JP2024106304A - High-strength metal matrix composite and method for producing the same - Google Patents

Abstract

[Problem] To provide an aluminum alloy-based composite having high strength yet good processability, which could not be realized by conventional manufacturing techniques, and which is economically valuable because it can reduce manufacturing costs, and a manufacturing method for said composite. [Solution] To provide a high-strength metal-based composite and a manufacturing method for said composite, which are formed by impregnating and filling molten aluminum or aluminum alloy into a porous filled body or molded body (preform) made of a mixed powder obtained by adding one or more types of aluminum/aluminum alloy powder selected from the group consisting of aluminum powder and aluminum alloy powder having an average particle size of 10 μm to 300 μm to one or more types of fine powder selected from the group consisting of metal powder and ceramic powder having an average particle size of 0.3 μm to 8 μm, and the filling rate of the fine powder is 10 vol % to 50 vol %, and the bending strength is 500 MPa to 800 MPa, and a manufacturing method for said metal-based composite. [Selected Figure] None

Description

The present invention relates to a metal-based composite obtained by combining a ceramic powder and/or a metal powder as a fine powder that functions as a reinforcing material with a molten aluminum or aluminum alloy as a matrix material. More specifically, the present invention relates to a technology for providing a high-strength metal-based composite with high strength and excellent workability, which is realized by using a mixed powder that combines the fine powder with an aluminum powder or an aluminum alloy powder (hereinafter also referred to as "powder of aluminum alloy or the like") having a larger particle size than the fine powder, and a method for producing the same.

In recent years, materials in which ceramics are composited with aluminum or aluminum alloys (so-called MMCs), CFRP (Carbon Fiber Reinforced Plastics) in which carbon fibers are composited with resin, CMCs (Ceramic Matrix Composites) in which ceramics are composited with ceramic molded bodies by CVD or the like, and composite materials in which aluminum is composited with other metal powders, etc. have been developed and put to practical use. Among these, MMCs that combine the properties of two different inorganic materials and use aluminum or aluminum alloys (hereinafter, collectively referred to as aluminum alloys, etc.) as a matrix material are being developed as described below, and have also been put to practical use, partly because they can reduce the weight of the material. For example, they are widely used in the industrial world as machine parts and electronic substrates that have desired properties such as light weight, high strength, high rigidity, and high heat resistance, as semiconductor liquid crystal manufacturing equipment, robot arms, gas turbine materials, power devices, etc.

Patent Document 1 proposes a method of manufacturing an intermediate molded body (preform) by adding ceramic powder and an inorganic binder to it and hardening it, and then high-pressure press-infiltrating molten metal such as an aluminum alloy into the pores other than the powder to form a composite. According to this aluminum high-pressure impregnation method, aluminum alloy-based composite materials (MMCs) in which ceramic powder is uniformly distributed can be easily produced by forcibly impregnating a unique intermediate molded body (preform) with molten metal such as an aluminum alloy at high pressure. The above-mentioned manufacturing method can also be applied to aluminum alloy-based composite materials (MMCs) that use a powder filler made of ceramic powder as the material to be composited.

Patent Document 2 proposes a method in which a unique intermediate molded body (preform) in which Mg powder is added to ceramic powder is placed in a nitrogen atmosphere, and aluminum alloy is infiltrated into it without pressure to form a composite. The principle of this method is to improve the wettability of ceramics and Al alloys in an Mg and nitrogen atmosphere, and promote the so-called capillary phenomenon to infiltrate molten aluminum alloys into the voids of the preform. According to this manufacturing method, the ceramic filling rate can be increased by increasing the ceramic filling rate and reducing the voids, and as a result, aluminum alloy-based composite materials (MMCs) of ceramics and aluminum alloys, etc., with high physical properties such as Young's modulus, thermal conductivity, and thermal expansion coefficient can be manufactured. In addition, according to this manufacturing method, by using a preform, aluminum alloys, etc. can be infiltrated while maintaining the shape of the preform, and an MMC composite can be manufactured with a near-net shape close to the product shape.

In addition to the above-mentioned manufacturing method, aluminum alloy-based composite materials (MMC) can also be manufactured by the following casting method. In this method, ceramic powder such as silicon carbide or alumina is added to a molten aluminum alloy or the like and stirred at high speed to produce a molten aluminum alloy or the like containing the ceramic powder, or a composite impregnated with aluminum alloy or the like in a mixed powder of ceramic powder and Mg is mixed and dissolved uniformly in a nitrogen atmosphere without pressure to produce a molten metal for casting, which is then cast into a conventional mold such as a casting sand mold, metal mold, or lost wax mold to produce a composite of ceramic and aluminum alloy.

Furthermore, aluminum alloy-based composite materials (MMC) can also be manufactured by a manufacturing method that utilizes the HIP (Hot Isostatic Pressing) method described below. Specifically, the so-called Supermex method is known, in which a ceramic powder is mechanically alloyed coated with an aluminum alloy or the like to produce a powder molded body, which is then sintered and then subjected to high-pressure isostatic pressing by HIP to produce a composite of the ceramic powder and the aluminum alloy or the like. A similar method is known in which a composite deposit is produced by spraying and depositing a molten metal such as an aluminum alloy mixed with ceramic powder, and since this deposit contains pores, the pores are removed by HIP treatment to produce a composite.

Patent No. 6837685 Patent No. 6984926

However, the inventors recognized that the above-mentioned conventional manufacturing methods for aluminum alloy-based composite materials (MMCs) have the problems listed below, and that there is room for improvement to create aluminum alloy-based composite materials with superior functionality.

In the high-pressure impregnation method described above, in which molten metal such as an aluminum alloy is impregnated at high pressure, the volume percentage of the powder itself in the powder packing or preform is determined by the properties of the powder, and only those with a volume ratio of more than 50 volume% could be produced. In the high-pressure impregnation method, since the molten metal such as an aluminum alloy is impregnated into the gap pores of the powder packing or preform, it is difficult to reduce the volume of metal powder or ceramic powder and increase the volume of aluminum alloy. For this reason, it was difficult to produce a composite with good processability and a large amount of impregnation of aluminum alloy, etc. by the high-pressure impregnation method. In other words, the method of impregnating molten metal such as an aluminum alloy at high pressure could not produce a composite with a volume ratio of ceramic powder or metal powder of 50% or less and good processability. In addition, since metal powder or ceramic powder of about 10 μm or more is usually used as a reinforcing material to be compounded, the load on the processing tool is large, and there was a problem that the aluminum alloy matrix composite material (MMC) obtained by the above-mentioned high-pressure impregnation method has poor processability.

In the previously described method of infiltrating molten aluminum alloy or the like into the voids of a preform without applying pressure to form a composite, powder is molded and the voids in the preform are impregnated with molten aluminum alloy or the like, but it was not possible to produce a preform with voids exceeding 50% by volume, i.e., an aluminum alloy-based composite material with a powder filling rate of 50% by volume or less.

The casting method described above also has the following problems. First, in casting methods, the flowability of the molten metal deteriorates as the content of ceramic powder in the aluminum alloy increases, so the upper limit of the ceramic content is generally considered to be about 30% by volume. On the other hand, the particle size of ceramic powder such as SiC powder used in casting methods must be large, at 15 μm or more, to maintain castability. For this reason, even though the SiC volume percentage is as low as 30% or less, the workability is low, and the resulting aluminum alloy-based composite material can only be processed with diamond tools, resulting in a material with poor workability. Another problem is that the molten metal is prone to entraining air during casting, making it difficult to obtain a composite material without defects.

In addition, the manufacturing method using the HIP method described above uses metal powder as the main metallic raw material, so the surface of the metal powder is easily oxidized during the manufacturing process, making it difficult to obtain the strength of the composite, and the complex HIP process is required, which poses major practical issues in that it is expensive.

The object of the present invention is therefore to provide an aluminum alloy-based composite that has high strength yet good workability, and that can reduce manufacturing costs, and is of great practical value in terms of industrial applicability, something that could not be achieved with conventional manufacturing techniques, and a new technology for the manufacturing method of said composite.

The above object can be achieved by the present invention, which provides a high-strength metal matrix composite as follows: In the present invention, the "average particle size" refers to the particle size (median size) at an integrated value of 50% in a particle size distribution determined by a laser diffraction/scattering method.
[1] A composite obtained by impregnating and filling molten aluminum or an aluminum alloy into a porous filled body or molded body (preform) made of a mixed powder obtained by adding one or more types of aluminum/aluminum alloy powder selected from the group consisting of aluminum powder and aluminum alloy powder having an average particle size of 10 μm or more and 300 μm or less to one or more types of fine powder selected from the group consisting of metal powder and ceramic powder having an average particle size of 0.3 μm or more and 8 μm or less, and the composite has a filling rate of the fine powder of 10 vol.% or more and 50 vol.% or less, and a bending strength of 500 MPa or more and 800 MPa or less.

Preferred embodiments of the high-strength metal-based composite are as follows.
[2] The high-strength metal matrix composite according to the above [1], wherein the metal powder constituting the fine powder of the mixed powder is any one selected from the group consisting of silicon powder, iron powder, stainless steel powder, copper powder, and titanium powder, the ceramic powder is any one selected from the group consisting of alumina powder, silica powder, aluminum borate powder, silicon carbide powder, silicon nitride powder, and aluminum nitride powder, and further, the blending ratio of the fine powder to the aluminum/aluminum alloy powder constituting the mixed powder is 10:90 to 90:10.
[3] The high-strength metal matrix composite according to the above [1] or [2], wherein the mixed powder further comprises one or more binders selected from the group consisting of silica-based binders and alumina-based organic/inorganic binders, the binder being added externally in an amount of 0.5% or more and 10% or less by mass.

As another embodiment, the present invention provides the following method for producing a high-strength metal matrix composite.
[4] A porous packed body or molded body (preform) is obtained using a mixed powder obtained by adding one or more aluminum/aluminum alloy powders selected from the group consisting of aluminum powders and aluminum alloy powders having an average particle size of 10 μm or more and 300 μm or less to one or more fine powders selected from the group consisting of metal powders and ceramic powders having an average particle size of 0.3 μm or more and 8 μm or less, and then subjecting the resulting packed body or molded body (preform) to
Molten aluminum or aluminum alloy is impregnated and filled at a high pressure of 20 MPa or more and 200 MPa or less to form a composite.
A method for producing a high-strength metal matrix composite, comprising the steps of: obtaining a metal matrix composite having a filling rate of the fine powder of 10 volume % or more and 50 volume % or less, and a bending strength of 500 MPa or more and 800 MPa or less.

[5] A mixed powder is obtained by adding one or more aluminum/aluminum alloy powders selected from the group consisting of aluminum powders and aluminum alloy powders having an average particle size of 10 μm to 300 μm to one or more fine powders selected from the group consisting of metal powders and ceramic powders having an average particle size of 0.3 μm to 8 μm, and further adding magnesium powder in a range of 0.5 parts by mass to 10 parts by mass to 100 parts by mass of the mixed powder to obtain a porous filled body or molded body (preform), and then subjecting the obtained filled body or molded body (preform) to
The material is impregnated and filled with molten aluminum or aluminum alloy without pressure to form a composite.
A method for producing a high-strength metal matrix composite, comprising the steps of: obtaining a metal matrix composite having a filling rate of the fine powder of 10 volume % or more and 50 volume % or less, and a bending strength of 500 MPa or more and 800 MPa or less.

A preferred embodiment of the method for producing a high-strength metal matrix composite according to the above item [4] or [5] is as follows.
[6] The method for producing a high-strength metal matrix composite according to the above [4] or [5], wherein the metal powder constituting the fine powder of the mixed powder is any one selected from the group consisting of silicon powder, iron powder, stainless steel powder, copper powder and titanium powder, the ceramic powder is any one selected from the group consisting of alumina powder, silica powder, aluminum borate powder, silicon carbide powder, silicon nitride powder and aluminum nitride powder, and further, the blending ratio of the fine powder and the aluminum/aluminum alloy powder constituting the mixed powder is 10:90 to 90:10.
[7] The method for producing a high-strength metal matrix composite according to any one of the above [4] to [6], wherein the mixed powder further contains one or more binders selected from the group consisting of silica-based binders and alumina-based organic/inorganic binders, the binders being added externally in an amount of 0.5% or more and 10% or less by mass.

According to the present invention, it is possible to provide a metal matrix composite product with high practical value that could not be realized by conventional manufacturing techniques, in which the volume percentage of the reinforcing material made of metal powder and/or ceramic powder is 50 volume % or less, the bending strength is high at 500 MPa or more, and the product also exhibits good processability. Furthermore, a method for manufacturing a metal matrix composite that can produce the above-mentioned metal matrix composite with excellent properties in a simple manner and is extremely useful in terms of practicality with reduced manufacturing costs is provided.

FIG. 2 is a schematic diagram for illustrating a method for producing a high-strength metal matrix composite according to the present invention without applying pressure.

The following describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments.

As mentioned above, in the past, a method for manufacturing a composite of a reinforcing material made of a metal powder and/or ceramic powder and a matrix material such as an aluminum alloy has been adopted in which a molten aluminum alloy or the like is impregnated into a packed body or molded body (preform) of the reinforcing material by high-pressure impregnation or non-pressure infiltration. However, according to the study by the present inventors, in the above-mentioned manufacturing method, for example, when manufacturing a preform with a filling rate of metal powder or ceramic powder of 50 volume % or less, it is difficult to maintain the shape because the particle filling rate is low, and it is difficult to manufacture a preform that can withstand the high-pressure impregnation method or the non-pressure infiltration method. In other words, in the conventional technology, it is difficult to manufacture a porous preform with voids of 50 volume % or more, so that a metal-based composite with a matrix material such as an aluminum alloy of more than 50 volume % could not be manufactured by high-pressure impregnation or non-pressure infiltration. In the above, a molded body (preform) has been used as an example, but unlike molded bodies (preforms), filled bodies made by packing raw material powder into a metal box or the like and vibrating and molding them, generally have a volume ratio of 50% or more, and so have the same problem of poor workability as composites made with molded bodies (preforms). Hereinafter, filled bodies or molded bodies (preforms) made of metal powder or ceramic powder will also be referred to as "preforms, etc.".

The present inventors have conducted intensive research into the difficulty of producing preforms and the like made of metal powders or ceramic powders with a filling rate of 50 volume % or less in the above-mentioned conventional technology, and have found that the problem can be solved by configuring as follows. Specifically, the above problem can be solved by configuring a preform and the like made of metal powders or ceramic powders that are impregnated and filled with molten metal such as an aluminum alloy, which constitutes a metal-based composite, as follows. First, for the above purpose, it is effective to use fine materials with an average particle size of 0.3 μm or more and 8 μm or less for the metal powders or ceramic powders used to form the preforms and the like. Then, it has been found that the above problem can be solved by using a mixed powder in which the above-mentioned fine metal powders and/or ceramic powders are added with powders of aluminum alloys or the like with an average particle size of 10 μm or more and 300 μm or less, and producing a preform and the like made of the mixed powder. As mentioned above, the "average particle size" defined in the present invention is the particle size at 50% of the cumulative value in the particle size distribution obtained by the laser diffraction/scattering method, that is, the so-called 50% median diameter.

Specifically, the present invention was arrived at by discovering that the amount of aluminum alloy, etc. constituting the metal-based composite can be more than 50% by volume by producing a preform or the like from a unique mixed material in which the above-mentioned fine metal powder and/or ceramic powder (hereinafter also referred to as "fine powder of metal powder, etc.") is further added with powder of aluminum alloy, etc. having a particle size larger than these powders, and impregnating the obtained preform or the like with molten aluminum alloy, etc. In other words, the amount of aluminum alloy, etc. constituting the metal-based composite of the present invention is the sum of the amount attributable to the powder of aluminum alloy, etc. added in advance to the forming material of the preform, etc., and the amount of molten aluminum alloy, etc. melted and impregnated. By configuring as described above, the metal-based composite of the present invention has a new configuration that has not been seen in the past, in which the aluminum alloy, etc. constituting the metal-based composite is more than 50% by volume.

The high-strength metal-based composite of the present invention is a composite formed by impregnating and filling a porous preform or the like made of a mixed powder to which "powder of aluminum alloy, etc." is added with "molten aluminum alloy, etc.", so that the form may change due to a melting of a part or all of the "powder of aluminum alloy, etc.". For this reason, it can be said that the high-strength metal-based composite of the present invention has a part that cannot be directly specified by its structure or characteristics as an invention of a product. However, in this regard, the degree of melting and the state of melting of each of the metal powders forming the porous preform, etc., which are caused by the impregnation and filling of the complex pores of the porous preform, etc., which constitutes the high-strength metal-based composite of the present invention with molten aluminum alloy, etc., naturally vary, and it is impossible or almost impractical to directly specify the microscopic melting states that differ individually in the metal powders forming such porous preforms, etc., by the structure or characteristics of the product. Because it is clear that such circumstances exist, the high-strength metal-based composite of the present invention, which is an invention of a product, is specified as a manufacturing method for a composite, which is "a composite in which molten aluminum or an aluminum alloy is impregnated and filled into a porous filled body or molded body (preform) made of a mixed powder to which aluminum and aluminum alloy powders have been added."

As described above, the manufacturing method of the metal matrix composite of the present invention differs from the conventional method of manufacturing preforms and the like made only of metal powder or ceramic powder by adding powder of an aluminum alloy or the like larger than fine metal powder or ceramic powder to the raw material to manufacture a porous preform and the like, and further by impregnating the voids in the preform with molten aluminum alloy or the like, the volume percentage of the aluminum alloy or the like can be made to exceed 50%, making it possible to manufacture a metal matrix composite material with excellent workability and high strength.

Specifically, the metal matrix composite of the present invention having the above-mentioned composition has a bending strength of 500 MPa or more, for example, 550 MPa or more, or even 700 MPa or more, resulting in a high-strength metal matrix composite. Even more surprisingly, it has been confirmed that the metal matrix composite of the present invention has good processability despite the high bending strength described above, and can be processed with carbide tools, which was not possible with conventional composites. The bending strength is a value measured in accordance with JIS R1601. Specifically, the value is measured by preparing a test piece of the specified dimensions in accordance with JIS R1601 and performing a three-point bending test. The value is also measured at 25°C (room temperature).

According to the method for producing a metal matrix composite of the present invention, the ratio of fine powder such as metal powder and powder such as aluminum alloy used in combination as a forming material for a preform can be freely changed, so that the ratio of fine powder such as metal powder and aluminum alloy in the final metal matrix composite can be freely designed. Furthermore, in the manufacturing method of the present invention, the material of the fine powder such as metal powder used as a forming material for a preform and the like and the particle size determined within the range specified in the present invention can be freely designed, so that a metal matrix composite with desired characteristics can be obtained. For example, according to the study by the inventors, the smaller the average particle size of the fine powder such as metal powder, the greater the strength of the final metal matrix composite. The details of the metal matrix composite and the manufacturing method of the metal matrix composite of the present invention will be described below. First, the manufacturing method of the metal matrix composite of the present invention will be described.

[Method of producing the metal matrix composite of the present invention]
As explained above, the manufacturing method of the present invention is a completely new manufacturing method that makes it possible to increase the volume percentage of the aluminum alloy or the like in the finally obtained metal matrix composite to more than 50% by adding a powder of an aluminum alloy or the like in advance to a forming material of a preform, etc. That is, in the present invention, the effective influence on the physical property values of the finally obtained metal matrix composite due to the average particle size of fine powder such as metal powder used as a raw material can be realized by obtaining a metal matrix composite by the following procedure, unlike the conventional method of manufacturing a metal matrix composite using a preform or the like made only of a metal powder or ceramic powder.

(1) Fine metal powder or ceramic powder In the manufacturing method of the metal matrix composite of the present invention, one or more fine powders selected from the group consisting of metal powders and ceramic powders having an average particle size of 0.3 μm or more and 8 μm or less are used as a material for forming a porous filler or a molded body (preform). The metal powder is not particularly limited, and examples thereof include at least one selected from the group consisting of silicon powder, iron powder, stainless steel powder, copper powder, titanium powder, etc. In addition, examples of the ceramic powder include any one selected from the group consisting of alumina powder, silica powder, aluminum borate powder, silicon carbide powder, silicon nitride, aluminum nitride powder, etc. In addition, in the case of using any of the above materials, in the present invention, it is necessary to use a fine metal powder or ceramic powder within the range of the average particle size specified in the present invention. Specifically, a powder having an average particle size in the range of 0.3 μm or more and 8 μm or less is used. The reason for making the particle size of the metal powder or ceramic powder 8 μm or less is that if a larger material is used, the interface between the metal powder or ceramic powder and the aluminum alloy, etc., becomes too large after impregnation with molten aluminum alloy, etc., resulting in a decrease in the strength of the final product, the metal matrix composite. On the other hand, the reason for making the particle size 0.3 μm or more is that the strength of the obtained metal matrix composite does not change much even if the particle size is made smaller than this, and if the powder is too fine, it is likely to aggregate, which may impair the uniform dispersion of the reinforcing material in the preform, etc., formed from the mixed powder.

(2) Aluminum powder/aluminum alloy powder The method for producing a metal matrix composite of the present invention is characterized in that a mixed powder in which an aluminum powder or an aluminum alloy powder having an average particle size of 10 μm to 300 μm is added to a fine powder such as the metal powder described above is used to form a porous filled body or a molded body (preform). According to the study by the present inventors, by configuring in this way, in the metal matrix composite of the present invention, the volume ratio of the fine powder such as a metal powder functioning as a reinforcing material can be controlled to a desired value. That is, by adding a powder such as an aluminum alloy to the forming material of a porous preform, etc., in the next step, the total amount of the aluminum alloy, etc. of the metal matrix composite, which is the final product, can be controlled by combining it with the molten aluminum alloy, etc., impregnated into the voids of the porous preform, etc. In this way, according to the present invention, the ratio of one or more fine powders selected from the group consisting of metal powders and ceramic powders constituting the metal matrix composite, which is the final product, to the aluminum alloy, etc. can be changed to obtain desired physical property values.

The powder of aluminum alloy or the like used to form the porous preform or the like that characterizes the present invention and constitutes the metal-based composite of the present invention has an average particle size of 10 μm or more and 300 μm or less. If it is less than 10 μm, it is likely to aggregate and it is difficult to mix uniformly with the fine powder of metal powder or the like used in combination. On the other hand, if it exceeds 300 μm, the powder of aluminum alloy or the like is too large, and the uniformity with the fine powder of metal powder or the like used in combination with the mixed powder is lost, and the strength of the preform or the like may decrease. As described below, by adding the powder of aluminum alloy or the like having the specific particle size described above to the mixed powder that forms the porous preform or the like, it is possible to control the volume ratio of the metal powder and/or ceramic powder that functions as a reinforcing material that constitutes the final product, the metal-based composite.

For example, the powder volume percentage of a molded body (preform) made from a mixture of ceramic powder and/or metal powder and aluminum alloy powder, etc., used in the present invention, varies depending on the particle size and mixing ratio of the powder used, but is generally 50 to 60 volume percent overall, with voids at 40 to 60 volume percent. Therefore, the volume percentage of metal powder, etc. can be controlled by the molten aluminum alloy, etc., impregnated into the voids of a porous preform, etc., and the aluminum alloy powder, etc., added to the molded body, etc., which characterizes the present invention. In other words, if the amount of aluminum alloy powder, etc. added increases, the volume percentage of fine powder, such as metal powder, in the final product, the metal matrix composite, can be reduced. As a result, according to the present invention, it is possible to manufacture a good metal matrix composite product with a volume percentage of 50% or less, which was not possible with metal powder and/or ceramic powder alone. The aluminum alloy powder, etc., which characterizes the present invention, can be used in different amounts to achieve the final desired volume percentage of metal powder and/or ceramic powder. The amount of addition is not particularly limited. Roughly speaking, the total volume percentage of the metal powder and/or ceramic powder used and the aluminum alloy powder, etc., added is 50-70%, so the total amount of aluminum alloy, etc. can be controlled by changing the ratio of aluminum alloy powder, etc., added as necessary and taking into account the amount of molten aluminum alloy, etc., that is impregnated into the porous voids.

Examples of fine metal powders constituting the metal-based composite of the present invention include silicon powder, iron powder, stainless steel powder, copper powder, and titanium powder. Examples of fine ceramic powders constituting the metal-based composite of the present invention include alumina powder, silica powder, aluminum borate powder, silicon carbide powder, silicon nitride powder, and aluminum nitride. In the present invention, one or more types of powders selected from the metal powders and ceramic powders listed above can be used.

The metal matrix composite of the present invention is preferably a porous preform or the like made of a mixed powder of the above-mentioned metal powder or ceramic powder and the above-mentioned aluminum alloy powder, etc., impregnated and filled with molten aluminum alloy under pressure or without pressure, and the mixed powder is mixed in the following ratio. That is, the mixing ratio of the fine powder of the metal powder, etc. and the powder of the aluminum alloy, etc. in the mixed powder is preferably 10:90 to 90:10. If the ratio of the fine powder of the metal powder, etc. to the powder of the aluminum alloy, etc. is less than 10:90, the ratio of the fine powder of the metal powder, etc. that functions as a reinforcing material in the final metal matrix composite becomes too small, which is not preferable because the desired strength improvement effect may not be obtained. On the other hand, if the ratio of the fine powder of the metal powder, etc. to the powder of the aluminum alloy, etc. exceeds 90:10, the ratio of the fine powder of the metal powder, etc. that constitutes the metal matrix composite becomes too large, which is not preferable because the processability of the final metal matrix composite becomes poor.

In the metal matrix composite of the present invention, fine powders such as metal powders with a particle size of 0.3 μm or more and 8 μm or less are used to improve the strength of the composite. However, since the use of such fine powders is prone to agglomeration due to static electricity, a mixed powder is used to which relatively large powders such as aluminum alloys with a particle size of 10 μm to 300 μm are added. By configuring in this way, a secondary effect of suppressing the agglomeration of the metal powder and/or ceramic powder, which are the reinforcing materials, is obtained, and ultimately, a good metal matrix composite consisting of uniformly dispersed metal powder and/or ceramic powder and aluminum alloys can be realized. In addition, when a molten metal such as an aluminum alloy is impregnated into a molded body or the like by the non-pressurized infiltration method, in the conventional technology, when a metal powder or ceramic powder with an average particle size of 1 μm or less is used to produce a porous preform or the like, the pores are too small to be impregnated with the molten metal. However, the technology of the present invention has the following effects and can solve the problem. That is, in the metal matrix composite of the present invention, the pores are enlarged by adding a powder of an aluminum alloy or the like having an average particle size of 10 μm or more and 300 μm or less to prepare a porous preform, etc., so that even when the above-mentioned non-pressurized infiltration method is applied, the molten aluminum alloy or the like can be easily impregnated.

(3) Preparation of mixed powder The mixed powder consisting of aluminum alloy powder or the like having an average particle size of 10 μm to 300 μm added to the fine powder such as metal powder described above can be easily obtained by uniformly mixing using a conventional mixer. In the present invention, a porous preform or the like is obtained using the prepared specific mixed powder. Since the use of the fine powder as described above results in low filling property, when a molded body (preform) is obtained by a method such as press molding, CIP, and sedimentation, a binder may be used in combination with the mixed powder as necessary. As the binder, inorganic binders such as ethyl silicate, silicone, water glass, etc., alumina-based inorganic binders such as aluminum alkoxide, and organic inorganic binders can be suitably used. The amount of binder used is preferably added to the mixed powder within a range of 0.5% to 10% by mass. In order to further improve the moldability of the molded body (preform), in addition to the inorganic binders listed above, for example, organic binders such as PVA and PVB may be added.

(4) Preparation of Preforms, etc. Preforms, etc. prepared using the mixed powder having the above-mentioned composition may be fired at a temperature of, for example, about 200°C to 700°C so as to facilitate subsequent operations. When a metal powder is used as a reinforcing material, the firing temperature is desirably 700°C or less to prevent oxidation. When Mg powder is added to the mixed powder for impregnation with molten metal such as an aluminum alloy using a non-pressure infiltration method, the firing temperature is desirably 500°C or less to prevent oxidation and deterioration of Mg during firing.

(5) High-pressure impregnation of molten metal such as aluminum alloy In the manufacturing method of the high-strength metal-based composite of the present invention, whether high-pressure impregnation or non-pressure infiltration is used, the molten metal such as aluminum alloy can be impregnated and filled in a good state into the porous preform obtained as described above to obtain a metal-based composite. When using the high-pressure impregnation method, for example, the molten metal such as aluminum alloy at about 700 ° C to 800 ° C is impregnated at a pressure of, for example, about 20 MPa to 200 MPa. A pressure of less than 20 MPa is not preferable because the pressure is too low and there is a concern that the material may not be sufficiently impregnated. On the other hand, impregnation is possible even at a pressure of more than 200 MPa, but a pressure of 200 MPa or less is sufficient in consideration of the energy cost and the life of the pressure vessel.

(6) Infiltration of molten aluminum alloy, etc. without pressure When infiltrating molten aluminum alloy, etc., by the infiltration method without pressure, so-called Rankside method, it is necessary to use a mixed powder in which 0.5 to 10 parts by mass of Mg powder is added to 100 parts by mass of a total of fine powder, such as metal powder, and powder, such as aluminum alloy, etc. Then, a good metal matrix composite can be obtained by infiltrating a molten aluminum alloy, etc., without pressure, for example, in a nitrogen atmosphere at 700°C to 900°C into a porous preform, etc., obtained by using the above mixed powder.

The present invention will be described in more detail below with reference to examples and comparative examples. Note that the present invention is not limited to the examples.

[Example 1]
1200g of SiC powder with an average particle size of 5μm and 800g of A6061-based aluminum alloy powder with an average particle size of 25μm were placed in a plastic pot, and mixed for 2 hours with alumina balls. 100g of ethyl silicate hydrolysis liquid was added to the pot so that _40g of SiO2 was included, and the mixture was mixed for another 30 minutes. The mixture was placed in a mold with an inner dimension of 200mm x 200mm and press molded at a pressure of 45t. The mixture was further fired at 500°C for 2 hours to produce a molded body (preform) containing SiC powder and aluminum alloy powder. The obtained molded body was placed in a metal mold, and molten A6061-based aluminum alloy melted at 750°C was poured in, and the preform was impregnated at a pressure of 100MPa to cast a composite.

The composite obtained by the above method was an aluminum alloy-based composite with 30 volume % SiC fine powder and 70 volume % remainder. Test pieces for measurement of the specified dimensions were cut out from the obtained composite, and the bending strength of the composite was measured at room temperature in accordance with JIS R1601 using the test pieces. Measurements were also performed for other examples in the same manner. The measurement result was 740 MPa, which was quite high strength. It was also confirmed that the obtained composite had good workability and could be machined with carbide tools.

[Example 2]
1200g of SiC powder having an average particle size of 5 μm, 800g of A6061-based aluminum powder having an average particle size of 25 μm, and 40g of Mg powder having an average particle size of 50 μm were added to the mixture and mixed for 2 hours in the same manner as in Example 1. A silicone resin (product name: KR-220L, manufactured by Shin-Etsu Chemical Co., Ltd.) liquid dissolved in isopropyl alcohol was added in an amount equivalent to 30 g% of SiO ₂ , and mixed for 30 minutes. This was press-molded and fired in the same manner as in Example 1 to produce a molded body (preform). A preform having a size of 100 mm x 100 mm x 30 mm was cut out from this molded body. Then, as shown in FIG. 1, the preform 1 was impregnated and filled with molten A6061-based aluminum 2 without pressure to form a composite aluminum alloy-based composite. Specifically, as shown in Fig. 1, a preform 1 and an A6061-based aluminum 2 were placed in a carbon container 4, and the container was placed in a furnace in a nitrogen atmosphere, and the temperature was raised at a rate of 100°C/hour, and then the container was held at 780°C for 2 hours, after which the composite was taken out. 3 in Fig. 1 indicates a penetration path of the same material as the preform 1. The taken-out composite was processed for measurement, and the physical properties were measured in the same manner as in Example 1.

The composite obtained in Example 2 was an aluminum alloy-based composite, similar to Example 1, with 30 volume % SiC fine powder and 70 volume % aluminum alloy. The bending strength measured in the same manner as in Example 1 was 650 MPa, making it a high-strength composite. In addition, the obtained composite had good workability and could be machined with a carbide tool.

[Example 3]
800 g of SiC powder having an average particle size of 3 μm and 1200 g of A1050-series aluminum alloy powder having an average particle size of 30 μm were mixed with 100 g of ethyl silicate hydrolyzed liquid so as to contain 40 g, calculated as SiO ₂ , and a preform containing the SiC powder and the aluminum alloy powder was produced in the same manner as in Example 1. The obtained preform was then impregnated with molten A1050-series aluminum alloy at high pressure in the same manner as in Example 1 to obtain the composite of this example.

When the physical properties of the composite obtained above were measured, it was found to be an aluminum alloy-based composite with 20 volume % SiC fine powder and 80 volume % remainder. The bending strength measured in the same manner as in Example 1 was 700 MPa, making it a fairly high-strength composite. In addition, the composite obtained had good workability and could be machined with a carbide tool.

[Example 4]
1200 g of metal silicon powder having an average particle size of 5 μm was mixed with 200 g of A6061-based aluminum alloy powder having an average particle size of 25 μm in the same manner as in Example 1, and 100 g of ethyl silicate hydrolyzed liquid was added thereto so that 40 g was contained in terms of SiO ₂ , and further mixed for 30 minutes. Using the obtained mixture, a molded body (preform) was produced in the same manner as in Example 1. Then, using the obtained preform, a molten A6061-based aluminum alloy was high-pressure impregnated in the same manner as in Example 1 to obtain a composite.

The physical properties of the composite obtained above were measured, and it was found to be an aluminum alloy-based composite containing 25 volume % silicon powder and 75 volume % aluminum alloy powder. The bending strength measured in the same manner as in Example 1 was 580 MPa, which was a high strength. Furthermore, the obtained composite had good processability and could be processed with a carbide tool.

[Comparative Example 1]
In the same manner as in Example 1, 100 g of ethyl silicate hydrolyzate liquid was added to 2000 g of SiC powder having an average particle size of 14 μm larger than that specified in the present invention so that 40 g of SiO ₂ was contained, and a preform was produced from the mixed material. The obtained preform was then impregnated with molten aluminum alloy similar to that used in Example 1 to produce a composite. Comparative Example 1 differs from the present invention in that the average particle size of the SiC powder is larger than that specified in the present invention and that aluminum powder or the like is not used in the raw material mixture.

The physical properties of the composite obtained above were measured, and the composite obtained was found to be 55% by volume of SiC and 45% by volume of aluminum alloy. The bending strength measured in the same manner as in Example 1 was 320 MPa, which is comparable to that of a general aluminum alloy, and it was confirmed that this was not a high-strength composite. In addition, the composite obtained had poor workability and could not be machined with a carbide tool, so it was machined with a diamond end mill.

[Comparative Example 2]
The composite of this example was produced in the same manner as in Example 1, except that a mixture of 1200 g of SiC powder having an average particle size of 14 μm, which is larger than that specified in the present invention, and 800 g of 6061-series aluminum alloy powder having an average particle size of 25 μm was used. The physical properties of the composite obtained were a composite containing 28 vol% SiC and 72 vol% aluminum. The bending strength measured in the same manner as in Example 1 was 330 MPa, which was comparable to that of a general aluminum alloy and was not a high-strength composite. In addition, the composite obtained had poor processability and could not be processed with a cemented carbide tool, and it was necessary to process it with a diamond end mill.

[Comparative Example 3]
A molded body (preform) was produced in the same manner as in Example 1, except that a mixture of 1200 g of SiC powder having an average particle size of 22 μm, which is larger than that specified in the present invention, and 800 g of A6061-series aluminum alloy powder having an average particle size of 25 μm was used. Then, in the same manner as in Example 1, the preform obtained above was impregnated with molten A6061-series aluminum alloy to obtain the composite of this example.

When the physical properties of the obtained composite were measured, it was found to be an aluminum-based composite with 31 volume % SiC powder and 69 volume % remainder. In addition, the bending strength measured in the same manner as in Example 1 was 410 MPa, which was lower than the composites of Examples 1 to 4 and had a bending strength comparable to that of ordinary aluminum, and was not a high-strength composite. In addition, the obtained composite had poor workability and could only be processed with diamond tools.

[Comparative Example 4]
A molded body (preform) was produced in the same manner as in Example 1 using 1,200 g of metal silicon powder having an average particle size of 45 μm, which is larger than that specified in the present invention, and 800 g of A6061-series aluminum alloy powder having an average particle size of 25 μm. The preform was then impregnated with the A6061-series aluminum alloy in the same manner as in Example 1 to obtain a composite.

The physical properties of the obtained composite were measured and it was found to be a composite containing 29 volume % 45 μm metal silicon powder and 71 volume % A6061 aluminum alloy. In addition, the bending strength measured in the same manner as in Example 1 was 270 MPa, making it a composite with low strength.

[Comparative Example 5]
A commercially available ingot of a composite material of 30% by volume of SiC powder/70% by volume of aluminum manufactured by Duralcan, USA was used, and the ingot was melted at 730°C and cast into a sand mold to produce a composite material of 200 mm x 200 mm x 50 mm (thickness). From this, a test piece for measurement was cut out in the same manner as in Example 1, and the bending strength was measured in the same manner. As a result, the composite material obtained above had a low bending strength of 380 MPa, and was also poor in workability, and could only be processed with a diamond tool.

[Summary of evaluation results]
Table 1 shows the preparation conditions of the composites of the examples and comparative examples, and the evaluation results of each of the composites obtained. The evaluation of the processability was evaluated as "good" for composites that could be processed with a cemented carbide tool, and "poor" for composites that could not be processed with a cemented carbide tool and could only be processed with a diamond tool. In Comparative Example 5, a commercially available composite material (commercial product) of SiC powder and aluminum metal was used. In Example 2, the molten aluminum alloy was impregnated into the preform without pressure. In all examples other than Example 2, the molten aluminum alloy was impregnated and filled into the preform at a high pressure of 100 MPa.

1: Preform 2: Aluminum alloy, etc. 3: Infiltration channel made of the same material as the preform 4: Carbon container

Claims (7)

A composite in which molten aluminum or aluminum alloy is impregnated and filled into a porous filler or molded body (preform) made of a mixed powder of one or more fine powders selected from the group consisting of metal powders and ceramic powders with an average particle size of 0.3 μm or more and 8 μm or less, and one or more aluminum/aluminum alloy powders selected from the group consisting of aluminum powders and aluminum alloy powders with an average particle size of 10 μm or more and 300 μm or less, and the composite has a filling rate of the fine powder of 10 vol % or more and 50 vol % or less, and a bending strength of 500 MPa or more and 800 MPa or less. The high-strength metal matrix composite according to claim 1, wherein the metal powder constituting the fine powder of the mixed powder is any one selected from the group consisting of silicon powder, iron powder, stainless steel powder, copper powder, and titanium powder, the ceramic powder is any one selected from the group consisting of alumina powder, silica powder, aluminum borate powder, silicon carbide powder, silicon nitride powder, and aluminum nitride powder, and further, the blending ratio of the fine powder and the aluminum/aluminum alloy powder constituting the mixed powder is 10:90 to 90:10. The high-strength metal-based composite according to claim 1 or 2, further comprising one or more binders selected from the group consisting of silica-based binders and alumina-based organic/inorganic binders, added to the mixed powder in an amount of 0.5% or more and 10% or less by mass. A porous packed body or molded body (preform) is obtained using a mixed powder obtained by adding one or more types of aluminum/aluminum alloy powders selected from the group consisting of aluminum powders and aluminum alloy powders, each having an average particle size of 10 μm to 300 μm, to one or more types of fine powders selected from the group consisting of metal powders and ceramic powders, each having an average particle size of 0.3 μm to 8 μm, and then subjecting the resulting packed body or molded body (preform) to
Molten aluminum or aluminum alloy is impregnated and filled at a high pressure of 20 MPa or more and 200 MPa or less to form a composite.
A method for producing a high-strength metal matrix composite, comprising the steps of: obtaining a metal matrix composite having a filling rate of the fine powder of 10 volume % or more and 50 volume % or less, and a bending strength of 500 MPa or more and 800 MPa or less. A porous packed body or molded body (preform) is obtained by adding one or more aluminum/aluminum alloy powders selected from the group consisting of aluminum powders and aluminum alloy powders having an average particle size of 10 to 300 μm to one or more fine powders selected from the group consisting of metal powders and ceramic powders having an average particle size of 0.3 μm or more and 8 μm or less, and further adding magnesium powder in an amount of 0.5 to 10 parts by mass to 100 parts by mass of the mixed powder to obtain an Mg powder-containing mixed powder, and then subjecting the resulting packed body or molded body (preform) to
The material is impregnated and filled with molten aluminum or aluminum alloy without pressure to form a composite.
A method for producing a high-strength metal matrix composite, comprising the steps of: obtaining a metal matrix composite having a filling rate of the fine powder of 10 volume % or more and 50 volume % or less, and a bending strength of 500 MPa or more and 800 MPa or less. The method for producing a high-strength metal matrix composite according to claim 4 or 5, wherein the metal powder constituting the fine powder of the mixed powder is any one selected from the group consisting of silicon powder, iron powder, stainless steel powder, copper powder and titanium powder, the ceramic powder is any one selected from the group consisting of alumina powder, silica powder, aluminum borate powder, silicon carbide powder, silicon nitride powder and aluminum nitride powder, and further, the blending ratio of the fine powder and the aluminum/aluminum alloy powder constituting the mixed powder is 10:90 to 90:10. The method for producing a high-strength metal matrix composite according to claim 4 or 5, further comprising externally adding one or more binders selected from the group consisting of silica-based binders and alumina-based organic/inorganic binders in an amount of 0.5% or more and 10% or less by mass to the mixed powder.

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