JPH03155449A - Method for manufacturing partial composite members - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a partial composite member in which predetermined portions of an Al-gold alloy are reinforced with SiC whiskers.

[Conventional technology] Lightweight AI for pistons, rocker arms, connecting rods, etc. of internal combustion engines! As a means of locally reinforcing areas made of alloy that are subject to severe thermal shock or sliding with SiC whiskers, SiC whisker preforms are set in predetermined locations in a mold and molten Al alloy is pressure cast. There are known methods to do this (for example, Japanese Patent Laid-Open Nos. 55-24763 and 55-24945). However, since the SiC whisker preform is an extremely fragile aggregate, it is often This has the disadvantage of causing deformation, destruction, etc. For this reason, research on methods for strengthening preforms has been actively conducted, but none has been found to be fully satisfactory.Furthermore, the surface layer of SiC whiskers contains some 0□ during heat treatment during manufacturing. Alternatively, 5iOz etc. may intervene, but the presence of these oxidizing components is due to the St
MgzS promotes selective reaction with Mg contained in the matrix A2 alloy, causing complex defects.
Precipitate the segregated parts such as j. This phenomenon usually becomes a serious problem because Ai alloys containing Mg, such as ACOA, AC4C, AC4D for casting, or wrought materials such as 2618.2024.5052.6061, are often used as a matrix. .

To prevent the above-mentioned segregation, it is necessary to
A method of pressure casting a molten Al gold alloy using a SiC whisker preform from which the NG component has been removed (Special Publication No. 62-
40409) is an effective means, but this method has the disadvantage that the preform itself cannot be strengthened.

Alternatively, a partial composite method may be considered in which a preliminary composite of a predetermined shape is formed from SiC whiskers and an Al alloy in advance, this is set in a predetermined location of a mold, and then cast with molten A2 alloy. However, in this case, Aj! □03 is formed, and this oxide film significantly inhibits the wettability with the matrix A2 alloy, resulting in a decrease in the bonding strength at the interface.

[Problem to be solved by the invention]

The present inventors have conducted extensive research with the aim of solving the above-mentioned problems that are an obstacle when partially compositely strengthening a predetermined part of an Al alloy with SiC whiskers. Powders of noble metals and carbide ceramics are attached to the surface of the formed sintered composite,
The present invention was developed after discovering that it is effective to set this in the reinforced part and cast the molten Al in the process.

When forming a fiber-reinforced composite material, there is a method for improving the wear resistance and self-lubricating properties of the composite material by pressure casting using a fiber molded body in which a metal substance is vapor-deposited on the surface of the reinforcing fibers (
JP-A No. 58-938.13) is known, but
It is not easy to form a homogeneous thin metal coating on micro short fibers such as SIC whiskers, and the coating metal is PbSZn, 5nSCu, etc., which have antifriction properties, so this method differs from the purpose of the present invention. It is something to do.

[Means to solve the problem]

That is, the method for manufacturing a partially composite member according to the present invention is as follows:
A composite base material is produced by sintering a mixture of SiC whiskers and Al alloy powder into a predetermined shape, and a dispersion slurry of a noble metal material and/or a carbide ceramic material is applied to the surface of the composite base material and dried. The structural feature is that after being set in a predetermined position in a mold, it is cast with molten Al alloy.

The SiC whisker serving as a reinforcing material has a diameter of O31~5μ.
A needle-like single crystal having an aspect property of 30 to 100 μm in length is used.

In the present invention, the composite base material for constructing the reinforcing part is:
It is produced by wet mixing SiC whiskers and Al1 alloy powder, and sintering this mixture into a predetermined shape using hot pressing, HIP, etc. in vacuum or an inert atmosphere. The Alfi alloy powder used is the same as the matrix A2 alloy to be cast in the subsequent process, and the mixing ratio of SiC whiskers and A2 alloy powder is set so that the Vt of SiC whiskers in the composite base material is a desired value in the range of 10 to 50%. Set it so that

Next, a dispersion slurry of a noble metal material and a carbide ceramic material is applied to the surface of the composite base material and dried. Examples of noble metal materials include Au, Ag, Pt, or Pt-Pd, and examples of carbide ceramic materials include SiC and Ti.
C or B, C is preferably used. These substances are uniformly dispersed in water or an appropriate organic solvent as fine powders with a particle size of 1 μm or less to form a slurry. In this case, if the particle size exceeds 1 μm, the coating in the subsequent process will not be uniformly applied, and the antioxidation function will be impaired.

Furthermore, various stirring devices are used to disperse the powder in the liquid medium, but it is particularly easy to form a uniformly dispersed slurry when using ultrasonic vibration.

If necessary, a binder component such as paraffin that does not inhibit the composite function can be added to the dispersion slurry.

The dispersion slurry of the noble metal material and/or the carbide ceramic material is uniformly applied to the surface of the composite base material by brush, spray, etc., and dried under vacuum. The thickness of the formed coating layer is desirably 10 μm or less. If this thickness exceeds 0 μm, precious metal components will remain on the surface of the composite base material during the casting process in the subsequent process, and
! This causes a decrease in bonding with the alloy.

The composite base material that has undergone the above coating treatment is set at a predetermined location corresponding to the reinforced part of the mold, and molten Al-gold alloy is cast by pressure casting. At this time, the composite base material is moved from its solidus line to - It is preferable to preheat the aluminum alloy to a temperature in the range of 20 to -100"C and set the temperature of the molten Al alloy to 50°C or more higher than its liquidus temperature. The preheating temperature of the composite base material should be above the solidus line of -20°C. This causes material deformation, which also causes the phase line to change to -100°C.
If the temperature of the A2 molten metal exceeds the liquidus temperature +50° C., cooling of the molten metal proceeds rapidly and a phenomenon occurs that causes a bonding failure. Pressure during casting is 250-3000 kg
The reason for this is that the interfacial bonding force between the composite base material and the matrix/1 alloy will be insufficient if the pressure is less than 250 kg/cm'',
This is because if it exceeds 0.00 kg/cm, material deformation will occur.

In this way, the AI! An alloy-based partially composite member is produced.

[For production]

According to the present invention, the reinforced portion is formed by applying a noble metal material and/or a carbide ceramic material in a fine powder state to the surface of a composite base material in which SiC whiskers and 1-alloy powder are sintered in advance. The reinforced part will not be deformed or destroyed during the molten metal casting stage, and there will be no A/! , O, etc. are not formed. Therefore, the molten matrix Al alloy is always in contact with the coating layer of precious metals and carbide ceramics, which have good wettability, and these coating components are applied at the time of casting. Because it is finally dispersed within the structure of the matrix Al alloy by the applied pressure, it does not remain at the bonding interface.

Due to the above action, a partially composite form with an integral structure in which the interfaces between the composite base material, the matrix, and the 11 alloy are firmly bonded is developed.

〔Example] The present invention will be explained below based on examples.

Example 1 SiC whiskers with an average diameter of 0.5 μm and an average length of 20 μm and Al alloy powder (AC8A) were stirred and dispersed in water.
It was filtered and dried to obtain a homogeneous mixture with a vf of SiC whiskers of 10%. 280 g of this mixture was sintered by hot pressing at a temperature of 600°C, a degree of vacuum of 5X IO-'Torr, a pressure of 1000 kg/cm', and a pressurizing time of 20 minutes to form a disc-shaped composite with a thickness of 20+em and a diameter of 80aus. A base material was prepared.

Precious metal fine powder with an average particle size of 0.1 μm, an average particle size of 0.
A fine carbide ceramic powder of 7 μm as a binder was added to ethanol in which 5% by weight of paraffin had been dissolved, and the mixture was sufficiently stirred by applying ultrasonic vibration to prepare a uniformly dispersed slurry.

The above composite base material was cut from the center into a half-moon shape, each of the dispersed slurries was applied to the cut surface with a brush to a uniform thickness, and vacuum-dried at a vacuum degree of Q, 1 Torr, and a temperature of 60°C.

The composite base material after the coating treatment was set in a half-moon shape in a mold with a diameter of 80.0 m+*, preheated to 500'C in Ar, and placed in a pressure casting machine.Then, it was held at a temperature of 700'C. A molten metal of matrix Al alloy (AC8A) was poured into a mold, and pressure casting was performed while applying a chisel force of 500 kg.

Each of the obtained partial composite materials had a shape in which half-moon-shaped matrix A2 alloy was joined through the cut surface of the composite base material.

The tensile strength of these partial composites in the direction perpendicular to the joint surface was measured, and the results are compared with the applied materials in Table 1.
It was shown to.

Comparative Example 1 Using the same composite base material as in Example 1, a matrix Al alloy was pressure cast under the same conditions as in Example 1 without applying any coating to the cut surface.

The tensile strength of this product was measured according to Example 1, and the results are also shown in Table 1.

Comparative Example 2 Using the same SiC whiskers as in Example 1, the diameter was 805 mm.
A preform having a length of 7110% and a height of 30 mm was prepared, and the preform was cut into two parts from the center.

A partial composite material was manufactured using the above semicircular preform under the same conditions as in Example 1.

The tensile strength of this product was measured according to Example 1, and the results are also listed in Table 1.

Table 1 From the results in Table 1, the tensile strength of each Example is significantly increased compared to the Comparative Example, and the effect of improving bondability is recognized.

〔Effect of the invention〕

As described above, according to the present invention, since the reinforced part is composed of a composite base material made of a strong sintered body, it deforms when subjected to external force during the process like a preform molded body.
No destruction occurs at all. Therefore, it is possible to easily mold even a reinforced part with a thin wall thickness and a complicated shape. In addition, since the surface of the composite base material is coated with a noble metal material and/or a carbonizable ceramic material, Al. Troubles associated with the presence of oxides such as O, etc. are effectively eliminated, and good interfacial bonding with the matrix A2 alloy is always obtained.

Therefore, it is possible to manufacture a partial composite member with a strong integral structure through a relatively simple manufacturing process, so that localized SiC whisker reinforcement structures can be formed in areas that are subject to severe thermal shock, friction, etc., such as piston beds. It is extremely useful in cases where

Claims (1)

[Claims] 1. A composite base material is produced by sintering a mixture of SiC whiskers and Al alloy powder into a predetermined shape, and a noble metal material and/or a carbide ceramic material is coated on the surface of the composite base material. A method for manufacturing a partial composite member, which comprises applying a dispersed slurry, drying it, setting it in a predetermined location of a mold, and then casting with molten Al alloy. 2. The noble metal material is Au, Ag, Pt or Pt-Pd
2. The method of manufacturing a partially composite member according to claim 1, wherein the carbide ceramic material is SiC, TiC or B_4C.