EP2178664A1

EP2178664A1 - Aluminium-based duplex-aluminium material with a first phase and a second phase and method for producing said duplex-aluminium material

Info

Publication number: EP2178664A1
Application number: EP08784863A
Authority: EP
Inventors: Horst Adams; Michael Dvorak
Original assignee: Alcan Technology and Management Ltd
Current assignee: 3A Composites International AG
Priority date: 2007-07-18
Filing date: 2008-07-18
Publication date: 2010-04-28
Also published as: CA2692959A1; WO2009010297A1; US20100189995A1; JP2010533786A; BRPI0813517A2; CN101754826A

Abstract

The invention relates to the processing of a composite material in particle or powder form, containing carbon nanotubes (CNT), said material having metal with a thickness of between 10 nm and 500,000 nm that is layered alternately with carbon nanotubes of a thickness of between 10 nm and 100,000 nm. The material is produced by mechanical alloying, i.e. by repeated deformation, breakage and welding of metal particles and CNT particles, preferably by milling in a pebble mill containing a milling chamber and milling pebbles as the milling bodies and to a rotating body for creating highly energetic pebble collisions. The invention discloses a method for producing duplex-aluminium, in which a material is alloyed as a combination of the composite material and an aluminium alloy with different characteristics in an Ospray process.

Description

Duplex aluminum material based on aluminum with a first phase and a second phase and method for producing the duplex aluminum material

The invention relates to a duplex aluminum material based on aluminum having a first phase and a second phase, which is produced in a Sprühkompaktierverfahren, with at least introduced via a first beam first material component in the form of an aluminum-based alloy to form the first phase and at least one introduced via a second beam second material component to form the second phase. Furthermore, the invention relates to a method for producing the duplex aluminum material.

There are known carbon nanotubes. Further equivalent terms for carbon nanotubes are nanoscale carbon tubes or carbon nanotubes and the abbreviated designation "CNT." In the following, the most commonly used form in the art, namely "CNT", will continue to be used. The CNTs are fullerenes and are carbon modifications with closed polyhedral structure. Known fields of application for CNTs are found in the field of semiconductors or for improving the mechanical properties of conventional plastics (www.de.wikipedia.org under "carbon nanotube").

In addition, Al / CNT composites are known from ESAWI A ET AL: "Dispersion of carbon nanotubes (CNTs) in aluminum powders" COMPOS PART A APPL SCI MANUF; COMPOSITES PART A: APPLIED SCIENCE AND MANUFACTURING FEBRUARY 2007, [Online] Vol. 38, No. 2, June 23, 2006 (2006-06-23), pages 646-650 and EDTMAIER C ET AL: "Aluminum-based carbon nanotube composites by mechanical alloying" POWDER METALLURGY WORLD CONGRESS & EXHIBITION (PM2004) 17-21 OCT 2004 VIENNA, AUSTRIA, October 17, 2004 (2004-10-17 ), -21. October 2004 (2004-10-21) page 6 pp. and GEORGE ET AL: "Strengthening in carbon nanotube / aluminum (CNT / Al) composites" SCRIPTA MATERIALIA, ELSEVIER, AMSTERDAM, NL, Vol. 53, No. 10, November 2005 (2005-11), pages 1159-1163 and CARRENO -MORELLI E ET AL: "Carbon nanotube / magnesium composites" PHYS STATUS SOLIDI A; PHYSICA STATUS SOLIDI (A) APPLIED RESEARCH JUNE 2004, Vol. 201, No. 8, June 2004 (2004-06), pages R53-R55 and C. EDTMAIER: "Metal-matrix composites with carbon nanotubes as a high-strength and high-heat storage phase "[Online] June 3, 2005 (2005-06-03), found on the Internet: XPOO2413867

URL: http: // www. ipp.mpg. de / en / for / areas / material / seminars / MFSem / talks / Edtmaier_03-06-2005.pdf> [found on 2007-01-09] and THOSTENSON ET AL: "Nanocomposites in Contect" COMPOSITIES SCIENCE AND TECHNOLOGY, Vol. 65, 2005, pages 491-516.

Application methods of aluminum-containing alloys are disclosed, inter alia, as an Ospray process. EP 0 411 577 discloses a hypereutectic aluminum alloy which is sprayed out of a first nozzle in the molten state by the ospray process, solid silicon particles or graphite particles, optionally as Si metal or graphite metal compound, also being sprayed from another nozzle without segregating them and which are thereby applied to a carrier device and solidify there to form a block of a duplex aluminum alloy. DE 43 08 612 A1 discloses the production of an aluminum duplex alloy with boron contents, with good properties such as deformability, corrosion resistance and heat resistance, etc. The boron is, for example, by means of a powdery carrier material using an additional spray jet in the spray of the melt of the remaining alloying constituents or applied directly to the Sprühgutträger in a Sprühkompaktiervorrichtung.

DE 100 47 775 C1 discloses the possibility of producing a copper-aluminum multi-substance bronze in an Ospray process.

DE 103 06 919 A1 discloses the production of a composite material with intermetallic phases in the context of a spray compacting based on an arc-wire spraying process with one or more metal solid wires and at least one composite wire comprising a ceramic.

Object of the present invention is to expand the field of application of CNT and to suggest new materials and moldings thereof.

The object is achieved by the invention by a duplex aluminum material of the aforementioned type and a method for producing a duplex aluminum material as a combination of two materials with different properties.

The invention is based on a duplex aluminum material based on aluminum with a first phase and a second phase according to the aforementioned type - A -

According to the invention, the second material component is formed in the form of an aluminum-based composite material comprising aluminum and / or an aluminum-based alloy on the one hand and a non-metal-containing material on the other hand, the first material component being compared to the second material component, respectively has separate material, higher ductility and / or lower tensile strength.

With regard to the manufacturing method, the object is achieved by the invention by a method for producing the duplex aluminum material, comprising the steps:

Processing of proportions of aluminum and / or an aluminum-based alloy and a non-metal in the form of granules, particles, fibers and / or powders by mechanical alloying to form the second material component in the form of an aluminum-based composite material comprising aluminum and / or or to provide an aluminum-based alloy on the one hand and a non-metal-containing material on the other hand;

Spray compacting the duplex aluminum material based on aluminum with a first phase and a second phase; by:

- introducing a first material component in the form of an aluminum-based alloy to form the first phase in at least a first beam; - introducing the second group of materials for forming the second phase in at least one second jet; wherein the first material component compared to the second material component, each as a separate material, has a higher ductility and / or lower tensile strength. In a most preferred embodiment of the invention, the non-metal is formed in the form of CNT. It has been shown in an advantageous manner that the spray-compacting process can preferably be carried out in the form of an ospray process.

A ductility or tensile strength of a material component is in each case related to the material component present as a separate material. In other words, for example, a ductility of a first material in the form of pure aluminum is compared with a ductility of a second material in the form of an aluminum-CNT composite. In a particularly preferred manner, the second material component compared to the first material component, again as a separate material, a lower ductility and / or higher tensile strength.

Duplex aluminum consists of two different types of structure: In duplex aluminum, two essentially single-phase aluminum-based materials are combined, preferably in approximately equal parts, in order to exploit their respective positive material properties. What is meant are mechanical technological properties such as tensile strength, toughness and hardness, but also corrosion-chemical properties, ie rust resistance. Duplex aluminum can be distinguished, for example, by high corrosion resistance, in particular against perforation and stress corrosion cracking and high strength characteristics, as well as increased heat resistance.

Based on this concept, the invention provides suitable duplex aluminum materials.

The invention is based on the idea of combining two or more different alloys to form a so-called aluminum-duplex alloy. Thus, it is an object of this invention to combine an alloy with a very high tensile strength but low ductility with another alloy having a low tensile strength but high ductility.

In a preferred development, similar to the Ospray method, an alloy, preferably that with high ductility or also pure aluminum, e.g. melted in a crucible and sprayed through a nozzle. In this jet of molten aluminum droplets, the alloy with the high tensile strength is sprayed in powder form. This has the advantage that it is also possible to spray alloys reinforced with nanoparticles into powder form without demixing the nanoparticles from the aluminum matrix.

The sprayed-in particles are then advantageously melted for a short time in the hot cloud of liquid droplets, homogeneously mixed and, after a very short time of flight, deposited together on a substrate where the material solidifies immediately (rapid solidification). The time of flight is in the liquid phase for the sprayed Powder particles expediently so short that no segregation of the nanoparticles from the surrounding aluminum occurs.

It is to be understood that the step of spray compaction in the manufacturing process according to the concept of the invention may have different developments. For example, with the aid of an example reference to FIG. 2 of the detailed description, the step of spray compacting can be carried out with a single spray whose carrier substance is formed by the first material component, the second material component being sprayed in powder form into this spray jet. In a modification - with exemplary reference to FIG. 11 - the step of spray compacting can also be carried out with two different spray jets. Thus, in a further development, a first spray jet can be used for merely the first material component in the form of an aluminum-based alloy on a substrate to form a compact specimen, for example in the form of a bolt or billet or the like. to raise. Colinear or at an angle to this, the second spray can be used in this development to deposit the second material component on the substrate. In the aforementioned further development, therefore, the first spray jet would be used almost exclusively for introducing the first material component, while the second spray jet is used almost exclusively for introducing the second material component. The incorporation of the second material component takes place works similar to the previously genann ^¬ th training, namely in that in the formed of pure aluminum or an aluminum alloy support of the second spray, the alloy having the high tensile is sprayed in powder form. In this development, a powdered entry of the alloy with high tensile strength in the first spray is not provided.

In a further development, the first spray jet can certainly also be used to deposit the second material component on the substrate by spraying the alloy with the high tensile strength in powder form into the first spray jet. Optionally, the amount of high tensile strength alloy sprayed in powder form into a first and / or second spray may be different.

Which of the aforementioned refinements proves to be expedient in individual cases can be adjusted according to the desired material according to the invention.

Preferably, similar to the Ospray method, it is now possible to deposit layer by layer on top of one another on the substrate so that over time a compact sample body is formed as a combination of the two different alloys. The mixing ratio can be adjusted by varying the delivery rate of the sprayed powder.

The result is a material with high tensile strength combined with high ductility. Thus, e.g. Fig. 4 is a duplex aluminum structure. The bright parts are the high-strength structural components with integrated CNT, the dark parts represent the soft structural components.

In the following, methods are described, in particular for the production of nanoparticles (eg CNT) reinforced aluminum alloys. These alloys are opposite pure aluminum depending on the CNT concentration a much higher tensile strength (eg factor 5) but at the same time also depending on the CNT concentration a reduced ductility. In addition to the CNT content, both material properties are also influenced by other process parameters, such as the material temperature during production. It is thus possible to set a range of possible tensile / ductility combinations for a specific aluminum alloy by varying these process parameters.

Further advantageous development of the invention can be found in the dependent claims and specify in particular advantageous ways to realize the above-described concept in the context of the task and in terms of further advantages. A particularly preferred first material component has, again in the present case as a separate material, a lower tensile strength than the second component and a higher maximum elongation - that is in particular the softer material component. In a particularly preferred manner, again indicated for a separately present material, the second material component has a higher tensile strength and a lower maximum elongation, i. Ductility - in particular, is the harder material component. This second material component has proven to be particularly easy to produce, in particular using CNT and is also particularly suitable in combination with the first material component for forming a duplex aluminum material.

It has proved to be particularly advantageous that the tensile strength of the first material component is less than 100 MPa and at the same time there is a maximum elongation of more than 15%. In a modification, at least one of the parameters, tensile strength or elongation may be within the stated limits. As a very particularly preferred, a first material component has proven, in which a tensile strength is below 70 MPa and a maximum elongation is more than 20%. In a modification of the last-mentioned further development, only one of the parameters, tensile strength or elongation, is within the limits mentioned.

The second material component may advantageously be provided with a tensile strength of more than 500 MPa and at the same time with a maximum elongation (ductility) of less than 3%. In a modification, at least one of the parameters, tensile strength or elongation may be within the stated limits. As a very particularly preferred, a second material component has proven, in which a tensile strength is above 1000 MPa and a maximum elongation (ductility) of less than 1% is present. In a modification of the last-mentioned further development, only one of the parameters, tensile strength or elongation, is within the limits mentioned.

In addition, it has proven to be advantageous that the second material component - starting from a conventional aluminum alloy or starting from conventional pure aluminum - an aluminum material is used, which has a CNT content such that a decrease in a maximum elongation compared to the aluminum material without CNT content below 30%, advantageously below 10%. Such aluminum materials provided with limited elongation have proven to be particularly ders preferred proven for the second material component. With regard to the construction of the second material component, reference is made to FIG. 13 of the detailed description.

With regard to the further composition of the first and second material components to form a duplex material, reference is made to FIG. 12 of the detailed description. The smaller the proportion of the (harder) second material component in the duplex aluminum material, the more flexible and softer it proves to be. The smaller the proportion of (softer) first material component on the duplex aluminum material, the more inflexible and harder it is.

In a particularly preferred embodiment, the first material component is in the form of pure aluminum or in the form of an aluminum alloy, each with unavoidable impurities and / or additives. The second material component has proven in a particularly preferred embodiment, especially in the form of a mixture, preferably intimate mixture of pure aluminum and / or an aluminum-based alloy on the one hand and CNT on the other hand. The intimate mixture is preferably carried out in the form of a mixture formed by mechanical alloying. Particularly preferred mechanical alloying methods will be described in detail below.

In addition, the first and / or the second material component according to the concept of the invention or a further development thereof can expediently have a further constituent, which can be chosen advantageously depending on the case of use. Another component may in particular be a plastic and / or a polymer and / or a highly heat-resistant component. It has been found that highly heat-resistant constituents can be formed, for example, in the form of a graphite and / or silicon constituent. A SiC component and / or an Al ₂ O ₃ component has also proved to be particularly suitable.

Advantageously, the concept can be implemented by materials comprising at least one metal and / or at least one polymer, in particular layered layers, alternately with layers of CNT.

The second material component is advantageously present in granular form or in the form of particles, the particle size of 0.5 .mu.m to 2000 .mu.m, advantageously from 1 .mu.m to 1000 .mu.m. The individual plies or layers of the metal or polymer may have a thickness of 10 nm to 500'0OO nm, preferably from 20 nm to 200 nm ¹ OOO. The thicknesses of the individual layers or plies of the CNT can range from 20 nm to 50 nm ¹ OOO be from 10 nm to 100 nm ¹ OOO advantageous.

Suitable metals are metals, such as iron and non-ferrous metals and precious metals. Suitable ferrous metals are iron, cobalt and nickel, their alloys and steels. Among the non-ferrous metals, aluminum, magnesium and titanium etc. as well as their alloys can be enumerated. As further examples of metals may be mentioned vanadium, chromium, manganese, copper, zinc, tin, tantalum or tungsten and alloys thereof or the alloys brass and bronze. It is also possible to use rhodium, palladium, platinum, gold and silver. The metals mentioned can be sorted or mixed with one another. Aluminum and its alloys are preferred Trains t. In addition to pure aluminum, the alloys of aluminum are preferred. The metal is used in granular or granular or powder form in the process according to the invention. Typical grain sizes of the metals are from 5 .mu.m to 1000 .mu.m and suitably from 15 .mu.m to 1000 .mu.m.

Suitable polymers are thermoplastic, elastic or thermosetting polymers. Examples are polyolefins, such as polypropylene or polyethylene, cycloolefin copolymers, polyamides, such as the polyamides 6, 12, 66, 610 or 612, polyesters, such as polyethylene terephthalate, polyacrylonitrile, polystyrenes, polycarbonates, polyvinyl chloride, polyvinyl acetate, styrene-butadiene copolymers , Acrylonitrile-butadiene copolymers, polyurethanes, polyacrylates and copolymers, alkyd resins, epoxides, phenol-formaldehyde resins, urea-formaldehyde resins, etc. The polymers are sorted or mixed with each other or in admixture with metal, granular or in granular or powder form in the present invention Method used. Typical particle sizes of the polymers are from 5 .mu.m to 1000 .mu.m and suitably from 15 .mu.m to 1000 .mu.m.

As CNT, for example, catalytically, in an arc, by laser or by gas decomposition generated materials can be used. The CNTs can be single-walled or multi-walled, such as double-walled. The CNTs can be open or closed tubes. The CNT may, for example, of 0.4 nm (nanometers) to 50nm in diameter and a length of 5 nm to 50 nm ¹ OOO. The CNTs may also be sponge-like structures, ie 2- or 3-dimensional frameworks, of mutually cross-linked carbon nanotubes. The diameter of the individual tubes thereby moves in the above-mentioned range of, for example, 0.4 nm to 50 nm Extent of the sponge structure, ie the side lengths of a framework body of CNT, can be given by way of example with 10 nm to 50 ¹ 000 nm, advantageously with I ¹ 000 nm to 50'0OO nm, in each of the dimensions.

The material according to the present invention may contain, for example, from 0.1 to 50% by weight, based on the material, of CNT. Suitably, amounts of 0.3 to 40 wt .-%, preferably from 0.5 to 20 wt .-% and in particular 1 to 10 wt .-% CNT contained in the material. If aluminum or an aluminum alloy is the metal of the material, the material may suitably contain 0.5 to 20% by weight of CNT, based on the material, with 3 to 17% by weight of CNT being preferred and 3 to 6% by weight. % CNT are particularly preferred.

The materials may consist of said metals and said CNT, they may consist of said metals, polymers and CNT, or may consist of the said polymers and CNT, or the above-mentioned materials may contain additional admixtures, for example functional admixtures. Functional additives are, for example, carbon, soot, graphite and diamond modification, glasses, fibers of carbon, plastic fibers, inorganic fibers, glass fibers, silicates, ceramics, carbides or Nitri ^¬ de of aluminum or silicon, such as aluminum carbide, aluminum nitride, silicon carbide or silicon nitride, for example in fiber form, so-called whiskers.

The inventive duplex aluminum material can be produced by mechanical alloying (mechanical alloying) of the respective proportions of metal, polymer and CNT provided for the second material component. Mechanical alloying can be carried out by repeated deformation, breaking and welding of powdery particles of the metal or polymer and the CNT. According to the invention, particularly suitable for mechanical alloying are ball mills with high-energy ball collisions. A suitable energy input is achieved for example in ball mills whose grinding chamber has a cylindrical, preferably circular-cylindrical, cross-section and the grinding chamber, as a rule, is arranged in a horizontal position. The millbase and the grinding balls are moved by the grinding chamber rotating about its cylinder axis and are additionally further accelerated by a driven rotary body extending in the direction of the cylinder axis into the grinding chamber and equipped with a plurality of cams. The speed of the grinding balls is advantageously set to 4 m / s and higher, suitably to 5 m / s, in particular 11 m / s and higher. Velocities of the grinding balls in the range of 6 to 14 m / s, in particular 11 to 14 m / s, are advantageous. Also advantageous is a rotary body, the majority of cam ü distributed over the entire length are arranged. The cams may, for example, extend over 1/10 to 9/10, preferably 4/10 to 8/10, of the radius of the grinding chamber. Also advantageous is a rotary body which extends over the entire extent of the grinding chamber in the cylinder axis. The rotary body is, as well as the grinding chamber, driven independently or synchronously, set by an external drive in motion. The grinding chamber and the rotating body can rotate in the same direction or preferably in opposite directions. The grinding chamber can be evacuated and the grinding process can be operated in a vacuum or the grinding chamber can be filled and operated with a protective or inert gas. Examples of Protective gases are, for example, N ₂ , CO ₂ , of inert gases He or Ar. The grinding chamber and thus the ground material can be heated or cooled. Case by case can be cryogenically ground.

Typical is a grinding time of 10 hours and less. The minimum grinding time is appropriately 15 min. A milling time between 15 minutes and 5 hours is preferred. Particularly preferred is a grinding time of 30 minutes to 3 hours, in particular up to 2 hours.

The ball collisions are the main reason for the energy transfer. The energy transfer can be expressed by the formula Ekin = mv ² , where m is the mass of the sphere and v is the relative velocity of the sphere. The mechanical ball milling is usually carried out with steel balls, for example with a diameter of 2.5 mm and a weight of about 50 g, or with zirconium oxide balls (ZrO ₂ ) of the same diameter with a weight of 0.4 g, carried out.

Depending on the energy input into the ball mill, materials with a preferred distribution of the layers of metal or polymer and CNT can be produced. With increasing energy input, the thickness of the individual layers can be changed. In addition to the energy input, the thickness of the CNT structure fed to the milling process can be used to control the thickness of the CNT layers in the milled material. With increasing energy input, the thickness of the individual layers can be reduced and the respective position can be increased with respect to the expansion in the area. Due to the increasing expansion in the surface, for example, individual layers of CNT can touch each other up to two-dimensional continuous CNT layers or throughout in two dimensions touching CNT layers through a particle. This makes it possible to substantially maintain the excellent properties of the CNT, for example the thermal conductivity and the electrical conductivity of the CNT, on the one hand and the ductility of the metal or the elasticity of the polymer on the other hand in the second material component.

Further control of the properties of the second material component can be achieved by mixing two or more materials of different starting material and / or energy input during their production. Also, materials such as metal or plastic, free of CNT, and one or more CNT-containing materials may be mixed or mechanically alloyed, i. be ground. The different materials, occasionally with the materials, can be mixed or subjected to a second grinding or several grinding operations. For example, the second refining or subsequent refining may take a grinding time of 10 hours or less. The minimum time of the second grinding is appropriate min. Preferably, a second grinding time is between 10 minutes and 5 hours. Particularly preferred is a second grinding time of 15 minutes to 3 hours, in particular up to 2 hours.

For example, a second material component high CNT content and a material lower CNT content or materials different energy input, are processed in a second grinding process. Also, a CNT-containing material, such as a CNT-containing metal, for example aluminum, with a CNT-free metal, for example, also aluminum, are processed in a second grinding operation. The second or grinding process or several grinding operations, respectively. The mechanical alloying is carried out only to the extent that the resulting material is not completely homogenized, but the inherent properties of any material or material are retained and supplement the effects in the final material.

With the described method, it is possible to overcome the intrinsic properties inherent in CNT, which in themselves make targeted processing impossible, such as a lower specific gravity over the specific gravity of metals and the poor wettability of CNT by metals. Thus, as an example of the different density for aluminum 2.7 g / cm ³ and for the CNT 1.3 g / cm ³ are given.

The second material component finds e.g. Use in shaped articles, including semi-finished products and layers produced by spray compacting, thermal spraying, plasma spraying, extrusion processes, sintering processes, pressure-controlled infiltration processes or compression molding.

The present second material component can therefore be processed, for example, by spray-compacting into shaped bodies. In spray compacting, a molten metal melt, for example a steel, magnesium or preferably aluminum or an aluminum alloy, is fed to a spray head via a heated crucible, where it is atomized to form fine droplets and sprayed onto a substrate or base. The initially still molten droplets cool during the flight from the atomizer to the lower substrate. The particle flow hits there at high speed to the so-called To grow up deposit and thereby completely freeze and continue to cool. In the case of spray compacting, the special phase transition "liquid-to-solid", which grows together to form a closed composite of materials, is used for the shaping process in the present case where the second material component containing the CNT is fed to the atomizing device in powder form The process is such that the CNT-containing materials are not or only at the surface melted and no segregation occurs.The particle flow of material and metal droplets impinges on the substrate at high speed on According to the substrate, such as turntable, torsion bar or table, solid bodies, such as bolts, hollow bodies, such as pipes or strips of material, such as sheets or profiles, can be produced as shaped bodies a mixture of metal with embedded CNT with the desired uniform arrangement of the constituents in the structure. For example, the deposit in the form of a bolt (so-called billet) incurred. In subsequent treatment steps, such as extrusion of a bolt, it is possible to produce highly compact and defect-free semi-finished products (tubes, sheets, etc.) or shaped bodies with a lamellar structure. The semifinished products and shaped bodies have, for example, a more or less pronounced anisotropy in the structure and mechanical and physical properties, such as electrical conductivity, thermal conductivity, strength and ductility. Further applications of the duplex aluminum materials according to the invention are in the field of neutron capturing, radiation moderating or the generation of layers for radiation protection. The present second material component leaves in another

Appropriate use as a shaped body or layer, wherein the shaped body by thermal spraying methods such as plasma spraying (plasma spraying) or the cold gas spraying

(CoId gas spraying) are generated. At the thermal

Spray processes are powdered materials in one

Energy source injected and there depending on the process variant only heated, melted or completely melted and accelerated to high speeds (depending on the method and parameter selection from a few m / s up to 1500 m / s) in the direction of the surface to be coated, where the impinging particles precipitate as a layer. When the particles, which are ideally heated or melted only at the surface, encounter very high kinetic energy on the substrate, the CNT preferentially settles to the droplet plane, i. transverse to the beam and impact direction. This leads to a controlled anisotropy of the material properties, such as the tensile strength.

The CNT-containing second material component can alternatively or additionally be further processed by extrusion processes, sintering or die casting process to give moldings. In compression or pressure casting, a slow, in particular laminar, continuous mold filling at high metal pressures is desired. For example, composite materials can be produced by infiltration of porous fiber or particle shaped bodies by a liquefied metal.

In press or die casting process, the second material component, from which the metals containing the CNT in a casting mold as a powdery matrix material, expediently becomes submitted. It is a metal whose melting point is lower than that of the material, for example, in aluminum-containing materials, a metal having a melt temperature of below 750 ⁰ C, slowly pressed into the heated mold. The liquid metal penetrates the powdered matrix material under the applied pressure. Thereafter, the mold can be cooled and the molding removed from the mold. The process can also be carried out continuously. In one embodiment variant, the metal, eg aluminum, can be processed into thixotropic behavior-exhibiting precursors and the CNT can be incorporated. Instead of liquefied metal, a preheated metal in the thixotropic (partly liquid / partly solid) state, containing the CNT, can be pressed into the casting mold. It is also possible, the material in particle or granular form, wherein in the individual particles, the metal is layered in layers alternately with layers of CNT, filled as a debris in the mold, to heat the mold and under pressure a complete mold filling without pores and voids in the To reach resulting moldings. Finally, coarsely mixed metal powders, such as aluminum powder or aluminum having thixotropic properties, and CNT, the CNT in sponge form or as clusters having a diameter of, for example, up to 0.5 mm, can be coarsely mixed and heated in the mold under heat to melt the metal be pressed. Moldings, for example rod-shaped moldings, batchwise or continuously, can be produced at low pressure using the pressure casting methods. Aluminum with thixotropic properties is obtainable, for example, by melting aluminum or aluminum alloys and rapid cooling with constant stirring until solidification. In a particularly preferred development of the two ^¬ te beam may be an identical with the first beam beam - in other words, the first component and the second component when needed can be supplied in common example of a spray nozzle to represent a single spray during spray. In addition, however, above all a variant has proven to be advantageous in which a second beam separately formed by the first is used to supply the second material component to the first beam. Depending on requirements, both or one of the jet may be formed as a spray jet. In addition, depending on the requirements of the first and the second beam may be collinear or be provided as needed at a certain angle to each other.

As already partially explained above, it has proved to be particularly advantageous that the first material component is introduced in the molten state into the first jet. For this purpose, the first material component, for example by spraying through a nozzle as liquid droplets, can be introduced into the first jet.

The second material component can be introduced in a preferred manner in the powdery state in the second jet. In particular, a particulate state of the second material component, preferably as a nanoparticle, is suitable for this purpose. Such and similar particles can be particularly preferably prepared according to one of the grinding methods described above. The arrangement of a first and a separate second jet provided according to this further embodiment ensures, above all, the introduction of the second component, without a segregation of, for example, nanoparticles with an aluminum component. Matrix, can be done. The sprayed particles are briefly melted in the hot cloud of, for example, liquid droplets of the first material component, homogeneously mixed and deposited after a comparatively short flight time together on a substrate where the material immediately solidifies in the form of duplex aluminum material.

In other likewise suitable developments, it is also possible that the first material component is introduced in the powdered state in the second beam and the second material component in the molten state in the first beam.

Overall, the aluminum duplex materials and moldings show good thermal conductivity and electrical conductivity. The temperature behavior of moldings of the materials according to the invention is outstanding. The thermal expansion is low. The creep strain improves. By adding the CNT to the metals, such as aluminum, a substantial refinement of the grain structure to, for example, 0.6-0.7 Fm can be observed. The addition of CNT to the metals can influence recrystallization of the metal, resp. prevent. Crack propagation can also be reduced or prevented by the CNT in the metal. An inventive material is characterized in particular by a high heat resistance.

Embodiments of the invention will now be described below with reference to the drawing. This is not necessarily to scale the embodiments, but the drawing, where appropriate for explanation, in a schematized and / or slightly distorted form executed. With regard to additions to the teachings directly recognizable from the drawing reference is made to the relevant prior art. It should be noted that various modifications and changes in the form and detail of an embodiment may be made without departing from the general idea of the invention. The features of the invention disclosed in the description, in the drawing and in the claims may be essential both individually and in any combination for the development of the invention. In addition, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention. The general idea of the invention is not limited to the exact form or detail of the preferred embodiment shown and described below or limited to an article which would be limited in comparison to the subject matter claimed in the claims. For the given design ranges, values within the specified limits should also be disclosed as limit values and be arbitrarily usable and claimable.

In detail, FIGS. 1 to 9 of the drawings are as follows:

Fig. 1: shows an illustrative scheme illustrating the possibility of a massive increase in the tensile strength of an aluminum-based composite with CNT compared to pure aluminum;

2 shows a schematic representation of a spray compacting device for applying a Duplex aluminum material according to the concept of the invention;

3 shows a schematic explanatory illustration of the flight phase of the first material component in FIG

Form of pure aluminum and the second material component in the form of an aluminum / CNT composite;

4 shows an exemplary micrograph of a duplex aluminum microstructure in a particle of a second material component in the form of an Al / CNT composite with clearly recognizable CNT phases within the aluminum matrix;

Fig. 5 to

Fig. 9: show the starting materials and finished material components viewed through a microscope, each at high magnification;

Fig. 5: shows a mixture of aluminum particles and CNT agglomerates prior to mechanical alloying to form a preferred second material component in magnification. The bright aluminum particles are denoted by (1). The dark ones

CNT agglomerates are designated (2);

Fig. 6: shows in enlargement a preferred second material component in powder or particle form after mechanical alloying. There are no visible CNTs. All CNTs are contained in the aluminum particles, which have been deformed, broken and welded many times; Fig. 7: shows the section through a particle of a preferred second material component in the form of an Al / CNT composite. Within the particle of the material is a layer structure, resp. they are layers, recognizable. These are the layers or layers of mutually gray aluminum aluminum tinted in the picture and light / dark line-shaped deposits of CNT visible;

8 shows the section through another particle of a preferred second material component in the form of an Al / CNT composite. Within a particle of the material is a layer structure, resp. they are layers, recognizable. These are the ones

Layers or layers of alternatively aluminum metal (3), visible as a light structure and CNT (4) as dark linear deposits in the aluminum. Compared with the material according to FIG. 7, the material in FIG. 9 has smaller proportions of CNT, which are separated by thicker layers of aluminum. The gray areas (5) surrounding the particles depict the resin in which the material is embedded for microscopic recording;

9 shows a sponge structure made of CNT, as it can be used, for example, for the production of presently inventive materials in an electron micrograph. Also can be used such a sponge structure, for example in the pressure casting process; FIG. 10: schematically illustrates the fundamental processes of breaking, stacking and welding occurring during mechanical alloying, which in the case of high-frequency multiple repetition in the context of a high-energy milling process becomes a so-called

As a result, "Severe Pastic Deformation" of the materials involved results in materials of the second material component, as exemplified in FIGS. 6 to 8;

11 shows a schematic representation of a further embodiment of a spray compacting device for applying a duplex aluminum material according to the concept of the invention;

Fig. 12: shows a volume fraction effect of hard and soft components in terms of tensile strength and elongation versus percent by volume of the hard material in percent of the finished duplex aluminum material;

13 shows the CNT content dependence of tensile strength and elongation as a function of the CNT content in% by weight of an aluminum material as it can be used in particular for a harder second material component according to the concept of the invention;

14 shows the electron micrograph of a micrograph of a preferred duplex aluminum

Material obtained using an advantageous spray compacting method according to the concept of the invention; Fig. 15: shows a typical plan view image from an electrostatic ^¬ nenmikroskopischen intake in a tensile test of a tie-rod produced from the inventive duplex aluminum material.

Examples:

By mechanically alloying a powder of pure aluminum and CNT by high-energy milling in a ball mill, reaching a ball speed of over 11 m / s, different materials are produced by different grinding time. The materials are further processed in a powder extrusion process and a series of rod-shaped specimens is produced. The specimens are subjected to the tests listed in the table. The temperature in the table indicates the processing temperature during the extrusion process. The test specimens contain 6% by weight of CNT. The times 30, 60 and 120 min indicate the grinding time during mechanical alloying for the production of the materials. Example 1 is a comparative experiment with pure aluminum, without CNT.

Example No. Fabric / Tensile Hardness Elast. -

Grinding time N / mm ² Brinell module *

KN / mm ²

Literature, pure Al 70-100 35.9 70

(Bulk)

Ex 1, pure Al, 138-142 40.1 71-81

Ex. 2, 30min, 222-231 66.4 98-101

Ex. 3, 60min, 236-241, 71.1, 71-78

Ex 4, 120min, 427-471 160.2 114-125

*Modulus of elasticity

It can be seen from the table that the tensile strength and hardness each increased by about 400%. The values can be controlled by the content of CNT in the material and the grinding process, such as the grinding time, for the production of the material. The modulus of elasticity can increase by 80%. The modulus of elasticity can be affected by the milling time during mechanical alloying in the production of the material and by the processing temperature in the extrusion process.

1 shows a number of tensile strength / ductility curves relating to a second material component in the form of an intimate mixture of an Al / CNT composite compared to pure aluminum (Al + 0% CNT). The tensile strength representing highest points of such curves are referred to herein as "stress / strain limit" and show that, for example, in the case of an aluminum-based composite with 8% CNT (Al + 8% CNT), the tensile strength of such a composite is almost a factor of 5 above the tensile strength of pure aluminum. Below this, tensile strength values with lower CNT contents are achievable (eg Al + 6% CNT or Al + 4% CNT) in which composites it is also ensured that the ductility is nevertheless comparatively high. Aluminum-based composites with a lower CNT content also have the advantage that an extrusion temperature is comparatively low.

2 shows the diagram of a spray compacting apparatus 11, in which pure aluminum present in a crucible 12, for example, can be fed to a tundish 14 and then into a spray nozzle 15 atomizing the liquid to a first jet 16 with suitably selected droplets Be fed spray cone. A present, not shown - usually collinear or slightly angled slightly - separate beam sprays powder particles of the second material component, present in the form of a pure aluminum / CNT composite in the spray cone of the first spray jet 6. The cloud shown schematically in Fig. 3 from liquid pure aluminum droplets 17 and the composite of Al / CNT particles 18 in partially melted state 19 reach the substrate 21 with a suitable impact speed 20 and solidify there immediately to a sample body 22.

A micrograph of a particle of a second material component in the form of an Al / CNT composite for producing such a sample is shown in FIG. 4. This clearly shows in the light areas the microstructure identify the CNT parts within the aluminum plates. Such high-strength structural components with integrated CNT are surrounded by dark-recognizable parts of a soft microstructure made of pure aluminum. Overall, this provides an aluminum duplex material which combines a first material ^component with comparatively high ductility and low tensile strength with a second material component with comparatively low ductility and high tensile strength as a phase mixture.

FIG. 10 illustrates the essential processes involved in a high energy milling process for mechanical alloying - namely welding, breaking and stacking - which ultimately lead to severe plastic deformation of the materials involved (severe plastic deformation). When applying the high energy milling method to a mixture of preferably harder aluminum alloy with CNT material, this results in a very strong solidification of the materials involved by grinding and as a result to a particularly preferred second (harder) material component according to the concept of the invention , The solidification takes place essentially according to the known HALL-PETCH relationship. This means that the smaller the diameter of the particles involved, the greater the maximum achievable tensile strength. Specifically, according to the HALL-PETCH relationship, the maximum achievable tensile strength P should be inversely proportional to the root of the particle diameter involved, with the validity of the relationship starting in any case for particle diameters below 1 μm. The high energy milling of aluminum materials such as pure aluminum or an aluminum alloy of relatively high hardness with CNT has not only the advantage illustrated in FIG. 10 that the CNT content is intimately incorporated into the aluminum material, but in addition there is the advantage that CNT serves as a grinding aid. According to a particularly preferred embodiment, the proportion of hitherto customary grinding aids, such as stearic acid or the like, can thereby be reduced. be reduced or eliminated altogether.

Fig. 11 shows - in a modification of a method shown schematically in Fig. 2 for producing a duplex aluminum material - schematically a manufacturing method in which two non-collinear spray jets 31, 32 are used for applying the first and second material components. Other identical parts or parts with the same function as in FIG. 11 and FIG. 2 and FIG. 3 are provided with the same reference numerals. In the present case, two powder injectors 41, 42 are used for the powdery introduction of the second material component into a carrier jet 31, 32 made of liquid aluminum droplets 17. In this case, the angle between the first spray jet 31 and 32 - in this case by adjusting the second spray jet 32 - be changed. Likewise, in the present case, the amount of powder for introduction into the first and second spray jet 31, 32 can be adjusted as needed. Optionally, in a modification, the first spray jet 31 may be free of powder delivery, i. be fed only from aluminum material, such as pure aluminum or alloyed aluminum.

By such and other arrangements, an advantageous billet of aluminum duplex material can be made. On the one hand, it is recognized that no billet would be produced using only powdered CNT. de. Secondly, it was recognized that in a strong ^¬ He overheating of CNT, in particular above 600 ⁰ C, Alumini ^¬ would arise to carbide. The latter would mean that a manufactured material would be highly susceptible to splintering. By introducing this powdery CNT-containing second material component into a liquid phase of a spray jet with liquid aluminum droplets 17, preferably of pure aluminum or a harder aluminum alloy, this is prevented. The short flying time also prevents adverse chemical reactions. It has proven to be particularly advantageous that two spray nozzles or two spray jets are used to form the duplex aluminum body.

In an advantageous subsequent production step, a further compression by, for example, an extrusion process or the like. done at the billet.

13 shows, by way of example, the tensile strength and elongation behavior of a preferred aluminum material component as a function of the CNT content for forming the (harder) second material component according to the concept of the invention. The starting alloy used may be, for example, an aluminum alloy of the 7000 series whose elongation is maximal at a low CNT content. A CNT content in the second material component has proved to be particularly advantageous such that a decrease in the elongation in the range between 10% to 30% is present. The tensile strength is advantageously also in the upper tensile strength range, in particular between the maximum tensile strength value and the point of intersection with the elongation curve. It turned out to be a CNT content in the region of the crossing region between tensile strength curve and elongation curve is advantageous.

FIG. 12 shows, by way of example, the development of the tensile strength and elongation in a finished duplex aluminum material with increasing proportion of the (harder) second material component in percent of the finished duplex aluminum material. This makes it clear that virtually any advantageous high value of a tensile strength can nevertheless be set by varying the volume fraction of the hard material in the form of the second, harder material component while maintaining the maximum elongation.

Fig. 14 illustrates the fine, inhomogeneous, but even distribution of harder second material component and softer first material component in a finished duplex aluminum material. The hard phase of the duplex aluminum material can be seen in the bright areas. The soft phase of the duplex aluminum material is visible in the dark areas.

15 shows a typical crack pattern of a tensile layer shown in the upper part of FIG. 15 in the lower enlarged area. With reference to the marking CNT-I and CNT-2, CNTs of different lengths embedded clearly in the aluminum material can be seen.

In summary, the invention provides the processing of a composite material in particle or powder form, containing carbon nanotubes (CNT), wherein in the material, for example, a metal in layers in a thickness of 10 nm to 500 ¹ 000 nm alternately with layers of CNT in a Thickness of 10 nm to 100 ¹ 000 nm layered. The material is produced by mechanical alloying, ie by repeated deformation, breaking and welding of metal particles and CNT particles, preferably by ball milling, containing a grinding chamber and grinding balls as grinding media and a rotating body for generating high-energy ball collisions. For the production of duplex aluminum, a method is described in which a material of the composite material and an aluminum alloy with different properties are alloyed in a single ospray process.

Claims

1. A duplex aluminum material based on aluminum having a first phase and a second phase, - is prepared in a Sprühkompaktierverfahren, with at least introduced via a first beam first material component in the form of an aluminum-based alloy to form the the first phase and a second material component introduced at least via a second beam to form the second phase, characterized in that the second material component in the form of an aluminum-based composite material, comprising aluminum and / or an aluminum-based alloy on the one hand and a non-metal containing Material on the other hand, is formed, wherein the first material component compared to the second material component, each as a separate material, a higher elongation (ductility) and / or lower tensile strength.

2. duplex aluminum material according to claim 1, characterized in that the second material component compared to the first material component, each as a separate material, a lower elongation (ductility) and / or higher tensile strength.

3. duplex aluminum material according to claim 1 or 2, since ^¬ characterized in that the first material component, as a separate work ^¬ material, a tensile strength (stress) of less than 100MPa, especially less than 70MPa, and / or a maximum elongation (ductility Strain) of more than 15%, in particular more than 20% has.

4. duplex aluminum material according to one of claims 1 to 3, characterized in that the second material component, as a separate material, a tensile strength of more than 500 MPa, in particular more than 1000 MPa, and / or a maximum elongation (ductility) less than 3%, in particular less than 1%.

5. duplex aluminum material according to one of claims 1 to 4, characterized in that the first material component in the form of pure aluminum is formed with unavoidable impurities and / or additives.

6. duplex aluminum material according to one of claims 1 to 5, characterized in that the first material component is formed in the form of an aluminum alloy with unavoidable impurities and / or additives.

7. duplex aluminum material according to one of claims 1 to 6, characterized in that the second material component is in the form of a, in particular intimate, mixture, preferably in the form of a mixture formed by mechanical alloying of pure aluminum and / or an aluminum-based alloy on the one hand and CNT on the other hand.

8. duplex aluminum material according to one of claims 1 to 7, characterized in that the first and / or the second material component further ter a plastic and / or polymer and / or a high heat resistant component, in particular a graphite and / or Has silicon component.

9. duplex aluminum material according to one of claims 1 to 8, characterized in that the second beam is an identical with the first beam, collinear or preferably separate beam, in particular a spray jet.

10. duplex aluminum material according to one of claims 1 to 9, characterized in that the first material component is introduced in a molten state in the first jet, in particular as liquid droplets, preferably sprayed through a nozzle is introduced into the first beam.

11. duplex aluminum material according to one of claims 1 to 10, characterized in that the second material component in a powdery state, preferably as a particle, in particular as Na nopartikel is introduced into the second beam, in particular without segregation of the aluminum and / or the aluminum-based alloy on the one hand and the non-metal-containing material, preferably CNT, on the other hand is introduced.

12. duplex aluminum material according to one of claims 1 to 11, characterized in that the first material component is introduced in the powdered state in the second beam and / or the second material component in a molten state in the first beam.

13 duplex aluminum material according to one of claims 1 to 12, characterized in that in the material at least one metal and / or at least one plastic layered in layers alternately with layers of CNT.

14. duplex aluminum material according to one of claims 1 to 13, characterized in that, a particle size of the second material component of 0.5 nm to 2000 nm, advantageously from 1 .mu.m to 1000 .mu.m.

15. duplex aluminum material according to one of claims 1 to 14, characterized in that individual layers of a metal or plastic have a thickness of 10 nm to 50O ¹ 000 nm, advantageously from 20 nm to 200'0OO nm.

16. duplex aluminum material according to one of claims 1 to 15, characterized in that thicknesses of CNT contained layers of 10 nm to 100 ¹ 000 nm, preferably from 20 nm to 50 * 000 nm amount.

17 duplex aluminum material according to one of claims 1 to 16, characterized in that within the particles of the material at least one metal or plastic layers are layered alternately with layers of CNT in uniformly arranged layer thickness.

18. duplex aluminum material according to any one of claims 1 to 17, characterized in that within the particles of the material at least one metal or plastic layers are stacked alternately with layers of CNT, within the particle areas with high concentration of CNT Layers and low concentration of metal or plastic layers are present.

19 duplex aluminum material according to one of claims 1 to 18, characterized in that touch through the particles of the material through several CNT layers in subregions and form through the particles continuously CNT penetrations.

20. duplex aluminum material according to any one of claims 1 to 19, characterized in that as metals, in addition to aluminum or its alloys, iron and non-ferrous metals, precious metals, suitably ferrous metals from the series of iron, cobalt and nickel, their alloys, as well as steels, non - ferrous metals, suitably aluminum, magnesium and titanium and their alloys, metals from the series vanadium, chromium, manganese, copper, zinc, tin, tantalum or tungsten and alloys thereof or the alloys from the series of brass and bronze or Metals from the series rhodium, palladium, platinum, gold and silver, sorted or mixed with each other, are included.

21. duplex aluminum material according to any one of claims 1 to 20, characterized in that as polymers thermoplastic, elastic or thermosetting polymers, preferably polyolefins, cycoolooler copolymers, polyamides, polyesters, polyacrylonitrile, polystyrenes, polycarbonates, polyvinyl chloride , Polyvinyl acetate, styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, polyurethanes, polyacrylates and copolymers, alkyd resins, epoxies, phenol-formaldehyde resins, urea-formaldehyde resins, sorted or mixed with one another.

22. duplex aluminum material according to one of claims 1 to 21, characterized in that the CNTs have a diameter of 0.4 nm to 50 nm and a length of 5 nm to 50 ¹ 000 nm.

23 duplex aluminum material according to one of claims 1 to 22, characterized in that the CNT represent 2- or 3-dimensional scaffold body, made of carbon nanotubes, preferably scaffold body with side lengths of 10 nm to 50O00 nm.

24. duplex aluminum material according to any one of claims 1 to 23, characterized in that the material amounts of CNT from 0.1 to 50 wt .-%, based on the material, expedient amounts of CNT from 0.3 to 40 Wt .-%, preferably amounts of CNT from 0.5 to 20 wt .-% and in particular amounts of CNT from 1 to 6 wt .-%.

25. duplex aluminum material according to any one of claims

1 to 24, characterized in that

Aluminum or an aluminum alloy is the metal of the material and the material contains 0.5 to 10 wt.% CNT, preferably 3 to 6 wt .-%, CNT.

26. A method for producing a duplex aluminum material according to any one of claims 1 to 25, comprising the steps - processing of proportions of aluminum and / or an aluminum-based alloy and a non-metal, in particular CNT, each in the form of granules, particles , Fibers and / or powders by mecha- alloying in order to provide the second material component in the form of an aluminum-based composite material comprising aluminum and / or an aluminum-based alloy on the one hand and a non-metal-containing material on the other hand,

Spray-compacting the duplex aluminum material based on aluminum with a first phase and a second phase, in particular in the context of an OSPRAY process

Introducing a first material component in the form of an aluminum-based alloy to form the first phase in at least one first beam

Introducing the second material component to form the second phase in at least one second jet, wherein

the first material component compared to the second material component, each having a separate material, a higher ductility and / or lower tensile strength.

27. A method for producing a duplex aluminum material according to claim 26, characterized in that a mechanical alloying by repeated deformation tion, breaking and welding of the particles of metal or plastic and particles of CNT, preferably by mechanical alloying in a ball mill containing a grinding chamber and grinding balls as Mahlkόr- per by high-energy ball collisions, is performed.

28. A method for producing a duplex aluminum material according to claim 26 or 27, characterized in that a ball mill has a Mahlkaminer with a cylindrical, preferably circular cylindrical, cross-section and moves the grinding balls through the rotating around its cylinder axis grinding chamber and by a in the direction of the cylinder axis in the grinding chamber extending, equipped with a plurality of cams, driven rotary body can be accelerated.

29. A method for producing a duplex aluminum material according to any one of claims 26 to 28, characterized in that the speed of the grinding balls at least 6 m / s, in particular 11 m / s, and advantageously the speed of the grinding balls in the range of 6 up to 14 m / s, in particular 11 m / s to 14 m / s.

30. A method for producing a duplex aluminum material according to any one of claims 26 to 29, characterized in that the grinding time is 10 hours and less and the minimum grinding time is 5 min and preferably the grinding time between 15 min and 5 hours, particularly preferably from 30 minutes to 3 hours and especially up to 2 hours.

31. A method for producing a duplex aluminum material according to any one of claims 26 to 30, characterized in that the rotary body, a plurality of cams distributed over the entire length and extends advantageously over the entire extent of the Mahlkämmer in the cylinder axis.

32. A method for producing a duplex aluminum material according to any one of claims 26 to 31, characterized in that two or more different materials are mixed same or different starting material and / or energy input or subjected to a second grinding or more grinding.

33. A method for producing a duplex aluminum material according to any one of claims 26 to 32, characterized in that a CNT-free metal or plastic and one or more different materials same or different starting material and / or energy input, mixed or a second Grinding or multiple grinding are subjected.

34. Use of the duplex aluminum material according to one of claims 1 to 33 for sprachenkompaktie- reindeer, thermal spraying, plasma spraying, extrusion processes, sintering process, pressure-controlled infiltration or compression molding molded body.