JPH0472895B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a metal matrix composite material in which metal compound particles are dispersed, and more particularly to a method for manufacturing the same. In general, by dispersing particles of other materials in a metal material as a matrix to create a particle-dispersed metal matrix composite material, it is possible to take advantage of the excellent properties of the metal material while compensating for its drawbacks. Attempts have been made to improve the strength and heat resistance of light metals such as magnesium alloys and titanium alloys by dispersing ceramic particles such as silicon carbide and silicon nitride, and hard metal particles. Attempts have been made to improve the wear resistance of the copper alloys that make up the bearings and the copper alloys for bearings by dispersing ceramic particles and hard metal particles to the extent that they do not impair the conductivity or bearing performance. There is.
In such a particle-dispersed metal matrix composite material, in order to take advantage of the excellent properties of the matrix metal while effectively compensating for its drawbacks, the dispersed particles must be fine and homogeneous and uniformly dispersed in the matrix metal. Furthermore, in order to inexpensively manufacture a particle-dispersed metal matrix composite material, the dispersed particles must be inexpensive. However, conventional particle-dispersed metal matrix composite materials are generally produced by mechanically mixing particles of 1 to several tens of micrometers produced by mechanical crushing or atomization with molten matrix metal, or by mixing them with molten matrix metal. It is manufactured by injection dispersion method, etc. in which argon gas is blown in, and particle size is 1 μm depending on mechanical crushing method or atomization method.
The following fine particles cannot be produced at low cost, and the particles produced by these methods have low surface activity and poor wettability with the molten matrix metal. There is a difference in the packing density of particles between the upper and lower layers of the molten metal, and therefore, depending on the mechanical mixing method or jet dispersion method, fine particles can be uniformly distributed in the molten matrix metal. It is difficult to disperse the particles into the matrix metal, and it is also difficult to produce a composite material with excellent adhesion between the particles and the matrix metal. In view of the above-mentioned problems in the conventional manufacturing method of particle-dispersed metal matrix composite materials, the inventors of the present application conducted various experimental studies and found that the velocity of the jet jet ejected from the cooling nozzle exceeds the speed of sound. If a mixed gas consisting of the vapor of the metal and the gas of other elements constituting the metal compound is rapidly cooled by passing it through a cooling nozzle and causing adiabatic expansion, it will form very fine particles with a particle size of several hundred angstroms or less and on the surface. Particles of highly active metal compounds can be produced efficiently and inexpensively, and by directing the jet ejected from a cooling nozzle at a flow rate higher than the speed of sound directly into the molten matrix metal, a special stirring device can be used. It has been found that very fine particles can be uniformly dispersed in a molten matrix metal using the molten matrix metal without stirring the molten matrix metal, and the adhesion between the particles and the matrix metal can be improved. The present invention is based on the knowledge obtained as a result of various experimental studies conducted by the inventors of the present invention, and is based on the findings obtained from various experimental studies conducted by the inventors of the present invention. The object of the present invention is to provide a method for efficiently and inexpensively manufacturing a dispersed metal matrix composite material. According to the present invention, this object is achieved by rapidly cooling a gaseous mixture of at least one metal and another element constituting at least one metal compound by passing it through a cooling nozzle and adiabatically expanding it. This is achieved by a method for producing a metal matrix composite material in which metal compound particles are dispersed, in which the metal and the other element are reacted and a jet ejected from the nozzle at a flow rate higher than the speed of sound is introduced into the molten metal. According to the present invention, a mixed gas (gaseous mixture) is passed through a cooling nozzle and is rapidly cooled by adiabatic expansion. During this process, a combination reaction between the metal and other elements takes place, so the particle size is several hundred. It is possible to form extremely fine metal compound particles on the order of Å, and since the thus formed metal compound particles with high surface activity are directly introduced into the molten matrix metal, the metal compound particles and the matrix metal are in close contact with each other. In addition, since the molten matrix metal is appropriately stirred by the jet ejected from the cooling nozzle at a flow rate higher than the speed of sound, the difference in specific gravity between the metal compound constituting the particles and the matrix metal is reduced. Even when the particles are relatively large, the metal compound particles can be uniformly dispersed in the matrix metal without stirring the molten matrix metal using a stirring device such as an electromagnetic stirring device. Furthermore, according to the present invention, the formation of very fine metal compound particles and the dispersion of the metal compound particles into the molten matrix metal are carried out continuously as a series of steps without any interruption, so these steps can be carried out without interruption. A metal matrix composite material in which metal compound particles are dispersed can be produced more efficiently and at a lower cost than when the processes are carried out as mutually independent steps. In the method of the present invention, a part of the thermal energy held by the metal vapor is converted into kinetic energy by self-adiabatic expansion by the cooling nozzle, and the jet jet ejected from the cooling nozzle is a high-speed flow of Matsuha 1 to 4. Become. The pressure and temperature of the mixed gas upstream from the cooling nozzle are P ₁ (torr) and T ₁ (〓), respectively, and the pressure, temperature, and velocity of the fluid downstream from the cooling nozzle are P ₂ (torr), respectively. , T ₂ (〓), and M ₂ (Matsuha number), the temperature and velocity of the fluid at any point downstream of the cooling nozzle are given by the following equation. When a tapered nozzle is used as a cooling nozzle, the nozzle outlet pressure P ₂ is the critical pressure.

When [formula] is reached, the speed M ₂ becomes Matsuha 1, and even if the pressure P ₂ decreases further, the speed M ₂ does not increase. On the other hand, when a wide divergent nozzle (also called a Laval nozzle) is used as a cooling nozzle, the velocity M ₂ increases at an accelerating rate as P ₂ /P ₁ decreases, and P ₂ /P ₁ = 1/100. if speed
_M2 becomes Matsuha 4. The temperature T ₁ may be selected depending on the vapor pressure of the metal constituting the metal compound dispersed in the matrix metal, but now T ₁ = 2273〓
(2000℃), specific heat ratio k = 1.667, pressure ratio P ₂ /
Temperature of the fluid downstream of the cooling nozzle according to P ₁ T ₂
and speed M ₂ are approximately the values shown in Table 1 below.

[Table] From Table 1, for example, if the pressure ratio P ₂ /P ₁ is 1/10, T ₂ = 905〓 (632℃), M ₂ = 2.13 (approximately 1400m/se
It turns out that c). Thus, according to the present invention, the very fine metal compound particles formed by passing the mixed gas through the cooling nozzle are thrown into the molten matrix metal at the speed of sound or higher, so that the metal The compound particles can be dispersed into the molten matrix metal before their surface activity decreases, and the molten matrix metal is appropriately stirred by the jet stream ejected from the cooling nozzle at the speed of sound or higher. The compound metal particles can be uniformly dispersed in the molten matrix metal without using a molten metal stirring means. A portion of the kinetic energy possessed by the metal compound particles is converted into thermal energy when they collide with the molten matrix metal, so in order to maintain the temperature of the molten matrix metal substantially constant, the temperature must be increased.
Preferably, T ₂ is set to a temperature slightly lower than the temperature of the molten metal of the matrix metal. Further, according to the present invention, the metal vapor is passed through the cooling nozzle in a mixed state with gases of other elements. In this case, the other elemental gas suppresses the grain growth of the metal vapor due to aggregation, and the other elemental gas functions as a carrier gas, allowing the metal vapor to reach the cooling nozzle more quickly and continuously. Therefore, the particle size of the metal compound particles dispersed in the matrix metal can be further reduced, and variations in the particle size of the metal compound particles can be reduced. In addition, since a gas mixture with other elemental gases is passed through the nozzle, the pressure ratio of the mixed gas before and after the nozzle can be controlled relatively easily by controlling the flow rate of the other elemental gases. Accordingly, the cooling rate of the mixed gas and the particle size of the metal compound particles can be easily controlled. According to one embodiment of the invention, the molten matrix metal is stirred by a molten metal stirring means so that the metal compound particles are more uniformly dispersed in the molten matrix metal. The cooling nozzle used in the present invention may be either a wide-spread nozzle or a tapered nozzle, but the cooling rate of the mixed gas can be increased as much as possible by increasing the flow rate of the mixed gas passing through the nozzle. In order to efficiently form fine, well-sized, high-quality metal compound particles, and to more effectively stir the molten matrix metal with the jet ejected from the nozzle, a wide-end nozzle is used. is preferred. In addition, in the method for producing a metal matrix composite material in which metal compound particles are dispersed according to the present invention, if the molten metal matrix metal is made to flow at a constant flow rate in the cooling nozzle, the metal compound particle dispersed metal having the above-mentioned excellent characteristics can be produced. It is possible to manufacture matrix composites continuously rather than in batches. In this specification, the term "metal compound" refers to a compound of a metal and another element, such as ceramic. The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings. Example 1 FIG. 1 is a schematic configuration diagram showing one composite material manufacturing apparatus suitable for carrying out the method for manufacturing a metal matrix composite material in which metal compound particles are dispersed according to the present invention. In the figure, reference numeral 1 indicates a furnace shell forming a substantially sealed container, and a crucible 2 is placed inside the furnace shell 1.
is located. The crucible 2 includes a gas preheating chamber 5 having a gas introduction port 4 whose communication is controlled by an on-off valve 3, and a metal vapor chamber 6 communicating with the gas preheating chamber.
It has A heater 7 is arranged around the crucible 2 to maintain the inside of the gas preheating chamber 5 and the metal vapor chamber 6 at a predetermined temperature _T1 , and this heater 7 melts the metal charged into the metal vapor chamber 6. The molten metal 8 is converted into molten metal 8, and further evaporated into metal vapor. The bottom wall 9 of the crucible 2 is provided with a conduit 11 that communicates and connects the metal vapor chamber 6 with the composite material production zone 10 in the furnace shell 1, and a diverging nozzle 12 is provided at the lower end of the conduit. . In the composite material manufacturing zone 10, a container 14 for storing a molten matrix metal 13 is arranged below the wide-spread nozzle 12, and is configured to receive the jet stream 15 ejected from the wide-spread nozzle 12. A heater 16 is disposed around the vessel 14 to maintain the molten matrix metal 13 stored within the vessel 14 at a substantially constant temperature. Further, as shown by the imaginary line in FIG. 1, the molten metal 13 can be stirred as necessary by a propeller 18 rotated by a motor 17. The composite material production zone 10 is connected by a conduit 19 to a vacuum pump 21 via an on-off valve 20, and the vacuum pump 21 brings the interior of the composite material production zone 10 and the metal vapor chamber 6 to predetermined pressures of P ₂ and P ₁ , respectively. It is starting to be depressurized. Using the composite material manufacturing apparatus thus constructed, a metal compound particle-dispersed metal matrix composite material was manufactured using silicon nitride particles as a dispersion material and aluminum alloy (JIS standard AC8A) as a matrix metal in the following manner. First, 50 g of silicon metal is charged into the metal vapor chamber 6, nitrogen gas is introduced from the gas introduction port 4 through the gas preheating chamber 5 into the metal vapor chamber 6, and the crucible 2 is rapidly heated by the heater 7 to melt the metal. Temperature inside steam chamber 6
By setting T ₁ to 2100° C., metal silicon was melted to form molten silicon 8, and the amount of nitrogen gas introduced was controlled so that the pressure P ₁ in the metal vapor chamber 6 was 15 torr. Next, the mixed gas of silicon vapor and nitrogen gas formed in the metal vapor chamber 6 is heated to a pressure of P ₂ =
Composite manufacturing zone 10 maintained at 0.5-1 torr
The liquid was ejected through a wide-divergent nozzle 12. In this case, the mixed gas is rapidly cooled down to a temperature T ₂ = approximately 700°C or less by self-adiabatic expansion by the wide-spread nozzle 12, and in the process becomes extremely fine silicon nitride particles, which together with excess nitrogen gas enter the composite material manufacturing zone 10. Moved to. Furthermore, the jet stream 15 containing the silicon nitride particles thus generated is stored in the container 14 and sent to the heater 16.
The particles of silicon nitride are dispersed in the molten aluminum alloy 13 by colliding with the liquid surface of the molten aluminum alloy 13 maintained at a temperature T ₃ =650 to 700°C, and unreacted particles are removed by the vacuum pump 21. Nitrogen gas was removed from composite material production zone 10. After the molten aluminum alloy 13 is completely solidified, the container 14 is taken out from the furnace shell 1, and
An ingot 80 mm in diameter and 80 mm in height made of an aluminum alloy in which silicon nitride particles were dispersed was taken out, and an ingot 22 was prepared as shown in FIG.
A cylindrical body 24 with a diameter of 10 mm and a height of 80 mm is cut out along the center line 23, and a diameter of 10 mm is cut out from the top surface 25 of the cylindrical body at points 15 mm, 40 mm, and 65 mm, respectively.
Samples A to C with a thickness of 10 mm were cut out, and the packing density (weight %) of silicon nitride particles was measured for each sample. The measurement results are shown in the column of Table 2 below. FIG. 3 is a transmission electron micrograph of the above-mentioned sample A, in which the spotted portions are silicon nitride particles and the other portions are aluminum alloy. According to this example, it is understood that silicon nitride particles having a small particle size can be uniformly dispersed in an aluminum alloy. In addition, a composite material manufactured under the same conditions as in the above embodiment except that the molten aluminum alloy 13 was stirred by a propeller 18, and a tapered nozzle 2 as shown in FIG. 4 as a cooling nozzle were used.
Table 2 below shows the measurement results of the packing density of silicon nitride particles for composite materials manufactured under the same conditions as in the above example except that No. 6 was used.
Shown in the columns and. Table 2 also shows silicon nitride particles with a diameter of 80 mm manufactured by dispersing silicon nitride particles (N2 manufactured by NEC Corporation) formed by a metal silicon nitriding method into a molten aluminum alloy by a jet dispersion method.
Also shown are the measurement results of the packing density of silicon nitride particles for a composite material as a comparative example with a height of 80 mm, and the particle size and average particle size of the silicon nitride particles in each composite material. In this case, the injection dispersion method, as shown in FIG. particle feeder 28 forming a mixed fluid of
An injection device 30 having a nozzle 29 that communicates with the conduit 27 and injects a mixed fluid gradually pours the molten copper alloy 32 stored in the ladle 31 into the crucible 33, and mixes the molybdenum particles and argon. This was done by injecting a mixed jet 34 with gas into the falling molten metal 32.

[Table] Example 1' In Example 1 above, ammonia gas is used instead of nitrogen gas, and the pressures P ₁ , , P ₂ and temperatures T ₂
An aluminum alloy (JIS standard
When a composite material using AC8A) as the matrix metal was produced, substantially the same results as those shown in columns ~~ of Table 2 were obtained. Example 2 Using the composite material manufacturing apparatus shown in FIG. 1, aluminum alloy (JIS standard
A metal particle-dispersed metal matrix composite material using AC8A) as the matrix metal was manufactured, and the packing density of silicon carbide particles was determined for each sample of the composite material.
Particle size and average particle size were measured. The manufacturing conditions for this example were as follows. Amount of silicon metal charged: 80g Introduced gas: Methane Temperature T ₁ : 2100℃ Pressure P ₁ : 10torr Temperature tT ₂ : Approx. 800℃ or less Pressure P ₂ : 0.5 to 1.0torr Temperature T ₃ : 650 to 700℃ In this example The measurement results are shown in Table 3 below. The silicon carbide particles used in the comparative examples were "Beta Random-Ultra Fine" manufactured by IBIDEN Corporation.

[Table] Example 3 A copper alloy (0.7% Cr, balance Cu )
A metal matrix composite material in which metal compound particles are dispersed in the matrix metal was manufactured, and the packing density, particle size, and average particle size of silicon carbide particles were measured for samples of each composite material. The manufacturing conditions for this example were as follows. Amount of silicon metal charged: 100g Introduced gas: Methane Temperature T ₁ : 2200℃ Pressure P ₁ : 15torr Temperature T ₂ : Approx. 900℃ or less Pressure P ₂ : 1.0 to 1.5torr Temperature T ₃ : 1100 to 1150℃ In this example The measurement results are shown in Table 4 below. The silicon carbide particles used in the comparative examples were "Beta Random-Ultra Fine" manufactured by IBIDEN Corporation.

[Table] From Tables 2 to 4 above, according to each of the above-mentioned examples, metal compound particles with a much smaller particle size can be uniformly dispersed in the matrix metal compared to the conventional method. In particular, it has been found that if the molten matrix metal is stirred, the metal compound particles can be more uniformly dispersed in the molten matrix metal. In addition, when a tapered nozzle is used as a cooling nozzle, the particle size and average particle size of the metal compound particles become slightly larger, but even in that case, the metal compound particles have a much smaller particle size than in the conventional method. can be uniformly dispersed in the molten matrix metal. Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to these embodiments, and it is understood that various embodiments are possible within the scope of the present invention. It will be clear to those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one composite material manufacturing apparatus suitable for carrying out the method for manufacturing a metal matrix composite material in which metal compound particles are dispersed according to the present invention;
FIG. 2 is an explanatory diagram showing a longitudinal section of a composite material ingot produced in an example, and FIG. 3 is an ingot produced according to the present invention in which silicon nitride particles are used as a dispersion material and aluminum alloy is used as a matrix metal. A transmission electron micrograph of the composite material, FIG. 4 is a partial vertical cross-sectional view showing a tapered nozzle as a cooling nozzle, and FIG. 5 is an illustration showing the manufacturing method of a metal particle-dispersed metal matrix composite material by the injection dispersion method. . 1...furnace shell, 2...crucible, 3...on/off valve, 4...gas introduction port, 5...gas preheating chamber, 6...metal vapor chamber,
7... Heater, 8... Molten metal, 9... Bottom wall, 10... Composite material production zone, 11... Conduit, 12... Diverging nozzle, 13... Molten matrix metal, 14... Container, 15... Jet, 16... Heater, 17 …motor,
18...Propeller, 19...Conduit, 20...Opening/closing valve, 2
DESCRIPTION OF SYMBOLS 1... Vacuum pump, 22... Ingot, 23... Axis, 24... Cylindrical body, 25... Upper surface, 26... Tapered nozzle, 27... Conduit, 28... Particle supplier, 29... Nozzle, 30... Injection device, 31... Ladle , 32...molten metal,
33... Crucible, 34... Mixing jet.

Claims (1)

[Scope of Claims] 1. A gaseous mixture of at least one metal and another element constituting at least one metal compound is passed through a cooling nozzle to expand adiabatically, thereby rapidly cooling the metal and the other element. A method for producing a metal matrix composite material in which metal compound particles are dispersed in a metal matrix by reacting with another element and introducing a jet jet ejected from the nozzle at a flow rate higher than the speed of sound into a molten metal. 2. The method for producing a metal matrix composite material in which metal compound particles are dispersed as set forth in claim 1, wherein the cooling nozzle is a diverging nozzle.