RU2001718C1 - Process of manufacture of dispersion-compressed material - Google Patents

Abstract

Use in powder metallurgy, in particular for the production of alloys by hot pressing of powders with the addition of fine particles into the metal matrix. SUMMARY OF THE INVENTION: use as a hardening phase of ultrafine diamond (UDD) with a highly developed specific surface, the introduction and mixing of which with the hardened metal phase is carried out in a mechanical activator. The use of ultradispersed diamond as a dispersion hardening phase has become possible only at present in connection with the development of industrial technology and the production of high-purity UDD. A hardened metal (aluminum) has been obtained with improved mechanical characteristics and its ductility, ductility, and lightness have been preserved. The simplicity of the process and the use of domestic equipment for the production of hardened metal allows us to conclude that there is a promising development of this direction and the widespread introduction of new material in industry. 2taba

Description

The invention relates to powder metallurgy, in particular to alloys of metal modification obtained by hot pressing of powders with the addition of fine particles into the metal matrix. The present invention can be used for dispersed hardening of a metal operating under high technical conditions and requiring high strength.

Various alloys and composites are known, for example, on an aluminum basis, as high strength lightweight materials having high stability of their characteristics and ease of manufacture. The necessary properties of the composites can be achieved by choosing a modifier (reinforcing agent, additives), its size and quantity. Typical reinforcing agents include graphite, silicon carbide, alumina, boron carbide, boron nitride. The reinforcing substance may be in the form of discrete particles with sizes of 1-200 μm, threads with a diameter of 1 μm and a length of 10-80 μm and any other shape and size. Aluminum composites are made by casting and using powder metallurgy and pressing.

Of. Aluminum powder alloys described in the literature are closest to the claimed alloy of the SAP type (sintered aluminum powder). One method for improving powder alloys is by treating powders in attritors. as well as mechanical mixers such as ball mills. Before sintering, the powder is milled in order to incorporate dispersed particles into the matrix and obtain particles of the desired size and shape.

One of the features of the preparation of such materials is the introduction of dispersed materials that are not soluble during sintering and operation. A characteristic feature in them is the presence of finely dispersed inclusions in the metal base, i.e., a hardening phase uniformly distributed between metal particles and chemically inert to them. The most effective hardening is achieved when the content of the hardening phase is 3-15% (volume), its particle size is up to 1 micron (better than 0.01-0.05 micron). This is explained by the fact that, in the presence of a second phase particle matrix, glide of dislocations in the metal grains becomes possible only at high stresses, the mobility of the boundaries of these grains is blocked, and the grain growth is inhibited almost to the melting temperature of the matrix. To reinforcing

phases include oxides, carbides, metal nitrides, refractory metals, etc.

The permissible volumetric content of the hardening phase is determined by the technological possibilities of obtaining a uniform distribution of its particles of the selected dispersion. The method of introducing the hardener phase particles into the matrix depends on the choice of the type of structure of the dispersion-strengthened material.

When creating a dispersion hardened material, the following requirements are imposed on the phase hardener: high thermodynamic strength, low speed

diffusion of phase components into the metal matrix and its solubility is small, high purity and large total (specific) surface of the particles of the dispersed phase. To hardening phases with such properties

oxides, carbides, nitrides, some metals and intermetals can be attributed. All of them are combined in that they can have a particle size (powder) of up to 1 μm, high microhardness of 10-49 GPa.

One of the dispersion hardening metals is aluminum. Reinforced aluminum is obtained from APS grade aluminum powder. Alumina A1203 is used as the hardening phase, the content of which in various grades is in the range of (6-17)%. The particle size of the aluminum powder is 2 microns or more.

In order to obtain an aluminum powder product, the following process steps must be carried out:

1, Preparation and pressing of powder.

In order to carry out pressing under optimum conditions, to obtain briquettes or preforms for further sintering, it is necessary in some cases to pretreat the powders: mixing, sieving, grinding, etc., which are carried out at powder manufacturing plants.

For compression, the powder is placed in

mold and compress. As a result, it deforms, decreases in volume, and forms its size and shape. When pressed, the material is compacted, individual

particles, the filling of voids, plastic deformation occurs.

2. Sintering.

Compressed briquettes (or billets) are subjected to sintering to obtain the desired physical and mechanical properties. A characteristic feature of sintering is that it is carried out without melting the main component at Tc 0.7 0 9Tp of the main phase (OV Roman,

I.P. Gabrielov. Handbook of powder metallurgy. Minsk: Belarus, 1988).

Because in the patent and scientific information literature there is no data on dispersion-hardened materials and their properties obtained by using powder metallurgy methods, then for the prototype we take the material obtained by us according to the above methodology. The reinforcing material was aluminum, an ASD powder with a grain size of 2-5 microns, and disperse A1aOz with a grain size of 0.1-5 microns as a strengthening phase. The amount is 1.5-2.5% of the SDA. The resulting sintered aluminum has the following main characteristics:

Vickers microhardness,

HV, GPa0.50

Brinell hardness

HB, GPa0.475

The resulting specs have ductility and can be forged and stamped. However, when comparing with the well-known aluminum grades (in terms of strength characteristics) of D-16, AMC, as well as with pure ASD powder sintered by a similar technique, the obtained dispersion-hardened aluminum has the worst characteristics.

The results are shown in table. 1.

Therefore, the existing method of producing dispersion-hardening material in powder metallurgy does not always allow to obtain positive results, using, for example, ALOe and the well-known technology as the surfactant phase.

The aim of the invention is to develop a method that improves the strength characteristics of the main phase of the metal due to the dispersed phase of the hardeners.

In the known method of dispersed hardening of a metal, which consists in preparing powders, pressing and sintering, an ultrafine diamond with a specific surface area of 300-400 m / g in an amount of 1.5-2.5% of the hardened metal phase is used as the dispersed phase of the hardener. the introduction and mixing of which is carried out in a mechanical activator in argon medium for 3-6 minutes. The ultrafine diamond (UDD) used to harden the metal has the following characteristics:

about

average particle size, A 50 specific surface area. m2 / g 300-400 temperature of graphitization, ° С 700-1000

(depending on the pressing technology)

Diamond is the hardest material known, and also has the highest thermal conductivity and other characteristics that allow it to be widely used 5 as a tool in the processing of hard and superhard materials. According to published data, diamond is neutral to metals and insoluble in many of them. Based on the foregoing, UDD has a significant advantage over other dispersed materials used for hardening metals in powder metallurgy. Most appropriate it

5 to use for metals with a melting point not higher than the oxidation temperature (graphitization) of UDD. It is known that imperfections of the crystal lattice (the presence of dislocations, defects) leads to the effect

0 hardening, i.e. materials with high defect density have increased strength. Therefore, the problem of obtaining materials with high physical and mechanical properties can be solved by

5 using ultrafine particles

about

(size 10-100 A) with a highly developed specific surface (300-400 m2 / g). Using UDD to compact just

0 and leads to a material with a high density of defects, and hence with increased strength characteristics. To uniformly mix the powders, as mentioned above, a mechanical activator was used. The mechanical activator in this case performs two functions:

1 T.K. Because UDD has a highly developed active surface due to its ultradispersity, UDD particles are surrounded, as it were, by a fur coat consisting of oxides, salts, radicals, and other elements. Therefore, the UDD is poorly pressed. Processing UDD and hardened metal in a mechanical activator in an inert gas (in this case argon) due to mechanochemical reactions that take place during activation, the fur coat is removed and UDD is cleaned.

2. After the passage of mechanochemical reactions, uniform mixing of the constituent powders occurs: the phases of the hardener - UDD and the hardening metal. Due to its high reactivity, uniform

5 mixing powders and their conglomeration to a size of 100 microns. A powder with such a fraction compacts well and is sintered. The metal whose matrix is to be hardened is chosen as AI to be strengthened. Thanks to its characteristics. such as lightness, malleability, high thermal conductivity, strength and corrosion resistance, etc. .. it is an indispensable material in electronic engineering, aircraft manufacturing, mechanical engineering, construction, etc.

The melting point of AI is Tm 650 ° C, which is significantly lower than the graphitization temperature of diamond (UDD), diamond (UDD) is insoluble in AI. The limits of its solubility are not precisely established, however, there is evidence that they are significantly less than hundredths of a percent.

Therefore, the metal matrix AI is the most suitable for hardening with ultrafine diamond - UDD. To obtain hardened AI, aluminum powder of the ASD grade with a grain size of 1-5 microns was used.

Before pressing and sintering, special mechanical processing of the ASD and UDD in a mechanical activator was carried out. Mechanical activation was carried out under the following conditions: container acceleration, m / s260 q

container chamber volume, cm3

8300 30-50

powder loading mass, g size of metal balls in the container - d, mm 6-8 ball loading mass, kg1

powder processing time in a mechanical activator, min 3-6 Mechanical activation and unloading of the container was carried out in an inert gas medium - argon. The conditions under which mechanical activation was carried out are optimal. If one or more of the above parameters is violated, the resulting sintering powder is oxidized, smeared on the walls of the container and balls, not briquetted. The use of a mechanical activator to mix A1gO3 with ASD did not yield positive results by the above procedure.

After treatment, the powder was normalized in a mechanical activator at T 250-300 ° C for 1 hour. To obtain a hardened material (AI), the amount of UDD was 0.5-1.0%. 1.5-2.5%, 10%, 20% by weight of aluminum powder (ASD).

The resulting mixture of powders was poured into the mold according to the above technology and briquetted on a hydraulic press at a pressure of P 0.45 GPa. After briquetting, sintering was carried out with the following parameters:

sintering pressure. GPa 1.0 sintering time, caraway seeds 5 sintering temperature, T ° С 550-600

The obtained, hardened by ultrafine diamond, aluminum, as well as AI + AlaOa and pure aluminum were subjected to electron microscopy, X-ray phase analysis, determination

0 hardness and microhardness.

The measurement results are presented in table. 2.

Analysis of the results of the study showed a fundamental difference between the obtained cakes, given as in table. 1, and in table. 2. Of the dispersion-hardened AI, the best characteristics are for cakes with 1.5–2.5% UDD content, although with an increase in UDD content, hardness and microhardness increase, but such material already becomes non-plastic, brittle, which does not allow its use like aluminum alloys, which have good ductility, ductility. Therefore, 1.5-2.5% of the UDD content as the hardening phase of aluminum was selected as the most optimal. Compared with the measurement results of known aluminum alloys and sinter ASD and

0 1.5-2.5% A1203 + ASD obtained aluminum reinforced using UDD has obvious advantages, a more homogeneous and thin structure, while remaining a plastic material. X-ray phase

5, an analysis of the obtained hardened aluminum UDD showed the presence of a diamond phase in the AI lattice. The use of UDD as a dispersion hardening phase has become possible only at the present time in connection with

On the development of industrial technology and the production of high-purity UDD.

Hardened aluminum with improved mechanical characteristics was obtained, and its ductility, ductility, and lightness were preserved with a low UDD 5 content of 1.5–2.5%. Using powder metallurgy methods, it is possible to produce various components and parts from it for the automotive and aircraft industries,

0 electrical and construction, space technology, where high strength and wear resistance are required. Using various press tools made of hardened aluminum, components and parts can be sintered with

5 minimal mechanical refinement. Because the obtained aluminum with a low content of UDD is malleable and ductile, from sintered briquettes it is possible by stamping and rolling to obtain products with a complex configuration and profile Level analysis

The patent literature has shown the novelty of the proposed solution. The use of UDD for hardening metals is a new area in powder metallurgy and currently there is no such way to solve this problem.

The technical solution of the present invention for specialists in no way follows from the development of technology, the technical solution has an inventive step.

The simplicity of the process and the use of domestic equipment for the production of hardened metal allows us to conclude that there is a prospective development of this direction and the widespread introduction of new material in industry.

(56) Kiparisov S.S. and Libenson G.A. Powder metallurgists. M .: Metallurgists, 1972, p. 504, 505.

Claims (1)

The claims METHOD FOR PRODUCING DISPERSED Hardened MATERIAL mainly based on aluminum, comprising mixing metal powders and hardening phase, pressing and sintering, characterized in that as Table 1 table 2 The hardening phase uses ultrafine diamond with a specific surface area of 300-400 m2 / g in an amount of 1.5-25% of the metal powder, and the powders are mixed in a mechanical activator in argon medium for 3-6 minutes.