JP2020196946A - Particle-reinforced aluminum composite material, pressure-resistant component using the same and method for manufacturing pressure-resistant component - Google Patents

Abstract

To provide a particle-reinforced aluminum composite material that is improved in machinability without reducing mechanical strength so much as compared with a particle-reinforced aluminum containing a spinel particle as a reinforcing particle.SOLUTION: The particle-reinforced aluminum composite material includes a base material composed of aluminum alloy and a reinforcing particle dispersed in the base material in which the reinforcing particle includes the main component represented by MgAl2O4 and aluminum.SELECTED DRAWING: Figure 5A

Description

The present invention relates to a particle-reinforced aluminum composite material, a pressure-resistant component using the same, and a method for manufacturing the pressure-resistant component.

A particle-reinforced aluminum composite material has been developed in which hard particles (reinforced particles) composed of an inorganic material or the like are contained in the aluminum composite material. For example, Patent Document 1 discloses a particle-reinforced aluminum composite material containing spinel particles as reinforcing particles. The particle-reinforced aluminum composite material described in Patent Document 1 is produced by adding metal oxide particles other than aluminum oxide and magnesium to a molten metal made of aluminum or an aluminum alloy and stirring the mixture. By adding metal oxide particles and magnesium to a molten metal made of aluminum or an aluminum alloy, the metal oxide, magnesium and aluminum react with each other in the molten metal to generate spinel particles. The generated spinel particles are dispersed in the aluminum alloy base material as reinforcing particles.

JP-A-2007-291450

(Problems to be solved by the invention)
Since the particle-reinforced aluminum composite material described in Patent Document 1 contains spinel particles having extremely high hardness as reinforcing particles, it has high mechanical strength but poor machinability.

Therefore, the present invention presents a particle-reinforced aluminum composite material having improved machinability without significantly reducing mechanical strength as compared with a particle-reinforced aluminum composite material containing spinel particles, and a pressure-resistant component using the same. Another object of the present invention is to provide a method for manufacturing a pressure resistant component using the same.

The present invention is a particle-reinforced aluminum composite material containing a base material composed of an aluminum alloy and reinforcing particles dispersed in the base material, wherein the reinforcing particles are mainly represented by MgAl ₂ O _4. Provided is a particle reinforced aluminum composite containing a component and aluminum. In this case, the aluminum in the reinforcing particles may be mixed in the reinforcing particles so as to adhere to the main component.

According to the present invention, the reinforcing particles contain metallic aluminum in addition to spinel (MgAl ₂ O ₄ ) as a main component. The hardness of metallic aluminum is lower than the hardness of spinel. Therefore, the breakability of the reinforced particles according to the present invention is improved, and thereby the machinability of the particle reinforced aluminum composite material can be improved. Further, since the main component of the reinforcing particles dispersed in the base material is spinel (MgAl ₂ O ₄ ), the mechanical strength is secured to some extent. That is, according to the present invention, it is possible to provide a particle-reinforced aluminum composite material having improved machinability with respect to the particle-reinforced aluminum composite material containing spinel particles without significantly reducing the mechanical strength.

In this case, it is preferable that the reinforcing particles contain 40 wt% or more of aluminum. More preferably, the reinforcing particles contain 40 wt% or more of aluminum and 16 wt% or less of magnesium. Even more preferably, the reinforcing particles may contain 40 wt% or more and 50 wt% or less of aluminum and 5 wt% or more and 16 wt% or less of magnesium. Even more preferably, the reinforcing particles contain 40 wt% or more and 50 wt% or less of aluminum, 5 wt% or more and 16 wt% or less of magnesium, 40 wt% or more and 50 wt% or less of oxygen, and unavoidable impurities. It is preferable that the total mass concentration is 100 wt%.

Further, it is preferable that the base material contains more than 12.6 wt% and 20 wt% or less of silicon. Alternatively, it is preferable that the base metal contains crystallization containing β (Si) particles. Here, β (Si) particles are alloyed molten metal in the process of cooling an Al—Si based alloy molten metal in which the silicon content is higher than the silicon content (12.6 wt%) at the co-crystal point of aluminum and silicon. It represents silicon particles that crystallize inside and do not crystallize in the process of cooling the molten Al—Si alloy with the above content or less. When the molten aluminum alloy containing more than 12.6 wt% of silicon is cooled to form the particle-reinforced aluminum composite material according to the present invention, β (Si) particles are crystallized in the base material. The β (Si) particles increase the rigidity of the base metal. Therefore, the rigidity of the particle-reinforced aluminum composite material can be increased.

Further, the average particle diameter (median diameter) of the strengthened particles is preferably 10 μm or more. According to this, since the particle size of the reinforcing particles is much larger than the average particle size (about 0.2 μm) of the reinforcing particles described in Patent Document 1, the wear resistance of the aluminum composite material can be improved.

Further, the crystallized product containing β (Si) particles contained in the base material is at least one of particles having an average particle diameter (median diameter) of 5 μm or less and a maximum particle diameter of 50 μm or less. It should have a diameter. When the average particle size (median diameter) of the crystallized products containing β (Si) particles contained in the base material is 5 μm or less, or when the maximum particle size is 50 μm or less, that is, crystallization in the base material When the material is made finer, the tensile strength and ductility of the aluminum composite material can be increased.

Further, the present invention is a pressure-resistant component having a strength that can withstand a predetermined pressure and the applied pressure, and includes a base material made of an aluminum alloy and reinforcing particles dispersed in the base material. A crystallized product composed of a particle-reinforced aluminum composite material containing, which contains a main component represented by MgAl ₂ O ₄ and aluminum, and contains β (Si) particles in the base material. Provide a pressure resistant component that contains.

According to the above invention, it is possible to provide a pressure resistant component having high mechanical strength, good machinability, and high rigidity.

In this case, the pressure-resistant component has a stress concentration portion where stress is concentrated by the applied pressure, and the size of the crystallized material contained in the base material constituting the stress concentration portion is a portion other than the stress concentration portion. It is preferable that the size is smaller than the size of the crystals contained in the base material constituting the above.

Further, in this case, it is preferable that the average particle diameter (median diameter) of the crystals contained in the base material constituting the stress concentration portion is 5 μm or less and the maximum particle diameter is 50 μm or less.

According to this, since the crystallized products containing β (Si) particles contained in the aluminum alloy base material constituting the stress concentration portion of the pressure-resistant component are refined, the tensile strength and ductility of the stress concentration portion are increased. As a result, the withstand voltage characteristics of the withstand voltage component can be further improved.

The pressure-resistant component may be a caliper body constituting a braking device mounted on a vehicle. In this case, the caliper body connects the cylinder portion that accommodates the piston so as to be movable in the axial direction, the facing portion that is arranged so as to be separated from the cylinder portion in the moving direction of the piston, and the cylinder portion and the facing portion. It is preferable that the portion has a portion and the stress concentration portion is at least one of the boundary portion between the cylinder portion and the connecting portion and the boundary portion between the facing portion and the connecting portion.

The caliper body constituting the brake device receives stress when the piston moves axially due to hydraulic pressure and presses the brake pad against the disc rotor. This stress tends to be concentrated at the boundary portion between the cylinder portion and the connecting portion of the caliper body and the boundary portion between the facing portion and the connecting portion. Therefore, by refining the crystallized material in the aluminum alloy base material constituting the boundary portion where stress is concentrated in this way, the tensile strength and ductility of the boundary portion are improved, and fracture at the boundary portion is suppressed. Will be done. Therefore, the durability of the caliper body is improved.

Further, the present invention is a method for manufacturing a pressure-resistant component having a strength that can withstand a predetermined pressure and a stress concentration portion where the stress is concentrated by the applied pressure. , Raw material particle charging step of charging powder composed of silicon dioxide particles into aluminum alloy molten metal containing magnesium, silicon dioxide particles charged into aluminum alloy molten metal in raw material particle charging process, and components of aluminum alloy molten metal By reacting magnesium and aluminum, which are the above, to generate reinforced particles containing the main component represented by MgAl ₂ O ₄ and aluminum, and by cooling the molten aluminum alloy, the aluminum alloy mother By crystallizing crystallization containing β (Si) particles in the material, the molding process of solidifying the molten aluminum alloy to form the pressure-resistant component, and frictionally stirring the stress-concentrated part of the molded pressure-resistant component. A method for manufacturing pressure-resistant parts, which includes a miniaturization step of refining crystallized products in an aluminum alloy base material constituting a stress concentration site to an average particle diameter of 5 μm or less and a maximum particle diameter of 50 μm or less. provide.

According to the above invention, it is possible to manufacture a pressure-resistant component having high mechanical strength, good machinability, and high Young's modulus (rigidity). In addition, the tensile strength and ductility of the stress-concentrated portion are improved, and as a result, the pressure-resistant characteristics of the pressure-resistant component can be further improved.

FIG. 1 is a schematic view of a manufacturing apparatus for manufacturing a particle-reinforced aluminum composite material. FIG. 2 is an SEM image of the silicon dioxide particles charged into the molten aluminum alloy in Example 1. FIG. 3 is an SEM image (1000 times) of the sample S1 according to the first embodiment. FIG. 4 is an SEM image (10000 times) of sample S1 according to Example 1. FIG. 5A is an enlarged SEM image (40,000 times) of a part of the reinforcing particles. FIG. 5B is an enlarged SEM image (40,000 times) of a part of the reinforcing particles. FIG. 6 is an SEM image (200 times) of sample S9 according to Example 3. FIG. 7 is an SEM image (200 times) of sample S10 according to Example 3. FIG. 8 is a graph showing the relationship between the particle content and Young's modulus. FIG. 9 is a schematic view of the friction stir tool used in Example 4 and the aluminum composite plate that is friction stir. FIG. 10 is a photographic image of a cross section of the tissue according to Example 3 and a cross section of the tissue according to Example 4 observed with a metallurgical microscope. FIG. 11A shows the measurement result of the particle size distribution of the crystallized product according to Example 3. FIG. 11B shows the measurement result of the particle size distribution of the crystallized product according to Example 4. FIG. 12 shows the tensile test results of the tensile test pieces according to Example 3 and Example 4. FIG. 13 shows the amount of elongation of the tensile test piece according to Example 3 and Example 4. FIG. 14 shows the tensile test results of the tensile test pieces according to Example 3 and Example 5. FIG. 15 shows the amount of elongation of the tensile test piece according to Example 3 and Example 5. FIG. 16 is a schematic view of a caliper body as a pressure resistant component according to the sixth embodiment. FIG. 17 is a schematic cross-sectional view of the brake device to which the caliper body of FIG. 16 is assembled.

The particle-reinforced aluminum composite material according to the present invention includes a base material constituting a matrix and reinforced particles dispersed in the base material.

The base material is composed of an aluminum alloy. Any of magnesium (Mg), silicon (Si), iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), and titanium (Ti) as components other than aluminum contained in the aluminum alloy base material. One or more can be exemplified. Among these, for example, an aluminum alloy containing at least magnesium and silicon is preferable as the base material of the present invention.

The reinforcing particles include a main component represented by MgAl ₂ O ₄ and aluminum (metallic aluminum). Here, the principal component refers to a component that forms most of the reinforcing particles and represents the main properties of the reinforcing particles. When all the components are MgAl ₂ O ₄ , the strengthening particles are spinel particles. Therefore, it can be said that the reinforcing particles of the present invention are spinel particles in which aluminum is partially mixed. Aluminum is preferably mixed in the reinforcing particles so as to adhere to the main component (spinel).

The hardness of the spinel particles is very high, and therefore the mechanical strength of the aluminum composite containing the spinel particles is high. However, on the other hand, the machinability is poor. On the other hand, since the reinforcing particles according to the present invention are spinel particles mixed with aluminum having a low hardness, the hardness of the reinforcing particles according to the present invention is slightly lower than the hardness of the spinel particles. Therefore, the fragmentability of the reinforced particles is improved, and thereby the machinability of the particle reinforced aluminum composite material according to the present invention is improved. Further, since most of the reinforcing particles are composed of MgAl ₂ O ₄ which is the main component, the mechanical strength of the aluminum composite material in which the reinforcing particles according to the present invention are dispersed in the base material is such that the spinel particles are the base material. Although it is lower than the aluminum composite material dispersed in it, it does not decrease significantly. Therefore, according to the particle-reinforced aluminum composite material of the present invention, the mechanical strength is not significantly reduced and the machinability is improved as compared with the aluminum composite material containing spinel particles.

The reinforcing particles preferably contain 40 wt% or more of aluminum. The composition of the spinel particles is expressed as MgAl ₂ O _{4, in} which case the content of aluminum in the spinel particles is theoretically 38 wt%. Therefore, when 40 wt% or more of aluminum is contained in the reinforced particles, 2 wt% or more of metallic aluminum is contained in the reinforced particles. Therefore, the reinforcing particles can be configured to contain MgAl ₂ O ₄ as a main component and 2 wt% or more of aluminum. In this case, it is preferable that the reinforcing particles contain aluminum in an amount of 40 wt% or more and 50 wt% or less.

Further, the reinforcing particles according to the present invention preferably contain 16 wt% or less of magnesium. The content of magnesium in the spinel particles is theoretically 16.9 wt%. Therefore, by suppressing the magnesium content to 16 wt% or less, it is possible to prevent all the reinforcing particles from being generated as MgAl ₂ O ₄ , and metallic aluminum is partially mixed in the reinforcing particles. In this case, it is preferable that the reinforcing particles contain magnesium in an amount of 5 wt% or more and 16 wt% or less.

More preferably, the reinforcing particles according to the present invention may contain 40 wt% or more and 50 wt% or less of aluminum and 5 wt% or more and 16 wt% or less of magnesium. Even more preferably, the reinforcing particles according to the present invention contain 40 wt% or more and 50 wt% or less of aluminum, 5 wt% or more and 16 wt% or less of magnesium, 40 wt% or more and 50 wt% or less of oxygen, and unavoidable impurities. Including, it is preferable that the total mass concentration of these is 100 wt%.

Further, it is preferable that the base material contains more than 12.6 wt% of silicon (Si). In the Al (aluminum) -Si (silicon) alloy, the concentration of Si at the eutectic point of Al and Si is 12.6 wt%. When the base material contains Si having a concentration exceeding the concentration of Si at the eutectic point, hard β (Si) particles are generated in the cooling process of the molten aluminum alloy during the production of the particle-reinforced aluminum composite material. Crystallize. The Young's modulus of β (Si) particles is as large as about 185 GPa. Therefore, the rigidity of the particle-reinforced aluminum composite material can be increased by the β (Si) particles crystallized in the base material and the reinforcing particles dispersed in the base material. In addition, the coefficient of linear expansion of the particle-reinforced aluminum composite can be reduced.

Further, it is known that when the content of silicon in the base material exceeds 12.6 wt%, the fluidity of the molten aluminum alloy is improved in the process of manufacturing the particle-reinforced aluminum composite material. Therefore, it is possible to improve the castability when casting the particle-reinforced aluminum composite material according to the present invention. However, if the silicon content in the base material exceeds 20 wt%, the fluidity of the molten aluminum alloy is lowered and the processability of the aluminum composite material after molding is deteriorated. Therefore, the content of silicon in the base metal is preferably more than 12.6 wt% and 20 wt% or less.

Further, the average particle diameter (median diameter) of the reinforcing particles dispersed in the base material is preferably 10 μm or more. Patent Document 1 describes that the diameter of the spinel particles dispersed in the aluminum alloy is 0.2 μm. If the diameter of the reinforcing particles dispersed in the base metal is very small in this way, improvement in wear resistance cannot be expected. Therefore, the wear resistance can be improved by adjusting the average particle size of the reinforced particles dispersed in the base material of the particle-reinforced aluminum composite material to 10 μm or more.

Further, the average particle diameter (median diameter) of the crystallized material containing β (Si) particles contained in the base material is preferably 5 μm or less. Further, the maximum particle size of the crystallized product containing β (Si) particles contained in the base material is preferably 50 μm or less. When the average particle size (median diameter) of the crystallized product containing β (Si) particles contained in the base material is 5 μm or less, and the maximum particle size of the crystallized product containing β (Si) particles is 50 μm or less. That is, when the crystallized product containing β (Si) particles in the base material is refined, the tensile strength and ductility of the aluminum composite material can be increased.

The particle-reinforced aluminum composite material according to the present invention can be produced through a raw material particle input step and a reinforced particle generation step.

In the raw material particle charging step, powder composed of silicon dioxide particles is charged into the molten aluminum alloy containing magnesium. The particle size of the silicon dioxide particles to be charged is preferably about 10 μm to 50 μm. In particular, the average particle size (median diameter) of the silicon dioxide particles to be charged is preferably 10 μm or more. Further, as a method of inputting silicon dioxide particles, a carrier gas (for example, nitrogen gas) is directed from a supply device capable of supplying powder composed of silicon dioxide particles toward the surface of the molten aluminum alloy stored in the storage tank. ) And a method of ejecting the powder so as to be sprayed can be adopted. By spraying the powder composed of silicon dioxide particles onto the molten aluminum alloy in this way, the silicon dioxide particles are uniformly dispersed in the molten aluminum alloy.

In the reinforcing particle generation step, the silicon dioxide particles charged into the molten aluminum alloy in the raw material particle charging step are reacted with magnesium and aluminum, which are the components of the molten aluminum alloy, to obtain the silicon dioxide particles in MgAl ₂ O. _It is changed into reinforced particles containing the main component represented by ₄ and aluminum. In this case, the molten aluminum in which the silicon dioxide particles are charged is stirred in the raw material particle charging step and held at a predetermined temperature (for example, 700 ° C.) for a predetermined time (for example, 120 minutes). As a result, silicon dioxide (SiO ₂ ) is reduced in the molten aluminum alloy and silicon is released into the molten alloy, and aluminum and magnesium react with oxygen, so that the silicon dioxide particles are mainly composed of MgAl ₂ O ₄ . It changes to a particle. Reinforced particles are produced by mixing a small amount of metallic aluminum with the particles thus changed.

Further, by reducing silicon dioxide in the above-mentioned strengthening particle generation step, silicon is released into the molten aluminum alloy. Therefore, the molten aluminum alloy will contain silicon. At this time, if the final content of silicon exceeds 12.6 wt%, crystallization containing β (Si) particles will crystallize in the cooling process of the molten aluminum alloy. Therefore, after the cooling is completed, β (Si) particles crystallize in the base metal. By crystallizing β (Si) particles in the base material, the rigidity of the aluminum composite material can be improved as described above.

Next, a specific example of the method for producing the particle-reinforced aluminum composite material according to the present invention and the reinforced particles contained in the particle-reinforced aluminum composite material produced by the production method will be described. FIG. 1 is a schematic view of a manufacturing apparatus for manufacturing a particle-reinforced aluminum composite material. As shown in FIG. 1, the manufacturing apparatus 1 includes a molten metal storage unit 10, a particle supply apparatus 20, and a decompression apparatus 40.

The molten metal storage unit 10 stores a storage tank 11 for storing the molten aluminum alloy, a heater 12 such as an electric heater for heating the storage tank 11, and a storage container 13 capable of hermetically accommodating the storage tank 11 in a reduced pressure state. It has a stirring device 14 for stirring the molten aluminum alloy L stored in the tank 11 and a relief valve unit 15 for releasing the internal pressure of the storage container 13 to the atmosphere.

The storage tank 11 is composed of a bottomed tubular crucible or the like. A heater 12 is laid around the outer circumference of the storage tank 11. The raw material of the molten aluminum alloy L is put into the storage tank 11. The charged raw material is melted by being heated by the heater 12. As a result, the molten aluminum alloy L is stored in the storage tank 11.

The storage container 13 is a closed container configured so that the decompressed state of the internal space thereof can be maintained. A storage tank 11 and a heater 12 are arranged in the internal space of the storage container 13. When the storage tank 11 and the heater 12 are arranged in the storage container 13, an upper space S is formed above the storage tank 11 as shown in FIG.

The stirring device 14 has a motor 141, a stirring rod 142 coaxially connected to the output shaft of the motor 141 and rotating around the axis in conjunction with the rotation of the motor 141, and a stirring blade 143 attached to the tip of the stirring rod 142. .. The motor 141 is provided above the storage container 13. As shown in FIG. 1, the stirring rod 142 enters the storage container 13 downward from the upper side wall portion of the storage container 13. Then, the tip portion of the stirring rod 142 is inserted into the molten aluminum alloy L stored in the storage tank 11 in the storage container 13 together with the stirring blade 143. By driving the motor 141 in this state, the stirring blade 143 rotates in the molten aluminum alloy L. As a result, the molten aluminum alloy L is agitated.

The relief valve unit 15 has a relief pipe 151 and a relief valve 152. One end of the relief pipe 151 communicates with the upper space S in the storage container 13, and the other end of the relief pipe 151 communicates with the atmosphere. The relief valve 152 is a normally closed valve interposed in the middle of the relief pipe 151, and opens the space in the storage container 13 to the atmosphere by opening the relief valve 152, for example, after the completion of the strengthening particle generation step described later.

The particle supply device 20 includes a first nitrogen gas cylinder 21, a second nitrogen gas cylinder 22, a first gas pipe 23, a second gas pipe 24, a first gas flow rate adjusting valve 25, and a second gas flow rate adjusting valve 26. It has a particle supply tank 27, a fixed quantity supply device 28, a mixing device 29, a powder transfer pipe 30, a powder flow rate adjusting valve 31, and an injection nozzle 32.

The first nitrogen gas cylinder 21 and the second nitrogen gas cylinder 22 are filled with compressed nitrogen gas. The first nitrogen gas cylinder 21 is connected to one end of the first gas pipe 23, and is configured to be able to supply the nitrogen gas inside to the first gas pipe 23. The second nitrogen gas cylinder 22 is connected to one end of the second gas pipe 24, and is configured so that the nitrogen gas inside can be supplied to the second gas pipe 24. Further, a first gas flow rate adjusting valve 25 is interposed in the first gas pipe 23. The first gas flow rate adjusting valve 25 adjusts the flow rate of nitrogen gas flowing through the first gas pipe 23. Further, a second gas flow rate adjusting valve 26 is interposed in the second gas pipe 24. The second gas flow rate adjusting valve 26 adjusts the flow rate of nitrogen gas flowing through the second gas pipe 24.

A particle supply tank 27 is connected to the other end of the first gas pipe 23. The particle supply tank 27 has a tank body 271 and a lid 272 having an internal space. The tank body 271 is formed in a truncated cone shape so that the diameter becomes smaller toward the bottom, and the upper end and the lower end are open. By attaching the lid 272 to the upper end of the tank body 271, the upper end opening of the tank body 271 is closed. Further, the other end of the first gas pipe 23 opens into the internal space of the tank body 271 through the lid 272. The powder P composed of the silicon dioxide particle group is stored in the tank body 271 of the particle supply tank 27.

A fixed quantity supply device 28 is connected to the lower end of the tank body 271 of the particle supply tank 27. The fixed quantity supply device 28 rotates the elongated container body 281 having an internal space, the transfer screw 282 arranged in the internal space of the container body 281 along the longitudinal direction of the container body 281, and the transfer screw 282 around the axis. It has a motor 283 and. An upper opening communicating with the lower end of the tank body 271 of the particle supply tank 27 is formed in the upper part of the container body 281, and a lower opening communicating with the mixing device 29 is formed in the lower part of the container body 281. The powder P stored in the tank body 271 of the particle supply tank 27 is supplied into the container body 281 through the upper opening of the container body 281. Further, when the motor 283 operates, the transport screw 282 rotates, and the powder P supplied into the container body 281 is transported to the right side of FIG. Then, a constant flow rate of powder P is supplied to the mixing device 29 from the lower opening of the container body 281.

The mixing device 29 is formed in a box shape having an internal space. The mixing device 29 has a gas inlet port 291 to which the other end of the second gas pipe 24 is connected, a powder inlet port 292 communicating with a lower opening provided in the container body 281 of the metering supply device 28, and an outlet. A port 293 is formed. Then, the outlet port 293 of the mixing device 29 is connected to one end of the powder transfer pipe 30. As shown in FIG. 1, the powder transfer pipe 30 has entered the inside of the storage container 13. Then, the other end of the powder transfer pipe 30 is connected to the injection nozzle 32 inside the storage container 13. Further, a powder flow rate adjusting valve 31 is interposed in the middle of the powder transport pipe 30.

The injection nozzle 32 is formed in a long shape, and is arranged so that the longitudinal direction coincides with the vertical direction as shown in FIG. The injection nozzle 32 is installed inside the storage tank 11 arranged in the storage container 13 and above the surface of the molten aluminum alloy L stored in the storage tank 11. The injection nozzle 32 is formed in a tubular shape so as to have an internal space, and the other end of the powder transfer pipe 30 is connected to the upper end thereof. Further, a discharge port is formed at the lower end of the injection nozzle 32. Then, the injection nozzle 32 is arranged so that the discharge port of the injection nozzle 32 faces the surface of the molten aluminum alloy stored in the storage tank 11.

The vacuum distillation device 40 includes a vacuum pump 41, a pipe 42, a gas cooling device 43, a particle filter 44, and an on-off valve 45. One end of the pipe 42 is connected to the vacuum pump 41, and the other end of the pipe 42 is inserted into the internal space of the storage container 13. A gas cooling device 43, a particle filter 44, and an on-off valve 45 are interposed in the middle of the pipe 42 from the other end side. The gas cooling device 43 is configured to be able to cool the gas flowing in the pipe 42. The particle filter 44 collects the powder P flowing in the pipe 42.

When the particle-reinforced aluminum composite material is manufactured using the manufacturing apparatus 1 having the above configuration, first, a metal molten metal formation step is carried out. In the metal molten metal generation step, a bulk (ingod) of an aluminum alloy containing magnesium is put into the storage tank 11, and then the heater 12 is operated. As a result, the aluminum alloy is melted, and the molten aluminum alloy L is stored in the storage tank 11.

Then, the depressurization step is carried out. In the depressurizing step, the on-off valve 45 is opened and the vacuum pump 41 is operated. As a result, the internal space of the storage container 13 is exhausted, and the internal pressure of the storage container 13 is reduced to a predetermined low pressure.

When the internal pressure of the container 13 is set to a predetermined low pressure by carrying out the depressurizing step, the raw material particle charging step is carried out. In the raw material particle charging step, nitrogen gas is supplied from the first nitrogen gas cylinder 21 to the particle supply tank 27 via the first gas pipe 23, and nitrogen gas is mixed from the second nitrogen gas cylinder 22 via the second gas pipe 24. Supply to device 29. At this time, the flow rate of nitrogen gas flowing through the first gas pipe 23 is adjusted by the first gas flow rate adjusting valve 25, and the flow rate of nitrogen gas flowing through the second gas pipe 24 is adjusted by the second gas flow rate adjusting valve 26.

The nitrogen gas supplied from the first nitrogen gas cylinder 21 to the particle supply tank 27 is introduced into the quantitative supply device 28 together with the powder P in the particle supply tank 27. In the fixed quantity supply device 28, the transfer screw 282 rotates to supply the powder P at a constant flow rate to the mixing device 29 together with the nitrogen gas. In this mixing device 29, the powder P merges with the nitrogen introduced into the mixing device 29 from the second nitrogen gas cylinder 22. Then, the powder P is supplied from the outlet port 293 of the mixing device 29 together with the nitrogen gas as the carrier gas to the injection nozzle 32 in the storage container 13 through the powder transport pipe 30. At this time, the flow rate of the powder P flowing through the powder transport pipe 30 and being supplied to the injection nozzle 32 is adjusted by the powder flow rate adjusting valve 31.

The powder P supplied to the injection nozzle 32 is ejected from a discharge port formed at the lower end of the injection nozzle 32. Since the discharge port of the injection nozzle 32 faces downward so as to face the surface of the molten aluminum alloy L in the storage tank 11 as described above, the powder P ejected from the discharge port of the injection nozzle 32 is It is sprayed onto the molten aluminum alloy L so as to be driven into the molten aluminum alloy L in the storage tank 11. In this way, the powder P composed of the silicon dioxide particle group is charged into the molten aluminum alloy L.

While charging a predetermined amount of powder P into the molten aluminum alloy L in the raw material particle charging step, the molten aluminum alloy L is stirred by the stirring device 14 and held at a predetermined temperature for a predetermined time. At this time, the strengthened particle generation step is executed. In the reinforcing particle generation step, the reduction reaction shown below proceeds from the surface of the silicon dioxide particles constituting the powder P in the molten aluminum alloy L.
2SiO ₂ + 2Al + Mg → MgAl ₂ O ₄ + 2Si

By the above-mentioned reduction reaction, the silicon dioxide particles constituting the powder P react with aluminum and magnesium in the molten aluminum alloy, and silicon is released from the silicon dioxide particles into the molten aluminum alloy and the silicon dioxide particles. Changes to particles containing MgAl ₂ O ₄ as a main component. Further, in the process of forming the particles, aluminum permeates into the particles to generate reinforced particles in which the main component is MgAl ₂ O ₄ and aluminum is mixed. In this way, in the reinforcing particle generation step, reinforcing particles containing the main component represented by MgAl ₂ O ₄ and aluminum are produced. The generated reinforcing particles are uniformly dispersed in the molten aluminum alloy L by stirring the molten aluminum alloy L by the stirring device 14.

After that, the stirring device 14 is stopped and the heating by the heater 12 is stopped to cool the molten aluminum alloy in the storage tank 11. Alternatively, the molten aluminum alloy in the storage tank 11 is poured into a cooling mold to cool the molten aluminum alloy. As a result, the molten aluminum alloy L is solidified to produce the particle-reinforced aluminum composite material according to the present embodiment.

The particle-reinforced aluminum composite material produced as described above has a base material composed of an aluminum alloy and reinforced particles dispersed in the base material. Then, as described above, the reinforcing particles contain a main component represented by MgAl ₂ O ₄ and aluminum. The content of aluminum contained in the reinforcing particles is higher than the content of Al (38 wt%) in the MgAl ₂ O ₄ particles (spinel particles).

Further, the content of silicon contained in the molten aluminum alloy L increases as the above reaction proceeds because silicon is released into the molten aluminum alloy. In this case, the amount of powder P supplied to the molten aluminum alloy so that the final silicon content is higher than the silicon content of 12.6 wt% at the eutectic point of the aluminum-silicon alloy. Is adjusted. As a result, β (Si) particles crystallize in the cooling process of the molten aluminum alloy. Therefore, β (Si) crystal grains are crystallized in the base material of the particle-reinforced aluminum composite material.

<Example 1: Confirmation of shape and composition of reinforced particles in particle reinforced aluminum composite material>
Using the manufacturing apparatus 1 shown in FIG. 1, 50 kg of an aluminum alloy containing a magnesium component was melted in a storage tank 11 to prepare a molten aluminum alloy. The composition of the aluminum alloy used here is as follows.
-Silicon (Si): 6.3 wt%
-Magnesium (Mg): 0.4 wt%
-Iron (Fe): 0.4 wt%
-Copper (Cu): 0.9 wt%
-Aluminum (Al): Remaining

Next, the pressure inside the storage container 13 was reduced to a predetermined low pressure. Then, while maintaining a predetermined low pressure, the powder P composed of the silicon dioxide particle group was charged (injected) into the molten aluminum alloy using the particle supply device 20. The added silicon dioxide has a purity of 99.5 wt%, a spherical shape, and a particle size of 10 μm or more and 50 μm or less. FIG. 2 shows an SEM image of the charged silicon dioxide particles.

Further, while the powder P composed of the silicon dioxide particle group was put into the molten aluminum alloy, the molten aluminum alloy was stirred and held at a predetermined temperature (750 ° C.) for a predetermined time (for example, 120 minutes). As a result, the above-mentioned reduction reaction occurs, and reinforcing particles containing the main component represented by MgAl ₂ O ₄ and aluminum are generated in the molten aluminum alloy. In order to make up for the magnesium deficiency due to the progress of this reduction reaction, solid magnesium was appropriately added into the molten aluminum alloy.

After a lapse of a predetermined time, the molten aluminum alloy was poured into a cooling mold and cooled and solidified. As a result, sample S1 of the particle-reinforced aluminum composite material according to Example 1 was prepared. The prepared sample S1 was cut and the cross-sectional structure was observed. 3 and 4 show SEM images of the cross section of sample S1. As is well shown in FIG. 3, reinforcing particles are formed in the base material of the aluminum composite material. The shape of the reinforcing particles is substantially spherical, and the diameter thereof is about 10 μm to 50 μm. That is, the diameter of the generated reinforcing particles is substantially equal to the diameter of the charged silicon dioxide particles. Further, the interface of the reinforcing particles is sufficiently adhered to the base material, and there is no gap between the interface of the reinforcing particles and the base material. Therefore, it is considered that there is no formation of defective particles such that a gap is formed between the interface of the reinforcing particles and the base material. The average particle diameter (median diameter) of the strengthened particles is 10 μm or more. Since the diameter of the strengthened particles generated as described above is almost equal to the diameter of the silicon dioxide particles to be charged, the average particle size of the strengthened particles to be generated is adjusted to 10 μm or more by adjusting the diameter of the silicon dioxide particles to be charged. be able to.

5A and 5B are SEM images obtained by enlarging a part of the reinforcing particles. As shown in FIGS. 5A and 5B, most of the reinforcing particles are composed of spinel (MgAl ₂ O ₄ ). In addition, the part that appears white so as to adhere to the spinel indicates metallic aluminum. As described above, it was confirmed that the reinforcing particles prepared in this example had a structure in which the main component was MgAl ₂ O ₄ and metallic aluminum was partially mixed.

Although the mechanism of forming such strengthened particles, specifically, the mechanism of mixing aluminum with the strengthened particles containing MgAl ₂ O ₄ as a main component is not always clear, the silicon dioxide particles are made of aluminum in the raw material particle charging step. By injecting the silicon dioxide particles into the molten aluminum alloy by spraying (driving) it into the molten alloy, the wettability between the silicon dioxide particles and the molten aluminum alloy is improved, which sequentially starts from the entire surface of the silicon dioxide particles. It can be considered that this is because the molten aluminum permeates the inside of the particles when the molten alloy causes the above-mentioned reduction reaction.

<Example 2: Investigation of the relationship between the material composition of the reinforced particles and the particle hardness>
A predetermined amount of pure aluminum (purity: 99.57 wt%) and an aluminum-10 wt% magnesium ingod were placed in a 100 cc crucible and mixed. Then, it was heated to 750 ° C. in an electric furnace to melt them, and a molten aluminum alloy containing magnesium was prepared. Further, by variously changing the amount of pure aluminum and the amount of aluminum-10 wt% magnesium as shown in the columns of each sample S2 to S8 in Table 1, a plurality of molten aluminum alloys having different magnesium concentrations were prepared. Then, under a predetermined reduced pressure, the silicon dioxide particle group (purity: 99.5 wt%, shape: spherical, particle diameter: 10 μm or more) was added to the molten aluminum alloy prepared by using the particle supply device 20 shown in FIG. The powder P was charged into the molten aluminum alloy by spraying the powder P composed of 50 μm or less). Then, the temperature of the molten aluminum alloy after the introduction of the silicon dioxide particles (powder P) was maintained at 750 ° C. for 10 minutes. After 10 minutes had passed, the molten aluminum alloy was solidified by natural cooling to prepare samples S2 to S8 of a plurality of particle-reinforced aluminum composite materials.

The concentration of each element constituting the strengthened particles contained in each of the prepared samples S2 to S8 was calculated using SEM / EDX (scanning electron microscope / energy dispersive X-ray spectroscopy). At the same time, the hardness of the strengthened particles contained in each sample S2 to S8 was measured with a Micro Vickers hardness tester (load: 10 g), and the relationship between the material composition of the strengthened particles and the hardness was investigated. The hardness of the reinforced particles in the sample S1 of the particle-reinforced aluminum composite material produced by the method shown in Example 1 and the spinel particles (manufactured by Wako Pure Chemical Industries, Ltd., purity 99 wt%, particle diameter 45 μm or less) are also included. And measured. Table 2 shows the elemental analysis results and hardness of each strengthened particle.

In Table 2, the content of magnesium in the strengthened particles according to sample S2 is very small, and it is considered that MgAl ₂ O ₄ cannot be said to be the main component. Therefore, sample S2 is not the strengthening particle according to the embodiment of the present invention. On the other hand, the main component of the strengthening particles according to the samples S1 and S3 to S8 is considered to be MgAl ₂ O ₄ . That is, these samples (S1, S3 to S8) are particle-reinforced aluminum composite materials according to the embodiment of the present invention.

The hardness of the reinforced particles contained in the sample (S1, S3 to S8) of the particle-reinforced aluminum composite material according to the present embodiment shown in Table 2 is 1106.0 to 1367.0 [Hv], and the hardness of the spinel particles (1682). It can be seen that it is lower than .2 [Hv]). Therefore, it can be seen that the machinability of the particle-reinforced aluminum composite material according to the present embodiment is better than the machinability of the particle-reinforced aluminum composite material containing spinel particles. Further, it can be seen that the higher the magnesium concentration in the strengthened particles and the lower the aluminum concentration in the strengthened particles, the higher the hardness of the strengthened particles. In particular, it was confirmed that the hardness of the strengthened particles was lower than the hardness of the spinel particles when the magnesium concentration in the strengthened particles was 16 wt% or less and the aluminum concentration was 40 wt% or more. Therefore, the reinforcing particles in the particle-reinforced aluminum composite material preferably contain MgAl ₂ O _{4 as the} main component, have a magnesium concentration of 16 wt% or less, and have an aluminum concentration of 40 wt% or more.

Further, from the results shown in Table 2, the reinforcing particles contained in the particle-reinforced aluminum composite material according to the present embodiment are 40 wt% or more and 50 wt% or less of aluminum, 5 wt% or more and 16 wt% or less of magnesium, and 40 wt%. It can be seen that oxygen containing 50 wt% or less and unavoidable impurities are contained, and the total mass concentration of these is 100 wt%.

<Example 3: Investigation of the relationship between the content of reinforced particles and Young's modulus due to the difference in Si concentration in the aluminum alloy base material>
In the storage tank 11 of the manufacturing apparatus 1 shown in FIG. 1, the composition similar to the composition shown in Example 1 (Al-6.3 wt% Si-0.4 wt% Mg-0.4 wt% Fe-0.9 wt%). 50 kg of an aluminum alloy of Cu) was melted to prepare a molten aluminum alloy, and then the pressure inside the storage container 13 was reduced. Next, using the particle supply device 20, a powder P composed of 8.35 kg of silicon dioxide particle group (SiO ₂ purity 99.5%, spherical, particle diameter 10 μm to 50 μm) is mixed with a carrier gas (nitrogen gas) into an aluminum alloy. The powder P was put into the molten aluminum alloy by spraying on the molten metal. Then, the molten aluminum alloy was held at a predetermined temperature for a predetermined time to generate reinforcing particles in the molten aluminum alloy. Further, in order to make up for the magnesium deficiency, the magnesium alloy was appropriately charged into the molten aluminum alloy in the storage tank 11.

Since the reinforcing particles generated in the molten aluminum alloy tend to settle in the molten aluminum alloy, the content (concentration) of the reinforcing particles in the molten aluminum alloy changes depending on the vertical position of the storage tank 11. Utilizing this, a part of the molten aluminum alloy is extracted from a plurality of positions in the storage tank 11 having different vertical positions, and the extracted molten aluminum alloy is cooled and solidified to increase the content of the strengthened particles (particle content). A plurality of particle-reinforced aluminum composite materials having different) were prepared as sample S9. Immediately before taking out the molten aluminum alloy from the storage tank 11, the silicon concentration in the molten aluminum alloy was measured using an emission spectroscopic analyzer and found to be 13.5 wt%. Therefore, the content of silicon in the base material of sample S9 is 13.5 wt%.

Further, the amount of the powder P composed of the silicon dioxide particle group charged into the molten aluminum alloy was 1.4 kg, and the reinforcing particles were generated in the molten aluminum alloy in the same manner as described above. Then, a part of the molten aluminum alloy is extracted from a plurality of positions where the vertical positions of the storage tank 11 are different, and the extracted aluminum alloy molten metal is cooled and solidified to sample a plurality of particle-reinforced aluminum composite materials having different particle contents. It was produced as S10. Immediately before taking out the molten aluminum alloy from the storage tank 11, the silicon concentration in the molten aluminum alloy was measured using an emission spectroscopic analyzer, and the silicon concentration was 7.1 wt%. Therefore, the content of silicon in the base material of sample S10 is 7.1 wt%.

One of the prepared samples S9 and one of the samples S10 were cut, and the cut cross section was observed. FIG. 6 shows an SEM image of a cross section of the sample S9, and FIG. 7 shows an SEM image of a cross section of the sample S10. In FIG. 6, in addition to the strengthening particles represented by the substantially spherical black portion, the structure represented by the gray portion was observed. Analysis of this tissue revealed β (Si). That is, in sample S9, it was confirmed that β (Si) particles were crystallized in the base material. On the other hand, in sample S10 shown in FIG. 7, although reinforcing particles represented by spherical black portions are observed in the aluminum alloy base material, the structure considered to be β (Si) as shown in FIG. 6 is not crystallized. ..

In the production of sample S9, the molten aluminum alloy immediately before cooling contains silicon higher than the silicon concentration (12.6 wt%) at the eutectic point of the aluminum-silicon alloy. Therefore, it is considered that β (Si) particles crystallized during the cooling process of the molten aluminum alloy. On the other hand, in the production of sample S10, the concentration of silicon contained in the molten aluminum alloy immediately before cooling is less than the silicon concentration (12.6 wt%) at the co-crystal point of the aluminum-silicon alloy, so that the aluminum alloy It is considered that β (Si) particles do not crystallize during the cooling process of the molten metal.

Further, each of the produced samples S9 was processed to 60 mm × 10 mm × t (thickness) 2 mm in order to measure the rigidity (Young's modulus) of the material. Then, the Young's modulus was calculated for each of the processed samples S9 using an elastic modulus measuring device (manufactured by Nippon Techno Plus Co., Ltd., JE-RT type). Similarly, each of the prepared samples S10 was processed in the same manner as described above, and Young's modulus was calculated using the same apparatus. Then, the relationship between the particle content and Young's modulus was investigated for each of the samples S9 and S10.

FIG. 8 is a graph showing the relationship between the particle content and Young's modulus for each of Sample S9 and Sample S10. In FIG. 8, the points indicated by the squares indicate the relationship between the particle content and Young's modulus of the sample S9, and the points indicated by the diamonds are the points of the particle content and Young's modulus of the sample S10. It is a point that shows the relationship. As can be seen from FIG. 8, in the region where the particle content is 20 to 25%, the Young's modulus of the sample S9 is higher than the Young's modulus of the sample S10. Specifically, the Young's modulus of sample S9 is improved by about 11% with respect to the Young's modulus of sample S10. It is considered that this is because β (Si) particles are crystallized in the base material of the particle-reinforced aluminum composite material according to sample S9 to improve the rigidity of the base material. Therefore, from the viewpoint of improving the rigidity, it is preferable that the base material contains more than 12.6 wt% of silicon. Further, it is preferable that the base material contains β (Si) particles.

<Example 4: Miniaturization of β (Si) particles>
The crystallized product containing β (Si) particles crystallized in the aluminum alloy base material shown in Example 3 tends to be coarsened when the molten aluminum alloy is cooled at a normal cooling rate. These coarsened crystals are characterized by low elongation, hard, brittle, and fragile. Therefore, the particle-reinforced aluminum composite containing such crystallization may also have low elongation, be hard, brittle, and fragile. Therefore, in Example 4, an attempt was made to refine the crystallized product containing β (Si) crystallized in the aluminum alloy base material. In this case, first, a plate-shaped particle-reinforced aluminum composite material (hereinafter referred to as an aluminum composite plate) was produced by the same production method as the production method of sample S9 of Example 3. The composition of the main components constituting the base material in the produced aluminum composite plate was as follows.
・ Si: 13.5 wt%
-Cu: 1.0 wt%
・ Mg: 0.5 wt%
-Al: Remaining The particle size of the reinforced particles in the produced aluminum composite plate was 10 μm or more and 50 μm or less, and the particle mixing ratio was 20 to 25%.

Next, a predetermined area of the produced aluminum composite plate was rubbed and stirred using a friction stir tool. FIG. 9 is a schematic view of the friction stir tool used and the aluminum composite plate that is friction stir. As shown in FIG. 9, the aluminum composite plate 50 is formed in a plate shape. The long region R surrounded by the broken line in the aluminum composite plate 50 is a predetermined region to be frictionally agitated. Further, the friction stir tool 60 has a tool body 61 and a probe 62. The tool body 61 is formed in a stepped cylindrical shape, and one end (upper end in FIG. 9) 61a is connected to the drive source. The tool body 61 rotates about an axis by driving the drive source. The other end surface of the tool body 61 constitutes a shoulder 61b that comes into contact with the surface of the work material, and the probe 62 is formed so as to project from the shoulder 61b. As can be seen from FIG. 9, the probe 62 is formed in a tapered truncated cone shape, and is connected to the tool body 61 so that its axis is coaxial with the axis of the tool body 61. Therefore, when the drive source is driven, the tool body 61 and the probe 62 rotate integrally around the axis.

When the aluminum composite plate 50 is frictionally agitated using the friction stir tool 60, the probe 62 is placed on the surface of one end of a predetermined region R of the aluminum composite plate 50 from the tip thereof while rotating the friction stir tool 60. Press as shown by arrow A. As a result, frictional heat is generated by rubbing the surface of the aluminum composite plate 50 while the probe 62 rotates, and the frictional heat softens the surface of the aluminum composite plate 50. Therefore, the probe 62 enters so as to be buried inside the aluminum composite plate 50. After the probe 62 is inserted into the aluminum composite plate 50 until the shoulder 61b of the friction stir tool 60 comes into contact with the surface of the aluminum composite plate 50, the probe 62 is rotated while rotating the friction stir tool 60, as shown by the arrow B in FIG. It is horizontally moved in the longitudinal direction of the region R. As a result, the tissue in the predetermined region R is frictionally agitated by the probe 62. In this example, the rotation speed of the friction stir tool is set to 1000 rpm, and the feeding speed (moving speed) in the horizontal direction is set to 200 mm / min. Was set to, and friction stir welding was performed.

After the friction stir welding, a part of the predetermined region R (hereinafter referred to as a modified layer) that was frictionally agitated was cut and taken out. The cut surface of the modified layer taken out was polished, and the structure of the polished surface was observed with a metallurgical microscope. FIG. 10 shows a photographic image of a cross section of the tissue observed with a metallurgical microscope as Example 4. For reference, FIG. 10 also includes a photographic image obtained by observing the cross section of the structure of the portion of the aluminum composite plate 50 other than the modified layer with a metallurgical microscope as Example 3. Shown.

As shown in FIG. 10, β (Si) particles and eutectic Si particles are contained in the aluminum alloy base material in both the case where friction stir welding is performed (Example 4) and the case where friction stirring is not performed (Example 3). Is included. If the concentration of Si contained in the molten aluminum alloy is less than the eutectic point (12.6 wt%), the eutectic Si particles crystallize during the cooling process of the molten alloy, but the β (Si) particles crystallize. I will not put it out. On the other hand, when the concentration of Si contained in the molten aluminum alloy exceeds the eutectic point, β (Si) particles are crystallized as described above, and eutectic Si particles are also crystallized. The β (Si) particles crystallize in a mass, and the eutectic Si particles crystallize in a needle shape. Further, the particle area ratio in the photographic image according to Example 4 (the ratio of the area of particles (reinforced particles) to the total area of the aluminum alloy in the photographic image) is 22.4%, and the particles in the photographic image according to Example 3 The area ratio was 21.6%. From this, it can be seen that the particle area ratio did not change so much before and after the friction stir welding.

Further, as can be seen by comparing the photographic image according to Example 3 in which friction stir welding is not performed with the photographic image according to Example 4 in which friction stir welding is performed, β (β (containing) contained in the aluminum alloy base material according to Example 4 can be seen. The sizes of the Si) particles and the eutectic Si particles are smaller than the sizes of the β (Si) particles and the eutectic Si particles contained in the aluminum alloy base material according to Example 3 in which friction stir welding is not performed. On the other hand, the size of the reinforcing particles in the aluminum alloy base material according to Example 4 is not so different from the size of the reinforcing particles in the aluminum alloy base material according to Example 3 in which friction stir welding is not performed. From this, it can be seen that the β (Si) particles and the eutectic Si particles can be miniaturized by friction stir welding without significantly changing the diameter of the strengthening particles. In other words, it can be seen that the crystallization containing β (Si) particles crystallized in the cooling process of the molten aluminum alloy can be miniaturized by friction stir welding without causing cracking of the strengthened particles. When the particle-reinforced aluminum composite material in which the reinforcing particles are spinel particles is subjected to friction stir welding, there is a high possibility that the spinel particles will crack. Therefore, by frictionally stirring the particle-reinforced aluminum composite material containing the reinforcing particles according to the present embodiment, it is possible to refine the crystallized product without breaking the reinforcing particles. Further, when the photographic image according to Example 4 was observed, no particle defect such as a crack (chip) of β (Si) particles was found. From this, it can be seen that β (Si) particles can be miniaturized by friction stir welding without causing cracks.

Further, the particle size distribution of the crystallized product containing β (Si) particles crystallized in the aluminum alloy base material from the photographic image according to Example 3 and the photographic image according to Example 4 taken by using image analysis software. I examined. FIG. 11A shows the particle size distribution measurement result of the crystallized product according to Example 3, and FIG. 11B shows the particle size distribution measurement result of the crystallized product according to Example 4. From the measurement results of the particle size distribution shown in FIGS. 11A and 11B, the average particle diameter (median diameter) of the crystallized product according to Example 3 was 6,32 μm, and the maximum particle diameter was 187.62 μm. On the other hand, the average particle size (median diameter) of the crystallized product according to Example 4 was 3.47 μm, and the maximum particle size was 48.40 μm. From this, it can be seen that the crystallized product was made finer by friction stir welding. In the measurement of the particle size distribution, when the shape of the particles was a different diameter shape, the maximum diameter or the maximum length was measured as the particle diameter.

<Measurement of tensile strength and elongation>
Tensile test pieces (JIS Z2241) from the modified layer in which friction stir welding was performed according to Example 4 and the portion (aluminum composite plate 50 other than the modified layer) according to Example 3 in which friction stir welding was not performed, respectively. No. 14A) was cut out, and a tensile test was carried out using an autograph (manufactured by Shimadzu Corporation: AG-X (100 kN)), and the tensile strength and the amount of elongation until the test piece broke were measured. FIG. 12 shows the tensile test results, and FIG. 13 shows the measurement results of the elongation amount.

As can be seen from FIGS. 12 and 13, the tensile strength and elongation of the tensile test piece according to Example 4 are larger than the tensile strength and elongation of the tensile test piece according to Example 3. Specifically, the tensile strength (291.9 MPa) of the tensile test piece according to Example 4 was improved by 13% with respect to the tensile strength (259.3 MPa) of the tensile test piece according to Example 3, and in Example 4. The elongation amount (1.2%) of the tensile test piece is about four times the elongation amount (0.3%) of the tensile test piece according to Example 3. From this, by refining the crystallized products (specifically, β (Si) particles and eutectic Si particles) containing β (Si) particles crystallized in the aluminum alloy base material by friction stir welding, the tensile strength is obtained. It can be seen that the strength and ductility are improved. In particular, when the average particle size (median diameter) of the crystallized particles containing β (Si) particles crystallized in the aluminum alloy base material is 5 μm or less, more preferably 3.5 μm or less, and the aluminum alloy base material. It can be seen that when the maximum particle size of the crystallized product containing β (Si) particles crystallized in the material is 50 μm or less, the tensile strength and ductility of the particle-reinforced aluminum composite material are improved.

<Example 5: Confirmation of influence on tensile strength and elongation by heat treatment>
The modified layer according to Example 4 was cut out and heat-treated (T6 treatment) to prepare the modified layer according to Example 5. A tensile test piece (JIS Z2241 14A) was cut out from the prepared modified layer according to Example 5, and a tensile test was carried out using an autograph (manufactured by Shimadzu Corporation: AG-X (100 kN)). The tensile strength and elongation of the tensile test piece were measured. FIG. 14 shows the tensile test results, and FIG. 15 shows the measurement results of the elongation amount. For reference, FIG. 14 also shows the tensile strength of the tensile test piece according to Example 3, and FIG. 15 also shows the elongation amount of the tensile test piece according to Example 3.

As can be seen from FIG. 14, the tensile strength (327.6 MPa) of the tensile test piece according to Example 5 is higher than the tensile strength (259.3 MPa) of the tensile test piece according to Example 3. Specifically, the tensile strength of the tensile test piece according to Example 5 in which the modified layer was heat-treated was improved by 26% with respect to the tensile strength of the tensile test piece according to Example 3. On the other hand, as can be seen from FIG. 15, the elongation amount (0.6%) of the tensile test piece according to Example 5 in which the modified layer is heat-treated is the elongation amount (0.) of the tensile test piece according to Example 3. It is about twice that of 3%).

Further, as can be seen by comparing FIG. 12 and FIG. 14, when the modified layer is heat-treated (in the case of Example 5), it is compared with the case where the heat treatment is not performed (in the case of Example 4). As a result, the tensile strength is further improved. On the other hand, as can be seen by comparing FIG. 13 and FIG. 15, when the modified layer is heat-treated (in the case of Example 5), it is not heat-treated (in the case of Example 4). The amount of elongation decreases as compared with. Therefore, when applied to a member requiring higher tensile strength, it is preferable to heat-treat the modified layer. On the other hand, when applied to a member requiring a larger amount of elongation (ductility), it is preferable not to heat-treat the modified layer.

<Example 6: Application to pressure resistant parts>
The particle-reinforced aluminum composite material shown in the present embodiment can be applied to a pressure-resistant component having a strength that can withstand a predetermined pressure and the applied pressure. In this case, the strength of the pressure-resistant component can be increased, and the machinability can also be improved.

In particular, among the particle-reinforced aluminum composite materials according to the present embodiment, the particle-reinforced aluminum composite material in which β (Si) particles are contained in the aluminum alloy base material may be used for the pressure-resistant component. That is, the pressure-resistant component is composed of a particle-reinforced aluminum composite material containing a base material made of an aluminum alloy and reinforcing particles dispersed in the base material, and the reinforcing particles are represented by MgAl ₂ O _4. It is preferable that the base material contains the main component and aluminum, and the base material contains crystallization containing β (Si) particles. By configuring the pressure-resistant component in this way, the strength can be increased, the machinability can be improved, and the rigidity can be improved.

When the pressure-resistant component has a stress-concentrated portion where stress is concentrated by the applied pressure, the size of the crystallized product containing β (Si) particles contained in the aluminum alloy base material constituting the stress-concentrated portion. However, it is preferable that the size is smaller than the size of the crystallized product containing β (Si) particles contained in the aluminum alloy base material constituting the portion other than the stress concentration portion. That is, it is preferable that the crystallized material at the stress concentration site is miniaturized. In this case, the average particle diameter (median diameter) of the crystallized material containing β (Si) contained in the aluminum alloy base material constituting the stress concentration site is 5 μm or less, and the maximum particle diameter is 50 μm or less. When the object is made finer, the tensile strength and ductility of the stress concentration site are further enhanced. Therefore, it is possible to effectively suppress the breakage of the stress concentration portion due to stress, and it is possible to further improve the durability (pressure resistance characteristic) of the pressure resistant component.

As such a pressure-resistant component, a caliper body used in a vehicle braking device can be preferably mentioned.

FIG. 16 is a schematic view of the caliper body. Further, FIG. 17 is a schematic cross-sectional view of the brake device to which the caliper body of FIG. 16 is assembled. The cross section of the caliper body shown in FIG. 17 is a cross section obtained by cutting the caliper body of FIG. 16 along the line AA.

As shown in FIGS. 16 and 17, the caliper body 80 is configured to have a cylinder portion 81, an opposing portion 82, and a connecting portion 83. These parts are integrally molded. The cylinder portion 81 is formed in a cylindrical shape so that a cylindrical space for accommodating the piston 91 is formed therein, and one end is opened and the other end is closed. Then, the piston 91 is mounted inside the cylinder portion 81 from one end of the opening. The piston 91 is housed in the cylinder portion 81 so as to be movable in the axial direction thereof. At this time, the hydraulic chamber P is formed in a liquidtight state between the bottom surface of the piston 91 and the other end surface of the cylinder portion 81.

Further, the connecting portion 83 is directed away from the cylinder portion 81 along the axial direction of the cylinder portion 81 from a predetermined region constituting the upper portion in FIGS. 16 and 17 of the opening edge of one end of the cylinder portion 81. It is extended to. A pair of reaction force arms 82a and 82b are provided so as to extend downward in FIGS. 16 and 17 from the extended end of the connecting portion 83. The facing portion 82 is formed by the pair of reaction force arms 82a and 82b. In this way, the connecting portion 83 connects the cylinder portion 81 and the facing portion 82. Further, the pair of reaction force arms 82a and 82b (opposing portions 82) are arranged to face the opening surface of the cylinder portion 81 in the moving direction (axial direction) of the piston 91.

As shown in FIG. 17, when the caliper body 80 is assembled to the brake device, a part of the disc rotor 92 attached to the vehicle is arranged between the cylinder portion 81 and the facing portion 82 which are arranged to face each other. .. Therefore, the cylinder portion 81 and the facing portion 82 face each other with the disc rotor 92 interposed therebetween, and the connecting portion 83 is arranged so as to straddle the outer circumference of the disc rotor 92.

The inner pad 93 is arranged between the opening surface of the piston 91 in the cylinder portion 81 and the disc rotor 92, and the outer pad 94 is arranged between the facing portion 82 and the disc rotor 92. The inner pad 93 and the outer pad 94 are supported by a mounting 95, which is a component of the braking device. Further, the caliper body 80 is movably supported in the axial direction of the cylinder portion 81 (axial direction of the piston 91) via a slide pin (not shown) on the mounting 95.

In such a braking device, when the driver steps on the brake pedal while the vehicle is running (while the disc rotor 92 is rotating), the hydraulic pressure in the hydraulic chamber P increases, so that the piston 91 moves to the left in FIG. Moving. Then, the inner pad 93 also moves to the left due to the movement of the piston 91 and is pressed against the disc rotor 92. On the other hand, as the hydraulic pressure in the hydraulic chamber P increases, the caliper body 80 moves to the right in FIG. Then, this movement is transmitted from the facing portion 82 (reaction force arm 82a) of the caliper body 80 to the outer pad 94, and the outer pad 94 moves to the right in FIG. 17 and is pressed against the disc rotor 92. In this way, the inner pad 93 and the outer pad 94 are pressed against the disc rotor 92 from both sides thereof. This pressing force acts on the disc rotor 92 as a frictional force, so that the disc rotor 92 brakes.

In the process of the brake operation described above, the hydraulic pressure in the hydraulic chamber P acts directly on the cylinder portion 81 of the caliper body 80. Due to this hydraulic pressure, stress acts on the cylinder portion 81 in the direction of arrow B in FIG. That is, stress acts in the direction in which the cylinder portion 81 opens. Further, a reaction force from the outer pad 94 acts on the facing portion 82. Due to this reaction force, stress acts on the facing portion 82 in the direction of arrow C in FIG. That is, stress acts in the direction in which the facing portion 82 opens.

Due to the stress acting in the direction of arrow B, the stress is concentrated on the boundary portion 84 between the cylinder portion 81 and the connecting portion 83. Further, due to the stress acting in the direction of arrow C, the stress is concentrated on the boundary portion 85 between the facing portion 82 and the connecting portion 83. That is, the boundary portion 84 and the boundary portion 85 are stress concentration sites.

As described above, the caliper body 80 is subjected to stress due to the hydraulic pressure and the reaction force based on the hydraulic pressure. The caliper body 80 is designed to withstand these stresses. That is, the caliper body 80 is a pressure resistant component. By forming the caliper body 80, which is such a pressure-resistant component, with the particle-reinforced aluminum composite material shown in the above embodiment, the pressure-resistant performance can be improved. In particular, the caliper body 80 is preferably composed of the particle-reinforced aluminum composite material shown in the present embodiment in which β (Si) particles are contained in the aluminum alloy base material. Specifically, the caliper body 80 is composed of a particle-reinforced aluminum composite material containing a base material made of an aluminum alloy and reinforcing particles dispersed in the base material, and the reinforcing particles are MgAl ₂ O ₄ It is preferable that the base material contains the main component represented by the above and aluminum, and the base material contains crystallization containing β (Si) particles. By configuring the caliper body 80 in this way, Young's modulus (rigidity) can also be improved.

Further, the caliper body 80 has boundary portions 84 and 85 where the acting stress is concentrated. The size of the crystallized material containing β (Si) particles crystallized in the aluminum alloy base material of the particle-reinforced aluminum composite material constituting the boundary portions 84 and 85 constitutes a portion other than the boundary portions 84 and 85. It is preferable that the size is smaller than the size of the crystallized product containing β (Si) particles crystallized in the aluminum alloy base material of the particle-reinforced aluminum composite material. That is, it is preferable that the crystallized material containing β (Si) particles crystallized in the aluminum alloy base material constituting the boundary portions 84 and 85 is miniaturized. In this case, the average particle diameter (median diameter) of the crystallized particles containing β (Si) particles in the aluminum alloy base material constituting the boundary portions 84 and 85 is 5 μm or less (preferably 3.5 μm or less), and the maximum particles. By setting the diameter to 50 μm or less, the tensile strength and ductility of the boundary portions 84 and 85 are further improved. By further increasing the strength of the boundary portions 84 and 85 in this way, the tensile strength and ductility of the boundary portions 84 and 85 are increased, whereby the durability of the caliper body 80 can be further improved.

In this case, the caliper body 80 (pressure resistant component) can be manufactured by a manufacturing method including the above-mentioned raw material particle input step, the above-mentioned strengthened particle generation step, a molding step, and a miniaturization step. Here, in the molding step, the molten aluminum alloy is cooled after the reinforcing particle generation step to crystallize the crystallized product containing β (Si) particles in the aluminum alloy base material and solidify the molten aluminum alloy. This is a step of molding (for example, casting) the caliper body 80 (pressure resistant part). In the miniaturization step, the boundary portions 84,85 (stress concentration portion) of the molded caliper body 80 (pressure resistant parts) are frictionally agitated to form the boundary portions 84,85 (stress concentration portion) in the aluminum alloy base material. This is a step of refining a crystallized product containing β (Si) particles crystallized in (1) to an average particle diameter of 5 μm or less and a maximum particle diameter of 50 μm or less. Specifically, in this miniaturization step, after the caliper body 80 is molded (for example, cast molding) by the aluminum composite material described in the present embodiment, the inner side surfaces (facing the disc rotor 92) of the boundary portion 84 and the boundary portion 85 are formed. The friction stir tool 60 shown in the above embodiment is pressed from the surface) while rotating to allow the probe 62 to enter the inside of the boundary portions 84 and 85, and in that state, the probe 62 is in the entire region of the boundary portions 84 and 85 or a predetermined value. The friction stir tool 60 is moved so as to spread over the area of. As a result, the boundary portions 84 and 85 are agitated by friction, and β (Si) particles and eutectic Si particles in the aluminum alloy base material constituting the boundary portions 84 and 85 are produced with an average particle diameter (median diameter) of 5 μm or less and a maximum. The particle size can be reduced to 50 μm or less.

Incidentally, as a means for refining the crystallized product containing β (Si) particles crystallized in the aluminum alloy base material, a means for adding an additive to the molten aluminum alloy can be considered. However, in this case, the crystallized product is miniaturized in the entire molded product. On the other hand, by adopting the above-mentioned method, that is, a method of rubbing and stirring a specific part after molding (for example, after casting) of a product (pressure resistant part) to miniaturize the crystallization existing in the part. The crystallized product can be refined only for a specific part of the molded product. Therefore, this method is useful as a means for refining the crystallized product only in the portion where tensile strength or ductility is required, that is, the stress concentration portion.

In the above example, the floating type caliper body is illustrated as the caliper body 80 as the pressure resistant component, but the present invention can also be applied to the opposed type caliper body. In this case, the facing portion is a cylinder portion, and the boundary portion is a boundary portion between both cylinder portions and the connecting portion.

Although the embodiments of the present invention have been described above, the present invention should not be limited to the above embodiments. For example, in the above embodiment, the caliper body 80 has been described as a pressure resistant component, but the present invention can be applied to other pressure resistant components. The present invention can be modified as long as it does not deviate from the gist thereof.

1 ... Manufacturing equipment, 10 ... Molten metal storage unit, 11 ... Storage tank, 12 ... Heater, 13 ... Storage container, 20 ... Particle supply device, 27 ... Particle supply tank, 32 ... Injection nozzle, 40 ... Decompression device, 50 ... Aluminum composite plate, 60 ... Friction stirring tool, 61 ... Tool body, 62 ... Probe, 80 ... Caliper body (pressure resistant part), 81 ... Cylinder part, 82 ... Opposing part, 82a, 82b ... Reaction force arm (opposing part), 84, 85 ... Boundary part, 91 ... Piston, L ... Aluminum alloy molten metal, P ... Powder

Claims (11)

A particle-reinforced aluminum composite material containing a base material composed of an aluminum alloy and reinforcing particles dispersed in the base material.
The strengthening particles
Principal components represented by MgAl ₂ O ₄ and
With aluminum
Including particle reinforced aluminum composites. In the particle-reinforced aluminum composite material according to claim 1,
A particle-reinforced aluminum composite material containing 40 wt% or more of aluminum in the reinforced particles. In the reinforced aluminum composite material according to claim 1 or 2.
The strengthening particles
40 wt% or more of aluminum and
Magnesium of 16 wt% or less and
Including particle reinforced aluminum composites. In the particle-reinforced aluminum composite material according to any one of claims 1 to 3.
A particle-reinforced aluminum composite material containing 20 wt% or less of silicon in an amount of more than 12.6 wt% in the base material. In the particle-reinforced aluminum composite material according to any one of claims 1 to 4.
A particle-reinforced aluminum composite material containing crystals containing β (Si) particles in the base material. In the particle-reinforced aluminum composite material according to any one of claims 1 to 5.
A particle-reinforced aluminum composite material having an average particle diameter of 10 μm or more. In the particle-reinforced aluminum composite material according to claim 5.
The crystallized product containing β (Si) particles has at least one of a particle size having an average particle size of 5 μm or less and a maximum particle size of 50 μm or less. Particle reinforced aluminum composite. A pressure-resistant component having a strength that can withstand a predetermined pressure and the applied pressure.
It is composed of a particle-reinforced aluminum composite material containing a base material composed of an aluminum alloy and reinforcing particles dispersed in the base material, and the reinforcing particles are composed of a main component represented by MgAl ₂ O ₄ and aluminum. A pressure-resistant component containing, and, in the base metal, crystallization containing β (Si) particles. In the pressure-resistant component according to claim 8,
It has a stress concentration site where stress is concentrated by the applied pressure,
The size of the crystallized material contained in the base material constituting the stress concentration site is smaller than the size of the crystallized product contained in the base material constituting the site other than the stress concentration site. Pressure resistant parts. In the pressure-resistant component according to claim 9,
The pressure-resistant component is a caliper body that constitutes a braking device mounted on a vehicle.
The caliper body
A cylinder that houses the piston so that it can move in the axial direction,
With respect to the cylinder portion, the facing portion is arranged so as to be separated from the cylinder portion in the moving direction of the piston.
It has a connecting portion that connects the cylinder portion and the facing portion.
A pressure-resistant component in which the stress concentration portion is at least one of a boundary portion between the cylinder portion and the connecting portion and a boundary portion between the facing portion and the connecting portion. A method for manufacturing a pressure-resistant component having a strength that can withstand a predetermined pressure and a stress concentration portion where the stress is concentrated by the applied pressure.
A raw material particle charging process in which powders made of silicon dioxide particles are charged into a molten aluminum alloy containing magnesium.
By reacting the silicon dioxide particles charged into the molten aluminum alloy in the raw material particle charging step with magnesium and aluminum which are the components of the molten aluminum alloy, the main component represented by MgAl ₂ O ₄ and aluminum Reinforcement particle generation process to generate reinforcement particles including
By cooling the molten aluminum alloy, crystallization containing β (Si) particles is crystallized in the base metal of the aluminum alloy, and the molten aluminum alloy is solidified to form the pressure-resistant component.
By frictionally stirring the stress-concentrated portion of the molded pressure-resistant component, the crystallized material crystallized in the aluminum alloy base material constituting the stress-concentrated portion has an average particle diameter of 5 μm or less and a maximum particle diameter of 50 μm or less. And the miniaturization process
Manufacturing methods for pressure resistant parts, including.