JPH1129831A - Preform for metal matrix composite and method for producing the same - Google Patents

Abstract

(57) [PROBLEMS] To use a ceramic hollow sphere, inorganic fibers and ceramic particles in combination to reduce the amount of expensive inorganic fibers used and to easily penetrate a metal matrix into voids. To provide a preform for a composite material and a method for producing the same. A ceramic hollow sphere having an average particle diameter of 20 to 150 µm, an average fiber diameter of 1 to 10 µm and an average fiber length of 10 to 10 µm.
It is composed of inorganic fibers of 200 μm, ceramic particles having an average particle diameter of 1 to 10 μm, and a binder for binding them, and has a volume fraction (excluding voids inside the ceramic hollow sphere) of 10 μm.
５０50% preform.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preform of a metal-based composite material in which a metal is used as a matrix and reinforced with inorganic fibers and ceramic particles, and a method for producing the same.

[0002]

2. Description of the Related Art Carbon fibers, ceramic fibers such as alumina fibers, ceramic whisker heat-resistant fibers such as silicon carbide, or ceramic particles such as whiskers, alumina and mullite are embedded and reinforced in a material metal such as steel or an aluminum alloy. The material has high physical properties that far exceed the physical properties, such as mechanical strength and abrasion resistance, of the material metal. Such a metal-based composite material reinforced with inorganic fibers, whiskers, ceramic particles, and the like has attracted attention in fields requiring lightweight and high-physical materials such as aircraft and automobiles.

[0003] The metal-based composite material is prepared by previously disposing a molded article (preform) composed of inorganic fibers, whiskers, ceramic particles and the like in a mold such as a die cast casting machine. It is obtained by a method of pouring and impregnating a molten metal of a matrix metal into a preform.

[0004] As such a preform, one made of ceramic particles and alumina short fibers is used as a fiber reinforced composite material without deformation, cracking, bending, poor infiltration or the like of the preform. It has been proposed to be superior in quality (Japanese Patent Application Laid-Open No. 9-14405). Further, it has been proposed that a sound composite material which does not cause shrinkage or cracking of a molded article can be obtained by subjecting a reinforcing fiber having a specific fiber diameter and particles having an average particle diameter of 10 to 50 μm to suction dehydration molding (see, for example, Japanese Patent Application Laid-Open Publication No. H11-163873). JP-A-3-44432).

[0005]

However, preforms mainly composed of ceramic fibers and whiskers are expensive, and cannot be said to be widely used. In addition, preforms mainly composed of ceramic particles have lower strength than those mainly composed of ceramic fibers and whiskers.If the volume fraction of the preform is increased to secure the strength of the preform, a metal matrix is formed in the voids. There is a problem that it is difficult to penetrate.

Accordingly, an object of the present invention is to provide a ceramic hollow sphere, inorganic fibers, and ceramic particles in combination.
An object of the present invention is to provide a preform of a metal-based composite material that can reduce the amount of expensive inorganic fibers used and easily penetrate a metal matrix into voids, and a method for producing the same.

[0007]

Under such circumstances, the present inventors have conducted intensive studies and, as a result, completed the present invention. That is, the present invention has an average particle size of 20 to 150 μm.
Ceramic hollow spheres, inorganic fibers having an average fiber diameter of 1 to 10 μm and an average fiber length of 10 to 200 μm,
An object of the present invention is to provide a preform for a metal matrix composite comprising ceramic particles of 10 μm and a binder for bonding the ceramic particles. Further, the present invention provides a method for producing a metal base, comprising extruding a plastic mixture obtained by adding water to a mixture of ceramic hollow spheres, inorganic fibers, ceramic particles, an inorganic binder and an organic binder and mixing, drying and firing. A method for producing a preform for a composite material is provided.

[0008]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, the ceramic hollow spheres have an average particle size of 20 to 150 .mu.m. Also,
The diameter of the closed pores of the hollow sphere is preferably in the range of 10 to 120 μm. The hollow sphere is made of a metal matrix composite (hereinafter, referred to as “MM”) as described later.
C ") at 250 to 1000 kg / cm ²
It is preferable that the metal matrix be infiltrated into the closed pores by a certain casting pressure, and in order to realize this, it is preferable that the outer shell of the hollow sphere has minute pores and defects. The minute pores and defects in the outer shell of such hollow spheres are produced during the production of the hollow spheres, during kneading of a plastic mixture as described below,
It is formed spontaneously or intentionally at the time of firing a molded body or at the time of preheating of a preform at the time of casting. Further, the infiltration of the metal matrix into the inside of the closed pores may be caused by breaking of the hollow ceramic sphere due to casting pressure. Specific examples of such ceramic hollow spheres include glass balloons, alumina balloons, shirasu balloons, and the like, and one or more of these can be used in combination. Also,
The bulk specific gravity of the hollow sphere is 0.1 to 0.8, preferably 0.1 to 0.8.
2 to 0.6.

The inorganic fibers have an average fiber diameter of 1 to 10 μm and an average fiber length of 10 to 200 μm. As the inorganic fiber, for example, alumina fiber, alumina silica fiber,
Ceramic fiber, mullite fiber, asbestos, rock wool,
Natural or synthetic inorganic fibers such as carbon fibers; whisker fibers such as silicon carbide whiskers, silicon nitride whiskers, aluminum borate whiskers, and potassium titanate whisker; and the like, and one or a combination of these may be used. it can.

The ceramic particles have an average particle size of 1 to 10 μm.
belongs to. Examples of the ceramic particles include carbon, graphite powder, Al, Si, Ti, Zr, Mg, B, and Fe.
And the like. Specific examples thereof include alumina powder, mullite powder, cordierite powder, silica-alumina powder, silica powder and the like, and these are used alone or in combination of two or more. can do.

The binder for binding the above-mentioned ceramic hollow spheres, inorganic fibers and ceramic particles is not particularly limited, as long as they are bonded by heat treatment to obtain the necessary strength as a preform for a metal matrix composite. I just need.
Specific examples include a powdery binder such as a frit; and an inorganic binder such as a sol-like binder such as colloidal silica and alumina sol, and one or two of these can be used in combination. The combination may be determined in consideration of the chemical and physical properties such as the composition, melting point, reactivity, specific surface area, and particle size of the ceramic hollow spheres, inorganic fibers, and ceramic particles used. Further, in the present invention, an organic binder can be blended. Examples of such an organic binder include methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, polyvinyl alcohol, phenolic resin, polyacrylate, and sodium polyacrylate.

[0012] The preform for a metal matrix composite of the present invention comprises:
Volume fraction (excluding voids inside ceramic hollow sphere) is 1
The content of the ceramic hollow spheres, the inorganic fibers, and the ceramic particles in the preform is preferably 20% by weight or more, and 10 to 50%.
It is preferable that the content is not more than 60% by weight and 40% by weight.
The ceramic hollow spheres are 20 to 80% by weight, the inorganic fibers are 10 to 60% by weight, and the ceramic particles are
More preferably, it is 0 to 40% by weight. When the volume fraction of the preform is smaller than the above range, the strength tends to be insufficient, and when the volume fraction is larger than the above range, the metal matrix does not easily penetrate into the voids. If the ratio of the ceramic hollow spheres is small, it is necessary to increase the volume fraction in order to secure the strength of the preform, and the metal matrix is less likely to penetrate into the voids. If the ratio of the ceramic hollow spheres is too large, the wear resistance of the MMC will decrease.
If the proportion of the inorganic fibers is less than the above range, the spalling resistance of the preform decreases, and if the proportion of the inorganic fibers is too large, the metal matrix penetrates into the voids when the volume fraction of the preform is increased. It is easy to be difficult.
If the ratio of the ceramic particles is larger than the above range, it is necessary to increase the volume fraction in order to secure the strength of the preform, and the metal matrix is less likely to permeate into the voids. If the ratio of the ceramic particles is too small, MM
The wear resistance of C decreases.

Preferred combinations of the above-mentioned ceramic hollow spheres, inorganic fibers and ceramic particles differ depending on the use and physical properties of the MMC, but include glass balloons, alumina-silica short fibers and mullite powder; glass balloons, silicon carbide whiskers and alumina powder; Combinations of silica powders are particularly preferred.

The preform for a metal-based composite material of the present invention comprises:
It can be obtained by the following production method. That is, ceramic hollow spheres, inorganic fibers, ceramic particles and an inorganic binder and an organic binder are mixed by adding water as a molding aid,
Make a homogeneous plastic mixture. The resulting plastic mixture is
It is formed into a predetermined shape according to the use of the product, such as a rod, a cylinder, a ring, and a disk. Such a molding method is not particularly limited, and may be selected according to the shape of the product, and examples thereof include an extrusion molding method, an injection molding method, and a press molding method, and the like. For a metal matrix composite used as a cylinder block, As a method for forming a cylindrical preform such as a preform, an extrusion molding method is preferable. Further, since the density difference between the ceramic hollow spheres and the ceramic particles is large, it is difficult to obtain a uniform preform by dehydration molding of the slurry. The obtained molded body is dried at room temperature or under heating to cure the organic binder and remove moisture. Next, baking is performed to obtain the preform of the present invention. As the firing temperature,
What is necessary is just a temperature range in which the strength of the inorganic binder is exhibited.

Next, the preform for a metal matrix composite material obtained by the above method is placed in a mold of a casting machine such as squeeze casting or die casting, and a molten metal of a matrix metal such as an aluminum alloy is placed in the preform. MMC may be obtained by a method of pouring and impregnating. Also, MM
In C, the volume fraction of the preform is preferably in the range of 10 to 50%. The casting conditions by die casting are not particularly limited, but the preform preheating temperature is from room temperature to 600 ° C, and the melt temperature is from 600 ° C to 800 ° C.
C, mold temperature 150-300 ° C, injection temperature 0.1-1.0m / sec, casting pressure 250-1000kg
/ cm ² is preferable. In the MMC manufactured by such a method, a metal matrix is infiltrated into pores of the ceramic hollow spheres existing in the preform, and a desired strength is given.

The use of the MMC includes, for example, parts for automobiles and aircraft, which are required to be lightweight and have high physical properties.

[0017]

According to the preform for a metal matrix composite of the present invention, the volume fraction can be set in a wide range, and when the metal matrix is injected, the filling rate is high and the quality of M is high.
MC is obtained. Further, it can be molded by a method having high productivity such as extrusion molding, and is inexpensive because the fiber content can be reduced.

[0018]

【Example】

Example 1 100 parts by weight of a glass balloon having an average particle diameter of 50 μm and an average independent pore diameter of 47 μm, 20 parts by weight of alumina silica short fiber having an average fiber diameter of 3 μm and an average fiber length of 100 μm, and 80 parts by weight of mullite powder having an average particle diameter of 10 μm Then, as a binder, 50 parts by weight of a glass frit having a softening point of 600 ° C., 15 parts by weight of methylcellulose, and 900 parts by weight of water were kneaded to obtain a plastic mixture. After extruding the mixture into a cylindrical shape, the mixture was dried at 105 ° C. to obtain a cured molded product. This molded product was baked at a temperature of 900 ° C. for 1 hour to soften the frit and bond the reinforcing material and the glass balloon. The preform thus obtained had a density of 0.8 g / cm ² and a volume fraction (excluding voids inside the glass balloon) of 18%. Next, after preheating the preform to 600 ° C., it is set in a mold,
To this, an 800 ° C aluminum alloy (JIS standard ADC1
2) The molten metal was poured, and pressurized at a pressure of 1000 kg / cm ² , and held until the molten metal was completely solidified to obtain an MMC. The MMC was cut, and the impregnation state of the aluminum alloy inside the glass balloon was evaluated with a metallographic optical microscope photograph. The results are shown in FIG.

From FIG. 1, it was found that the aluminum alloy was uniformly impregnated into the inside of the glass balloon and the fine communicating voids without the binder between the fibers and the particles. In addition, the MMC exhibited excellent wear resistance.

[Brief description of the drawings]

FIG. 1 shows a photomicrograph (× 1750) of an optical microscope metallographic structure of the aluminum-based composite material obtained in Example 1.

[Explanation of symbols]

 A Aluminum alloy B Glass balloon C Mullite particles D Alumina silica fiber

Claims (4)

[Claims] 1. A ceramic hollow sphere having an average particle diameter of 20 to 150 μm, an average fiber diameter of 1 to 10 μm and an average fiber length of 10 to 10 μm.
A preform for a metal-based composite material comprising inorganic fibers of 200 μm, ceramic particles having an average particle size of 1 to 10 μm, and a binder for binding these. 2. The preform has a volume fraction (excluding voids inside the ceramic hollow spheres) of 10 to 50%, and
The metal matrix composite material preform according to claim 1, wherein the ratio of the ceramic hollow spheres, the inorganic fibers and the ceramic particles in the preform is 20% by weight or more, 10 to 60% by weight and 40% by weight, respectively. Reform. 3. The preform for a metal-based composite according to claim 1, wherein said hollow ceramic spheres are glass balloons, and said inorganic fibers are short alumina silica fibers. 4. A plastic mixture obtained by adding and mixing water to a mixture of ceramic hollow spheres, inorganic fibers, ceramic particles, an inorganic binder and an organic binder, extruding, drying and firing. The method for producing a preform for a metal-based composite material according to claim 1, 2 or 3.