JPH02194133A - Manufacturing method of whisker-reinforced Al-based metal composite material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a whisker-reinforced Al-based metal composite material having homogeneous texture properties.

[Conventional technology]

AI whiskers made of needle-like single crystals such as S i C, S is N4, and Alz Os! Whisker-reinforced Al-based metal composites combined with , and their alloys are lightweight and have outstanding strength characteristics, so they are attracting attention as materials for a wide range of applications ranging from aircraft and automobiles to sports and leisure fields, and some have already been put into practical use. has been done.

These composite materials are usually manufactured using a pressure casting method, in which a preform in which whiskers are assembled into a predetermined shape is infiltrated and cast under pressure with a molten Al-based metal matrix, or a mixture of whiskers and an Al-based metal matrix powder is used. It is manufactured using a powder metallurgy method that involves sintering using a hot press or the like.

Among these methods, the pressure casting method requires advanced technical techniques to form a preform with a homogeneous structure, and also causes a phenomenon in which part of the Al-based metal is trapped in the preform during infiltration. Recent research has found that the homogenization of matrix components is impaired.

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

[Problem to be solved by the invention]

The physical characteristics of whisker-reinforced metal composites are highly dependent on the degree of dispersion of whiskers present in the matrix metal, so homogeneous composites! Forming II#a is a manufacturing technology requirement, but as mentioned above, it has been difficult to satisfy this requirement by the usual pressure casting method and powder metallurgy method.

It is known that homogenization of the composite structure can be improved by subjecting the composite material to plastic working such as hot extrusion, rolling, or shaping. In particular, it has been recognized that when hot extrusion processing is applied, the strength properties are significantly improved due to the orientation of whiskers and the compression effect of microporosity (2nd Symposium on Advanced Materials Technology (SAMPI!)).
Japan) Hobun, 242~54M5IC Whis Power-
"Manufacturing conditions and mechanical properties of reinforced AN alloy composites", JP-A-63-274727, etc.].

However, when extrusion is used, there is a particular difficulty in that anisotropy occurs in the material properties due to the orientation of the whiskers, making it unsuitable for use as a member requiring isotropic properties.

The present invention solves the above problems and provides whisker reinforcement Aj2 in which the whisker distribution is extremely uniform if isotropic mm.
The present invention provides a method for manufacturing a metal composite material.

[Means to solve the problem]

That is, the method for producing a whisker-reinforced Al-based metal composite according to the present invention involves extruding a mixed molded body or sintered body of whiskers and Al-based metal matrix powder into fine wires, and then cutting them into short pieces to form granules. A structural feature is that the granules are sintered.

As whiskers, SjC or 5
An acicular single crystal of isNn is effectively used, and a powder selected from an An-based metal consisting of Al or an alloy thereof is used for the matrix.

These whiskers and 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. On this occasion,
The particle size of the matrix powder is preferably adjusted to a fine powder of 14 nm or less; if the particle size exceeds this particle size, it becomes difficult to obtain a uniform mixture.

It is desirable to set the composition of both components in the range of 5 to 30% as the whisker volume content (■【) with respect to the Al-based metal matrix. If this volume content (vr) is less than 5%, the whisker The composite reinforcement performance is not effectively exhibited, and if it exceeds 30%, extrusion processing in the subsequent process will not proceed smoothly.

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

The extrusion process is preferably performed using a hot extrusion method under such conditions that the mixed molded body or sintered body becomes a thin wire with a diameter (D) of 0.5 to 2.0+an. In this case, the thin wire diameter (
When D) is less than 0.5 m, nozzle extrusion becomes difficult, while when it exceeds 2.0 m, the effect of improving whisker dispersion by extrusion 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 the diameter of the thin wire).

The granules thus formed are 10-”torr
Sintering is carried out under the following conditions of vacuum atmosphere, temperature range from solidus line -100°C to solidus line, and pressure of 500 kg/c- or more to obtain a whisker-reinforced Al-based metal composite.

[For production]

According to the present invention, a mixed compact or sintered compact of whiskers and Al-based metal matrix powder obtained through a simple processing step is used, and the dispersion degree of the whiskers is improved through a processing step of extruding this into a thin wire. The process of sintering the granules obtained by cutting the thin wire into short pieces as a material serves to eliminate the orientation of whiskers formed during the extrusion process.

These effects work together to make it possible to efficiently form a composite structure in which whisker dispersion is extremely uniform and isotropic.

〔Example〕

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

Example 1, Comparative Example 1 SiC whiskers with an average diameter of 0.4 μm and a length of 20 μm and A1 alloy (6061) powder with a particle size of 44 pm or less were uniformly stirred and mixed in ethanol to obtain a whisker volume content (
Vf) 15% mixture was prepared. Apply this mixture to a surface pressure of 3
The mixture was molded at a pressure of L/cj to form a mixed molded body (diameter: 48 mm, length: 23 mm, length: 23 mm) with a filling rate of 72%.

Next, the mixed molded product was placed in an extrusion container with a diameter of 50 m, and the temperature was 480"C1 and the extrusion surface pressure was 4.5 t/C.
It was extruded into a thin wire with a diameter of 1.5 mm under the same heat and pressure conditions, and then immediately cut into 2 mm lengths to form granules.

The above granular material too g was filled into a mold with an inner diameter of 70 mm, held at a temperature of 550°C for 24 hours under vacuum (10-'torr level), and degassed, and then the surface pressure It/c
A whisker-reinforced Al-based metal composite was obtained by vacuum sintering.

For comparison, the above SiC whisker and AI! .

Mixture with alloy (6061) [Whisker volume content (
V f ) 15%] was directly filled into a mold and vacuum sintered under the same conditions as above to create a whisker-reinforced Al-based metal composite (Comparative Example 1).

Each composite material (F) and T thus obtained was heat treated (T,: 495°C 12hr, 190°C
, 10 hours), the strength characteristics in the pressing direction (P direction) and in the direction perpendicular to the pressing axis (S direction) were measured, and the results are shown in Table 1 for comparison.

In addition, optical micrographs (100x magnification) showing the structure (#?ll polished surface) in the S direction of the composite materials (T,) according to Example 1 and Comparative Example 1 are shown in Figures 1 and 2. .

From Table 2 and FIGS. 1 and 2, it is recognized that the SiC whisker-reinforced A11 alloy material of Example 1 exhibits higher composite properties than that of Comparative Example 1, and also has an excellent isotropic structure. .

Examples 2 to 3 Whisker volume content (Vf) was determined using SiC whiskers and Al alloy (6061) powder using the same method as in Example 1.
A 20% mixed molded body was formed, and this was heated in vacuum to a temperature of 500° C. to perform temporary sintering.

This sintered body was prepared according to Example 1 with a diameter of 2.0 mm and a diameter of 5 mm.
The product was extruded into a thin wire with a diameter of 0.0 mm, and then cut to the same length as the diameter of the thin wire to obtain granules. This granular material was vacuum sintered under the same conditions as in Example 1 to form SiC whiskers AI! A metal composite material was manufactured.

Table 2 shows the strength characteristics of each composite material obtained.

As shown in Table 2, all the composite materials according to Example 2.3 showed good composite properties, but the extruded fine wire diameter was 2.0.
In Example 3, which exceeded the average, the degree of whisker dispersion was not sufficiently improved, and as a result, the strength performance was inferior to that of Example 2.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to efficiently produce a whisker-reinforced Al-based metal composite material that always has a homogeneous and isotropic structure. Useful.

[Brief explanation of the drawing]

Figure 1 is an optical micrograph (100x magnification) magnifying the structure of a whisker-reinforced Al-based metal composite material according to an example of the present invention.
, FIG. 2 is an optical micrograph (100 times) magnifying the structure of a whisker-reinforced Al-based metal composite material according to a comparative example.

Claims (1)

[Claims] 1. A mixed molded body or sintered body of whiskers and Al-based metal matrix powder is extruded into fine wires, cut into short pieces to form granules, and the granules are sintered. A method for producing a whisker-reinforced Al-based metal composite material. 2. The method for producing a whisker-reinforced Al-based metal composite material according to claim 1, wherein the whisker is an acicular single crystal of SiC or Si_3N_4. 3. The volume content (Vf) of whiskers in the Al-based metal matrix is 5 to 30%, and the diameter of the thin wire during extrusion (
2. The method for manufacturing a whisker-reinforced Al-based metal composite material according to claim 1, wherein D) is set in a range of 0.5 to 2.0 mm and the cutting length is set in a range of 1D to 2D.