JPS59208042A - Dispersion strengthened magnesium alloy - Google Patents

Abstract

PURPOSE:To provide a dispersion strengthened Mg alloy having excellent strength and toughness by dispersing fine particles for strengthening having specified grain size, intergranular distance and volume ratio into Mg matrix and crystallizing dendrite of a specified size. CONSTITUTION:Fine particles for strengthening (SiC, TiC, etc.) for strengthening are added to a molten Mg alloy and are stirred to be uniformly dispersed, then the molten metal is pressurized and is cooled quickly at about 25-300 deg.C/sec cooling rate, thereby producing a dispersion strengthened Mg alloy in which the fine particles are dispersed and dendrite is crystallized. The fine particles dispersed in the Mg alloy are made <=0.5mu grain size, <=10mu intergranular distance and <=20% volume ratio. The size of the dendrite is <=20mu and the fine particles are dispersed in the dendrite as well.

Description

[Detailed description of the invention] The present invention relates to dispersion strengthened magnesium alloys.

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 1tered A luminumP o
wder) 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, it is well known that dendrites crystallize in magnesium alloys (hereinafter abbreviated as Mg alloys), and the shape and size of these dendrites affect the strength of the alloy.

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 particular, when strengthening Mg alloys by dispersing reinforcing fine particles, it is difficult to obtain sufficient strength because the fine particles gather at the interface between the dendrite and the magnesium matrix and do not enter the dendrite. there were.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a dispersion-strengthened Mg alloy with excellent strength and toughness.

According to the Mg alloy of the present invention, this object is achieved by dispersing reinforcing fine particles in the magnesium matrix and also dispersing the fine particles in fine dendrites. Here, the dendrite size is 2
The reinforcing fine particles must have a particle size of 0.5 μ or less, an interparticle distance of 10 μ or less, and a volume ratio of 20% or less.

In this way, the dendrites are made finer, and the reinforcing fine particles are made finer and also dispersed in the dendrites, so that the dispersion and strengthening of the reinforcing fine particles functions effectively and the movement of dislocations is prevented. This greatly improves the strength of the Mg alloy.

Next, the present invention will be explained in detail.

In the present invention, the smaller the size of the dendrite, the better the strength and toughness, so it is preferable that the size of the dendrite is at least 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 magnesium 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, 5iC1Tic, ZrC
,,WC,,NbC,”FiN, 13N.

St, N4, A I + Oi, M g O, S
i02, ZrO2, Fe, O, CuO1 graphite, etc. can be used.

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

The smaller the distance between the fine particles, the better. In the present invention, it is necessary that the thickness be 10μ or less, and more preferably 5μ or less.

The larger the amount of these fine particles, the better. Sufficient dispersion strengthening can be expected up to 20% by volume, but no further effect can be expected if it exceeds 20%, and it becomes difficult to disperse in the molten magnesium, so the upper limit was set at 20%. .

In order to manufacture the dispersion-strengthened Mg alloy of the present invention, it is necessary to uniformly disperse reinforcing fine particles into a molten Mg alloy by appropriate means such as stirring, and then pressurize and rapidly cool it.

Here, the cooling rate is 25~b Next, embodiments of the present invention will be described with reference to the drawings.

Example In this example, a magnesium alloy (JIS MC5: AlB2°3~10.7
% Zn; 0.30% or less M n 1O110~0.
50% Si; 0.3% or less Cu; 0.10% or less N
A rocker arm was manufactured using SiC with an average particle size of 0.05 μm as fine particles for dispersion reinforcement.

First, a magnesium alloy raw material was put into a melting furnace and melted, and then SiC 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.

FIG. 1 is a front view of the vertical pressure casting apparatus used in this example. ■ is the casting device main body, and this casting device main body 1 has four tie bars 2 erected, and the tie bars 2
An upper fixing plate 3 is fixed to the upper end of. A pair of clamping cylinders 4 are attached to the upper mold fixing plate 3, and the other end of a clamping rod 5 connected to the clamping cylinders 4 is fixed to a slider platen 6.

This slider platen 6 is slidably attached to the tie bar 2 and is moved up and down by the mold clamping cylinder 4. A pressure cylinder 7 is attached to the upper part of the slider platen 6, and a plunger sleeve 9 provided with a pouring port 8 and an upper die 10 are attached to the lower part. Further, a lower mold 12 is provided at a position facing the upper mold 10 at the upper part of the casting apparatus main body 1 with a bolster 11 interposed therebetween. Note that 13 is a pressurizing plunger, which is connected to the pressurizing cylinder 7 and whose other end is inserted into the plunger sleeve 4.

Further, 14 is a ladle, which pours the molten metal into the pouring port 8.

Reference numeral 15 denotes an automatic temperature adjustment device for a cooling medium for maintaining the temperature of the molds 10 and 12 at a predetermined temperature.

A heat-resistant hose communicating with the mold 10.12 is installed in this automatic temperature adjustment device 15, and a cooling medium circulates within this hose 16. 17 is the sen number for mold temperature measurement,
It is connected to the automatic temperature control device 15 by a lead wire 18, and serves to automatically control the temperature of the mold 10.12 to the temperature set by the mold temperature setting dial 19.

FIG. 2 is a sectional view of the main part near the mold. In Figure 2,
A product cavity 20 is defined by the upper die 10 and the lower die 12, and is connected to the plunger sleeve 9 via a gate 21. A pressure tip 22 fixed to the tip of the pressure plunger 13 slides within the plunger sleeve 9 . A counter tip 24 fixed to a counter opening 23 is provided at a position facing the pressure tip knob 22, and is capable of sliding within a counter sleeve 25 fixed to the lower die 12. .

Reference numerals 26 and 27 are holes provided in the upper mold 10 and lower mold 12, respectively, through which a cooling medium circulates, and are connected to the aforementioned hose 16. 28 is a molten metal, into which fine particles 29 for reinforcement are mixed. Further, 30 is an extrusion pin for extruding the product after casting.

Next, the operation will be explained.

First, the cooling rate of the molten metal in the product cavity 20, which will become a predetermined dendrite cell, was determined. After determining the temperature of the mold 10.12 that will result in this cooling rate and adjusting the mold temperature setting dial 19 to that temperature, the cooling medium is adjusted from the automatic temperature adjustment device 15 to the hose 16 to the lower mold 12 to the hose 16 to the upper mold. 10
- Hose 16 - Circulated with automatic temperature regulator 15.

In this state, a molten magnesium alloy 28 mixed with 5iC29 was poured into the plunger sleeve 9 from the ladle 14 through the pouring spout 8, resulting in the state shown in FIG.

In FIG. 2, the counter chip 24 is lowered and the gate 2
1 was closed, and the molten metal 28 was gently introduced into the product cavity 20 by its own weight. Product cavity 20 is 1/3~l
/2, the pressurizing plunger 13 was lowered and the molten metal 28 was pressurized to about 500 atmospheres. The state at this time is the third
As shown in the figure. After the molten metal 28 solidified, the mold 10.12 was opened and the product was removed through the extrusion bottle 30. This rocker arm was manufactured by changing the amount of SiC dispersed.

As a result, the size of the dendrite near the surface of the rocker arm was 2μ, and the size at the center was about 12μ. Also, S
It was confirmed that iC particles were mixed within the dendrite.

Further, FIG. 4 shows the results of a tensile test conducted with different amounts of SiC dispersed. As is clear from FIG. 4, the tensile strength of the Mg alloy rocker arm according to the present invention is 50 to 60% higher than that of the Mg alloy rocker arm manufactured by conventional die casting. I understand.

Furthermore, it was confirmed that the Mg alloy of the present invention had improved impact value and toughness.

[Brief explanation of drawings]

Figure 1 is a front view of the vertical pressure casting apparatus used in the embodiment of the present invention, Figures 2 and 3 are sectional views of the main parts of Figure 1, and Figure 2 is the state immediately after pouring. FIG. 3 shows the pressurized state, and FIG. 4 is a diagram comparing the conventional technology and the present invention to show changes in tensile strength when the amount of reinforcing fine particles dispersed is changed. 1---Casting apparatus main body 2---Tie bar 3---Upper fixing plate 4---1 Mold clamping cylinder 5---Mold clamping rod 6---Slider platen 7------ --Pressure cylinder 8---Pouring port 9--Plunger sleeve lO---Upper mold 11--Bolster 12--Lower mold 13--Press plunger 14-- Ladle 15 --- Automatic temperature adjustment device 16 --- Hose 17 --- Sensor 18 --- Lead wire 19 --- Type 1 temperature setting dial 20 --- Product cavity 21 -----Gate 22---One pressure tip 23---Counter rod 24---One counter press 25---One counter sleeve 26.27---One hole 28------ Molten metal 29 -・-1--Fine particles 3 (1----Extruded bottle Applicant Toyota Automobile Co., Ltd. - Hachizumi Figure 1 Figure 2 Figure 3 R Figure 4 239-

Claims (1)

[Claims] (1) A dispersion-strengthened magnesium alloy in which reinforcing fine particles are dispersed in a magnesium matrix and dendrites are crystallized, the fine particles having a particle size of 0.5 μm.
The interparticle distance is 10μ or less, the volume ratio is 20% or less dispersed, and the dendrite size is 20μ
A dispersion-strengthened magnesium alloy as follows, characterized in that the fine particles are also dispersed in the dendrites.