JPS6316453B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for producing a new material for fiber-reinforced metal composite materials. FIBER REINFORCED is a lightweight material with excellent mechanical performance, high temperature heat resistance, and corrosion resistance.
METAL (hereinafter referred to as FRM) has been actively developed in recent years. However, some difficult problems remain unresolved in the development of this material.
It was thought that it would still take many years of study to put FRM into practical use. One of the problems was that high strength fibers suitable for reinforcing composites had not been found. That is, boron fibers, carbon fibers, alumina whiskers, etc. have conventionally been used as strength fibers. However, for example, boron fibers tend to react with many practical metals and easily form boron compounds at relatively high temperatures, resulting in a significant decrease in the strength of the composite material. Furthermore, the fiber diameter is generally large, exceeding 100 μm, and therefore has poor flexibility and processability. Additionally, carbon fibers are easily oxidized, so when mixing them with metals to produce FRM, it is necessary to do so in a vacuum or in an inert gas, and at moderately high temperatures, they easily form carbides with various metals. Although several methods of coating fiber surfaces have been proposed to prevent this, they are still far from being put to practical use. Furthermore, since carbon fiber is electrically conductive, the matrix metal of the composite material is gradually electrolytically eroded.
There is a problem that the physical properties of alumina·
Whiskers do not have the disadvantage of reacting with such a matrix, but on the other hand, they have poor wettability with the matrix and tend to form pores in the composite material, thus causing FRM.
physical properties are inferior. In addition, since the fibers are expensive and necessarily short, it is difficult to align them in a certain direction. Therefore, it is difficult to create a reinforced composite material with controlled fiber orientation, which is the best form of composite material. Requires manufacturing process. Another problem that hinders the practical application of FRMs is related to the process of mixing reinforcing fibers and metals to form FRMs. That is, the reinforcing fibers are placed in a mold in the form of a bundle of elastic fibers, or in the form of a cross or mat, and mixed with metal. At this time, the metal is obstructed by fibers, cloth, etc., making it difficult for the metal to penetrate into the entire molded body, and voids are likely to occur at various locations within the molded body. In particular, it is not easy for the metal to penetrate into the gaps between individual fibers inside the fiber bundle, resulting in numerous small voids. Such voids affect the physical properties of the obtained FRM,
It significantly reduces mechanical performance, especially at high temperatures. Another problem in the FRM molding process is
When the reinforcing fibers and metal are mixed and integrated in the mold, the position of the fibers may move, resulting in uneven distribution of the fibers in the molded product or distribution of the fibers at desired positions in the molded product. It's difficult. Therefore, it is not possible to mold an FRM that has the performance as designed. As a result of the inventors' earnest efforts to solve various problems that hinder the practical application of FRM,
As described below, aluminous fibers are used as reinforcing fibers, the fiber bundle is pre-impregnated with metal, and the raw material is processed into a cloth or mat shape, which is then put into a mold. The present invention was achieved by discovering that by adding metal as necessary and molding, the distribution state of reinforcing fibers in the molded product can be controlled, and an FRM with no voids and excellent mechanical performance can be obtained. It is something. To explain the present invention in more detail, the alumina fiber used in the present invention has an alumina (Al ₂ O ₃ ) content of 72% by weight or more and 100% by weight or less, preferably 75% by weight or more and 98% by weight or less. and the silica (SiO ₂ ) content is 0% by weight or more and 28% by weight or less,
Preferably, it has a composition of 2% by weight or more and 25% by weight or less, and according to the results of studies by the present inventors, it has extremely high tensile strength and elastic modulus, and furthermore, it has excellent properties even at high temperatures in an oxidizing atmosphere. It has excellent heat resistance without losing its mechanical properties. Also, among the silica contents, 10% of the total weight of fibers
In a range of not more than 5% by weight, preferably not more than 5% by weight,
Lithium, beryllium, boron, sodium, magnesium, silicon, phosphorus, potassium, calcium, titanium, chromium, manganese, yttrium, zirconium, lanthanum, tungsten,
It may be replaced with one or more oxides of barium. In addition, in the X-ray structure of the alumina fiber, α
- It is desirable that the material exhibits substantially no alumina reflection. Generally, in inorganic fibers, crystal grains of the inorganic substance that form fibers grow within the fibers at high temperatures, and fiber strength is significantly reduced due to grain boundary destruction between these crystal grains. According to the results of studies conducted by the present inventors, this situation is characterized by the appearance of reflection by α-alumina in the X-ray diffraction image of the alumina fiber. Therefore, the alumina fiber used in the present invention must be manufactured so that reflection of α-alumina does not appear in its X-ray diffraction image. According to the findings of the present inventors, such alumina fibers have excellent properties as reinforcing fibers, as described below. First, it has a high tensile strength of 10 t/cm ² or more and a high tensile modulus of 1000 t/cm ² or more. Also, since it is made of stable oxide, it will not deteriorate even if exposed to high temperatures of over 1000℃ in the air for a long time. Since the main component is alumina, it does not react and is stable even when it comes into contact with various molten metals. Furthermore, the density
It is light at 2.5 to 3.5 g/cc. These performances depend on the silica content in the fibers, but the inventors have found that they are best when the silica content is 28% by weight or less, preferably 2% by weight or more and 25% by weight or less. Excellent performance is achieved. Such alumina fibers can be produced in various ways. For example, a precursor fiber is obtained by spinning a viscous solution containing an aluminum compound (alumina sol, aluminum salt, etc.), a silicon compound (silica sol, ethyl silicate, etc.), and an organic polymer (polyethylene oxide, polyvinyl alcohol, etc.). is produced by calcination in air at a temperature below the temperature at which reflections of α-alumina are visible in the X-ray structure. Alternatively, it can be produced by immersing organic fibers in a solution containing an aluminum compound and a silicon compound and then firing them in air. The most preferable alumina fiber is
Manufactured by the method described in No. 13768. That is, this method involves spinning a solution containing polyaluminoxane and a silicon compound to obtain precursor fibers, which are then fired in air to produce alumina fibers. The polyaluminoxane used here has the general formula A polymer having a structural unit represented by, for example, Y consists of one or more of the following residues. In other words, alkyl groups such as methyl, ethyl, propyl, and butyl groups, alkoxy groups such as ethoxy, propoxy, and butoxy groups, carboxyl groups such as formyloxy and acetoxy groups, halogens such as fluorine and chlorine, and hydroxyl groups. , phenoxy group, etc. Particularly preferred are polyaluminoxanes that do not soften or melt at temperatures below 300° C. during the step of firing the alumina precursor fibers. Examples of such aluminoxane include polyisopropoxyaluminoxane, polyacetoxyaluminoxane, polybutoxyaluminoxane, and polypropionyloxyaluminoxane. These polyaluminoxanes are produced by partial hydrolysis of organoaluminum compounds such as triethylaluminum, triisopropylaluminum, tributylaluminum, aluminum triethoxide, and aluminum tributoxide, and by substituting the organic residues of the resulting polyaluminoxane with other suitable groups. It is known that it can be obtained by Polyaluminoxane is generally soluble in organic solvents such as ethyl ether, tetrahydrofuran, benzene, and toluene, and at an appropriate concentration forms a viscous liquid with excellent stringiness. On the other hand, as a compound containing silicon to be mixed with

Polyorganosine having the structural unit of [Formula] Roxane,

A polysilicate ester having the structural unit of [Formula] (R ₁ and R ₂ are organic atomic groups) is suitable, but an organosilane having the structure R _o SiX _4-o (X is OH, OR, etc.) is suitable. Yes, R
is an organic atomic group, n is an integer of 4 or less) silicate ester having a structure of Si (OR) ₄ (R is an organic atomic group),
Other silicon-containing compounds in general may be used. Furthermore, a small amount of lithium, beryllium,
Adding one or more compounds containing boron, sodium, magnesium, phosphorus, potassium, calcium, titanium, chromium, manganese, yttrium, zirconium, lanthanum, tungsten, etc. will improve the quality of the alumina fibers obtained. This is desirable for improving physical properties. For spinning from a mixed solution of a compound containing polyaluminoxane and silicon, so-called dry spinning is convenient, but other suitable spinning methods such as centrifugal spinning and blow spinning may be used. Spinning is carried out at room temperature, but the spinning solution can be heated if necessary. It is also desirable to control the atmosphere surrounding the spun fibers to obtain good results. Dry removal of the solvent contained in the fibers is not particularly necessary when the fibers are thin, but
This can also be done during or after spinning. The precursor fibers produced here are usually 1 to 600μ
It has an average diameter of However, it is not limited to this range. The alumina fiber precursor obtained in this way is formed into a fiber with a high concentration of alumina formed and uniformly continuous, which is extremely convenient for improving the physical properties of the alumina fiber after firing. It is something. The alumina fiber precursor obtained in this way is infusible to heat, and if it is fired as it is in an atmosphere containing oxygen such as air, it can be easily converted into alumina fiber without changing the fiber shape. Can be done. That is, if the precursor fiber is fired in an oxygen-containing atmosphere, for example, air, it will substantially change to an alumina fiber at about 700°C, with an
A transparent and strong alumina fiber can be obtained at ℃. In order to obtain these various alumina fibers, the precursor fibers may be fired in an inert atmosphere such as nitrogen or in vacuum, and then exposed to an oxygen-containing atmosphere to remove organic or carbonaceous substances. . Further, it is desirable to further sinter the obtained alumina fiber in a reducing atmosphere such as hydrogen in order to improve various physical properties of the alumina fiber. It is also desirable to maintain tension on the precursor fibers or alumina fibers during these firing steps in order to produce strong alumina fibers. In either case, the maximum firing temperature is set so that no reflection of α-alumina is seen in X-rays. In this way, by the method described in Japanese Patent Publication No. 51-13768, the fiber diameter is from 0.6 to 400 μ and the tensile strength is from 10 to
30t/cm ² , elastic modulus 1000 to 3000t/cm ² , in air
Alumina fibers are produced that are stable for long periods of time at temperatures above 1000°C, and such fibers are most suitable for use in the present invention. In order to further increase the reinforcing effect of the alumina fibers used in the present invention, it is also effective to coat the fiber surface with a metal such as nickel or titanium or with ceramics to control the reaction and bond between the fiber and the impregnated metal. . A fiber bundle of such alumina fibers has a melting point
By using a material impregnated with metal at 1700°C or less as a raw material and processing it into a cross or mat shape, high-performance FRM can be formed extremely easily. Here, a fiber bundle is a bundle of multiple fibers, and the number of fibers included in one bundle is not particularly important, but the present invention is particularly effective for bundles that usually consist of 20 or more fibers. Applicable. This is because, even if a bundle of several fibers is not impregnated with metal in advance, the matrix metal can penetrate into the gaps between the individual fibers during the FRM forming process. However, such bundles made of a small number of fibers are difficult to handle, and it is actually easier to form an FRM by applying the present invention to bundles of 20 or more fibers. Next, there is no particular restriction on the upper limit of the number of fibers included in one bundle, but according to the results of the study by the present inventors, if the cross-sectional area of the bundle exceeds approximately 0.2 cm ² , metal may be added to the bundle. Impregnated materials have problems such as lack of flexibility. Therefore, the number of fibers is preferably such that the cross-sectional area of one bundle is 0.2 cm ² or less. The cross-sectional shape of the fiber bundle is not particularly limited, and may be circular, elliptical, rectangular, irregular, or the like. When a single bundle contains a large number of fibers, forming the bundle into a flat plate has the advantage that the resulting material is more flexible and can be easily filled into the mold during FRM molding. It may have. Also, the length of the fiber bundle is 50% of the diameter of the single fiber.
If it is more than double that, it becomes a useful material. Furthermore, the present invention can be effectively applied not only to fiber bundles in which a plurality of fibers are aligned, but also to fiber bundles in which these fibers are twisted or knitted. Next, a cloth is one in which fibers or fiber bundles are woven into a sheet shape or three-dimensional shape using plain weave, satin weave, etc., and there is no lower limit to the number of fibers included in the fiber bundle in this case. Matsut is a collection of fibers or fiber bundles that are not woven into a plate shape, and are short fibers that are randomly entangled, long fibers that are twisted together in a spiral, or long fibers that are parallel to each other in one direction. This includes various structures such as those arranged in a sheet shape. It may be preferable that these cloths and mats have a shape that matches the FRM molded body to be finally obtained. For example, suitable materials for forming tubular FRM include cloth or pine cylindrical and impregnated with metal. In some cases, it may be useful to have a cross or pine in the form of a ribbon whose width is smaller than its length.
Furthermore, it may be more useful to have a structure in which two or more types of cloth, mat, and fiber bundles are laminated. The shapes of these various materials and the combination of materials are determined by what kind of FRM is required. Furthermore, in addition to the above-mentioned alumina fibers, it may be preferable to mix a small amount of other types of fibers, such as alumina whiskers, carbon fibers, boron fibers, ceramic fibers, and metal fibers, as reinforcing fibers. Further, in the present invention, impregnation refers to a state in which metal penetrates into the gaps between individual fibers of the fiber bundle, but in this case, it is not necessary that the gaps between the individual fibers are completely filled with metal. Even if there are voids between the fibers of the material, these voids are often filled with metal during the FRM forming process, and compared to when FRM is formed from fiber bundles that are not pre-impregnated with metal, there are far fewer voids in the formed object. few. Further, even if there are voids between the fibers of the material, they can be used extremely effectively for the purpose of controlling the distribution state of reinforcing fibers in the FRM molded body, which will be described later. However, generally speaking, the amount of voids in the material is preferably 60% or less by volume. Furthermore, the metal used in the present invention has a melting point of
Beryllium, magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, titanium, manganese, iron, cobalt, nickel, palladium, copper, which is below 1700℃
Single metals such as silver, gold, zinc, cadmium, aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, bismuth, selenium, tellurium, copper-zinc alloys such as brass, copper-tin alloys such as bronze , copper-tin-phosphorus alloys, aluminum-magnesium-based alloys such as duralumin, aluminum-magnesium-copper-based alloys, and many other types such as aluminum-copper-based, aluminum-silicon-based, nickel-aluminum-based, nickel-aluminum-copper-based, etc. Alloys are mentioned. It is also possible to use a mixture of these metals with several percent of one or more other elements to improve wettability with the alumina fibers. Which of these metals to use depends on the intended use of the material. For example, when molding a lightweight FRM with a matrix of light metal, it is generally desirable that the material metal is also a light metal, and when molding a high-temperature heat-resistant FRM with a matrix of iron or the like, the material metal It is also desirable that the material has excellent heat resistance. Fiber bundles of alumina fibers impregnated with metal
Although various methods can be considered to produce the material for FRM, the present inventors have found that a method of immersing a fiber bundle in molten metal and drawing it out is simple and effective. In this case, the temperature of the molten metal should be at least the melting point of the metal, but it is usually 50℃ or higher, or 300℃ above the melting point.
The following is desirable from the viewpoint of ease of temperature control to keep the metal in a molten state and prevention of unnecessary deterioration of fiber properties. The time for immersing the fiber bundle in the molten metal varies depending on the number of fibers in the fiber bundle, but 20 minutes or less is usually sufficient. Additionally, applying pressure to the molten metal while immersing fiber bundles in the molten metal to make it easier for the metal to penetrate into the gaps between the fibers is extremely effective in shortening the immersion time and reducing voids in the material. be. This can be done by mechanically applying pressure using a roll, press, etc., or by immersing the metal in molten metal in an autoclave and applying gas pressure. The pressure in this case depends on the size of the fiber gap, but it is effective if the pressure is 5 kg/cm ² or more. When pulling out the immersed fiber bundle from the molten metal, it is squeezed through an appropriate squeeze at a temperature above the melting point of the metal.
Controlling the metal content in the material and reducing voids are also effective. The optimum amount of metal in the material is determined by what kind of FRM is required and what molding method is used.
When an extremely high-performance FRM with a high fiber content or an FRM with localized reinforcing fibers is required, it is desirable that the metal content of the material is low. When FRM with low fiber content and high metal content is required, the metal content of the material may often be high. However, even if a material with a low metal content is used, it is possible to form an FRM with a high metal content by adding matrix metal in the FRM forming process, and conversely, even if a material with a high metal content is used, an FRM with a high metal content can be formed. By melting and squeezing out some of the metal during the process, it is possible to form FRM with a low metal content. The metal content in the material is usually preferably from 10% by volume to 95% by volume. The method of impregnating a bundle of alumina fibers with molten metal according to the present invention can be carried out either batchwise or continuously. Although the process can be carried out in air, depending on the metal, it may be preferable to carry out the process in an inert atmosphere, other special atmosphere, or vacuum. The present invention is a method characterized by using a material obtained by impregnating fiber bundles with metal using various methods as a raw material, and processing this into a cloth or mat shape to obtain a material. FRM an appropriate amount of the material thus obtained.
An FRM molded body can be obtained by placing it in a mold and hot pressing it as it is, by melting and pressurizing impregnated metal to squeeze out the metal, or by newly casting molten metal. The present invention produces novel effects as described below. First, the fiber used in the FRM material according to the present invention is an alumina fiber that is extremely suitable for reinforcing metals, and the FRM obtained from this material has extremely excellent mechanical performance, high temperature resistance, and corrosion resistance. . Next, when manufacturing an FRM molded body from an appropriate amount of this material, since each material is pre-impregnated with metal, there are fewer voids in the gaps between the materials and fibers, and for this reason, a high-performance FRM molded body is produced. That's what you get. Furthermore, since the fiber bundles, cloths, and mats are impregnated with metal and tied together, they can be molded anywhere in the FRM mold, and can be deformed by arbitrarily controlling the fiber arrangement direction. By arbitrarily controlling the fiber distribution in the molded article, it is possible to easily produce a molded article having the performance as designed. EXAMPLES The present invention will be explained below using Examples, but the present invention is not limited thereto. Example 1 Fiber diameter 10μm, tensile strength 240Kg/mm ² , tensile modulus 25t/mm ² , SiO ₂ 15% by weight and Al ₂ O ₃ 85% by weight
Continuous alumina fibers with a γ-alumina structure are coated with nickel to a thickness of 100 Å by chemical plating, and a bundle of 200 fibers is continuously immersed in a 750°C molten aluminum (99.7% purity) bath for 2 minutes. The material was passed through the cloth and squeezed with a boron nitride roller at the bath outlet to obtain a material with a cross section of 1 x 0.3 mm and a metal content of 50% by volume, which was woven into a plain weave to obtain a cloth weighing 600 g per 1 m ² . Five layers of this were placed in each flange part of the eye beam type, and a 1 m long FRM eye beam with an aluminum matrix was prototyped by casting. The fibers could be localized only in the flange, and the bending stiffness was double that of aluminum alone without fibers. Example 2 The continuous alumina fibers used in Example 1 were made into a bundle of 1000 fibers, and the bundle was wound around a carbon spool. This was immersed in molten aluminum at 750℃ in a crucible placed in an autoclave, and 10Kg/cm ²
The above pressure was applied for 80 seconds. While maintaining the temperature at 750°C, the pressure was returned to normal and the aluminum-impregnated fiber bundle was pulled out from the spool. The material was then passed through an alumina die heated above the melting point of aluminum to remove excess aluminum, yielding a material with a metal content of 50% by volume and a cross-sectional area of approximately 0.002 cm ² . Using this aluminum-impregnated alumina fiber bundle, a satin woven cloth having a weight of about 400 g per 1 m ² was obtained. This satin woven cloth was cut into pieces of 20 mm wide and 100 mm long, and 15 pieces were stacked and placed in a mold with a width of 20 mm, a thickness of 10 mm, and a length of 100 mm, and molten aluminum was poured into it to achieve a fiber volume fraction of 20%.
Obtained FRM board material. No deviation of the alumina fiber bundles in the FRM was observed. As a comparative example, a satin cloth having a weight of about 210 g per m ² was obtained from the same alumina fibers as used in Example 1. This was cut into the same dimensions as in Example 7, laminated in the same manner, and operated in the same manner, but the impregnation of aluminum between the fibers was insufficient. The same operation as above was performed on the satin woven cloth obtained in the above comparative example under pressure. Although the impregnation of aluminum between the fibers was good, the fabric was pressed to one side by the pressure during impregnation with aluminum, and a uniform fiber distribution could not be obtained.

Claims (1)

[Claims] 1 Al ₂ O ₃ 72% by weight or more in its components,
Alumina made by impregnating a bundle of alumina fibers containing 28% by weight or less of SiO ₂ and showing substantially no reflection of a-Al ₂ O ₃ in the X-ray structure with a metal whose melting point is 1700°C or less. A method for producing a material for alumina fiber-reinforced metal composite material, which is characterized by using a material for alumina fiber-reinforced metal composite material as a raw material and processing it into a cross or mat shape.