JPS63259039A - Manufacture of metal-base composite material - Google Patents

Abstract

PURPOSE:To obtain a metal-base composite material in high yield, by previously coating a preformed body consisting ceramics fibers, etc., with a material having a melting point lower than that of the above preformed body and by forming the preformed body by diffusion joining so as to improve strength and also to inhibit shrinkage and prevent breakage at the time of pressure infiltration with molten-metal matrix. CONSTITUTION:The surface of a reinforcement constituting a preformed body and consisting of ceramics fibers, whiskers, or grains is coated with a material having a melting point lower than the melting points of the principal components of the reinforcement. Subsequently, at the time of forming the preformed body out of the coated reinforcement, the reinforcement is subjected to diffusion joining at a relatively low temp. by means of heating at a temp. of the melting point of the above-mentioned material or above. Accordingly, the deformation, shrinkage, cracking, etc., of the preformed body are not caused at the time of subjecting the above-mentioned reinforcement to pressure impregnation with molten-metal matrix, and the metal-base composite material in which the reinforcement is uniformly disposed can be obtained.

Description

Detailed Description of the Invention (Objective of the Invention) (Industrial Application Field) The present invention is directed to manufacturing a metal matrix composite material by pressurizing and impregnating a preformed body made of ceramic fibers, whiskers, or particles with molten metal. In particular, the present invention relates to a method for manufacturing a metal matrix composite material in which the buckling strength of a preform is improved.

(Prior Art) So-called fiber-reinforced metal matrix composite materials to which ceramic fibers, whiskers, or particles, such as S t C, A1203, etc. are added, have been known. This metal matrix composite material has excellent strength, heat resistance, wear resistance, etc. Among them, aluminum (Aj+) matrix composite material is partially put into practical use in space equipment, robots, automobile parts, etc.

Methods for producing metal matrix composite materials can be roughly divided into infiltration methods, powder methods, and diffusion bonding methods. In particular, infiltration methods are suitable for mass production because they can produce a large number of complex-shaped members at once.

The infiltration method involves adding a reinforcing material to molten metal, which serves as a matrix, and then casting it.The other method involves forming a preform with the reinforcing material in a shape similar to the actual product, and then applying high pressure to the reinforcing material. It can be divided into methods of impregnation with molten metal. The former has a simpler manufacturing process than the latter, but it is difficult to obtain a high volume fraction (Vf) of the reinforcement due to wettability between the reinforcement and the molten metal. As the contact time increases, the reinforcing material deteriorates and the strength of the composite material tends to decrease. For this reason, the latter method is generally considered to be more effective.

This latter manufacturing process will be explained with reference to FIGS. 10(a) to (e).

First, ceramics 4! A predetermined amount of water 2 is added as an adjustment liquid to the reinforcing material 1 such as fibers and whiskers, and the mixture is thoroughly mixed with a stirrer 3 (FIG. 10(a)).

This mixed liquid 4 is placed in a mold 5, pressurized with a piston 6 to remove water, and compression molded to obtain a preformed body 7 (
Figure (b)). At this time, the volume fraction of the reinforcing material can be adjusted to any desired value by adjusting the molding pressure angle. After sufficiently drying this preform 7, it is set in a mold 8 and heated to 400 to 700°C with a heater 9 (FIG. 2(C)), after which molten metal 10 as a matrix is poured into the mold 8. The preformed body 7 is dried and pressurized with the piston 11.
((d) in the same figure) to obtain a composite material 12 ((e) in the same figure).

In this case, the pressing force for impregnating the preform 7 with the molten metal 10 is set to 100 to 1000 atmospheres depending on the volume ratio of the reinforcing material, the mold 8, the temperature of the molten metal, and the like. In addition, in order to reduce material defects due to the occurrence of pores, etc., 300
Atmospheric pressure or higher is desirable.

By the way, looking at the fiber morphology in the preformed body 7, the 11th
As schematically shown in Figures (a) and (b), 48M7a
, 7b, and 7c are only in contact with each other, and there is no special bonding force between the fibers, and the deformation resistance of the preform 7 against the compressive load is! It depends only on the ``frictional force'' and ``entanglement'' between the a-fibers.

When the buckling strength of such a preformed body 7 was investigated, it was found that it was 5.
The pressure is only about 80 atm, which is below the desired infiltration pressure (3
00 atm).

For this reason, when a metal matrix composite material was manufactured by the manufacturing process shown in FIG. 10, the preform 7 would shrink due to pressure during infiltration, and if the shrinkage was significant, the preform would often crack. . Furthermore, shrinkage of the preform during infiltration not only makes it difficult to adjust the volume fraction of the reinforcing material, but also makes it difficult to create a preform with a shape close to the actual product, which is ideal for infiltration and compounding. It becomes impossible to manufacture such parts.

Therefore, various methods have been attempted to improve the compressive strength of the preform, such as adding a metal binder. However, this method has the disadvantage of reducing the strength of the resulting composite material.

(Problems to be Solved by the Invention) In the conventional manufacturing method of metal matrix composite materials, the constituent reinforcing materials of the preform are simply brought into polymeric contact with each other, so the compressive strength of the preform is low; Shrinkage or breakage during pressurized infiltration of the t8 melt matrix, resulting in a decrease in yield;
There were problems such as deterioration of product quality.

The present invention has been made in view of the above circumstances, and it improves the strength of the preform without reducing the strength of the metal matrix composite material, and prevents shrinkage and damage of the preform during infiltration. It is an object of the present invention to provide a method for manufacturing metal matrix composite materials that can produce metal matrix composite materials of up to 8 quality with good yield.

[Structure of the invention]

(Means for Solving the Problems) The present invention involves compressing a reinforcing material made of ceramics, whiskers, or particles to form a preformed body having a shape similar to that of a product, and adding molten metal as a matrix to this preformed body. In a method for producing a metal matrix composite material in which a fiber-reinforced metal matrix composite material is obtained by pressure impregnation of the reinforcing material, the surface of the reinforcing material is coated with a substance having a melting point lower than that of the reinforcing material components in advance at the material stage, The reinforcing material is heated at a temperature equal to or higher than the melting point of the coating material during compression for forming the preform.

(Function) As a result of various studies on improving the buckling strength of the preform, the inventors found that the preform was heated to 1300 to 2000°C in a vacuum or an inert gas atmosphere, and the contact points between the reinforcing materials were diffusion bonded. It has been found that buckling strength can be significantly improved by doing so. However, firing at a temperature close to 1500°C poses a problem in terms of workability, and we further investigated obtaining higher compressive strength at a lower temperature.

According to the present invention, the surface of the reinforcing material constituting the preform is coated with a substance having a melting point lower than that of the main component of the reinforcing material, and the reinforcing material is heated at a temperature equal to or higher than the melting point of the material when forming the preform. Because of the heating, the reinforcement can be diffusion bonded at relatively low temperatures.

In other words, the surface of the reinforcing material is easily sintered by the coating material with a low melting point, and diffusion bonding can be performed at a lower temperature and in a shorter time than in the case of sintering the reinforcing material itself, which generally has a high melting point. The bending strength is also sufficiently improved.

Therefore, when pressurizing and impregnating the molten metal matrix, deformation, shrinkage, cracking, etc. of the preform do not occur, and a metal matrix composite material in which the reinforcing material is uniformly arranged can be easily obtained.

(Example) Hereinafter, as an example of the present invention, SiC whisker reinforced A1
A method for manufacturing an alloy composite material will be described with reference to FIGS. 1 to 9.

First, the manufacturing process of the preform will be explained with reference to FIGS. 1(a) to 1(d). As shown in FIG. 1(a), SiC whiskers 21 are placed in a ceramic container 22 and heated to 600 to 1200°C in an electric furnace 23 to form a layer of oxide, that is, 3i02, on the surface of the SiC whiskers. . Next, a predetermined amount of a solvent 25 such as alcohol is added to the oxidized SiC whiskers 24, and the mixture is thoroughly stirred and mixed using a stirrer 26 or the like (FIG. 2(b)). Mixed powder 2 thus obtained
7 is put into the mold 28 and pressed from both the upper and lower directions using the press If129, and at the same time heated by the heater 30 disposed around the mold 28 (FIG. 2(C)). Note that when this heating is performed in the air, 5i02 on the SiC whisker surface
Since the 5i02 layer will grow excessively and the 5i02 layer will decompose if the heating is carried out under high vacuum, the oxygen partial pressure of the heating atmosphere should be appropriately adjusted.

In this way, after heating and pressurizing for a predetermined period of time, it is cooled to obtain a preformed body 31 having a desired shape and fiber volume ratio (FIG. 3(d)).

FIG. 2 shows the relationship between the 5i02 glue formed on the SiC whisker surface and the heating time.

Formation of SiO2 was observed even when heated to 600°C, and 100°C
It rises rapidly when it exceeds 0°C. Moreover, the production rate is very fast, about 10% at 1000° C. for 10 minutes.

Figure 3 shows the 5i02 min and the buckling strength of the preform when heated at 1000°C; the more 3i02, the more
The buckling strength of the preform is improved, but with 10% SiO2
Above, it becomes almost constant.

If too much SiO2 is formed on the SiC whisker surface, the cross-sectional area of the SiC whisker decreases and the strength decreases, so it is preferable that the SiO2 cover the SiC whisker surface thinly. Specifically, S i 02 ffl is desirably 10% or less.

From the above results, it is desirable to perform oxide treatment at 1000° C. for about 10 minutes as the conditions for forming oxides on the SiC surface. Figure 4 shows the results of fabricating preforms using SiC whiskers oxidized under these conditions and SIC whiskers without oxidation treatment, and measuring the sintering temperature and buckling strength of the preforms. show. It is recognized that the buckling strength of a preformed body sintered at 1000 to 1200° C. using whiskers that have been oxidized in advance is about 20 times higher than when whiskers that have not been oxidized are used.

It can be seen that even in the case without oxidation treatment, the strength is improved by sintering if heated at the time of forming the preform, but the strength is only about 1/4 of that with oxidation treatment.

In the preformed body manufactured by the method of the above example, each constituent fiber l is shown schematically in FIG. 5(a).
ff31a, 31b, 31c are the same oxide layer 3 on the surface
They are integrated by a diffusion reaction via 2, and the strength of the preform is improved. On the other hand, when sintering is performed without oxidation treatment, as shown in FIG.
ff131' a.

There is no oxide layer at the contact points of 31'b and 31'C,
Since the oxide layer 32' is formed only in areas other than the contact points and the sintering reaction only occurs in those areas, its compressive strength is low.

Figure 6 shows the results of measuring the buckling strength of a preform that was subjected to oxidation treatment J3 and sintering at 1000°C with varying SiC whisker volume fractions, and a preform that was only compression molded using the conventional method. It shows. It can be seen that the buckling strength of the method of the present invention is 4 to 8 times higher than that of the conventional method of laminating and bonding.

FIG. 7 shows a preform obtained by infiltrating and compounding with molten A1 alloy using the 3iC Wiss-forced compact sintered according to the above embodiment and the unsintered preform formed by the conventional method. The results of measuring the degree of shrinkage are shown. SiC on the horizontal axis
The whisker volume fraction is plotted on the vertical axis as the shrinkage rate, that is, the ratio of the height of the preform shrunk due to infiltration to the height of the preform before infiltration. From this result, according to the method of this example for sintering the preform, the shrinkage of the preform during infiltration is reduced to 1/1/2 at any m-male volume fraction compared to the conventional unsintered case. It is recognized that it can be reduced to 3 or less. In addition, because the shrinkage rate has been reduced, there will be no cracking in the preform during infiltration, improving the number of turns and making the preform approximate the shape of the actual product, so-called "Near Net 5hape". It will also be possible to manufacture the desired parts.

Further, FIG. 8 shows a metal matrix composite material (20% reinforced with SiC whiskers) as a final product manufactured by the method of the above example.
24A1 alloy), its tensile strength was compared with that obtained by the conventional method. It is recognized that the tensile strength of the above-mentioned examples is improved compared to that obtained by the conventional method even in preforms having various volume ratios.

In the above example, by heating the SiC whiskers in advance, 5102, which is a SiM compound, is used as the coating material.
However, the present invention is not limited to this, and can be applied to various ceramics! This can be carried out by forming an oxide, nitride, carbide, or silicide on the surface of IN, whiskers, and particles in advance. Specific examples are shown in the table below.

[Margin below]

The coating material is not limited to the reaction product of the reinforcing material component itself as mentioned above, but also plating, chemical vapor stone (CVD), etc.
), or may be formed by coating the reinforcing material component or other components of pure metal, alloy, or oxide by thermal spraying or the like.

For example, Si is known under the trade name "Atron".

It is also possible to form a coating of oxides of these metals by immersing the m-fibers in a solution containing metal alkoxides such as Ti, Zr, Ta, etc. as main components and hydrolyzing them. - For example, when SiC whiskers are used as a reinforcing material, a coating of T i 02 is formed on the surface thereof.

In addition, when TiO2 is formed on the surface of SiC whiskers, depending on the alloy system that becomes the matrix to be strengthened, the alloy components may react with oxides on the surface of the reinforcing material, reducing the strength of the resulting composite material. be. Therefore, Si
When Tio is coated on the C whisker surface, it is coated with N2
The TiO2 formed on the surface of the SiC whisker may be reduced by heat treatment in a reducing ambient atmosphere such as the above, thereby forming a TiN coating. FIG. 8 shows the results of measuring the buckling strength of preforms that have been subjected to reduction treatment and those that have not been subjected to reduction treatment, in comparison with those that have been prepared using a conventional method. TlO2
The buckling strength a of the preform obtained by reducing the preform tends to be slightly lower than that of the unreduced material, but it is found that the buckling strength a of the preform obtained by the conventional method is 3 to 7 times that of C. It will be done.

(Effects of the Invention) As described above, according to the method for producing a metal matrix composite material according to the present invention, the surface of fibers, particles, or whiskers for constituting a preform is coated in advance with a substance having a lower melting point than that of the fiber, particle, or whisker. Since the preform is formed by diffusion bonding, the strength of the preform is improved, and the molten metal matrix is pressurized, shrinkage is suppressed during infiltration, and damage is prevented.As a result, the yield can be significantly improved. This method has the advantage that it can be easily carried out at relatively low temperatures.

[Brief explanation of the drawing]

Figures 1 (a) to (d) are process diagrams for explaining one embodiment of the present invention, Figure 2 is a graph showing the relationship between the amount of Si oxide produced on the SiC surface and heating conditions, and Figure 3 is a graph showing the relationship between the amount of Si oxide produced on the SiC surface and heating conditions. 3 on the SiC surface
i Graph showing the amount of oxide produced and the buckling strength of the preform,
Figure 4 is a graph showing the relationship between sintering temperature and buckling temperature of the preform, Figures 5 (a) and (b) are schematic diagrams for explaining the strengthening mechanism of the preform, and Figure 6 is a graph showing the relationship between the sintering temperature and buckling temperature of the preform. Graph showing the relationship between the fiber volume fraction and buckling strength of the preform, Figure 7 is a graph showing the relationship between the volume ratio of the preform and the shrinkage rate due to infiltration and compounding, and Figure 8 is the graph showing the relationship between the fiber volume fraction and buckling strength of the preform. A graph showing the tensile strength of the composite material produced by the method of the invention, FIG. 9 is a graph showing the buckling strength of the preform when reduction treatment is performed after sintering, and FIG. 10 <a) to (e) ) is a diagram showing the manufacturing process of a metal matrix composite material by a conventional method, and FIGS. 11(a) and 11(b) are schematic diagrams for explaining the strengthening mechanism of a preform by a conventional method. 31.31a, 31b, 31cm...Reinforced fiber (SiC
whiskers), 32... coating material (Si02 layer). (0) (b) ■ 廿cc> (d) Figure 1 Figure 2 Figure 3 Figure 4 Kiku Figure 5 Volume ratio (%) Figure 6 Zumoto f Kiyoshi (Nkun Figure 7 Body Senkan) Main (Vchi) (5 小) Figure 8 Volume *('/,) Figure 9 (G) (b) Figure 10 Figure 11

Claims (1)

[Claims] 1. A reinforcing material made of ceramic fibers, whiskers, or particles is compressed to form a preform with a shape approximating the product, and this preform is impregnated with molten metal as a matrix under pressure to form fibers. In the method for producing a metal matrix composite material for obtaining a reinforced metal matrix composite material, the surface of the reinforcement material is coated with a substance having a melting point lower than that of the reinforcement components in advance at the material stage, and the reinforcement material is formed into a preform. A method for producing a metal matrix composite material, which comprises heating at a temperature equal to or higher than the melting point of the coating material during compression for formation. 2. The method for producing a metal matrix composite material according to claim 1, wherein the reinforcing material is coated with an oxide, nitride, carbide, or silicide of the reinforcing material component.