JPH076015B2 - Method for producing whisker reinforced Al-based metal composite material - Google Patents

Description

The present invention relates to a method for producing a whisker reinforced Al-based metal composite material having a homogeneous texture.

[Conventional technology]

Whisker reinforced Al-based metal composites made by combining whiskers consisting of needle-shaped single crystals such as SiC, Si ₃ N ₄ and Al ₂ O ₃ with Al and its alloys are lightweight and have excellent strength characteristics, and are therefore suitable for aircraft and automobiles. Has been attracting attention as a wide-ranging member for use in various fields from sports to leisure, and some have already been put to practical use.

These composite materials are usually a pressure casting method of infiltrating and casting a matrix melt of an Al-based metal under pressure in a preform that is a collective molding of whiskers, or a mixture of whiskers and matrix powder of an Al-based metal. It is manufactured by the powder metallurgy method of sintering using a hot press or the like.

Among them, the pressure casting method requires a high-level technical method for forming a preform having a homogeneous structure, and at the time of infiltration, a part of Al-based metal is trapped in the preform. Recent studies have found that the homogenization of matrix components is impaired.

On the other hand, in the powder metallurgy method, it is difficult to uniformly mix the whiskers and the matrix metal powder, and it is unavoidable that the whiskers after sintering are unevenly distributed at the boundaries of Al-based metal particles.

[Problems to be Solved by the Invention]

Since the properties of the whisker reinforced metal composite material largely depend on the degree of dispersion of the whiskers present in the matrix metal, it is a manufacturing technology requirement to form a homogeneous composite structure. It was difficult to satisfy this requirement by the pressure casting method and the powder metallurgy method.

It is known that the homogenization of the composite structure is improved by subjecting the composite material to hot extrusion, rolling, or forging such as plastic working. In particular, it has been confirmed that the strength characteristics are significantly improved by the hot extrusion process due to the orientation of the whiskers and the crimping action of microporosity [The 2nd Symposium on Advanced Materials Technology (SAMPE Japan)
, P42-54, "Manufacturing Conditions and Mechanical Properties of SiC Whisker Reinforced Al Alloy Composites," JP-A-63-274727, etc.].

However, in the case of extrusion processing, there is a peculiar difficulty that material properties are anisotropy due to the orientation of whiskers, and there is a problem that it is not suitable as a member requiring isotropic properties.

The present invention solves the above problems and provides a method for producing a whisker-reinforced Al-based metal composite material having an isotropic structure in which the dispersion of whiskers is extremely uniform.

[Means for Solving the Problems]

That is, the method for producing a whisker-reinforced Al-based metal composite material according to the present invention is a mixture of a whisker and an Al-based metal matrix powder, or a sintered body is extruded into a fine wire and then cut into granules to be shortly cut, The structural feature is that the granular body is sintered.

As whiskers, needle-like single crystals of SiC or Si ₃ N ₄ obtained by reacting a Si source material with a carbon material at high temperature in an inert gas stream are effectively used.
A powder selected from Al-based metals consisting of Al or its alloys is used.

The whiskers and the Al-based metal matrix powder are uniformly mixed using a wet method of stirring and mixing in an appropriate liquid medium or a dry method of stirring and mixing in a high-speed air stream. At this time, it is preferable to adjust the particle size of the matrix powder to a fine powder having a particle size of 74 μm or less, and if it exceeds this particle size, it becomes difficult to obtain a uniform mixture.

The content of both components is preferably set within a range of 5 to 30% as a volume content (Vf) of whiskers with respect to the Al-based metal matrix. If this volume content (Vf) is less than 5%, the composite reinforcing performance of the whiskers will not be effectively exhibited, and if it exceeds 30%, the extrusion process in the subsequent step will not proceed smoothly.

The above-mentioned mixed powder is molded into a billet shape to obtain a mixed molded body, or the mixed molded body is further heated in vacuum to form a temporary sintered body, which is then subjected to extrusion processing.

The extrusion process is preferably carried out by using a hot extrusion method and under the conditions such that the mixed molded body or the sintered body becomes a fine wire having a diameter (D) of 0.5 to 2.0 mm. In this case, the fine wire diameter (D) is 0.5m
If it is less than m, it will be difficult to extrude the nozzle, while 2.0 mm
If it exceeds, the effect of improving the dispersion of whiskers by the extrusion process becomes insufficient.

The extruded fine wire is then cut into short pieces to form granules. A desirable cutting length is 1D to 2D (D is a fine wire diameter).

The granular material thus formed has a vacuum atmosphere of 10 ⁻³ torr or less, a solidus line −100 ° C. to a solidus line, a temperature range of 500 kg.
Strengthen whiskers by sintering under conditions of pressure of / cm ² or more
Obtain an Al-based metal composite material.

[Work]

According to the present invention, a mixed molded body or a sintered body of whiskers and Al-based metal matrix powder obtained by a simple treatment step is used, and the degree of dispersion of whiskers is improved by a processing step of extruding this into a fine wire, A function of eliminating the orientation of the whiskers formed in the extrusion step is achieved in the process of integrally sintering the fine particles obtained by cutting the thin wires into a material.

By combining these actions, it becomes possible to efficiently form a isotropic composite structure having extremely uniform whisker dispersibility.

〔Example〕

Hereinafter, the present invention will be described in comparison with Examples and Comparative Examples.

Example 1 and Comparative Example 1 SiC whiskers having an average diameter of 0.4 μm and a length of 20 μm and particle diameters
Al alloy (6061) powder of 44 μm or less was uniformly stirred and mixed in ethanol to prepare a mixture having a whisker volume content (Vf) of 15%. This mixture was molded with a surface pressure of 3 t / cm ² to form a mixed compact with a filling rate of 72% (diameter 48 mm, length 23 mm).
0 mm) was formed.

Then, the mixed molded body was mounted in an extrusion container with a diameter of 50 mm, extruded into a fine wire with a diameter of 1.5 mm under the temperature and pressure of 480 ° C. and an extrusion surface pressure of 4.5 t / cm ² , and immediately cut into granules with a length of 2 mm. I made it a body.

1000 g of the above granules was filled in a mold with an inner diameter of 70 mm, degassed by keeping it at a temperature of 550 ° C for 24 hours under vacuum (10 ^-5 torr level), and then vacuum baking at a surface pressure of 1 t / cm ^2. Bonding was performed to obtain a whisker reinforced Al-based metal composite material.

For comparison, above SiC whiskers and Al alloy (6061)
The mixture [a whisker volume content (Vf) 15%] was filled in a mold as it was, and vacuum-sintered under the same conditions as above to prepare a whisker reinforced Al-based metal composite material (Comparative Example 1).

For each composite material (F) thus obtained and the material subjected to the T ₆ heat treatment (T ₆ : 495 ° C., 2 hr, 190 ° C., 10 hr), the pressing direction (P direction) and the direction perpendicular to the processing axis ( The strength characteristics in the S direction) were measured and shown in Table 1 for comparison.

In addition, S of the composite material (T ₆ ) according to Example 1 and Comparative Example 1
Optical micrographs (magnification 100 times) showing the texture (mirror-polished surface) in the direction are shown in FIGS. 1 and 2.

From Table 2 and FIG. 1 and FIG. 2, it is recognized that the SiC whisker reinforced Al alloy material of Example 1 has higher composite properties than those of Comparative Example 1 and has an excellent isotropic structure. .

Examples 2 to 3 Using the same method as in Example 1, SiC whiskers and Al alloy (606
1) A mixed compact with a whisker volume content (Vf) of 20% was formed from the powder, and this was heated in vacuum to a temperature of 500 ° C and pre-sintered. The diameter of this sintered body was determined according to Example 1.
It was extruded into thin wires of 2.0 mm and 5.0 mm, and subsequently cut into the same length as the thin wire diameter to obtain a granular material. This granular material was vacuum-sintered under the same conditions as in Example 1 to produce a SiC whisker Al-based metal composite material.

Table 2 shows the strength characteristics of the obtained composite materials.

As shown in Table 2, the composite materials of Examples 2 and 3 all showed good composite characteristics, but the extruded fine wire diameter was 2.0 mm.
In Example 3, which exceeds the range, the degree of dispersion of the whiskers was not sufficiently improved, and as a result, the strength performance was inferior to that in Example 2.

〔The invention's effect〕

As described above, according to the present invention, since it is possible to efficiently produce a whisker-reinforced Al-based metal composite material that is always homogeneous and has an isotropic structure, it can be used as a member for various applications requiring lightweight and high strength properties. It is useful.

[Brief description of drawings]

FIG. 1 is an optical micrograph (100 times) of an enlarged structure of a whisker reinforced Al-based metal composite material according to an embodiment of the present invention, and FIG. 2 is an optical structure of a whisker-reinforced Al-based metal composite material according to a comparative example. It is a micrograph (100 times).

Claims (3)

[Claims] 1. A whisker characterized by comprising: extruding a mixture of a whisker and an Al-based metal matrix powder or a sintered body into a fine wire, then cutting it into short pieces to form granules, and sintering the granules. Manufacturing method of reinforced Al-based metal composite. 2. The method for producing a whisker-reinforced Al-based metal composite material according to claim 1, wherein the whiskers are needle-shaped single crystals of SiC or Si ₃ N ₄ . 3. The whisker volume content (Vf) relative to the Al-based metal matrix is set to 5 to 30%, the fine wire diameter (D) during extrusion is set to 0.5 to 2.0 mm, and the cutting length is set to 1D to 2D. The method for producing a whisker-reinforced Al-based metal composite material according to claim 1.