Glossary of Terms: TMI: Technical Materials, Inc. : Clad Metal and Electroplating

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Glossary of Terms

Age Hardening (Precipitation Hardening): A process of increasing the hardness and strength by the precipitation of particles of a phase from a supersaturated solid solution alloy. The hardening cycle usually consists of heating or annealing at a temperature sufficiently high to maintain solid solution, rapid cooling or quenching to retain the supper saturated solid solution, and subsequent heating at a temperature lower than the solution anneal to effect the precipitation.
Annealing: A process involving heating and cooling designed to effect: (1) softening of a cold-worked structure by re-crystallization of grain growth or both; (2) softening of an age-hardened alloy by causing a nearly complete precipitation of the second phase in a relatively coarse form; (3) softening of certain age-hardenable alloys by dissolving the second phase and cooling rapidly enough to obtain a supersaturated solution; (4) relief of residual stress.
ASTM: Abbreviation for American Society for Testing and Materials
Blister: A void in, or raised spot on the surface of the clad caused by expansion of entrapped gas at the interface or by non-bonding.
Bonding: in the clad metals industry this refers to the initial step in the manufacturing process where ultra-clean clad and base materials are fed simultaneously into a modified rolling mill where they become metallurgically joined. This joining of clad to base metal is called bonding.
Brazing: A joining process wherein coalescence is produced by heating to suitable temperatures above 800(F and by using a non-ferrous filler metal having a melting point below that of the base metals. The filler metal is distributed between the closely filled surfaces of the joint by capillary attraction. See also soldering.
Buckle: Alternate bulges and hollows recurring along the length of a flat product with the edges remaining relatively flat.
Burr: The thin ridge or roughness left by a cutting operation such as slitting, shearing, blanking or sawing.
Chamber (Edgewise Curvature): The lateral departure of the edge from a straight line, which may be unidirectional or reversing; in the latter case, sometimes called snaking.
CDA: Abbreviation for Copper Development Association Inc.
Chatter Marks: A series of transverse ripples along the length of a rolled product caused by equipment vibration.
Clad Metal: A sophisticated composite of two or more metals, effectively combining the best qualities of the different metals - frequently at a lower cost than that for a solid metal and always conserving on precious metal usage.
Coil Set (Longitudinal Curl): A unidirectional departure from longitudinal flatness.
Cold Working: The process of changing the form or cross-section of a piece of metal at a temperature below the softening or recrystallization point, but commonly at or about room temperature. It includes rolling, drawing, pressing and stretching.
Corrosion Fatigue: The deterioration of properties resulting from repeated stressing of a metal in a corrosive medium. The rate of deterioration is greater than that resulting from either repeated stressing or corrosion alone.
Creep: The flow or plastic deformation of metals held for long periods of time, even at stresses lower than the normal yield strength. Creep is the time-dependent part of a strain resulting from any stress. The effect is particularly important if the temperature of stressing is in the vicinity of the recrystallization temperature of the metal.
Creep Strength: (1) The constant nominal stress that will cause a specified quantity of creep in a given time at constant temperature. (2) The constant nominal stress that will cause a specified creep rate at constant temperature.
Crown: The variation in thickness across the product from edge to center or edge to edge.
Dish: The transverse departure of the concave surface of the strip from a straight line from edge to edge.
Ductility: The property of a metal that permits permanent deformation before fracture by stress tension.
Elastic Limit: The greatest stress which a material is capable of sustaining without any permanent strain remaining after complete release of the stress.
Electrical Conductivity: A measure of the efficiency with which atoms in a metal transmit electrons, i.e. a metal's ability to convey an electrical current. Usually referenced to OFHC copper.
Elongation: The permanent extension of a specimen which has been stretched to rupture in a tension test. The percentage elongation is an indication of ductility.
Endurance Limit: A measure of the limit of safe loading for materials to be used under repeated, cyclic changes of stress. Expressed in psi. Properly, it is the maximum stress to which a metal can be subjected for indefinitely long periods without damage. contrast with fatigue strength.
Fatigue: The tendency for a metal to break under conditions of repeated cyclic stressing considerable below the ultimate tensile strength.
Fatigue Life: The number of stress cycles which can be sustained for a given test condition.
Fatigue Limit: The limiting value of the stress below which a material can presumably endure an infinite number of stress cycles.
Fatigue Strength: The greatest stress which can be sustained for a given number of stress cycles without fracture.
Feathered Edge: An occasional defect in clad inlays where the edge of the stripe displays loose clad. The edge appears cracked with fine lines, similar to the appearance of a feather.
Flatness: The degree to which a surface of a flat product approaches a plane.
Flux: Used when soldering or brazing, this substance is introduced to remove surface oxides and impurities and to improve wetability.
Gauge: (1) Term sometimes used to designate thickness of flat products. (2) The instrument used to measure thickness.
Gauge Number: A number in a specific series used to designate a dimension. There are several series of such gauge number, of which the most familiar are the American Wire Gauge or Brown & Sharpe and Birmingham or Stubs.
Grain: A solid polyhedral (or many sided) crystal consisting of groups of atoms bound together in a regular geometric pattern. In mill practice grains are usually studied only as they appear in one plane.
Grain Size: The average diameter of grains, usually determined microscopically, on an etched plane surface of the metal. See ASTM Designation E 112.
Grain Bond: The marginal bond which sometimes results during the initial bonding operation; the integrity of which is improved by sintering.
Hardness: The resistance of metal to plastic deformation by indentation. The most common method of measurement is Rockwell. Other methods are Brinell, Scleroscope, Tukon and Vickers.
Hardness Number: The number used to designate the hardness of metal. The number is related to the scale of values of a particular hardness test, as Rockwell B 80 or Brinell 150.
Hydrogen Embrittlement: In oxygen-bearing copper, a condition of low ductility resulting from absorption of hydrogen at high temperature. Internal reduction of cuprous oxide and creation of intergranular holes or cracks by the accompanying generation of steam.
IACS: Abbreviation for International Annealed Copper Standard.
Inclusions: Particles of foreign material (usually chips, dirt, carbon, oxides) that are held mechanically on or within the metal.
Intercrystalline Cracking: Fracture of metal that follows along the grain boundaries and between crystals or grains.
Interface: The boundary between the bonded metals. In this region considerable diffusion has taken place between the two metals.
Mill Hardening: This is the same process as age hardening. The difference lies in that mill hardening is done by the vendor before subsequent forming of the material.
Modulus of Elasticity (Young's Modulus): E, the ration of stress to corresponding strain below the proportional limit. It is a measure of stiffness.; Note: The stress-strain relationship of copper and copper alloys under tension at normal room temperature does not conform to Hooke's Law throughout the elastic range. The modulus values in common use are derived from the approximately linear relationship measured in the lower range of tension test loading.
Orange Peel Surface: The surface roughness resulting from working metal of large grain size. The surface is similar in texture to an orange peel.
Platers' Bar: A rectangular section, specially surfaced, for use as a base to which precious metal is to be applied before rerolling, for the jewelry and similar trades.
Recrystallization: The change in grain structure which occurs when the metal is annealed; during which grains, deformed and strain hardened by working, becomes new equiaxed unstrained grains. This results in decreased hardness and tensile strength together with an increase in the ductility. Recrystalization is a function of time, temperature and percent reduction.
Reduction of Area: (1) The decrease in a cross-section of a product by rolling or drawing. This is a measure of the temper of metal in the cold worked condition. (2.) The difference between the original cross-section area of a tension test specimen and the area of its smallest cross-section measured aftr fracture. The reduction of area is usually expressed as a percentage of the original cross-sectional area of the specimen. It is a criterion of ductility.
Ripple: A slight transverse wave or shadow mark repeated at internals, sometimes observed on flat products.
Rolling: The process of passing metal between rolls under pressure to reduce its cross-section.
Roll Mark: Imperfections introduced on the surface of a rolled product caused by defects and wear patterns in the surface of the rolls.
Season Cracking: Spontaneous failure of some metals by cracking under the combined action of corrosion and residual stresses. Season cracking can be prevented by relief annealing which removes entirely or reduces to a safe limit the residual stresses without affecting the temper and physical properties of the material.
Sinter: Securing the bond at elevated temperatures where diffusion causes the metal atoms of the bonded components to intermingle.
Skiving: A continuous machining using a form tool that cuts a trough in the surface of base metal strip stock into which the cladding metal is inlayed and subsequently bonded.
Soldering: Joining metals by fusion of alloys that have relativelylow mlting points - most commonly, lead-base or tin-base alloys, which are the soft solders. Hard solders are alloys that have silver, copper or nickel bases. Use of these alloys with melting points higher than 800(F, 427(C is properly called "Brazing".
Solder Reflow: A process which produces solder bonded to a base metal in a specific location. Parts fabricated from this material can therefore be solder assembled simply by applying flux and heat.
Spill: A defect which originates during casting and after rolling or drawing appears as a discontinuity either on the surface or as a faint streak which on distortion becomes open or blistered.
Strain: The measure of change in size or shape of a body caused by the application of a load, referred to its original size or shape. Strain is a nondimensional quantity, but is often expressed in inches per inch.
Stresses: (1) Applied Stress - Stresses that are set up and exist in a body during application of an external load. (2) Residual Stress - Stresses that remain within a body as the result of plastic deformation, casting or rapid temperature change. Stress expressed in force per unit area (pounds per square inch).
Stress Corrosion: The combined action of a specific corrodant and applied stresses that may result in spontaneous cracking of some metals.
Surface Roughness: An indication of surface irregularity measured by the root-mean square (rms) of the surface variations. Typical values for commercial spring materials run 4-8 rms.
Temper: The condition produced in a metal by thermal and/or mechanical treatment resulting in characteristic structure and mechanical properties.
Tensile Strength: The value obtained by dividing the maximum load observed during tensile straining by the specimen cross-sectional area before straining. Also called "Ultimate Strength". It is usually expressed in pounds per square inch.
Tests: (1) Bend - A test sometimes made to indicate ductility or bending quality by bending a suitable specimen about a predetermined radius through a predetermined angle.; (2) Brinell Hardness - A test made to determine hardness on relatively thick sections of metal by pressing a steel ball of specified diameter into a test specimen under a specified load. This test is seldom used on copper and copper-base alloys. See ASTM Designation E 10.; (3) Creep - A test to determine the extension of metallic materials due to the combined effects of temperature, tensile stress and time. Inherently, it is a long term test not suitable for specification purposes. See ASTM Designation E 22.; (4) Cup - A test to indicate the ductility of sheet or strip wherein a cup is drawn from the metal until it fractures. Several modifications of the original Erichsen method are now in use. See ASTM Designation A 344.; (5) Endurance - A test to determine the endurance limit of a metal's resistance to fatigue by subjecting a specimen to repeated alternating or pulsating stresses.; (6) Impact - A test made to determine the resistance of metals to failure by sudden shock load. See ASTM Designation E 23.; (7) Rockwell Hardness - A test to measure hardness by determining the depth of penetration into a specimen of a penetrator under predetermined conditions of test. See ASTM Designation E 17.; (8) Tension - A test to determine one or more of the following: tensile strength, yield strength, elongation and reduction of area. See ASTM Designation E 8.; (9) Torsion - A test to determine the strength in torsion by measuring the torque required to twist a specimen of given length through a predetermined angle.
Thermal Coefficient of Expansion: A measure of the dimensional change of a metal with temperature, caused by changes in the magnitude of atomic vibration that affect the atomic spacing.
Thermal Conductivity: A measure of the efficiency with which atoms in a metal transmit thermal activity.
Wavy Edges: A wrinkled condition along the edges of the product, with a relatively flat center portion.
Yield Point: The first stress in a material at which an increase in strain occurs without an increase in stress.
Yield Stress: The stress at which a material exhibits a specified deviation from proportionality of stress and strain.

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