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    • 专利摘要:
    Manufacture of composite materials reinforced with carbon fiber by injection of a high pressure aluminum alloy. The invention provides a process for obtaining a material characterized in that said process comprises the following consecutive steps: (a) preheating an injection mold to a temperature greater than 160ºC; (b) placing at least one carbon fiber in the injection mold; (c) closing the injection mold; (d) injecting a liquid aluminum alloy into the injection mold at a pressure greater than 10 MPa; (e) open the injection mold; and (f) extracting the material from the injection mold in solid state. Likewise, the invention provides the composite material thus obtained with good homogeneity and porosity properties and with improved mechanical and thermal properties compared to the unreinforced matrix and which is useful, among others, in the transport industry, as pieces with good rigidity, mechanical resistance, thermal conductivity and ability to dissipate heat. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2802282A1
    申请号:ES201930614
    申请日:2019-07-02
    公开日:2021-01-18
    发明作者:Martín Pedro Luis Marino；Martín Raúl Arias；Hinojal Alberto Carrero；Barreiro Belén Torres；Ramos Joaquín Rams；Fernández Alejandro Ureña；Martínez María Sánchez；Galisteo Antonio Julio López；Herrero Pilar Rodrigo；Sapia Camilo Mercado；Sanz Javier Bedmar
    申请人:Fundiciones Y Matriceria Sl；Universidad Rey Juan Carlos；
    IPC主号:
    专利说明:

    [0002] Manufacture of composite materials reinforced with carbon fiber by injection of a high pressure aluminum alloy
    [0004] FIELD OF THE INVENTION
    [0005] The present invention relates to the field of manufacturing continuous carbon fiber reinforcing metal matrix composites. Such a material is called a metal matrix composite (MMC) in English.
    [0007] BACKGROUND OF THE INVENTION
    [0008] Carbon fiber reinforced (CF) aluminum matrix composites are of great interest because carbon fibers reduce the coefficient of thermal expansion, increase mechanical strength and elastic modulus. Furthermore, if these fibers are interconnected or continuous, they promote thermal dissipation.
    [0010] However, the manufacture of composite materials from a carbon fiber reinforced aluminum matrix is complex due to the low wettability of aluminum with carbon fiber. Wettability is defined as the ability of a liquid to spread over the surface of a solid substrate. Wettability improves when aluminum reacts with the fiber to form AUC3, but the formation of this brittle compound in the fiber / matrix interface degrades the mechanical properties of the resulting material.
    [0012] The manufacturing methods for liquid carbon fiber reinforced metal matrix composites are based on infiltration of preforms. When the infiltration processes are carried out correctly, microporosity, macro-voids, fiber breakage and local variations in the volume fraction of the fibers can be avoided. Otherwise, these and other defects can appear extensively by the material and result in a decrease in the thermal and mechanical properties of the part, such as thermal conductivity, heat dissipation, Young's modulus, tensile strength, resistance tensile yield, strain stress 0.2% at the elastic limit point and stress at break.
    [0014] OBJECT OF THE INVENTION
    [0015] The object of the present invention, therefore, is to provide a process for obtaining a continuous carbon fiber reinforcing and metal matrix composite material, which solves the problems and overcomes the disadvantages mentioned above. In particular, the object is to provide a process for obtaining a composite material with a metal matrix and carbon fiber reinforcement, where said composite material has no defects and therefore has improved mechanical and thermal properties compared to unreinforced material. In particular, said material must have greater rigidity and mechanical resistance, in addition to greater thermal conductivity.
    [0017] Another object is to provide a process to obtain a composite material with a metal matrix and carbon fiber reinforcement where said process does not use metallic or ceramic coatings, which are usually deposited on the carbon fiber to increase the wettability of the carbon fibers by cast aluminum.
    [0019] Finally, another object of the invention is to provide the use of said material to manufacture a piece for automotive, lighting, urban furniture, or for the aeronautical or electronic industries.
    [0021] BRIEF DESCRIPTION OF THE INVENTION
    [0023] The present invention describes, in one embodiment, a process for obtaining a material, characterized in that said process comprises the following consecutive steps of:
    [0024] (a) preheating an injection mold to a temperature greater than 160 ° C;
    [0025] (b) placing at least one carbon fiber in said injection mold;
    [0026] (c) closing the injection mold;
    [0027] (d) injecting a liquid aluminum alloy into the injection mold at a pressure greater than 10 MPa;
    [0028] (e) open the injection mold; Y
    [0029] (f) extracting the material from the injection mold in solid state.
    [0031] In another embodiment of the present invention, a process is described to obtain a material characterized in that said process comprises the following consecutive steps:
    [0032] (a) preheating an injection mold to a temperature greater than 220 ° C;
    [0033] (b) placing at least one carbon fiber in the injection mold, where said carbon fiber has a tensile strength greater than 5 GPa or a modulus of elasticity greater than 300 GPa;
    [0034] (c) closing the injection mold;
    [0035] (d) inject a liquid aluminum alloy into the injection mold at a temperature lower than 720 ° C and a pressure of between 28 and 35 MPa, where the main elements of the aluminum alloy are aluminum and silicon (Al-Si) or aluminum, silicon and copper (Al-Si-Cu) and the subsequent solidification of the resulting material within the injection mold takes place in a time of less than 15 s;
    [0036] (e) open the injection mold; Y
    [0037] (f) extract the material from the injection mold in solid state where, before placing the carbon fiber in the injection mold, the carbon fiber is pretreated by heat treatment at a temperature between 170 and 180 ° C for at least 24 hours.
    [0039] In another additional embodiment of the present invention, a material comprising a metal matrix and a reinforcement is described, characterized in that said material is obtainable by any of the methods described in the present description.
    [0041] In another additional embodiment of the present invention, the use of the material obtainable by any of the procedures described in the present description to manufacture a part for the automotive, lighting, urban furniture, or for the aeronautical or electronic industries is described.
    [0043] DESCRIPTION OF THE FIGURES
    [0045] Figure 1 . Scheme of the manufacture of composite material in a mold (Z) with a fabric (Y) and an alloy (X), once stage (d) has been carried out according to the process of the present invention, and before stage (f) , A in a plane parallel to the plane of the fabric, and B in a cross section of the plane AA.
    [0047] Figure 2 . Orientation of the fiber that forms the fabrics: A flat, B crossed and C satin.
    [0049] Figure 3 . A Aluminum infiltration on carbon fiber preform showing the placement of a carbon fiber preform in a mold, the pouring of liquid aluminum and the application of pressure, and B infiltration of alternating layers of aluminum and carbon fiber (sandwich type ), showing the placement of layers of carbon fiber and aluminum in a mold, heating the mold, and applying pressure.
    [0050] Figure 4 . Piece manufactured by the method of the invention with a unidirectional reinforcement where the orientation of the longitudinal direction of the carbon fiber is perpendicular to the injection direction; where the longitudinal direction of the test piece L0 is parallel to the longitudinal direction of the piece and to the longitudinal direction of the carbon fiber; and where the longitudinal direction of the T90 specimen is perpendicular to the longitudinal direction of the piece and to the longitudinal direction of the carbon fiber.
    [0052] Figure 5 . Clutch discs manufactured without reinforcement or by the method of the invention with (A) unidirectional wicks with the longitudinal direction of said wicks oriented perpendicular (U90) or parallel (U0) or 45 ° oblique (U45) to the injection direction; or (B) tissue (T) with the longitudinal direction of said locks oriented perpendicular or parallel (T) or oblique (T45) to the injection direction.
    [0054] DESCRIPTION OF THE INVENTION
    [0056] The present invention describes a process for injecting aluminum or an aluminum alloy, under high pressure, into a mold containing at least one continuous carbon fiber.
    [0058] The material obtained by said process is, in particular, a composite material comprising a metal matrix and a reinforcement. In the context of the invention, the term "composite material" refers to a material or MMC that is composed of a metallic matrix, in this case of different aluminum alloys, which contains a continuous carbon fiber reinforcement.
    [0060] In an embodiment of the present invention, a process is described to obtain a material characterized in that said process comprises the following consecutive steps of:
    [0061] (a) preheating an injection mold to a temperature greater than 160 ° C;
    [0062] (b) placing at least one carbon fiber, preferably a continuous woven or unidirectional carbon fiber, in the injection mold;
    [0063] (c) closing the injection mold;
    [0064] (d) injecting a liquid aluminum alloy into the injection mold at a pressure greater than 10 MPa;
    [0065] (e) open the injection mold; Y
    [0066] (f) extracting from injection mold material (i.e., one piece) in solid state.
    [0067] In step (a), the injection mold is preheated to a temperature greater than 160 ° C, preferably at a temperature between 165 and 300 ° C, more preferably at a temperature between 170 and 280 ° C. Said preheating is carried out by means of a heat source. Examples of such heat sources are, but are not limited to, a furnace, a flame, or a liquid aluminum alloy previously injected into said mold. In a preferred embodiment, the preheating of step (a) is carried out by using a flame or by the latent heat remaining in the injection mold previously caused by having carried out the procedure by using a flame.
    [0069] In step (b), one at least one carbon fiber, optionally comprised in a preform, is placed in the preheated injection mold according to step (a). A preform comprises at least one carbon fiber and has a predetermined shape to allow it to be placed in the injection mold.
    [0071] A carbon fiber is an amorphous material that comprises carbon filaments, where each filament comprises sheets of carbon atoms arranged in a regular hexagonal pattern that are placed randomly, tightly or together. Also, the term "continuous carbon fiber" refers to a ceramic (non-metallic) material in the form of long fibers that can be used in different morphologies, such as a unidirectional weave or wicks. Preferably, the carbon fiber is selected from:
    [0072] - a carbon fiber of the HM type (called high modulus in English) that has a Young's modulus greater than 300 GPa (almost 30% of the elastic constant C11 of a single graphite crystal) and a tensile strength ratio: Young's modulus of 0.01;
    [0073] - a carbon fiber of the HT type (called high tensile in English) having a Young's modulus of 150 - 300 GPa and a force: stiffness ratio of 1.5 - 2.0%; it has a tensile strength greater than 3000 MPa (3 GPa);
    [0074] - a carbon fiber of the IM type (called intermediate modulus in English) that has a Young's modulus greater than 275 - 350 GPa (up to almost 35% of the elastic constant C11 of a single graphite crystal) and a resistance ratio tensile: Young's modulus of 0.01;
    [0075] - a carbon fiber of the LM type (called low modulus in English) that has a Young's modulus of up to almost 10% of the elastic constant C11 of a single graphite crystal; or
    [0076] - a carbon fiber of the UHM type (called ultra high modulus in English) that has a Young's modulus greater than 600 GPa (more than 55% of the elastic constant C 11 of a single graphite crystal). In a more preferred embodiment, the carbon fiber is an HT type carbon fiber. Even more preferably, the carbon fiber has a tensile strength greater than 5 GPa or a modulus of elasticity greater than 300 GPa, measured. Said properties of carbon fiber are determined according to ASTM D4018-99 (see also JSA-JIS R 7601: 1986).
    [0078] In one embodiment, each carbon fiber is derived from a polymer blend comprising polyacrylonitrile (PAN). When PAN is heated under suitable temperature conditions, the chains of carbon molecules come together while the other components separate, the carbon atoms of the polymer change their distribution and form a stable structure of tightly linked rings that support each other. the others. By means of a new heating, the rings are joined together in 'ribbons' of hexagons of carbon atoms, very flexible. The flexible joint of the slats prevents them from slipping, as occurs with the flat structure of graphite, which results in a notable increase in the strength of the material.
    [0080] The fibers are drawn into filaments that are composed of between 92 and 100 percent carbon atoms, depending on the properties that are sought. Thus, in one embodiment of the process of the present invention, the carbon fiber is a carbon fiber with a minimum carbon content of 92% by weight, preferably with a minimum content of 95% by weight, more preferably with a minimum content. 97% by weight.
    [0082] Individual carbon filaments have a diameter ranging from 5 to 8 microns (^ m). Carbon fibers can be supplied in the form of a continuous wick which is an unwound bundle of continuous filaments. The sizes of the wicks are determined based on the number of thousands of individual filaments that compose them. With these wicks, fabrics can be made, interlacing (weaving) the fibers. And with those fabrics, a preform can be manufactured that consists of shaping said fabrics with a shape similar to the final product that is desired.
    [0084] The use of fabrics that comprise at least one carbon fiber is of great importance in order to achieve a controlled distribution of said fiber in the metal matrix and to eliminate possible agglomerates of the same that may form in the composite material. Furthermore, these fabrics are capable of distributing the load in two directions. Importantly, depending on the orientation of the carbon fiber in the fabric, A carbon cloth can be stronger in one direction or just as strong in all directions. Fibers offer better properties when interwoven in the direction of stresses, that is, in an ideal case the directions of the fibers should align with the direction of external force. For this reason, a small piece of material obtained by the process of the invention can withstand the impact of many tons and deform minimally, since the shock forces are distributed and are cushioned by the at least one carbon fiber or the mesh or fabric made from it. Hence the importance in choosing the number and orientation of the fibers that form the fabric to obtain rigidity and resistance that meets the desired requirements in the application.
    [0086] The following are the most common fabrics:
    [0087] (i) Flat or plain fabric (Figure 2A), a flat fabric is one in which each longitudinal and transversal yarn passes over one yarn and under the next. This construction provides a reinforced fabric that can be used extensively in general applications and ensures good build laminates. This type of fabric is very stable, so it is hardly distorted.
    [0088] (ii) Twill or twill weave (Figure 2B), in a crossover weave the number of longitudinal yarns that can pass over the transverse (and reciprocally) can be varied, giving different constructions of crossover weaves.
    [0089] (iii) Satin or satin fabric (Figure 2C), in satin fabrics the interlacing is similar to that of the crossover (ii), although the number of longitudinal and transverse yarns that pass reciprocally above and below, before interlacing, is older. Therefore, one side of the fabric is built primarily with longitudinal fibers, and the other side - with transverse fibers. It has an excellent surface finish, similar to satin, hence its name.
    [0091] Thus, in an embodiment of the process of the present invention at least one carbon fiber is comprised in a fabric comprising a continuous fiber and / or discontinuous fibers or a wick comprising a continuous fiber and / or discontinuous fibers, where said fabric is a flat, double-breasted or satin weave.
    [0093] A polymeric sizing is usually applied to carbon fibers in order to protect the condition of their surface and prevent the formation of surface cracks that could degrade their mechanical properties.
    [0094] In one embodiment of the process of the present invention, the carbon fiber is pretreated before being placed in the injection mold, by heat treatment at a temperature greater than 170 ° C for at least 24 hours, more preferably at a temperature between 170 and 250 ° C for at least 24 hours. Pretreatment by means of said heat treatment eliminates the size of at least one carbon fiber, and therefore, eliminates the possibility that the size is volatilized during the high pressure injection process causing an unwanted porosity in the material.
    [0096] Placing at least one carbon fiber, optionally comprised in a preform, in the preheated injection mold according to step (a) comprises placing said fiber in the part or parts of said mold into which the alloy is injected. liquid aluminum according to step (d). Said parts of the mold can be any cavity, recess and / or tube that is formed when closing the mold according to step (c) and preferably into which said alloy is injected. More preferably, said fiber is not placed in the parts of the mold through which the alloy is injected and / or allow the escape of air or gases (such as risers, inlets and outlets of the mold). In one embodiment of the method of the present invention, step (b) comprises placing the carbon fiber in the injection mold, using protrusions thereof as support.
    [0098] The injection mold has the necessary shape to be able to place at least one carbon fiber, optionally comprised in a preform, in it and carry out the formation of the material in a predetermined shape. In addition, the injection mold comprises parts that allow the injection of the liquid alloy and / or the escape of air and / or gases and that remain open throughout the process as a riser and / or an injection hole. Preferably, the placement of the continuous fiber is done by clamping, more preferably by manually hooking, at least one carbon fiber, optionally comprised in a preform, on the protrusions of the injection mold with care to avoid loss of orientation or agglomerations by the fiber.
    [0100] Said mold is made of at least one material that has a higher casting temperature than the temperature of the injected aluminum alloy. Preferably, said mold is made of sand, a salt, plaster, a metal or an alloy, or combinations thereof, more preferably said mold is made of a metal or an alloy.
    [0101] In a particular embodiment of the process of the invention, the preparation of the reinforcement for its placement in the mold consists of the following stages:
    [0102] (i) cutting a fabric (mesh or cloth) comprising at least one carbon fiber with the desired size;
    [0103] (ii) remove the size of the carbon fiber by means of a heat treatment:
    [0104] introduction in an oven at 175 ° C for two days; Y
    [0105] (iii) extract strands from the tissue as appropriate to obtain various volume fractions and / or morphologies
    [0107] The modification of the fabric wicks allows changing various parameters such as the volumetric fraction of the carbon fiber or the morphology of the reinforcement (if it is fabric or unidirectional wicks). In this way, it is possible to promote wettability and avoid agglomerations of the reinforcement and optimize the mechanical and thermal properties of the material resulting from the process of the present invention, such as thermal conductivity and Young's modulus.
    [0109] Once at least one carbon fiber, optionally included in a preform, has been placed in the injection mold, said mold is closed according to step (c). Once said injection mold is closed, only the parts of the mold through which the alloy is injected and / or allow the escape of air or gases, remain open (such as the risers, inlets and outlets of the mold).
    [0111] In step (d), a liquid aluminum alloy is injected into the injection mold.
    [0113] The liquid aluminum alloy is preferably a metal alloy comprising aluminum and at least one alloying element. An alloying element can change the surface tension of the melt or react with the reinforcement. In the event that reactions occur at the interface, a new interfacial system appears, and the interfacial energies may have changed, thus modifying the contact angle. The addition of alloying elements in aluminum alloys, such as silicon and magnesium, improves wettability, as shown in Table 1.
    [0114] Table 1 . Carbon fiber wettability by binary aluminum alloys.
    [0118] In a preferred embodiment, the aluminum alloy is any cast aluminum alloy, more preferably an aluminum alloy comprising aluminum and silicon (Al-Si) or aluminum, silicon and copper (Al-Si-Cu) or aluminum and magnesium. (Al-Mg) or aluminum, silicon and magnesium (Al-Si-Mg) or aluminum, magnesium and copper (Al-Mg-Cu) or aluminum, silicon, magnesium and copper (Al-Si-Mg-Cu) as elements main of it. For the purposes of the present invention, the main element is understood to be that element comprised in an alloy in an amount greater than 0.25% by weight of the total alloy. In one embodiment of the process of the present invention, the aluminum alloy comprises aluminum and silicon (Al-Si) or aluminum, silicon and copper (Al-Si-Cu) as the main elements thereof. In a more preferred embodiment, said aluminum alloy is an alloy that belongs to the designation system (standard), UNE-EN-1706-98 and chosen from the group of: EN AC-46000, EN AC-46500, EN AC-47000 and EN AC-44100, more preferably EN AC-46000.
    [0120] As carbon fibers have a low wettability by molten metal, the application of high pressure is necessary. In the state of the art, the manufacture of carbon fiber and aluminum matrix composite materials can be carried out, for example, through the squeeze-casting technique from the infiltration of preforms by molten aluminum applying pressure (Figure 3A) , or also by alternate layers of fiber and aluminum, heating and applying pressure (Figure 3B). The differences that exist between the squeeze-casting technique and the technique of the present invention are mainly the range of pressure applied, which in the case of the squeeze-casting technique is higher (between 100 and 160 MPa), and the time also higher pressure application (between 30 s and 4 minutes, until the manufactured part solidifies).
    [0122] Therefore, in step (d) of the process of the present invention, the liquid aluminum alloy is injected at a pressure greater than 10 MPa, preferably at a pressure between 10 and 90 MPa, more preferably at a pressure between 12 and 60 MPa, even more preferably at a pressure between 16 and 40 MPa, much more preferably at a pressure between 28 and 35 MPa, still much more preferably at a pressure between 30 and 32 MPa. The high pressure applied makes it possible to overcome the surface tension of the aluminum alloy and thus the injection and, therefore, the infiltration of all the carbon fibers, optionally included in a preform, and the intimate matrix / reinforcement contact is achieved.
    [0124] The process of the present invention is a rapid process, which reduces the risk of chemical reactions at the matrix / reinforcement interface. Furthermore, both the shape of the preform comprising at least one carbon fiber and its placement in the mold can be selected, making it possible to obtain locally reinforced parts.
    [0126] The viscosity of the molten metal is low, allowing pressure infiltration to be suitable for injecting the liquid aluminum alloy into the injection mold according to step (d) and, therefore, for the manufacture of MMCs. Furthermore, the material has low porosity, due to the efficient pouring or flow of the liquid.
    [0128] In general, when the injection processes and, therefore, infiltration, are carried out according to step (d) of the process of the invention, microporosity, macro-voids, fiber breakage and local variations in the volume fraction of the fibers are avoided. . Otherwise, these and other defects can appear extensively by the material.
    [0130] In one embodiment of the process of the present invention, the temperature at which the liquid aluminum alloy is injected into the injection mold is less than 800 ° C, preferably between 650 and 750 ° C, more preferably between 670 and 710 ° C .
    [0132] In one embodiment of the process of the present invention, the aluminum alloy Liquid is injected into the injection mold at a speed of 10 - 30 m / s until the carbon fiber is covered by the liquid aluminum alloy and then the liquid aluminum alloy is injected at a speed of 40 - 100 m / s. Preferably, the liquid aluminum alloy is injected into the injection mold at a speed of 12-20 m / s until the carbon fiber is covered by the liquid aluminum alloy and then the liquid aluminum alloy is injected at a rate. speed of 45 - 80 m / s.
    [0134] Thus, in a highly preferred embodiment of the process of the present invention, the aluminum alloy comprises aluminum and silicon (Al-Si) or aluminum, silicon and copper (Al-Si-Cu) as the main elements, and said alloy is injected of aluminum in liquid state in the injection mold at a temperature between 650 and 750 ° C, at a pressure between 25 and 40 MPa, and at a speed of 12 - 20 m / s until the at least one carbon fiber remains covered by the liquid aluminum alloy and then the liquid aluminum alloy is injected at a speed of 40 - 80 m / s.
    [0136] Once the aluminum alloy has been injected according to step (d) of the process of the present invention (Figures 1A and 1B), the composite material solidifies in the injection mold, at least the exterior of said composite material solidifies. The solidification time of said composite material is preferably less than 100 s. In one embodiment of the process of the present invention, the time of said solidification of the composite material is less than 29 s, preferably less than 20 s, more preferably between 5 and 15 s. In another embodiment, the liquid aluminum alloy is injected at a pressure between 16 and 40 MPa and the time of said solidification of the composite material is between 5 and 18 s.
    [0138] This rapid forced solidification allows to mitigate the segregation of particles in the material, due to their push by the solidification front, which also guarantees a fine-tuning of the structure, since there is a critical growth rate from which the solid particles are enveloped instead of being pushed. In the microstructure of composite materials, it is observed that the grain size of the matrix is strongly controlled by the effects of heat flow and, the higher the preheating of the carbon fibers or the preforms that comprise them, the more it is favored. a thick columnar structure. Therefore, in step (a) of the process of the present invention, the preheating of the mold of injection at a temperature greater than 160 ° C, as described above.
    [0140] It has also been observed, in most composite materials, that fibers do not act as preferential nucleation sites (onset of solidification). Therefore, during dendritic solidification, which occurs in most of the matrices of interest, the last portion of the liquid, which is usually enriched in solute, is located around the fibers. Prolonged matrix / fiber contact, normally under high hydrostatic pressure (ie, applied pressure) and with solute enrichment, favors the formation of a strong interfacial bond, in many cases promoted by a localized chemical reaction. In the method of the present invention, AUC3 is not formed because the solidification time is very fast and does not allow time for it to form.
    [0142] Step (e) of the process of the invention comprises opening the injection mold. Said opening is carried out once the composite material has solidified, at least on the outside of said material. Then, in step (f) of the process of the invention, the composite material is extracted from the injection mold in a solid state.
    [0144] When subsequent shaping is required, short carbon fiber reinforced composites can be subjected to plastic deformation (extrusion, stamping, forging and rolling). With this, it is possible to reduce porosity and for the fibers to have a preferred orientation, which implies an improvement in mechanical properties. For continuous fiber CMMs, forming by plastic deformation is not possible and cutting is necessary.
    [0146] In another even more preferred embodiment of the present invention, a process is described to obtain a composite material characterized in that said process comprises the following consecutive steps:
    [0147] (a) preheating an injection mold to a temperature greater than 170 ° C;
    [0148] (b) placing at least one carbon fiber in the injection mold, where said carbon fiber has a tensile strength greater than 5 GPa or a modulus of elasticity greater than 300 GPa;
    [0149] (c) closing the injection mold;
    [0150] (d) inject a liquid aluminum alloy into the injection mold at a temperature lower than 720 ° C and a pressure between 28 and 35 MPa, where the main elements of the aluminum alloy are aluminum and silicon (Al-Si) or aluminum, silicon and copper (Al-Si-Cu) and the subsequent solidification of the resulting material within the injection mold takes place in a time of less than 20 s;
    [0151] (e) opening the injection mold; Y
    [0152] (f) extract material from injection mold in solid state
    [0153] where, before placing it in the injection mold, the carbon fiber is pretreated by heat treatment at a temperature between 170 and 180 ° C for at least 24 hours.
    [0155] When the composite material is in the shape of a street lamp, step (a) of preheating an injection mold is preferably carried out at a temperature greater than 165 ° C, more preferably at a temperature between 165 and 250 ° C, even more preferably between 170 and 220 ° C. When the composite material is in the shape of a clutch disc, step (a) of preheating an injection mold is preferably carried out at a temperature greater than 200 ° C, more preferably at a temperature between 200 and 300 ° C, even more preferably between 230 and 280 ° C.
    [0157] In particular, the invention relates to a process for obtaining a composite material with a continuous carbon fiber reinforced aluminum alloy matrix where said fiber is arranged in woven or unidirectional configurations. Said material has low porosity and improved mechanical and thermal properties compared to the unreinforced matrix, such as thermal conductivity and Young's modulus, among others. Thus, in an embodiment of the present invention, a material comprising a metal matrix and reinforcement is described, characterized in that said material is made by the process of the present invention. Said material:
    [0158] - reduces the weight of the parts manufactured with it.
    [0159] - increases the mechanical resistance of unreinforced materials.
    [0160] - increases the thermal conductivity of unreinforced materials.
    [0162] This invention is based on the use of a high pressure aluminum injection process (> 10 MPa, preferably at the pressures mentioned above), which allows reducing the temperature of the aluminum alloy and avoiding the formation of AUC3, while The high pressures used force the union of the metallic matrix with the carbon fiber without the need to use metallic coatings, (for example, copper or nickel, or ceramic compatible with the aluminum alloy to improve the wettability of the reinforcement by the liquid alloy, or matrix) applied on the reinforcements to avoid the reaction between the matrix and the carbon fibers. The method of the invention achieves, on the other On the other hand, adequate wettability without the presence of AI3C4 or other materials in the interface that weaken the final structure of the material, thanks to the high pressures (the liquid aluminum alloy is injected into the injection mold at a pressure greater than 10 MPa, preferably at the above-mentioned pressures), low temperature (the temperature at which the liquid aluminum alloy is injected into the injection mold is less than 800 ° C) and short time (the solidification time of the material is less than 20 s) of high pressure injection processes. In the process of the invention, therefore:
    [0163] - The problem induced by infiltration pressure that forces these materials to be manufactured by means of a high pressure greater than 100 MPa is solved, in the case of squeeze casting, thus greatly reducing the cost.
    [0164] - the production rate is increased.
    [0165] - the need for preforms and pretreated carbon fibers with coatings is eliminated. Furthermore, in a preferred embodiment a carbon fiber fabric is used which eliminates the preform manufacturing step necessary when short fibers or continuous fiber are used.
    [0167] Thus, the material produced by the process of the present invention can be used to manufacture a part for the transportation, lighting or furniture industries. In one embodiment, said material is used to manufacture an automotive, lighting, urban furniture part, or for the aeronautical or electronic industries, preferably an automotive part or for the aeronautical industry, more preferably a clutch disc.
    [0169] Among others, the material produced by the process of the present invention allows the design of heat dissipation systems, or cooling, in luminaires with LEDs with complex geometries that are usually made of extruded aluminum alloys or alloys with lower thermal conductivity. The use of composite materials with carbon fiber reinforcement would allow the realization of said cooling systems much more efficiently and at a lower cost than with conventional methods.
    [0171] In addition, the material produced by the process of the present invention allows the design of a motor support that is a structural part that has properties of high rigidity, high mechanical resistance and high resistance to fatigue, in addition to having a reduced weight, which are the properties necessary for application in the automotive industry.
    [0172] EXAMPLES
    [0174] Example 1: General manufacturing procedure
    [0175] An aluminum alloy EN AC-46000 was used as a matrix and a HexTow® AS4C GP 3K carbon fiber layer, which is sized, was used as reinforcement.
    [0177] The carbon fiber reinforcement is trimmed to the desired shape. Subsequently, a sizing removal heat treatment is carried out at 175 ° C, which is volatilized. The reinforcement is placed in the injection mold. The mold must be preheated beforehand, either by applying a flame or by maintaining said heating thanks to serial injection.
    [0179] Subsequently, the injection is carried out using an IDRA 900 machine with the following injection parameters:
    [0180] Alloy injection speed in 1st phase: 15 - 18 m / s
    [0181] Alloy injection speed in the 2nd phase: 50 - 60 m / s
    [0182] Multiplied pressure: 30 - 32 MPa
    [0183] Solidification time: 12s
    [0184] Injection temperature: 680 - 700 ° C
    [0185] Riser thickness: 35 - 45 mm
    [0186] Mold temperature: 230 - 280 ° C
    [0188] The first injection phase consists of filling the mold with the alloy and in the second injection phase it is compressed to fill pores. The injection of the first phase is done with a piston and that of the second phase is done with gas (N2).
    [0190] After the injection, the piece is extracted, eliminating the riser and carrying out the opportune surface machining.
    [0192] Example 2: Procedure to obtain lampposts made of aluminum matrix composite material with continuous carbon fiber reinforcement in the form of:
    [0193] (A) unidirectional wicks with the longitudinal direction of said wicks oriented perpendicular or parallel to the injection direction; or
    [0194] (B) fabric with the longitudinal direction of said locks oriented perpendicular or parallel (090) to the injection direction.
    [0195] 2.1 Manufacturing
    [0196] In each lamppost an aluminum alloy EN AC-46000 was used as a matrix and a HexTow® AS4C GP 3K carbon fiber layer, which is sized, as reinforcement.
    [0198] For streetlights that include continuous reinforcement of type (A), the carbon fiber fabric is cut into the desired shape with an additional 3 cm in circumference. Subsequently, a sizing removal heat treatment is carried out at 175 ° C, which is volatilized. Then all the wicks in the direction in which reinforcement is not required are extracted from the fabric (for example, if you want to reinforce with the weft wicks, the warp wicks are eliminated and vice versa), leaving the wicks that are in the 3 cm extra that have been added before, so that the wicks are manageable and remain parallel.
    [0200] A layer of the carbon fiber preform is placed in the injection mold, hooking it on the protrusions of the same, ensuring that it remains immovable. If the wicks are unstable, thermal paste can be added to better adhere them to the mold. The mold must be preheated beforehand, either by applying a flame or by maintaining said heating thanks to serial injection.
    [0202] For streetlights comprising continuous reinforcement of type (B), the carbon fiber fabric is cut into the desired shape. Subsequently, a sizing removal heat treatment is carried out at 175 ° C, which is volatilized. One out of every five fibers is then removed from the fabric in both the warp and weft directions to improve the wettability of the aluminum, giving it more room to flow without being hampered.
    [0204] A layer of the carbon fiber preform is placed in the injection mold, hooking it on the protrusions of the same, ensuring that it remains immovable. The mold must be preheated beforehand, either by applying a flame or by maintaining said heating thanks to serial injection.
    [0206] Subsequently, for streetlights that include continuous reinforcement of type (A) or (B), the injection is carried out using an IDRA 900 machine with the injection parameters indicated in Example 1. After the injection, each piece is extracted, eliminating the riser and performing the opportune surface machining, before cutting specimens of the piece (lamppost) in order to carry out two types of tests. The nomenclature of the cut specimens for thermal and mechanical conductivity tests consists of a letter and a number:
    [0207] • The letter corresponds to the orientation of the longitudinal direction of the specimen in the part (the longitudinal direction of the specimen being the longest direction between two opposite faces of said specimen), in such a way that if it is in the longitudinal direction of the the same (that is, the direction in the plane of the carbon fiber layer that is perpendicular to the injection direction) is called L and if it is in the transverse direction (that is, the direction in the plane of the carbon fiber layer) carbon fiber that is parallel to the injection direction) is called T.
    [0208] • The number corresponds to the orientation of the longitudinal direction of the carbon fiber reinforcement (the longitudinal direction of the reinforcement being the longest direction of said fiber) with respect to the longitudinal direction of the specimen. If the reinforcement is unidirectional and it is in the longitudinal direction of the specimen it will have a 0, while if it is in the transverse direction of the specimen it will have a 90. If the reinforcement is a fabric it will have the number 090.
    [0209] In this way, if you have a specimen where the longitudinal direction of said specimen is oriented in the longitudinal direction of the piece (lamppost) that has a unidirectional reinforcement with its longitudinal direction oriented in the same direction, the specimen will have the name of Le , while if in the same piece (lamppost) the specimen meets the longitudinal direction of said specimen oriented in the direction perpendicular to the previous one, it will be called T90, as shown in Figure 4.
    [0211] 2.2 Thermal properties: thermal conductivity
    [0212] Tests were carried out to calculate the relative thermal conductivity ( K,) of each material, this being the quotient between the thermal conductivity of the composite material and that of the unreinforced material. In this way, if Kr is greater than 1, the thermal conductivity of the composite material will be greater than that of the unreinforced material and if it is less than 1, the thermal conductivity will be less than that of the base alloy.
    [0214] The tests at a general level consist of heating one end of a test piece taken from the street lamps with different reinforcement morphologies and measuring the time it takes for the cold end of it to heat up. The medium for heating the end of the cylinder is boiling water. The tests are carried out in isolation, in such a way that the conduction mechanism is enhanced.
    [0215] The thermal conductivity results are those shown in Table 2.
    [0217] Table 2 . Thermal conductivity with respect to the unreinforced alloy
    [0219]
    [0222] It is observed that, in general, the carbon fiber reinforced specimens perform thermally better than the unreinforced alloy when driving mechanisms prevail. On the other hand, the reinforcement morphology that works best is the unidirectional one in the direction of the specimen (0), which is that of heat transmission.
    [0224] 2.3 Mechanical properties
    [0225] Tensile tests were carried out where it could be seen that the mechanical properties [Young's modulus (E), tensile strength (Om) and yield strength (Oy)], especially Young's modulus (E) it tends to be maintained, except in the L90 and To specimens, which improve as it happened with the thermal properties.
    [0227] The results of mechanical properties are those shown in Table 3.
    [0229] Table 3 . Mechanical properties relative to the unreinforced alloy
    [0234] Example 3: Procedure to obtain aluminum matrix composite material clutch discs with continuous carbon fiber reinforcement in the form of:
    [0235] (A) unidirectional wicks with the longitudinal direction of said wicks oriented perpendicular (U90) or parallel (U0) or oblique (U45) to the injection direction; or
    [0236] (B) tissue (T) with the longitudinal direction of said locks oriented perpendicular or parallel (T) or oblique (T45) to the injection direction (see Figure 5).
    [0238] In each clutch disc, an EN AC-46000 aluminum alloy was used as a matrix and a HexTow® AS4C GP 3K carbon fiber layer, which is sized, as reinforcement.
    [0240] For clutch discs that comprise continuous reinforcement of type (A), the carbon fiber fabric is cut into the desired shape (round), which is the one whose dimensions coincide with the base of the clutch disc with 3 cm more radius. Subsequently, a sizing removal heat treatment is carried out at 175 ° C, which is volatilized. Then all the wicks in the direction in which reinforcement is not required are extracted from the fabric (for example, if you want to reinforce with the weft wicks, the warp wicks are eliminated and vice versa), leaving the wicks that are in the 3 cm extra that have been added before, so that the wicks are manageable and remain parallel.
    [0242] A layer of the carbon fiber preform is placed in the injection mold, hooking it on the protuberance or central pin of the same (the one that gives the formal internal diameter of the disc), separating the fibers that remain in the central area so that it forms well the inside diameter, making sure that it remains immovable with respect to the area of the base of the disc during the whole process (that it does not move to the area of the fins). If the wicks are unstable, thermal paste can be added to better adhere them to the mold. The mold must be preheated beforehand, either by applying a flame or by maintaining said heating thanks to serial injection.
    [0244] For clutch discs that comprise continuous reinforcement of type (B), the carbon fiber fabric is cut into the desired shape (round), which is that whose dimensions coincide with the base of the clutch disc. Subsequently, a sizing removal heat treatment is carried out at 175 ° C, which is volatilized. One out of every five fibers is then removed from the fabric in both the warp and weft directions to improve the wettability of the aluminum, giving it more room to flow without being hampered.
    [0246] A layer of the carbon fiber preform is placed in the injection mold, hooking it on the boss or central pin of the same (the one that shapes the diameter inside the disc), separating the fibers that remain in the central area so that the internal diameter is formed well, making sure that it remains immovable with respect to the area of the base of the disc throughout the process (that it does not move to the area of fins). The mold must be preheated beforehand, either by applying a flame or by maintaining said heating thanks to serial injection.
    [0248] Subsequently, for clutch discs that include continuous reinforcement of type (A) or (B), the injection is carried out using an IDRA 900 machine with the injection parameters indicated in Example 1. After injection, each part is removed, eliminating the riser and performing the appropriate surface machining, before cutting specimens from each disc in order to carry out two types of tests.
    [0250] These pieces have improved mechanical and thermal properties compared to unreinforced material. Different reinforcement arrangements have been tested on each clutch disc as shown in Figure 5.
    [0252] 3.2 Thermal properties: thermal conductivity
    [0253] The thermal conductivity tests of the clutch discs comprising continuous reinforcement of type (A) were carried out according to the method described in Example 2. The results of said thermal conductivity tests are those shown in Table 4, where it can be seen that Clutch discs comprising continuous reinforcement of type (A) with the longitudinal direction of the wicks oriented parallel to the injection direction have better thermal conductivity in heat transfer than alloys of the state of the art without reinforcement, consistent with the Results of Example 2.
    [0255] Table 4 . Thermal conductivity with respect to the unreinforced alloy
    [0260] 3.3 Mechanical properties
    [0261] The tests of the mechanical properties of the types (A) and (B) clutch discs were carried out according to the method described in Example 2. The nomenclature of the specimens in each clutch disc is based on the orientation it occupies in the own disk. In this way, the specimen R is the one with the longitudinal direction oriented in the radial direction and the O is the one with the longitudinal direction occupying a transverse orientation or perpendicular to the radial. Likewise, the specimen V is the one that has a longitudinal direction that occupies a vertical orientation, that is, with an orientation at 0 ° with respect to the injection direction. The results of mechanical properties are those shown in Table 5 where it could be seen that the mechanical properties [Young's modulus (E), the strain at 0.2% at the elastic limit point (Rp0.2) and the stress at break (Rm)], especially Young's modulus (E) tends to be maintained, except in the L90 and T0 specimens, which improve as occurred with the thermal properties.
    [0263] Table 5 . Mechanical properties relative to the unreinforced alloy
    权利要求:
    Claims (15)
    [1]
    1. Procedure to obtain a material characterized in that said procedure comprises the following consecutive stages:
    (a) preheating an injection mold to a temperature greater than 160 ° C;
    (b) placing at least one carbon fiber in the injection mold;
    (c) closing the injection mold;
    (d) injecting a liquid aluminum alloy into the injection mold at a pressure greater than 10 MPa;
    (e) open the injection mold; Y
    (f) extracting the solid state material from the injection mold.
    [2]
    2. The method according to claim 1, characterized in that, before placing the at least one carbon fiber in the injection mold, said carbon fiber is pre-treated by heat treatment at a temperature greater than 170 ° C for at least 24 hours, optionally followed by a treatment with a metallic coating or with a ceramic coating compatible with the aluminum alloy.
    [3]
    3. The method according to any of claims 1 and 2, characterized in that the main elements of the aluminum alloy are aluminum and silicon (Al-Si) or aluminum, silicon and copper (Al-Si-Cu) or aluminum, silicon and magnesium (Al-Si-Mg).
    [4]
    4. The method according to claim 3, characterized in that the aluminum alloy is an alloy chosen from the group of: EN AC-46000, EN AC-46500, EN AC-47000 and EN AC-44100.
    [5]
    5. The process according to any of the preceding claims, characterized in that the carbon fiber is a carbon fiber with a minimum carbon content of 92% by weight.
    [6]
    6. The method according to claim 5, characterized in that the carbon fiber is a carbon fiber with a tensile strength greater than 5 GPa or a modulus of elasticity greater than 300 GPa.
    [7]
    7. The method according to claim 6, characterized in that the carbon fiber It is a carbon fiber made from polyacrylonitrile.
    [8]
    8. The method according to any of the preceding claims, characterized in that the temperature at which the liquid aluminum alloy is injected into the injection mold is less than 800 ° C.
    [9]
    The method according to any of the preceding claims, characterized in that the liquid aluminum alloy is injected into the injection mold at a speed of between 10 - 30 m / s until the carbon fiber is covered by the liquid aluminum alloy and then at a speed of between 40 - 100 m / s.
    [10]
    The method according to any of the preceding claims, characterized in that the solidification time of the material is less than 20 s.
    [11]
    The process according to any of the preceding claims, characterized in that step (a) is carried out by means of a flame or by means of the latent heat remaining in the injection mold caused by previously having carried out the process of any of the previous claims by means of a flame. .
    [12]
    12. The method according to any of the preceding claims, characterized in that the carbon fiber is comprised of a fabric comprising a continuous fiber and / or discontinuous fibers or a wick comprising a continuous fiber and / or discontinuous fibers, wherein said fabric is a flat, double-breasted or satin weave.
    [13]
    13. The method according to any of the preceding claims, characterized in that step (b) comprises placing the carbon fiber in the injection mold, using its protrusions as support.
    [14]
    14. A material comprising a metal matrix and a reinforcement obtainable by the method of claims 1 to 13.
    [15]
    15. Use of the material of claim 14 to manufacture a part for automotive, lighting, urban furniture, or for the aeronautical or electronics industries.
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    同族专利:
    公开号 | 公开日
    WO2021001590A1|2021-01-07|
    ES2802282B2|2021-05-25|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    CN102127722A|2011-03-22|2011-07-20|上海交通大学|Three-dimensional orthotropic carbon fiber reinforced aluminum-based composite material and preparation method thereof|
    KR20170057610A|2015-11-17|2017-05-25|이성균|Poly-Dopamine · Fiber Alloy Molded Body Coated with Functional Nanomaterial|
    CN107662312A|2016-07-28|2018-02-06|上海悦野健康科技有限公司|A kind of preparation method of integrated wheel of bicycle|
    CN108251768A|2018-01-23|2018-07-06|沈阳工业大学|A kind of regular polygon crucible prepares the device and method of carbon fiber aluminum-based compound material|
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    PCT/ES2020/070429| WO2021001590A1|2019-07-02|2020-07-02|Manufacture of carbon fibre-reinforced composite materials by means of the high-pressure injection of an aluminium alloy|
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