Patent Application
20080131719
The present invention generally relates to a method for producing an aluminum composite material, and more specifically relates to production of an aluminum composite material excelling in at least one property such as plastic workability thermal conductivity, strength at room temperature or high temperatures, high rigidity, neutron absorbing ability, wear resistance or low thermal expansion.
When using powder metallurgy to produce a composite material having aluminum as the matrix phase, ceramic particles of Al2O3, SiC or B4C, BN, aluminum nitride and silicon nitride are mixed as reinforcing materials into an aluminum powder which forms the matrix phase, then this mixed powder is loaded into a can and cold-pressed or the like, then degassed or sintered to form the desired shape. Sintering methods include methods of simply heating, methods of heating while compressing such as hot-pressing, methods of pressure sintering by hot plastic working such as hot extrusion, hot forging and hot rolling, methods of sintering by passing electricity while compressing, and combinations of these methods. Additionally, the sintering can be performed together with the degassing.
In recent years, aluminum composite materials have been developed, not only for its strength, but for other uses requiring a high Young's modulus, wear resistance, low thermal expansion, and radiation absorbing ability. In general, each function can be increased by increasing the amount of ceramics having the required function, but simply increasing the amounts can cause the plastic workability such as sintering ability, extrusion ability, rolling ability and forging ability to be largely reduced.
Therefore, methods of performing the ceramics, impregnating with an aluminum alloy melt, then evenly dispersing high-concentration ceramics in the matrix phase have been contemplated, but this carries the drawback of possible defects occurring due to inadequate penetration of the melt and shrinkage forming during solidification.
The present invention was made in consideration of the above situation, and has the object of offering a method enabling an aluminum composite material with a high ceramic content, such as 10% by mass, to be easily produced.
Another object of the present invention is to offer a method of producing an aluminum composite material which is more readily subjected to plastic working by cladding an aluminum-ceramic composite material with a metallic plate.
A further object of the present invention is to offer a method of producing an aluminum composite material capable of reliably preventing the generation of cracks or the like when subjecting a clad aluminum-ceramic composite material to rolling.
Yet a further object of the present invention is to offer a method of producing an aluminum composite material capable of achieving a high productivity.
For the purposes of the present specification, aluminum shall refer to aluminum alloys as well as pure aluminum.
Additionally, the production method of the present invention is not limited to the production of aluminum composite materials with a high reinforcing material content, and can just as well be applied to production of aluminum composite alloys having a low reinforcing material content, such as 0.5% by mass.
The method for producing an aluminum composite material according to the present invention is characterized by comprising (a) a step of mixing an aluminum powder and ceramic particles to prepare a mixed material; (b) a step of electric-current pressure sintering said mixed material together with a metallic plate material to form a clad material wherein a sintered compact is covered by a metallic plate material; and (c) a step of subjecting said clad material to plastic working to obtain an aluminum composite material.
Generally, ceramic particles are much harder than aluminum. Therefore, when a sintered compact of an aluminum powder containing large amounts of ceramic particles is plastically worked, the ceramic particles on the surface can be points of origin for damage, and cause cracks to occur in the plastically worked material. Additionally, they can cause wear in extrusion dies, mill rolls, forging dies and the like. However, in the present invention, the plastic working step is preceded by a step of covering the mixed material of aluminum powder and ceramic particles with a metallic plate material, electric-current pressure sintering, then cladding the surface of the ceramic-containing aluminum sintered compact with a metallic plate material, and performing plastic working in that state. With this method, there will be no ceramic particles on the surface that may be the point of origin for damage or wear down dies or the like, thus resulting in good plastic working materials. Additionally, the ceramic-containing aluminum powder is clad by a metallic plate material by means of electric-current pressure sintering, so there is close contact between the ceramic-containing aluminum material and the metallic plate material, thus providing excellent thermal conductivity and electrical conductivity between the ceramic-containing aluminum material and the metallic plate material. Additionally, even if subjected to hot plastic working, defects will not occur between the metallic plate material and the ceramic-containing aluminum material, so there is no need to separate the metallic plate material after hot plastic working.
In a preferred embodiment of the present invention, the aforementioned step (b) includes loading the aforementioned mixed material in a forming die together with a metallic plate material in a state of contact with the metallic plate material, and subjecting to electric-current pressure sintering while compressing with a punch and applying voltage. Here, this may involve sandwiching the mixed material between a pair of metallic plate materials, loading in a forming die with a metallic plate materials being pressed by a punch, and compressing the mixed material together with the metallic plate material, or as an alternative method, placing the mixed powder in a metallic container having a lid plate material opposite a bottom plate material, loading in a forming die with the bottom plate material and lid plate material pressed by a punch, and compressing the mixed material together with the container.
In a further preferred embodiment of the present invention, the aforementioned step (b) may involve preparing at least two assemblies of a mixed material and metallic plate materials and performing the electric-current pressure sintering with the aforementioned at least two assemblies loaded in a forming die in a stacked state, to simultaneously form at least two clad materials, and this method can greatly improve the productivity. Here, a receiving space inside the forming die can be partitioned by at least one partitioning member perpendicular to the punch movement direction to delimit at least two compartments, the aforementioned at least two assemblies being loaded into the aforementioned at least two compartments to perform the electric-current pressure sinter.
In another preferred embodiment of the present invention, the aforementioned metallic plate material is composed of aluminum or stainless steel. Additionally, in the aforementioned step (a), the usual procedure would be to mix an aluminum powder and ceramic particles to prepare a mixed material consisting of a mixed powder, but the mixed material may consist of a compressed formed compact formed by compression forming a mixed powder of an aluminum powder and ceramic particles, for example, by a cold isostatic press (CIP), cold uniaxial press or vibration press, and may be subjected to electric-current pressure sintering beforehand, due to which it becomes easier to sinter during electric-current pressure sintering and easier to handle such as during transport. Additionally, it can be compression formed with a mixed powder loaded into a metallic container or a mixed powder between metallic plate materials.
In vet another embodiment of the present invention, in the aforementioned step (a), the aluminum powder may be an alloy powder is a pure Al powder with a purity of at least 99.0% or an alloy powder containing Al and 0.2-2% by mass of at least one of Mg, Si, Mn and Cr, and the ceramic particles may take up 0.5-60% of the total mass of the mixed material.
In a further preferred embodiment of the present invention, the aforementioned step (b) can involve forming a clad material with peripheral portions covered by a metallic frame material. More preferably, the aforementioned step (b) can involve covering the clad material with a metallic frame material after electric-current pressure sintering. In an alternative method, the peripheral portions of the metallic plate materials and/or the mixed material may be covered by a metallic frame material before electric-current pressure sintering. Here, the aforementioned metallic frame material may be formed by welding, friction stir welding (FSW welding) or the like of a plurality of frame members, or may be a single piece. Preferably, the metallic frame material is a single piece obtained by cutting out the central portion of an aluminum plate material by wire cutting or pressing, or a hollow extruded material cut to an appropriate length.
In a further embodiment of the present invention, the aforementioned step (c) may involve covering the surface of the aforementioned clad material with a metallic protective plate before subjecting to plastic working. Here, the aforementioned protective plate is preferably composed of a material that is malleable, has good high temperature strength, and low thermal conductivity. For example, stainless steel, Cu, soft iron or the like can be used, among which soft iron is most preferable. Additionally the aforementioned step (c) more preferably involves covering the aforementioned clad material with the aforementioned protective plate on the front side in the direction of movement and on the top and bottom surfaces. Furthermore, lubrication is preferably performed between the aforementioned clad material and protective plate such as by solid lubrication using a BN-based lubricant.
Another embodiment of the present invention offers an aluminum composite material produced by one of the above-described methods of producing an aluminum composite material.
The method of producing an aluminum composite material according to the present invention partially or completely resolves the aforementioned drawbacks of conventional methods of producing aluminum composite materials.
In particular, with the method of producing an aluminum composite material according to the present invention, a metallic plate material and a mixed material of an aluminum powder and ceramic particles are together subjected to electric-current pressure sintering before performing plastic working, thus cladding a ceramic-containing aluminum sintered compact with the metallic plate material, as a result of which there are no ceramic particles on the surface that may be points of origin of damage or wear down dies or the like, resulting in a good plastic working material. Additionally, the ceramic-containing aluminum material is clad by a metallic plate material by means of electric-current pressure sintering, so there is close contact between the ceramic-containing aluminum material and the metallic plate material, and excellent thermal conductivity and electrical conductivity between the ceramic-containing aluminum material and the metallic plate material. Additionally defects will not occur between the metallic plate material and the ceramic-containing aluminum material even if plastic working is performed.
Additionally, in a preferred embodiment of the method of producing an aluminum composite material according to the present invention, at least two assemblies of a mixed material and metallic plate materials are simultaneously loaded into a forming die, and subjected to electric-current pressure sintering, thus enabling the efficiency of the sintering step to be raised and greatly improving the productivity of the aluminum composite material.
In further preferred embodiments, the peripheral portions of the clad material are covered by a metallic frame material or the surface of the clad material is covered by a metallic protective plate before performing the rolling procedure, thereby achieving the effect of reliably preventing cracks, fissures and the like from occurring on the surface, interior or sides of the composite material due to plastic working.
Additionally multi-stacked sintering has the effect of allowing the plate thickness to be freely controlled by the use of a spacer.
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1 forming die
2 upper punch member
3 lower punch member
A material receiving portion
4, 5 metallic plate material
6 bottom plate member
9 lid plate member
10 stacked plates
11 assembly
12 spacer
13 partition member
14 container
15 frame material
16, 18 welded portion
17 gap portion
21 protective plate
24 mill roll
The method of production of the present invention is characterized by a step of mixing an aluminum powder and ceramic particles to prepare a mixed material, (b) a step of electric-current pressure sintering said mixed material together with a metallic plate material to form a clad material wherein a sintered compact is covered by a
metallic plate material, and (c) a step of plastic working said clad material to obtain an aluminum composite material, Here below, the raw materials used shall be explained, followed by a detailed explanation of the respective steps in the order of steps (a) through (c).
While the composition of the aluminum powder to form the matrix material of the main body portion is not particularly restricted, it is possible to use various types of alloy powders such as pure aluminum (JIS1050,1070 etc.), Al—Cu alloys (JIS2017 etc.), Al—Mg alloys (JIS5052 etc.), Al—Mg—Si alloys (JIS6061 etc.), Al—Zn—Mg alloys (JIS7075 etc.) and Al—Mn alloys, either alone or as a mixture of two or more.
The composition of the aluminum alloy powder to be selected can be determined in consideration of the desired properties, deformation resistance in subsequent forming steps, amount of ceramic particles mixed, and raw material costs. For example, when wishing to increase the workability or heat dissipation of the aluminum composite material, a pure aluminum powder is preferable. A pure aluminum powder is also advantageous in terms of raw material costs as compared with the case of aluminum alloy powders. As the pure aluminum powder, it is preferable to use one with a purity of at least 99.5% by mass (commercially available pure aluminum powders usually have a purify of at least 99.7% by mass).
Additionally; when wishing to obtain neutron absorbing ability, a boron compound is used as the ceramic particles to be described below, but when wishing to further increase the resulting neutron absorbing ability, it is preferable to add 1-50% by mass of one type of element providing neutron absorbing ability such as hafnium (Hf), samarium (Sm) or gadolinium (Gd) to the aluminum powder. Additionally, when high-temperature strength is required, it is possible to add at least one element chosen from titanium (Ti), vanadium (V), chrome (Cr), manganese (Mn), iron (Fe), copper (Cu), nickel (Ni), molybdenum (Mo), niobium (nb), zirconium (Zr) and strontium (Sr), and when room-temperature strength is required, it is possible to add at least one element chosen from silicon (Si), copper (Cu), magnesium (Mg) and zinc (Zn), at a proportion of 2% by mass or less for each element, and a total of 15% by mass or less.
Furthermore, while the sintering ability must be increased in the present invention, it is preferable to include at least 0.2% by mass of at least one of Mg (magnesium), Cu (copper) or Zn (zinc) in order to fulfill this purpose.
In the above-described aluminum alloy powders, the balance other than the specified ingredients basically consists of aluminum and unavoidable impurities.
While the average particle size of the aluminum powder is not particularly restricted, the powder should generally have an upper limit of 500 μm or less, preferably 150 μm or less and more preferably 60 μm or less. While the lower limit of the average particle size is not particularly limited as long as producible, it should generally be 1 μm or more, preferably 20 μm or more. Additionally, if the particle size distribution of the aluminum powder is made 100 μm or less and the average particle size of the particles of the reinforcing material is made 10 μm or less, then the particles of the reinforcing material will be evenly dispersed, thus greatly reducing the portions where the reinforcing material particles are thin, and providing a property stabilizing effect. Since cracks will tend to occur if plastic working such as extrusion or rolling is performed with a large difference between the average particle size of the aluminum alloy powder and the average particle size of the ceramic particles discussed below, the difference in average particle size should preferably be small. If the average particle size becomes too large, it becomes difficult to achieve an even mixture with ceramic particles whose average particle size cannot be made too large, and if the average particle size becomes too small, the fine aluminum alloy powder can clump together, making it extremely difficult to obtain an even mixture with the ceramic particles. Additionally, by putting the average particle size in this range, it is possible to achieve greater workability, formability and mechanical properties.
For the purposes of the present invention, the average particle size shall refer to the value measured by laser diffraction particle size distribution measurement. The shape of the powder is also not limited, and may be any of teardrop-shaped, spherical, ellipsoid, flake-shaped or irregular.
The method of production of the aluminum powder is not limited, and it may be produced by publicly known methods of production of metallic powders. The method of production can, for example, be by atomization, melt-spinning, rotating disk, rotating electrode or other rapid-cooling solidification method, but an atomization method, particularly a gas atomization method wherein a powder is produced by atomizing a melt is preferable for industrial production.
In the atomization method, the above melt should generally by heated to 700-1200° C., then atomized. By setting the temperature to this range, it is possible to perform atomization more effectively. Additionally, the spray medium/atmosphere for the atomization may be air, nitrogen, argon, helium, carbon dioxide, water or a mixed gas thereof, the spray medium should preferably be air, nitrogen gas or argon gas in view of economic factors.
Examples of the ceramic to be mixed with the aluminum powder to form the main body portion include Al2O3, SiC or B4C, BN, aluminum nitride and silicon nitride. These may be used alone or as a mixture, and selected depending on the intended use of the composite material.
Here, boron (B) has the ability to absorb neutrons, so the aluminum composite material can be used as a neutron-absorbing material if boron-containing ceramic particles are used. In that case, the boron-containing ceramic can be, for example, RC, TiB2, B2O3, FeB or FeB2, used either alone or as a mixture. In particular, it is preferable to use boron carbide B4C which contains large amounts of 10B which is an isotope of B that absorbs neutrons well.
The ceramic particles should be contained in the aforementioned aluminum alloy powder in an amount of 0.5% to 60% by mass, more preferably 5% to 45% by mass. The reason the content should be at least 0.5% by mass is that at less than 0.5% by mass, it is not possible to adequately reinforce the composite material. Additionally, the reason the content should be 60% by mass or less is because if it exceeds 60% by mass, then sintering becomes difficult, the deformation resistance for plastic working becomes high, plastic workability becomes difficult, and the formed article becomes brittle and easily broken. Additionally, the adhesion between the aluminum and ceramic particles becomes poor, and gaps can occur, thus not enabling the desired functions to be obtained and reducing the strength and thermal conductivity. Furthermore, the cutting ability is also reduced.
While the average particle size of the B4C or Al2O3 ceramic particles is arbitrary, it is preferably 1-20 μm. As explained with regard to the average particle size of the aluminum alloy, the difference in particle size between these two types of powders is preferably small. Therefore, the particle size should more preferably be at lease 5 μm and at most 20 μm. If the average particle size is greater than 20 μm, then the teeth of the saw can quickly wear away during cutting, and if the average particle size is smaller than 1 μm (preferably 3 μm), then these fine powders may clump together, making it extremely difficult to achieve an even mixture with the aluminum powder.
For the purposes of the present invention, the average particle size shall refer to the value measured by laser diffraction particle size distribution measurement. The shape of the powder is also not limited, and may be any of teardrop-shaped, spherical, ellipsoid, flake-shaped or irregular.
While the metallic plate material used in the method of production of the present invention may consist of any metal as long as the metal excels in adhesion to the powder material and is suitable for plastic working, it should preferably be of aluminum or stainless steel. For example, in the case of aluminum, pure aluminum (JIS1050, 1070 etc.) can be preferably used, as well as various types of alloy materials such as Al—Cu alloy (JIS2017 etc.), Al—Mg alloy (JIS5052 etc.), Al—Mg—Si alloy (JIS6061 etc.), Ai—Zn—Mg alloy (JIS7075 etc.) and Al—Mn alloy. The composition of the aluminum selected should be determined in consideration of the desired properties, cost and the like. For example, when wishing to improve the workability and heat dissipation ability, pure aluminum is preferable. Pure aluminum is also preferable in terms of raw material cost as compared with aluminum alloys. Additionally, when wishing to improve the strength or workability, an Al—Mg alloy (JIS5052 etc.) is preferable. Furthermore, when wishing to further improve the neutron absorbing ability, it is possible to add preferably 1-50% by mass of at least one element having neutron-absorbing ability; such as Hf, Sm or Gd.
Additionally, as shall be described in detail in connection with the electric-current pressure sintering step below, the metallic plate material may be a pair of metallic plate materials, or a container wherein a lid plate material is combined with a box element comprising a bottom plate material and side plate materials. In the case of a container, a step-shaped mating portion can be formed on the upper edge portions of the box element so as to mate with the peripheral portions of the lid plate element.
An aluminum powder and ceramic particles are prepared, and these powders are uniformly mixed. The aluminum powder may be of one type alone, or may be a mixture of a plurality of types, and the ceramic particles may likewise consist of one type alone or a plurality of types, such as by mixing in B4C and Al2O3. The method of mixture may be a publicly known method, for example, using a mixer such as a V blender or cross-rotary mixer, or a vibrating mill or planetary mill, for a designated time (e.g. 10 minutes to 10 hours). Additionally, the mixture can be performed under dry or wet conditions. Furthermore, media such as alumina balls or the like can be added for the purposes of crushing during mixture.
Step (a) merely concerns preparation of a powder mixture, and the basic process involves sending the powder mixture to the next electric-current pressure sintering step, but in some cases, it is possible to compression form the mixed aluminum powder by subjecting to a cold isostatic press (CIP), cold uniaxial press or vibration press prior to the subsequent electric-current pressure sintering step, and it may further be subjected to electric-current pressure sintering beforehand. By forming a compression formed material instead of using a mixed powder as is, the material becomes easier to sinter during electric-current pressure sintering, as well as becoming easier to handle during transport or the like. Furthermore, the compression formed material can be heated to 200-600° C. and degassed in a reduced pressure atmosphere, an inert atmosphere or a reducing atmosphere.
In step (b), the mixture (mixed powder or mixed compression formed compact) produced in step (a) is loaded into an electric-current pressure sintering device and subjected to electric-current pressure sintering. The electric-current pressure sintering device itself may be of any type as long as capable of performing the designated electric-current pressure sintering, an example being the device shown in the schematic diagram of
That is, in the present invention, the powder material and the metallic plate material are loaded into the material receiving portion A in a state of mutual contact in order to perform electric-current pressure sintering so as to form a clad material wherein a sintered compact is covered with a metallic plate material The electric-current pressure sintering can be performed by conventionally known methods, such as by sealing the vacuum container, putting the inside of the sintering furnace in a reduced pressure state by means of a vacuum pump or the like, loading the vacuum container with an inert gas if needed, activating the upper punch member 2 and lower punch member 3 to compress the material in the forming die 1 with a designated pressure, then passing a DC pulse current through the resulting high-density compress via the upper punch member 2 and the lower punch member 3, to heat and sinter the material. The conditions of electric-current pressure sintering must be selected so that the desired sintering results are achieved, and are determined in accordance with the type of powder being used and the degree of sintering desired. When considering the adhesion between the metallic plate material and sintered compact, and the plastic workability of the clad material which are the basic requirements of the present invention, electric-current pressure sintering in air is possible, but it can be performed, for example, in a vacuum atmosphere of 0.1 torr or less, with an electric current of 5000-30000 A, a temperature increase rate of 10-300° C./minutes, a sintering temperature of 500-650° C., a retention time of at least 5 minutes and a pressure of 5-10 MPa. With a sintering temperature of less than 500° C., it is difficult to achieve adequate sintering, and at more than 650° C., the aluminum powder or aluminum plate material can melt (530-580° C. or less is preferable).
Here, in the present invention, the powder material and metallic plate material are put in a state of mutual contact so as to form a clad material wherein the sintered compact is covered by a metallic plate material, for which the following two embodiments are contemplated and preferred.
That is, in a first embodiment as shown in
In a second embodiment as shown in
A mixture consisting of a mixed aluminum powder or a compression formed compact thereof can be sintered by electric-current pressure sintering according to any of the above methods, while simultaneously being in close contact with the upper and lower metallic plate materials 4, 5, or the bottom plate material 6 and the lid plate material 9 of the container, thus forming a clad material.
Furthermore, in the present invention, the sintering step can be multi-stacked sintering such as two-stacked sintering or three-stacked sintering.
In
Additionally, in a preferred embodiment of the present invention, a clad material whose peripheral portions are covered by a metallic frame material such as an aluminum block material is formed in step (b), so that the load when rolling is applied to the metallic frame material, thus preventing the occurrence of cracks and fissures mostly in the side directions of the clad material. The protection of the clad material due to this metallic frame material may be achieved after electric-current pressure sintering, or before electric-current pressure sintering. It the width a of the frame material 15 is made greater, the frame material 15 is capable of receiving more of the rolling load, thus better preventing cracks or fissures in the clad material, so the width a of the frame material 15 should preferably be at least 5 mm. It should more preferably by at least 20 mm. Additionally, if the frame material 15 is composed of the same metal as the metallic plate materials and the metallic container, they will be better joined, and there will be less difference in the amount of deformation of the composition during rolling.
Furthermore,
Additionally, as shown in
The electric-current pressure sintered compact is generally subjected to hot plastic working such as hot extrusion, hot rolling or hot forging, thus further improving the pressure sintering while simultaneously achieving the desired shape. When preparing a plate-shaped clad material, it is possible to obtain a clad plate material having a designated clad ratio with an Al plate material or an Al container by cold rolling alone. The hot plastic working may consist of a single procedure, or may be a combination of a plurality of procedures. Additionally, cold plastic working may be performed after hot plastic working. In the case of cold plastic working, the material can be made easier to work by annealing at 100-530° C. (preferably 400-520° C.) prior to working.
Since the sintered compact is clad by a metallic plate material, the surface will not have any ceramic particles that might otherwise be a point of origin for damage during plastic working or wear down the dies or the like. As a result, it is possible to obtain an aluminum composite material with good plastic workability, excelling in strength and surface properties. Additionally the resulting material which has been subjected to hot plastic working will have a surface dad with a metal, with good adhesion between the metal on the surface and the aluminum sintered compact inside, thus having corrosion resistance, impact resistance and thermal conductivity superior to aluminum composite materials whose surfaces are not clad with a metallic material.
In a preferred embodiment of the rolling process, the surface of the clad material is covered by a metallic protective plate such as a thin plate of stainless steel, Cu or soft iron prior to roiling. As a result, it is possible to prevent separation between the sintered material and the metallic plate material that can occur due to friction between the roller and the metallic plate material during rolling(especially the initial stages).
Herebelow, the method of production of the present invention shall be described in detail with reference to the examples.
The methods for measuring the respective physical values described in the examples are as follows.
An analysis was performed by ICP emission spectrometry.
A Microtrac (Nikkiso) was used to perform laser diffraction type particle size distribution measurement. The average particle size was the volume-based median.
Samples were evaluated for the presence of cracks and the surface properties when rolling. Those having surface cracks on the plate surface were rated “×”, those having no surface cracks but wrinkle-like irregularities were rated “◯” and those without any surface cracks or irregularities were rated “⊚”.
A small piece cut from a sample was implanted in a resin, emery-polished and buff-polished, then its structure was observed by an optical microscope.
An EPMA device was used to study the Mg distribution in the sample used for structure observation.
A B4C ceramic powder was evenly mixed into an aluminum alloy powder with the composition shown in Table 1, so as to take up 35% by mass. Then, containers of length 100 mm×width 100 mm×height 5 mm consisting of aluminum alloys JIS 5052 and JIS 1050 with a plate thickness of 0.5 mm were prepared, and loaded into an electric-current pressure sintering device with the aforementioned mixed powder inside the containers, then electric-current pressure sintering was performed by applying a voltage (electric current 7000 A) in a vacuum atmosphere (0.1 torr). Here, the sintering temperature was 520-550° C., the retention time was 20 minutes, the temperature increase rate was 20° C./minute, and the pressure was 7 MPa.
Test pieces were taken from the resulting sintered material, and their metallic structure was observed using an optical microscope. The microscope photographs are shown in
Furthermore, the test piece used in the structure observation was subjected to line analysis for Mg content using an EPMA device. The results are shown in
Next, the obtained sintered compact was cold rolled to a plate thickness of 2 mm.
As a comparative example, a sample obtained by electric-current pressure sintering a powder without placing in a container was cold rolled (the remaining composition and production conditions were the same). However, cracks and gouges occurred on the surface, so a rolled material was not able to be obtained. Therefore, the strength and corrosion resistance of the sintered material were studied. The results are also shown in the below Table 2.
Table 2 shows that while the examples of the present invention excel in strength and corrosion resistance as well as having good rolling ability, the comparative example is inferior to the examples of the present invention for all properties, and cracks during rolling.
B4C ceramic powder was mixed into an aluminum alloy powder of the composition shown in Table 1, so as to take up 43% by mass. Then, the mixed powder was placed in a pure aluminum (JIS 1050) cylindrical container (φ 100 mm; plate thickness 2 mm), and electric-current pressure sintering was performed under the conditions described in Example 1.
Next, the resulting sintered material was heated to 480° C., and hot extruded into a flat plate of thickness 6 mm×40 mm.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-378938 | Dec 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/24102 | 12/28/2005 | WO | 00 | 10/12/2007 |
