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A .Mor t ens en , C .SanMar ch i , H .P .Deg i s cher


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A.Mortensen, C.San Marchi, H.P.Degischer MMC-Assess Thematic Network

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Glossary of terms specific to Metal Matrix CompositesMMC ASSESS EU Network, Topic 1: Processing.

1) GENERAL DEFINITIONS:

Composite: A composite (or composite material) is defined as a material that consists of at leasttwo constituents (distinct phases or combinations of phases) which are bonded together alongthe interface in the composite, each of which originates from a separate ingredient materialwhich pre-exists the composite.The essential elements of this definition are(i) composite refers to a material, as opposed to a structure or a component; as such a

composite material is used for the fabrication of components of various shapes orfunctions, thus it should be distinguished from a wing or other structure made of severalcomponents bonded together, and from an electronic device or packaging structure madeof layered materials (although one of the materials in the packaging could be considered acomposite);

(ii) the composite is produced via a physical combination of at least two pre-existingingredient materials; this distinguishes a composite from other multiphase materials whichare produced by bulk processes where one or more phases result from phasetransformation: many in-situ composites, such as directionally solidified eutectics oralloys from which a ceramic phase is precipitated, are thus considered to be alloys and notcomposites (even though their properties can be described using composite theory).

Hybrid composite: a composite that consists of at least three (as opposed to two) constituents(distinct phases or combinations of phases) which are bonded together at the atomic level in thecomposite, each of which originates from a separate ingredient material which pre-exists thecomposite (i.e., there are, at least three ingredient materials).

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Metal Matrix Composite (MMC):a composite material in which one constituent is a metal or alloyforming at least one percolating network. The other constituent is embedded in this metal matrixand usually serves as reinforcement.

Metal matrix: the percolating metal or alloy forming the constituent of a MMC in which the

other constituents are embedded.

Ingredient materials: Raw materials put together to produce the composite (e.g., the metalalloy, metal powder, ceramic particles, etc.). During the processing the ingredient materials aretransformed into the constituents of the MMC.

Reinforcement: a constituent (phase or combination of phases) of the MMC originating from theingredient material which is combined with a metal or an alloy to produce a metal matrixcomposite (e.g., alumina fibres, silicon carbide whiskers, steel fibres, or graphite particles, even if,in the case of graphite particles, the reinforcement does not reinforce the matrix).A reinforcement is characterised by its chemical composition, its shape and dimensions, itsproperties as ingredient material and its volume fraction and spatial distribution in the matrix.

Interface: that portion of the composite microstructure that lies between its constituents, i.e.matrix and reinforcement. The interface may be a simple row of atomic bonds (e.g., theinterface between alumina and pure aluminium), but may also include matrix/reinforcementreaction products (e.g., aluminium carbide between aluminium and carbon fibres), orreinforcement coatings (e.g., interfacial coatings between SiC monofilaments and titaniummatrices).

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1) REINFORCEMENT

Continuous reinforcement: a constituent of a compositewhich is continuous in at least onedirection through the composite (e.g., continuous fibres or percolating open-celled foam).

Continuous fib res (f) : cylindrical ingredient material producedcontinuously to form anessentially endless reinforcement in the composite; usually delivered on bobbins ofmultifilament tows, each tow consisting of many individual fibres of diameters typically in therange of 3 to 30 m. According to the production process such fibres are usually coated by apolymeric sizing and the tows may be slightly twisted. They are typically designated by abrand name, the number of fibres per tow and a symbol of the applied sizing (e.g. T300-6K-E).

Monofilaments (m) : essentially endless reinforcement as continuous fibres, except for a largerdiameter, typically greater than 100 m. Monofilaments are generally produced by depositiononto a core fibre (most often of carbon or tungsten), and are delivered as individual fibresinstead of tows.

Discontinuous reinforcement: a non-percolating constituent of a composite, taking the form ofindividual elements embedded in the matrix constituent (e.g., particulates, short fibres,whiskers). Preforms produced from discontinuous reinforcements that are mechanicallystabilised by a binder or by cold compaction are still considered discontinuous reinforcements.

Particulates (p) : roughly equiaxed reinforcement or composite ingredient, usually of aspectratio (ratio of largest to smallest diameter) less than about 5. Particulates can be both mono- orpolycrystalline, can take various shapes (spherical, angular, plate-like) and are typically greaterthan 1 m in diameter.

Dispersoids (d) : same as particulates, except that the diameter is less than 1m, hence, being

capable of providing Orowan strengthening.

Platelets: flat reinforcements of an aspect ratio (diameter to thickness) greater than 2. Plateletsof an aspect ratio less than 5 can be considered as a type of particulates.

Short f ibres (s) : cylindrical reinforcement or composite ingredient with a ratio of length todiameter greater than 5 (but typically greater than 100), and with a diameter typically greaterthan 1 m.

Whiskers (w) : elongated single crystals, typically produced with a length to diameter ratiogreater than 10 and with a diameter typically less than 1micron.

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2) CATEGORIES OF MMC

Particulate reinforced MMC (PRM):metal matrix composite with a particulate reinforcementoccupying a volume fraction greater than 5% in the material (otherwise, the particulates are

generally considered to be inclusions).

Dispersoid reinforced MMC: metal matrix composite with a dispersoid reinforcementoccupying a volume fraction greater than 5% in the material (otherwise, the material isconsidered to be a dispersion strengthened metal - which incidentally may form the matrix ofany type of MMC, i.e., a MMC with dispersion-strengthened matrix).

Cermets: a metal matrix with a three-dimensionally percolating ceramic reinforcement,typically with far more ceramic than metal (strictly speaking they contain less than 20% metalper volume and are thus not considered as MMC). According to the percolating structure ofboth constituents cermets could thus be considered as both a ceramic and a metal matrixcomposite.

Short fibre reinforced MMC (SFRM): metal matrix composite with a short fibre reinforcement.

Whisker reinforced MMC (WRM): metal matrix composite with a whisker reinforcement.

Continuous fibre reinforced MMC (CFRM): metal matrix composite with reinforcement ofcontinuous fibres.

Monofilament reinforced MMC (MFRM): metal matrix composite with reinforcement ofmonofilaments.

MMC designation: method of indicating the composition and at t imes also the processing of

the MMC. As proposed by the American Aluminum Association for the designation ofaluminium composites, MMC should be designated as follows by their constituents: accepteddesignation of the matrix / abbreviation of the reinforcements designation / arrangement andvolume fraction in % with symbol of type (shape) of reinforcement, such as p for particle, sfor short fibres, w for whiskers, f for continuous fibres or m for monofilaments (The for m is assumed to describe unidirectional reinforcement unless otherwise specified).

Some examples are: matrix of a magnesium alloy AM10 reinforced by continuous carbon fibresof type T300, perpendicular oriented, amounting to a volume fraction of 65% is designated as:

AM10/C-T300/65 f-0/90 ;or matrix of the aluminium alloy AA6061 reinforced by particulates of alumina of 22 % byvolume is designated as:

AA6061/Al2O3/22 p.Additional information is supplied as needed for more specific reference to properties withfollowing basic form:

/ form / heat treatmentForm is simply an indicator of final forming step as extruded or pmc for permanent moldcasting, while the heat treatment is specified as its standard for the matrix alloy such as t6 orO. Thus a more complete designation of the second example above is: AA6061/Al2O3/22 p/ extruded / T6 .MMC product names used by companies vary, hence their use indicates the processing routeemployed by implicit reference to the producer.

Cellular metals (metal foams): similar to MMC as they are often formed by combining two

separate ingredients yielding a metal matrix and the second constituent being the gas in closedor open pores: however, there is no clear bond between the gas phase and the matrix.

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4) PROCESSING STEPS

Pre-processing: all steps which precede primary processing (e.g., surface treatment ofingredient materials, or preform fabrication for infiltration processing).

Preform: a shaped porous assembly of ingredient material elements (such as fibres,whiskers or particles). Typically, preforms are produced for subsequent infiltration withliquid metal, or foil-fibre-foil stacks prior to diffusion bonding. The mechanical stabilityof the shape may be provided by the adjunction of a binder, potentially but not alwaysfugitive, and amounting to only a few mass % of the preform.

Hybrid preform: a preform containing at least two types of ingredient material elementswhich form at least two distinct reinforcing constituents in the composite (e.g.particulate-fibre mixtures, hollow micro-spheres).

Primary processing of composites: production of composite material by combining ingredient

materials (e.g., powdered metal and loose ceramic particles, or molten metal and fibrepreforms), but not necessarily to final shape or final microstructure.

Continuous MMC primary process: a process for the production of MMC material that isessentially continuous (e.g., foil-fibre-foil diffusion bonding using a rolling mill, or continuousinfiltration).

Secondary processing: processing steps which follow primary processing, and aim to alter theshape or microstructure of the material (e.g., shape casting, forging, extrusion, heat-treatment,machining). Secondary processing may change the constituents (phases, shape) of thecomposite.

Consolidation of MMC: a secondary composite manufacturing process during whichcomposite elements are consolidated (e.g., the consolidation of composite elements consistingof the reinforcement coated with the matrix metal).

MMC insertion casting: a secondary process for production of partially reinforcedcomponents, in which a pre-fabricated MMC is placed within a mould, and incorporated into ametal or alloy by a casting process.

Partially reinforced metal component: semi-products or components which contain MMCmaterial metallurgically bonded to a conventional metal or alloy (e.g. by diffusion bonding,insertion casting, co-extrusion).

In-situ MMC: a MMC in which the ingredient reinforcement material changes its phase orshape during primary composite processing (e.g. TiB2 reacts to form TiC in some metals by

adding carbon). To be an MMC, the constituents must, however, retain its local identity,although they change in shape and/or composition (otherwise, it is an alloy).

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5) LIQUID METAL PROCESSING

Stir casting: a primary process of composite production whereby the reinforcement ingredientmaterialis incorporated into the molten metal by stirring.

Compocasting: a variant of stir-casting in which the metal is semi-solid, i.e. a rheocastingprocess incorporating the reinforcing ingredient material to form the composite. (The semi-solid state aids incorporation of the particles, in particular because the metal is more viscous.)

Semi-solid forming: a family of secondary forming processes which use semi-solid alloy ormetal matrix in the case of a MMC.

Thixocasting: a family of secondary casting or forming processes, which shape partiallyremelted thixotropic (semi-solid) metallic materials by deformation.

Infiltration : a primary process of composite production whereby the moltenmetal is made to

fill, spontaneously or using external mechanical work, pores within a preform of thereinforcement ingredient.

Spontaneous infiltration: an infiltration process in which the matrix penetratesspontaneously the preform without added force (e.g., copper into tungsten because ofdirect wetting, or by coating nickel onto the reinforcement for infiltration withaluminium, or by control of the atmosphere and the alloy composition as in the Lanxide-

Primex process).

Forced infil tration: an infiltration process which is not spontaneous, i.e., which requiresapplication of mechanical force onto matrix or reinforcement.

Pressure infi ltration: an infiltration process in which hydrostatic pressure is applied ontothe molten matrix surface to drive the liquid into the preform.

Vacuum infil tration: an infiltration process in which a hydrostatic pressure of one barapplied by the atmosphere onto the molten matrix drives it into an evacuated preform. Insome processes the vacuum can be self-generated, for example by reaction of magnesiumwith air or oxygen in the preform.

Gas pressure infiltration: a pressure infiltration process which uses pressurized gas toapply pressure on the metal surface driving the liquid into a preform.

Pressure assisted investment casting: an investment casting process where a preform is

integrated into the pattern and the assembly is cast while the mould and the melt areunder hydrostatic gas pressure.

Mechanical pressure infiltration: a pressure infiltration process which uses a movingsolid part to apply pressure on the melt surface driving the liquid into a preform.

Squeeze casting infiltration: a mechanical pressure infiltration process in which apreform is placed into a solid mould, and pressure infiltration is affected with a movingsolid piston providing laminar flow of the molten matrix into the mould. Variantsinclude direct squeeze casting, in which the piston surface represents a fraction of thefinal casting surface; and indirect squeeze casting, in which the piston acts on the ingateto the die.

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Pressure die inf iltration: an infiltration process which uses a pressure die castingapparatus, in which a preform is placed into a solid mould, and pressure infiltration iseffected with a moving solid piston causing turbulent flow of the melt upstream of thepreform.

Centrifugal infiltration: an infiltration process in which centrifugal force is used to drive themolten matrix into the preform.

Ultrasonic inf iltration: an infiltration process in which ultrasonic pressure waves are used todrive the molten matrix into the preform.

Lorentz force inf iltration, or electromagnetic inf iltration: an infiltration process in whichelectromagnetic forces push the molten matrix into the preform.

Spray casting: a primary process of composite production whereby the metal is sprayed onto asubstrate. For composites, the reinforcement is either already incorporated in the sprayed melt

(e.g., by stir-casting), is combined during spraying with the metal, by injection of thereinforcement ingredient material into the sprayed metal droplet stream, or is co-sprayed, i.e.,sprayed at the same time as the matrix onto the substrate.

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6) SOLID STATE PROCESSING

MMC diffusion bonding: a primary process for composite fabrication in the solid state, inwhich stacks of matrix metal and reinforcement ingredients (usually parallel fibre monolayers

and matrix foils, see also fibre winding) are encapsulated and bonded together after evacuationby mechanical pressure at elevated temperature to enhance diffusion.

Foil-fibre-foil method (also called foil-fibre method): a primary composite production processwherein layers of metal foil and ceramic monofilament fibres are alternatively stacked toproduce precursor materials for subsequent diffusion bonding, specifically hot pressing.

Wire winding: a method for production of precursor MFRM material produced by co-windingmetal wires and ceramic fibres for subsequent diffusion bonding, specifically hot pressing

Powder cloth method: variant of the foil-fibre-foil method for production of MFRM, in whichmatrix metal powders and a binder are mixed and formed into a cloth or foil before stacking.

Powder consolidation: a diffusion bonding (primary) process in which matrix in powder formis blended or otherwise placed next to the reinforcing ingredient material, and consolidatedwith or without pressure and elevated temperature.

MMC sintering: consolidation of ingredient materials at elevated temperatures withoutapplication of pressure.

MMC liquid phase sintering: consolidation of ingredient materials comprising the presence ofa liquid phase (at least temporarily) in the compact.

MMC hot pressing: consolidation of ingredient materials by diffusion bonding with

application of pressure by means of a piston (a hot press) at temperatures high enough to effectconcurrent sintering of the matrix, which for metal matrices is generally above the matrixrecrystallisation temperature.

MMC cold pressing: consolidation of ingredient materials with application of pressure bymeans of a piston, at temperatures too low to effect concurrent sintering of the matrix, whichfor metal matrices is generally below the matrix recrystallisation temperature.

MMC hot isostatic pressing (HIP): diffusion bonding of ingredient materials with applicationof hydrostatic pressure by means of a gas, at temperatures high enough to effect concurrentsintering of the matrix, which for metal matrices is generally above the matrix recrystallisationtemperature.

MMC cold isostatic pressing (CIP): cold pressing of ingredient materials with application ofhydrostatic pressure by means of a fluid (or gas), at temperatures too low to effect concurrentsintering of the matrix, which for metal matrices is generally below the matrix recrystallisationtemperature.

MMC powder rolling: consolidation of ingredient materials with application of pressure bymeans of a rolling mill. Cold rolling occurs below the recrystallisation temperature of themetal, hot rolling at higher temperatures.

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MMC powder extrusion: consolidation of ingredient materials with application of pressure bymeans of an extrusion press. Cold extrusion occurs below the recrystallisation temperature ofthe metal, hot extrusion at higher temperatures.

MMC powder forging: consolidation of ingredient materials with application of pressure bymeans of a forging press. Cold forging occurs below the recrystallisation temperature of themetal, hot forging at higher temperatures.

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7) COATING PROCESSES

Coating processes: primary processes which coat the matrix onto individual reinforcementelements of the ingredient material (e.g., vapour deposition, or electrolytic coating) creatingcomposite elements, which generally require subsequent consolidation.

Vapour deposition coating (in the context of composite production): primary processwherein the matrix is deposited from the vapour phase onto individual reinforcementelements of the ingredient.

Electrolytic coating (in the context of composite production): primary process whereinthe matrix is deposited from solution using electrochemical means onto individualreinforcement elements of the ingredient material.

Matrix coated fibre method: a family of primary coating process whereby continuous ormonofilament fibres are coated with metal matrix material by physical vapourdeposition, or by sputtering techniques or by chemical means prior to composite

consolidation.

Vapour infil tration: a primary process wherein the matrix is deposited from the vapour phaseinto the pores of a preform of reinforcement material.

Electrolytic inf iltration: a primary process wherein the matrix is deposited from solution usingelectrochemical means into the pores of a preform of reinforcement material.

Electrolytic co-deposition: a primary composite processing method which consists inelectrolytic deposition of the matrix metal from a solution containing the reinforcementingredient, so as to trap the reinforcement within the deposited metal layer.

Plasma spray method: variant of the foil-fibre-foil method where monolayers of monofilamentfibres or continuous fibre tows are plasma sprayed with the matrix metal and subsequentlystacked and diffusion bonded, specifically hot pressed.

Slurry tape casting: method where monofilament fibres are coated with a slurry of matrixmetal powder thus forming a tape that can be stacked and diffusion bonded, specifically hotpressed, to form MFRM.

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8) ROLE WITHIN THE PRODUCTION CHAIN

Supplier: industrial or research institution that markets and sells MMC or MMC ingredientmaterials, or products thereof.

Producer: industrial or research institution that produces MMC or MMC ingredient materials,or products thereof.

Ingredient material supplier or producer:supplier or producer of ingredient materials that areused to make a composite (includes fibre or ceramic particle producers, as well as preformproducers).

MMC supplier or producer: supplier or producer of metal matrix composite materials. MMCproducer performs at least primary processing of the material.

MMC component supplier or producer: supplier or producer of metal matrix compositematerial components produced to final shape and microstructure MMC component producer

performs at least a secondary processing step of the material).

MMC end-user: the producer of an end-product which incorporates metal matrix compositematerials (e.g., a bicycle manufacturer)

MMC consumer: the user of an end-product which incorporates metal matrix compositematerials (e.g., the cyclist with reference to a bicycle).

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Cellular metals ...................................... 4Centrifugal infiltration .......................... 7

Cermets................................................. 4

CFRM .see Continuous fibre reinforced MMCCIP........................................................ 8Coating processes ................................ 10

COATING PROCESSES ...................... 10

Compocasting........................................ 6Composite............................................. 1Consolidation of MMC.......................... 5Continuous fibre reinforced MMC......... 4

Continuous fibres (f) ............................. 3

Continuous MMC primary process ........ 5

Continuous reinforcement ..................... 3direct squeeze casting ............................ 6

Discontinuous reinforcement ................. 3Dispersoid reinforced MMC.................. 4

Dispersoids (d) ...................................... 3Electrolytic coating .............................. 10

Electrolytic co-deposition..................... 10

Electrolytic infiltration......................... 10electromagnetic infiltration...... see Lorentz

force infiltration

Foil-fibre-foil method ............................ 8

Forced infiltration.................................. 6Gas pressure infiltration ........................ 6GENERAL DEFINITIONS..................... 1

HIP ....................................................... 8Hybrid composite .................................. 1

Hybrid preform..................................... 5

indirect squeeze casting......................... 6Infiltration ............................................ 6Ingredient material supplier or producer

....................................................... 11

Ingredient materials .............................. 2In-situ MMC ......................................... 5Interface................................................ 2LIQUID METAL PROCESSING ............ 6

Lorentz force infiltration........................ 7

Matrix coated fibre method.................. 10Mechanical pressure infiltration ............ 6metal foams .........Siehe Cellular metals

Metal matrix.......................................... 2Metal Matrix Composite ........................ 2

MFRM ... see Monofilament reinforced MMCMMC cold isostatic pressing.................. 8

MMC cold pressing ............................... 8MMC component supplier or producer. 11

MMC consumer................................... 11

MMC designation.................................. 4MMC diffusion bonding........................ 8

MMC end-user .................................... 11MMC hot isostatic pressing....................8

MMC hot pressing................................. 8

MMC insertion casting .......................... 5MMC liquid phase sintering .................. 8

MMC powder extrusion ......................... 9

MMC powder forging............................ 9MMC powder rolling............................. 8

MMC sintering......................................8MMC supplier or producer ..................11

Monofilament reinforced MMC ............. 4

Monofilaments (m)................................ 3Partially reinforced metal component.....5

Particulate reinforced MMC...................4Particulates (p) .......................................3

Plasma spray method ........................... 10

Platelets................................................. 3Powder cloth method ............................. 8

Powder consolidation ............................ 8Preform................................................. 5Pre-processing .......................................5Pressure assisted investment casting ......6Pressure die infiltration ......................... 7

Pressure inf iltration............................... 6

Primary processing of composites ..........5PRM ........... see Particulate reinforced MMCPROCESSING STEPS ............................ 5

Producer.............................................. 11

Reinforcement.......................................2REINFORCEMENT ............................... 3

rheocasting ............................................6ROLE WITHIN THE PRODUCTION

CHAIN............................................ 11Secondary processing............................. 5

Semi-solid forming................................ 6SFRM ..........see Short fibre reinforced MMCShort fibre reinforced MMC...................4

Short fibres (s).......................................3

Slurry tape casting ............................... 10SOLID S TATE PROCESSING ...............8

Spontaneous infiltration ........................ 6

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Spray casting......................................... 7Squeeze casting infiltration ................... 6Stir casting ............................................ 6Supplier.............................................. 11

Thixocasting.......................................... 6TYPES OF MMC ................................... 4Vacuum infiltration............................... 6

Vapour deposition coating ...................10Vapour infiltration .............................. 10Whisker reinforced MMC ......................4Whiskers (w) .........................................3

Wire winding ........................................8WRM..............see Whisker reinforced MMC

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MMC-Assess Publications

Volume 1: Glossary of Terms specific to M etal Mat rix Composit es

Volume 2: Thermal Treatm ents of Age-hardenable Metal M atrix Compos ites

Volume 3: Metallographic Preparation of M etal M atrix Compo sites

Volume 4: X-R ay Comput ed Tomography on M etal Matrix Composit es

Volume 5: Qualit y control and nondestructiv e tests in metal m atrix composit es

Volum e 6: Machining guidelines of Al/SiC part iculate MM C

Volume 7: Thermophy sical Properties of M etal M atrix Compo sites

Volume 8: Guidelines for joining of m etal m atrix compo sit es

Volume 9: Bomding and interface format ion in M etal M atrix Compos ites

Copyright: MMC-Assess Consortium, August 2000Content: A.Mortensen, C.San Marchi, H.P.Degischer

Design: P.Prader

Contact: Insitut e of M aterials Science and Test ing Vienna Univ ersity of Technology

[email protected]

Homepage: http://mmc-assess.tuwien.ac.at/

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