CA2357323A1 - Hybrid metal matrix composites - Google Patents
Hybrid metal matrix composites Download PDFInfo
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- CA2357323A1 CA2357323A1 CA002357323A CA2357323A CA2357323A1 CA 2357323 A1 CA2357323 A1 CA 2357323A1 CA 002357323 A CA002357323 A CA 002357323A CA 2357323 A CA2357323 A CA 2357323A CA 2357323 A1 CA2357323 A1 CA 2357323A1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C47/00—Making alloys containing metallic or non-metallic fibres or filaments
- C22C47/02—Pretreatment of the fibres or filaments
- C22C47/06—Pretreatment of the fibres or filaments by forming the fibres or filaments into a preformed structure, e.g. using a temporary binder to form a mat-like element
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
- C22C49/02—Alloys containing metallic or non-metallic fibres or filaments characterised by the matrix material
- C22C49/04—Light metals
- C22C49/06—Aluminium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12486—Laterally noncoextensive components [e.g., embedded, etc.]
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249924—Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity
- Y10T428/249927—Fiber embedded in a metal matrix
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
- Braking Arrangements (AREA)
Abstract
A hybrid composite reinforced metal matrix in which the metal is aluminum, aluminum alloy, or a magnesium alloy containing a relatively high percentage of aluminum. In addition to the reinforcement, which is typically alumina, the metal matrix also includes a hardening agent which is at least one intermetallic compound of aluminum with at least one second metal chosen from iron, nickel, titanium, zirconium, cobalt and niobium. The metal matrix optionally also includes graphite as a wear resistant agent. The intermetallic compound(s) can be added as a powder to the metal matrix during formation of the composite, or can be created in the composite by adding the at least one second metal as a powder to the molten metal matrix during composite preparation. If the intermetallic compound is created in the composite, the composite when made initially can be readily machined and is self hardening through repeated heating cycles. The composite finds use in brake parts, such as brake rotors and brake drums as a replacement for the commonly used grey cast iron and exhibits adequate strength and compression properties up to a working temperature of at least about 450ÀC.
Description
HYBRID METAL MATRIX COMPOSITES
Background of the Invention This invention is concerned with a hybrid aluminum matrix composite material of particular use in the fabrication of lightweight brake components. In this context, the term "aluminum" embraces both aluminum and its alloys. It also includes certain magnesium alloys which contain relatively high percentages of aluminium. More particularly this invention is concerned with a hybrid aluminum matrix composite of particular use in the fabrication of brake parts, such as the rotating parts used in vehicle disc or drum brake systems.
The conventional disc brake, for example as used in the vehicle industry, consists of essentially three elements in combination: a rotor, at least two opposed brake pads usually supported by a metal backing, and a hydraulic cylinder system carried in a caliper. The drum brake also contains essentially the same three parts, and the brake pads are pressed outwardly to engage the inner face of the drum. For both types, the hydraulic system is constructed to urge the brake pads into frictional engagement with the rotor or brake drum when hydraulic pressure is applied. The rotor is either fabricated as a disc which is bolted to a hub structure, or fabricated integrally with the hub structure; a brake drum is generally fabricated as a unit which is attached to the hub structure. Frictional engagement of the brake pads to slow the vehicle generates significant amounts of heat, which has several consequences. One of these is that the brake pads become heated, thus exposing the brake pads, hydraulic fluid, and the sundry elastomeric materials used in the hydraulic system to elevated temperatures while the brake is in use. These difficulties have been largely solved; brake hydraulic systems I
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and pad materials resistant to temperatures in excess of 500°C
are available.
The rotor or drum has to dissipate the major proportion of the heat generated in braking, and at least the surfaces in frictional engagement with the pads can reach temperatures approaching 500°C. The rotor or drum also has to accommodate the braking forces and desirably should have sufficient wear resistance to have an extended working life. In addition, it has to be made from a material which can be machined accurately, particularly if the hub is formed integrally with the rotor. The commonest material currently used for disc brake rotors and brake drums is grey cast iron: it can be readily cast and machined, will withstand both the temperature and stress conditions which occur on braking, and provides an acceptable working life.
However the use of grey cast iron as the rotor or drum material does have three significant disadvantages. First, iron is a poor conductor of heat, with the result that even when ventilated rotors which have internal air passageways are used, or when a finned brake drum is used, the rotor or drum once heated cools slowly. This can result in so-called brake fade if the brakes are used repetitively. Second, an iron rotor or drum is a relatively heavy component, which complicates vehicle design as it increases the vehicle unsprung weight for each wheel; this is of importance in fuel consumption, ride comfort, and green house gas emission, in competition vehicles and in aircraft.
Third, the cast iron used has a high coefficient of thermal expansion and a low elastic modulus. This results in a requirement for frequent machining to maintain the inner and outer rotor braking surfaces both flat and parallel, or to maintain the inner surface of a drum concentric with the hub.
Z
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,.wM...., , , ..... .u.."~w,w .,~,~.",~,~,.....~.~.~...,.~....~...._....~_ In order to overcome these disadvantages, it has been proposed to fabricate brake rotors from light metals, including aluminium, and aluminum alloys. Although light metals have acceptable strength properties, and far higher thermal conductivity than iron, the light metals cannot be used alone.
First, the light metals have inadequate resistance to frictional abrasion, and thus cannot provide an adequate working life. To overcome this disadvantage, light metal composite materials have been proposed, which comprise a light metal matrix reinforced with a second material dispersed in the metal matrix.
Typical reinforcing materials include silicon carbide, boron carbide, boron nitride, titanium diboride, titanium carbide and alumina. The elastic moduli of light metal matrix composites (such as an aluminum matrix reinforced with silicon carbide) are higher than the elastic modulus of cast iron and of unreinforced aluminum. In addition, the coefficients of thermal expansion of light metal matrix composites are lower than both cast iron and unreinforced aluminum. These composite materials do have adequate wear resistant properties.
Second, even though light metal composites have far better thermal conductivity, adequate strength and wear resistant properties are only obtained if the brake rotor surface in service does not exceed a temperature of above about 400°C. If the rotor surface temperature exceeds this value, and for example rises to above about 500°C, the rotor will fail rapidly due to softening of the light metal matrix. Even commercially available aluminum composites reinforced with silicon carbide (such as Duralcan (trade mark) composites) have a compressive strength as low as about 50 mPa at about 450°C. This is no better than unreinforced aluminum alloys at that temperature. As a result, commercial light metal composite brake rotors are suitable for use only for relatively light vehicles under about 1,100kg in weight.
This invention seeks to overcome these disadvantages, and to provide a hybrid aluminum composite material which retains adequate strength and wear properties up to at least 450°C, and preferably up to at least about 500°C. In the hybrid aluminum composite material of this invention one further material, and preferably at least two further materials, with different properties are incorporated in an effective amount into the metal matrix in addition to a reinforcing material.
Thus in a first embodiment, this invention seeks to provide a hybrid aluminum, or aluminum alloy, metal composite comprising in combination a metal matrix having dispersed therein effective amounts of each of:
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, boron nitride, titanium diboride, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the at least one second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium.
Preferably the metal composite also contains an effective amount of:
(c) a particulate wear resistant additive chosen from the group consisting of flake graphite, fibrous graphite and powdered graphite. More preferably, the metal composite contains up to about 2o by volume of the particulate wear resistant additive.
Preferably, the aluminum is an aluminum alloy, or a magnesium alloy containing a sufficiently high percentage of aluminum.
Preferably, the intermetallic compound is a binary intermetallic compound, and the second metal is nickel or iron.
Preferably, the intermetallic compound has a particle size range of from about lam to about 100~m.
Preferably, the metal matrix contains from about to to about 40o binary intermetallic compound by volume. Most preferably, the light metal matrix contains about 2% to about 40g by volume nickel or iron binary metallic compound.
Preferably, the reinforcement material is alumina.
Preferably, the reinforcement material is particulate, and has a particle size range of from about lam to about 50~m.
Preferably, the composite contains from about 5o to about 45o by volume reinforcement. More preferably, the composite contains from about 15o to about 35o by volume reinforcement.
Most preferably, the composite contains about 30o by volume reinforcement.
In a second broad embodiment this invention seeks to provide a process for the preparation of a metal composite comprising in combination an aluminum, or aluminum alloy, metal matrix having dispersed therein effective amounts of each of:
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, boron nitride, titanium diboride, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium;
which process comprises:
(i) fabricating a preform comprising the reinforcement;
(ii) placing the preform into a suitably shaped mould;
(iii) mixing an appropriate quantity of the at least one second metal in particulate or fiber form into a suitable amount of molten metal;
(iv) investing the preform in the mould with the molten metal; and (v) retrieving the reinforced metal composite casting from the mould.
If desired, the process includes the further steps of:
(vi) finish machining the casting to desired dimensions; and (vii) thermally cycling the finished casting to a temperature of at least from about 300°C to about 500°C until a desired initial high temperature strength is obtained.
Preferably, the preform is invested with molten light metal by the squeeze casting technique.
Preferably, the preform used in step (ii) is constructed and arranged to reinforce only a part of the metal composite, and is placed in the mould at the part to be reinforced.
Preferably, in step (iii) an effective amount of a particulate wear resistant additive chosen from the group consisting of flake graphite, fibrous graphite and powdered graphite is also mixed into the molten light metal.
Preferably, the second metal powder has a particle size range of from about 20E.cm to about 100~.cm.
The additional materials added to the metal matrix in the hybrid composites of this invention each serve different purposes.
The at least one intermetallic compound functions as a hardening agent for the metal matrix. Typical binary intermetallic compounds are: for nickel, NiAl, NizAl3 and Ni3Al;
for iron, FeAl and Fe3Al; for titanium, TiAl, Ti3Al, TiAl2 and TiAl3; for cobalt, CoAl; for zirconium, Zr3Al; and for niobium, Nb3Al. Depending on the elements present in the melt, particularly for an aluminium alloy, ternary intermetallic compounds can also be formed. Thus any element which will form an aluminide which has better mechanical strength, both at room temperature and at an elevated temperature, preferably of at least about 400°C can be used as the at least one second metal.
The element will form an aluminide under two conditions: in an aluminium melt at a temperature of at least about 700°C, and it has a high enough activation energy that solid state diffusion will occur to form aluminide when the composite is subjected to a temperature in the range of from about 300°C to about 500°C.
The metals cited above meet these criteria.
Additionally, although this invention is primarily concerned with the use of aluminium, or aluminium alloys, as the matrix metal, certain magnesium alloys also contain relatively high percentages of aluminium. These alloys can also be hardened by the incorporation into them of the same intermetallic compounds using the teachings of this invention.
When the metal composite is made according to the process of this invention, these intermetallic compounds are formed to some extent initially when the reinforcement and the other particulate materials are invested with molten light metal, for example in fabricating a hybrid metal composite body using the known squeeze casting process, by reaction of the at least one second metal with the molten aluminum or aluminum alloy.
However, formation of the intermetallic compounds also occurs by a solid state diffusion process which is thermally activated. It has been found that formation of the intermetallic compounds proceeds further, each time the hybrid light metal composite body is put through a heating cycle to a sufficiently high temperature, for example under repeated braking. Since the intermetallic compounds have the effect of hardening the light metal matrix, a body fabricated from the hybrid metal composite of this invention is both self hardening, and also continues to harden further during use when that use involves periodic heating of the body. It is thus apparent that the hybrid metal composite materials of this invention are particularly useful for brake components, especially disc brake rotors and brake drums, as these are subjected to heat cycling every time the vehicle brakes are used; strengthening of a rotor, for example, is thus an on-going process.
In the process aspect of this invention, the at least one second metal is added as a powder, and the casting and use conditions are then relied upon to both initiate and continue the solid state reaction to form the intermetallic compound. It is also possible to add the at least one intermetallic compound directly to the aluminum metal matrix during the mixing step in the casting process. This is not recommended, as it has two disadvantages. First, the intermetallic compounds in powder form are significantly more expensive than the corresponding powdered second metals. Second, since wetting of the intermetallic compound powder by the molten metal matrix may not be fully achieved during the fabrication process, it is possible that the interfacial strength between the intermetallic compound powder and the metal matrix may not be sufficient to add the desired level of strength to the metal composite. When the second metal is added as a powder, a metallurgical bond is formed when the second metal powder reacts with the metal matrix to provide the intermetallic compounds) in the metal matrix. Third, the resulting reinforced metal matrix composite as cast will be effectively fully hardened, with the result that it is very difficult to finish machine to its final shape.
The objective of adding the at least one second metal as a powder is that during the squeeze casting process, for example to cast a brake rotor, the added metal powder only reacts partially with the molten aluminium to form the intermetallic compound, or compounds. Thus, the as-cast brake rotor containing only a limited amount of intermetallic compound, or compounds, can be readily machined to the required final dimensions. During service, the brake rotor under braking will be repeatedly heated.
The repeated heat cycling of the rotor, especially under heavy and/or repeated braking which can involve brake rotor temperatures of in excess of 400°C, activates the reaction of the remaining at least one second metal with the aluminium matrix.
As the amount of intermetallic compound, or compounds, present increases, so also does the high temperature strength of the brake rotor. If desired, in order to ensure adequate initial high temperature strength, a finished component can be thermally cycled up to a temperature of from at least about 300°C to about 500°C prior to use.
Further, in the process aspect of this invention, the reinforcement is typically provided as a preform, particularly if it is desired to reinforce only a selected portion, or portions, of the final composite body. The preform is prepared by a conventional technique suitable for the reinforcement material, or mixture of materials, which is chosen.
The graphite powder functions to improve the frictional wear resistance characteristics of the hybrid light alloy composite material. It also functions to improve the machining properties of the cast metal composite.
Since the total. amount of the three additives incorporated into the aluminum, or aluminum alloy, metal matrix composite bodies according to this invention can be quite low, the composite largely retains the ductility and machinability of the metal. The properties of the metal can therefore generally be used as the basic design parameters for the hybrid composite body.
The metal used in this invention can be either aluminum, or an aluminum alloy. Many such alloys are commercially available, recommended for use for both cast and wrought products; those for wrought products generally have better mechanical properties.
Typical alloying elements include iron, copper, manganese, magnesium, chromium, nickel, zinc, gallium, vanadium, titanium, zirconium, lithium, tin, boron, cobalt, beryllium, bismuth and lead. Additionally, in certain magnesium alloys although the major metal is magnesium, the percentage of aluminium is high enough for aluminium intermetallic compounds to be formed. The properties of these magnesium alloys can be altered using the teachings of this invention.
Background of the Invention This invention is concerned with a hybrid aluminum matrix composite material of particular use in the fabrication of lightweight brake components. In this context, the term "aluminum" embraces both aluminum and its alloys. It also includes certain magnesium alloys which contain relatively high percentages of aluminium. More particularly this invention is concerned with a hybrid aluminum matrix composite of particular use in the fabrication of brake parts, such as the rotating parts used in vehicle disc or drum brake systems.
The conventional disc brake, for example as used in the vehicle industry, consists of essentially three elements in combination: a rotor, at least two opposed brake pads usually supported by a metal backing, and a hydraulic cylinder system carried in a caliper. The drum brake also contains essentially the same three parts, and the brake pads are pressed outwardly to engage the inner face of the drum. For both types, the hydraulic system is constructed to urge the brake pads into frictional engagement with the rotor or brake drum when hydraulic pressure is applied. The rotor is either fabricated as a disc which is bolted to a hub structure, or fabricated integrally with the hub structure; a brake drum is generally fabricated as a unit which is attached to the hub structure. Frictional engagement of the brake pads to slow the vehicle generates significant amounts of heat, which has several consequences. One of these is that the brake pads become heated, thus exposing the brake pads, hydraulic fluid, and the sundry elastomeric materials used in the hydraulic system to elevated temperatures while the brake is in use. These difficulties have been largely solved; brake hydraulic systems I
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and pad materials resistant to temperatures in excess of 500°C
are available.
The rotor or drum has to dissipate the major proportion of the heat generated in braking, and at least the surfaces in frictional engagement with the pads can reach temperatures approaching 500°C. The rotor or drum also has to accommodate the braking forces and desirably should have sufficient wear resistance to have an extended working life. In addition, it has to be made from a material which can be machined accurately, particularly if the hub is formed integrally with the rotor. The commonest material currently used for disc brake rotors and brake drums is grey cast iron: it can be readily cast and machined, will withstand both the temperature and stress conditions which occur on braking, and provides an acceptable working life.
However the use of grey cast iron as the rotor or drum material does have three significant disadvantages. First, iron is a poor conductor of heat, with the result that even when ventilated rotors which have internal air passageways are used, or when a finned brake drum is used, the rotor or drum once heated cools slowly. This can result in so-called brake fade if the brakes are used repetitively. Second, an iron rotor or drum is a relatively heavy component, which complicates vehicle design as it increases the vehicle unsprung weight for each wheel; this is of importance in fuel consumption, ride comfort, and green house gas emission, in competition vehicles and in aircraft.
Third, the cast iron used has a high coefficient of thermal expansion and a low elastic modulus. This results in a requirement for frequent machining to maintain the inner and outer rotor braking surfaces both flat and parallel, or to maintain the inner surface of a drum concentric with the hub.
Z
r~,..~.,~.,~~...W~....._~~ . ..~.,.,.,~,~..,~m»..~ ~Mrv.. ," ".~~~, T. ~~.
,.wM...., , , ..... .u.."~w,w .,~,~.",~,~,.....~.~.~...,.~....~...._....~_ In order to overcome these disadvantages, it has been proposed to fabricate brake rotors from light metals, including aluminium, and aluminum alloys. Although light metals have acceptable strength properties, and far higher thermal conductivity than iron, the light metals cannot be used alone.
First, the light metals have inadequate resistance to frictional abrasion, and thus cannot provide an adequate working life. To overcome this disadvantage, light metal composite materials have been proposed, which comprise a light metal matrix reinforced with a second material dispersed in the metal matrix.
Typical reinforcing materials include silicon carbide, boron carbide, boron nitride, titanium diboride, titanium carbide and alumina. The elastic moduli of light metal matrix composites (such as an aluminum matrix reinforced with silicon carbide) are higher than the elastic modulus of cast iron and of unreinforced aluminum. In addition, the coefficients of thermal expansion of light metal matrix composites are lower than both cast iron and unreinforced aluminum. These composite materials do have adequate wear resistant properties.
Second, even though light metal composites have far better thermal conductivity, adequate strength and wear resistant properties are only obtained if the brake rotor surface in service does not exceed a temperature of above about 400°C. If the rotor surface temperature exceeds this value, and for example rises to above about 500°C, the rotor will fail rapidly due to softening of the light metal matrix. Even commercially available aluminum composites reinforced with silicon carbide (such as Duralcan (trade mark) composites) have a compressive strength as low as about 50 mPa at about 450°C. This is no better than unreinforced aluminum alloys at that temperature. As a result, commercial light metal composite brake rotors are suitable for use only for relatively light vehicles under about 1,100kg in weight.
This invention seeks to overcome these disadvantages, and to provide a hybrid aluminum composite material which retains adequate strength and wear properties up to at least 450°C, and preferably up to at least about 500°C. In the hybrid aluminum composite material of this invention one further material, and preferably at least two further materials, with different properties are incorporated in an effective amount into the metal matrix in addition to a reinforcing material.
Thus in a first embodiment, this invention seeks to provide a hybrid aluminum, or aluminum alloy, metal composite comprising in combination a metal matrix having dispersed therein effective amounts of each of:
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, boron nitride, titanium diboride, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the at least one second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium.
Preferably the metal composite also contains an effective amount of:
(c) a particulate wear resistant additive chosen from the group consisting of flake graphite, fibrous graphite and powdered graphite. More preferably, the metal composite contains up to about 2o by volume of the particulate wear resistant additive.
Preferably, the aluminum is an aluminum alloy, or a magnesium alloy containing a sufficiently high percentage of aluminum.
Preferably, the intermetallic compound is a binary intermetallic compound, and the second metal is nickel or iron.
Preferably, the intermetallic compound has a particle size range of from about lam to about 100~m.
Preferably, the metal matrix contains from about to to about 40o binary intermetallic compound by volume. Most preferably, the light metal matrix contains about 2% to about 40g by volume nickel or iron binary metallic compound.
Preferably, the reinforcement material is alumina.
Preferably, the reinforcement material is particulate, and has a particle size range of from about lam to about 50~m.
Preferably, the composite contains from about 5o to about 45o by volume reinforcement. More preferably, the composite contains from about 15o to about 35o by volume reinforcement.
Most preferably, the composite contains about 30o by volume reinforcement.
In a second broad embodiment this invention seeks to provide a process for the preparation of a metal composite comprising in combination an aluminum, or aluminum alloy, metal matrix having dispersed therein effective amounts of each of:
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, boron nitride, titanium diboride, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium;
which process comprises:
(i) fabricating a preform comprising the reinforcement;
(ii) placing the preform into a suitably shaped mould;
(iii) mixing an appropriate quantity of the at least one second metal in particulate or fiber form into a suitable amount of molten metal;
(iv) investing the preform in the mould with the molten metal; and (v) retrieving the reinforced metal composite casting from the mould.
If desired, the process includes the further steps of:
(vi) finish machining the casting to desired dimensions; and (vii) thermally cycling the finished casting to a temperature of at least from about 300°C to about 500°C until a desired initial high temperature strength is obtained.
Preferably, the preform is invested with molten light metal by the squeeze casting technique.
Preferably, the preform used in step (ii) is constructed and arranged to reinforce only a part of the metal composite, and is placed in the mould at the part to be reinforced.
Preferably, in step (iii) an effective amount of a particulate wear resistant additive chosen from the group consisting of flake graphite, fibrous graphite and powdered graphite is also mixed into the molten light metal.
Preferably, the second metal powder has a particle size range of from about 20E.cm to about 100~.cm.
The additional materials added to the metal matrix in the hybrid composites of this invention each serve different purposes.
The at least one intermetallic compound functions as a hardening agent for the metal matrix. Typical binary intermetallic compounds are: for nickel, NiAl, NizAl3 and Ni3Al;
for iron, FeAl and Fe3Al; for titanium, TiAl, Ti3Al, TiAl2 and TiAl3; for cobalt, CoAl; for zirconium, Zr3Al; and for niobium, Nb3Al. Depending on the elements present in the melt, particularly for an aluminium alloy, ternary intermetallic compounds can also be formed. Thus any element which will form an aluminide which has better mechanical strength, both at room temperature and at an elevated temperature, preferably of at least about 400°C can be used as the at least one second metal.
The element will form an aluminide under two conditions: in an aluminium melt at a temperature of at least about 700°C, and it has a high enough activation energy that solid state diffusion will occur to form aluminide when the composite is subjected to a temperature in the range of from about 300°C to about 500°C.
The metals cited above meet these criteria.
Additionally, although this invention is primarily concerned with the use of aluminium, or aluminium alloys, as the matrix metal, certain magnesium alloys also contain relatively high percentages of aluminium. These alloys can also be hardened by the incorporation into them of the same intermetallic compounds using the teachings of this invention.
When the metal composite is made according to the process of this invention, these intermetallic compounds are formed to some extent initially when the reinforcement and the other particulate materials are invested with molten light metal, for example in fabricating a hybrid metal composite body using the known squeeze casting process, by reaction of the at least one second metal with the molten aluminum or aluminum alloy.
However, formation of the intermetallic compounds also occurs by a solid state diffusion process which is thermally activated. It has been found that formation of the intermetallic compounds proceeds further, each time the hybrid light metal composite body is put through a heating cycle to a sufficiently high temperature, for example under repeated braking. Since the intermetallic compounds have the effect of hardening the light metal matrix, a body fabricated from the hybrid metal composite of this invention is both self hardening, and also continues to harden further during use when that use involves periodic heating of the body. It is thus apparent that the hybrid metal composite materials of this invention are particularly useful for brake components, especially disc brake rotors and brake drums, as these are subjected to heat cycling every time the vehicle brakes are used; strengthening of a rotor, for example, is thus an on-going process.
In the process aspect of this invention, the at least one second metal is added as a powder, and the casting and use conditions are then relied upon to both initiate and continue the solid state reaction to form the intermetallic compound. It is also possible to add the at least one intermetallic compound directly to the aluminum metal matrix during the mixing step in the casting process. This is not recommended, as it has two disadvantages. First, the intermetallic compounds in powder form are significantly more expensive than the corresponding powdered second metals. Second, since wetting of the intermetallic compound powder by the molten metal matrix may not be fully achieved during the fabrication process, it is possible that the interfacial strength between the intermetallic compound powder and the metal matrix may not be sufficient to add the desired level of strength to the metal composite. When the second metal is added as a powder, a metallurgical bond is formed when the second metal powder reacts with the metal matrix to provide the intermetallic compounds) in the metal matrix. Third, the resulting reinforced metal matrix composite as cast will be effectively fully hardened, with the result that it is very difficult to finish machine to its final shape.
The objective of adding the at least one second metal as a powder is that during the squeeze casting process, for example to cast a brake rotor, the added metal powder only reacts partially with the molten aluminium to form the intermetallic compound, or compounds. Thus, the as-cast brake rotor containing only a limited amount of intermetallic compound, or compounds, can be readily machined to the required final dimensions. During service, the brake rotor under braking will be repeatedly heated.
The repeated heat cycling of the rotor, especially under heavy and/or repeated braking which can involve brake rotor temperatures of in excess of 400°C, activates the reaction of the remaining at least one second metal with the aluminium matrix.
As the amount of intermetallic compound, or compounds, present increases, so also does the high temperature strength of the brake rotor. If desired, in order to ensure adequate initial high temperature strength, a finished component can be thermally cycled up to a temperature of from at least about 300°C to about 500°C prior to use.
Further, in the process aspect of this invention, the reinforcement is typically provided as a preform, particularly if it is desired to reinforce only a selected portion, or portions, of the final composite body. The preform is prepared by a conventional technique suitable for the reinforcement material, or mixture of materials, which is chosen.
The graphite powder functions to improve the frictional wear resistance characteristics of the hybrid light alloy composite material. It also functions to improve the machining properties of the cast metal composite.
Since the total. amount of the three additives incorporated into the aluminum, or aluminum alloy, metal matrix composite bodies according to this invention can be quite low, the composite largely retains the ductility and machinability of the metal. The properties of the metal can therefore generally be used as the basic design parameters for the hybrid composite body.
The metal used in this invention can be either aluminum, or an aluminum alloy. Many such alloys are commercially available, recommended for use for both cast and wrought products; those for wrought products generally have better mechanical properties.
Typical alloying elements include iron, copper, manganese, magnesium, chromium, nickel, zinc, gallium, vanadium, titanium, zirconium, lithium, tin, boron, cobalt, beryllium, bismuth and lead. Additionally, in certain magnesium alloys although the major metal is magnesium, the percentage of aluminium is high enough for aluminium intermetallic compounds to be formed. The properties of these magnesium alloys can be altered using the teachings of this invention.
Claims (19)
1. A hybrid aluminum, or aluminum alloy, metal composite comprising in combination a metal matrix having dispersed therein effective amounts of each of:
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, boron nitride, titanium diboride, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the at least one second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium.
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, boron nitride, titanium diboride, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the at least one second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium.
2. A hybrid metal composite according to Claim 1 further containing an effective amount of:
(c) a particulate wear additive chosen from the group consisting of flake graphite, fibrous graphite and powdered graphite.
(c) a particulate wear additive chosen from the group consisting of flake graphite, fibrous graphite and powdered graphite.
3. A hybrid metal composite according to Claim 1 wherein the metal matrix is chosen from the group consisting of an aluminum alloy, and a magnesium alloy containing a sufficiently high percentage of aluminium.
4. A hybrid metal composite according to Claim 1 wherein the at lest one second metal is chosen from at least one member of the group consisting of nickel, iron and titanium.
5. A hybrid metal composite according to Claim 1 wherein the at least one intermetallic compound has a particle size range of from about 1µm to about 100µm.
6. A hybrid metal composite according to Claim 1 wherein the metal matrix contains from about 1% to about 40% intermetallic compound by volume.
7. A hybrid metal composite according to Claim 6 wherein the light metal matrix contains about 2% by volume binary metallic compound in which the second metal is chosen from the group consisting of nickel and iron.
8. A hybrid metal composite according to Claim 1 wherein the particulate reinforcement material is alumina.
9. A hybrid metal composite according to Claim 1 wherein the reinforcement material is particulate, and has a particle size range of from about 1µm to about 50µm.
10. A hybrid metal composite according to Claim 1 wherein the composite contains from about 15% to about 45% by volume reinforcement.
11. A hybrid metal composite according to Claim 10 wherein the composite contains from about 15% to about 35% by volume reinforcement.
12. A hybrid metal composite according to Claim 11 wherein the composite contains about 30% by volume reinforcement.
13. A hybrid metal composite according to Claim 1 wherein the metal composite contains up to about 2% by volume of the particulate wear additive.
14. A process for the preparation of a metal composite comprising in combination an aluminum, or aluminum alloy, metal matrix having dispersed therein effective amounts of each of:
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, silicon carbide, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium;
which process comprises:
(i) fabricating a preform comprising the reinforcement (ii) placing the preform into a suitably shaped mould;
(iii) mixing an appropriate quantity of the second metal in particulate or fiber form into a suitable amount of molten metal;
(iv) investing the preform in the mould with the molten metal; and (v) retrieving the reinforced metal composite casting from the mould.
(a) a particulate, whisker or fibre reinforcement material chosen from the group consisting of alumina, silicon carbide, silicon dioxide, boron carbide, silicon carbide, and titanium carbide; and (b) at least one intermetallic metal compound of aluminum with at least one second metal, in which the second metal is chosen from at least one member of the group consisting of nickel, iron, titanium, cobalt, niobium and zirconium;
which process comprises:
(i) fabricating a preform comprising the reinforcement (ii) placing the preform into a suitably shaped mould;
(iii) mixing an appropriate quantity of the second metal in particulate or fiber form into a suitable amount of molten metal;
(iv) investing the preform in the mould with the molten metal; and (v) retrieving the reinforced metal composite casting from the mould.
15. A process according to Claim 14 wherein the preform is invested with molten light metal by the squeeze casting technique.
16. A process according to Claim 14 wherein in step (iii) an effective amount of a particulate wear additive chosen from the group consisting of flake graphite, fibrous graphite and powdered graphite is also mixed into the molten light metal.
17. A process according to Claim 14 wherein the second metal powder has a particle size range of from about 20µm to about 50µm.
18. A process according to Claim 14 including the further steps of:
(vi) finish machining the casting to desired dimensions; and (vii) thermally cycling the finished casting to a temperature of from at least about 300ÀC to about 500ÀC until a desired initial high temperature strength is obtained.
(vi) finish machining the casting to desired dimensions; and (vii) thermally cycling the finished casting to a temperature of from at least about 300ÀC to about 500ÀC until a desired initial high temperature strength is obtained.
19. A process according to Claim 14 wherein the preform used in step (ii) is constructed and arranged to reinforce only a part of the metal composite, and is placed in the mould at the part to be reinforced.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US66017700A | 2000-09-12 | 2000-09-12 | |
| US09/660,177 | 2000-09-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2357323A1 true CA2357323A1 (en) | 2002-03-12 |
Family
ID=24648470
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002357323A Abandoned CA2357323A1 (en) | 2000-09-12 | 2001-09-12 | Hybrid metal matrix composites |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US20030175543A1 (en) |
| JP (1) | JP2002178130A (en) |
| CA (1) | CA2357323A1 (en) |
Cited By (4)
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| US7550029B2 (en) | 2004-04-22 | 2009-06-23 | Alcan International Limited | Recycling method for Al—B4C composite materials |
| CN110732654A (en) * | 2019-09-12 | 2020-01-31 | 天津立鑫晟智能制造有限公司 | Liquid die forging process for high-chromium cast iron plate hammers |
| US10815552B2 (en) | 2013-06-19 | 2020-10-27 | Rio Tinto Alcan International Limited | Aluminum alloy composition with improved elevated temperature mechanical properties |
| CN115805666A (en) * | 2022-12-16 | 2023-03-17 | 汨罗市福缘新材料有限公司 | Fettling milling cutter suitable for graphite product |
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| JP4323339B2 (en) * | 2004-02-03 | 2009-09-02 | 日信工業株式会社 | Brake drum and manufacturing method thereof |
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| CA2757805C (en) * | 2010-11-10 | 2015-02-10 | Purdue Research Foundation | Method of producing particulate-reinforced composites and composites produced thereby |
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| US5041340A (en) * | 1987-09-03 | 1991-08-20 | Honda Giken Kogyo Kabushiki Kaisha | Fiber-reinforced light alloy member excellent in heat conductivity and sliding properties |
| JPH01205041A (en) * | 1988-02-09 | 1989-08-17 | Honda Motor Co Ltd | Fiber reinforced aluminum alloy composite material |
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- 2001-09-12 CA CA002357323A patent/CA2357323A1/en not_active Abandoned
-
2003
- 2003-02-28 US US10/375,257 patent/US20030175543A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7550029B2 (en) | 2004-04-22 | 2009-06-23 | Alcan International Limited | Recycling method for Al—B4C composite materials |
| US10815552B2 (en) | 2013-06-19 | 2020-10-27 | Rio Tinto Alcan International Limited | Aluminum alloy composition with improved elevated temperature mechanical properties |
| CN110732654A (en) * | 2019-09-12 | 2020-01-31 | 天津立鑫晟智能制造有限公司 | Liquid die forging process for high-chromium cast iron plate hammers |
| CN115805666A (en) * | 2022-12-16 | 2023-03-17 | 汨罗市福缘新材料有限公司 | Fettling milling cutter suitable for graphite product |
Also Published As
| Publication number | Publication date |
|---|---|
| US20030175543A1 (en) | 2003-09-18 |
| JP2002178130A (en) | 2002-06-25 |
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