RU2649632C2 - Method of obtaining composite material aluminum-steel - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to the production of composite material aluminum-steel. Method includes forming a multilayer work material by interlacing aluminic layers and steel mesh layers, compacting the multilayer work material by pressing and heat-treating it to obtain a composite material. As the aluminic layers interlace layers made of a filling of aluminum powder with a plate-like shape particle, as a steel mesh, mesh with mesh sizes of 3–5 mm, woven from a wire of 0.8–1.0 mm in diameter, the ratio of the thickness of the aluminum powder layers and the thickness of the steel mesh in the multilayer work material is from 2:1 to 3:1. Compacting of the multilayer work material by pressing is carried out at a pressure of 700–1,000 MPa, and the heat treatment is carried out in air at a temperature of 550–600 °C for 15–30 minutes. Production of a composite material with a density of 2.60–2.85 g/cm³, impact strength KCU (5-8)⋅10⁶ J/m² is provided.

EFFECT: production of a composite material is provided.

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Description

The invention relates to the technology of composite metallic materials and can be used to produce lightweight, impact-resistant products, as well as structural elements operated under conditions of alternating loads when heated to a temperature of 550-600 ° C.

Such materials are required to combine low density (lightweight materials) with increased impact strength (KCU) and specific effective fracture work (γ _F ), which largely determines the working life of the products.

A known method of producing a composite material aluminum - steel [1], including winding coils of steel wire with a certain step on aluminum (matrix) layers, laying such layers in a bag and rolling it with a given degree of deformation.

The disadvantages of this method are the relatively low rates of fracture characteristics (KCU and γ _F ), the relatively high density, as well as the anisotropy of the mechanical properties of the resulting composite.

The closest to the claimed technical essence and the achieved effect is a method of producing a composite material aluminum - steel [2] (adopted as a prototype), which includes the formation of a multilayer billet - a package by alternating aluminum layers (in the form of foil with a thickness of 0.05-0.5 mm or sheets with a thickness of more than 0.5 mm to 1.5 mm) and steel nets of “knitted” weaving from high-strength, cured wire (X18N10T; U8A or X13N13M2) 0.02-0.2 mm thick with mesh sizes from 0.6- 0.8 mm to 2 -2.5 mm.

The multilayer preform was compacted by pressing, positioning it between two plane-parallel steel plates. Then it was wrapped in aluminum foil and placed in a sealed vacuum container of flexible sheet steel. A vacuum was created in the container and transferred to the furnace, heating to a predetermined temperature (below the melting point of aluminum: 500-600 ° C) with an isothermal exposure of 8-10 minutes.

After that, a heated container with a multilayer workpiece under rarefaction conditions was moved under the friction hammer of a dynamic hot pressing (DTP) plant and a blow was struck from a fixed height.

In this case, it is possible to reduce the degree of anisotropy of the mechanical properties through the use of meshes as reinforcing elements. However, the disadvantages of the prototype method remain insufficiently high values of KCU and γ _{F of the} obtained composite material, as well as its relatively high density. In addition, the prototype method is time-consuming due to the need to implement a large number of technological operations, as well as the application of the accident method.

The technical task of this invention is to reduce the density of the obtained composite material, increase KCU and γ _F , as well as simplify the method of its production by reducing the number of technological operations and eliminating the use of accidents.

To accomplish the task in a method for producing an aluminum-steel composite material, which includes forming a multilayer billet by alternating aluminum-containing layers and a steel mesh, compacting the multilayer billet by pressing and its heat treatment, a multilayer billet is formed by alternating layers formed from a bed of aluminum powder with a plate-like particle shape and steel grids with a mesh size of 3-5 mm, woven from a cable with a diameter of 0.8-1.0 mm, with a ratio of the thickness of the layers of aluminum powder and a steel mesh thickness of from 2: 1 to 3: 1.

In addition, the compaction of the multilayer preform by pressing is carried out under a pressure of 700-1000 MPa, and the heat treatment of the multilayer preform is carried out in air at a temperature of 550-600 ° C for 15-30 minutes.

The essence of the method of producing composite material aluminum - steel is illustrated in graphic materials, which depict:

in FIG. 1 is a view of the cleaved surface of a composite material aluminum - steel (the size of a square cell of a cable mesh is 5 mm); pos.1 - matrix aluminum layers, pos.2 - mesh of steel cable, pos.3 - "jumpers - bridges" between adjacent matrix layers;

in FIG. 2 - view of the fracture surface of the composite material aluminum - steel after static loading (line length - marks 1.0 mm); pos. 4 - section surface aluminum matrix - steel cable, pos. 5 is a relief formed by pulling a steel cable from an aluminum matrix.

figure 3 is a view of the fracture surface of a layered aluminum matrix (line length - labels - 30 microns); pos. 6 - layered package of diffusion-related lamellar particles, pos. 7 — cavities — regions of tearing out layered packets.

To obtain the material according to the claimed method, aluminum powder of the PAP-2 grade (GOST-5494-95), consisting of lamellar particles (prevailing particle sizes: 10-100 μm in length, 5-50 μm in width, according to 0.5-1.0 μm thick). Particles of powder as a product of industrial supply are coated with a thin layer of stearin (3.0 wt.%), Introduced as a fat additive at the stage of their grinding in a ball mill.

The use of this powder to form the aluminum matrix of the composite is explained by the possibility of imparting a layered structure to it as a result of laying lamellar particles on planes during pressing. Such a layered structure of the matrix made it possible to increase its crack resistance.

A steel cable made of austenitic steel (08X17H13M2) of the A4 brand of the following chemical composition (wt.%) Was also used: C (≤0.08), Cr (16-18), Fe (66.345-74), Mn (≤2) , Ni (10-14), P (≤0.045), S (≤0.03), Cu (≤1), Mo (2-3). The twist type of the cable is 1 × 19 (in one twist, 19 wires with a diameter of 0.16-0.20 mm were used, 5 wires are laid along the cable diameter, while its diameter can be from 0.8 to 1.0 mm).

The use of this cable as a reinforcing element is due to its high strength, high modulus of normal elasticity and scale resistance. Due to the combination of such properties, it is able to fulfill the function of reinforcement, which allows providing for the composite increased fracture characteristics - KCU and γ _F.

In the inventive method, mesh was made of a steel cable with a square mesh size (l _i ) from 3 to 5 mm. A decrease in l _I less than 3 mm is not advisable, since in this case the resistance to forcing matrix aluminum powder through the cells during pressing significantly increased, which led to the formation of “delamination” cracks along the ends of the sample. An increase in l _I over 5 mm is also not advisable, since the effect of reinforcing the aluminum matrix with a cable was significantly reduced: there was a decrease in the parameters KCU and γ _F.

A decrease in cable diameter (d _t ) of less than 0.8 mm also led to a decrease in KCU and γ _F , while an increase in d _{t of} more than 1.0 mm gave a significant increase in the density of the material due to an increase in its mass.

The ratio of the thickness of the layers of aluminum powder (δ _A1 ) to the thickness of the steel mesh (δ _C ) less than 2: 1 led to “overlaps” of the grids in the adjacent layers due to the small thickness of the matrix powder layer. An increase in δ _A1 / δ _{C of} more than 3: 1 is not advisable due to a drop in KCU and γ _F.

A decrease in the pressing pressure of the multilayer preform (P) of less than 700 MPa reduced the attainable values of the parameters KCU and γ _F. An increase in P of more than 1000 MPa led to the deformation of the cable and the occurrence of “re-pressing” cracks in the aluminum matrix.

A decrease in temperature (T) and time (t) for heat treatment of the multilayer billet in air below 550 ° C and 15 min, respectively, did not allow achieving the required high values of the parameters KCU and γ _F. An increase in Tit of more than 600 ° C and 30 minutes, respectively, is not advisable, since the oxidation of the aluminum matrix of the composite and its softening due to the accumulation of the alumina phase formed with increasing volume are observed.

Examples of the implementation of the claimed method

Example 1. To prepare the matrix component of the composite material, aluminum powder of the industrial grade PAP-2 was loaded into an aluminum container with a lid and heated in air (at an average speed of 50 ° C / h) to a temperature of 350 ° C followed by isothermal exposure necessary for burning stearin from the surface of lamellar particles and its replacement with a passivating alumina film (500 g of PAP-2 was held for 3 hours). Then, the obtained powder was granulated by wetting it (based on the addition of 10 cm ^{3 of} water to 10 g of powder), then rubbing the wet powder through a sieve and drying it to zero moisture.

The reinforcing component of the composite material was obtained by weaving a mesh with a mesh size (l _I ) of 3 mm from a steel cable with a diameter (d _t ) of 0.8 mm (austenitic steel - 08X17H13M2, twisting type - 1 × 19, 5 wires with a diameter of 0 are laid along the cable diameter, 16 mm). For weaving used a special device.

To form a multilayer billet, 20.5 g of matrix aluminum powder was poured into a socket of a steel mold (85 × 100 mm) and leveled in the form of a layer uniform in thickness. A mesh woven from a cable was laid on the surface of this layer. Then, matrix matrix aluminum powder was again filled with the indicated fixed sample, which ensured the ratio of the powder layer thickness and the mesh thickness (δ _A1 / δ _s ) as 2: 1.

Thus, sequentially alternating layers of aluminum powder and steel wire mesh, a multilayer billet was obtained (a total of 5 nets and 6 layers of aluminum powder, the outer layers are made of aluminum powder).

Next, the multilayer preform was compacted by compression, applying pressure (P) - 700 MPa.

The heat treatment of the multilayer preform was carried out in air according to the following regime: heating to a temperature (T) of 600 ° C in 0.5 hours, followed by isothermal exposure (τ) of 15 minutes.

As a result of heat treatment, a sintered sample was obtained in the form of a plate with a density of 2.85 g / cm ³ with a volume fraction of the reinforcing component of 20%. Prismatic samples were cut from this plate to study the fracture characteristics of the material (KCU and γ _F ).

Example 2. The type and sequence of technological operations coincide with those in example 1.

The reinforcing component of the material was obtained by weaving a mesh of steel cable: austenitic steel - 08X17H13M2, l _i = 4 mm, d _t = 0.9 mm, twist type - 1 × 19, 5 wires with a diameter of 0.18 mm are laid along the cable diameter.

To form a multilayer billet, 28.7 g of matrix aluminum powder was poured into a socket of a steel mold (8 × 100 mm) and leveled in the form of a layer uniform in thickness.

Further, sequentially alternating layers of aluminum powder and steel wire mesh, a multilayer billet was obtained (a total of 5 nets and 6 layers of aluminum powder, the outer layers are made of aluminum powder, δ _A1 / δ _s = 2.5: 1).

The multilayer preform was compacted by pressing (P = 850 MPa), and heat treated in air (T = 570 ° C, τ = 45 minutes).

As a result of heat treatment, a sintered sample was obtained in the form of a plate with a density of 2.75 g / cm ³ with a volume fraction of the reinforcing component of 18%. Prismatic samples were cut from it to determine the parameters KCU and γ _F.

Example 3. The type and sequence of technological operations coincide with those in examples 1 and 2.

The reinforcing component of the material was obtained by weaving a mesh of steel cable: austenitic steel - 08X17H13M2, l _i = 5 mm, d _t = 1.0 mm, twist type - 1 × 19, 5 wires with a diameter of 0.2 mm are laid along the cable diameter.

To form a multilayer workpiece, 38 g of matrix aluminum powder was poured into a socket of a steel mold (85 × 100 mm) and leveled in the form of a layer uniform in thickness.

Further, sequentially alternating layers of aluminum powder and steel wire mesh, a multilayer billet was obtained (a total of 5 nets and 6 layers of aluminum powder, the outer layers are made of aluminum powder, δ _A1 / δ _s = 3: 1).

The multilayer preform was compacted by pressing (P = 1000 MPa) and heat treated in air (T = 550 ° C, τ = 30 minutes).

As a result of heat treatment, a sintered sample was obtained in the form of a plate with a density of 2.60 g / cm ³ with a volume fraction of the reinforcing component of 15%. Prismatic samples were cut from it to determine the parameters KCU and γ _F.

The solution to the technical problem of this invention — reducing the density of the composite — is achieved by forming a light and crack-resistant layered powder matrix in its composition (whereas by the prototype method, the matrix is formed from dense foils and sheets obtained by rolling, in addition, the accident method provides significant material compaction )

Increased values of the parameters KCU and γ _{F of the} claimed composite are provided due to its effective reinforcement with a wire mesh and due to the high resistance to destruction of the layered aluminum matrix. So, for example, for its destruction as a result of the application of an impact load (Fig. 1), high energy costs are required for the destruction of the twist of wires in the cable network (pos. 2) located between the matrix aluminum layers (pos. 1), as well as for the destruction by cutting off "bridge jumpers" (pos. 3) connecting adjacent matrix layers.

In addition, in the case of both static and shock loading of the composite (Fig. 2), there is significant energy consumption for overcoming the friction forces along the “matrix-cable” interface (item 4) when pulling sections of the cable from the matrix with the formation of a pronounced relief its surface (item 5).

During mechanical tests, the increased fracture resistance of the layered aluminum matrix (Fig. 3) is ensured by the significant energy consumption of the process of “tearing out” of layered packets (pos. 6), consisting of diffusion-bonded plate particles, with the formation of cavities (pos. 7).

When loading the material obtained by the prototype method, there is no manifestation of the above mechanisms, which can further increase the fracture resistance. Its mechanical properties are determined by the number and strength of contacts along the mating surface of the steel mesh and aluminum sheet that arise as a result of diffusion welding during an accident.

The simplification of the claimed method (compared with the prototype) is achieved by reducing the number of technological operations and eliminating the need for the use of accidents.

According to the prototype method, the following technological operations are carried out: 1) forming a multilayer workpiece by alternating aluminum layers (foil or sheets) and a steel mesh, 2) compacting the multilayer workpiece by pressing, 3) placing it in a sealed container and creating a vacuum in it by pumping air, 4) heating the container containing the multilayer workpiece during rarefaction to a temperature of 500-600 ° C with a subsequent predetermined isothermal exposure, 5) carrying out an accident, 6) removing the resulting composite from the container.

In accordance with the claimed method, the following technological operations are performed: 1) the formation of a multilayer workpiece by alternating layers formed from backfill of aluminum powder with a plate-like particle shape and steel grids woven from a cable, 2) compaction of the multilayer workpiece by pressing, 3) heat treatment of the multilayer workpiece in air at a temperature of 550-600 ° C.

The table presents data on the physico-mechanical properties of the material obtained by the claimed method in comparison with the material manufactured by the prototype method.

For a correct comparison, the material was made according to the prototype method, using high-strength steel wire (X13H13M2) with a diameter of 0.2 mm and a mesh size of 2.5 mm for mesh weaving, the volume fraction of reinforcing meshes was 15-20% (as in the claimed method), V As the matrix layers, foils and sheets of AMg6 alloy with a thickness of 0.1-0.5 mm were used, the specific work of the accident was 0.8 J / g.

The density of the composite was calculated by the formula: ρ = m / V (m and V are the mass and volume of the sample, respectively).

Impact strength according to the parameter KCU was determined in accordance with GOST 9454-78.

To determine the specific effective work of fracture (γ _F ), strain diagrams were recorded in the coordinates “load (P) - deflection (δ)" during bending by a concentrated load of prismatic samples cut into half the height - 10 × 12 × 55, mm (radius of curvature of the notch tip - 50 μm, the loading speed is 1 mm / min) [1]. The specific effective work of destruction was calculated by the formula:

γ _F = U / 2S, where U is the work of destruction, estimated by the area of the graph P - δ, S is the surface of destruction.

Thus, the technical task of the invention was achieved: in comparison with the prototype, a simplification of the method for producing aluminum-steel composite material was achieved by reducing the number of technological operations; there also takes place (see table) a decrease in its density with an increase in the specific effective work of fracture and impact strength not less than by an order of magnitude.

Information sources

1. Ivanov D.A., Sitnikov A.I., Shlyapin S.D. Dispersion-strengthened, fibrous and layered inorganic composite materials / study guide. - M.: MGIU, 2010, 230 p.

2. Karpinos DM, Maksimovich GG, Kadyrov V.Kh., Lyuty EM The strength of composite materials. Kiev: Naukova Dumka, 1978, 236 p. (prototype).

Claims (1)

A method of producing an aluminum-steel composite material, comprising forming a multilayer billet by alternating aluminum-containing layers and steel mesh layers, compressing the multilayer billet by pressing and heat treatment to obtain a composite material, characterized in that as aluminum-containing layers alternate layers made of backfilled aluminum powder with plate-shaped particles, as a steel mesh use a mesh with a mesh size of 3-5 mm, woven from a cable with a diameter of 0.8-1.0 mm, with this ratio of the thickness of the layers of aluminum powder and the thickness of the steel mesh in the multilayer billet is from 2: 1 to 3: 1, and the compaction of the multilayer billet by pressing is carried out at a pressure of 700-1000 MPa, and heat treatment in air at a temperature of 550-600 ° C for 15-30 minutes.

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