JPS62139838A - Production of preform of metallic composite material - Google Patents

Abstract

PURPOSE:To form a preform which contains short fibers such as whiskers with the uniform disposition of uniform sizes by removing coarse parts and fine parts by sizing from the slurry of the above-mentioned short fibers. CONSTITUTION:The short fibers such as whiskers are mixed with a solvent to prepare the slurry. the coarse whiskers, etc., and the fine whiskers, etc., are removed from the slurry in a sizing stage. Such slurry is poured into a preform molding tool and after the liquid is removed, the initial preform is molded by adjusting the volumetric rate of the fibers by pressurization. The resulted initial preform is again mixed with the solvent to prepare the secondary slurry. The secondary slurry is subjected to the pressure reduction in a reduced pressure vessel by which the secondary slurry is defoamed. The defoamed slurry is subjected to liquid removal and drying in the molding tool for the regular preform, by which preform is obtd.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing preforms such as whiskers and short fibers used when manufacturing a metal matrix composite material by an infiltration method. The present invention relates to a method for manufacturing a preform of a metal matrix composite material that is suitable for manufacturing sexual products.

[Technical background of the invention and its problems]

Recently, as one of the new materials, short lengths such as whiskers or 14! Metal M composite materials, which are composites of II, are attracting attention in various fields. In particular, aluminum-based composite materials are expected to be used in a wide range of fields, such as space equipment, robot parts, and automobile parts, because they not only have high strength but also excellent high-temperature properties.

Infiltration methods, powder methods, diffusion methods, and the like are known as methods for manufacturing such gold Ii single-base composite materials. Among these, the infiltration method is a method in which a preform with accumulated whiskers and the like is infiltrated with molten 7-trix metal under pressure, and is suitable for mass production and is being put into practical use in some cases.

Conventionally, the method for producing preforms using this type of infiltration method is to mix whiskers, etc. with a water-soluble solvent to create a slurry, inject the slurry into a mold, and pour it into the mold. Two methods are known: one method is to dry the whiskers, and the other method is to mold the whiskers only by applying pressure without adding much water or the like. Among these methods, in the latter method, only the fiber density near the pressure surface is upper bound, and the 1JAKi density in the part far from the pressure surface is low, which causes the fiber volume fraction to be uneven and the metal-based composite monthly yield to be There are problems such as the strength tends to be non-uniform.

For this reason, the former method of using slurry, which tends to make the fiber volume percentage uniform even if it generally requires some manufacturing time, is often used.

An example of a conventional preform manufacturing method using such slurry such as whiskers will be explained with reference to FIGS. 15 to 17.

Conventionally, as shown in FIG. 15, first, for example, SiC whiskers as a preform material are mixed with a solvent such as water to create a slurry 1. As shown in FIG. 16, after this slurry 1 is injected into a mold 2, it is drained into a lower container 4 by the downward suction action of a vacuum pump 3, and then placed on a filtering material 5 provided at the bottom of the mold 2. No whiskers 6 remain in the wet state. Since the fiber density of the whisker 6 after the liquid removal is small, it is compressed by a pressurizer 7 as shown in FIG. 17 to increase the fiber density to a desired level.

Thereafter, it is dried to obtain a preform for molten matrix metal infiltration.

In addition, if the preform is manufactured only by the series of steps shown in FIGS. 15 to 17, cracks may occur after drying due to the repulsive force inside the preform, so the first step is repeated.
After forming into a slurry as shown in FIG. 5, the liquid is removed as shown in FIG. 16 to produce a preform with repaired cracks.

By the way, the preform manufactured using this method has 7
Metal matrix composites infiltrated with helix metal typically exhibit about four times the tensile strength compared to the matrix metal.

However, in some cases, the metal matrix composite material may break at a lower cart than the matrix metal, resulting in the problem of non-uniform strength of the metal matrix composite material. It was observed that such non-uniformity in strength was more pronounced as the whisker content increased. Therefore, when we examined the fracture surfaces of tensile test specimens that fractured at low loads and fatigue test specimens that fractured at a small number of repetitions, we found that the fracture surfaces were mixed with uniform whiskers 9 in the 7-trix metal 8, as shown in Figure 18. A large number of coarse granular whiskers 10 and unreinforced regions 11 without whiskers were scattered.

In other words, it is well known that high-strength materials generally have high notch acceptability, and if defects exist near the surface, they will break with a very low load or a small number of repetitions. It is thought that the whisker portion and the unreinforced area portion without the whisker become a defect and cause the strength to decrease.

The reason why such coarse whisker parts and whisker reinforced areas appear in the metal It composite shrine 1 is that the state of the whiskers contained in the preform used during infiltration is non-uniform. That is, the first
As shown in FIG. 5, when whisker slurry 1 is made, coarse portions are generated due to the entanglement of whiskers, etc., and these coarse whisker portions remain inside the metal matrix composite material to form the 18th slurry. This results in the formation of coarse granular whiskers 10 in the figure. Also, during preform molding, air bubbles present in the slurry create whisker defects.
When matrix metal is infiltrated into a dried preform having a defective part, only matrix metal exists in the defective part, and the unreinforced part 1 in FIG.
1 will be formed.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its object is to be able to construct a preform for infiltrating a matrix metal with uniformly sized whiskers or short fibers, and to make it possible to form a preform with uniformly sized whiskers or short fibers. In addition, it is possible to have a uniform arrangement without missing parts of whiskers or short fibers, and as a result, coarse whiskers, etc. or unreinforced areas without whiskers, etc. occur in the metal matrix composite material after infiltration. It is an object of the present invention to provide a method for preparing a metal matrix composite material r1, IM 3+5, which can prevent such problems and make the strength of the metal matrix composite material uniform. .

Another object of the present invention is to provide a method for manufacturing a preform of a metal matrix composite moon 1-31, which can reliably form a preform into a predetermined shape without deforming the preform during construction.

[Summary of the invention]

The first invention consists of a step of mixing short fibers such as whiskers with a solvent to create a slurry, a sizing step of removing coarse whiskers, fine whiskers, etc. from the slurry, and a step of molding the slurry after sizing into a preform mold. After injecting and dehydrating,
An initial preform molding process in which the fiber volume ratio is adjusted by pressure, a process in which the initial preform, which has been reduced by 1q, is mixed with a solvent again to make a re-slurry, and the re-slurry is depressurized in a vacuum container. It is equipped with a bubble removal process for removing air bubbles in the re-slurry, and a wood preform molding process in which the re-slurry from which air bubbles have been removed is dehydrated and dried in the present preform mold to form a preform. Features.

The second invention also includes a step of mixing short fibers such as whiskers with a solvent to create a slurry, a sizing step of removing coarse whiskers, fine whiskers, etc. from the slurry, and a step of molding the slurry after sizing into a preform. After pouring into a mold and removing liquid, there is an initial preform molding process in which the fiber volume ratio is adjusted by applying pressure, a process in which the initial preform obtained through this process is mixed with a solvent again to make a reslurry, and a re-slurry process. There is a bubble removal step in which air bubbles are removed from the reslurry by reducing the pressure of the slurry in a vacuum container, and the reslurry from which air bubbles have been removed is deliquified in this preform mold, and whiskers or It is characterized by comprising a shape maintaining step of pressurizing short fibers, and a drying step of drying the short fibers to form a preform.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 14.

This example uses aluminum as a matrix and SiC
A method for manufacturing a SiC whisker briefform, which is used when manufacturing a metal matrix composite material in which whiskers are used as reinforcing fibers, by an infiltration method will be described later.

First, the manufacturing process will be explained with reference to FIGS. 1 to 8.

FIG. 1 shows the slurry production process. 20 faucets on top and bottom
A whisker/water slurry 23 is created by injecting SiC whiskers and water as a solvent into a mixing volume 7521 having the components a and 20b, and sufficiently stirring the mixture using the agitation 122. At this stage, the slurry 23 is in a state where the coarse 1-size squirrels 24 are mixed.

Figure 2 shows the sizing process. In this step, stirring is stopped and the slurry 23 is left standing until it becomes still. At this time, the coarse whiskers 24 sink to the bottom of the mixing container 21 due to the difference in sedimentation speed, and the extremely fine whiskers float in the supernatant liquid 25. Therefore, first, the upper faucet 20a
Listen, on? Remove the humid liquid 25. Thereafter, the slurry 23 containing only appropriate human whiskers is taken out into the receiving container 26 by opening the lower faucet 20b.

The operations shown in FIGS. 1 and 2 are repeated several times. As a result, whisker sizing is performed, and most of the large whiskers and extremely fine whiskers are removed.

Note that the solvent for dissolving whiskers is not limited to water, and organic solvents with low viscosity and low ratio, such as alcohol and acetone, can be used. If such a low viscosity, low specific gravity solvent is used, it is possible to shorten the separation time of the whiskers, and it is also possible to dissolve and remove 'r5 filth impurities contained in the whiskers. It can be done effectively.

FIG. 3 shows the initial preform molding process. That is, the slurry 23 containing uniformly sized whiskers that has been subjected to V+ in the sizing process is injected from the container 26 into the brief A-me mold. A filter material 28 is placed at the bottom of the preform mold 27.
A lower space 29 of the filter material 28 is connected to a vacuum pump 31 via a lower container 30. By driving the vacuum pump 31 after injecting the slurry 23, the solvent 23a in the slurry 23 can be extracted into the lower container 32 through the filtering material 28. In addition, in the J stiff preform mold 27, the IIfa liquid was poured into the mold 27, 11'
Whiskers in the J state remain.

Figure 4 shows the pressurizing process J'. In this pressurizing step, the wet whiskers remaining in the preform mold 27 shown in FIG. This results in
The U and fiber volume ratios of the preform to be molded later are adjusted.

That is, in FIG. 3, the rate of debris accumulation during dehydration is only about 10% (90% is voids). Since it is not possible to obtain a composite material with sufficient strength with this level of fiber volume fraction, the whiskers 33 are pressurized in order to increase the fiber volume fraction beyond this level. The pressing force is set according to the desired fiber volume percentage (for example, when the fiber volume percentage is 15%, set the pressure to 1.
70Kg/cd1 or 700 K9/at 30%
eta)Q Note that in the initial preform obtained in this way, only the fiber volume percentage on the pressurizing side increases, and as it is, it is not possible to obtain a preform with a uniform volume percentage. to make the volume ratio uniform.

Figure 5 shows the reslurry process. In this step, the initial preform obtained in the pressurizing step of FIG. 4 is dissolved in the solvent again, reslurred into a slurry 35, and mixed and stirred by the stirrer 22 in the mixing container 36 in the same manner as in FIG. This aims to equalize the m-body attack rate.

FIG. 6 shows the bubble removal process. In this bubble removal process, the re-slurry 35 shown in FIG. This is to remove the air bubbles 40 that occur.

As the reduced pressure container 37, this preform mold "a" is used for final molding of the preform. That is, this vacuum container 37 which also serves as the main preform mold
This has a filtering material 41 at the bottom almost like the preform mold 27 shown in FIG. 3, and the space 4 below the filtering material 41
2 is connected to a vacuum pump 44 via a lower container 43. In addition, a liquid removal valve 45 for opening/closing adjustment is provided in the communication portion between the lower space 42 and the lower container 43. In addition, an airtight lid 46 is provided on the upper surface of the preform mold 37, and the airtight lid 46 and the vacuum container 44 are connected by a suction vibrator 47, and a pressure reduction adjustment valve 48 is installed on the suction vibrator 47. The above-mentioned pressure reducing means 39 is constituted by the above-mentioned pressure reduction means 39.

Further, the airtight lid 46 is provided with a pipe 49 communicating with the atmosphere.
This atmosphere communication pipe 49 is provided with a leak valve 50 .

When performing the bubble removal action, close the deliquid adjustment valve 45 and the leak valve 50,
is opened, and the vacuum pump 44 suctions air from inside the decompression container 37. At the same time, rotate the stirring IY138. Due to the pressure reduction inside the container 37 that is carried out simultaneously with such stirring of the re-slurry 35, the air bubbles 40 in the slurry 35 expand, and as if receiving a large buoyant force, they gurgle and move inside the re-slurry 35? The instep goes up. In this case, if a decompression effect of about 20 degrees is performed, the bubbles (diameter 0.5
mm or more) was observed to float completely. 4i. Although there is a possibility that extremely small air bubbles may remain in the reslurry 35, by stopping the vacuum pump 44 and listening to the leak valve 50 when the pressure reduction action is completed, they can be removed through the atmospheric communication pipe 49. If the inside of the container 37 is brought back to atmospheric pressure, the volume of the fine bubbles will be calculated by Boyle's law f'llJ (P V
= constant), it is reduced to several hundredths. As seen from the experimental results described below, the presence of such extremely fine bubbles does not pose any particular problem in terms of the strength of the metal matrix composite material to be produced. In order to float the bubbles, it is desirable that the viscosity of the re-slurry 35 be as low as possible, and it has been found that it is effective to perform the stirring 1 intermittently using the lff1 machine 38.

When the bubble removal action is completed, the pressure reduction adjustment valve 48 is closed, the leak valve 50 is turned on to bring the inside of the preform mold 37 to atmospheric pressure, and the liquid removal adjustment valve 45 is turned on to reslurry. Perform step 35 dehydration.

FIG. 7 shows this dewatering process. In this dewatering process, the equipment used in the bubble removal process is used as is. That is,
When the vacuum pump 44 is activated by turning on the liquid removal adjustment valve 45, one adsorbent 51 is extracted into the lower volume S43.

In addition, in this dewatering step, as shown in FIG.
As the second liquid advances (1), the layer of the reslurry 35 gradually decreases, while the whisker precipitate J2 Ft 52 gradually grows. This state is shown enlarged in FIG.

However, if dehydration work is continued in this state, the first
As shown in FIG. 2, the peripheral side of the precipitated layer 52 of the whisker may contract just before the end of liquid removal, creating a gap 53 between it and the main preform mold 37. - When such a gap 53 occurs, the re-slurry 35 on the top of the sediment layer 52
Rather than being sucked downward through the sediment layer 52 (actually, most of it is supernatant liquid), a phenomenon occurs in which it flows out from the surrounding area through the gap 53 as shown by arrow a in Figure 12. . Then, as shown in FIG. 13, the precipitate 52 near the contraction part corresponding to the solvent outflow passage flows out at the same time, causing the preform 54 to be molded to lose its shape, as shown in FIG. It turns out.

Therefore, in order to prevent such damage to the precipitated layer 52, it is desirable to maintain the shape of the precipitated layer 52.

FIG. 8 does not show the shape maintaining process. In this shape maintenance process,
A pressurizer 55 is inserted into the preform mold 37, and the precipitate layer 52 is pressurized downward just before the completion of deliquing, thereby expanding the precipitate layer 52 toward its outer circumference. This prevents the generation of a gap toward the outer circumferential side due to the contraction of 52.

In addition, in order to more effectively maintain this J: shape, it is desirable to add a deflocculant to the solvent of the reslurry 35 to improve leakage and improve the flow of water between the whiskers. If leakage is improved by the deflocculant, the precipitate layer 52
This improves the flow of the solvent within the tank, which is effective in preventing the flow of re-slurry as indicated by the arrow a in FIG. 12 mentioned above.

In addition, as generally known deflocculants, there are those shown in the table below.

The preform obtained in the above manner is the main mold 3.
After taking it out from 7, it is dried at a crystallinity of 50 to 100°C. Thereafter, the brifform is inserted into a mold (not shown), and a 7-trix metal, such as molten aluminum, is poured into the mold to form a metal matrix composite material (+7 It is something that can be done.

FIG. 9 shows the cross-sectional shape of the si'c whisker/Δ) composite material manufactured by the above method.

As shown in FIG. 9, in the 7 trix Kinku 56,
Whiskers 57 of uniform size are evenly arranged and compounded. That is, unlike the metal M composite material Fl using whiskers produced by the conventional manufacturing method (see FIG. 18), there are no coarse whiskers or unreinforced portions without whiskers.

Figure 10 shows a comparison between a metal matrix composite material (SiC whisker/Aj! composite material) using the preform obtained in the above example and one using a preform manufactured by a conventional method, using a tensile test. We have shown the results. In Fig. 10, the horizontal axis is the AM of SiC whiskers.
The volume ratio is shown, and the vertical axis shows the tensile strength. a, a2 are 1
Indicates the average value of the tensile strength of 0 test piece pieces, b , b
indicates its standard deviation. It can be seen that the tensile strength of the preform manufactured by the method of the above example is improved as a whole compared to the preform manufactured by the conventional method. Although the difference between the two provinces is small in the area where the fiber volume percentage is less than 20%,
In areas of high intensity over %, on average 5-10 K3
f/nrtA culm orientation is recognized.

Moreover, it is recognized that the variation V in tensile strength of the sheet based on the above-mentioned example is smaller than that of the sheet based on the conventional example. In particular, when based on conventional examples, the higher the fiber volume fraction, the greater the variation;
When based on the method of the example, the variation is almost constant. This is because, as is clear from the comparison between FIG. 9 and FIG. 18, in the past, the higher the fiber volume fraction, the larger the amount of coarse whiskers, and the more unreinforced portions without whiskers appeared. In the case of the example, it is recognized as 1b based on the fact that there are almost no coarse whiskers or unreinforced parts.

In the above embodiment, as shown in FIG. 8, the precipitated layer 52 was pressed with the ICL end culm of the preform molding to maintain its shape. This is the most desirable method for efficiently molding a preform in a good shape without damaging the shape of the preform, and has the advantage that the entire process can be carried out smoothly.

Therefore, in the shape maintenance process shown in FIG. 8, in addition to preventing the occurrence of coarse whiskers and unreinforced portions without whiskers, a shape maintenance effect is expected.
In order to eliminate the drawback of non-uniform strength due to the conventional preform manufacturing method, the process shown in FIG. 7 can sufficiently achieve the objective.

Similarly, the deflocculant added to the re-slurry in the above example is a means applied to obtain the most desirable effect in the shape maintenance process, and is effective in preventing shape deformation. Similarly, this is an additional effect; for example, if the shape can be maintained by some means, the use of the deflocculant can be omitted.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to "remove coarse parts and fine parts by sizing from short V & dark blue slurry such as whiskers to form a preform containing uniformly sized things in a uniform arrangement. I can do it.

Therefore, it is possible to prevent weak parts such as coarse whiskers from forming in the gold B-base composite material, and since bubbles are removed from the reslurry, whiskers and other parts due to penetration of the metal matrix can be prevented. It is also possible to effectively prevent the occurrence of unreinforced portions that are not reinforced.

Further, according to the second invention, since the preform to be molded is prevented from deforming and is held in a predetermined shape, a perfectly shaped preform can be smoothly manufactured. Effects such as no need for subsequent shape restoration and easier molding operations are achieved.

[Brief explanation of drawings]

FIGS. 1 to 8 are explanatory diagrams illustrating a method for manufacturing a preform of a metal frame composite material according to an embodiment of the present invention in order of culm;
The figure is a schematic diagram showing the cross-sectional shape of a metal matrix composite material using a preform I#7 prepared by the method of Example 11a,
Country 10 is a graph showing the difference in strength between the metal matrix composite materials based on BRIFORM manufactured by the method of the present invention and the conventional method, and FIGS. 11 to 14 are the shapes shown in FIG. 8! Figures 15 to 17 are process diagrams showing the conventional manufacturing method, and Figure 18 is a metal matrix composite material using a preform obtained by the conventional method. FIG. 23...Slurry, 24...Coarse whisker, 25...
・Fine whiskers, 27... Preform mold, 35
. . . Re-slurry, 37 . . . Decompression container and main preform mold, 40 . . Bubbles, 56 . Applicant's agent Hisashi Hatano Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 8 Figure 9 5iC(W)G product-'! ('/,)Figure 10Figure 11Figure 12Figure 13Figure 14Figure 15Figure 16Figure 17Figure 18

Claims (1)

[Claims] 1. A step of mixing short fibers such as whiskers with a solvent to create a slurry, a sizing step of removing coarse whiskers, fine whiskers, etc. from the slurry, and a preform molding of the slurry after sizing. An initial preform molding process in which the fiber volume ratio is adjusted by applying pressure after pouring into a mold and removing liquid;
The initial preform obtained by this process is mixed with a solvent again to make a reslurry, the air bubbles are removed by reducing the pressure of the reslurry in a vacuum container, and the air bubbles are removed. A method for manufacturing a preform for a metal matrix composite material, comprising the steps of: deliquifying and drying the re-slurry in a preform mold to form a preform. 2. A process of mixing short fibers such as whiskers with a solvent to create a slurry, a sizing process of removing coarse whiskers and fine whiskers from the slurry, and a process of pouring the slurry after sizing into a preform mold to remove it. An initial preform molding process in which the fiber volume ratio is adjusted by applying pressure after the liquid is applied;
The initial preform obtained by this process is mixed with a solvent again to make a reslurry, the air bubbles are removed by reducing the pressure of the reslurry in a vacuum container, and the air bubbles are removed. In addition to deliquifying the re-slurry in the preform mold, the process includes a shape maintaining process of pressurizing whiskers or short fibers during the deliquoring process, and a drying process of drying the preform after deliquifying the liquid. A method for manufacturing a preform of a metal matrix composite material, characterized by: 3. The method for producing a preform of a metal matrix composite material according to claim 2, wherein a conditioning liquid such as a deflocculant or a fiber coating agent is added to the solvent.