The Titanium Glossary
Technical & Industrial Terminology .....for the Titanium Industry
Click on the appropriate letter below to find the word you are looking for
Alpha Alloys..... Single-phase alloys that cannot be heat treated to develop higher mechanical properties. They typically contain high amounts of aluminum used primarily to provide oxidation resistance at high temperatures. To see the U.S. alpha alloy specifications click Alpha Specifications To see the U.S. alpha alloy chemical compositions click Alpha Chemistry.
Alpha-Beta Alloys...These are two-phased alloys that allow the metal structure to be refined and to develop higher mechanical properties through heat treatment. These alloys typically contain high amounts of aluminum primarily to stabilize the alpha phase during processing stages. To see the U.S. alpha-beta alloy specifications click Alpha-Beta Specifications. To see the U.S. alpha-beta alloy chemical compositions click Alpha-Beta Chemistry.
Alpha Case..... A brittle, oxygen-enriched layer that covers the surface of titanium metal that has been heat treated (at high temperatures) in an oxygen atmosphere. The alpha case can result in embrittlement and can increase the metals susceptibility to stress corrosion. It should be removed prior to any subsequent processing or before putting the finished product into use.
Aluminum.....A master alloy element for many titanium alloys. Aluminum is used to stabilize alpha microstructures. Typical alloying weight percentages are from 2 to 7%.
AMS Specifications......A series of specifications published by the Society of Automotive Engineers and used as standards for Aerospace Material Specifications. Titanium specifications are found in the 4900 numbered series.
Beta Alloys.....These are metastable alloys that generally have increased formability properties and can generally attain high strengths through subsequent heat treatment after processing. To see the U.S. beta alloy specifications click Beta Specifications. To see the U.S. beta alloy chemical compositions click Beta Chemistry.
Beta Transus Temperature......This is the lowest equilibrium temperature of a specific material where the material is still in a 100% beta structure. Below this temperature the material is no longer 100% beta, but a mixture of alpha and beta structure. It is important to know because many processing and heat treating steps are defined by some measurement of temperature either above or below the beta transus temperature. Many mills identify the beta transus on their test reports if the customer requests this. The beta transus can also be estimated fairly accurately by using a formula.
Billet.....Describes a mill product that is generally round or round-corner squared (RCS) and runs from 4" in diameter or larger. A billet product has been hot worked by either forging, extruding or rolling process. These products are primarily used as starting stock for subsequent forging or extrusion processes.
Blasting.........A processing procedure that is used to remove scale from titanium products. It describes a mechanical grit or abrasive blasting process usually used for larger metal products like ingot and billet. Minerals such as silica, zircon and aluminum sands are used as the grit. A fine dust remains on the titanium after the blasting process. This process is usually followed by a pickling cycle to remove the dust.
British Standards Institution.......BSI maintains the basic specification standards for titanium in the United Kingdom. For more information they can be contacted at : British Standards House,
Casting.....A product that has been fabricated by pouring molten metal into an engineered mold and permitted to solidify in this configuration. Titanium castings have been successfully marketed to a broad spectrum of applications but because of titanium's reactive properties, the casting of titanium remains a complex process.
Chromium.....A master alloy element for several titanium alloys. Chromium is used to stabilize beta microstructures. Typical alloying weight percentages are from 2 to 12%.
Compact.....A product manufactured by mechanical compression of metal fines or powder into an engineered die to produce a desired shape.
Corrosion.....A condition that weakens many types of metal by certain chemical or electrochemical reactions with its environment. Many metals can wear, become embrittled and fatigued from this process. Titanium is an outstanding product when considering this issue because of its tremendous resistance to corrosion.
Creep.....A time dependant measurement of dimensional change in the size of a test specimen occurring under stress from external (usually a mechanical pull machine) forces.
DA.....This is the abbreviation for duplex annealing. Duplex annealing is a processing procedure where a second heat treatment is added to improve ductility and toughness at the cost of slightly lower strength properties.
Descale.....This is a processing term that describes any of the varied mechanical and chemical processing procedures designed to remove the thick layer of oxides formed on titanium products that are worked at high temperatures.
DMS Specifications.....A series of specifications originally published by Douglas Aerospace (now the Boeing Company) and used as standards for many of the DC and MD series commercial aircraft.
Duplex Annealed.....Duplex annealing is a processing procedure where the second heat treatment is added to improve ductility and toughness at the cost of slightly lower strength properties. The abbreviation "DA" is used on certifications and industry work orders to signify the condition of the metal as duplex annealed.
Ductility.....The measurement of a metals ability to bend or deform from stresses supplied by external forces before fracturing. The measurement is defined by elongation and reduction of area performed on a tension test.
ELI.....This is the abbreviation used to describe several titanium alloys including 6-4 ELI. ELI stands for extra low interstitials. Interstitials are the elements oxygen, nitrogen and carbon. ELI means that these interstitials have been reduced beyond the standard titanium alloy requirements to improve ductility and fracture toughness.
Embrittlement....A metal condition that causes the metal to suffer a severe loss of ductility and/or toughness. Titanium alloys are susceptible to embrittlement from several sources including hydrogen pickup (from water vapor, pickling acids, and hydrocarbons), and liquid metal embrittlement (liquid cadmium, mercury and silver).
Erosion...A metal condition that occurs from the abrasive action of moving fluids on the surface of the metal. The condition accelerates the loss of surface metal. The destruction rate is further increased when solid particles (like sand) are in the fluid solution. Many metals perform poorly under these conditions however titanium performs well in many highly erosive environments.
Extrusion.....A mill product that describes metal forms that are produced by mechanically pushing metal through a die to create a shape. There are several excellent titanium extrusion facilities throughout the United States. Extrusions have been successfully marketed throughout a wide variety of industries and applications.
Fatigue.....A metal condition that occurs when minute cracking begins to appear in the metal and progressively grow under repeated or fluctuating stresses.
Fatigue Strength.....The measurement of maximum stress a metal product can sustain for a specific number of cycles before fracturing into two pieces.
Foil.....A mill product that describes flat rolled metal forms that are defined only by a maximum thickness. Traditionally the description of titanium foil is a flat rolled product 0.005" or less in thickness. However gauges up to .010" are manufactured and marketed as foil products in various sectors of the industry.
Forging.....A semi-finished metal product that has been hot formed into an engineered shape by any one of a variety of mechanical compressive forces. Hammer forgings, open die, closed die and press forgings are some of these types.
Formability......A comparative measurement of how difficult or easy a metal alloy can be shaped with mechanical stresses.
Forming.....A processing procedure where the metal is shaped by bending or stretching the metal into an engineered shape. Sheet mill products are typically used for this process.
Fracture......A metal condition that occurs when one metal product is broken into two pieces by outside forces.
Galling......A metal condition that occurs between the facing surfaces of two mating metal products. Excessive friction between the high spots of these two products results in momentary adhesion and subsequent surface deterioration.
Grain...... The microstructure of titanium is made up of many small grains connected to each other. These grains can be seen under a microscope. Grain size and shape can be changed and controlled by specific processing procedures to enhance mechanical properties on titanium alloys.
Grinding.....A mechanical processing procedure that removes metal from the surface of a product by a variety of mechanically equipment including wheel and belt grinding.
Hardness......A comparative measurement of impact stress required to produce a level of surface deformation on a metal product. Some of the popular testing scales are Brinell and Rockwell hardness tests.
Heat-Affected Zone..... A metal condition that occurs when the microstructure and/ or mechanical properties of a localized area(s) of a metal product has been effected by previous elevated temperature processing.
Heat Treating.....A thermal processing procedure that involves an engineered plan depicting the time and rate of heating and cooling of metal products to obtain a specific level of mechanical properties.
Hogging......A mechanical processing procedure that removes (by machining) much of the original stock from the metal product.
Hot Working......A processing procedure where the metal is plastically deformed into an engineered shape at an engineered temperature and strain rate that that is designed to avoid any strain hardening.
Hydrogen Embrittlement......A metal condition that causes the metal to suffer a severe loss of ductility and/or toughness from the absorption of hydrogen from water vapor, pickling acids, or hydrocarbons.
Inclusion..... A particle of foreign material embedded within a metal product that, if left unattended could cause the material to fail. Because of the nature of titanium mill product processing most inclusions found are either oxide, sulfide, or silicate compounds.
Ingot.....A mill product that describes an as-cast product engineered for subsequent hot working or remelting processing.
Interstitial Elements......Describes elements with atoms small enough to locate within the gaps between the larger metal atoms. Examples of these are oxygen, nitrogen, hydrogen and carbon.
Investment Casting.....A processing procedure where molten metal is cast into a mold by surrounding an expendable pattern with a slurry that sets at room temperature. Subsequently the expendable pattern is removed by heat.
International Titanium Association ..... A worldwide titanium industrial trade association that contributes to the promotion of titanium products and applications through many channels including conferences, trade shows, symposiums, technical brochures, reports and visual media. The address is: 1871 Folsom Street, Suite 200 Boulder, Colorado 80302 USA. Phone: (303) 443-7515 FAX: (303) 443-4406 . Website: www.titanium.org
Japan Titanium Society (JTS)......A titanium industrial trade association that contributes to the promotion of titanium products and applications through many channels including conferences, trade shows, symposiums, technical brochures, reports and visual media. Address: 2-9, Kanda Nishiki-Cho, Chiyoda-KU, Tokyo, ZIP 101, Japan. Phone: 081-3-3295-5958 FAX 081-3-3293-6187 website: www.titan-japan.com
KIC.....A measurement of fracture toughness. The higher the KIC reading the greater the resistance to fracture.
Laser Cutting............ A popular processing procedure for close tolerance cutting of thin gauge titanium products.
Longitudinal Direction......One of three directions typically measured in a metal product. The longitudinal direction is parallel with the working of the metal product. It is easily identified in bar and billet products as parallel to the length of the product. More difficult to determine in sheet and plate products, many specifications require stenciling to be administered in the longitudinal direction to eliminate uncertainties. When viewing a product's microstructure, it is the direction parallel with the elongated grain in worked metal products.
Longitudinal Properties......A series of measurements of a metal product's properties taken in the longitudinal direction. This is significant because the properties can vary significantly depending on which directional the measurements are made.
Machinability......A measurement describing the ease of machining a specific metal in relationship to other metals.
Mechanical Properties......A series of measurements taken with the application of force to reveal a metal product's elongation, fatigue limit, hardness, modulus of elasticity, tensile strength, and yield strength.
Mill Products......Metal products that are produced in semi-finished forms but not in a final part or component shaped form. Some examples of these are billet, bar, ingot, sheet, plate, tube, foil, extrusion, and wire.
Modulus of Elasticity.....A measurement of rigidity or stiffness of a metal product.
Near-Net Shape......This describes a metal product that has been produced (usually by powder or casting processes) to dimensions that are very near to the components final (net) dimensions. This description implies minimal machining requirements to bring the component to the finished dimensions.
O.D......A measurement describing the outside diameter of a round product such as bar, billet or tubing.
Overheated......This describes the condition of a metal product that has been heated to such a high temperature that its mechanical properties have been corrupted.
Oxygen Pickup......This describes a metal condition where oxygen is absorbed into a titanium product's surface during some type of high temperature processing. The result is a detrimental hard alpha case that has embrittled the surface.
Pickling......A chemical bathing procedure used to remove the oxide film on a titanium product.
Physical Properties......A series of measurements that are unaffected by microstructure and taken without applied force to reveal a metal product's coefficient of thermal expansion, density, electrical conductivity, heat capacity, and magnetic permeability.
Plate........A mill product that is flat rolled to a specific thickness, width and length. The industry usually considers plate products as being at least .1875" (4.762mm) thick and typically produced at 36" or wider.
Powder......Small solid particles that range in size from 1 to 1000umTitanium powder metallurgy is a growing processing procedure that incorporates both forging and near-net shape technologies.
PPM.......A measurement describing the value of one element in relationship to the overall value of all elements of a given product in parts per million.
Premium Grade.......Describes a titanium product suitable for use in jet engine applications.
Quenching......A processing procedure that describes a variety of processes used to rapidly cool a metal product. The process is used to improve specific properties of a metal product.
Recrystallization......This describes the condition of a metal structure that has changed from one crystal structure to another, usually from a work-strained structure to a strain-free grain structure. The condition is attained through specific heat treatments.
Reduction in Area.....This is a measurement that describes the dimensional difference of a cross-sectional area before and after the product has been stressed to failure. The measurement is usually expressed as a percentage of the original cross-sectional dimension.
Residual Stress......A metal condition that describes internal forces within a metal product that resist the change of form that has taken place to this metal product.
Revert........Titanium products and scrap that are recycled into the production process to manufacture new mill and semi-finished products.
Rockwell Hardness Test.......A popular measurement system describing the resistance of a given metal product to surface indentation. Rockwell measurements are expressed in numbers and symbols that reflect a specific penetration devise, the amount of force applied, and the dial used to perform the measurement.
Rotor Grade........A titanium metal product that have been processed according to a specific set of procedures and approved for rotation applications within turbine engines.
RT......Abbreviation for room temperature. Measurements of titanium products properties are done at room temperature and some at specific elevated temperatures. RT is used to identify a measurement taking place at room temperature.
Scale.....A metal condition resulting from high temperature processing in an oxygen atmosphere that describes a layer of oxidation on a metal product's surface.
Sheet......A flat rolled mill product that has a width to thickness ratio greater than 50 to 1 with the thickness of the product running from .016" thick ( .406mm) to .187" thick ( 4.762mm).
Slab......An intermediate product form produced for further processing stages towards a completed flat rolled mill product like plate or sheet.
Solution Heat Treatment.....A thermal processing procedure designed to effect the crystalline structure by causing one or more structural elements to enter into solid solution and thereafter hold (by quenching) these elements in solution. The process is designed to create more attractive properties in a metal product.
Solution Heat Treatment and Aging......A thermal processing procedure designed to effect the crystalline structure by causing one or more structural elements to enter into solid solution and thereafter hold (by quenching) these elements in solution. After quenching it is aged at the standard aging temperature. The process is designed to create more attractive properties in a metal product.
Solution Heat Treatment and Overaging......A thermal processing procedure designed to effect the crystalline structure by causing one or more structural elements to enter into solid solution and thereafter hold (by quenching) these elements in solution. After quenching it is aged above the standard aging temperature. The process is designed to create more attractive properties in a metal product.
SPF.....Abbreviation for super plastic forming. This is a thermal processing procedure designed to create semi-finished components by forming them at temperatures that allow the metal to plastically form around a mold.
Sponge.......A titanium product that is produced by the decomposition of a several compound elements. It is of sufficient commercial purity that this product can be used as the primary imput to produce all subsequent titanium mill products.
Springback.....A metal product condition that describes the degree which metal tends to try to recover to its previous shape after going through a forming process.
ST.......Abbreviation for Solution Heat Treatment. A thermal processing procedure designed to effect the crystalline structure by causing one or more structural elements to enter into solid solution and thereafter hold (by quenching) these elements in solution. The process is designed to create more attractive properties in a metal product.
STA.........Abbreviation for Solution Heat Treated and Aged. A thermal processing procedure designed to effect the crystalline structure by causing one or more structural elements to enter into solid solution and thereafter hold (by quenching) these elements in solution. After quenching it is aged at the standard aging temperature. The process is designed to create more attractive properties in a metal product.
STOA.........Abbreviation for Solution Heat Treated and Over aged. A thermal processing procedure designed to effect the crystalline structure by causing one or more structural elements to enter into solid solution and thereafter hold (by quenching) these elements in solution. After quenching it is aged above the standard aging temperature. The process is designed to create more attractive properties in a metal product.
Stress.....A measurement that describes internal forces within a metal product that resist the change of shape and form that has taken place to a metal product during processing. The Stress component is expressed in force per unit (usually pounds per square inch, psi).
Stress Reliving.......A thermal processing procedure designed to reduce residual stress. The process includes an engineered thermal process containing time and temperature dynamics followed by a very slow cooling process to minimize the amount of acquiring new residual stresses.
Tensile Strength.....A measurement that describes the maximum force a metal product can bear prior to failure. The measurement is expressed in a ratio of maximum load to original cross-section area. this is also known as the "ultimate strength" measurement.
Tension......A type of force that produces elongation in a metal product.
Transverse Direction......... The transverse directions are dimensions of a metal product that run perpendicular to the working direction of a metal product. In flat-rolled products there are two transverse directions. The direction through the thickness is known as the "short transverse" and the direction across the width is know as the "long transverse". It is sometimes difficult to determine the long transverse direction in sheet and plate products. To eliminate uncertainties many specifications require stenciling to be administered in the longitudinal direction. When viewing a product's microstructure, it is the direction perpendicular to the elongated grain in worked metal products.
Ultimate Strength.....A measurement that describes the maximum force a metal product can bear prior to failure. The measurement is expressed in a ratio of maximum load to original cross-section area. this is also known as the "tensile strength" measurement.
Ultrasonic Testing.....A testing procedure used to determine the size and location of defects within a metal product. The process uses short bursts of acoustic energy (sound waves) in the ultrasonic range and reads back the reflections of these bursts to identify any defects.
Upset Forging........A semi finished metal product that has been produced by mechanical deformation into a new form with increased cross sectional size.
Vacuum Creep Flattening......A thermal processing procedure used to produce both flat and stress-free plate. The plate is placed in a bed and slowly subjected to vacuum forces and elevated thermal forces high enough to anneal the plate.
Vacuum Melting......A thermal processing procedure for remelting and refining titanium products in a vacuum chamber. Once the melting is completed the solidification process is usually carried out in the vacuum chamber. This process prevents oxygen and other gaseous contaminations in the remelted product.
Weldability......A measurement that describes the relative ability of an alloy to be welded to another like product. The measurement also describes a specific set of conditions and requirements the completed weldment must meet.
Wire......A metal product with a circular diameter that runs from .032 to .312" thick. The products are usually produced in long continuous lengths and can be ordered cut to length or in a coil.
X-Ray Radiographs..............A testing procedure designed to identify cracks, porosity or inclusions of titanium weldments.
Yield Strength.....A measurement that describes the force a metal product bears at a pre-defined % of deviation in dimensional proportions. The specified deviation for titanium is usually at 2(two) %.
Zirconium.....A master alloy element found in several titanium alloys used to strengthen both alpha and beta microstructures. Typical weight percentages are from 2 to 8%.
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