JPH01287238A - Aluminum-base composite material - Google Patents

Abstract

PURPOSE:To uniformly disperse whiskers in an Al-base matrix material by using an Al powder having a specific diameter at the time of manufacturing an Al-base composite material by using an Al powder as a matrix and also using whiskers as a reinforcement. CONSTITUTION:At the time of manufacturing an Al-base composite material in which an Al powder is used as a matrix and also whiskers are used as a reinforcement, an Al powder having an average diameter dp(mu) specified by 5dw/Vf>dp [where dw and Vf represent the average diameter (mu) of the whiskers and the volume percentage of the whiskers in the composite material, respectively] is used. Further, the Al powder mentioned above can be prepared by a gas atomizing method, a centrifugal atomizing method, etc., and moreover, respective whiskers of SiC, Si3N4, Al2O3, etc., are used as the above whiskers, and the diameter and length of the whisker are regulated to about 0.1-1mu and about 5-200mu, respectively, and also the volume percentage of the whiskers is regulated to about 0.05-0.30. By this method, the Al-base composite material in which whiskers are uniformly dispersed can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to whisker-reinforced aluminum-based composites.

In this specification, aluminum and aluminum alloys are collectively referred to as "aluminum".

Conventional technology and its problems Whisker-reinforced composite materials, which use whiskers as reinforcing materials, have high specific strength, high specific stiffness, and excellent heat resistance. It is attracting attention as a material for structural and functional parts in the field of spacecraft such as aircraft and spacecraft, structural and functional parts in the field of transportation equipment such as automobiles and ships, and sports goods and equipment.

Existing methods for manufacturing whisker-reinforced aluminum composites include (a) containing molten aluminum under pressure in a space within a whisker preform prepared in advance; There are two main methods: (1) a high-pressure solidification forging method in which the aluminum powder is cooled after Jt, and (2) a method in which whiskers and aluminum powder are mixed and then compression molded.

Method (a) not only requires the complicated process of manufacturing whisker preforms, but also the preform itself may be deformed due to the high molten pressure during impregnation with molten aluminum. It is difficult to control the volume fraction of whiskers.

On the other hand, method (b) has different problems from method (b). Generally, whiskers have a diameter of 0.1 to
It has a needle-like shape with a diameter of about 1 μm and a length of about 5 to 200 μm, and the fibers are intertwined with each other to form a so-called “moxa-like” shape. Therefore, in order to mix uniformly with the aluminum powder, it is necessary to first sufficiently loosen the tangles and then mix. JP-A-59-185701 and JP-A-60-251,922 disclose a method for disentangling whiskers and uniformly mixing them with aluminum powder. However, if the particle size of the aluminum powder to be mixed is large, the whiskers will concentrate in the gaps between the aluminum powders in the subsequent solidification molding process, making it difficult to expect uniform dispersion with the aluminum matrix. This becomes especially noticeable when producing a composite material with a large volume fraction of whiskers.

Means for Solving the Problems The present inventor has conducted various studies in view of the problems of the prior art as described above, and has found that uniform dispersion of whiskers in an aluminum matrix composite material depends on the diameter of the whiskers used. It has been found that this is possible by using aluminum powder with a particle size smaller than the value defined by the volume fraction of whiskers in the composite phase.

That is, the present invention provides the following aluminum matrix composite material: "An aluminum matrix composite material in which aluminum powder is used as a matrix and whiskers are used as a reinforcing material, and 5d /Vf>dp (however, d, : average diameter of whiskers (μm) Vf : volume fraction of whiskers in composite material dp average diameter of aluminum powder (μm)) An aluminum product characterized by using aluminum powder as a matrix. Base composite material.'' The aluminum powder used as the matrix component in the present invention can be one made by a conventional method such as a gas atomization method or a centrifugal atomization method.

The whiskers used in the present invention are not particularly limited, and include 5iCSSi3 N4, A1203, K20φ6Ti
Known whisker materials such as 02 are used. These whiskers have a diameter of about 0.1 to 1 μm and a length of 5 to 2 μm.
It is about 00 μm. Before use, the tangled state of these whiskers 4-11 must be loosened in advance, as in the case of the prior art.

The mixing ratio of aluminum powder and whiskers may vary depending on the use of the composite shrine, the type of whiskers, etc., but it is usually preferable that the former be about 95 to 70% by volume and the latter about 5 to 30% by volume. In other words, the volume fraction of the whiskers is preferably about 0.05 to 0.30.

Under such conditions, the average diameter d (μm) of the aluminum powder used in the present invention is 5d /Vf>d
p (where d: average diameter of whiskers (μm) Vf: volume fraction of whiskers in the composite material). If this condition is not satisfied, the whiskers and the aluminum powder will not be mixed uniformly, and therefore the physical properties such as tensile strength of the molded product will be poor.

The composite material according to the present invention can be produced by, for example, uniformly mixing aluminum powder and whiskers that meet the above requirements in a solvent that has a low boiling point, does not form compounds with aluminum, and has low toxicity, and then removes the solvent. Thereafter, it is manufactured by filling into cans according to conventional methods, degassing under reduced pressure, sealing the can, and hot extrusion molding.

Effects of the Invention The whisker-reinforced composite material according to the present invention has higher strength than known composite materials because the aluminum matrix and whiskers are uniformly dispersed.

EXAMPLES Examples will be shown below to further clarify the features of the present invention.

Example 1 Air atomized powder of AA6061 aluminum (10
0 mesh passing) was air-classified using a rotary centrifugal air classifier, and the maximum diameter (classification point) was d+ = 5.1 μm, d
2=9.8μm, d3-1.5.3μm, d4=20
．． Four kinds of powders of 2 μm were obtained.

This powder was ultrasonically dispersed in alcohol to give 20.5
Ti02 whiskers (100 average diameter d = 0.64μ determined by scanning electron micrograph at 5000x magnification)
m) at a predetermined volume fraction and dispersed while stirring with a homogenizer to remove alcohol.

The obtained mixed powder was heated at a temperature of 530°C and a pressure of 2000 kg.
Vacuum hot press at f/c, temperature 530'C
After hot extrusion at an extrusion ratio of 10 and T6 treatment, the resulting composite phase was subjected to a tensile test.

FIG. 1 shows the relationship between whisker volume fraction and tensile strength when aluminum powder with d2=9.81 tm is used.

When the volume fraction of whiskers is up to 0.28, the tensile strength increases proportionally to the volume fraction, but 0.28
When the value exceeds 0.33, the rate of increase begins to decline, and from around 0.33 onwards, the rate of increase begins to decline.

When the whisker volume fraction is 0.28, 5XO,64
÷0.28=11. ．． 4, and if the whisker volume fraction is 0.33, then 5XO, 64÷0.33=9.
7, the diameter of the aluminum powder in this example,
The average whisker diameter and whisker volume fraction are:
”-2 is satisfied.

FIG. 2 shows the relationship between the aluminum powder and the volume fraction of the whiskers, taking into account the average diameter of the whiskers. More specifically, the curve in the figure shows the relationship when d = 5d /V, and on the curve W line and on the left side, there is a linear relationship between the tensile strength and the whisker volume fraction (for example, In Figure 1, Vf is 0.
28 or less), on the right side of the curve, the degree of increase in tensile strength decreases or the strength itself decreases.

From the results shown in FIGS. 1 and 2, it is clear that the volume fraction of whiskers determines the particle size of usable aluminum powder.

In addition, V shown as "A" in FIGS. 1 and 2
An optical micrograph (1000x) of the crystal structure of the aluminum composite phase with f=0.25 is shown in Figure 3, and “
FIG. 4 shows an optical micrograph (1000x magnification) of the crystal structure of the aluminum composite phase Vr-〇, 35, which is not shown as "B".

In the case of the aluminum composite phase of the present invention shown in FIG. 3, the whiskers shown in black are uniformly dispersed, whereas in the case of the comparative aluminum composite H shown in FIG.
The whiskers shown in black are unevenly distributed.

Example 2 Example 1 except that SiC whiskers (100 average diameter d = W 0.37 μm determined by scanning high-speed electron micrograph at 5000x magnification) were used in place of the 0.6 Ti02 whiskers. A tensile test of the obtained composite phase was conducted in the same manner as above.

FIG. 5 shows the relationship between the aluminum powder and the volume fraction of the whiskers, taking into account the average diameter of the whiskers.

It is clear that even when the types of whiskers are different, the particle size of the usable aluminum powder is determined by the volume fraction of the whiskers.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between SiC whisker volume fraction and tensile strength when aluminum powder of a specific diameter is used in the composite phase of the present invention. FIG. 2 is a graph showing the relationship between aluminum powder and whisker volume fraction in consideration of the average diameter of SiC whiskers in the composite material of the present invention. FIG. 3 shows an optical micrograph (10
00 times). Figure 4 is an optical micrograph (1
000 times). FIG. 5 is a graph showing the relationship between aluminum powder and the volume fraction of whiskers in the composite material of the present invention, taking into account the average diameter of 20.6Ti02 whiskers. (that's all)

Claims (1)

[Claims] (1) An aluminum matrix composite material in which aluminum powder is used as a matrix and whiskers are used as reinforcing materials, and 5d_w/V_f>d_p {where, d_w: average diameter of whiskers (μm), V_f: volume of whiskers in the composite material. An aluminum matrix composite material characterized in that an aluminum powder having a diameter defined by the ratio d_p: average diameter of aluminum powder (μm)} is used as a matrix.