482 ● Glossary
specimen. An impact blow is im-
parted to the specimen by means of
a weighted pendulum.
Cis. For polymers, a prefix denot-
ing a type of molecular structure.
For some unsaturated carbon chain
atomswithinamerunit,a sideatom
or group may be situated on one
sideofthechainordirectlyopposite
at a 180⬚ rotation position. In a cis
structure, two such side groups
within the same mer reside on the
same side (e.g., cis-isoprene).
Coarse pearlite. Pearlite for which
the alternating ferrite and cement-
ite layers are relatively thick.
Coercivity (or coercive field,
H
c
). The applied magnetic field
necessarytoreducetozerothemag-
netic flux density of a magnetized
ferromagnetic or ferrimagnetic ma-
terial.
Cold working. The plastic defor-
mation of a metal at a temperature
below thatat which itrecrystallizes.
Color. Visual perception that is
stimulated by the combination of
wavelengths of light that are trans-
mitted to the eye.
Colorant. An additive that imparts
a specific color to a polymer.
Component. A chemical consti-
tuent (element or compound) of an
alloy, which may be used to specify
its composition.
Composition (C
i
). The relative
content of a particular element or
constituent (i) within an alloy, usu-
ally expressed in weight percent or
atom percent.
Concentration. See Composition.
Concentration gradient (dC/dx).
The slope of the concentration pro-
file at a specific position.
Concentration polarization. The
condition wherein the rate of an
electrochemical reaction is limited
by the rate of diffusion in the so-
lution.
Concentration profile. The curve
that results when the concentration
of a chemical species is plotted ver-
sus position in a material.
Concrete. A composite material
consisting of aggregate particles
bound together in a solid body by
a cement.
Condensation(or step reaction) po-
lymerization. The formation of
polymer macromolecules by an in-
termolecular reaction involving at
least two monomer species, usually
with theproduction ofa by-product
of low molecular weight, such as
water.
Conduction band. For electricalin-
sulators and semiconductors, the
lowest lying electron energy band
that is empty of electrons at 0 K.
Conductionelectrons arethose that
have been excited to states within
this band.
Conductivity, electrical (
). The
proportionality constant between
current density and applied electric
field;alsoameasureoftheeasewith
which a material is capable of con-
ducting an electric current.
Congruent transformation. A trans-
formation of one phase to another
of the same composition.
Continuous cooling transformation
(CCT)diagram. Aplotoftempera-
tureversusthelogarithmoftimefor
asteelalloyofdefinitecomposition.
Used to indicate when transforma-
tions occur as the initially austenit-
izedmaterial iscontinuously cooled
at a specified rate; in addition, the
finalmicrostructureandmechanical
characteristics may be predicted.
Coordination number. The num-
ber of atomic or ionic nearest
neighbors.
Copolymer. A polymer that con-
sists of two or more dissimilar mer
units in combination along its mo-
lecular chains.
Corrosion. Deteriorative loss of a
metalas aresult ofdissolutionenvi-
ronmental reactions.
Corrosionfatigue. Atypeoffailure
that results from the simultaneous
action of a cyclic stress and chemi-
cal attack.
Corrosion penetration rate (CPR).
Thickness loss of material per unit
of timeas aresult of corrosion;usu-
ally expressed in terms of mils per
year or millimeters per year.
Coulombic force. A force between
charged particles such as ions; the
forceisattractivewhentheparticles
are of opposite charge.
Covalent bond. A primary in-
teratomic bond that is formed by
the sharing of electrons between
neighboring atoms.
Creep. The time-dependent per-
manentdeformationthatoccursun-
der stress; for most materials it is
importantonlyatelevatedtempera-
tures.
Crevice corrosion. A form of cor-
rosion that occurs within narrow
crevices and under deposits of dirt
or corrosion products (i.e., in re-
gions of localized depletion of oxy-
gen in the solution).
Critical resolved shear stress
(
crss
). That shear stress, resolved
within a slip plane and direction,
which is required to initiate slip.
Crosslinkedpolymer. Apolymerin
which adjacent linear molecular
chains are joined at various posi-
tions by covalent bonds.
Crystalline. Thestateofasolidma-
terial characterized by a periodic
and repeating three-dimensional
array of atoms, ions, or molecules.
Crystallinity. For polymers, the
state wherein a periodic and re-
peating atomic arrangement is
achieved by molecular chain
alignment.
Crystallite. A region within a crys-
talline polymer in which all the mo-
lecular chains are ordered and
aligned.
Crystal structure. For crystalline
materials, the manner in which
atoms or ions are arrayed in space.
It is defined in termsof the unit cell
geometry and the atom positions
within the unit cell.
Crystal system. A schemeby which
crystal structures are classified ac-
cording to unit cell geometry. This
geometryis specifiedin terms ofthe
relationships between edge lengths
and interaxial angles. There are
seven different crystal systems.
Curie temperature (T
c
). That tem-
perature above which a ferromag-