JPH01283330A - Manufacture of aluminum-based composite member - Google Patents

Abstract

PURPOSE:To manufacture the title composite member having excellent heat resistance and wear resistance by preheating a mixing molded material of Al metallic powder and a grain-shaped or fiber-shaped reinforcing material to a specific temp., disposing it into a mold, pouring Al alloy molten metal as a matrix therein and subjecting the same to pressure casting. CONSTITUTION:Al or Al alloy powder, and, as a reinforcing material, at 5-60% volume rate to the above, reinforcing grains constituted of inorganic powder, e.g., of ceramics such as Al2O3 and other metallic powder or reinforcing fiber such as long or short fiber of SiC, Si3N4, etc., or inorganic fiber of mica, graphite, alumina, etc., or metallic fiber of W, Fe, etc., are added to a ball mill 1 and are mixed. The mixture 2 is charged to a mold 3 for molding and is pressurized to prepare a molded body 4 constituted of the Al alloy powder and the reinforcing material. The molded body is preheated to the range of 300- the solidus temp. of the powder Al alloy and is charged into a mold 5. The molten metal 6 of an Al alloy for a matrix is poured therein, which is solidified as pressurized by an extrusion mold 7. By this method, the Al-based composite member having excellent heat resistance and wear resistance can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing an aluminum matrix composite member in which aluminum metal is used as a matrix and the matrix is partially composited with a reinforcing material.

(Prior Art) Conventionally, a high-pressure casting method in which a fiber body is composited is known as one of the means for partially reinforcing aluminum metal.

In this method, short fibers such as SiC, 5iaN4, etc. are molded to produce a fibrous body, the fibrous body is placed in a mold, molten aluminum metal is injected, and the mold is cast under pressure. The molten aluminum metal is impregnated into the fibrous body under pressure, and the fibrous body and the aluminum metal are integrally bonded.

(Problem to be solved by the invention) However, according to the conventional high-pressure casting method, when impregnating molten aluminum metal, component segregation occurs due to a certain reaction between aluminum metal and fibers, which causes structural defects. To solve this problem, a method has been proposed in which the reaction part is discharged from the system by unidirectional pressurization (
JP-A No. 62-238062).

However, even with this method, prevention of component segregation is not sufficient (the boundary between the reacted part and the unreacted part is not clear),
Another problem is that the yield is reduced.

Furthermore, in the high-pressure casting method, the fiber body may shrink during impregnation, making it difficult to control V5 (fiber volume ratio), and impregnation with molten metal may be difficult when the relative density of the fiber body is high. Become. In particular, when the wettability between the molten metal and the fibers is poor, the difficulty becomes more pronounced, and there is a problem in that there are significant restrictions such as the type of fiber body.

Furthermore, when forming a glyph body using particulate reinforcing material, impregnation with molten metal is difficult due to the high density of the reinforcing material in the preform, and in fact, it is impossible to use particulate reinforcing material. Have difficulty.

As described above, the high-pressure casting method requires a high pressure of, for example, 1000 kg/cJ or more to achieve impregnation into the fibrous body, requiring large-sized equipment and increasing equipment costs.

The basic objective of the present invention is to solve the above problems, and to provide a method for producing an aluminum matrix composite member that has fewer restrictions on the selection of reinforcing materials and can produce composite members without structural defects at a high yield. It is.

(Means for Solving the Problems) In order to achieve the above object, the method for manufacturing an aluminum matrix composite member of the present invention includes mixing aluminum metal powder and a reinforcing material and molding the mixture into a predetermined shape, and preparing this molded body. It is characterized in that it is heated and placed in a mold, and then molten aluminum metal, which will become the matrix of the composite member, is poured into the mold and pressure cast.

Note that it is desirable that the preheating temperature of the compact be equal to or higher than the solidus temperature of the powdered aluminum metal.

For the above aluminum metal powder, not only aluminum alloy but also pure aluminum can be used as a raw material, and there are no particular restrictions on the type of aluminum alloy, and it can be used depending on the purpose of the composite member etc. It can be selected as appropriate. For example, JIS6061 alloy, AC8AC12JIS2024 alloy, etc., which are general wrought materials, are used.

The method of pulverizing the aluminum metal whose type has been determined in this way is not particularly limited, and various methods such as conventionally used mechanical pulverization methods and physicochemical pulverization methods can be used. Moreover, since an oxide film may be formed on the obtained metal powder, there is no need to use expensive atomized powder using inert dregs, and there are fewer restrictions on raw materials. In addition, the shape of the produced aluminum metal powder may be flaky, acicular, etc.
In order to obtain high density, a spherical shape or a modified shape thereof (for example, a slender spherical shape) is preferable. In addition, the particle size is determined by strength,
WA 0 if you want to obtain a composite member with excellent wear resistance.
．． If IR is about 1 to 100 IfIR, and if a material with excellent lubricity is desired, it is preferably about 200 to 111 m, but it is not limited to this range.

As the reinforcing material to be mixed with the aluminum metal powder described above, reinforcing particles or fiber materials are used.

As the reinforcing particles, inorganic substances such as ceramic powder such as AI 203 and other metals are used, but the shape and particle size are not limited, and two or more types may be used.

For example, the particle size is 0.5 to 10-5 = It should be about the same level as coffee.

As fiber materials, short fibers such as SiC, 5iaN+, etc.
Contains long fibers, as well as mica, graphite, AI 20 a, F
Inorganic compounds such as e20a and metals such as W and e can be used.Furthermore, the fiber may be single crystal (whisker), polycrystalline, or amorphous.

The mixing ratio of the above-mentioned aluminum metal and the reinforcing material is not limited, but it is desirable that they be mixed so that the volume ratio of the reinforcing material is 5 to 60%. In this mixing, a lubricant, a binder, etc. may be added, and the mixture is uniformly stirred using a ball mill or the like.

Note that this stirring and mixing requires a mixing condition with a stirring force that is capable of decomposing the agglomerated material of the reinforcing particles and does not involve pulverization of the aluminum metal powder.

The mixed powder thus obtained is molded into a predetermined shape.

This molding is carried out regardless of whether it is cold or warm; warm temperatures are preferably 100 to 400°C (preferably recrystallization temperature transformation -1 to 2
00 to 300[deg.] C.) and, if desired, pressure molded so that the relative density becomes 60% or more (preferably 65% or more -4-). If this relative density is low, it will easily lose its shape and will be difficult to handle. However, if the pressing force is increased to increase the relative density, the aluminum metal powder will be plastically deformed. This licking process destroys the oxidized film on the surface that has not yet been formed. It is undesirable to increase the relative density more than necessary without doing so.
It is desirable to set it to about 85% or more (more preferably 7
5% or less). A molded article with increased density can be easily stored and transported. The molded body may of course be an integral body, but it is also possible to form a plurality of divided molded bodies.

This molded body is preheated in the mold 1 or outside the mold. Moreover, this preheating can also be performed in a preheating mold or a mold described later.

Furthermore, the preheating temperature is specifically 300°C or higher.
The temperature should be approximately 1-1, preferably at least the solidus temperature of powder aluminum = 7-metal. In addition, even in the solid-liquid coexistence region and even at temperatures above the liquidus line, the surface of the aluminum metal powder is covered with an oxide film and maintains the sawn state, thereby maintaining its shape. Therefore, when preheating is performed above the liquidus temperature U, heating is performed at a temperature that maintains the oxide film, for example, about the liquidus temperature + (20 to 150° C.).

The molded body is placed in a mold and molten aluminum metal, which will become the matrix of the composite member, is poured into the mold. The molded body can also be placed in the mold by installing the divided molded body as described above. Further, molded bodies can be placed at multiple locations in order to strengthen multiple locations as desired.

In this case, it is possible to arrange multiple identical molded bodies, but powder aluminum metal, reinforcing material, density,
It is also possible to arrange different types of molded bodies with different shapes.

Next, as the aluminum metal for the 71~Rix, it is generally possible to use the same kind of aluminum metal as the powdered aluminum metal in the compact, or it is also possible to use a different kind of aluminum metal. This matrix aluminum metal is heated to its own liquidus temperature +50 to 150°C to form a molten metal.

Specifically, for example, JIS6061 alloy has a temperature of 750°C.
degree.

The pressure when pouring the above molten metal into a mold and performing pressure casting is the pressure required for solidifying the molten aluminum metal of 71 to Lynx, and is preferably 500 kg/- or more. . However, it is not necessary that the molten aluminum metal of the matrix impregnates the inside of the molded body.

Note that if an oxide film is formed on the surface of the compact and the compact is heated to a temperature above the solidus temperature of the aluminum metal powder, preferably above the liquidus temperature, the pressing force will be It is desirable that the pressure be higher than the pressure at which the molten metal within the oxide film of the aluminum metal powder is discharged to the outside of the oxide film.

(Function of the invention) According to the present invention, by placing the molded body in a mold and pressurizing the molded body, penetration by the molten aluminum metal of the matrix occurs near the interface between the molded body and the links 71 to 71. This molten metal and the molten metal in which the aluminum metal powder of the molded body has been melted are mixed, and the molded body and the molded body are joined in a high-strength state such as a 71 helix to form a composite body.

In addition, even if the compact is preheated at a temperature below the solidus line of the aluminum metal powder, if the temperature near the interface of the compact in contact with the molten metal of the matrix exceeds the homophase line temperature of the aluminum metal powder, the aluminum metal powder Part of the aluminum metal melts, and even when the powder is covered with an oxide film, the oxide film is broken by pressure, and the melted aluminum metal fills the surrounding cavity and wets the reinforcing material to form a composite. achieved. Therefore, the aluminum metal powder of the compact and the molten aluminum metal of 7 Trinks mix near the interface between the compact and the matrix.

In addition, in most of the molded body (inside the molded body), there is almost no impregnation with molten aluminum metal having a thickness of 71 to 60. Inside the molded body, the molded body is heated to a temperature higher than the solidus temperature of the aluminum nilum metal powder, or even if the temperature is lower than the solidus temperature, the molded body is heated by heat transfer from the molten aluminum metal in the matrix. The aluminum metal powder becomes a solidus temperature tool-F, and the molten aluminum metal powder wets the surrounding reinforcing material, and compounding also occurs inside the compact.

Further, when the compact is heated to a temperature higher than the liquidus temperature of the aluminum metal powder, the surface of the aluminum metal powder is left covered with an oxide film. That is, an oxide film is formed before preheating or during heating.

In implementing this invention, it is possible to adjust the atmosphere during powder production and the control pattern after production so that the thickness of the oxide film is appropriate, and it is also possible to adjust the preheating until the liquidus is reached. The thickness of the oxide film can also be adjusted through control. By heating the molded body at a temperature equal to or higher than the liquidus line of the aluminum metal, the aluminum metal covered with the oxide film in the molded body is melted. On the other hand, the oxide film is heated so as not to enter a liquid phase. Therefore, in a single unit of aluminum aluminum metal powder, only the internal aluminum metal is in a molten state, and the independence of each unit is maintained. Furthermore, the molded body is also pressurized by pressure casting, the oxide film is destroyed, and the molten metal inside leaches out.

The molten metal has high fluidity and efficiently penetrates into the gap between the aluminum metal powder and the reinforcing material, forcibly wetting the aluminum metal powder and the reinforcing material. In addition, the air remaining in the molded body and the scum generated by heating are forcibly removed to the outside of the molded body, thereby preventing the formation of pores and yielding a composite material with a high relative density. In the pressurization, the pressurization force is kept constant or varied and is continued until the aluminum metal solidifies, thereby preventing the generation of pores due to solidification shrinkage. That is, the initial pressure is required to be large enough to cause the oxide film to break down into a composite material, and thereafter the pressure to prevent the formation of pores due to solidification and contraction is required.

Note that the destroyed oxide film contributes to improving the strength as fine particles.

As described above, the molded body is composited, and the aluminum metal of the matrix is partially composited with this composite material to obtain a composite member.

(Example 1) An example of the present invention will be described below based on FIG. 1.

JIS6061 aluminum alloy is made into aluminum metal powder with an average particle size of 40 c by the air atomization method,
With 600 g of this powder and fiber length of 10 to 30 fibers, the fiber diameter is 0.
．． 4IJR and 200 g of SiC whiskers were uniformly mixed in an alcohol solution using a ball mill 1.

This mixed powder 2 was placed in a mold 3, heated to 300°C, and pressurized with a pressure of 100 kg/cJ to have a relative density of 6.
A molded body 4 of 8% was obtained.

This molded body 4 is taken out from the mold 3 and preliminarily rotated at 350°.
The molded body 4 was placed in a mold 5 that had been heated to 350° C., and preheated to 350° C.

Next, heat JIS60 to 750'C in this mold 5.
A molten aluminum metal 6 for the matrix made of 61 aluminum alloy is poured, and a male mold 7 is used to weigh 1000 kg/
Pressure casting was carried out at a pressure of -.

In the obtained composite member, the molten metal 6 of the matrix forms the molded body 4.
The bonding strength was improved by impregnating the reinforcing material at the interface, and it had excellent heat resistance and wear resistance without causing component segregation within the region where the reinforcing material was placed. Furthermore, the material has a low coefficient of thermal expansion, high Young's modulus, and high strength, making it suitable for pistons for internal combustion engines that require strength at high temperatures.

In addition, in order to evaluate the thermal expansion coefficient of the composite member of this example,
An experiment was conducted to measure the coefficient of thermal expansion using a JIS6061 aluminum alloy as Comparative Example 1. The results are shown in Table 1.

Compared to Comparative Example 1, the coefficient of thermal expansion was significantly reduced.

(Example 2) Next, another example will be described below. A JIS 2024 aluminum alloy was made into aluminum metal powder having a particle size of 401M by a conventional method, and 700 g of this powder and 300 g of Al 203 particles having a particle size of between 0.5 and 300 g were dry-mixed uniformly using a ball mill.

This mixed powder was heated and pressurized in a mold in the same manner as in the previous example to obtain a molded body with a relative density of 71%.

The molded body is taken out of the mold and preheated to 700°C, which is the temperature above the liquid phase of the JIS2024 alloy. During this heating, the aluminum metal powder is covered with an oxide film, and even if it is inside the powder or in the molten state, the shape of the compact is not impaired, and the hand links stored in the mold are not affected. No deformation occurred at this time.

Next, in the same manner as in the previous example, a molten metal made of JIS 2024 alloy that was not heated to 750°C was poured into the mold.
In the example in which pressure casting was performed at a pressure of 0.00 kg/cJ, the molten aluminum metal powder in the oxide film penetrated between the reinforcing materials to improve the bonding properties of the compact. The obtained composite member had excellent embryonic properties such as heat resistance and abrasion resistance as in the above example.

(Example 3) Next, three types of composite members were manufactured by changing the preheating temperature of the molded body.

This embodiment will be explained below.

JISAC8A aluminum alloy was made into aluminum alloy powder with an average particle size of 40 mm by a conventional method, and 560 g of this powder was prepared.
and 240 to 120B particles with a particle size of 1.7 IER.
g were uniformly dry mixed using a ball mill.

This mixed powder was placed in a mold and cooled at 200hg/
A molded article was obtained by pressing at a pressure of a'&.

Three of these molded bodies are prepared, and one of them, molded body A, is
The other compact B is preheated to 550'C, which is higher than the solid-liquid coexistence region temperature between the SAC8 aluminum alloy degree (S1゛) and the liquidus temperature (LT). It was preheated at 600°C, which is the phase line temperature -L, and another molded body C was also preheated at 650°C, which was also above the liquidus temperature.

These molded bodies A, B, and C are each housed in a mold,
Molten metal made of JISAC88 alloy heated to 750°C was poured into a mold, and pressure casting was performed at a pressure of 500 kg/-. The resulting composite members used molded body A as Example 3A, molded body B as Example 3B, and molded body C as Example 3C.

Next, experiments were conducted to measure tensile strength and Young's modulus using the composite members of these Examples. The results are shown in Figure 2, and good results were obtained in both tensile strength and Young's modulus.

Although no significant difference was observed between Examples 3A, 3B, and 30 in terms of tensile strength, in terms of Young's modulus, Example 3B was superior to Example 3A, and Example 3C was superior to Example 3B. was.

Next, when the structural states of Examples 3A, 3B, and 3C were observed, it was found that in Example 3A, voids were observed inside the composite material made of compact A, and the relative density was also less than 90%. Ta. Example 3B had fewer voids and a higher relative density than Example 3A, whereas Example 3C had few or no voids and a relative density of almost 100%.

This seems to be due to the higher preheating temperature or the improved wettability between the aluminum metal powder and the reinforcing material.

It is also believed that the difference in Young's modulus was caused by the difference in the structure state.

Next, in order to evaluate the thermal expansion coefficient of the example, JISAC
8^ When the thermal expansion coefficient was measured using aluminum alloy as Comparative Example 3, as shown in Table 2, Comparative Example 3 was 20.
．． 1 x 10-6 ('C"1), whereas Examples 3A, 3B, and 3C have 15-17 x 10'('C-
1>, and both results showed that the effect of reducing the coefficient of thermal expansion was large. Note that among the Examples, there was a tendency that Example 3C had the largest reduction effect, and Example 3A had the smallest reduction effect.

Table 2 (Effects of the Invention) As explained above, according to the present invention, aluminum metal powder and a reinforcing material are mixed and molded into a predetermined shape, and this molded product is preheated and placed in a mold. Then, the molten aluminum metal that becomes the matrix is poured into the mold and pressure cast is performed, so the required pressure during casting is low and the cost of pressurizing equipment can be reduced. Furthermore, there are fewer restrictions on the type of reinforcing material.

In addition, the bondability between the molded body and the matrix is good,
Excellent strength characteristics of joints. The obtained composite member is
There is no component segregation in the areas where the reinforcing material is placed, a uniform structure is obtained, and it has excellent heat resistance and abrasion resistance. Furthermore, it has a low coefficient of thermal expansion, and has high Young's modulus and strength. There is an effect that can be obtained.

Furthermore, if the preheating temperature of the compact is deviated from the solidus temperature of the powdered aluminum metal, the molten aluminum powder will penetrate between the reinforcing materials, thereby improving the bonding properties of the reinforcing materials.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing one embodiment of the present invention, and FIG. 2 is a graph showing mechanical properties of Examples 3A, 3B, and 3C. 2...Mixed powder 4...Molded body 5...Mold

Claims (1)

[Claims] 1. Aluminum metal powder and reinforcing material are mixed and molded into a predetermined shape, this molded body is preheated and placed in a mold, and then a composite member is placed in the mold. A method for manufacturing an aluminum matrix composite member 2, characterized in that molten aluminum metal serving as a matrix is poured and pressure cast.Claim 2: The preheating temperature of the compact is equal to or higher than the solidus temperature of the aluminum metal for powder. Method for manufacturing an aluminum matrix composite member according to 1.