JPS63118043A - Al or al alloy composite material - Google Patents

Abstract

PURPOSE:To improve the mechanical characteristics, heat and wear resistances of the titled composite material by producing a proper amt. of a ZrAl3 layer on the interface between Al (alloy) as a matrix and ZrO2 powder as a reinforcing material added to the matrix. CONSTITUTION:Al (alloy) powder is mixed with 2-50vol% fine ZrO2 powder and the mixture is hermetically sealed in a capsule and compacted by powder metallurgical processing with a hot isostatic press or by other process. At this time, compacting conditions such as temp. and time are properly controlled so as to regulate the amt. of fine ZrO2 powder reacted, that is, the amt. of ZrAl3 produced to >=10% of the fine ZrO2 powder mixed. The resulting composite material has superior heat and wear resistances, high strength and a high modulus of elasticity, so it is suitable for use as a piston material for an automobile or a vane material for a compressor.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has excellent heat resistance and abrasion resistance, and exhibits high levels of strength and elastic modulus, and is useful as automobile pistons, connecting rods, compressor vane materials, etc. The invention relates to Al or Al alloy composite materials.

[Conventional technology]

Al and Al alloys (hereinafter referred to as Al alloys) have the characteristics of being lightweight and having high specific strength. However, because they are generally soft, have low rigidity, and have poor heat resistance and abrasion resistance, their field of application has been severely limited. However, recently, reinforcing materials such as fine ceramic particles and ceramic fibers have been dispersed in Al alloys to improve strength, rigidity,
With the development of Al alloy composite materials with improved physical properties such as heat resistance and abrasion resistance, it is expected that the fields of application will expand significantly.

[Problems to be Solved by the Invention] In order to effectively achieve the purpose of blending reinforcing particles and reinforcing fibers, it is considered to be an essential condition to increase the bonding strength between the Al alloy and the reinforcing material.

However, industrial research on Al alloy composite materials is currently at an early stage, and when a diffusion layer or a compound layer (hereinafter referred to as reaction layer) exists on each contact surface between the Al alloy and the reinforcement, it is difficult to form a composite material. 3.11 Some vague assumptions have been made that the effect will be higher, and the compounding effect is most effectively produced when there is a good bonding state with the contact surface. Such theoretical and qualitative research has not been sufficiently conducted.

Under these circumstances, the present invention specifically selected fine powdered zirconium oxide as a reinforcing material, clarified the preferred blending ratio in the Al alloy, and developed a reaction method that would most effectively exhibit the composite effect. The aim is to clarify the form and thickness of the layers, thereby providing an Al alloy composite material with excellent physical properties.

[Means for Solving the Problems] The composition of the Al or Al alloy composite material according to the present invention is that fine powder zirconium oxide is uniformly dispersed in a matrix made of Al or Al alloy at a ratio of 2 to 50% by volume. Z r A
The gist is that a reaction layer made of 13 is formed.

[Function] The present inventors conducted various studies on factors that are thought to affect the performance of Al alloy composite materials, and found that
We confirmed the fact that the physical properties of the reaction layer generated on each contact surface between the reinforcing material and the Al alloy matrix have an extremely large effect on the performance of the composite material. As a result of searching for various reinforcing materials that could form layers, we came up with fine powdered zirconium oxide. In other words, zirconium oxide fine powder has the effect of dramatically increasing heat resistance and wear resistance when incorporated in an appropriate amount as a reinforcing material into an Al alloy, but these effects are exerted only by the combined effect of the zirconium oxide fine powder itself. It has become clear that the effect is stronger when ZrAl3, an intermetallic compound produced by the reaction between the zirconium oxide fine powder and the Al alloy matrix, is present near the contact surface between the zirconium oxide fine powder and the Al alloy matrix.

As will be made clear in the examples below, 2 to 50% by volume of zirconium oxide fine powder was added to the Al alloy matrix.
ZrAl. It has been confirmed that a composite material that forms a reaction layer consisting of the following can exhibit extremely excellent performance in terms of heat resistance and abrasion resistance.

Therefore, the volume percentage occupied by zirconium oxide fine powder is 2%.
When it is less than 50%, the composite effect as a reinforcing material is not substantially exhibited, while when it exceeds 50%, the composite material becomes hard and its workability is extremely deteriorated, making it impractical. In the present invention, the most preferred range is 5 to 40%. In addition, the reason why the ZrAl3 formed near the contact surface between the zirconium oxide fine powder and the Al alloy was set to be 10% or more is because if it is less than 10%, the composite strengthening effect due to the interposition of the ZrAl3 layer will not be effectively exerted, and the presence of the ZrAl3 layer will not be effective. This is because there is no significant difference between the composite material and the simple zirconium oxide fine powder dispersed composite material. The upper limit of the amount occupied by the three ZrAl layers cannot be set uniformly because it changes depending on the proportion of the zirconium oxide fine powder in the composite material, but if this proportion increases, the composite material will become brittle even at a relatively low reaction rate. It starts to show a trend. Therefore, the volume ratio occupied by the zirconium oxide fine powder is defined as v2ro2, and its α%
When it is assumed that ZrAl3 is generated at the interface layer between the two by reacting with the Al alloy, it may be determined as appropriate according to the blending amount of the zirconium oxide fine powder so that (v2ro2×α) <Q,l. The method for performing the above-mentioned control will be described in detail later.

In addition, if the fine zirconium oxide powder used as a reinforcing material is too coarse, the composite reinforcement effect will not be effectively exhibited, and it may actually act as inclusions and impede physical properties, so fine powder of 145 mesh or less is not recommended. should be used.

The Al alloy composite material of the present invention can be produced by the molten metal method (a method in which fine zirconium oxide powder is dispersed and cast in a molten Al alloy) or the powder metallurgy method (a method in which Al alloy powder and fine zirconium oxide powder are mixed and hot isostatically pressed. However, especially the latter powder metallurgy method, it is easy to obtain a composite material with a high blending ratio of fine zirconium oxide powder, and the molding conditions (temperature , pressure, time, etc.), the reaction of zirconium oxide fine powder jc (ZrA
This is preferable because the amount of ls produced) can be easily adjusted. In addition, the molding temperature after adopting the powder metallurgy method is 580
℃ or higher; below this temperature, the reaction layer (Zr
The production rate of Al3) is very slow, and especially when the reaction layer is intended to have a content of 20% by volume or more, heating is required for an extremely long time, making it impractical. The preferable upper limit of the forming temperature varies depending on the type of Al alloy, but it should be kept below its melting point.

Furthermore, the composite material of the present invention has Zr in the interface layer with the Al alloy.
It can also be produced by heat treating a zirconium oxide powder-reinforced Al alloy composite material in which A13 is not produced. That is, when the above composite material is heated to just below the solidus temperature of the Al alloy matrix, the zirconium oxide powder and the Al alloy react to form ZrAl3 around the ZrO2 particles.
is produced, and the Al alloy composite material of the present invention is obtained.

In addition, the effect of the composite material of the present invention is that fine zirconium oxide powder is mixed into a normal Al alloy composite material (fiber-reinforced composite material, single-particle dispersed composite material, etc.), and Zr is added to the interface layer with the Al alloy.
It can also be obtained by generating Al3.

That is, 1% or more of inorganic carbide (Al20
3゜5i02. TiO2, etc.), inorganic carbides (SiC,
TiC, 84C, C, etc.), inorganic nitrides (Si3N4.
Zirconium oxide fine powder is mixed with one or more of inorganic carbides (TiB2, etc.), TiN, BN, etc., and Z is added to the interface layer between the zirconium oxide fine powder and the Al alloy.
By generating r A 1 :+, the properties of ordinary Al alloy composite materials, especially the heat resistance and wear resistance, can be further improved.

However, when the amount of the above-mentioned inorganic combination material becomes equal to the amount of zirconium oxide fine powder, the amount of reaction layer (ZrAl3) produced tends to be insufficient, and the additive physical property improvement effect due to the formation of the ZrAl3 layer intended by the present invention is lost. Therefore, it is preferable to suppress the amount to an equal amount, more preferably 50% or less, to the zirconium oxide fine powder.

[Example] Example 1 Pure Al powder with a particle size of 350 mesh or less has an average particle size of 2~
A body of 3 μm zirconium oxide (ZrO2) particles
After mixing at a ratio of 20%, encapsulating and sealing, hot isostatic pressing (molding pressure = 1000Kgf 70m2)
A zirconium oxide (Zr02) particle reinforced aluminum composite material was obtained. FIG. 1 shows the relationship between the reaction amount of zirconium oxide (ZrO2) particles in the composite material obtained at this time and the molding temperature. As is clear from the figure, when the molding temperature exceeds 580°C, the reaction between the zirconium oxide (ZrO2) particles and Al proceeds rapidly. Furthermore, the reaction progresses significantly by increasing the molding time.

A typical example of the cross-sectional microstructure of a composite material produced by this method is shown in FIG. 2 (micrograph in place of a drawing). In FIG. 2, the white parts represent Al, and the black dispersed particles represent zirconium oxide (ZrO2) particles. In addition, the gray area around the zirconium oxide (Zr02) particles is a reaction layer between the zirconium oxide (ZrO□) particles and Al, and as a result of EPMA analysis and X-ray diffraction, Z r A 1
It was confirmed that it was 3.

Table 1 shows the mechanical properties of the composite material produced by this method. As is clear from Table 1, as the reaction amount of zirconium oxide (ZrO2) particles increases, the yield strength, strength, and elastic modulus of the composite material increase, and the high-temperature Vickers hardness also increases at each temperature. However, the reaction amount was 40%
The composite material becomes extremely brittle in the vicinity of exceeding this point, becomes a material with low elongation that cannot maintain its yield strength, and has poor workability. Therefore, in the amount of zirconium oxide in this example,
It can be seen that the amount of reaction with Al can be suppressed to 40% or less.

As a comparative example, silicon carbide (Sic), aluminum 1 (Al2O2), silicon nitride (Si
Table 2 shows the mechanical properties of pure Al composites each containing 20% by volume of 3N4). Even when compared with these examples, it can be seen that the properties of the composite material of the present invention are very excellent.

Example 2 Pure Al powder with a particle size of 350 mesh or less and 6061A
Zirconium oxide (ZrO2) particles with an average particle size of 2 to 3 μm were mixed with the l alloy powder at a volume ratio of 20%, and the mixture was encapsulated in capsules and sealed, followed by hot isostatic pressing (forming temperature: 500 µm). °C, pressure crab 1000 gf/am
2) A composite material in which the amount of reacted zirconium oxide (ZrO2) particles was about 5% was obtained. FIG. 3 shows the temporal change in the amount of zirconium oxide (ZrO2) particles reacted when this composite material was heat-treated.

As is clear from Fig. 3, if heat treatment is performed for about 10 hours at a temperature just below the solidus line of matrix Al, the amount of reaction of zirconium oxide (Zr02) particles in the composite material will be approximately 20%.
%, and a composite material satisfying the requirements of the present invention is obtained.

In addition, FIG. 4(A) is a microscopic photograph showing the cross-sectional microstructure of the composite material before heat treatment, and FIG. 4(B) is a micrograph substituted for a drawing showing the cross-sectional microstructure of the composite material after heat treatment. As a result, zirconium oxide (ZrO2) particles are
It can be seen that ZrAl3 reacts with ZrO2 and generates ZrAl3 around ZrO2.

Example 3 Pure Al powder with a particle size of 350 mesh or less has an average particle size of 2
~3μm zirconium oxide (ZrO2) particles were mixed at a volume ratio of 0~60%, encapsulated and sealed in a capsule, and then hot isostatically pressed (550℃ x 1000kgf).
/c+n2X 1 hr or 630℃x 1000k
gf/cm2X 1 hr) to obtain a composite material.

Among the above composite materials, for those subjected to hot isostatic pressing at 630°C, the reaction between ZrO particles and Al progresses during the forming process, and the reaction rate of ZrO2 particles is 20 to 30%.
It was confirmed that it falls within the range of When this composite material was subjected to a Vickers hardness test and the relationship between the volume fraction of ZrO2 particles and hardness was investigated, the tendency shown in FIG. 5 was obtained.

As is clear from this figure, there is a nearly proportional relationship between the volume fraction of ZrO2 particles and the hardness, but if the volume fraction is less than 2%, a sufficient hardness improvement effect cannot be obtained; It can be seen that the objectives of the invention can be achieved.

On the other hand, among the above composite materials, the molding temperature was suppressed to 550°C (Z
Conditions under which the reaction between rO2 particles and Al is difficult to proceed) For those subjected to hot isostatic pressing, hydrostatic extrusion tests were conducted with various extrusion pressures and extrusion ratios, and the surface properties of the extruded materials were investigated.

The results are shown in Table 3, and as is clear from the table, as the volume fraction of ZrO2 particles increases, the extrusion pressure increases and the surface quality of the extruded material also deteriorates. Especially ZrO
The extrusion performance changes drastically when the volume ratio of two particles reaches about 50%, and when it exceeds 50%, surface cracks and seizures become noticeable, and when it reaches 60%, it becomes almost impossible to extrude.
In the wood experiment, a hydrostatic extrusion device with a maximum pressure of 1000 kgf/Cm2 was used). Therefore, in consideration of processability, the volume fraction of ZrO□ particles needs to be suppressed to 50% or less, more preferably 40% or less.

In this experiment, the processing temperature was 580℃ during the molding and extrusion steps.
In order to prevent the ZrO2 particles from reacting with Al (as this reaction progresses, the composite material becomes hard and the formability deteriorates significantly), for practical use it is necessary to keep the temperature at 580°C after forming processes such as extrusion. ZrO
It is necessary to improve heat resistance and abrasion resistance by reacting 10% by volume or more of the two particles with Al.

Town I Nido 550℃x I OOOkgf/cLI2x l br
Extrusion temperature: 480°C Stem speed: 10 mm/sec [Effects of the invention] The present invention is configured as described above, and has Al or an Al alloy as a matrix, zirconium oxide powder added as a reinforcing material, and Al or Al alloy as a matrix. By forming an appropriate amount of ZrAl3 layer in the blush with Al alloy, Al or A
While maintaining the lightweight characteristics of l-alloys, we have dramatically improved physical properties such as rigidity, heat resistance, and abrasion resistance, which were considered to be disadvantageous, and have created Al or Al alloy composite materials with excellent material properties. I was able to provide it.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the molding temperature and the amount of reaction on the surface of zirconium oxide powder when powder metallurgy is used, and Figure 2 is a photomicrograph substituted for a drawing showing the cross-sectional microstructure of a composite material obtained by powder metallurgy. , Figure 3 shows zirconium oxide powder reinforced A obtained by hot isostatic pressing at 500°C.
Graph showing the relationship between heat treatment time and reaction amount of zirconium oxide powder when heat treating l-alloy composite material, Figure 4.
A) and CB) are micrographs substituted for drawings showing the cross-sectional structure of each composite material before and after the above heat treatment, and Fig. 5 is a Z1
2 is a graph showing the relationship between the volume fraction of 02 particles and Vickers hardness.

Claims (1)

[Claims] Finely powdered zirconium oxide is uniformly dispersed in a matrix made of Al or an Al alloy at a ratio of 2 to 50% by volume, and at least 10% by volume of the fine powder is ZrAl.
An Al or Al alloy composite material characterized by forming a reaction layer made of _3.