Matsci Ezam 3

Austenite

Face-centered cubic iron; also iron and steel alloys that have the FCC crystal structure.

Cementite

Iron Carbide.

Eutectoid reaction

A reaction in which, upon cooling, one solid phase transforms isothermally and reversibly into two new solid phases that are intimately mixed.

Eutectic structure

A two-phase microstructure resulting from the solidification of a liquid having the eutectic composition; the phases exist as lamellae that alternate with one another.

Eutectic reaction

A reaction in which upon cooling, one liquid phase transforms isothermally and reversibly into two new solid phases that are intimately mixed.

Ferrite

Body-centered cubic iron; also iron and steel alloys that have the BCC crystal structure.

Hypereutectoid alloy

An alloy for which the concentration of solute is greater than the eutectoid composition.

Isomorphous

Having the same structure; in phase diagram sense, having the same crystal structure or complete solid solubility for all compositions.

Lever rule

A mathematical expression by which the relative phase amounts in a two-phase alloy at equilibrium may be computed.

Liquidus line

The line or boundary separating liquid- and liquid + solid-phase regions on a binary phase diagram.

Microconstituent

An element of the microstructure that has an identifiable and characteristic structure.

Pearlite

A two-phase microstructure found in some steels and cast irons, consisting of alternating layers of ferrite and cementite.

Phase

A homogeneous portion of a system that has uniform physical and chemical characteristics.

Proeutectoid ferrite

Primary ferrite that exists in addition to pearlite for hypoeutectoid steels.

Proeutectoid cementite

Primary cementite that exists in addition to pearlite for hypereutectoid steels.

Solidus line

The locus of points at which solidification is complete upon equilibrium cooling on a phase diagram.

Block copolymer

A linear copolymer in which identical repeat units are clustered in blocks along the molecular chain.

Branched polymer

A polymer having a molecular structure of secondary chains that extend from the primary main chains.

Cross linked polymer

A polymer in which molecular chains are interconnected by covalent bonds.

Molecular weight

The sum of the atomic weights of all the atoms in a molecule.

Monomer

A stable molecule from which a polymer is synthesized.

Network polymer

A polymer produced from multifunctional monomers resulting in the formation of three-dimensional molecules.

Repeat unit

The most fundamental structural unit in a polymer chain.

Thermoplastic polymer

A semicrystalline polymeric material that softens when heated and hardens upon cooling.

Thermosetting polymer

A polymeric material that, once hardened by a chemical reaction, will not soften or melt when subsequently heated.

Elastomer

A polymeric material that may experience large and reversible elastic deformations.

Glass transition temperature

The temperature at which, upon cooling, a noncrystalline ceramic or polymer transforms from a supercooled liquid into a rigid glass.

Melting temperature

The temperature at which, upon heating, a solid (and crystalline) phase transforms into a liquid.

Vulcanization

A nonreversible chemical reaction involving sulfur that forms crosslinks between molecular chains in rubber materials.