RU2625377C1 - Method of manufacturing composite material for microwave electronics - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes sealing a split compression mould by slip casting a mixture of fractions 1÷15 mcm and 35÷50 mcm of silicon carbide of hexagonal structure of 6H syngony with a binder in the form of sodium liquid glass and paraffin at a temperature of 70÷75°C and pressure 0.5÷1.0 MPa, extraction of the workpiece from the compression mould, workpiece sintering at a temperature of more than 750°C, impregnation of the workpiece with an aluminium alloy melt with a silicon content of 6÷12% in a heated mould at a temperature of 890-900°C, a pressure of 80-100 MPa for 30-50 s and crystallization by creating a temperature gradient.

EFFECT: increased specific density, heat conductivity and strength of composite material.

1 tbl, 6 ex

Description

The invention relates to powder metallurgy, and in particular to the manufacture of composite material for microwave electronic products.

The modern development of microwave electronics, primarily solid-state microwave electronics, requires the creation of new materials for the manufacture of products (product elements, components, assemblies) of microwave electronics with a wide range of physical properties.

A feature and advantage of a composite material is multicomponent. It is this combination of physical properties of many components that leads to the creation of a new material, the physical properties of which differ from the physical properties of each of its constituent components.

Many composite materials are superior to traditional materials and alloys in their physical properties.

,A known method of producing a composite material based on an aluminum matrix (Al) with inclusions of silicon carbide (SiC), comprising melting an aluminum-silicon alloy and treating the molten bath with carbon dioxide, in which, in order to simplify the process, increase productivity and reduce costs, expand functionality , the relative consumption of K _Q carbon dioxide is selected from the interval K _Q = 0.005 ... 0.05, while

,

where M _G is the mass of gas consumed during the processing of the melt, M _M is the mass of processed metal [RF Patent No. 2348719, IPC C22C 1/10, C22C 21/00, priority date 20.11 2006, publ. 03/10/2009].

This method is quite complicated and practically not suitable for solving problems of microwave electronics.

Known composite material based on aluminum alloy and method for its production.

The composite material contains reinforcing discrete ceramic particles and precipitation of strengthening phases during precipitation hardening of the alloy, which, in order to increase contact durability, additionally contains intermetallic phases of composition Al ₃ X, where X is Ti, Zr, V, Hf with a phase size of ≅20 μm in the following the content of hardeners, vol. %: inclusions of intermetallic phases N = 5 ÷ 15, discrete ceramic particles - (30 ÷ N), precipitation of hardening phases during dispersion hardening 7 ÷ 10, while the average size of discrete ceramic particles does not exceed 28 microns. As discrete ceramic hardeners, it contains particles of TiC, ZrC, B ₄ C, SiC, Al ₂ O ₃ , ZrO ₂ , BN, TiN.

The method for its preparation consists in mechanical mixing of discrete ceramic particles into an aluminum melt and dispersion hardening of the alloy.

In which, for the above purpose, after kneading, the melt is additionally alloyed with the addition of a composite ligature containing elements forming intermetallic phases Al ₃ X, where X is Ti, Zr, V, Hf, then the melt is mixed, liquid stamping and subsequent dispersion hardening of the alloy are carried out [ RF patent №2136774, IPC С22С 1/10, С22С 21/00, priority date November 20, 2006, publ. 03/10/2009].

In this way, like the method of the first analogue, it is technically difficult to solve the problems of microwave electronics.

A known method of obtaining a highly filled composite material Al-SiC, which consists in preparing a preform (workpiece) by mixing reinforcing powders of silicon carbide of various size fractions, placing it in a mold and subsequent vibration compaction. Then the finished preform is impregnated under pressure with a matrix melt and the resulting composite material is cooled. Inside the working space of the press, it is possible to place a plurality of separation elements forming cavities corresponding to the shape of the product [US Patent No. 5941297, IPC B22D 18/00, class. 164/62, priority date 09/23/1996, publ. 02.1976].

The use of two size fractions of SiC powder (50 and 100 μm) allows to reduce the porosity of the preform, since the finer powder fills the gaps between the particles of the larger powder. This method allows to obtain a filler content in the composite material of more than 60 percent.

The disadvantage of this method is the impossibility of obtaining the finished product of complex shape, since the machining of the obtained composite material is practically impossible because of its high hardness and strength, and at the preliminary stage of obtaining the preform from silicon carbide powder, you can only give it a fairly simple shape to avoid the possibility of violation its mechanical integrity.

A known method of manufacturing a product from a composite material with a metal matrix, comprising preparing a workpiece by mixing a reinforcing ceramic powder of silicon carbide of various size fractions, placing the resulting mixture in a mold and its vibration compaction, impregnating the workpiece with a molten matrix under pressure and subsequent crystallization.

In which, in order to obtain a highly filled composite material with a metal matrix and a filler in the form of dispersed ceramic particles and a product from it having a high density, high thermal conductivity and low temperature coefficient of linear expansion (TEC) with high yield and the possibility of obtaining products of complex shape, in the reinforcing ceramic powder of silicon carbide, boron carbide powder is additionally added in an amount of 1 ÷ 50 vol.%, after vibration compaction, the workpiece is subjected to an additional air dissolution with isothermal exposure, and crystallization is carried out directionally by creating a temperature gradient at the crystallization front [RF Patent No. 2261780, IPC C22C 1/10, C22C 21/00, priority 25.02.2004, publ. 10/10/2005] - a prototype.

However, the achieved results of the composite material of the product in terms of specific density, thermal conductivity, and the consistency of its temperature coefficient of linear expansion with the temperature coefficients of linear expansion of other specified structural materials in a certain range are not sufficient for microwave electronic products.

The technical result of the invention is to increase the specific density, thermal conductivity and strength of the composite material, providing a temperature coefficient of linear expansion of the latter, consistent with the temperature coefficients of linear expansion of other specified structural materials of microwave electronic equipment, not more than 8 × 10 ^-6 K ^-1 .

The specified technical result is achieved by the claimed method of manufacturing a composite material for microwave electronic devices based on a metal matrix — an aluminum alloy and a non-metallic filler — silicon carbide of various size fractions, including

- preparing a workpiece of a given size from silicon carbide of various size fractions by mixing various size fractions of silicon carbide, placing this mixture in a given mold, sealing the mixture of the workpiece,

- impregnation of the preform with molten aluminum alloy under pressure and crystallization by creating a temperature gradient,

wherein

aluminum alloy is taken with the content of the alloying element - silicon 6 ÷ 12 percent,

silicon carbide is taken from the hexagonal structure of 6H syngony, with two size fractions: the first 1 ÷ 15 μm, the second 35 ÷ 50 μm, with the content of impurities in each of them - other silicon carbide syngoniums not more than 20 percent,

a given mold is made detachable,

during preparation of the preform, the aforementioned size fractions of silicon carbide are mixed at their ratio, in parts by weight, 1: 5, the binder components are added additionally and sequentially to this mixture - sodium liquid glass and paraffin at their ratio, parts by weight, 0.004 ÷ 0.006 and 0.2 ÷ 0.22 of the total ratio of size fractions of silicon carbide, respectively,

the mixture is heated at a temperature of 70 ÷ 75 ° C,

and compaction of the workpiece mixture is carried out by slip casting under a pressure of 0.5 ÷ 1.0 MPa into said predetermined mold,

then remove the workpiece from a given mold and sinter the workpiece at a temperature of 750 ÷ 800 ° C,

and the aforementioned impregnation of the preform with molten aluminum alloy under pressure is carried out at a temperature of 890 ÷ 900 ° C, a pressure of 80 ÷ 100 MPa for 30 ÷ 50 s in another mold made of heat-resistant material, a proportional preform, detachable, the latter being heated during the impregnation up to a temperature of 640 ÷ 650 ° C.

Disclosure of the invention.

Aluminum alloy with the content of the alloying element - silicon 6 ÷ 12 percent:

firstly, it ensures its optimum fluidity and, as a consequence, a high specific gravity of the composite material;

secondly, it eliminates the possibility of the formation of an undesirable phase of aluminum carbide, namely Al ₄ C ₃ , which can lead to mechanical destruction of the composite material.

Silicon carbide:

- the hexagonal structure of syngony 6H is one of the modifications of α-SiC, which has maximum thermal conductivity;

- with two size fractions: the first 1 ÷ 15 microns, the second 35 ÷ 50 microns, which optimally provide the specified filling of the composite material with silicon carbide;

- with the content in each of them of impurities - other syngonium silicon carbide not more than 20 percent.

And, as a consequence of this, a significant increase in the thermal conductivity of the composite material.

The manufacture of molds (preset and different) detachable ensures the preservation of the composite material billet during extraction after technological operations as slip casting and impregnation of the billet with molten aluminum alloy under pressure.

The manufacture of another mold from heat-resistant material provides mechanical preservation of the mold and, thereby, the implementation of high technological operations of impregnation of the workpiece with molten aluminum alloy under pressure.

Preparation of the workpiece through other technological operations and other technological modes relative to the prototype, namely when:

said size fractions of silicon carbide are mixed at their ratio, in parts by weight, 1: 5,

the binder components — sodium liquid glass and paraffin — are added to this mixture additionally and sequentially with their ratio, parts by weight, 0.004–0.006, and 0.2–0.22 of the total ratio of size fractions of silicon carbide, respectively,

the mixture is heated at a temperature of 70 ÷ 75 ° C,

compaction of the workpiece mixture is carried out by slip casting under a pressure of 0.5 ÷ 1.0 MPa into said predetermined mold,

remove the workpiece from a given mold and sinter the workpiece at a temperature of 750 ÷ 800 ° C.

This together provides:

firstly, increasing the thermal conductivity of the composite material;

secondly, the temperature coefficient of linear expansion of the composite material is consistent with the temperature coefficients of linear expansion of other specified structural materials of the elements of microwave electronic equipment not more than 8 × 10 ^-6 K ^-1 .

In this case, the first and second, due to the burning out of the binder component - paraffin in the process of impregnating the preform with aluminum melt, and thereby - increasing its open porosity.

Thirdly, an increase in the strength of the composite material, due to the adhesion of dimensional fractions of silicon carbide to the binder component - sodium liquid glass.

Fourth, the optimum allowable fluidity of the slurry of the workpiece, due to the heating of the mixture at a temperature of 70 ÷ 75 ° C and thereby - the possibility of the slip casting itself;

Fifthly, the optimum possible full filling of the blank with a slip of a given mold and thereby correspondingly obtaining the most accurate specified dimensions and shapes of the product from composite material.

The implementation of the workpiece impregnation with a molten aluminum alloy under pressure at other technological conditions (temperature 890 ÷ 900 ° C, pressure 80 ÷ 100 MPa for 30 ÷ 50 s, rather than in the prototype, is optimal to ensure:

firstly, the optimal viscosity of the melt of the workpiece and thereby

a) the possibility of carrying out the technological operation of impregnation of the workpiece,

b) elimination of the possibility of the formation of non-impregnated pores in the composite material and, as a result, an increase in the specific gravity of the composite material;

secondly, eliminating the likelihood of the formation of an undesirable phase of aluminum carbide (Al ₄ C ₃ ), which can lead to the destruction of the composite material of the product and, as a result, increase the strength of the composite material.

In this case, heating of another mold during the impregnation process in addition to the above provides:

firstly, the optimal stability of the necessary-sufficient viscosity of the molten aluminum alloy and thereby:

a) the possibility of stable and reliable implementation of the process of impregnation of the workpiece,

b) the exclusion of the possibility of the formation of impregnated pores in the composite material and, as a consequence, an increase in the specific gravity of the composite material;

secondly, the stability of the directed crystallization front in the process of impregnation of the workpiece and, as a result, an increase in the thermal conductivity of the composite material.

So, the set of essential features of the claimed method of manufacturing a composite material for microwave electronic products fully provides the specified technical result, namely, increasing the specific gravity, thermal conductivity and strength of the composite material, providing a temperature coefficient of linear expansion of the latter, consistent with the temperature coefficients of linear expansion of other specified construction materials of microwave electronics no more than 8 × 10 ^-6 K ^-1 .

An aluminum alloy with an alloying element - silicon content of less than 6 and more than 12 percent is not acceptable:

In the first case:

a) does not provide an increase in its specific gravity and, accordingly, the specific gravity of the composite material,

b) due to the likelihood of the formation of an undesirable phase of aluminum carbide (Al ₄ C ₃ ) which can lead to the destruction of the composite material,

secondly, due to a significant decrease in the thermal conductivity of the composite material.

Size fractions of silicon carbide:

- smaller: both the first 1 μm, the second 35 μm, and more than the first 15 μm, the second 50 μm are undesirable, in the first case due to a decrease in thermal conductivity, in the second - due to the complexity of subsequent technological operations with the product made of composite material (processing, plating);

- with the content of impurities in each of them - other syngonies of silicon carbide more than 20 percent is not permissible due to a decrease in the thermal conductivity of the composite material.

Technological modes during the preparation of the workpiece, namely:

- mixing dimensional fractions of silicon carbide with a different ratio in weight. hours (than 1: 5) is not desirable, since it does not provide the necessary thermal conductivity of the composite material, and the temperature coefficient of linear expansion of the latter, consistent with the temperature coefficients of the linear expansion of other specified structural materials of microwave equipment, is not more than 8 × 10 ^-6 K ^{- 1} ;

- the introduction of the components of the binder in their ratio, parts by weight,

less than 0.004 (sodium liquid glass) and 0.2 (paraffin), and more than 0.006 (sodium liquid glass) and 0.22 (paraffin) of the total ratio of size fractions of silicon carbide in parts by weight (1: 5) is not desirable: in the first case, due to a decrease in the strength of the workpiece, in the second, due to an increase in the porosity of the workpiece and, accordingly, a decrease in thermal conductivity and an unacceptable mismatch of the above-mentioned TECs;

- heating the workpiece mixture (two dimensional fractions of silicon carbide and binder components) at a temperature below 70 ° C is not permissible, due to the insufficient fluidity of the slurry of the workpiece and, accordingly, the impossibility of providing a slip casting process, and more than 75 ° C is inappropriate;

- compaction of the workpiece by slip casting under a pressure of less than 0.5 MPa is not desirable due to a decrease in the quality of filling a given mold and, accordingly, deviations from a given size and shape of a product, and more than 1 MPa is not practical;

- sintering at a temperature below 750 ° C is not permissible, due to a decrease in the strength of the composite material, above 800 ° C, it is advisable.

Impregnation of a billet with an aluminum alloy melt at technological parameters, both less than a temperature of 890 ° C, a pressure of 80 MPa, for 30 sec, and more than a temperature of 900 ° C, a pressure of 100 MPa, for 50 sec is not permissible, in the first case - due to insufficient melt flow, in the second - due to the likelihood of the formation of an undesirable phase of aluminum carbide (Al ₄ C ₃ ), which can lead to the destruction of the composite material.

Heating another mold to a temperature of less than 640 ° C and more than 650 ° C is not permissible:

in the first case, due to a critical decrease in the viscosity of the melt and the formation of impregnated pores in the composite material,

in the second, due to a possible violation of the directed crystallization front during the impregnation of the workpiece and, accordingly, a decrease in the thermal conductivity of the composite material.

Examples of specific performance of the claimed method of manufacturing a composite material for microwave electronics products, for example, heat-releasing components from the claimed composite material of submodules containing components from low-temperature co-fired ceramics (SCM 18 linear expansion temperature coefficient of 5.8 ÷ 7.2 × 10 ^-6 K ^-1 ), active phased array antenna systems (AFAR).

Example 1

Ask:

the size of the workpiece (41 × 17 × 3.2) × 10 ^-3 m and, accordingly, the size of a given mold, taking into account the allowable allowance.

Take the source materials (components):

- a metal matrix - an aluminum alloy with a dopant - silicon content of 9 percent GOST 1583-93,

- non-metallic filler - silicon carbide hexagonal structure of syngony 6H with two size fractions: the first is 8 microns and the second is 42.5 microns GOST 3547-80, with impurities in each of them - other syngonium silicon carbide 10 percent,

- the components of the binder - sodium liquid glass GOST 13078-81 and T-1 paraffin GOST 23683-89.

Make:

- a given mold made of steel (St3 GOST 3 80-94), detachable;

- another mold made of heat-resistant material (4X5MFS steel stamped), a commensurate workpiece, demountable, both molds using any known method, for example, milling.

Prepare a blank of silicon carbide with:

- pre-mixed the above-mentioned size fractions of silicon carbide at their ratio, in parts by weight, 1: 5 in an EIRJCH Laboratory mixer (type EL-1),

- the components of the binder, parts by weight, are sequentially introduced into this mixture, - sodium liquid glass - 0.030 × (0.005 × 6) and paraffin 1.26 × (0.21 × 6) (determined according to their indicated ratios, parts by weight , from the total ratio of size fractions of silicon carbide (equal to 6), respectively),

- heat this mixture at a temperature of 72.5 ° C,

- carry out the compaction of the workpiece mixture by slip casting under a pressure of 0.75 MPa at the installation of casting slip ULSH-3 in the manufactured specified mold,

- further, the preform is removed from the given mold and the preform is sintered at a temperature of 775 ° C (muffle furnace KS 600/25),

The workpiece is impregnated with molten aluminum alloy under pressure (press IP-2500M-auto) at a temperature of 895 ° C, a pressure of 90 MPa, for 40 s, in another mold a proportional workpiece, while in the process of impregnation the mold is heated to a temperature 645 ° C.

Examples 2-6

Analogously to example 1, samples of the composite material were made for the heat sink component, but under other technological conditions, both indicated in the claims (examples 2-3) and beyond (examples 4-5).

Example 6 corresponds to the prototype method.

On the manufactured samples of the composite material for heat sink components, the following are determined:

- thermal conductivity, W / m × K, using a laser flash method (Linseis XFA500 installation);

- specific gravity, kg / m ³ , by hydrostatic weighing (SHIMADZU UW620, SMK-101);

-bending strength, MPa (explosive machine, model 2001 R-0.5)

- temperature coefficient of linear expansion, 10 ^-6 K ^-1 (dilatometer DIL 402 C).

The data are presented in the table.

As can be seen from the table,

samples of the composite material for the heat sink component manufactured according to the claimed method have:

- thermal conductivity 180 ÷ 240 W / m × K,

- specific gravity 3020 ÷ 3080 kg / m ³ ,

- bending strength 405 ÷ 442 MPa,

- temperature coefficient of linear expansion of 7.5 ÷ 7.9 × 10 ^-6 K ^-1 (examples 1-3);

in contrast to samples of composite material made outside the limits claimed in the method, have:

- thermal conductivity 170 ÷ 190 W / m × K,

- specific gravity 2800 ÷ 3060 kg / m ³ ,

- bending strength 370 ÷ 420 MPa,

- temperature coefficient of linear expansion of 6.8 ÷ 8.3 × 10 ^-6 K ^-1 (examples 4-5).

The prototype method has:

- thermal conductivity 193 W / m × K,

- specific gravity 3050 kg / m ³ ,

- strength - no data,

- the temperature coefficient of linear expansion of 8.4 × 10 ^-6 K ^-1 (example 6).

Thus, the claimed method of manufacturing a composite material for products of electronic microwave technology will provide in comparison with the prototype:

- increase in specific gravity by about 1 percent,

- increase in thermal conductivity by about 25 percent,

- the temperature coefficient of linear expansion of the claimed composite material is 7.5 ÷ 7.9 × 10 ^-6 K ^-1 , consistent with the temperature coefficients of linear expansion of other specified structural materials of microwave technology not more than 8 × 10 ^-6 K ^-1 , for example, with temperature the coefficient of linear expansion of the low-temperature co-fired ceramic SCM 18 (5.8 ÷ 7.2 × 10 ^-6 K ^-1 ).

The bending strength of the composite material is 405 ÷ 440 MPa.

A composite material with the indicated technical characteristics is relevant and promising for microwave electronic products and, above all, heat-removing components, for example, heat-removing components of submodules of the AFAR system.

Claims (1)

A method of manufacturing a composite material for microwave electronic devices based on a metal matrix in the form of an aluminum alloy and a non-metallic filler in the form of silicon carbide, comprising preparing a predetermined size workpiece from silicon carbide by mixing the latter, placing this mixture in a mold, compacting the workpiece mixture, impregnating blanks with molten aluminum alloy under pressure, crystallization by creating a temperature gradient, characterized in that they use aluminum alloy silicon content 6 ÷ 12% as an alloying element, wherein the use of silicon carbide of hexagonal crystal system 6H structure as a mixture of two size fractions of 1 ÷ 15 ÷ 35 microns and 50 microns, in the ratio parts by weight 1: 5, with the content in each of them of impurities of other syngonies of silicon carbide not exceeding 20%, the preform is prepared by mixing the aforementioned size fractions of silicon carbide with the introduction of sequentially binder components in the form of sodium liquid glass and paraffin at their ratio, weight. hours, 0.004 ÷ 0.006 and 0.2 ÷ 0.22 of the total ratio of size fractions of silicon carbide, respectively, heat this mixture at a temperature of 70 ÷ 75 ° C, and the workpiece mixture is sealed by slip casting under a pressure of 0.5 ÷ 1.0 MPa into the aforementioned mold, then the preform is removed from the given mold and sintered at a temperature of more than 750 ° C, and the aforementioned impregnation of the preform with molten aluminum alloy under pressure is carried out at a temperature of 890 ÷ 900 ° C, a pressure of 80-100 MPa for 30 ÷ 50 s in another detachable mold from durable material, commensurate with the workpiece.