JPS59208039A - Dispersion strengthened hypereutectic aluminum silicon alloy - Google Patents

Abstract

PURPOSE:To obtain an alloy having high wear resistance and strength by dispersing fine particles for strengthening to be dispersed in Al matrix into primary crystal Si as well and specifying the size of the primary crystal Si as well as the grain size, intergranular distance and volume ratio of said fine particles. CONSTITUTION:The size of primary crystal Si is more preferable as said size is smaller and is made <=20mu. Fine particles for strengthening are the oxide, carbide, nitride, etc. of Si, etc. which exist stably in Al matrix at a high temp. without growing to or forming coarse grains and the grain size thereof is made <=0.5mu in order to obtain substantial dispersion strengthening. The intergranular distance of the fine particles is more preferable as said distance is smaller and is made about <=30mu. The larger the amt. of the fine particles, the better, but if the amt. exceeds 20% by volume, substantial dispersion strengthening cannot be expected and mixed dispersion is difficult and therefore 20% is the upper limit. The fine particles for strengthening are uniformly dispersed in a molten hypereutectic Al-Si alloy in order to satisfy the above-mentioned conditions and thereafter the molten alloy is quickly cooled and is pressurized, by which the intended alloy is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dispersion-strengthened hypereutectic aluminum-silicon alloy.

Dispersion-strengthened alloys in which hard, fine particles that are stable even at high temperatures are dispersed and composited in a metal matrix are known. For example, if the matrix is aluminum, S A
P (S 1intered A IuminumP
oiyder) is well known. The strength of this dispersion-strengthened alloy improves as the amount of dispersed fine particles increases and as the particle spacing becomes narrower.

On the other hand, hypereutectic aluminum-silicon alloy (hereinafter referred to as hypereutectic A
It is well known that primary crystal silicon (hereinafter abbreviated as primary St alloy) can improve strength and wear resistance.

However, in conventional dispersion-strengthened alloys, the particle size of reinforcing particles is generally large, and sufficient strength and wear resistance have not been achieved. In addition, most of the primary Si crystals in hypereutectic Al-3i alloys have large diameters, and sufficient wear resistance and strength are not obtained.

In particular, when a hypereutectic Al-St alloy is strengthened by dispersing reinforcing fine particles, the fine particles are primary S
It was difficult to obtain sufficient strength and durability because □ was dispersed at the interface between i and the aluminum matrix and □ was not included in the primary Si.

The present invention has been made to solve the above-mentioned problems of the prior art, and its primary purpose is to provide a dispersion-strengthened hypereutectic Al--Si alloy having excellent wear resistance and strength.

According to the hypereutectic Al-Si alloy of the present invention, this object is achieved by dispersing reinforcing fine particles in the aluminum matrix and also dispersing these fine particles in the fine primary Si crystals. Ru. Here, the size of the primary crystal St is 20μ or less, and the reinforcing fine particles have a particle size of 0.
．． It is necessary to set the particle size to 5μ or less, the interparticle distance to 30μ or less, and the volume ratio to 20% or less. In this way, primary crystal Si is made finer, reinforcing fine particles are made finer, and primary crystal Si is made finer.
By being dispersed within the i, the strengthening by the primary Si and the dispersion strengthening of the reinforcing fine particles function effectively, and the movement of dislocations is hindered, thereby improving the strength and wear resistance of the hypereutectic Al-3t alloy. performance is greatly improved.

Next, the present invention will be explained in detail.

In the present invention, the smaller the size of primary Si is, the more desirable it is, and it is desirable that it is 20 μm or less. Further, it is more desirable that the thickness be 18μ or less.

The reinforcing fine particles must stably exist in the aluminum matrix at high temperatures and do not grow or coarsen, which would cause a decrease in strength.

Fine particles meeting this condition include oxides, carbides, nitrides, and the like. Specifically, SiC, TiC2ZrC-W
ClNbCl"r+ N-BN-Six Na, A12
01, MgO, 5i02, ZrO2, Fe 20. ,
CuO1 graphite or the like can be used.

The particle size of these fine particles must be 0 to obtain sufficient dispersion strengthening.
．． It is necessary that it is 5μ or less, and more preferably 0°05μ or less.

The smaller the distance between the fine particles, the better. In the present invention, it is necessary that the thickness be 30μ or less, and more preferably 10μ or less.

The larger the amount of these fine particles, the better. Sufficient dispersion strengthening can be expected up to 20% in volume ratio, but no further effect can be expected when the volume ratio exceeds 20%, and it is difficult to mix and disperse more than 20% in molten aluminum, so the upper limit is set at 20%. %.

In order to produce the dispersion-strengthened hypereutectic Al-Si alloy of the present invention, reinforcing fine particles are uniformly dispersed in a molten hypereutectic Al-St alloy by appropriate means such as stirring, and then rapidly cooled and heated. It is necessary to press the

Here, the cooling rate is 25~b is desirable.

Next, embodiments of the present invention will be described with reference to the drawings.

Example In this example, hypersilumin (Cu: 1.5%, Si: 18.0% in weight%) was used as the matrix alloy.
, Mg: 1.0%, Cr: 0.4%, Ni: ], 88%
A1: Remaining part) was used to manufacture a rocker arm using SiC having an average particle size of 0.05 μm as fine particles for dispersion reinforcement. At this time, the casting method allows rapid cooling of the molten metal,
A vertical pressure casting method was used, which allows for good pressure transmission to the molten metal.

First, the Hyper Silumin raw material was put into a melting furnace and melted, and then Si fine particles were mixed into the molten metal using an inert gas as a carrier while stirring the molten metal.

The molten metal thus prepared was poured into a vertical pressure casting apparatus shown in the drawing to manufacture a rocker arm.

The figure is a sectional view of a main part of a vertical pressure casting apparatus, where ■ is an upper die and 2 is a lower die. The upper die 1 and the lower die 2 define a rocker arm-shaped product cavity 3. Type l, 2
A plunger sleeve 4 is provided at the center of the plunger sleeve 4, and a pressure plunger 5 and a counter plunger 6 are slidably inserted into the plunger sleeve 4. A pressure tip 7 and a counter tip 8 are attached to the tips of both plungers 5.6, respectively. Further, the product cavity 3 and the plunger sleeve 4 are communicated via a gate 9. In addition, 10 is a pouring hole, and 11 is an extrusion pin.

Next, the operation will be explained.

The mold was clamped, the gate 9 was closed by the counter chip 8, and the pressure plunger 5 was pulled up to the state shown in the figure.

Next, Hyper Silumin molten metal 12 mixed with SjC fine particles was poured from the pouring port IO. Thereafter, the counter chip 8 was gradually lowered, and the molten metal 12 was gently introduced into the product cavity 3. When 1/4 to 1/3 of the molten metal was introduced into the product cavity, the pressure plunger 5 pressurized the molten metal 12 to rapidly fill the product cavity 3 with the molten metal 12. After solidification, the mold was opened and the product was taken out using the extrusion bottle 11.

This rocker arm was manufactured by changing the amount of SiC dispersed.

As a result, the size of primary Si near the back surface of the rocker arm was 3 μm, and about 12 μm at the center. Also, Si
It was confirmed that C fine particles were mixed in the primary Si.

In this example, a tensile test and a rotational abrasion test were conducted to examine strength and abrasion resistance. The results are shown in Table 1.

From Table 1, it can be seen that the dispersion-strengthened hypereutectic Al-3i alloy of the present invention has significantly improved strength and wear resistance.

As described above, the dispersion-strengthened hypereutectic A1-3i of the present invention
This alloy has significantly improved strength and wear resistance compared to conventional hypereutectic Al-St alloys, so it can be used for parts that require lightweight strength and wear resistance, such as rocker arms, pulleys, etc.
It can be applied to automobile parts such as gears, camshafts, and shift forks.

[Brief explanation of drawings]

The drawing is a sectional view of a main part of a vertical pressure casting apparatus used in an embodiment of the present invention. 1-11 Upper mold 2--M lower mold 3--Product cavity 4--Plunger sleeve 5--Press plunger 6--Counter plunger 7--Press Tip 8----One counter tip 9----Gate 10---One pouring spout 11-Eject pin 12----Molten metal

Claims (1)

[Claims] (1) A dispersion-strengthened hypereutectic aluminum-silicon alloy in which reinforcing fine particles are dispersed in an aluminum matrix and primary crystal silicon is fine, the fine particles having a particle size of 0.5μ or less. The particle distance is 30μ or less, the volume ratio is 20% or less dispersed, and the size of the primary silicon is 20μ or less, and the fine particles are also dispersed in the primary silicon. A dispersion-strengthened hypereutectic aluminum-silicon alloy.