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IACS
International annealed copper standard; a standard reference used in reporting electrical conductivity. The conductivity of a material, in %IACS, is equal to 1724.1 divided by the electrical resistivity of the material in n · m.
ideal critical diameter (DI)
Under an ideal quench condition, the bar diameter that has 50% martensite at the center of the bar when the surface is cooled at an infinitely rapid rate (that is, when H = , where H is the quench severity factor or Grossmann number ).
idiomorphic crystal
An individual crystal that has grown without restraint so that the habit planes are clearly developed. Compare with allotriomorphic crystal.
immersed-electrode furnace
A furnace used for liquid carburizing of parts by heating molten salt baths with the use of electrodes immersed in the liquid. See also submerged-electrode furnace.
immersion cleaning
Cleaning in which the work is immersed in a liquid solution.
immersion coating
A coating produced in a solution by chemical or electrochemical action without the use of external current.
immersion plating
Depositing a metallic coating on a metal immersed in a liquid solution, without the aid of an external electric current. Also called dip plating.
impact energy
The amount of energy, usually given in joules or foot-pound force, required to fracture a material, usually measured by means of an Izod test or Charpy test. The type of specimen and test conditions affect the values and therefore should be specified.
impact extrusion
The process (or resultant product) in which a punch strikes a slug (usually unheated) in a confining die. The metal flow may be either between punch and die or through another opening. The impact extrusion of unheated slugs is often called cold extrusion.
impact line
A blemish on a drawn sheet metal part caused by a slight change in metal thickness. The mark is called an impact line when it results from the impact of the punch on the blank; it is called a recoil line when it results from transfer of the blank from the die to the punch during forming, or from a reaction to the blank being pulled sharply through the draw ring.
impact load
An especially severe shock load such as that caused by instantaneous arrest of a falling mass, by shock meeting of two parts (in a mechanical hammer, for example), or by explosive impact, in which there can be an exceptionally rapid buildup of stress.
impact strength
A measure of the resiliency or toughness of a solid. The maximum force or energy of a blow (given by a fixed procedure) that can be withstood without fracture, as opposed to fracture strength under a steady applied force.
impact test
A test for determining the energy absorbed in fracturing a test piece at high velocity, as distinct from static test. The test may be carried out in tension, bending, or torsion, and the test bar may be notched or unnotched. See also Charpy test , impact energy , and Izod test.
impact wear
Wear of a solid surface resulting from repeated collisions between that surface and another solid body. The term erosion is preferred in the case of multiple impacts and when the impacting body or bodies are very small relative to the surface being impacted.
impingement
A process resulting in a continuing succession of impacts between liquid or solid particles and a solid surface.
impingement attack
Corrosion associated with turbulent flow of liquid. May be accelerated by entrained gas bubbles. See also erosion-corrosion and impingement corrosion.
impingement corrosion
A form of erosion-corrosion generally associated with the local impingement of a high-velocity, flowing fluid against a solid surface.
impingement erosion
Loss of material from a solid surface due to liquid impingement. See also erosion.
impregnation
(1) Treatment of porous castings with a sealing medium to stop pressure leaks. (2) The process of filling the pores of a sintered compact, usually with a liquid such as a lubricant. (3) The process of mixing particles of a nonmetallic substance in a cemented carbide matrix, as in diamond-impregnated tools.
impression-die forging
A forging that is formed to the required shape and size by machined impressions in specially prepared dies that exert three-dimensional control on the workpiece.
impurities
(1) Elements or compounds whose presence in a material is undesirable. (2) In a chemical or material, minor constituent(s) or component(s) not included deliberately; usually to some degree or above some level, undesirable.
inclinable press
A press that can be inclined to facilitate handling of the formed parts. See also open-back inclinable press.
inclusion
(1) A physical and mechanical discontinuity occurring within a material or part, usually consisting of solid, encapsulated foreign material. Inclusions are often capable of transmitting some structural stresses and energy fields, but to a noticeably different degree than from the parent material. (2) Particles of foreign material in a metallic matrix. The particles are usually compounds, such as oxides, sulfides, or silicates, but may be of any substance that is foreign to (and essentially insoluble in) the matrix. See also exogenous inclusion , indigenous inclusion , and stringer.
inclusion count
Determination of the number, kind, size, and distribution of nonmetallic inclusions in metals.
incomplete fusion
In welding, fusion that is less than complete.
indentation hardness
(1) The resistance of a material to indentation. This is the usual type of hardness test, in which a pointed or rounded indenter is pressed into a surface under a substantially static load. (2) Resistance of a solid surface to the penetration of a second, usually harder, body under prescribed conditions. Numerical values used to express indentation hardness are not absolute physical quantities, but depend on the hardness scale used to express hardness. See also Brinell hardness test , Knoop hardness test , nanohardness test , Rockwell hardness test , and Vickers hardness test.
indenter
In hardness testing, a solid body of prescribed geometry, usually chosen for its high hardness, that is used to determine the resistance of a solid surface to penetration.
indigenous inclusion
An inclusion that is native, innate, or inherent in the molten metal treatment. Indigenous inclusions include sulfides, nitrides, and oxides derived from the chemical reaction of the molten metal with the local environment. Such inclusions are small and require microscopic magnification for identification. Compare with exogenous inclusion.
indirect-arc furnace
An electric arc furnace in which the metallic charge is not one of the poles of the arc.
indirect (backward) extrusion
See extrusion.
induction brazing
A brazing process in which the heat required is obtained from the resistance of the workpieces to induced electric current.
induction furnace
An alternating current electric furnace in which the primary conductor is coiled and generates, by electromagnetic induction, a secondary current that develops heat within the metal charge.
induction hardening
A surface-hardening process in which only the surface layer of a suitable ferrous workpiece is heated by electromagnetic induction to above the upper critical temperature and immediately quenched.
induction heating
Heating by combined electrical resistance and hysteresis losses induced by subjecting a metal to the varying magnetic field surrounding a coil carrying alternating current.
induction melting
Melting in an induction furnace.
induction soldering
A soldering process in which the heat required is obtained from the resistance of the workpieces to induced electric current.
induction tempering
Tempering of steel using low-frequency electrical induction heating.
induction welding
A welding process that produces coalescence of metals by the heat obtained from the resistance of the workpieces to the flow of induced high-frequency welding current with or without the application of pressure. The effect of the high-frequency welding current is to concentrate the welding heat at the desired location.
induction work coil
The inductor used when induction heating and melting as well as induction welding, brazing, and soldering.
inductor
A device consisting of one or more associated windings, with or without a magnetic core, for introducing inductance into an electric circuit.
industrial atmosphere
An atmosphere in an area of heavy industry with soot, fly ash, and sulfur compounds as the principal constituents.
inert anode
An anode that is insoluble in the electrolyte under the conditions prevailing in the electrolysis.
inert gas
(1) A gas, such as helium, argon, or nitrogen, that is stable, does not support combustion, and does not form reaction products with other materials. (2) In welding, a gas that does not normally combine chemically with the base metal or filler metal. See also protective atmosphere.
infiltration
The process of filling the pores of a sintered or unsintered compact with a metal or alloy of lower melting temperature.
infrared brazing
A brazing process in which the heat required is furnished by infrared radiation.
infrared soldering
A soldering process in which the heat required is furnished by infrared radiation.
infrared spectroscopy
The study of the interaction of material systems with electromagnetic radiation in the infrared region of the spectrum. The technique is useful for determining the molecular structure of organic and inorganic compounds by identifying the rotational and vibrational energy levels associated with the various molecules. See also electromagnetic radiation.
ingate
Same as gate.
ingot
A casting of simple shape, suitable for hot working or remelting.
ingot iron
Commercially pure iron.
inhibitor
A substance that retards some specific chemical reaction, e.g., corrosion. Pickling inhibitors retard the dissolution of metal without hindering the removal of scale from steel.
inoculant
Material that, when added to molten metal, modifies the structure and thus changes the physical and mechanical properties to a degree not explained on the basis of the change in composition resulting from their use. Ferrosilicon-base alloys are commonly used to inoculate gray irons and ductile irons.
inoculation
The addition of a material to molten metal to form nuclei for crystallization. See also inoculant.
insert
(1) A part formed from a second material, usually a metal, which is placed in the molds and appears as an integral structural part of the final casting. (2) A removable portion of a die or mold.
insert die
A relatively small die that contains part or all of the impression of a forging and that is fastened to a master die block.
inserted-blade cutters
Cutters having replaceable blades that are either solid or tipped and are usually adjustable.
instrumented impact test
An impact test in which the load on the specimen is continually recorded as a function of time and/or specimen deflection prior to fracture.
intense quenching
Quenching in which the quenching medium is cooling the part at a rate at least two and a half times faster than still water. See also Grossmann number.
intercept method
A quantitative metallographic technique in which the desired quantity, such as grain size or inclusion content, is expressed as the number of times per unit length a straight line on a metallographic image crosses particles of the feature being measured.
interconnected porosity
A network of connecting pores in a sintered object that permits a fluid or gas to pass through the object. Also referred to as interlocking or open porosity.
intercritical annealing
Any annealing treatment that involves heating to, and holding at, a temperature between the upper and lower critical temperatures to obtain partial austenitization, followed by either slow cooling or holding at a temperature below the lower critical temperature.
intercrystalline
Between the crystals, or grains, of a polycrystalline material.
intercrystalline corrosion
See intergranular corrosion.
intercrystalline cracking
See intergranular cracking.
interdendritic corrosion
Corrosive attack that progresses preferentially along interdendritic paths. This type of attack results from local differences in composition, such as coring commonly encountered in alloy castings.
interdendritic porosity
Voids occurring between the dendrites in cast metal.
interface
The boundary between any two phases. Among the three phases (gas, liquid, and solid), there are five types of interfaces: gas-liquid, gas-solid, liquid-liquid, liquid-solid, and solid-solid.
interfacial tension
The contractile force of an interface between two phases.
intergranular
Between crystals or grains. Also called intercrystalline. Contrast with transgranular.
intergranular corrosion
Corrosion occurring preferentially at grain boundaries, usually with slight or negligible attack on the adjacent grains. See also interdendritic corrosion.
intergranular cracking
Cracking or fracturing that occurs between the grains or crystals in a polycrystalline aggregate. Also called intercrystalline cracking. Contrast with transgranular cracking.
intergranular fracture
Brittle fracture of a polycrystalline material in which the fracture is between the grains, or crystals, that form the material. Also called intercrystalline fracture. Contrast with transgranular fracture.
intergranular penetration
In welding, the penetration of a filler metal along the grain boundaries of a base metal.
intergranular stress-corrosion cracking (IGSCC)
Stress-corrosion cracking in which the cracking occurs along grain boundaries.
intermediate annealing
Annealing wrought metals at one or more stages during manufacture and before final treatment.
intermediate electrode
Same as bipolar electrode.
intermediate phase
In an alloy or a chemical system, a distinguishable homogeneous phase whose composition range does not extend to any of the pure components of the system.
intermetallic compound
An intermediate phase in an alloy system, having a narrow range of homogeneity and relatively simple stoichiometric proportions; the nature of the atomic binding can be of various types, ranging from metallic to ionic.
intermetallic phases
Compounds, or intermediate solid solutions, containing two or more metals, which usually have compositions, characteristic properties, and crystal structures different from those of the pure components of the system.
intermittent weld
A weld in which the continuity is broken by recurring unwelded spaces.
internal friction
The conversion of energy into heat by a material subjected to fluctuating stress.
internal grinding
Grinding an internal surface such as that inside a cylinder or hole.
internal oxidation
The formation of isolated particles of corrosion products beneath the metal surface. This occurs as the result of preferential oxidation of certain alloy constituents by inward diffusion of oxygen, nitrogen, sulfur, and so forth. Also called subscale formation.
internal shrinkage
A void or network of voids within a casting caused by inadequate feeding of that section during solidification.
internal stress
See preferred term residual stress.
interpass temperature
In a multiple-pass weld, the temperature (minimum or maximum as specified) of the deposited weld metal before the next pass is started.
interrupted aging
Aging at two or more temperatures, by steps, and cooling to room temperature after each step. See also aging , and compare with progressive aging and step aging.
interrupted-current plating
Plating in which the flow of current is discontinued for periodic short intervals to decrease anode polarization and elevate the critical current density. It is most commonly used in cyanide copper plating.
interrupted quenching
A quenching procedure in which the workpiece is removed from the first quench at a temperature substantially higher than that of the quenchant and is then subjected to a second quenching system having a different cooling rate than the first.
interstitial solid solution
A type of solid solution that sometimes forms in alloy systems having two elements of widely different atomic sizes. Elements of small atomic size, such as carbon, hydrogen, and nitrogen, often dissolve in solid metals to form this solid solution. The space lattice is similar to that of the pure metal, and the atoms of carbon, hydrogen, and nitrogen occupy the spaces or interstices between the metal atoms. See also substitutional solid solution.
intracrystalline
Within or across the crystals or grains of a metal; same as transcrystalline and transgranular.
intracrystalline cracking
See transgranular cracking.
inverse chill
The condition in a casting section in which the interior is mottled or white, while the other sections are gray iron. Also known as reverse chill, internal chill, and inverted chill.
inverse segregation
A concentration of low-melting constituents in those regions of an alloy in which solidification first occurs.
investing
In investment casting, the process of pouring the investment slurry into a flask surrounding the pattern to form the mold.
investment
A flowable mixture, or slurry, of a graded refractory filler, a binder, and a liquid vehicle that, when poured around the patterns, conforms to their shape and subsequently sets hard to form the investment mold.
investment casting
(1) Casting metal into a mold produced by surrounding, or investing, an expendable pattern with a refractory slurry coating that sets at room temperature, after which the wax or plastic pattern is removed through the use of heat prior to filling the mold with liquid metal. Also called precision casting or lost wax process. (2) A part made by the investment casting process.
investment compound
A mixture of a graded refractory filler, a binder, and a liquid vehicle, used to make molds for investment casting.
investment precoat
An extremely fine investment coating applied as a thin slurry directly to the surface of the pattern to reproduce maximum surface smoothness. The coating is surrounded by a coarser, cheaper, and more permeable investment to form the mold. See also dip coat and investment casting.
investment shell
Ceramic mold obtained by alternately dipping a pattern set up in dip coat slurry and stuccoing with coarse ceramic particles until the shell of desired thickness is obtained. See also investment casting.
ion
An atom, or group of atoms, which by loss or gain of one or more electrons has acquired an electric charge. If the ion is formed from an atom of hydrogen or an atom of a metal, it is usually positively charged; if the ion is formed from an atom of a nonmetal or from a group of atoms, it is usually negatively charged. The number of electronic charges carried by an ion is termed its electrovalence. The charges are denoted by superscripts that give their sign and number; for example, a sodium ion, which carries one positive charge, is denoted by Na+; a sulfate ion, which carries two negative charges, by.
ion carburizing
A method of surface hardening in which carbon ions are diffused into a workpiece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma carburizing or glow-discharge carburizing.
ion exchange
The reversible interchange of ions between a liquid and solid, with no substantial structural changes in the solid.
ion implantation
The process of modifying the physical or chemical properties of the near surface of a solid (target) by embedding appropriate atoms into it from a beam of ionized particles.
ion nitriding
A method of surface hardening in which nitrogen ions are diffused into a workpiece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma nitriding or glow-discharge nitriding.
ion plating
A generic term applied to atomistic film deposition processes in which the substrate surface and/or the depositing film is subjected to a flux of high-energy particles (usually gas ions) sufficient to cause changes in the interfacial region or film properties.
iron casting
A part made of cast iron.
ironing
An operation used to increase the length of a tube or cup through reduction of wall thickness and outside diameter, the inner diameter remaining unchanged.
iron rot
Deterioration of wood in contact with iron-base alloys.
iron soldering
A soldering process in which the heat required is obtained from a soldering iron.
irradiation
The exposure of a material or object to x-rays, gamma rays, ultraviolet rays, or other ionizing radiation.
isocorrosion diagram
A graph or chart that shows constant corrosion behavior with changing solution (environment) composition and temperature.
isomorphous
Having the same crystal structure. This usually refers to intermediate phases that form a continuous series of solid solutions.
isostatic pressing
A process for forming a powder metallurgy compact by applying pressure equally from all directions to metal powder contained in a sealed flexible mold. See also cold isostatic pressing and hot isostatic pressing.
isothermal annealing
Austenitizing a ferrous alloy, then cooling to and holding at a temperature at which austenite transforms to a relatively soft ferrite-carbide aggregate. See also austenitizing.
isothermal forging
A hot-forging process in which a constant and uniform temperature is maintained in the workpiece during forging by heating the dies to the same temperature as the workpiece. Compare with hot-die forging.
isothermal transformation
A change in phase that takes place at a constant temperature. The time required for transformation to be completed, and in some instances the time delay before transformation begins, depends on the amount of supercooling below (or superheating above) the equilibrium temperature for the same transformation.
isothermal transformation (IT) diagram
A diagram that shows the isothermal time required for transformation of austenite to begin and to finish as a function of temperature. Same as time-temperature-transformation (TTT) diagram or S-curve.
isotropic
Having uniform properties in all directions. The measured properties of an isotropic material are independent of the axis of testing.
isotropy
The condition of having the same values of properties in all directions.
Izod test
A type of impact test in which a V-notched specimen, mounted vertically, is subjected to a sudden blow delivered by the weight at the end of a pendulum arm. The energy required to break off the free end is a measure of the impact strength or toughness of the material. Contrast with Charpy test.