JP2014201762A - Composite material with crystal grains of base material micronized and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance strength of a composite material containing metals such as Al and the like as a base material, which are light but has low strength.SOLUTION: A composite material contains a compound dispersed in a base metal, which is produced during casting and serves as heterogeneous nuclei, or the composite material is produced by increasing a cooling rate during solidification by adding powder, which is the same as the base material, before casting, thereby enhancing strength of the base metal by micronizing crystal grains thereof. A method of producing a composite material comprises mixing powder of a base metal with powder which forms a compound with the base metal, charging the mixed powder into a mold which rotates and pouring a molten base metal while applying centrifugal force to the mixed powder to make the molten base metal react with the powder to form a compound which serves as heterogeneous nuclei or increasing the cooling rate during solidification by adding the powder to micronize crystal grains of the base metal.

Description

The present invention relates to a high-strength composite material in which base material crystal grains are made finer than before and a method for producing the same.

In recent years, development of lightweight and high-strength materials has been promoted. One of them is a composite material using lightweight Al or the like as a base material. The composite material is a material in which the base material and the base material are combined with materials having different structures and compositions. Since the advantages of the combined materials can be combined, the composite material is expected to be applied to various fields such as a connecting rod for an internal combustion engine and a heat sink.

  As a method for producing a composite material, there are reactive centrifugal force mixed powder methods disclosed in Patent Document 1 and Non-Patent Document 1. In this manufacturing method, first, a mixed powder 1 is prepared by mixing a base metal powder and a substance powder that reacts with the base material to form a compound. After the mixed powder 1 is put into the cylindrical mold 2, the cylindrical mold 2 is rotated so that a centrifugal force is applied to the mixed powder 1, and the cylindrical mold 2 is spared as necessary. Heating is performed (see FIG. 1). Then, the base metal molten metal 4 melted in the melting furnace for casting is poured into the rotating cylindrical mold 2 through the runner 3 (see FIG. 2).

Due to the pressurizing effect of the centrifugal force, the base metal molten metal 4 is impregnated into the voids in the mixed powder, and at the same time, the base metal metal powder in the mixed powder 1 is dissolved by the heat of the molten metal. At this time, the base material and the substance powder react to produce a compound. By this manufacturing process, a composite material in which the compound is firmly fixed to the base metal and is uniformly or inclinedly dispersed in the base metal is manufactured.

JP 2011-184713 A

Shimaa El-Hadad, Hisashi Sato, Eri Miura-Fujiwara and Yoshimi Watanabe; Japan Journal of Applied Physics 50, (2011) 01A02.

  An object of the present invention is to solve the problem that when a composite material made of a metal such as Al, which is lightweight but has low strength, is produced, the strength of the composite material is reduced because the strength of the base material is low. That is.

The present inventors have found that the above problem can be solved by making the crystal grains of the base metal constituting the composite material fine. That is, according to the present invention, the following composite material and the manufacturing method thereof are provided.

[1] A composite material in which a compound serving as a heterogeneous nucleus generated during casting is dispersed in a base metal, and the crystal grain size of the base metal is 300 μm or less.

[2] The composite material according to [1], wherein a crystal grain size of the base metal is 100 μm or less.

[3] The composite material according to [1] or [2], wherein the size of crystal grains of the base metal changes in an inclined manner in the composite material.

[4] The composite material according to any one of [1] to [3], wherein the base metal is Al and the compound is Al ₃ Zr.

[5] The base metal powder is put into a mold, the melted base metal molten metal is poured while rotating the mold to give centrifugal force to the powder, and the heat of the base metal molten metal A method for producing a composite material in which the base metal powder is melted, the crystal grains are made finer, and the strength is higher than that of a base metal by centrifugal casting.

[6] Production of composite material according to [5] above, wherein the powder charged into the mold is a mixed powder of the base metal powder and a powder that generates a compound having good consistency with the base material. Method.

[7] The method for producing a composite material according to [6], wherein the base metal is Al, and the powder that forms the base material and the compound is Zr.

FIG. 2 is a schematic view of a method of introducing a mixed powder of a base metal powder and a substance powder that reacts with the base material to form a compound in the reactive centrifugal mixed powder method, which is the background art of the present invention, into a rotating cylindrical mold. FIG. It is the figure which drawn typically the method of pouring the base metal molten metal in the rotating cylindrical metal mold | die in the reactive centrifugal force mixed powder method which is the background art of this invention. It is the figure which drawn the manufacturing process of the composite material typically. It is the figure which showed the process chart of the composite material manufacturing method. It is an Al-based composite material composed of Al and Zr manufactured by the reactive centrifugal force mixed powder method of the first embodiment of the present invention. It was prepared by reacting the centrifugal force the mixed powder method in the first embodiment of the present invention, a reflected electron composition image of a scanning electron microscope cross-section of the Al-based composite material intermetallic compound Al 3 _Zr are generated. It is the graph which showed the result of the micro Vickers hardness test of the pure Al sample which is a preform | base_material part of the Al group composite material manufactured by the reactive centrifugal force mixed powder method in 1st Embodiment of this invention, and a comparison material. It is the photograph after the corrosion of the cross section of Al composite material manufactured in Example 2 of this invention. It is the graph which showed the result of the micro Vickers hardness test of the Al composite material manufactured in Example 2 of this invention, and the centrifugal cast product (comparative material) of Al.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

The composite material of the present invention is a composite material in which a compound serving as a heterogeneous nucleus generated during casting is dispersed in a base metal, and the crystal grain size of the base metal is preferably 300 μm or less, preferably 100 μm or less. More preferably. In the composite material of the present invention, another metal B that reacts with the base material to form a compound is dispersed in the metal A that is the base material, and the metal B sufficiently reacts with the base metal A. However, the metal B cannot completely react with the base metal A due to a lack of heat, and the compound of the metal B and the base metal A surrounds the periphery of the metal B so that the metal A and the metal B There is no problem even when the organization is generated at the boundary.

Furthermore, it is preferable that the crystal grains of the base metal A change in an inclined manner in the composite material. When the size of the crystal grains changes in an inclined manner, there is an advantage that the crystal grains are hard in a fine portion and that the processing is easy in a place where the crystal grains are coarse.

As shown in FIG. 3, the method for producing a composite material of the present invention produces a mixed powder 5 in which a base metal powder and a substance powder that reacts with the base metal to form a compound are produced, and the mixed powder After 5 is put into the cylindrical mold 6, the cylindrical mold 6 is rotated around the rotation shaft 7. The mixed powder 5 is fixed to the inner wall of the cylindrical mold 6 by applying a centrifugal force to the mixed powder 5. Then, by pouring the base metal molten metal 8 into the cylindrical mold 6, the substance powder that reacts with the base metal molten metal in the mixed powder 5 to form a compound reacts with the base material, An intermetallic compound having a small lattice constant difference and good consistency is generated. Since this intermetallic compound has good consistency, it acts as a heterogeneous nucleus on the base material. This promotes the refinement of crystal grains of the base material, and the composite material 9 with improved strength is manufactured. FIG. 4 shows a manufacturing flow of the composite material of the present invention.

Instead of the mixed powder 5, when the base metal molten metal is poured into a powder that is the same material as the base metal and the metal powder is melted, the cooling rate during solidification increases due to latent heat or the like, and the crystal grains of the base metal Can be obtained. Thus, even if it is a material made of only a base metal, when it has a crystal grain structure in which the size of crystal grains is partially different, it is called a composite material in a broad sense in the present invention.

In the method for producing a composite material of the present invention, more specifically, a powder is prepared by mixing Al powder as a base material, or Zr powder that reacts with the base material Al powder and Al powder to form a compound, By flowing Al melted into the mixed powder in a cylindrical mold into the cylindrical mold, the base material Al and Zr in the mixed powder react to form an intermetallic compound having good consistency with the base material Al. Al ₃ Zr is generated. This intermetallic compound Al ₃ Zr acts as a heterogeneous nucleus with respect to the base material Al because of its good compatibility with Al. This promotes the refinement of the crystal grains of the base material Al and produces a composite material with improved strength. In the case where a molten metal is poured into a powder that is the same material as the base metal and the metal powder is melted, Al is suitable as the base material, but not only Al but also other metals have the same effect. Is obtained.

  In addition, the shape of the metal mold | die used for manufacture of the composite material of this invention is not restrict | limited to the said cylindrical shape, It can apply suitably changing in the range which does not deviate from the meaning. For example, the present invention can be applied to other complicated shapes such as a triangular prism, a quadrangular prism, and a polygonal prism. Furthermore, the base material of the composite material of the present invention and the metal that generates the compound and the base material are not limited to the combination of Al and Zr described above, and other combinations can be used as long as the compatibility between the generated intermetallic compound and the base material is good. Is also applicable.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

(Example 1: Melting Al / Zr mixed powder with molten Al)
The composite material of the present invention is produced by a reactive centrifugal force mixed powder method. A mixed powder composed of 59.8 g of pure Al powder having a particle diameter of 100 to 150 μm as a base metal powder and 15.2 g of Zr powder having a particle diameter of 2 to 3 mm that reacts with the base material to form a compound, The mixed powder is put into a cylindrical mold having a cavity with a diameter of 80 mm and a width of 50 mm. On the other hand, 280 g of pure Al ingot, which is a base metal, is loaded into a melting furnace for casting. Thereafter, the cylindrical mold is heated to 600 ° C. and the pure Al ingot is heated to a melting temperature of 800 ° C. in a vacuum to obtain a base material molten pure Al. Then, the cylindrical mold is rotated, and a centrifugal force of gravity multiple 1119G (gravity multiple 1G corresponds to the gravitational field) is applied to the mixed powder, so that the base material molten pure Al is poured into the cylindrical mold. Through this manufacturing process, an Al-based composite material in which the base metal pure Al was refined as shown in FIG. 5 was manufactured. FIG. 6 is a reflected electron composition image of the cross section of the cast material, and it can be seen that the intermetallic compound Al ₃ Zr is generated at the interface between the Zr particles and the base metal pure Al.

(Comparative example)
A pure Al sample, which is a comparative material produced by centrifugal casting, was produced under the same conditions as the Al-based composite material produced in the manufacturing process.

The crystal grain sizes of the Al-based composite material and pure Al were measured, and a micro Vickers hardness test was further performed. The crystal grain size was measured at 1 mm from the outer periphery toward the inner periphery. The crystal grain size was 2.7 mm for pure Al and 99 μm for Al-based composite material. From this result, it can be seen that the crystal grains of the base material Al in the Al-based composite material are much finer than the crystal grains of the pure Al sample of the comparative sample. It can be presumed that the reason why the crystal grains of the Al-based composite material became fine is that the intermetallic compound Al ₃ Zr worked as a heterogeneous nucleus. Moreover, the evaluation result of a micro Vickers hardness test is shown in FIG. In the micro Vickers hardness test, in the Al-based composite material, Vickers indentation was applied to a portion of the base material pure Al where Zr and the intermetallic compound Al ₃ Zr were not present. In addition, the cross-sectional thickness was standardized from the inner periphery toward the outer periphery, and measurement was performed. From this figure, the hardness of the Al-based composite material is larger than that of the pure Al sample at the normalized position 0.7 to 1.0 (outer peripheral side) where the mixed powder containing Zr was present at the time of casting. Recognize. From the results of the crystal grain size and FIG. 7, it can be seen that the smaller the crystal grain size, the higher the micro Vickers hardness of the base material, that is, the higher the material strength. From the above results, it can be seen that the Al-based composite material obtained by the present invention has higher strength than the pure Al sample.

(Example 2: Dissolution of Al powder with molten Al)
65.9 g of pure Al powder having a particle diameter of 100 to 150 μm as a base metal powder is put into a cylindrical mold having a cavity with a diameter of 80 mm and a width of 50 mm. Further, 280 g of pure Al ingot is loaded into a melting furnace for casting. Thereafter, the mold is heated to 600 ° C. in vacuum and the pure Al ingot is heated to a melting temperature of 800 ° C. to obtain a base material molten pure Al. Then, the cylindrical mold is rotated and a centrifugal force of gravity multiple 1119G (gravity multiple 1G corresponds to a gravitational field) is applied to the pure Al powder to fix the cylindrical mold to the inner wall of the cylindrical mold, Molten pure Al was poured. At this time, the pure Al powder is heated to the melting point, and at the same time, heat is removed from the portion where the powder was present due to latent heat at the time of melting, and the cooling rate at the time of solidification is increased. Through this manufacturing process, a composite material was produced in which the pure Al crystal grains in the portion where the powder was present were refined. FIG. 8 is a photograph after corrosion of the cross section of the composite material. It can be seen that centrifugal force is applied in the direction of the arrow, and the crystal grains on the outer peripheral side are fine.

The crystal grain size and micro Vickers hardness test of an Al sample, which is a comparative material produced by centrifugal casting under the same conditions as the composite material produced in the manufacturing process, were performed. The crystal grain size was measured at 1 mm from the outer peripheral part toward the inner peripheral part as described above. When there was no Al powder, it was 2.7 mm, and when there was Al powder, it was 129 μm. From this result, it can be seen that the material produced by pouring pure Al powder into a cylindrical mold and then pouring the base material molten pure Al into the mold has a crystal grain size finer than that of the comparative sample. Moreover, the result of a micro Vickers hardness test is shown in FIG. Also in the same manner as in Example 1, the thickness of the cross section was measured by standardizing the position from the inner peripheral portion toward the outer peripheral portion. From this figure, it can be seen that the micro Vickers hardness of the Al composite material is large at the normalized position 0.7 to 1.0 where the powder was present at the time of casting. From the above results, it can be seen that the Al composite material produced by the present technology has finer crystal grains and higher strength than an ordinary centrifugal cast product.

The present invention aims to improve the strength of pipes and the like manufactured by centrifugal casting, and when a bearing or the like is produced using the present invention, the wear resistance and durability of the bearing are expected to be improved.

Claims (7)

A composite material in which a compound serving as a heterogeneous nucleus is dispersed in a base metal, wherein the base metal has crystal grains of 300 μm or less. The composite material according to claim 1, wherein a crystal grain size of the base metal is 100 μm or less. The composite material according to claim 1 or 2, wherein the size of the crystal grains of the base metal changes in an inclined manner in the composite material. The composite material according to claim 1, wherein the base metal is Al and the compound is Al ₃ Zr. The base metal powder is put into a mold, the molten base metal is poured while rotating the mold to give a centrifugal force to the powder, and the base metal is heated by the heat of the base metal molten metal. A method for producing a composite material in which metal powder is melted, crystal grains are made finer, and strength is higher than that of a base metal by centrifugal casting. The method for producing a composite material according to claim 5, wherein the powder charged into the mold is a mixed powder of the base metal powder and a powder that generates a compound having good consistency with the base material. The method for producing a composite material according to claim 6, wherein the base metal is Al, and the powder that forms a compound with the base material is Zr.