JPH0371966A - Manufacture of dispersing reinforcing metal composite material - Google Patents

Abstract

PURPOSE:To manufacture a composite material, in which reinforcing material is uniformly dispersed in matrix metal, by dropping the temp. in the range of coexistence of solid and liquid of the matrix metal while stirring the molten matrix metal mixing the reinforcing material and after that, raising the temp. CONSTITUTION:For example, in molten Al alloy 14 as the matrix metal, the reinforcing material 22 of SiC particles is mixed while stirring this with propeller 18 in a stirring device 16. Further, the temp. in the range of coexistence of solid and liquid of the matrix metal is dropped under condition of stirring the molten metal 14 with the propeller 18, and after, the temp. is raised. At the time of dropping the temp. of molten metal 14, this crystallized material is increased and agglomerate of the reinforcing material 22 is broken into fine particles by shearing action with the crystallized material of solid phase, and the broken reinforcing materials 22 are uniformly dispersed in the molten metal 14, which the fluidity is improved by raising the temp. thereof. Therefore, the composite material uniformly dispersing the reinforcing material without remaining the agglomerated condition, is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to dispersion-strengthened metal composite materials, and more particularly to methods of manufacturing the same.

Conventional Techniques One of the methods for manufacturing dispersion-strengthened metal composite materials is to lower the temperature of a molten matrix metal to a temperature below the liquidus line of the matrix metal, as described in, for example, Japanese Patent Application Laid-open No. 147826/1983. A compocasting method is conventionally known in which the molten metal is stirred to form a solid-liquid coexistence state, and a dispersion reinforcing material such as particles is mixed into the molten metal.

In the composite casting method, as the molten metal is mixed with dispersed particles, the viscosity of the molten metal increases. Conventionally, the temperature of the molten metal is gradually raised as the amount of dispersed particles mixed in increases, and casting is performed when the mixing of dispersed particles is completed.

Problems to be Solved by the Invention In this composite casting method, the fluidity of the molten metal is ensured by the thixotropic effect obtained by stirring the molten metal, and the high viscosity of the molten metal in a solid-liquid coexistence state, that is, a semi-molten state, is maintained. Since the dispersion reinforcing material is forcibly mixed into the molten metal using this method, even if the dispersion reinforcing material has poor wettability with respect to the molten metal in the liquid phase, it is relatively easy to mix the reinforcing material into the molten metal. Can be dispersed.

However, dispersed reinforcing materials tend to aggregate, and this tendency is more pronounced as the reinforcing materials become finer. Therefore, when the reinforcing material to be dispersed in the molten metal is fine, it is not possible to sufficiently loosen the reinforcing material agglomerates by simply stirring the molten metal, and therefore, in the conventional composite casting method, the agglomerates remain. It is difficult to produce composite materials in which reinforcement is uniformly dispersed without

In view of the above-mentioned problems in dispersing fine reinforcing material into molten metal using the conventional composite casting method, the present invention has been developed to make it possible to uniformly disperse the reinforcing material in molten metal even when the dispersed reinforcing material is fine. The object of the present invention is to provide a method for producing a composite material in which the reinforcing material is uniformly dispersed in the matrix metal.

Means for Solving the Problems According to the present invention, a dispersion reinforcing material is mixed into a molten metal of a matrix metal, and while the molten metal is stirred, the solid-liquid coexistence temperature range of the matrix metal is maintained. This is achieved by a method for producing a dispersion-strengthened metal composite material, which includes lowering and then increasing the temperature of the molten metal.

According to one aspect of the present invention, in the step of mixing the dispersion reinforcing material into the molten metal of the matrix metal, the temperature of the molten metal is set to the solid-liquid coexistence temperature of the matrix metal, and the molten metal is stirred. Dispersion reinforcing material is mixed in.

According to another aspect of the present invention, the temperature of the molten metal is repeatedly lowered and raised.

In the method of the present invention, the temperature of the molten metal does not exceed the solid-liquid coexistence of the matrix metal in the final stage of heating the molten metal and in the intermediate heating step when the temperature of the molten metal is repeatedly lowered and raised. The temperature may be increased to a higher temperature.

Further, the dispersed reinforcing material in the method of the present invention may be particles or short fibers (including whiskers) made of any material that is stable in the molten metal of the matrix metal.

Furthermore, if the amount of reinforcing material in the molten matrix metal is too large, it is difficult to uniformly disperse the reinforcing material in the molten matrix metal, and if the amount of reinforcing material is too small, it is difficult to disperse the reinforcing material uniformly into the molten matrix metal. becomes difficult to strengthen. Therefore, the volume ratio of the reinforcing material to the molten matrix metal is preferably about 4 to 50%, particularly about 10 to 20%.

Effect of the Invention According to the method of the present invention, after the reinforcing material is mixed into the molten metal of the matrix metal, the molten metal is cooled while being stirred within the solid-liquid coexistence temperature range of the matrix metal, and then heated. Ru. When the temperature of the molten metal is lowered, the amount of the product increases, and the agglomerates of the reinforcing material are loosened by the shearing action of the crystallized substances in the solid phase, and the loosened reinforcing material becomes fluid as the temperature of the molten metal rises. Improved uniform dispersion in the molten metal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Example 1 As shown in FIG. 1, an aluminum alloy (JIS standard AC8A
) was introduced, and the mass was heated by the heater 12 to melt it. Next, while the temperature of the molten aluminum alloy 14 thus formed is maintained at 570° C., which is the liquidus temperature of the aluminum alloy, by the heater 12, the molten metal is stirred by the propeller 18 of the stirring device 16, and the reinforcing material supplying device SiC with a particle size of 0.1 to 50μ from 20
Particles 22 were mixed into the molten metal over a period of 30 minutes.

Most of the SiC particles with a particle size of 10 μm or less were in the form of aggregates that were difficult to uniformly disperse in the molten metal only by stirring with a propeller.

Next, while stirring the molten metal with a propeller, the temperature of the molten metal is lowered and raised in the pattern shown in Figure 2, and casting is performed when the temperature of the molten metal is 600°C.
A composite material consisting of an aluminum alloy with dispersed particles was manufactured.

When the composite material thus produced was then cut and its cross section was observed, it was found that the SiC particles were uniformly dispersed without any remaining agglomerates. Nao S
The volume fraction of iC particles was about 15%.

Example 2 An aluminum alloy in which SiC particles were dispersed in the same manner as in Example 1 above, except that the pattern of temperature decrease and temperature increase of the aluminum alloy was set to the pattern shown in FIG. A composite material was manufactured and its cross section was observed.

As a result, it was found that even in this composite material, the SiC particles were uniformly dispersed without any remaining aggregates. The volume fraction of SiC particles in this composite material is approximately 15%.
Met.

In addition, when composite materials were manufactured in the same manner as in Examples 1 and 2 using SiC whiskers with an average fiber diameter of 0.3 μm and an average fiber length of 5 μm as the dispersion 2 reinforcing material, in both composite materials. It was confirmed that no agglomerates remained (SiC whiskers were uniformly dispersed).

Example 3 Average particle diameters of 0.1μ, 0.3μ, 3μ, as dispersion reinforcement
A composite material made of an aluminum alloy in which SiC particles were dispersed was produced in the same manner and under the same conditions as in Example 1 above, except that SiC particles of 10μ, 40μ, and 100μ were used. The material was investigated for uniformity of dispersion of SiC particles.

In this case, the uniformity of dispersion was investigated using five levels as shown in FIG. In Figure 4, the first degree indicates that the original agglomerates remain essentially intact, and the second degree indicates that the original agglomerates have become slightly smaller, but relatively large agglomerates remain. At 3rd degree, the agglomerates have become relatively smaller but still remain, and at 4th degree, most of the agglomerates have been loosened, but
The dispersion state of the stripped SiC particles is slightly uneven, and at 5 degrees, no aggregates remain at all, and the SiC particles are uniformly dispersed.

For the purpose of comparison, a case where the molten metal was not stirred in a solid-liquid coexistence state and casting was performed immediately after all the SiC particles were mixed into the molten metal (Comparative Example 1), and a case where the SiC The same applies to the case (Comparative Example 2) where the temperature is gradually increased while stirring the molten metal in a solid-liquid coexistence state so that the total volume fraction of particles and crystallized substances in the molten metal becomes substantially constant. S
The uniformity of dispersion of iC particles was measured.

The results of these measurements are shown in FIG. From FIG. 5, it can be seen that the method of the present invention allows the dispersion reinforcing material to be more uniformly dispersed in the matrix metal than in the conventional method, and in particular improves the uniformity of dispersion of very fine reinforcing material. I know what I'm getting.

Example 4 The same procedure as in Example 3 and Comparative Examples 1 and 2 above was used, except that SiC particles with an average particle size of 0.3 μm were used as the dispersion reinforcement, and the volume ratio of SiC particles was 15%. A composite material made of an aluminum alloy dispersed in the above was manufactured, tensile test pieces were formed from each composite material, and a tensile test was conducted on each test piece.

In addition, as Comparative Example 3, aluminum alloy (JIS standard A
A tensile test piece consisting only of C8A) was formed, and the test piece was also subjected to a tensile test.

The results are shown in Figure 'W46.

It can be seen from FIG. 6 that the composite material manufactured according to the present invention has better tensile strength than any of the comparative materials. In particular, the reason why the composite material of this example is superior in tensile strength to the composite materials of Comparative Examples 1 and 2 is that no agglomerates of SiC particles remain and individual particles are uniformly dispersed. This is thought to be due to

Although the present invention has been described above in detail with reference to several embodiments, the present invention is not limited to these embodiments, and various other embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art that

Effects of the Invention As is clear from the above explanation, according to the method of the present invention, after the reinforcing material is mixed into the molten metal of the matrix metal, the molten metal is stirred to maintain a temperature within the solid-liquid coexistence temperature range of the matrix metal. The temperature is lowered and then raised. When the temperature of the molten metal is lowered, the amount of crystallized substances increases, and the agglomerates of the reinforcing material are loosened by the shearing action of the crystallized substances in the solid phase, and the loosened reinforcing material becomes fluid as the temperature of the molten metal rises. The reinforcing material is uniformly dispersed in the molten metal, thereby making it possible to produce a composite material in which the reinforcing material is uniformly dispersed without remaining in the form of agglomerates.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view showing the state in which the dispersion reinforcing material is mixed into the molten metal of the matrix metal, and Fig. 2 shows the pattern of temperature drop and temperature rise of the molten metal in one embodiment of the method of the present invention. FIG. 3 is a graph showing the pattern of temperature drop and temperature rise of the molten metal in another embodiment of the method of the present invention, and FIG. Fig. 5 is a graph showing the relationship between the average particle size of the reinforcing material and the uniformity of dispersion for composite materials produced by the method of the present invention and comparative examples; 1 is a graph showing the tensile strength of a composite material made according to the invention and a comparative example material. DESCRIPTION OF SYMBOLS 10... Crucible, 10... Heater, 14... Molten aluminum alloy, 16... Stirring device, 18...
Propeller, 20... Reinforcement supply device, 22... Si
C Particle Patent Applicant Toyota Motor Corporation Representative Patent Attorney Masatake Akashi Diagram Time (minutes) Time (minutes) Average particle size (pml)

Claims (1)

[Claims] A dispersion-strengthened metal composite comprising mixing a dispersion reinforcing material into a molten metal of a matrix metal, lowering the temperature of the molten metal within the solid-liquid coexistence temperature range of the matrix metal, and then increasing the temperature while stirring the molten metal. Method of manufacturing the material.