a metallic solid or liquid formed from an intimate combination of two or more elements.
Alternating Copolymer
a polymer, composed of two different repeating mers, in which the different mer units systematically alternate positions along the molecular chain.
Amorphography
the branch of science concerned with the determination of amorphous solid structures and their systemmatic classification (see also crystallography).
Amorphous
having no long-range order.
Anisotropic
exhibiting different values of a property in different crystallographic directions.
Annealing
a generic term used to denote a heat treatment wherein the microstructrure and, consequently, the properties of a material are altered. Frequently, refers to heat treatment whereby a cold-worked metal is softened by allowing it to recrystallize.
Antiferromagnetism
a phenomenon observed in some materials in which complete magnetic moment cancellation occurs as a result of antiparallel coupling of adjacent atoms or ions. The macroscopic solid possesses no net magnetic moment.
Atactic
a type of polymer chain configuration wherein side groups are randomly poitioned on one side of the polymer backbone or the other.
Austenite
face-centered cubic iron; also iron and steel alloys that have the FCC structure.
B
Bainite
a Fe-C composition consisting of a fine dispersion of cementite in alpha-ferrite. It is an austenitic transformation product that forms at temperatures between those at which pearlite and martensite transformations occur.
Band Gap Energy
for semiconductors and insulators, the energies that lie between the valence and conduction bands.
Bifunctional Monomer
a monomer unit that has two active bonding positions.
Block Copolymer
a linear copolymer in which identical mer units are clustered in blocks along the molecular chain.
The gas constant per molecule: 1.381x10-23J/atom K; 1.381x10-16 erg/atom K; or 8.63x10-5 eV/atom K.
Bonding Energy
the energy required to separate two atoms that are chemically bonded to each other.
Bragg's Law
a relationship that stipulates the condition for diffraction by a set of crystallographic planes.
Branched Polymer
a polymer having a molecular structure of secondary chains that extend from the primary chains.
Brass
a copper-rich copper-zinc alloy.
Bravais Lattice
Brazing
a metal joining technique that uses a molten filler metal alloy having a melting temperature greater than about 425 ° C.
Brittle Fracture
fracture that occur by rapid crack propagation and without appreciable macroscopic deformation.
Bronze
a copper-rich copper-tin alloy.
Burgers Vector
a vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.
C
Calcination
a high-temperature reaction whereby one solid material dissociates to form a gas and another solid.
Capacitance
the charge-storage ability of a capacitor, defined as the magnitude of charge stored on either plate divided by the applied voltage.
Carburizing
the process by which the surface carbon concentration of a ferrous alloy is increased by diffusion from the surrounding environment.
Cast Iron
a ferrous alloy with carbon content between 2 and 4.5 wt%.
Cathodic Protection
a means of corrosion prevention whereby electrons are supplied to the structure to be protected from an external source such as anoother more reactive metal or a dc power supply.
a material brought about by combining materials differing in composition or form on a macroscale for the purpose of obtaining specific characteristics and properties. The constituents retain their identity such that they can be physically identified and they exhibit an interface between one another.
Concrete
a composite material consisting of aggregate particles bound together in a solid body by a cement.
Condensation Polymerization
the formation of polymers by an intermolecular reaction involving at least two monomer species, usually with the production of a low molecular weight by-product such as water.
Conduction Band
the lowest-lying electron energy band that is not completely filled with electrons.
Configuration
Conformation
Congruent Transformation
a transformation of one phase to another that does not involve any change in composition.
Coordination Number
the number of atomic or ionic nearest neighbors.
Copolymer
a polymer that consists of two or more dissimilar mer units in combination along its molecular chains.
Corrosion
Deteriorative loss of a metal as a result of dissolution environmental reactions.
Covalent Bond
a primary interatomic bond that is formed by the sharing electrons between neighboring atoms.
Creep
the time-dependent permanent deformation that occurs under stress; for most materials it is important only at elevated temperatures.
Critical Point
Crosslinked Polymer
A polymer in which adjacent linear molecular chains are joined at various positions by covalent bonds.
Crystalline
the state of a solid material characterized by a periodic and repeating three-dimensional arrays of atoms, ions, or molecules.
Crystallinity
for polymers, the state wherein a periodic and repeating atomic arrangement is achieved by molecular chain alignment.
Crystallite
a region within a crystalline polymer in which all the molecular chains are ordered and aligned.
a linear crystalline defect around which there is an atomic misalignment.
Doping
the intentional alloying of semiconducting materials with controlled concentrations of donor or acceptor impurities.
Drawing
a deformation technique used to fabricate metal wire and tubing. Deformation is accomplished by pulling the material through a die by means of a tensile force applied on the exit side.
Ductility
a measure of a material's ability to undergo appreciable plastic deformation before fracture.
a crystal structure found in some of the common elemental metals. Within the cubic unit cell, atoms are located at all corner and face-centered positions.
Fatigue
failure, at relatively low stress levels, of structures that are subjected to fluctuating and cyclic stresses.
Fermi Energy
for a metal, the energy corresponding to the highest filled electron state in the valence bond at 0 K.
body-centered cubic iron. Also, iron and steel alloys that have the BCC crystal structure.
Ferroelectric
a dielectric material that may exhibit polarization in the absence of an electric field.
Ferromagnetism
permanent and large magnetizations found in some metals (e.g., Fe, Ni, and Co), which result from the parallel alignments of neighboring magnetic moments.
Fiber
any material that has been drawn into a cylinder with a length-to-diameter ratio greater than about ten.
Filler
an inert foreign substance added to a matrix to improve or modify its properties.
Firing
a high-temperature heat treatment that increases the density and strength of a ceramic piece.
Forging
mechanical forming of a metal or alloy by heating and hammering.
Fracture toughness
critical value of the stress intensity factor for which crack extensions occurs.
Fracture
Free energy
a thermodynamic quantity that is a function of both the internal energy and entropy of a system.
Frenkel Defect
in an ionic solid, a cation-vacancy and cation-interstitial pair.
a fine-grained crystalline material that was formed as a glass and subsequently devitrified (crystallized).
H
Hall Effect
the phenomenon whereby a force is brought to bear on a moving electron or hole by a magnetic field that is applied perpendicular to the direction of motion. The force direction is perpendicular to both the magnetic field and the particle motion directions.
Hardenability
a measure of the depth to which a specific ferrous alloy may be hardened by the formation of martensite upon quenching from a temperature above the upper critical temperature.
Hardness
the measure of some materials' resistance to deformation by surface indentation or by abrasion.
Hexagonal Close-Packed (HCP)
a crystal structure found for some metals. The HCP unit cell is of hexagonal geometry and is generated by the stacking of close-packed planes of atoms.
Hole (electron)
for semi-conductors and insulators, a vacant electron state in the valence band that behaves as a positive charge carrier in an electric field.
Homopolymer
a polymer having a chain structure in which all mer units are of the same type.
Hot Working
any metal forming operation that is performed above a metal recrystallization temperature.
Hydrogen Bond
a strong secondary interatomic bond which exists between a bound hydrogen atom (its unscreened proton) and the electrons of adjacent atoms.
for an alloy system displaying a eutectoid, an alloy for which the concentration of solute is greater than the eutectoid composition.
Hypoeutectoid Alloy
for an alloy system displaying a eutectoid, an alloy for which the concentration of solute is less than the eutectoid composition
Hysteresis (magnetic)
the irreversible magnetic flux density-versus-magnetic field strength (B-versus-H) behavior found for ferromagnetic and ferrimagnetic materials.
I
Impact Energy
a measure of the energy absorbed during the fracture of a specimen of standard dimensions and geometry when subjected to very rapid (impact) loading. Charpy and Izod impact tests are used to measure this parameter, which is important in assessing the ductile-to-brittle transition behavior of a material.
the proportionality constant between the magnetization M and the magnetic field strength H.
Magnetization
the total magnetic moment per unit volume of material. Also, a measure of the contribution to the magnetic flux by some material within an H field.
Martensite
a metastable Fe-C composition consisting of supersaturated carbon in iron that is the product of a diffusionless (athermal) transformation from austenite.
the initial stage in a phase transformation. It is evidenced by the formation of small particles (nuclei) of the new phase, which are capable of growing.
O
Octahedral position
the void space among closed-packed, hard sphere atoms or ions for which there are six nearest neighbors. An octahedron (double pyramid) is curcumscribed by lines constructed from centers of adjacent spheres.
P
Paramagnetism
a relatively weak form of magnetism that results from the independent alignment of atomic dipoles (magnetic) with an applied magnetic field.
deformation that is permanent or nonrecoverable after release of the applied load.
Plasticizer
a low molecular weight polymer additive that enhances flexibility and workability and reduces stiffness and brittleness.
Point Defect
a crystalline defect associated with one or, at most, several atomic sites.
Poisson's Ratio
for elastic deformation, the negative ratio of lateral and axial strains that result from an applied axial stress.
Polar Molecule
a molecule in which there exists a permanent electric dipole moment by virtue of the asymmetrical distribution of positively and negatively charged regions.
Polarization (electronic)
for an atom, the displacement of the center of the negatively charged electron cloud relative to the positive nucleus, which is induced by an electric field.
Polarization (ionic)
polarization as a result of the displacement of anions and cations in opposite directions.
Polarization (orientation)
polarization resulting from the alignment (by rotation) of permanent electric dipole moments with an applied electric field.
Polycrystalline
referring to crystalline materials that are composed of more than one crystal or grain.
Polymer
a solid, nonmetallic (normally organic) compound of high molecular weight the structure of which is composed of small repeat (or mer) units.
Polymorphism
the ability of a solid material to exist in more than one form or crystal structure.
Portland Cement
Precipitation Hardening
hardening and strengthening of a metal alloy by extremely small and uniformly dispersed particles that precipitate from a supersaturated solid solution.
Prepreg
continuous fiber reinforcement pre-impregnated with a polymer resin which is then partially cured.
Primary Bond
interatomic bonds that are relatively strong and for which bonding energies are relatively large.
Proportional Limit
the point on a stress-strain curve at which the straight line proportionality between stress and strain ceases.
p-type Semiconductor
a semiconductor for which the predominant charge carriers responsible for electrical conduction are holes. Normally, acceptor impurity atoms give rise to the excess holes.
Q
R
Random Copolymer
a polymer in which two different mer units are randomly distributed along the molecular chain.
Reciprocal Lattice
Recrystallization
the formation of a new set of strain-free grains within a previously cold-worked material; normally an annealing heat treatment is necessary.
Reflection
deflection of a light beam at the interface between two media.
Refraction
bending of a light beam upon passing from one medium into another.
Refractive Index
the ratio of the velocity of light in a vacuum to the velocity of light in some medium.
Refractory
a metal or ceramic that may be exposed to extremely high temperatures without deteriorating rapidly or without melting.
Reinforcement
Relative Magnetic Permeability
the ratio of the magnetic permeability of some medium to that of a vacuum.
Resistivity
the reciprocal of electrical conductivity, and a measure of a material's resistance to the passage of electric current.
Rupture
failure that is accompanied by significant plastic deformation.