koma ord

Amorphous non-crystalline

Anisotropy directionality of properties

close-packed direction close-packed planes, as FCC and BCC

crystal structure the manner in which atoms, ions, or molecules are arranged

interplanar distance distance between two structure planes.

interstitial atom between two other atoms were it should not be

Isotropy properties independent of direction

Lattice parameter axial length of unit cell

lattice point corners of a unit cell

Degree of packing APF

Planar density Number of atoms centred on plane

Polymorphism more than one crystal structure

repeat distance distance between two repeating units in a crystalline structure

unit cell Crystal structures are specified geometry and atom positions within

Hydrocarbon chains consist of hydrogen and carbon bonding via van der waals bonding

Zigzag structure carbon atoms form a zigzag pattern

Cross-linking linear chains are joined one to another by covalent bonds

Branching side-branch chains are connected to the main ones

Monomer small molecule from which a polymer is synthesized

Repeat unit long molecules repeated along a chain

Polymerization process of reacting monomer molecules together to form polymer chains

Homopolymer the repeat units are the same type

Degree of polymerization average number of repeat units in a chain

Stereoisomerism atoms are linked together in the same order

Tacticity R-groups are situated

Tacticity 3 types isotactic, syndiotactic, atactic

Tacticity - Isotactic all R-groups same side

Tacticity - Syndiotactic alternate sides of the chain

Tacticity - atactic random positioning

Geometric isomerism Chain configurations within repeat units having a double bond

Copolymers composed of two or more kinds of repeat units

Thermoplastic soften upon heating, branched structures, recycle

vacancy An atomic space missing an atom in a atomic plane

grain An individual crystal

grain boundary separating two grains

Thermosetting do not soften upon heating, crosslinked, network, not able to recycle

Crystalline polymer composed of randomly oriented molecules

Frenkel defects ionic solid, a cation vacancy and a cation interstitial pair

Schottky defects ionic solid, a defect consisting of both an anion and a cation vacancy

Arrhenius relationship between temperature and reaction rates

Activation energy Q, the energy needed to start the reaction

Diffusion transfer of mass

Grain boundary diffusion grain boundaries are a bunch of misalignments, an intermediate activation energy allows mass flow, and increases the density

grain growth grain boundary diffusion, big grains growth

interstitial diffusion Atoms go from a nterstitial position to a neighboring one that is empty

Self-diffusion atomic migrations in pure metals

Vacancy diffusion lattice position to an adjacent vacant lattice site or vacancy

Lattice diffusion atomic diffusion within a crystalline lattice

creep time dependent permanent deformation

ductility material's ability to undergo plastic deformation

elongation at fracture How much the material has plastically deformed before fracture

fatigue limit the large number of fluctuating stress that a material can endure without breaking

fracture toughness resistance to fracture

hardness resistance of surface deformation

impact toughness how much energy a material takes up when impacted

UTS ultimate tensile strength

ductile-brittle transition temperature when a material goes from ductile behavior to brittle behavior

viscoelasticity type of deformation of both viscous flow and elastic deformation

ductility ability to undergo appreciable plastic deformation

resilience capacity to absorb energy

glass transition transition upon cooling when a polymer goes from liquid to rubbery to a rigid solid

slip plastic deformation as the result of dislocation motion

twin formation Forms between two crystals pieces who mirror images of each other

grain boundary strengthening changing crystalline grain sizes and therefore modifying the overall grain boundary are

solution hardening adding impurity atoms

strain hardening movement of dislocations and generation of new ones

cold working plastic deformation of a metal at a temperature below that at which it recrystallize

annealing metal going through a heat treatment after it has been cold-worked, recrystallize

recovery The relief of some of the internal strain energy of a previously cold-work metal, usually by heat treatment, increasing the rate of diffusion

recrystallization new strain free grain within a cold worked material

residual stresses material free of external forces or temperature gradients

vulcanizing non reversible chemical reaction involving sulfur

fracture mechanics fracture analysis

fractography study of propagation

impact toughness measure of the energy absorbed during the fracture of a specimen

fatigue failure at relatively low stress levels

crazing often occurs when fracturing some thermoplastics

Gibbs phase rule relationship between the number of phases present and the number of externally controllable variables

phase diagram: representation of the relationships among environmental constraints, compositions

binary phase diagram plots temperature against the relative concentrations of two substances

isomorphous phase diagram The same crystal structure or complete solid solubility for all compositions

solidus melting begins upon equilibrium heating or solidification is complete upon equilibrium cooling

liquidus boundary separating liquid- and liquid+solid-phase regions

solvus limit of solid solubility

eutectic lamellar microstructure microstructure composed of fine, alternating, layers of different materials in the form of lamellar

hypereutectic the concentration of solute is greater than the eutectoid composition

hypoeutectic the concentration of solute is less than the eutectoid composition

microconstituent Compound of two metals that has a distinct chemical formula

proeutectic phase starts to form just before the eutectic point

secondary phase before eutectic temperature

Eutectoid reaction upon cooling, one solid phase transforms isothermally and reversibly into two new solid phases

peritectic reaction upon cooling, a solid and a liquid phase transform isothermally and reversibly to a solid phase

congruent phase transformation same composition

ternary phase diagram three components

homogeneous nucleation away from a surface, without any impurities, only the base material.

heterogeneous nucleation nucleation sites on surfaces in the system, easier for nucleation to occur

dendrite formation dendrites can develop in one or multicomponent systems.

ferrous alloys iron based

non-ferrous alloys metal alloys with no iron

stainless steel highly resistant to corrosion

noble metals soft, ductile, and oxidation resistant, highly conductive

refractory materials metal or ceramic that may be exposed to extremely high temperatures without deteriorating rapidly or without melting

glass ceramics fine-grained crystalline ceramic material

elastomers extremely elastic polymers

heat treatment treating material with a combination of heat addition/reduction and time

quenching rapid cooling

tempering Increasing the strength of glass by heat treatment

welding technique for joining metals in which actual melting of the base material

powder pressing press powder of ceramic into the desired shape

intergranular corrosion corrosion along grain boundary regions of polycrystalline materials.

stress corrosion form of failure that results from the combined action of a tensile stress and a corrosion environment

uniform corrosion oxidation and reduction reactions occurs uniformly over surface

crevice corrosion form of corrosion that occurs within narrow crevices and under deposits of dirt

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

activation polarization condition in which the rate of an electrochemical reaction is controlled by the slowest step

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