be considered pure iron
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
. It has a strength of 280 N/mm2 and a hardness of approximately 80 Brinell
Brinell scale

The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece....
.






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Ferrite or alpha iron (a-Fe) is a materials science
Materials science

Materials science or materials engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering....
 term for iron
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
, or a solid solution
Solid solution

A solid solution is a solid-phase solution of one or more soluble in a solvent. Such a mixture is considered a solution rather than a Chemical compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single wiktionary:Homogeneous phase ....
 with iron as the main constituent, with a body centred cubic crystal structure
Crystal structure

In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a motif, a set of atoms arranged in a particular way, and a lattice....
. It is the component which gives steel
Steel

Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.14% by weight , depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese, chromium, vanadium, and tungsten....
 and cast iron
Cast iron

Cast iron usually refers to Gray iron, but also identifies a large group of ferrous alloys, which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy....
 their magnetic properties, and is the classic example of a ferromagnetic
Ferromagnetism

Ferromagnetism is the basic mechanism by which certain materials form permanent magnets and/or exhibit strong interactions with magnets; it is responsible for most phenomena of magnetism Magnet#Common uses of magnets ....
 material.

Practically speaking, it can be considered pure iron
Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
. It has a strength of 280 N/mm2 and a hardness of approximately 80 Brinell
Brinell scale

The Brinell scale characterizes the indentation hardness of materials through the scale of penetration of an indenter, loaded on a material test-piece....
. Ferrite can be strictly defined as a solid solution of iron in body-centered cubic (BCC) containing a maximum of 0.03% carbon at and 0.006% carbon at room temperature.

Mild steel (carbon steel with up to about 0.2 wt% C) consist mostly of ferrite, with increasing amounts of pearlite
Pearlite

Pearlite is a Phase , Lamellar structure structure composed of alternating layers ofFerrite and cementite that occurs in some steels and cast irons....
 (a fine lamellar structure of ferrite and cementite
Cementite

Cementite or iron carbide is a chemical compound with the formula Fe3C , and an orthorhombic crystal structure. It is a hard, brittle material, normally classified as a ceramic in its pure form, though it is more important in metallurgy....
) as the carbon content is increased. Since bainite
Bainite

Bainite is a phase that exists in steel microstructures after certain heat treatments. First described by Davenport ES and Edgar Bain, it is one of the phase transformation that may form when austenite is cooled past a critical temperature of 723 ?C ....
 (shown as ledeburite on the diagram) and pearlite each have ferrite as a component, any iron-carbon alloy will contain some amount of ferrite if it is allowed to reach equilibrium
Chemical equilibrium

In a chemical process, chemical equilibrium is the state in which the Activity or concentrations of the reactants and products have no net change over time....
 at room temperature.

Phase Diag Iron Carbon
In pure iron, ferrite is stable below . Above this temperature the face-centered cubic form of iron, austenite
Austenite

Austenite is a metallic non-magnetic solid solution of iron and an alloying element. In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K ; other alloys of steel have different eutectoid temperatures....
 (gamma-iron) is stable. Above , up to the melting point
Melting point

The melting point of a solid is the temperature range at which it changes states of matter from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium....
 at , the body-centred cubic crystal structure is again the more stable form of delta-ferrite (d-Fe).

Only a very small amount of carbon
Carbon

Carbon is a chemical element with chemical symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalence?making four electrons available to form covalent bond chemical bonds....
 can be dissolved in ferrite; the maximum solubility
Solubility

Solubility is often seen as a property of a substance; for instance the solubility of a solid substance usually refers to the concentration of the substance in a liquid that has reached equilibrium with the substance in solid phase ....
 is about 0.02 wt% at . This is because carbon dissolves in iron interstitially, with the carbon atoms being about twice the diameter of the interstitial "holes", so that each carbon atom is surrounded by a strong local strain field. Hence the enthalpy
Enthalpy

In thermodynamics and chemistry, the enthalpy is a quotient or description of thermodynamic potential of a system, which can be used to calculate the heat transfer during a quasistatic process taking place in a closed system thermodynamic system under constant pressure....
 of mixing is positive (unfavourable), but the contribution of entropy
Entropy

In many branches of science, entropy is a measure of the disorder of a system. The concept of entropy is particularly notable as it is applied across physics, information theory and mathematics....
 to the free energy
Thermodynamic free energy

In thermodynamics, the term thermodynamic free energy refers to the amount of Work that can be extracted from a system, and is helpful in engineering applications....
 of solution
Solution

In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent....
 stabilises the structure for low carbon content. also is the minimum temperature at which iron-carbon austenite (0.8 wt% C) is stable; at this temperature there is a eutectoid reaction between ferrite, austenite and cementite
Cementite

Cementite or iron carbide is a chemical compound with the formula Fe3C , and an orthorhombic crystal structure. It is a hard, brittle material, normally classified as a ceramic in its pure form, though it is more important in metallurgy....
.

See also

  • Acicular ferrite
    Acicular ferrite

    Acicular ferrite consists of a fine structure of interlocking ferrite plates .Acicular ferrite is formed in the interior of the original Austenite grains by direct nucleation from the inclusions, resulting in randomly oriented short ferrite needles with a 'basket weave' appearance....
  • Spring steel
    Spring steel

    Spring steel is a low alloy, medium carbon steel with a very high yield strength. This allows objects made of spring steel to return to their original shape despite significant bending or twisting....
  • Maraging steel
    Maraging steel

    Maraging steels are iron alloys which are known for possessing superior strength and toughness without losing malleability. These steels are a special class of low carbon ultra-high strength steels which derive their strength not from carbon, but from precipitation of inter-metallic compounds....
  • Cementite
    Cementite

    Cementite or iron carbide is a chemical compound with the formula Fe3C , and an orthorhombic crystal structure. It is a hard, brittle material, normally classified as a ceramic in its pure form, though it is more important in metallurgy....
  • Eutectoid
  • Martensite
    Martensite

    Martensite, named after the German :category:metallurgists Adolf Martens , most commonly refers to a very hard form of steel crystalline structure, but it is also any crystal structure that is formed by displacive transformation....
  • Ferrite bead
    Ferrite bead

    File:Two ferrite beads.jpgA ferrite bead is a passive electric component used to suppress high frequency Electronic noise in electronic circuits....