JP4119357B2 - Method for producing high thermal conductivity metal matrix composite - Google Patents

Description

The present invention relates to a method for producing a highly thermally conductive metal matrix composite member.

  Conventionally, a particle-dispersed metal matrix composite member and a fiber-dispersed metal matrix composite member are known as this type of member. In the former case, there is an advantage that the directionality of the thermal conductivity is small, but on the other hand, a plurality of particles having high thermal conductivity are dispersed in a matrix having lower thermal conductivity than those particles. In addition, since heat needs to flow through the matrix having a low thermal conductivity and be transmitted through the interface between the particles and the matrix, there is a problem that the degree of improvement in the thermal conductivity of the entire member is low. On the other hand, in the latter case, although the thermal conductivity in the fiber orientation direction is high, there is an anisotropy that the thermal conductivity other than the orientation direction is low. Such anisotropy can be reduced by making the fiber orientation random, but the amount of fibers oriented in the direction of heat flow decreases, so the degree of improvement in thermal conductivity of the entire member is low. There was a problem.

By the way, with the aim of improving wear resistance, a metal matrix composite member has been developed that includes a ceramic molded body having a three-dimensional network structure and a metal matrix filled in the ceramic molded body (for example, Patent Document 1). reference). Therefore, if a ceramic molded body is molded using a material having high thermal conductivity and a heat transfer path with high thermal conductivity is stretched around the entire member, the heat flow in the entire member is improved, and the thermal conductivity is related. We can expect relaxation of directionality.
JP-A-6-170514

  However, in the conventional ceramic molded body, the size of the cells and the distribution state of the cells are not uniform, so that the partial heat flow differs greatly inside the metal matrix composite member, and the degree of improvement in thermal conductivity of the entire member There was a risk of causing a problem of low.

The present invention provides a method for manufacturing a metal matrix composite member having a high thermal conductivity over the entire member by improving the structure of the ceramic molded body to make the partial heat flow uniform. Objective.

According to the present invention for achieving the above object, a ceramic molded body having a three-dimensional network structure is composed of SiC or AlN, Ri Na more metal matrix filled Al alloy or Mg alloy into the ceramic body the ceramic molded body is manufactured of a plurality of the spherical cells, phase Tonariru high thermal conductivity metal matrix composite formed by a plurality of communication holes existing in the partition wall between the two spherical cells be arranged in close-packed format A method,
A ceramic molded body manufacturing process for manufacturing the ceramic molded body of a predetermined shape, and a process of placing the manufactured ceramic molded body in a cavity of a mold and pressurizing and filling the molten metal matrix into the cavity; The ceramic molded body manufacturing step comprises covering the surface with the ceramic particles by closely attaching a plurality of ceramic particles having a smaller diameter than the spherical synthetic resin particles to the surface of the spherical synthetic resin particles having a predetermined diameter. A first step of obtaining an aggregate of coated particles, a second step of placing the aggregate of coated particles in a mold and performing a close-packing treatment, and injecting a ceramic slurry containing ceramics into the mold. A third step of obtaining a shaped product comprising the ceramic and the aggregate of the coated particles by filling the gap between the aggregates of the coated particles and drying; After releasing the product, a fourth step of thermally decomposing each synthetic resin particle in the shaped article by installing and heating in the sintering furnace, and after the pyrolysis, the sintering furnace And a fifth step of sintering the ceramic particles and the ceramic in the shaped article . A method for producing a highly heat-conductive metal matrix composite member is provided.

  When configured as described above, the size of the spherical cells in the ceramic molded body and the uniformity of the distribution state thereof can be improved, and the heat transfer path with high thermal conductivity can be stretched in a well-balanced manner throughout the member, thereby A metal matrix composite having high thermal conductivity at a low volume fraction Vf can be provided.

  1 and 2, a highly thermally conductive metal matrix composite member 1 having a short columnar shape includes a ceramic molded body 2 having a three-dimensional network structure and a metal matrix 3 filled in the ceramic molded body 2. 3 and 4, the ceramic molded body 2 has a rectangular parallelepiped shape, and includes a plurality of spherical cells 4 arranged in a close-packed form, and a plurality of communication holes 6 existing in the partition walls 5 between the adjacent spherical cells 4. Have.

The median Md of the inner diameter of the communication hole 6 is set to Md ≧ 1 μm so as to allow pressure filling of the molten metal constituting the metal matrix 3. Further, the ratio Md / M _D of the median M _D of the inner diameter of the spherical cell 4 and the median Md of the inner diameter of the communication hole 6 is set to Md / M _D <0.5 from the heat flow inside the ceramic molded body 2. However, when the ratio Md / M _D ≧ 0.5, the amount of the partition walls 5 is reduced, so that the thermal conductivity of the entire member 1 is lowered. The median M _D of the inner diameter of the spherical cells 4 3D CT analysis, also the median Md of the inner diameter of the communication hole 6 is determined respectively by mercury porosimetry.

As a constituent material of the metal matrix 2, A l alloy or Mg alloy is used. Examples of the material of the ceramic molded body 2, SiC or Al N having a high thermal conductivity is used. In this case, the relationship between Kc> Km between the thermal conductivity of Km of thermal conductivity Kc and the metal matrix 3 of the ceramic molded body 2 you satisfied.

  Table 1 shows the thermal conductivities Km and Kc regarding the constituent materials of the metal matrix 3 and the ceramic molded body 2.

  In manufacturing the ceramic molded body 2, as shown in FIG. 5, the following processes are used.

  (A) Step: An aggregate of spherical synthetic resin particles 7 having a predetermined median diameter and ceramic particles 8 having a smaller diameter than the synthetic resin particles 7 and having a predetermined median diameter to form the spherical cell 4 Prepare an aggregate.

  Step (b): Both aggregates are put into a coating processor to obtain an aggregate of coated particles 9 in which ceramic particles 8 are closely adhered to the surface of the synthetic resin particles 7.

  (C) Process: Putting the aggregate | assembly of the covering particle | grains 9 into a type | mold, and performing a close packing process.

  (D) Step: For example, a ceramic slurry containing ceramics of the same material as the ceramic particles 8 is injected into the mold and filled in the gaps of the aggregate.

  (E) Step: After drying the ceramic slurry, the shaped article 11 composed of the ceramic 10 and the aggregate of the coated particles 9 is released.

  (F) Step: The shaped article 11 is placed in a sintering furnace of a predetermined atmosphere, and heating that can thermally decompose the synthetic resin particles 7 in the furnace at a predetermined heating rate under a predetermined furnace pressure. The temperature is raised and the heating temperature is maintained for a predetermined time. As a result, the synthetic resin particles 7 are thermally decomposed to form the spherical cells 4 and are thermally decomposed into the partition wall forming portion 5a formed of the plurality of ceramic particles 8 and the ceramics 10 between the adjacent spherical cells 4. A plurality of communication holes 6 are formed by the pressure at which the gas escapes.

  (G) Process: The inside of the furnace is raised to a temperature at which the ceramic particles 8 can be sintered, and the sintering temperature is maintained for a predetermined time. Thereby, the ceramic molded body 2 having a three-dimensional network structure is obtained.

In the manufacturing method, the inner diameter of the spherical cells 4 and the uniformization thereof depend on the median diameter of the synthetic resin particles 7, and the uniform distribution of the spherical cells 4 is performed by the closest packing process in the step (c). Achieved by: Further, the inner diameter of the communication hole 6 is controlled by the atmosphere in the furnace, the heating rate, the furnace pressure, the viscosity of the ceramic slurry (concentration of the ceramic 10) and the like in the step (f). For example, by setting the median diameter of the synthetic resin particles 7 to a predetermined value and controlling the temperature increase rate, the ratio Md / M _D of both medians Md and M _D falls within Md / M _D <0.5. be able to.

  Hereinafter, specific examples will be described.

[I] Production of Ceramic Molded Body The steps (a) to (g) were performed under the conditions described below to obtain a rectangular parallelepiped ceramic molded body having a length of 20 mm, a width of 20 mm, and a length of 200 mm.

(A) Process: Aggregation of spherical synthetic resin particles: Aggregation of PMMA particles having a median diameter of 90 μm (trade name MR-90G, manufactured by Soken Chemical Co., Ltd.); Aggregation of ceramic particles: SiC having a median diameter of 0.5 μm Particle aggregate (manufactured by Yakushima Electric Works, trade name OY-20).
(B) Process: Blending weight ratio of the aggregate of synthetic resin particles (W ₁ ) and the aggregate of ceramic particles (W ₂ ): W ₁ / W ₂ = 1/1; Coating processor: manufactured by Hosokawa Micron Name AM-15F (see JP 2003-160330 A), rotational speed 1000 rpm, processing time 0.5 h, inner piece distance 1 mm.
(C) Process: Mold size and structure: Two PTFE blocks having recesses of 20 mm in length, 20 mm in width, and 100 mm in depth are arranged to face each other and have a cavity of 20 mm in length, 20 mm in width, and 200 mm in length Close-packing treatment by vacuum filtration: A glass fiber filter medium having a 0.7 μm communication hole is laid on the bottom surface of one block having a plurality of suction holes, and then inside the cavity from the opening of the other block Then, the coated particles were put in, and then the inside of the cavity was depressurized through the suction hole of one block.

(D) Step: Ceramic slurry: SiC slurry (e) Step: Primary drying treatment: 20 ° C., 20 h; Secondary drying treatment: 90 ° C., 1 h.
(F) Process: furnace atmosphere: air; furnace pressure: 0.1 MPa; heating rate: 10 ° C./h; heating temperature: 500 ° C., 1 h.
(G) Step: Sintering temperature: 2000 ° C .; Sintering time: 3 h.
The ceramic molded body 2 thus obtained has a three-dimensional network structure, and a plurality of spherical cells 4 are arranged in a close-packed form, and the median M _D of the inner diameter is M _D = 80 μm. and the median Md of the inner diameter of the communication hole 6 is Md = 16 [mu] m, thus the ratio Md / M _D of both median Md, M _D was Md / M _D = 0.2.

[II] Manufacture of metal matrix composite member The ceramic molded body 2 was placed in the cavity of the mold, and then a molten metal of 680 ° C. Al alloy (JIS ADC12) was used, injection speed 0.2 m / s, casting pressure 75 MPa The metal matrix composite member 1 having a length of 20 mm, a width of 30 mm, a length of 40 mm, and a volume fraction Vf of the ceramic molded body 2 of Vf = 30% was obtained by performing a low-speed laminar flow die casting method. This member 1 was taken as an example.

For comparison, a metal matrix composite member was produced in the same manner as described above using a foamed ceramic molded body manufactured by MMI having the same material and the same dimensions as the ceramic molded body. Further, a metal matrix composite member in which SiC particles having a median particle size of 15 μm were uniformly dispersed was produced, and this was designated as Comparative Example 2. A further median M _D is M _D = 100 [mu] m inner diameter of spherical cells, also the median Md of the inner diameter of the communication hole a Md = 50 [mu] m, both median Md, the ratio Md / M _D is Md / M _D of M _D A metal matrix composite member similar to the example except that = 0.5 was produced, and this was designated as Comparative Example 3.

  Test specimens having a diameter of 10 mm and a thickness of 2 mm were prepared from Examples and Comparative Examples 1 to 3, and these were subjected to heat conduction using a laser flash method thermal conductivity measuring device (manufactured by ULVAC-RIKO, model TC-7000). The rate was measured.

  Table 2 shows various data relating to Examples and Comparative Examples 1 to 3.

From Table 2, the examples show that the high heat transfer material is connected in a mesh shape (with continuity), has isotropic heat conduction, and the distribution of spherical cells is uniform, and in addition, the median Md Since it is ≧ 1 μm and Md / M _D is Md / M _D <0.5, it can be seen that it has high thermal conductivity. Although Comparative Example 1 has the continuity, since the size of the spherical cells is non-uniform, the isotropy is moderate and the distribution of the spherical cells is also non-uniform. Is low. Furthermore, although the comparative example 2 has the isotropy about heat conduction and the uniformity of the high heat transfer material, it does not have the continuity, so the heat conductivity is lower than that of the example.

  FIG. 6 shows the relationship between the inner diameter of the spherical cell by the template method and the existence probability regarding the example and the comparative example 1. In the examples, the variation range of the inner diameter of the spherical cell is 30 to 110 μm, while that of Comparative Example 1 is as wide as 40 to 340 μm. Therefore, it can be seen that the uniformity of the inner diameter of the spherical cell is higher in the example than in the comparative example 1.

  As the high thermal conductivity metal matrix composite, one or more parts selected from the cylinder bore, cylinder head gasket surface, etc. in the engine cylinder block are reinforced. In the cylinder head, around the combustion chamber, valve seat press-fitting part, valve Strengthened at one or more locations selected from guide press-fitting parts, etc., piston strengthened at one or more locations selected from the top, ring groove, etc., various devices require strength and cooling There are parts that have a part and strengthen it.

It is a perspective view of a metal matrix composite member. It is a principal part expanded sectional view of a metal matrix composite member. It is a perspective view of a ceramic molded body. It is a principal part expanded sectional view of a ceramic molded object. It is manufacturing process explanatory drawing of a ceramic molded body. It is a graph which shows the relationship between the internal diameter of a spherical cell, and its existence probability.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Metal matrix composite member 2 ... Ceramic compact 3 ... Metal matrix 4 ... Spherical cell 5 ... Partition 6 ... Communication hole
7 ... Spherical synthetic resin particles
8. Ceramic particles
9 …… Coated particles
10 Ceramics
11 ... Shaped items

Claims (1)

Ceramic molded body having a three-dimensional network structure is composed of SiC or AlN and (2), the ceramic molded body (2) a metal matrix (3) of the filled Al alloy or Mg alloy into the Ri more greens, the ceramic The molded body (2) has a plurality of spherical cells (4) arranged in a close-packed form and a plurality of communication holes (6) in the partition wall (5) between the adjacent spherical cells (4). A method for producing a high thermal conductivity metal matrix composite member,
A ceramic molded body manufacturing process for manufacturing the ceramic molded body (2) having a predetermined shape, and the manufactured ceramic molded body (2) is placed in a cavity of a mold, and the metal matrix (3) is placed in the cavity. And a step of pressurizing and filling the molten metal,
The ceramic molded body producing step includes the step of closely attaching a plurality of ceramic particles (8) having a smaller diameter than the spherical synthetic resin particles (7) to the surface of the spherical synthetic resin particles (7) having a predetermined diameter. A first step of obtaining an aggregate of coated particles (9) formed by covering the ceramic particles with the ceramic particles (8), and a second step in which the aggregate of the coated particles (9) is put in a mold and subjected to a close-packing treatment. A ceramic slurry containing ceramics (10) is injected into the mold and filled in the gaps of the aggregates of the coated particles (9), and dried, whereby the ceramics (10) and the coated particles (9) A third step of obtaining a shaped article (11) comprising the aggregate of the above, and after releasing the shaped article (11), the shaped article (11) is placed in a sintering furnace and heated to obtain the shaped article. A fourth step of thermally decomposing each synthetic resin particle (7) in (11); After serial pyrolysis, in the sintering furnace, characterized in that it comprises a fifth step of the sintered ceramic particles (8) and the ceramic (10) in the attached form product (11) The manufacturing method of a highly heat conductive metal matrix composite member.

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