JPS63303019A - Production of preform for metal base composite material - Google Patents

Abstract

PURPOSE:To produce a preform for metal base composite material without developing any defect by compacting an integrated body of reinforced fiber composing of outer circumferential part of fiber group for reinforcing bound with binder and center part of high quality reinforced fiber group. CONSTITUTION:The integrated body of reinforced fiber composing of whiskers of SiC, etc., and the other staples is compacted to the prescribed volume ratio to obtain the preform for impregnating into matrix metal. Then, this partition cylinder 14 is inserted in a forming die 11 having long cylindrical shape and the SiC whiskers 20 bound with the binder around thereof and the top and bottom parts thereof, and the high quality whiskers 21 in the center part of the die 11 are charged. Next, the above partition cylinder 14 is pulled out upward. After that, the above reinforced fiber integrating body is compacted in the forming die 11 from upper and lower sides with pressurized pistons 12, 17. By this method, the preform, which can form the reinforced forming material without developing any crack at the time of forming and any defect at the time of compositing by high pressure casting, is obtd.

Description

Detailed Description of the Invention (Objective of the Invention) (Industrial Application Field) The present invention is directed to the manufacture of metal 1! composite materials by high-pressure casting (infiltration).
The present invention relates to a method for manufacturing a preform made of lIl1, etc., and particularly to a method for manufacturing a preform for a metal matrix composite material suitable for manufacturing reliable products.

(Prior Art) Metal matrix composite materials in which short aiIff such as whiskers or long fibers are composited in a matrix metal are attracting attention in various fields. In particular, aluminum (AJ)-based composite materials are durable, highly durable, and have excellent high-temperature properties, so they are used in a wide range of fields such as space equipment, robots, and automatic parts.

As methods for manufacturing this metal matrix composite material, PI dipping method, powder method, diffusion method, etc. are known. Among these, the infiltration method is a method in which a preform in which reinforcing fibers such as whiskers are accumulated is impregnated with matrix metal melt under pressure, and is suitable for mass production and has been put into practical use in some cases.

Conventionally, the method for manufacturing preforms used in such infiltration methods is to mix whiskers, etc. with a solvent such as water to create a slurry, inject the slurry into a mold, and remove the liquid inside the mold. A so-called slurry method in which the material is dried and a so-called press method in which a small amount of a solvent such as water is added to whiskers and the like are molded under pressure are known. Of these methods,
Although the latter pressing method has the problem of non-uniformity in that the I1m density near the pressurizing surface is higher than in areas farther from the pressurizing surface, the production time is extremely short and it is more efficient than the former slurry method. This is a great method.

By the way, in order to improve the quality of lightweight reinforced materials, it is necessary to remove impurities and cluster-like lumps (so-called lumps) contained in reinforced uAN, as well as fine powder with a small length-to-thickness ratio (aspect ratio). This is desirable.

However, when such impurities, especially lumps, are reduced, the slipping properties of the reinforcing fibers increase, and the compressive strength of the preform becomes extremely low. Furthermore, the compressive strength of the preform is also reduced by removing impurities that can act as a binder that binds the Il fibers together. For this reason, when molding a preform using a press method using a preform with few lumps and impurities, the increase in WJ debonding of the fibers and the decrease in the bonding force between fibers makes it difficult for the press to remove the pressurized load. The amount of springback in renovation increases. Therefore, due to the difference in the amount of springback caused by the difference in fiber volume fraction at a position away from the vicinity of the pressurizing part, cracks 2 frequently occur on the outer surface of the preform 1, as shown in FIG. 4, for example. There is. This tendency becomes more pronounced as the 88 volume ratio increases.

On the other hand, when a preform with few impurities is used, due to a decrease in the compressive strength of the preform, significant deformation or cracking occurs in the preform during the process of impregnating the preform with matrix metal by high-pressure casting. Material molded articles may contain unreinforced portions in which reinforcing fibers are not present.

FIG. 5 shows a rod-shaped molded product, a so-called molded billet, including such an unreinforced portion.

The composite portion 4 reinforced with the whiskers 3 is divided by cracks in the preform, resulting in an unreinforced portion 5 of only the matrix metal without the whiskers 3.

(Problems to be Solved by the Invention) Conventionally, when manufacturing fiber-reinforced metal matrix composite materials by high-pressure casting, using I11/Ii from which impurities etc. have been removed, cracks may occur in the preform during preform molding. However, due to the low compressive strength of the preform, large deformations and cracks occur during the matrix impregnation stage, resulting in defects such as unreinforced parts in the molded product.

The present invention has been made in view of these circumstances, and even when reinforcing fibers with large JfJ debonding properties and low IIH bonding properties are used, cracks can be prevented during preform molding. Another object of the present invention is to provide a method for manufacturing a preform for a gold B-based composite material, which can produce a reinforced molded product that does not have defects such as unreinforced portions during composite formation by high-pressure casting.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a method for manufacturing a preform for matrix metal impregnation by compressing and forming an aggregate of reinforcing fibers containing whiskers and other miscellaneous materials to a predetermined volume ratio. The properties of the reinforced van aggregate are different between the outer circumferential part and the inner part, and the outer circumferential aggregate is made of reinforcing mII group in which reinforcing fibers are bonded with a binder, and the inner part is reinforced with less impurities! A high-grade fiber group filled with 11fi, both aJ
By compression molding the entire aggregate consisting of AH groups,
The method is characterized in that a preform with a predetermined volume ratio is manufactured.

(Function) By configuring the outer periphery of the preform with a binder-added aggregate, the fiber bonding force at the outer periphery of the preform is increased, and a preform with a high quality of whiskers, etc., with few impurities or lumps can be produced by the pressing method. Even when molding, the pullback is small and the compressive strength is small, which prevents cracks in the preform surface layer and cracks in the preform during the compounding process.

Furthermore, it is also possible to prevent the preform from cracking due to vibration, WJ impact, etc. during transportation of the preform. Furthermore, it is possible to prevent micro-cracks in the surface layer of the preform that occur during long-term storage, and also to eliminate the factors that cause large-scale cracks that occur during the later compounding process by high-pressure casting. .

(Example) An example of the present invention will be described below with reference to FIGS. 1 to 3. In addition, in this example, SiC was used as the reinforcing fiber.
This is about the case where a preform formed using a whisker is impregnated with A1 alloy (6061A) as a matrix metal under pressure.

FIGS. 1(A) to 1([) sequentially show the manufacturing process of the preform.

The molding of the 5iCC Quisca preform is carried out by a two-way press method. That is, a pressure piston 12 is inserted from the bottom of the preform mold 11 into a vertically long cylindrical shape, a thin partition cylinder 14 is inserted from the top, and the pressure piston 12 (FIG. 1(A)).

Next, an aqueous solution containing a silica (Si02)-based binder (for example, trade name [Snowtex-xsJ)] is applied to SiC.
In addition to a small amount of whiskers, SiC whiskers 20 with binder added and stirred uniformly are packed between the preform mold 11 and the partition circle IP114, and SiC whiskers 21 without binder are added to the inside of the partition circle fil 14. (Figure 1 (B)). This SiC whisker 21 is initially 5
% of 5i02 present on the surface, for example, by cleaning with hydrofluoric acid, 5i02ffi is reduced to 1i1.
It is of high quality and has been reduced to about 0.

Next, the SiC whisker holding ring 15 is fitted to the upper end of the preform mold 1, and the holding ring 1
5, press the SiC whisker 21 from the inner circumferential side of the piston 16.
Press the partition circle fi 14 with the preform mold 1.
1 and pull it upward (Fig. 1 (C)).

After that, a pressure piston 17 with a large cross-sectional area is attached to the upper part of the preform mold 11, and a SiC whisker 20.2 is attached to the upper part of the preform mold 11.
1 is the predetermined J! Compression molding until the volume ratio is reached (first stage)
Figure (D)). After molding, the SiC whisker preform 23 is taken out from the preform mold using one of the pressure pistons (FIG. 1(E)).

Then, the moisture inside the preform 23 is removed using a dryer, and the outside of the cylindrical preform is coated with binder-added S.
Obtain a preform reinforced with iC whiskers.

Figure 2 shows l#! 1 shows the results of investigating compressive deformation and fracture strength of a preform with a volume ratio of 20%. That is, the height of the preform is Lo, and the diameter is D (2L0
), and the thickness of the reinforcing part on the outer periphery of the preform is t. Then, the relationship between the amount of shrinkage ΔL due to the load W and the pressure was investigated for a plurality of samples in which α was variously changed. As a result, the buckling strength (
It was found that as the thickness t of the reinforced part with binder added increased, the instantaneous strength and shrinkage rigidity increased while the pressure) was 10 Kgf/- or less.

Next, a method for manufacturing a composite material using the preform 23 manufactured in this way will be explained with reference to FIG. First, the preform 23 is set in a high-pressure casting mold 31, and heated by the heater 32 from the outer circumferential side of the mold 31 (FIG. 3(A)). Whole preform 23 a! degree is 600~6
The temperature is maintained at 50°C for 30 to 40 minutes, and then the AI alloy 33 at about 800°C is injected into the mold 31, and the AJ alloy'/Q33 is pressurized by the pressurizing piston 34.

In this case, the maximum pressing force is equal to or less than the buckling compressive stress of the preform shown in FIG. When it is determined that the pressurizing piston 34 has stably stopped at a predetermined stroke and that the molten metal 33 has impregnated the entire preform 23 to form a composite, the maximum pressure is increased to 50 to eliminate unimpregnated areas (voids) of the A1 alloy.
Hold at 0-100100O/- for 5-10 minutes,
The mold 31 is cooled down. Thereafter, a billet 35 of an A1 alloy (6061AJ)-based composite material reinforced with SiC whiskers is obtained from the mold 31 (FIG. 3(B)).

In the billet 35 formed in this way, if the pressure applied by the pressure piston 34 is greater than the buckling pressure of the preform 23, the preform will crack at the upper part of the billet 35, and the unreinforced portion that does not contain SiC whiskers will be formed. exist. On the other hand, if the pressing force is lowered to prevent this cracking, A
7 alloy 1ii33 not only does not impregnate the lowest part of the preform 23, but also there are many unimpregnated parts outside of that area. This is because a low pressure cannot provide sufficient pressure to overcome the surface tension of the A-alloy melt and penetrate into each substance of the complex intersecting portions of whiskers.

In this way, when a large number of voids exist, not only the tensile strength but also the fatigue and creep properties are poor, and even the strength properties of the A1 alloy, which is the matrix metal, cannot be obtained.

For these reasons, the higher the pressure applied by the pressure piston 34, the more preferable it is, but judging from the results of numerous experiments, a minimum pressure of 30 to 40 KIf/- is necessary.

The table below compares the tensile strength test results for each material.

(■): Impregnation pressure 1ONfff/ad (If): , 50 to 9 f/d The impregnation pressure of molten metal A is 10 Kgf for the T6 heat-treated material of 6061Al, which is a matrix metal, and the A1 base composite molded product of this example.
/- (S i CW/6061A!!-T6 (
n)), and one in which the outer periphery of the preform is reinforced and the pressure is 50 Ky f /- (SiCW/60
61AJ-T6 (I[)), the characteristics of each composite material are listed.

As is clear from the table above, the rough molded product (I) has a large variation in strength and is not much different from the matrix metal, but the rough molded product (■) with increased impregnation pressure has a strength of 6061AI alloy reinforced with SIC whiskers. Values close to the original characteristics have been obtained.

Note that adding a binder that binds the reinforced oIM may cause cluster-like lumps (clumps) in whiskers, etc., which may reduce the quality, especially the strength, of the composite part. Since the additive accumulation is only at the outer peripheral part of the preform, this part can be removed after composite formation to obtain a high quality metal matrix composite material.

Furthermore, depending on the type of binder used, it may react with the matrix metal and cause segregation reactions between metal elements, but according to the present invention, it is possible to minimize such reaction areas. Become.

In the above embodiments, SiC whiskers were used as the reinforcing material, but whiskers made of various other materials, short IIN
It goes without saying that the present invention can also be applied to the production of preforms for gold-Ti 14-base composite materials using, etc.

〔Effect of the invention〕

As described above, according to the present invention, by using a preform whose outer periphery is reinforced with reinforcing fibers containing a binder,
It is possible to prevent cracks during preform molding, enable long-term storage, and prevent cracks during preform transportation.

In addition, it is possible to prevent the preform from cracking during the composite process by high-pressure casting, and it is also possible to prevent the occurrence of unreinforced portions due to deformation, cracking, etc. of the preform.

Furthermore, in line with the demand for higher quality, by using reinforcing fibers with less impurities inside, metal matrix composite materials with no material defects and excellent static and dynamic strength characteristics can be manufactured.

[Brief explanation of the drawing]

1(A) to (E) are process diagrams showing one embodiment of the present invention, FIG. 2 is a graph showing compression deformation characteristics of a preform according to the same embodiment, and FIG. 3(A). (B) is a diagram showing the composite process using the preform according to the same example, Figure 4 is a diagram showing cracks in the surface layer of the preform molded by the conventional method, and Figure 5 is a diagram showing cracks in the composite molded product. It is a figure showing a state. 20... Whiskers combined with a binder, 21...
High quality whisker, 23... preform. (A) (B)
(C)↓ ↑ (D) (E) Figure 1 o 5 10
Figure 2

Claims (1)

[Claims] In a method for manufacturing a preform for matrix metal impregnation by compressing and forming an aggregate of reinforcing fibers consisting of whiskers and other short fibers to a predetermined volume ratio, The outer peripheral part of the aggregate is a reinforcing fiber group in which reinforcing fibers are bonded with a binder, and the inner part is a high-grade fiber group filled with reinforcing fibers with few impurities, and the entire aggregate consisting of these two fiber groups is 1. A method for manufacturing a preform for a metal matrix composite material, the method comprising manufacturing a preform having a predetermined volume ratio by compression molding.