JP3249923B2 - Method for producing particle-dispersed composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a particle-dispersed composite material in which particles such as ceramic particles are dispersed in a molten aluminum alloy, and more particularly to a method for uniformly dispersing mixed particles in an alloy. The present invention relates to a method for producing a dispersion type composite material.

[0002]

2. Description of the Related Art Aluminum or aluminum alloy contains A
It is known that a functional composite material produced by mixing and dispersing ceramic particles such as l ₂ O ₃ and SiC has high strength, low coefficient of thermal expansion, and excellent wear resistance. .

Conventionally, various methods have been known as a method for dispersing desired powder particles in an aluminum alloy.
One example is a powder metallurgy method. In powder metallurgy, first, predetermined powder particles such as ceramic particles are mixed with a metal or alloy powder, and then the mixture is pressed and formed into a desired shape, and then sintered to obtain the desired powder particles in a predetermined metal. To produce metal products. However, when a composite material is formed by using the powder metallurgy method described above, many steps are required for manufacturing, which is troublesome, and the cost is high. Was difficult to manufacture.

Therefore, a method of manufacturing a particle-dispersed composite material by adding and solidifying powder particles in a molten metal or alloy has been considered. However, simply obtained by mixing Al ₂ O ₃ particles in the aluminum powder particles 5 of Al ₂ O ₃ as shown in FIG. 9 is not uniformly dispersed in the aluminum. Therefore, as a molten metal mixing method for producing a composite material by uniformly mixing particles added in the molten metal, for example, as described in Japanese Patent Application Laid-Open No. Hei 3-20424, aluminum or an aluminum alloy is made to contain strontium, and Some attempts have been made to easily and surely disperse the powder particles.

[0005]

However, even when powder particles such as ceramics are mixed in a molten metal according to the invention described in JP-A-3-20424,
If the ceramic particles are added to the liquid metal and agitated, they are mixed for the time being, but when the metal groups solidify, the powder particles segregate at the crystal grain boundaries, or when the metal groups solidify, the particles in the liquid phase become However, there is a problem that particles do not penetrate into the solid phase, and the particles concentrate at the position where the liquid phase remains at the end.

[0006] As described above, in the particle-dispersed metal matrix composite material by the conventional molten metal mixing method, particles cannot be uniformly dispersed and solidified. It has been mainly limited to wear-resistant materials.

The present invention solves these problems, and provides a method for producing a composite material having high strength, in which the added powder particles are uniformly dispersed and solidified in the metal matrix.

[0008]

According to the present invention, in order to solve the above-mentioned problems, a manufacturing method is configured as follows.

That is, 0.005% to 0.2% of strontium and 0.1% are added to an aluminum-silicon alloy.
005% to 0.2% of calcium is added, and powder particles are added to this molten metal and solidified to produce a particle-dispersed composite material.

The silicon content of the aluminum alloy is set to 5% or more.

Further, the powder particles are alumina particles or silicon carbide.

As described above, in the present invention, the wettability of the aluminum alloy to alumina can be greatly improved by adding a predetermined amount of strontium and calcium to the aluminum-silicon alloy. Therefore, when alumina powder particles are added to the aluminum alloy, the powder particles are uniformly dispersed in the aluminum alloy, and the powder particles are uniformly mixed without being discharged from the solid phase when the alloy is solidified. The material is obtained.

When the mixing ratio of either strontium or calcium is less than 0.005%, no improvement in wettability to alumina is observed, while when the mixing ratio exceeds 0.2%, the alumina becomes poor. May damage particles.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Strontium and calcium are added to a molten aluminum-silicon alloy,
An aluminum alloy containing 1-12% Si-0.1% Sr-0.1% Ca was produced. To this aluminum alloy, 2 to 5% of Al ₂ O ₃ powder particles 2 having an average particle size of 30 μm was added and stirred. Then, it was confirmed that the Al ₂ O ₃ powder particles 2 were well dispersed in the aluminum alloy, and when solidified as it was, the powder particles 2 were uniformly dispersed in the aluminum alloy base as shown in FIG. A composite material was obtained.

This is because the aluminum alloy of this embodiment is
Since strontium and calcium are added, the Al ₂ O ₃ powder particles 2 in the liquid phase at the solid-liquid interface are directly wrapped in the solid phase without being discharged from the solid phase, and enter the solid phase. Since the alloy base is solidified, the powder particles 2 can be uniformly dispersed.

As a comparative example, FIG. 2 shows a dispersion state of particles when particles are mixed with a conventional aluminum alloy.
A conventional aluminum alloy contains 0.4% strontium, but does not contain calcium.

As shown in FIG. 2, when only the conventional strontium is added to the aluminum alloy, the powder particles 2 are solidified when the aluminum alloy solidifies even if the powder particles 2 are stirred in the molten aluminum alloy. It can be seen that the powder particles 2 do not enter the phase, segregate at the grain boundaries, and the powder particles 2 are partially concentrated and are not uniformly dispersed in the solidified aluminum alloy.

The factor that governs the behavior of ceramic particles at the metal-solid interface at the solid-liquid interface is whether or not the metal particles are interfacial energy. The following experiment was performed as a means for observing the effect of the interface energy.

The material of the crucible is alumina (Al ₂ O ₃ ), the alloy is melted in a crucible made of alumina, the contact state between the wall surface of the crucible and the alloy is examined, and the wettability between the molten alloy and the alumina is examined. did.

First, when the melt of the alloy according to the present embodiment is put into a crucible and solidified from below, the boundary surface between the solid phase 6 and the liquid phase 8 becomes convex downward as shown in FIG. It can be seen that when the angle θ between the wall surface and alumina is 90 degrees or less, the wettability between the alumina particles and the alloy, which are the same material as the crucible, is good. Therefore, as shown in FIG. 3, the alumina particles 4 wet well with the solid of the present alloy, and the powder particles 2 dispersed in the liquid phase 8 of the alloy are discharged when the molten metal becomes the solid phase 6. Without being incorporated into the solid phase 6 as shown in FIG.
It is uniformly dispersed in the solidified alloy.

On the other hand, when a melt of a conventional alloy, Al-0.4% Sr alloy, is put into the above crucible and solidified from below, FIG.
As shown in the figure, the boundary surface between the solid phase 6 and the liquid phase 8 has an upwardly convex shape. This state indicates that the angle θ ′ between the alloy and the alumina on the crucible wall surface is 90 degrees or more, and the wettability between the alumina and the solid metal is not good. As shown in FIG. It can be seen that the particles do not wet with the solid and are discharged from the solid phase 6 when the molten metal is solidified, and the particles cannot be uniformly dispersed in the molten metal.

The amount of strontium added is 0.005.
%, The effect of dispersing particles in the crucible is small, and no improvement in wettability is observed. On the other hand, it was found that when the amount of strontium added exceeded 0.2%, the damage of alumina was large and it was not practical.

Further, with respect to calcium, as in the case of strontium, when the amount of calcium is 0.005% or less, the effect of dispersing particles in the crucible is small, and no improvement in wettability is observed. On the other hand, it was found that when the amount of added calcium exceeds 0.2%, the alumina is greatly damaged and is not practical.

Both strontium and calcium need to be added to the aluminum alloy. FIG. 7 shows the state of dispersion when strontium is added alone. As shown in FIG. 7, it can be seen that the Al ₂ O ₃ powder particles 5 are not uniformly dispersed. Similarly, FIG. 8 shows a case where calcium is added alone. In this case, as in the case of adding strontium alone, no uniform dispersion of the Al ₂ O ₃ powder particles 5 is observed.

The silicon added to aluminum is 5
% Is desirable. When the amount of silicon added to aluminum was 5% or less, a sufficient effect could not be obtained.

The powder particles 2 added to the alloy are not limited to alumina, but may be silicon carbide particles, and the particle size is not limited to the above example.

[0027]

According to the present invention, the method for producing a composite material comprises the steps of:
Since Sr and Ca were added to the i-alloy and powder particles were added to the alloy to produce a metal in which the powder particles were dispersed, the wettability between the powder particles such as Al ₂ O ₃ and the alloy base was determined. And a composite material in which powder particles are uniformly dispersed in a molten metal can be manufactured at a low cost with a simple apparatus configuration.

[Brief description of the drawings]

FIG. 1 is a photograph showing a metal structure of a composite material manufactured by a manufacturing method according to the present invention.

FIG. 2 is a photograph showing a metal structure of a composite material manufactured by a conventional manufacturing method.

FIG. 3 is a diagram showing the wettability of particles.

FIG. 4 is a diagram showing the wettability of particles.

FIG. 5 is a diagram showing the wettability between an alumina and an alloy.

FIG. 6 is a graph showing the wettability of alumina and an alloy.

FIG. 7 is a photograph showing a metal structure when strontium is added alone.

FIG. 8 is a photograph showing a metal structure when aluminum is added alone.

FIG. 9 is a photograph showing a metal structure when no additive is used.

[Explanation of symbols]

 2,5 powder particles 4alumina particles 6solid phase 8liquid phase

Continuation of front page (56) References JP-A-6-93354 (JP, A) JP-A-63-195235 (JP, A) JP-B-60-27744 (JP, B2) Kure, Nakae, "Al 2 ▼ O ▲ 3 凝固 Solidification state of Al-Si alloy with added particles ”, Casting Engineering 128th National Lecture Meeting Lecture Summary, Japan Foundry Engineering Society, April 30, 1996, p. 117 (58) Field surveyed (Int. Cl. ⁷ , DB name) C22C 1/10 C22C 21/02

Claims (1)

(57) [Claims] 1. An aluminum-silicon alloy melt having a silicon content of 5% or more is added in an amount of 0.005% to 0.2%.
% Strontium and 0.005% to 0.2% calcium; and adding alumina or silicon carbide powder particles to the molten metal to which the strontium and calcium are added. A method for producing a dispersed composite material.