mse final ALL terms

bainite

An austenitic transformation product found in some steels and cast irons. It forms at temperatures between those at which pearlite and martensite transformations occur. The microstructure consists of α-ferrite and a fine dispersion of cementite.

coarse pearlite

Pearlite for which the alternating ferrite and cementite layers are relatively thic

fine pearlite

Pearlite in which the alternating ferrite and cementite layers are relatively thin.

kinetics

The study of reaction rates and the factors that affect them

martensite

A metastable iron phase supersaturated in carbon that is the product of a diffusionless (athermal) transformation from austenite.

spheroidite

Microstructure found in steel alloys consisting of spherelike cementite particles within an -ferrite matrix. It is produced by an appropriate elevated-temperature heat treatment of pearlite, bainite, or martensite, and is relatively soft.

ceramic-matrix composite (CMC)

A composite for which both matrix and dispersed phases are ceramic materials. The dispersed phase is normally added to improve fracture toughness.

concrete

A composite material consisting of aggregate particles bound together in a solid body by a cement.

dispersed phase

For composites and some two-phase alloys, the discontinuous phase surrounded by the matrix phase.

fiber

Any polymer, metal, or ceramic that has been drawn into a long and thin filament.

fiber-reinforced composite

A composite in which the dispersed phase is in the form of a fiber (i.e., a filament that has a large length-to-diameter ratio).

large-particle composite

A type of particle-reinforced composite in which particle-matrix interactions cannot be treated on an atomic level; the particles reinforce the matrix phase.

longitudinal direction

The lengthwise dimension. For a rod or fiber, in the direction of the long axis.

matrix phase

The phase in a composite or two-phase alloy microstructure that is continuous or completely surrounds the other (or dispersed) phase.

metal-matrix composite (MMC)

A composite material that has a metal or metal alloy as the matrix phase. The dispersed phase may be particulates, fibers, or whiskers, which normally are stiffer, stronger, and/or harder than the matrix.

rule of mixtures

The properties of a multiphase alloy or composite material are a weighted average (usually on the basis of volume) of the properties of the individual constituents.

specific modulus (specific stiffness)

The ratio of elastic modulus to specific gravity for a material.

specific strength

The ratio of tensile strength to specific gravity for a material.

transverse direction

A direction that crosses (usually perpendicularly) the longitudinal or lengthwise direction

anode

The electrode in an electrochemical cell or galvanic couple that experiences oxidation, or gives up electrons.

cathode

The electrode in an electrochemical cell or galvanic couple at which a reduction reaction occurs; thus the electrode that receives electrons from an external circuit.

corrosion

Deteriorative loss of a metal as a result of dissolution environmental reactions.

electrolyte

A solution through which an electric current may be carried by the motion of ions.

electromotive force (emf) series

A ranking of metallic elements according to their standard electrochemical cell potentials.

galvanic series

A ranking of metals and alloys as to their relative electrochemical reactivity in seawater.

oxidation

The removal of one or more electrons from an atom, ion, or molecule.

reduction

The addition of one or more electrons to an atom, ion, or molecule.

standard half-cell

An electrochemical cell consisting of a pure metal immersed in a 1M aqueous solution of its ions, which is electrically coupled to the standard hydrogen electrode.

conduction band

For electrical insulators and semiconductors, the lowest-lying electron energy band that is empty of electrons at 0 K. Conduction electrons are those that have been excited to states within this band.

doping

The intentional alloying of semiconducting materials with controlled concentrations of donor or acceptor impurities.

electrical conductivity

The proportionality constant between current density and applied electric field; also, a measure of the ease with which a material is capable of conducting an electric current.

energy band gap

For semiconductors and insulators, the energies that lie between the valence and conduction bands; for intrinsic materials, electrons are forbidden to have energies within this range.

extrinsic semiconductor

A semiconducting material for which the electrical behavior is determined by impurities

free electron

An electron that has been excited into an energy state above the Fermi energy (or into the conduction band for semiconductors and insulators) and may participate in the electrical conduction process.

hole (electron)

For semiconductors and insulators, a vacant electron state in the valence band that behaves as a positive charge carrier in an electric field.

intrinsic semiconductor

A semiconductor material for which the electrical behavior is characteristic of the pure material—that is, in which electrical conductivity depends only on temperature and the band gap energy.

mobility (electron, u_e, and hole, u_h )

The proportionality constant between the carrier drift velocity and applied electric field; also, a measure of the ease of charge carrier motion.

valence band

For solid materials, the electron energy band that contains the valence electrons.

heat capacity

The quantity of heat required to produce a unit temperature rise per mole of material.

linear coefficient of thermal expansion

The fractional change in length divided by the change in temperature.

specific heat

The heat capacity per unit mass of material.

thermal conductivity

For steady-state heat flow, the proportionality constant between the heat flux and the temperature gradient. Also, a parameter characterizing the ability of a material to conduct heat.

thermal shock

The fracture of a brittle material as a result of stresses introduced by a rapid temperature change.

austenite

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

cementite

Iron carbide (Fe3C)

eutectic reaction

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

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.

eutectoid reaction

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

ferrite (iron)

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

hypereutectoid alloy

For an alloy system displaying a eutectoid, an alloy for which the concentration of solute is greater than the eutectoid composition.

isomorphous

Having the same structure. In the phase diagram sense, isomorphicity means having the same crystal structure or complete solid solubility for all compositions

lever rule

A mathematical expression, such as Equation 9.1b or Equation 9.2b, by which the relative phase amounts in a two-phase alloy at equilibrium may be computed.

liquidus line

On a binary phase diagram, the line or boundary separating liquid- and liquid + solid-phase regions. For an alloy, the liquidus temperature is the temperature at which a solid phase first forms under conditions of equilibrium cooling.

microconstituent

An element of the microstructure that has an identifiable and characteristic structure. It may consist of more than one phase, such as with pearlite.

pearlite

A two-phase microstructure found in some steels and cast irons; it results from the transformation of austenite of eutectoid composition and consists of alternating layers (or lamellae) 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

On a phase diagram, the locus of points at which solidification is complete upon equilibrium cooling, or at which melting begins upon equilibrium heating.

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 adjacent linear molecular chains are joined at various positions 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 having three or more active covalent bonds, resulting in the formation of three-dimensional molecules.

repeat unit

The most fundamental structural unit in a polymer chain. A polymer molecule is composed of a large number of repeat units linked together.

thermoplastic polymer

A semicrystalline polymeric material that softens when heated and hardens upon cooling. While in the softened state, articles may be formed by molding or extrusion.

thermosetting polymer

A polymeric material that, once having been cured (or 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 the viscosity of a glass material is 10 Pas (100 P).

vulcanization

A nonreversible chemical reaction involving sulfur or another suitable agent in which crosslinks are formed between molecular chains in rubber materials. The rubber's modulus of elasticity and strength are enhanced.

Ductility

A measure of a material's ability to undergo appreciable plastic deformation before fracture; it may be expressed as percent elongation (%EL) or percent reduction in area (%RA) from a tensile test

Elastic Deformation

Deformation that is nonpermanent—that is, totally recovered upon release of an applied stress

engineering strain

See strain, engineering

engineering stress

See stress, engineering

hardness

The measure of a material's resistance to deformation by surface indentation or by abrasion.

modulus of elasticity

The ratio of stress to strain when deformation is totally elastic; also a measure of the stiffness of a material

plastic deformation

Deformation that is permanent or nonrecoverable after release of the applied load. It is accompanied by permanent atomic displacements.

Poisson's ratio

For elastic deformation, the negative ratio of lateral and axial strains that result from an applied axial stress.

tensile strength

The maximum engineering stress, in tension, that may be sustained without fracture. Often termed ultimate (tensile) strength.

toughness

A mechanical characteristic that may be expressed in three contexts: (1) the measure of a material's resistance to fracture when a crack (or other stress-concentrating defect) is present; (2) the ability of a material to absorb energy and plastically deform before fracturing; and (3) the total area under the material's tensile engineering stress-strain curve taken to fracture.

true strain

The natural logarithm of the ratio of instantaneous gauge length to original gauge length of a specimen being deformed by a uniaxial force.

true stress

The instantaneous applied load divided by the instantaneous cross-sectional area of a specimen.

Yield strength

The stress required to produce a very slight yet specified amount of plastic strain; a strain offset of 0.002 is commonly used.

cold working

The plastic deformation of a metal at a temperature below that at which it recrystallizes.

critical resolved shear stress

The shear stress, resolved within a slip plane and direction, required to initiate slip.

dislocation density

The total dislocation length per unit volume of material; alternatively, the number of dislocations that intersect a unit area of a random surface section.

grain growth

The increase in average grain size of a polycrystalline material; for most materials, an elevated-temperature heat treatment is necessary.

recovery

The relief of some of the internal strain energy of a previously cold-worked metal, usually by heat treatment.

recrystallization

The formation of a new set of strain-free grains within a previously cold-worked material; normally, an annealing heat treatment is necessary.

recrystallization temperature

For a particular alloy, the minimum temperature at which complete recrystallization occurs within approximately 1 h.

resolved shear stress

An applied tensile or compressive stress resolved into a shear component along a specific plane and direction within that plane.

slip

Plastic deformation as the result of dislocation motion; also, the shear displacement of two adjacent planes of atoms.

slip system

The combination of a crystallographic plane and, within that plane, a crystallographic direction along which slip (i.e., dislocation motion) occurs

solid-solution strengthening

Hardening and strengthening of metals that result from alloying in which a solid solution is formed. The presence of impurity atoms restricts dislocation mobility.

strain hardening

The increase in hardness and strength of a ductile metal as it is plastically deformed below its recrystallization temperature.

brittle fracture

Fracture that occurs by rapid crack propagation and without appreciable macroscopic deformation.