RU2288074C1 - Method for manufacturing semifinished products of aluminum base powder composition material - Google Patents

Abstract

FIELD: construction composition materials on base of aluminum, possibly used in article of precise machine engineering, for example at developing instruments of control systems of air crafts.

SUBSTANCE: method comprises steps of mixing powder of aluminum alloy and silicon powder; pouring prepared mixture into capsule at percentage density of poured material 0.62 - 0.63. Capsule is made of pure aluminum at next relation of its sizes: diameter to height - no more than 1 : 3; wall thickness to diameter, no less than 1 :5. Then degassing is realized in vacuum apparatus for three stages at temperature and time duration providing stable fineness of structure similar to initial state structure of powder. At first stage degassing is performed in vacuum; second stage of degassing is performed in inert gas and third stage of degassing is performed at evacuation degree 5 x 10^-5 - 1 x 10^-5 mm of Hg. After accumulation of gaseous impurities in space of vacuum apparatus till 3 lx micron/s, degassing process is interrupted.

EFFECT: possibility for producing material with uniform fine structure and high physical and mechanical properties.

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Description

Technical field

The invention relates to powder metallurgy and can be used as a structural material in precision engineering products, including the creation of command devices for aircraft control systems with high operational characteristics, which require a combination of such product properties as low specific gravity, low linear coefficient expansion (klr), high dimensional stability and vacuum density. The material must also be environmentally friendly.

State of the art

A known method of manufacturing a compact material containing a metal matrix of aluminum or aluminum alloys and particles of a solid reinforcing phase, including mechanical solid-phase alloying of aluminum or an aluminum alloy in a ball mill in a nitrogen atmosphere, stabilization of the alloyed powder (i.e. make it non-pyrophoric) mixing the stabilized powder with reinforcing particles (for example, silicon carbide), filling the powder mixture into the container, heating and vacuum pumping the container, sealing the container Nera and its subsequent hot pressing.

The disadvantage of this method is the high energy intensity and the complexity of the process, a high coefficient of linear expansion, poor machinability and high density, low dimensional stability (US Patent No. 4557893, 10.12.85, IPC 22 P 1/00). All this does not allow to obtain material with high characteristics and operational reliability over a long service life.

A known method of manufacturing semi-finished products from a composite material, including obtaining aluminum alloy powder, introducing silicon powder into it, filling the powder composite mixture into capsules, vacuum degassing, sealing and hot isostatic pressing (RF Patent No. 2174456, IPC B 22 P 3/15), adopted as the closest analogue of the invention (prototype).

The disadvantage of this method is the instability of obtaining blanks of the required size and quality required, which leads to increased marriage and an increase in the cost of the material; the impossibility of precise control of the end of the degassing process, which leads to an overestimated content of gaseous impurities in the material and, as a result, to a deterioration in the physicomechanical characteristics (cdp, vacuum density, ductility, etc.). All this does not allow to obtain high quality material, therefore, to ensure high operational reliability of the material over a long service life.

Summary of the invention

The problem to which the invention is directed, is to obtain a material with a homogeneous fine structure, high physical and mechanical properties (low potency, high dimensional stability and vacuum density, high processability) and operational reliability of the material over a long service life as well as expanding the range and size of the resulting semi-finished products, reducing the complexity and energy intensity of the process.

To solve the problem in a method for producing semi-finished products from a powder composite material based on aluminum, including obtaining an aluminum alloy powder, introducing silicon powder into it, filling the resulting powder composite mixture into capsules, degassing the powder mixture, sealing the capsules at the end of the degassing process, and hot isostatic pressing while using capsules made of pure aluminum, which have the following aspect ratio: diameter to height - not more than 1: 3, thickness a wall-to-diameter - no more than 1: 5, and the bulk density of the mixture in a capsule - within 0,62-0,63 relates .; the hot degassing process in a vacuum installation is carried out using vacuum or an inert gas at a temperature and a holding time that ensure that the dispersion of the structure is close to the initial state of the powder mixture, and the end of the degassing process is carried out if gas impurities flow from the degassed material into the vacuum volume installations under vacuum 5 × 10 ^-5 -1 × 10 ^-5 mm Hg makes no more than 3 l · mk / s.

The proposed method allows to preserve a homogeneous finely dispersed structure in the semi-finished product, practically no different from the structure of the initial powder mixture, to have a stable minimum content of gas impurities in the material and thereby provide high physical and mechanical properties on the semi-finished products. This is ensured by the analytical and experimental justification for choosing the optimal sizes of technological capsules and the density of the filling of the composite mixture in them, as well as the use of a fundamentally new process of degassing the powder mixture. The essence of the proposed method lies in the fact that the degassing process for the purpose of its optimization is carried out at certain stages either in a vacuum or in an inert gas medium - helium, since the latter has the highest permeability compared to other gases. In the first stage, in order to prevent additional oxidation, degassing is carried out in a vacuum. Then, for the intensification and uniformity of heating the powder mixture in the volume of the entire capsule, the degassing process is carried out in helium, due to which the total degassing time is sharply reduced and, consequently, the temperature-time effect on the structural state of the material is reduced. In addition, the use of helium as a degassing medium, especially during the period of maximum gas separation, also significantly accelerates the degassing process and eliminates the possibility of segregation of gas impurities in the powder mixture in the capsule volume. The last stage of degassing is carried out in vacuum 5 × 10 ^-5 -1 × 10 ^-5 mm Hg mainly to remove inert gas (helium), as well as dissolved hydrogen released from the powder. The end of the degassing process is carried out in the event that the leakage of gas impurities from the degassed material into the volume of the vacuum installation at a vacuum of 5 × 10 ^-5 -1 × 10 ^-5 mm Hg makes no more than 3 l · mk / s. All this ensures the production of a material whose structure practically corresponds to the structure of the starting material, i.e. finely dispersed evenly distributed in the α-solid solution precipitates of primary silicon crystals and intermetallic phases NiAl ₃ , FeAl ₃ , AlN, AlP, which is the main condition for the production of an article from this material with high performance characteristics and their reliability over a long service life.

Description of Embodiments

The proposed method for producing semi-finished products from a powder composite material based on aluminum was tested on three compositions of the composite material.

Example 1. In a powder of an aluminum-based alloy (containing 27% silicon, 4.6% nickel, 0.075% phosphorus, 0.03% aluminum nitride — powder composition mixture No. 1), the particle size of which was not more than 60 μm, the powder was introduced silicon, the particle size of which was also not more than 60 microns, in a ratio of 3.76: 1. Mixture No. 1 was poured into sealed technological capsules made of pure aluminum, with the following aspect ratio: diameter to height - not more than 1: 3, wall thickness to diameter - not less than 1: 5, and the density of the mixture in the capsule was within 0 , 62-0.63 rel., With simultaneous compaction to a density of 1.62-1.65 g / cm ³ (0.62-0.63 rel.). Capsules with the powder composite mixture were placed in a vacuum heating unit and degassed using vacuum and inert gas at a temperature and holding time, which ensured that the dispersion of the structure was close to the initial state of the powder mixture. At the same time, the end of the degassing process was carried out after gas impurities from degassed material in the volume of the vacuum installation under vacuum 5 × 10 ^-5 -1 × 10 ^-5 mm RT.article amounted to no more than 3 l · μ / s. At the end of the degassing process without changing the parameters of the vacuum and temperature, the capsules were sealed. The process of hot isostatic pressing of sealed capsules was carried out in a gas bath at 520 ° C with a force of 1100 ati and holding for 3 hours. The resulting blanks were machined to remove a process aluminum capsule.

Example 2. In a powder of an alloy CAC1-50, doped with beryllium (0.03% Be) and aluminum oxide (2.2% Al ₂ O ₃ ), silicon powder was introduced in a ratio of 4: 1 — powder composition mixture No. 2. The modes of subsequent processing of the prepared mixture No. 2 to obtain a compact billet was carried out in accordance with example 1.

Example 3. In a powder of an alloy CAC1-50 was introduced a powder of silicon nitride in a ratio of 6: 1 - powder composite mixture No. 3. Modes and schemes for subsequent processing of the prepared mixture No. 3 to obtain a compact billet was carried out in accordance with example 1. In addition to these examples, the same three composite materials were obtained by a known method.

The data of the analysis of the physicomechanical properties of powder composite materials obtained in accordance with examples 1-3 are shown in the table, also the table shows the properties of materials obtained by the method known from the prototype with the same set of components as in examples 1-3. From an analysis of the results shown in the table, we can conclude that the best technical result is achieved using the proposed method, which allows you to get a material with a structure that is practically consistent with the starting material, i.e. finely dispersed evenly distributed in the α-solid solution precipitates of primary silicon crystals (mainly globular in shape) and intermetallic phases NiAl ₃ , FeAl ₃ , AlN, AlP, which are decisive in ensuring high physical and mechanical characteristics of the material.

Thus, using the proposed method, we obtain a material: with a high modulus of elasticity, a low coefficient of linear expansion, increased strength and plastic characteristics, low gas impurities, high dimensional stability and vacuum density, improved machinability. In addition to the above, the material obtained by this method has a minimal ratio of to thermal conductivity (α / λ), which is evidence of minimal temperature deformations and stresses that occur in products under the influence of temperature fluctuations during operation and storage.

All this guarantees high performance and high reliability of products made from this material over a long service life. In addition, a material with the specified characteristics allows you to expand the range of semi-finished products, reduce the cost of their manufacture and significantly expand the scope of their use.

Table
METHOD FOR PRODUCING SEMI-FINISHED PRODUCTS FROM POWDER COMPOSITE MATERIAL BASED ON ALUMINUM No. p / p Methods of obtaining material (composition of the components in accordance with examples 1, 2, 3) Specific elastic limit E / ρ Conditional C.L.R., α / λ Total gas content, ^cm3 / 100g Vacuum density at wall thickness, mm Machinability one Proposed No. 1 45.8 0.1 2,5 ^0.65-0.02 sat. 2 Proposed No. 2 41.3 0.12 3.0 ^0.85-0.02 sat. 3 Proposed No. 3 41.5 0.15 3.0 1.10 ^-0.02 dissatisfied. four Famous No. 1 40.5 0.20 6.2 1.00 ^-0.02 sat. 5 Famous No. 2 36.6 0.25 6.7 1.30 ^-0.02 sat. 6 Famous No. 3 37.0 0.35 8.0 ^1.35-0.02 dissatisfied.

Claims (1)

A method of producing semi-finished products from an aluminum-based powder composite material, comprising mixing aluminum alloy powder and silicon powder, filling the resulting mixture into a capsule, degassing in a vacuum unit, sealing the capsules after degassing, and hot isostatic pressing, characterized in that the mixture is poured into a capsule with a relative density of backfill of 0.62-0.63, made of pure aluminum, having the following size ratios: diameter to height - not more than 1: 3, wall thickness to diameter - not less than it is 1: 5, degassing is carried out in three stages at a temperature and holding time, ensuring the preservation of the dispersion of the structure close to the initial state of the powder mixture, while in the first stage degassing is carried out in vacuum, the second stage of degassing is carried out in an inert gas, and in the third stage, degassing lead under vacuum 5 · 10 ^-5 -1 · 10 ^-5 mm Hg, and degassing is stopped when the leakage of gas impurities into the volume of the vacuum installation is not more than 3 l · µ / s.