Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D19/00—Casting in, on, or around objects which form part of the product
  • B22D19/0081—Casting in, on, or around objects which form part of the product pretreatment of the insert, e.g. for enhancing the bonding between insert and surrounding cast metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D19/00—Casting in, on, or around objects which form part of the product
  • B22D19/02—Casting in, on, or around objects which form part of the product for making reinforced articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D19/00—Casting in, on, or around objects which form part of the product
  • B22D19/14—Casting in, on, or around objects which form part of the product the objects being filamentary or particulate in form
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/002—Castings of light metals
  • B22D21/007—Castings of light metals with low melting point, e.g. Al 659 degrees C, Mg 650 degrees C
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/02—Casting exceedingly oxidisable non-ferrous metals, e.g. in inert atmosphere
  • B22D21/04—Casting aluminium or magnesium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/24—After-treatment of workpieces or articles
  • B22F3/26—Impregnating
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0408—Light metal alloys
  • C22C1/0416—Aluminium-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
  • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
  • C22C29/065—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on SiC
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/10—Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/12—Metallic powder containing non-metallic particles
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
  • C22C32/0052—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents only carbides
  • C22C32/0063—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents only carbides based on SiC

Definitions

• the present invention relates to a metal matrix composite obtained by forming a composite from a fine ceramic powder and/or a fine metal powder that functions as a reinforcing material and molten aluminum or a molten aluminum alloy as a matrix material.
• the present invention relates to a technique that provides: a high-strength metal matrix composite having high strength and excellent processability, wherein the high strength and excellent processability are realized by using a mixed powder obtained by adding an aluminum powder or an aluminum alloy powder (hereinafter, also referred to as "powder of an aluminum alloy or the like") having a larger particle size than the above-described fine powder to the above-described fine powder; and a method for producing the same.
• MMCs materials in which aluminum or an aluminum alloy and a ceramic form a composite
• CFRPs Carbon Fiber Reinforced Plastics
• CMCs Ceramic Matrix Composites
• a ceramic-molded body and a ceramic form a composite by CVD or the like composites in which aluminum and another metal powder form a composite, and the like
• aluminum alloy or the like aluminum alloy
• MMCs have been widely used in the industrial world as mechanical parts, electronic substrates, apparatuses for producing semiconductors or liquid crystals, robot arms, gas turbine materials, power devices, and the like that possess desired properties such as light weight, high strength, high rigidity, and high heat resistance.
• Patent Literature 1 discloses a composite-forming method including: curing a ceramic powder and an inorganic binder added to the ceramic powder to produce an intermediate molded body (preform); and infiltrating a molten aluminum alloy or the like into pores of the intermediate molded body (preform) with a high-pressure press.
• an aluminum alloy matrix composite (MMC) in which the ceramic powder is uniformly distributed can be simply prepared by impregnating the characteristic intermediate molded body (preform) with the molten aluminum alloy or the like forcibly at a high pressure.
• MMC aluminum alloy matrix composite
• the above-described production method is also applicable to an aluminum alloy matrix composite (MMC) using, as a material for forming a composite, a powder-filled body formed of a ceramic powder.
• Patent Literature 2 discloses a method for forming a composite, wherein a particular intermediate molded body (preform) in which a Mg powder is added to a ceramic powder is placed in a nitrogen atmosphere, and an aluminum alloy is infiltrated into the intermediate molded body (preform) without pressurization.
• the principle of this method is that the wettability between the ceramic and the aluminum alloy or the like is improved in the Mg-and-nitrogen atmosphere to accelerate a so-called capillary phenomenon, and thereby the molten aluminum alloy or the like is infiltrated into voids of the preform.
• the ceramic-filling rate is increased to decrease the voids, thereby making it possible to increase the ceramic-filling rate, and as result, an aluminum alloy matrix composite (MMC) of a ceramic and an aluminum alloy or the like, having high physical property values of Young's modulus, thermal conductivity, coefficient of thermal expansion, and the like, can be produced.
• MMC aluminum alloy matrix composite
• the aluminum alloy or the like can be infiltrated into the voids by using the preform while the shape of the preform by using the preform is kept, and therefore the MMC having a near-net shape close to a product shape can be produced.
• the aluminum alloy matrix composite can also be produced by the following casting method other than the above-described production method.
• a ceramic powder of silicon carbide, alumina, or the like is put into a molten aluminum alloy or the like, and the resulting mixture is stirred at a high speed to prepare a molten aluminum alloy or the like containing the ceramic powder, or a composite obtained by impregnating a mixed powder obtained by adding Mg to a ceramic powder with an aluminum alloy or the like in a nitrogen atmosphere without pressurization is melted and mixed uniformly to prepare a molten metal for casting.
• the molten metal prepared is cast in a conventionally used mold, such as a sand mold for casting, a metal mold, and a mold for lost wax casting, to produce a composite of the ceramic and the aluminum alloy.
• the aluminum alloy matrix composite can also be produced by a production method making use of the following HIP (Hot Isostatic Pressing) method.
• HIP Hot Isostatic Pressing
• a so-called SupremEX method is known, in which a powdery molded body obtained by subjecting a ceramic powder to mechanical alloying coating with an aluminum alloy or the like is subjected to firing and subsequent high-pressure isostatic pressing by HIP to produce a complex of the ceramic powder and the aluminum alloy or the like.
• a method which is similar to this a method is known, wherein: a molten aluminum alloy or the like in which a ceramic powder is mixed is sprayed and deposited to produce a deposit of a composite; and the deposit is subjected to HIP treatment to remove pores contained in this deposit, and thereby a composite is produced.
• the percentage by volume of the powder-filled body itself or the powder itself of the preform is determined by the properties of the powder, and therefore a product having a volume percentage of higher than 50% by volume can only be produced.
• the pores in the powder-filled body or preform are impregnated with the molten aluminum alloy or the like, and therefore it is difficult to decrease the volume of the metal powder and the ceramic powder and increase the amount of the aluminum alloy or the like.
• a metal powder of about 10 ⁇ m or larger and a ceramic powder of about 10 ⁇ m or larger are usually used as a reinforcing material or the like to be used for forming a composite, which increases the load to working tools, and therefore there is a problem that an aluminum alloy matrix composite (MMC) obtained by the above-described high-pressure impregnation method is inferior in processability.
• MMC aluminum alloy matrix composite
• a powder is molded into a preform, and voids of the preform are impregnated with the molten aluminum alloy or the like, but a preform with more than 50% by volume of voids, in other words, an aluminum alloy matrix composite having a powder-filling rate of 50% by volume or lower, cannot be produced.
• the molten metal is likely to entrap air during casting, and therefore a composite without a defect is considered to be hard to obtain.
• an object of the present invention is to provide new techniques on an aluminum alloy matrix composite that cannot be obtained with conventional production techniques, that has good workability while having high strength, and that makes it possible to suppress an increase in production costs, the composite being useful in terms of industrial utility and having a high practical value; and a method for producing the composite.
• the present invention provides a high-strength metal matrix composite described below.
• "average particle size” is a particle size at an integrated value of 50% (median diameter) in the particle size distribution determined by a laser diffraction/scattering method.
• the present invention makes it possible to provide a metal matrix composite product that cannot be obtained by the conventional production techniques, the metal matrix composite having a high practical value, wherein: the volume percentage of a reinforcing material composed of a metal powder and/or a ceramic powder is 50% by volume or lower; the strength is high as high as a flexural strength of 500 MPa or higher; and the processability is good. Further, the present invention provides a method for producing a metal matrix composite, the method making it possible to produce the metal matrix composite having excellent properties as described above by a simple method and being extremely useful also in terms of practicality in that an increase in production costs is suppressed.
• Figure 1 is a schematic diagram for describing a method of producing a high-strength metal matrix composite of the present invention without pressurization.
• a molded body (preform) as an example, but even a filled body obtained by packing a raw material powder in a metal box or the like to perform vibration molding or the like without active molding by pressing unlike the molded body (preform) also generally has a volume percentage of 50% or higher, and therefore there is a problem that the processability of the composite is deteriorated, which is the same as in the composite using the molded body (preform).
• the filled body or molded body (preform) of a metal powder and/or a ceramic powder is also referred to as a "preform or the like.”
• the present inventors Facing the difficulty of preparing a preform or the like formed of a metal powder and/or a ceramic powder and having a filling ratio of 50% by volume or less in the above-described conventional techniques, the present inventors have conducted diligent studies to find that the problems can be solved by forming the preform or the like in the manner as described below. Specifically, by forming, in the manner as described below, the preform or the like, which forms a metal matrix composite, which is to be impregnated and filled with a molten aluminum alloy or the like, and which is formed of the metal powder and/or the ceramic powder, the problems can be solved.
• the present inventors have found that by using a mixed powder obtained by adding a powder of an aluminum alloy or the like having an average particle size of 10 ⁇ m or larger and 300 ⁇ m or smaller to the above-described fine metal powder and/or fine ceramic powder to prepare the preform or the like formed of the mixed powder, the above-described problems can be solved.
• the "average particle size" specified in the present invention refers to a particle size at an integrated value of 50% in the particle size distribution determined by a laser diffraction/scattering method, that is, a so-called 50% median size.
• the present inventors have found that the amount of the aluminum alloy or the like in the metal matrix composite being higher than 50% by volume can be achieved when the preform or the like is prepared with a particular mixed material obtained by adding a powder of an aluminum alloy or the like to the above-described fine metal powder and/or fine ceramic powder (hereinafter, also referred to as "fine metal powder and/or the like"), and the resulting preform or the like is impregnated with a molten aluminum or the like.
• the particle size of the powder of an aluminum alloy or the like is larger than that of the fine metal powder and/or the fine ceramic powder.
• the amount of the aluminum alloy or the like in the metal matrix composite of the present invention is the sum total of the amount derived from the powder of an aluminum alloy or the like preliminarily added to the material for forming the preform or the like and the amount of the molten aluminum alloy or the like which is melted to impregnate the preform or the like.
• the metal matrix composite of the present invention formed in the manner as described above is a novel metal matrix composite containing the aluminum alloy or the like in an amount of higher than 50% by volume in the metal matrix composite, which has never been obtained so far.
• the above-described high-strength metal matrix composite of the present invention is a composite obtained by impregnating and filling a porous preform or the like with a "molten aluminum alloy or the like," wherein the porous preform or the like is formed of a mixed powder containing a "powder of an aluminum alloy or the like," and therefore part or the whole of the "powder of an aluminum alloy or the like” may be melted to change the form of the composite. For this reason, it can be said that in the high-strength metal matrix composite of the present invention as the product invention, there exist some parts not directly specified by the structure or properties.
• the product is specified by the method for producing the composite, which provides "a composite obtained by impregnating and filling a porous filled body or molded body (preform) with molten aluminum or a molten aluminum alloy, wherein the porous filled body or molded body (preform) is formed of a mixed powder containing an aluminum or aluminum alloy powder.”
• a powder of an aluminum alloy or the like having a larger size than the fine metal powder or fine ceramic powder is added to the raw material to prepare a porous preform or the like as described above, which is different from the conventional methods for preparing a preform or the like consisting of a metal powder or a ceramic powder, furthermore, voids of the preform or the like are impregnated with a molten aluminum alloy or the like, and thereby the volume percentage of the aluminum alloy or the like being higher than 50% is realized, so that a metal matrix composite having excellent processability and high strength can be produced.
• the metal matrix composite of the present invention which is composed of the above-described combination, is a metal matrix composite having high strength, as high as a flexural strength of 500 MPa or higher, for example, 550 MPa or higher, and further, 700 MPa or higher. Furthermore, surprisingly enough, although the metal matrix composite of the present invention has high flexural strength as described above, it has good processability, and it is ascertained that processing with a cemented carbide tool is possible, which is not realized for the conventional composites.
• the flexural strength is a value measured according to JIS R1601. Specifically, the flexural strength is a value measured, according to JIS R1601, by the three-point flexural test preparing a specimen having a specified size. The measurement is performed at 25°C (room temperature).
• the ratio of the fine metal powder and/or the like to the powder of an aluminum alloy or the like, which are materials for forming the preform or the like, can be changed freely, and therefore the ratio of the fine metal powder and/or the like to the aluminum alloy or the like in the final metal matrix composite can also be designed freely.
• the particle size of the fine metal powder and/or the like, which is determined within the range specified in the present invention according to the material quality of the fine metal powder and/or the like which is used as the material for forming the preform or the like can be freely designed, and therefore a metal matrix composite having desired properties can be obtained.
• details on the metal matrix composite and method for producing a metal matrix composite of the present invention will be described. First, the method for producing a metal matrix composite of the present invention will be described.
• the production method of the present invention is a totally new production method that makes it possible to make the percentage by volume of the aluminum alloy or the like in the finally obtained metal matrix composite higher than 50% by preliminarily adding the powder of an aluminum alloy or the like to the material for forming the preform or the like.
• the present invention makes it possible to realize an effective influence on the physical property values of the finally obtained metal matrix composite, the influence brought about by the average particle size of the fine metal powder and/or the like which is used as a raw material, and such an effective influence can be realized by obtaining the metal matrix complex according to the following procedure, which is different from the conventional methods for producing a metal matrix composite using a preform or the like consisting of a metal powder or a ceramic powder.
• At least one fine powder selected from the group consisting of a metal powder and a ceramic powder each having an average particle size of 0.3 ⁇ m or larger and 8 ⁇ m or smaller is used as the material for forming a porous filled body or molded body (preform).
• the metal powder is not particularly limited, and examples thereof include at least one selected from the group consisting of a silicon powder, an iron powder, a stainless steel powder, a copper powder, a titanium powder, and the like.
• the ceramic powder examples include one selected from the group consisting of an alumina powder, a silica powder, an aluminum borate powder, a silicon carbide powder, a silicon nitride powder, an aluminum nitride powder, and the like.
• a fine particle having an average particle size within the range specified in the present invention needs to be used as the metal powder or the ceramic powder.
• a metal powder or a ceramic powder each having an average particle size within a range of 0.3 ⁇ m or larger and 8 ⁇ m or smaller is used.
• the reason that the average particle size of the metal powder or the ceramic powder is set to 8 ⁇ m or smaller is because when a material having an average particle size larger than that, the interface between the metal powder or the ceramic powder and the aluminum alloy or the like is too large after the impregnation with the molten aluminum alloy or the like, so that the strength of a metal matrix composite as the final product is deteriorated.
• the reason that the average particle size is set to 0.3 ⁇ m or larger is because the strength of a resulting metal matrix composite is not changed so much even when the average particle size is made smaller than that, and when the powder is too fine, it is likely to aggregate, so that there is a risk that uniform dispersion of the reinforcing material in the preform or the like formed from the mixed powder is impaired.
• the method for producing a metal matrix composite of the present invention is characterized in that a mixed powder obtained by adding an aluminum powder or an aluminum alloy powder each having an average particle size of 10 ⁇ m or larger and 300 ⁇ m or smaller to the above-described fine metal powder and/or the like is used for forming the porous filled body or molded body (preform).
• a mixed powder obtained by adding an aluminum powder or an aluminum alloy powder each having an average particle size of 10 ⁇ m or larger and 300 ⁇ m or smaller to the above-described fine metal powder and/or the like is used for forming the porous filled body or molded body (preform).
• the whole amount of the aluminum alloy or the like in the metal matrix composite as the final product can be controlled, wherein the whole amount of the aluminum alloy or the like includes the amount of the molten aluminum alloy or the like with which voids of the porous preform or the like is impregnated in the next step.
• the ratio of at least one fine powder selected from the group consisting of a metal powder and a ceramic powder to the aluminum alloy or the like in the metal matrix composite as the final product, desired physical property values can be obtained.
• a powder having an average particle size of 10 ⁇ m or larger and 300 ⁇ m or smaller is used as the powder of an aluminum alloy or the like which is used for forming the porous preform or the like that forms the metal matrix composite of the present invention and that characterizes the present invention.
• the powder has an average particle size of smaller than 10 ⁇ m, it is likely to aggregate, and it is difficult to uniformly mix the powder with the fine metal powder and/or the like to be used together with the powder.
• the powder of the aluminum alloy or the like is too large in size, and therefore there is a risk that the uniformity with the fine metal powder and/or the like to be used together for the mixed powder is impaired, which deteriorates the strength of the preform or the like.
• the powder of an aluminum alloy or the like having the above-described particular average particle size to the mixed powder for forming the porous preform or the like, it is made possible to control the percentage by volume of the metal powder and/or the ceramic powder that functions as a reinforcing material in the metal matrix composite as the final product.
• the percentage by volume of the powders of the molded body (preform) prepared from the mixed powder of a ceramic powder and/or a metal powder and the powder of an aluminum alloy or the like in the present invention is different depending on the particle sizes and mixing ratios of the powders used, but the molded body (preform) generally has a volume percentage of 50 to 60% by volume as a whole and contains 40 to 60% by volume of voids. Accordingly, the percentage by volume of the metal powder and the like can be controlled by the molten aluminum alloy or the like with which voids of the porous preform or the like is impregnated and the powder of an aluminum alloy or the like that characterizes the present invention and that is to be added to the molded body or the like.
• the addition amount of the powder of the aluminum alloy or the like when the addition amount of the powder of the aluminum alloy or the like is increased, the percentage by volume of the fine aluminum powder and/or the like in the metal matrix composite as the final product can be decreased.
• a product of a good metal matrix composite having a percentage by volume of 50% or lower can be produced, which cannot be achieved by only using the metal powder and/or the ceramic powder.
• the powder of an aluminum alloy or the like that characterizes the present invention may be used changing the addition amount in order to achieve the finally desired percentage by volume of the metal powder and/or the ceramic powder.
• the addition amount is not particularly limited.
• the total percentage by volume of the metal powder and/or the ceramic powder and the powder of an aluminum alloy or the like is 50 to 70%, and therefore the total amount of the aluminum alloy or the like can be controlled by changing, as necessary, the ratio of the powder of an aluminum alloy or the like to be added and taking into account the amount of the molten aluminum alloy or the like with which voids of the porous body is impregnated.
• Examples of the fine metal powder for forming the metal matrix composite of the present invention include a silicon powder, an iron powder, a stainless steel powder, a copper powder, and a titanium powder.
• Examples of the fine ceramic powder for forming the metal matrix composite of the present invention include an alumina powder, a silica powder, an aluminum borate powder, a silicon carbide powder, a silicon nitride powder, and aluminum nitride powder. In the present invention, one, or two or more powders selected from the metal powders and ceramic powders as given above can be used.
• the metal matrix composite of the present invention is preferably a metal matrix composite obtained by impregnating and filling the porous preform or the like with a molten aluminum alloy by pressurization or without pressurization, wherein the porous preform or the like is formed of the mixed powder of the above-described metal powder and/or ceramic powder and powder of an aluminum alloy or the like, and the mixed powder is obtained by blending the fine metal powder and/or the like and the powder of an aluminum alloy or the like in the ratio as described below.
• the blending ratio of the fine metal powder and/or the like to the powder of an aluminum alloy or the like in the mixed powder is preferably 10:90 to 90:10.
• the ratio of the fine metal powder and/or the like to the powder of an aluminum alloy or the like is less than 10:90 because the ratio of the fine metal powder and/or the like that functions as a reinforcing material in a metal matrix composite as the final product is too small, so that it may happen that the desired effect of improving the strength cannot be obtained.
• the ratio of the fine metal powder and/or the like to the powder of an aluminum alloy or the like is more than 90:10 because the ratio of the fine metal powder and/or the like that forms the metal matrix composite is too large, so that the processability of a metal matrix composite as the final product is deteriorated.
• the fine metal powder and/or the like having an average particle size of 0.3 ⁇ m or larger and 8 ⁇ m or smaller is used in order to improve the strength of the composite, but on the other hand, when such a fine powder is used, aggregation due to static electricity is likely to occur, and therefore the mixed powder obtained by adding the powder of an aluminum alloy or the like having a relatively large average particle size of 10 ⁇ m to 300 ⁇ m to the fine metal powder and/or the like is used.
• Such composition also gives a secondary effect of suppressing the aggregation of the metal powder and/or the ceramic powder as a reinforcing material and can finally realize a good metal matrix composite formed of uniformly dispersed metal powder and/or ceramic powder and aluminum alloy or the like.
• the addition of the powder of an aluminum alloy or the like having an average particle size of 10 ⁇ m or larger and 300 ⁇ m or smaller for preparation of the porous preform or the like makes pores larger, which makes it easier to impregnate the porous preform or the like with the molten aluminum alloy or the like even when the above-described non-pressurization infiltration method is applied.
• the above-described mixed powder composed of: a fine metal powder and/or the like; and a powder of an aluminum alloy or the like having an average particle size of 10 ⁇ m to 300 ⁇ m is easily obtained through uniform mixing using a commonly used mixer.
• the porous preform or the like is obtained using the particular mixed powder prepared.
• a binder may be used as necessary together with the mixed powder.
• inorganic binders such as ethyl silicate, silicone, and water glass
• inorganic binders alumina-based inorganic binders, such as aluminum alkoxides, and organic/inorganic binders
• organic/inorganic binders can be suitably used.
• the binder is preferably added to the mixed powder within a range of 0.5% or more and 10% or less on a mass basis.
• an organic binder such as, for example, PVA and PVB, may be further added in addition to the inorganic binder as given above.
• the preform or the like prepared using the mixed powder having a composition as described above may be fired at a temperature of, for example, about 200°C to about 700°C, so that the subsequent operation could be easily performed.
• the firing temperature is desirably set at 700°C or lower so that the metal powder will not be oxidized.
• the firing temperature is desirably set to 500°C or lower so that Mg would not be depleted by oxidation during firing.
• the metal matrix composite can be obtained by well impregnating and filling the porous preform or the like obtained in the manner as described above with the molten aluminum alloy or the like irrespective of using the method of either the high-pressure impregnation or the non-pressurization infiltration.
• the preform or the like is impregnated with a molten aluminum alloy or the like whose temperature is, for example, about 700°C to about 800°C at a pressure of, for example, about 20 MPa to about 200 MPa.
• a pressure of lower than 20 MPa is not preferable because the pressure is too low, so that there may be concern over insufficient impregnation.
• the pressure is higher than 200 MPa, the impregnation is feasible, but a pressure of 200 MPa or lower is enough taking energy cost and life of a pressure vessel into consideration.
• a so-called Lanxide process a mixed powder obtained by adding 0.5 to 10 parts by mass of a Mg powder to 100 parts by mass of the total amount of the fine metal powder and/or the like and the powder of the aluminum alloy or the like needs to be used.
• the molten aluminum alloy or the like is infiltrated without pressurization in, for example, a nitrogen atmosphere at 700°C to 900°C to impregnate the porous preform or the like obtained using the above-described mixed powder, thereby a good metal matrix composite can be obtained.
• the mixture was subjected to firing at 500°C for 2 hours to prepare a molded body (preform) containing the SiC powder and the aluminum alloy powder.
• preform a molded body
• the resulting molded body was placed in a metal mold, a molten A6061 aluminum alloy melted at 750°C was poured therein to impregnate the preform at a pressure of 100 MPa, and thus a composite was cast.
• the composite obtained by the above-described method was an aluminum alloy matrix composite formed of 30% by volume of the SiC fine powder and 70% by volume of the balance.
• a specimen for measurement having a specified size was cut out from the resulting composite, and the flexural strength of the composite was measured using the specimen at room temperature in accordance with JIS R1601. Also in other examples, the flexural strength was measured by the same method. The measurement result was that the flexural strength was 740 MPa, which indicated that the obtained composite had significantly high strength.
• the obtained composite had good processability and was confirmed to be processable with a cemented carbide tool.
• This mixture was subjected to press molding and firing by the same operation as in Example 1 to prepare a molded body (preform).
• a preform having a size of 100 mm ⁇ 100 mm ⁇ 30 mm was cut out from this molded body. Then, as shown in Figure 1 , the preform 1 was impregnated and filled with a molten A6061 aluminum alloy 2 without pressurization to form a composite, and thus an aluminum alloy matrix composite was prepared.
• the preform 1 and the A6061 aluminum alloy 2 were placed in a container 4 made of carbon; this container was placed in a furnace in a nitrogen atmosphere; the temperature was increased at a rate of 100°C/hour and then kept at 780°C for 2 hours; and thereafter the composite was taken out.
• Reference numeral 3 in Figure 1 shows an infiltration path of the same material as the preform 1. The composite taken out was processed for measurement, and the physical property values were measured by the same method as in Example 1.
• the composite obtained in Example 2 was also an aluminum alloy matrix composite composed of 30% by volume of the SiC fine powder and 70% by volume of the aluminum alloy.
• the flexural strength measured by the same method as in Example 1 was 650 MPa, which indicated that the obtained composite was a high-strength composite.
• the obtained composite had good processability and was processable with a cemented carbide tool.
• the physical property values of the composite obtained above were measured to find that the composite was an aluminum alloy matrix composite composed of 20% by volume of the SiC fine powder and 80% by volume of the balance.
• the flexural strength measured by the same method as in Example 1 was 700 MPa, which indicated that the obtained composite was a significantly high-strength composite.
• the obtained composite had good processability and was processable with a cemented carbide tool.
• Example 2 Mixed were 1,200 g of a metal silicon powder having an average particle size of 5 ⁇ m and 200 g of the A6061 aluminum alloy powder having an average particle size of 25 ⁇ m in the same manner as in Example 1; 100 g of a hydrolyzed ethyl silicate solution was added thereto in order that 40 g of SiO 2 might be contained; and the resulting mixture was mixed for 30 minutes.
• a molded body (preform) was prepared using the resulting mixture by the same operation as in Example 1. Then, the resulting preform was impregnated with molten A6061 aluminum alloy at a high pressure by the same operation as in Example 1 to obtain a composite.
• the physical property values of the composite obtained above were measured to find that the composite was an aluminum alloy matrix composite composed of 25% by volume of the silicon powder and 75% by volume of aluminum alloy powder.
• the flexural strength measured by the same method as in Example 1 was 580 MPa, which indicated that the obtained composite had high strength.
• the obtained composite had good processability and was processable with a cemented carbide tool.
• Example 1 To 2,000 g of a SiC powder having an average particle size of 14 ⁇ m, which is larger than the average particle size specified in the present invention, 100 g of a hydrolyzed ethyl silicate solution was added in order that 40 g of SiO 2 might be contained to prepare a preform using the mixed material in the same manner as in Example 1. Then, the resulting preform was impregnated with the molten aluminum alloy which was the same as used in Example 1 to prepare a composite. Comparative Example 1 is different from the present invention in that: the average particle size of the SiC powder is larger than that specified in the present invention; and the aluminum powder and/or the like is not used in the raw material mixture.
• the physical property values of the composite obtained above were measured to find that the obtained composite was a composite composed of 55% by volume of SiC and 45% by volume of the aluminum alloy.
• the flexural strength measured by the same method as in Example 1 was 320 MPa which was about the same as those of general aluminum alloys, and therefore the composite was confirmed not to be a high-strength composite.
• the obtained composite had inferior processability and was not processable with a cemented carbide tool, and therefore the composite was processed with a diamond end mill.
• a composite of the present example was prepared by the same operation as in Example 1 except that a mixture of 1,200 g of a SiC powder having an average particle size of 14 ⁇ m, which is larger than the average particle size specified in the present invention, and 800 g of an A6061 aluminum alloy powder having an average particle size of 25 ⁇ m was used.
• the physical property values of the obtained composite were measured to find that the obtained composite was a composite composed of 28% by volume of SiC and 72% by volume of the aluminum alloy.
• the flexural strength measured by the same method as in Example 1 was 330 MPa which was about the same as those of general aluminum alloys, and therefore the obtained composite was not a high-strength composite.
• the obtained composite had inferior processability and was not processable with a cemented carbide tool, and therefore the composite needed to be processed with a diamond end mill.
• a molded body (preform) was prepared by the same operation as in Example 1 except that a mixture of 1,200 g of a SiC powder having an average particle size of 22 ⁇ m, which is larger than the average particle size specified in the present invention, and 800 g of an A6061 aluminum alloy powder having an average particle size of 25 ⁇ m was used. Then, the molded body (preform) obtained above was impregnated with molten A6061 aluminum alloy by the same operation as in Example 1 to obtain a composite of the present example.
• the physical property values of the obtained composite were measured to find that the obtained composite was an aluminum alloy matrix composite composed of 31% by volume of the SiC powder and 69% by volume of the balance.
• the flexural strength measured by the same method as in Example 1 was 410 MPa, which was lower than those of the composites of Examples 1 to 4 and was about the same as those of general aluminum alloys, and therefore the obtained composite was not a high-strength composite.
• the obtained composite had inferior processability and was only processable with a diamond tool.
• a molded body (preform) was prepared using 1,200 g of a metal silicon powder having an average particle size of 45 ⁇ m, which is larger than the average particle size specified in the present invention, and 800 g of an A6061 aluminum alloy powder having an average particle size of 25 ⁇ m by the same operation as in Example 1, and the preform was impregnated with A6061 aluminum alloy by the same operation as in Example 1 to obtain a composite.
• the physical property values of the obtained composite were measured to find that the obtained composite was a composite composed of 29% by volume of the metal silicon powder having an average particle size of 45 ⁇ m and 71% by volume of A6061 aluminum alloy.
• the flexural strength measured by the same method as in Example 1 was 270 MPa, which indicated that the obtained composite was a low-strength composite.
• a specimen for measurement was cut out from this in the same manner as in Example 1 to measure the flexural strength by the same method as in Example 1.
• the composite obtained above had low strength as low as a flexural strength of 380 MPa and inferior processability, and therefore the composite was only processable with a diamond tool.
• Table 1 shows conditions for preparing the composites of Examples and Comparative Examples and results of evaluations of the obtained composites.
• a composite processable with a cemented carbide tool was rated as "good,” and a composite not processable with a cemented carbide tool and only processable with a diamond tool was rated as “poor.”
• Comparative Example 5 a commercially available composite (commercially available product) of a SiC powder and aluminum metal was used.
• Example 2 the preform was impregnated with the molten aluminum alloy without pressurization.
• the preform was impregnated and filled with the molten aluminum alloy at a high pressure of 100 MPa.

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