A B C DE F G H I J K L M N O P Q R Sa-Sq St-Sy T U V W X Y Z
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abrasion
A process in which hard particles or protuberances are forced against and moved along a solid surface. (2) A roughening or scratching of a surface due to abrasive wear. (3) The process of grinding or wearing away through the use of abrasives.
abrasive
A hard substance used for grinding, honing, lapping, superfinishing, polishing, pressure blasting, or barrel finishing. Abrasives in common use are alumina, silicon carbide, boron carbide, diamond, cubic boron nitride, garnet, and quartz. (2) Hard particles, such as rocks, sand, or fragments of certain hard metals, that wear away a surface when they move across it under pressure. See also superabrasives.
abrasive belt
A coated abrasive product, in the form of a belt, used in production grinding and polishing.
abrasive blasting
A process for cleaning or finishing by means of an abrasive directed at high velocity against the workpiece.
abrasive disk
A grinding wheel that is mounted on a steel plate, with the exposed flat side being used for grinding. (2) A disk-shaped, coated abrasive product.
abrasive erosion
Erosive wear caused by the relative motion of solid particles that are entrained in a fluid, moving nearly parallel to a solid surface. See also erosion.
abrasive flow machining
Removal of material by a viscous, abrasive media flowing under pressure through or across a workpiece.
abrasive jet machining
Material removal from a workpiece by impingement of fine abrasive particles that are entrained in a focused, high-velocity gas stream.
abrasive machining
A machining process in which the points of abrasive particles are used as machining tools.
abrasive wear
The removal of material from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being abraded. Compare with adhesive wear .
abrasive wheel
A grinding wheel composed of an abrasive grit and a bonding agent.
absolute density
See density, absolute.
Accm, Ac1, Ac3, Ac4
Defined under transformation temperature.
accelerated corrosion test
Method designed to approximate, in a short time, the deteriorating effect under normal long-term service conditions.
accelerated-life test
A method designed to approximate, in a short time, the deteriorating effect obtained under normal long-term service conditions. See also artificial aging.
accelerated testing
A test performed on materials or assemblies that is meant to produce failures caused by the same failure mechanism as expected in field operation but in significantly shorter time. The failure mechanism is accelerated by changing one or more of the controlling test parameters.
acicular ferrite
A highly substructured nonequiaxed ferrite formed upon continuous cooling by a mixed diffusion and shear mode of transformation that begins at a temperature slightly higher than the transformation temperature range for upper bainite. It is distinguished from bainite in that it has a limited amount of carbon available; thus, there is only a small amount of carbide present.
acicular ferrite steels
Ultralow-carbon (<0.08%) steels having a microstructure consisting of either acicular ferrite (low-carbon bainite) or a mixture of acicular and equiaxed ferrite.
acid
A chemical substance that yields hydrogen ions (H+) when dissolved in water. Compare with base . (2) A term applied to slags, refractories, and minerals containing a high percentage of silica.
acid bottom and lining
The inner bottom and lining of a melting furnace, consisting of materials like sand, siliceous rock, or silica brick that give an acid reaction at the operating temperature.
acid copper
(1) Copper electrodeposited from an acid solution of a copper salt, usually copper sulfate. (2) The solution referred to in (1).
acid embrittlement
A form of hydrogen embrittlement that may be induced in some metals by acid.
acid rain
Atmospheric precipitation with a pH below 5.6 to 5.7. Burning of fossil fuels for heat and power is the major factor in the generation of oxides of nitrogen and sulfur, which are converted into nitric and sulfuric acids washed down in the rain. See also atmospheric corrosion.
acid refractory
Siliceous ceramic materials of a high melting temperature, such as silica brick, used for metallurgical furnace linings. Compare with basic refractories.
acid steel
Steel melted in a furnace with an acid bottom and lining and under a slag containing an excess of an acid substance such as silica.
acoustic emission
A measure of integrity of a material, as determined by sound emission when a material is stressed. Ideally, emissions can be correlated with defects and/or incipient failure.
actinide metals
The group of radioactive elements of atomic numbers 89 through 103 of the periodic system–namely, actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium.
activated rosin flux
A rosin-base flux containing an additive that increases wetting by the solder.
activation
(1) The changing of a passive surface of a metal to a chemically active state. Contrast with passivation . (2) The (usually) chemical process of making a surface more receptive to bonding with a coating or an encapsulating material.
activation energy
The energy required for initiating a metallurgical reaction–for example, plastic flow, diffusion, chemical reaction. The activation energy may be calculated from the slope of the line obtained by plotting the natural log of the reaction rate versus the reciprocal of the absolute temperature.
active
The negative direction of electrode potential. Also used to describe corrosion and its associated potential range when an electrode potential is more negative than an adjacent depressed corrosion rate (passive) range.
active metal
A metal ready to corrode or being corroded.
activity
A measure of the chemical potential of a substance, where the chemical potential is not equal to concentration, that allows mathematical relations equivalent to those for ideal systems to be used to correlate changes in an experimentally measured quantity with changes in chemical potential.
addition agent
(1) A substance added to a solution for the purpose of altering or controlling a process. Examples: wetting agents in acid pickles; brighteners or antipitting agents in plating solutions; inhibitors. (2) Any material added to a charge of molten metal in a bath or ladle to bring the alloy to specification.
adhesion
(1) In frictional contacts, the attractive force between adjacent surfaces. In physical chemistry, adhesion denotes the attraction between a solid surface and a second (liquid or solid) phase. This definition is based on the assumption of a reversible equilibrium. In mechanical technology, adhesion is generally irreversible. In railway engineering, adhesion often means friction. (2) Force of attraction between the molecules (or atoms) of two different phases. Contrast with cohesion . (3) The state in which two surfaces are held together by interfacial forces, which may consist of valence forces, interlocking action, or both.
adhesive
A substance capable of holding materials together by surface attachment. Adhesive is a general term and includes, among others, cement, glue, mucilage, and paste.
adhesive bonding
A materials joining process in which an adhesive, placed between the faying surfaces (adherends), solidifies to produce an adhesive bond.
adhesive wear
(1) Wear by transference of material from one surface to another during relative motion due to a process of solid-phase welding. Particles that are removed from one surface are either permanently or temporarily attached to the other surface. (2) Wear due to localized bonding between contacting solid surfaces leading to material transfer between the two surfaces or loss from either surface. Compare with abrasive wear.
adjustable bed
Bed of a press designed so that the die space height can be varied conveniently.
Aecm, Ae1, Ae3, Ae4
Defined under transformation temperature.
age hardening
Hardening by aging (heat treatment) usually after rapid cooling or cold working.
age softening
Spontaneous decrease of strength and hardness that takes place at room temperature in certain strain hardened alloys, especially those of aluminum.
aging
(1) The effect on materials of exposure to an environment for a prolonged interval of time. (2) The process of exposing materials to an environment for a prolonged interval of time in order to predict in-service lifetime.
aging (heat treatment)
A change in the properties of certain metals and alloys that occurs at ambient or moderately elevated temperatures after hot working or a heat treatment (quench aging in ferrous alloys, natural or artificial aging in ferrous and nonferrous alloys) or after a cold-working operation (strain aging). The change in properties is often, but not always, due to a phase change (precipitation), but never involves a change in chemical composition of the metal or alloy. See also age hardening , artificial aging , interrupted aging , natural aging , overaging , precipitation hardening , precipitation heat treatment , progressive aging , quench aging , step aging , and strain aging.
air acetylene welding
A fuel gas welding process in which coalescence is produced by heating with a gas flame or flames obtained from the combustion of acetylene with air, without the application of pressure, and with or without the use of filler metal.
air bend die
Angle-forming dies in which the metal is formed without striking the bottom of the die. Metal contact is made at only three points in the cross section: the nose of the male die and the two edges of a V-shape die opening.
air bending
Bending in an air bend die.
air carbon arc cutting
An arc cutting process in which metals to be cut are melted by the heat of a carbon arc and the molten metal is removed by a blast of air.
air classification
The separation of metal powder into particle-size fractions by means of an air stream of controlled velocity; an application of the principle of elutriation.
air-hardening steel
A steel containing sufficient carbon and other alloying elements to harden fully during cooling in air or other gaseous media from a temperature above its transformation range. The term should be restricted to steels that are capable of being hardened by cooling in air in fairly large sections, about 50 mm (2 in.) or more in diameter. Same as self-hardening steel.
air-lift hammer
A type of gravity-drop hammer in which the ram is raised for each stroke by an air cylinder. Because length of stroke can be controlled, ram velocity and therefore the energy delivered to the workpiece can be varied. See also drop hammer and gravity hammer.
alclad
Composite wrought product comprised of an aluminum alloy core having one or both surfaces a metallurgically bonded aluminum or aluminum alloy coating that is anodic to the core and thus electrochemically protects the core against corrosion.
alkali metal
A metal in group IA of the periodic system–namely, lithium, sodium, potassium, rubidium, cesium, and francium. They form strongly alkaline hydroxides, hence the name.
alkaline cleaner
A material blended from alkali hydroxides and such alkaline salts as borates, carbonates, phosphates, or silicates. The cleaning action may be enhanced by the addition of surface-active agents and special solvents.
alkaline earth metal
A metal in group IIA of the periodic system–namely, beryllium, magnesium, calcium, strontium, barium, and radium–so called because the oxides or “earths” of calcium, strontium, and barium were found by the early chemists to be alkaline in reaction.
alligatoring
(1) Pronounced wide cracking over the entire surface of a coating having the appearance of alligator hide. (2) The longitudinal splitting of flat slabs in a plane parallel to the rolled surface. Also called fish-mouthing.
alligator skin
See orange peel.
allotriomorphic crystal
A crystal whose lattice structure is normal but whose external surfaces are not bounded by regular crystal faces; rather, the external surfaces are impressed by contact with other crystals or another surface such as a mold wall, or are irregularly shaped because of nonuniform growth. Compare with idiomorphic crystal.
allotropy
(1) A near synonym for polymorphism . Allotropy is generally restricted to describing polymorphic behavior in elements, terminal phases, and alloys whose behavior closely parallels that of the predominant constituent element. (2) The existence of a substance, especially an element, in two or more physical states (for example, crystals).
allowance
(1) The specified difference in limiting sizes (minimum clearance or maximum interference) between mating parts, as computed arithmetically from the specified dimensions and tolerances of each part. (2) In a foundry, the specified clearance. The difference in limiting sizes, such as minimum clearance or maximum interference between mating parts, as computed arithmetically. See also tolerance.
alloy
(1) A substance having metallic properties and being composed of two or more chemical elements of which at least one is a metal. (2) To make or melt an alloy.
alloy cast iron
Highly alloyed cast irons containing more than 3% alloy content. Alloy cast irons may be of a type of white iron, gray iron, or ductile iron.
alloying element
An element added to and remaining in a metal that changes structure and properties.
alloy plating
The codeposition of two or more metallic elements.
alloy powder, alloyed powder
A metal powder consisting of at least two constituents that are partially or completely alloyed with each other.
alloy steel
Steel containing specified quantities of alloying elements (other than carbon and the commonly accepted amounts of manganese, copper, silicon, sulfur, and phosphorus) within the limits recognized for constructional alloy steels, added to effect changes in mechanical or physical properties.
alloy system
A complete series of compositions produced by mixing in all proportions any group of two or more components, at least one of which is a metal.
all-weld-metal test specimen
A test specimen wherein the portion being tested is composed wholly of weld metal.
alpha brass
A solid-solution phase of one or more alloying elements in copper having the same crystal lattice as copper.
alpha ferrite
See ferrite.
alpha iron
The body-centered cubic form of pure iron, stable below 910 °C (1670 °F).
alternate immersion test
A corrosion test in which the specimens are intermittently exposed to a liquid medium at definite time intervals.
aluminizing
Forming of an aluminum or aluminum alloy coating on a metal by hot dipping, hot spraying, or diffusion.
amalgam
A dental alloy produced by combining mercury with alloy particles of silver, tin, copper, and sometimes zinc.
amorphous
Not having a crystal structure; noncrystalline.
amorphous solid
A rigid material whose structure lacks crystalline periodicity; that is, the pattern of its constituent atoms or molecules does not repeat periodically in three dimensions. See also metallic glass.
anelastic deformation
Any portion of the total deformation of a body that occurs as a function of time when load is applied and which disappears completely after a period of time when the load is removed.
anelasticity
The property of solids by virtue of which strain is not a single-value function of stress in the low-stress range where no permanent set occurs.
angle of bite
In the rolling of metals, the location where all of the force is transmitted through the rolls; the maximum attainable angle between the roll radius at the first contact and the line of roll centers. Operating angles less than the angle of bite are termed contact angles or rolling angles.
angle of nip
In rolling, the angle of bite. In roll, jaw, or gyratory crushing, the entrance angle formed by the tangents at the two points of contact between the working surfaces and the (assumed) spherical particles to be crushed.
angstrom (unit)
A unit of linear measure equal to 10-10 m, or 0.1 nm (nanometer), sometimes used to express small distances such as interatomic distances and some wavelengths.
anion
A negatively charged ion that migrates through the electrolyte toward the anode under the influence of a potential gradient. See also cation and ion.
anisotropy
The characteristic of exhibiting different values of a property in different directions with respect to a fixed reference system in the material.
annealing
A generic term denoting a treatment consisting of heating to and holding at a suitable temperature followed by cooling at a suitable rate, used primarily to soften metallic materials, but also to simultaneously produce desired changes in other properties or in microstructure. The purpose of such changes may be, but is not confined to: improvement of machinability, facilitation of cold work, improvement of mechanical or electrical properties, and/or increase in stability of dimensions. When the term is used unqualifiedly, full annealing is implied. When applied only for the relief of stress, the process is properly called stress relieving or stress-relief annealing.
In ferrous alloys, annealing usually is done above the upper critical temperature, but the time-temperature cycles vary widely both in maximum temperature attained and in cooling rate employed, depending on composition, material condition, and results desired. When applicable, the following commercial process names should be used: black annealing, blue annealing, box annealing, bright annealing, cycle annealing, flame annealing, full annealing, graphitizing, in-process annealing, isothermal annealing, malleabilizing, orientation annealing, process annealing, quench annealing, spheroidizing, subcritical annealing.
In nonferrous alloys, annealing cycles are designed to: (a) remove part or all of the effects of cold working (recrystallization may or may not be involved); (b) cause substantially complete coalescence of precipitates from solid solution in relatively coarse form; or (c) both, depending on composition and material condition. Specific process names in commercial use are final annealing, full annealing, intermediate annealing, partial annealing, recrystallization annealing, stress-relief annealing, anneal to temper.
annealing carbon
See temper carbon.
annealing twin
A twin formed in a crystal during recrystallization.
anneal to temper
A final partial anneal that softens a cold-worked nonferrous alloy to a specified level of hardness or tensile strength.
anode
(1) The electrode of an electrolyte cell at which oxidation occurs. Electrons flow away from the anode in the external circuit. It is usually at the electrode that corrosion occurs and metal ions enter solution. (2) The positive (electron-deficient) electrode in an electrochemical circuit. Contrast with cathode.
anode copper
Special-shaped copper slabs, resulting from the refinement of blister copper in a reverberatory furnace, used as anodes in electrolytic refinement.
anode effect
The effect produced by polarization of the anode in electrolysis. It is characterized by a sudden increase in voltage and a corresponding decrease in amperage due to the anode becoming virtually separated from the electrolyte by a gas film.
anode efficiency
Current efficiency at the anode.
anode film
(1) The portion of solution in immediate contact with the anode, especially if the concentration gradient is steep. (2) The outer layer of the anode itself.
anode polarization
See polarization.
anodic cleaning
Electrolytic cleaning in which the work is the anode. Also called reverse-current cleaning.
anodic coating
A film on a metal surface resulting from an electrolytic treatment at the anode.
anodic pickling
Electrolytic pickling in which the work is the anode.
anodic polarization
The change of the electrode potential in the noble (positive) direction due to current flow. See also polarization.
anodic protection
(1) A technique to reduce the corrosion rate of a metal by polarizing it into its passive region, where dissolution rates are low. (2) Imposing an external electrical potential to protect a metal from corrosive attack. (Applicable only to metals that show active-passive behavior.) Contrast with cathodic protection.
anodic reaction
Electrode reaction equivalent to a transfer of positive charge from the electronic to the ionic conductor. An anodic reaction is an oxidation process. An example common in corrosion is M(s) M(aq)2+ + 2e-.
anodizing
Forming a conversion coating on a metal surface by anodic oxidation; most frequently applied to aluminum.
anolyte
The electrolyte adjacent to the anode in an electrolytic cell.
antiferromagnetic material
A material wherein interatomic forces hold the elementary atomic magnets (electron spins) of a solid in alignment, a state similar to that of a ferromagnetic material but with the difference that equals numbers of elementary magnets (spins) face in opposite directions and are antiparallel, causing the solid to be weakly magnetic, that is, paramagnetic, instead of ferromagnetic.
antifriction material
A material that exhibits low-friction or self-lubricating properties.
antipitting agent
An addition agent for electroplating solutions to prevent the formation of pits or large pores in the electrodeposit.
anvil
A large, heavy metal block that supports the frame structure and holds the stationary die of a forging hammer. Also, the metal block on which blacksmith forgings are made.
anvil cap
Same as sow block.
apparent density
(1) The weight per unit volume of a powder, in contrast to the weight per unit volume of the individual particles. (2) The weight per unit volume of a porous solid, where the unit volume is determined from external dimensions of the mass. Apparent density is always less than the true density of the material itself.
Arcm, Ar1, Ar3, Ar4, Ar’, Ar”
Defined under transformation temperature.
arbor
(1) In machine grinding, the spindle on which the wheel is mounted. (2) In machine cutting, a shaft or bar for holding and driving the cutter. (3) In founding, a metal shape embedded in green sand or dry sand cores to support the sand or the applied load during casting.
arbor press
A machine used for forcing arbors or mandrels into drilled or bored parts preparatory to turning or grinding. Also used for forcing bushings, shafts, or pins into or out of holes.
arbor-type cutter
A cutter having a hole for mounting on an arbor and usually having a keyway for a driving key.
arc
A luminous discharge of electrical current crossing the gap between two electrodes.
arc blow
The deflection of an electric arc from its normal path because of magnetic forces.
arc brazing
A brazing process in which the heat required is obtained from an electric arc.
arc cutting
A group of cutting processes that melt the metals to be cut with the heat of an arc between an electrode and the base metal. See carbon arc cutting , metal arc cutting , gas metal arc cutting , gas tungsten arc cutting , plasma arc cutting , and air carbon arc cutting . Compare with oxygen arc cutting.
arc furnace
A furnace in which metal is melted either directly by an electric arc between an electrode and the work or indirectly by an arc between two electrodes adjacent to the metal.
arc gouging
An arc cutting process variation used to form a bevel or groove.
arc melting
Melting metal in an electric arc furnace.
arc oxygen cutting
See preferred term oxygen arc cutting.
arc plasma
See plasma arc cutting .
arc seam weld
A seam weld make by an arc welding process.
arc spot weld
A spot weld made by an arc welding process.
arc spraying (ASP)
A thermal spraying process using an arc between two consumable electrodes of surfacing materials as a heat source and a compressed gas to atomize and propel the surfacing material to the substrate.
arc strike
A discontinuity consisting of any localized remelted metal, heat-affected metal, or change in the surface profile of any part of a weld or base metal resulting from an arc.
arc welding
A group of welding processes that produce coalescence of metals by heating them with an arc, with or without the application of pressure, and with or without the use of filler metal.
arc welding electrode
See electrode (welding).
argon oxygen decarburization (AOD)
A secondary refining process for the controlled oxidation of carbon in a steel melt. In the AOD process, oxygen, argon, and nitrogen are injected into a molten metal bath through submerged, side-mounted tuyeres.
artifact
A feature of artificial character, such as a scratch or a piece of dust on a metallographic specimen, that can be erroneously interpreted as a real feature.
artificial aging
Aging above room temperature. See aging (heat treatment) . Compare with natural aging.
as-cast condition
Castings as removed from the mold without subsequent heat treatment.
as-welded
The condition of weld metal, welded joints, and weldments after welding, but prior to any subsequent thermal, mechanical, or chemical treatments.
athermal transformation
A reaction that proceeds without benefit of thermal fluctuations–that is, thermal activation is not required. Such reactions are diffusionless and can take place with great speed when the driving force is sufficiently high. For example, many martensitic transformations occur athermally on cooling, even at relatively low temperatures, because of the progressively increasing drive force. In contrast, a reaction that occurs at constant temperature is an isothermal transformation; thermal activation is necessary in this case and the reaction proceeds as a function of time.
atmospheric corrosion
The gradual degradation or alteration of a material by contact with substances present in the atmosphere, such as oxygen, carbon dioxide, water vapor, and sulfur and chlorine compounds.
atmospheric riser
A riser that uses atmospheric pressure to aid feeding. Essentially, a blind riser into which a small core or rod protrudes; the function of the core or rod is to provide an open passage so that the molten interior of the riser will not be under a partial vacuum when metal is withdrawn to feed the casting but will always be under atmospheric pressure.
atomic number (Z)
The number of protons in an atomic nucleus, which determines the individuality of the atom as a chemical element.
atomic percent
The number of atoms of an element in a total of 100 representative atoms of a substance.
atomization
The disintegration of a molten metal into particles by a rapidly moving gas or liquid stream or by other means.
attritious wear
Wear of abrasive grains in grinding such that the sharp edges gradually become rounded. A grinding wheel that has undergone such wear usually has a glazed appearance.
attritor
A high-intensity ball mill whose drum is stationary and whose balls are agitated by rotating baffles, paddles, or rods at right angle to the drum axis.
attritor grinding
The intensive grinding or alloying in an attritor. Examples: milling of carbides and binder metal powders and mechanical alloying of hard dispersoid particles with softer metal or alloy powders. See also mechanical alloying.
Auger electron
An electron emitted from an atom with a vacancy in an inner shell. Auger electrons have a characteristic energy detected as peaks in the energy spectra of the secondary electrons generated.
Auger electron spectroscopy (AES)
A technique for chemical analysis of surface layers that identifies the atoms present in a layer by measuring the characteristic energies of their Auger electrons.
ausforming
Thermomechanical treatment of steel in the metastable austenitic condition below the recrystallization temperature followed by quenching to obtain martensite and/or bainite.
austempered ductile iron
A moderately alloyed ductile iron that is austempered for high strength with appreciable ductility. See also austempering.
austempering
A heat treatment for ferrous alloys in which a part is quenched from the austenitizing temperature at a rate fast enough to avoid formation of ferrite or pearlite and then held at a temperature just above Ms until transformation to bainite is complete. Although designated as bainite in both austempered steel and austempered ductile iron (ADI), austempered steel consists of two phase mixtures containing ferrite and carbide, while austempered ductile iron consists of two phase mixtures containing ferrite and austenite.
austenite
A solid solution of one or more elements in face-centered cubic iron (gamma iron). Unless otherwise designated (such as nickel austenite), the solute is generally assumed to be carbon.
austenitic grain size
The size attained by the grains in steel when heated to the austenitic region. This may be revealed by appropriate etching of cross sections after cooling to room temperature.
austenitic manganese steel
A wear-resistant material containing about 1.2% C and 12% Mn. Used primarily in the fields of earthmoving, mining, quarrying, railroading, ore processing, lumbering, and in the manufacture of cement and clay products. Also known as Hadfield steel.
austenitic steel
An alloy steel whose structure is normally austenitic at room temperature.
austenitizing
Forming austenite by heating a ferrous alloy into the transformation range (partial austenitizing) or above the transformation range (complete austenitizing). When used without qualification, the term implies complete austenitizing.
autogenous weld
A fusion weld made without the addition of filler metal.
automatic press
A press in which the work is fed mechanically through the press in synchronism with the press action. An automation press is an automatic press that, in addition, is provided with built-in electrical and pneumatic control equipment.
automatic welding
Welding with equipment that performs the welding operation without adjustment of the controls by a welding operator. The equipment may or may not load and unload the workpieces. Contrast with machine welding.
auxiliary anode
In electroplating, a supplementary anode positioned so as to raise the current density on a certain area of the cathode and thus obtain better distribution of plating.
auxiliary electrode
An electrode commonly used in polarization studies to pass current to or from a test electrode. It is usually made from a noncorroding material.
axial rolls
In ring rolling, vertically displaceable, taped rolls mounted in a horizontally displaceable frame opposite to, but on the same centerline as, the main roll and rolling mandrel. The axial rolls control ring height during rolling.