RU2616316C1 - Conductive extra low interstitial aluminium alloy and method of its production - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: conductive extra low interstitial aluminium alloy contains at least one alloying component selected from the group of rare earth metals, iron and silicon. The rare earth elements are selected from the group consisting of La, Ce, Nd, Pr, with the following component content, wt %: at least one alloying component selected from the group La, Ce, Nd, Pr 7.0-9.0, iron 0.05-0.1, silicon 0.05-0.1, aluminium is the rest. The alloy has a structure with an average grain size of not more than 400 nm and particles of the eutectic phase Al₁₁RE₃, which are uniformly distributed over the grain volume and have a spherical shape with a size of not more than 50 nm, and the interparticle distance is not more than 150 nm. The method of obtaining the alloy includes intense plastic deformation with a true accumulated deformation rate e≥4 with a pressure of 0.5-6.0 GPa applied in the homology temperature range 0.3-0.5 Tp, and annealing in the temperature range 280-400°C for at least 1 hour.

EFFECT: higher strength and heat resistance with satisfactory electric conductivity in the alloy.

3 cl, 1 ex, 1 tbl, 2 dwg

Description

The invention relates to the field of non-ferrous metallurgy and electrical engineering, in particular, to aluminum-based alloys, and can be used in the manufacture of electrical products (round and square conductors, wires of power lines, conductive elements in the form of wires, plates and tires), working with increased mechanical stress and experiencing high temperatures during operation.

Known heat-resistant alloy based on aluminum, containing, by weight. %: 0.28-0.50Zr, 0.16-0.30Si, 0.1-0.4Cu, 0.15-0.80Mn [EP 0787811, IPC C22C 21/00, publ. 08/06/1997]. In order to achieve a given set of physicomechanical properties of the alloy preform, it is subjected to prolonged heat treatment in the temperature range of 320-390 ° C for 30 to 300 hours before final processing by cold drawing. The conductive elements in the form of a wire from this alloy have a good combination of temporary resistance (σ _B ) and electrical conductivity (σ _B = 270 MPa and electrical conductivity 55% IACS). However, their operating temperature does not exceed 150 ° C. In addition, a significantly longer time is required for the manufacture of blanks.

Known aluminum alloys containing rare earth metals used in structural parts and conductors that carry low and medium loads. For example, a heat-resistant alloy based on aluminum for electrical wires is known [patent RU 2492258, IPC C22C 21/00, publ. September 10, 2013]. The alloy contains iron, at least one metal selected from the group of rare earth metals, as well as beryllium in the following ratio of components, wt.%: Metal selected from the group of rare earth metals 2.5-4.5, iron 0.05-0.1, beryllium 0.05-0.1, aluminum - the rest, and the size of inclusions of eutectic intermetallic compounds of rare-earth metals in the microstructure of the alloy is less than 1 μm.

A cast alloy wire with such a structure, obtained as a result of cold drawing, has a temporary resistance (σ _B ) of 253-260 MPa and an electrical conductivity of 52.2-57.4% IACS at room temperature. However, already at a temperature of 250 ° C, it undergoes significant softening (σ _B decreases to 110 MPa).

Known alloy containing the following components, wt. %: at least one rare-earth metal 5.0-10.0, oxygen 0.002-1.5, nitrogen 0.002-1.2, hydrogen 0.0002-0.5, aluminum - the rest [patent RU 2344187, IPC C22C 1/02, publ. January 20, 2009].

Alloy samples, depending on the content of rare-earth metals, have a temporary resistance of 260-350 MPa at room temperature and an electrical conductivity of 53-59% IACS. However, at a temperature of 350 ° C, the alloy samples are greatly softened. Their σ _B decreases to 140-250 MPa. In addition, for the production of electrical products in the form of a wire from samples of these alloys, labor-intensive and energy-intensive granular technologies are used, which leads to an increase in the number of technological operations for obtaining products to 17.

A known method of producing ultrafine-grained aluminum alloy, the closest to the claimed and adopted as a prototype, including intense plastic deformation carried out with a true accumulated deformation e≥4 at a temperature not exceeding 300 ° C, and artificial aging at a temperature of 100-180 ° C with a holding time 0.5-24 hours to obtain a structure with an average grain size of 400-1000 nm. The alloy contains nanoscale precipitation of particles of the reinforcing phase Mg ₂ Si stable modification (β) having a globular shape and uniformly distributed in the volume of grains [patent RU 2478136, IPC C22F 1/05, publ. 03/27/2013].

The disadvantage of this method is the low strength and heat resistance, which does not provide the necessary properties for heat resistance.

The technical result of the invention is to increase the mechanical strength and heat resistance with satisfactory electrical conductivity of the aluminum alloy for electrical products due to its composition and structure, as well as the simplicity and efficiency of the method of its production.

The specified technical result is achieved in that a conductive ultrafine-grained aluminum alloy containing at least one alloying component selected from the group of rare-earth metals, iron and silicon, in accordance with the claimed invention, an ultrafine-grained aluminum alloy containing at least one alloying component, selected from the group of rare-earth metals RE = La, Ce, Nd, Pr, in the amount of 7.0-9.0 mass. %, as well as 0.05-0.1 mass. % iron, 0.05-0.1 mass. % silicon, aluminum - the rest, characterized by a structure with an average grain size of not more than 400 nm and particles of the eutectic phase Al ₁₁ RE ₃ , uniformly distributed over the grain volume and having a spherical shape, the size of which is not more than 50 nm, and the interparticle distance is not more than 150 nm.

, приложенном давлении 0.5-6.0 ГПа, в интервале гомологических температур 0.3-0.5Т_пл, и последующий отжиг в температурном интервале 280-400°C продолжительностью не менее 1 часа.In addition, the specified technical result is achieved due to the method of producing aluminum alloy, including intensive plastic deformation, carried out with the value of the true accumulated deformation

applied pressure of 0.5-6.0 GPa, in the range of homologous temperatures 0.3-0.5T _pl , and subsequent annealing in the temperature range of 280-400 ° C for at least 1 hour.

In addition, this technical result is achieved due to the fact that intense plastic deformation is carried out by one of the known methods: either torsion under high pressure, or equal channel angular pressing, or equal channel angular pressing in parallel channels, or continuous angular pressing.

The technical result is achieved due to the following.

Rare earth metals (RE) are known to increase the strength of aluminum. In addition, since RE is practically insoluble in aluminum [Drits M.E., Kadaner E.S., N.D. Shoah. Solubility of rare-earth metals in aluminum in the solid state // Izv. USSR Academy of Sciences, Metals, No. 1, (1967). from. 219-223], alloying them with aluminum to a much lesser extent reduces its electrical conductivity than other known alloying elements.

It is known that the introduction of RE in aluminum up to 10 wt. % contributes to a significant increase in its heat resistance to a temperature of 250 ° C [Lee Y., Fujimura N., Higashi K., Ito T., A candidate for interconnection material; Al-Y alloy thin films, Mater. letters 10, (1991) R. 344-347].

The inventive alloy is obtained using intense plastic deformation carried out under the specified processing conditions.

. [Р.З. Валиев, И.В. Александров, Объемные наноструктурные металлические материалы. - М.: ИКЦ «Академкнига», 2007 - 308 с. (стр. 322-328)].It is known that the formation of an UFG structure in metals and alloys requires the use of intense plastic deformation (IPD), while the deformation must be carried out in the range of homological temperatures 0.3 ... 0.5T _pl , the applied pressure must be up to 6 GPa, and the true accumulated deformation must reach

. [R.Z. Valiev, I.V. Aleksandrov, Volumetric nanostructured metallic materials. - M.: IKC "Akademkniga", 2007 - 308 p. (p. 322-328)].

In accordance with the claimed invention, after SPD, annealing is carried out in the temperature range of 280-400 ° C, which leads to further evolution of the structure obtained after SPD. As a result of annealing, internal stresses in the formed structure are removed and grain size is stabilized, which ensures the achievement of the necessary combination of strength and electrical conductivity of the material, and also provides the necessary level of its heat resistance.

Simultaneously with the formation of the UFG structure during SPD in aluminum alloys, grinding to a nanoscale level and spheroidization of particles of the eutectic phase Al ₁₁ RE ₃ occur. The grinding process of intermetallic particles in the IPD process is much more intensive than with traditional methods of deformation processing [A. Ma, M. Takagi, N. Saito et al., Tensile properties of an Al-11 mass% Si alloy at elevated temperatures processed by rotary-die equal-channel angular pressing, Materials Science and Engineering, A 408 (2005), p . 147-153].

It is known that the formation of an UFG structure with a grain size of less than 1000 nm during SPD leads to a significant increase in the mechanical strength of aluminum alloys (1.5-2 times) without a noticeable decrease in their electrical conductivity (with a grain size of about 400 nm, the electrical conductivity decreases by no more than 15 %) [X. Sauvage, E.V. Bobruk, M.Yu. Murashkin, Y. Nasedkina, N.A. Enikeev, R.Z. Valiev, Optimization of electrical conductivity and strength combination by structure design at the nanoscale in Al-Mg-Si alloys, Acta Materialia, vol. 98, (2015), p. 355-366]. This is due to the high ability of grain boundaries to harden aluminum alloys and their weak effect, with grain in the size range 1000 ... 200 nm, on the scattering of conduction electrons.

It is known that nanosized particles uniformly located in an aluminum matrix effectively strengthen aluminum without significantly affecting its electrical conductivity. They also contribute to increasing the thermal stability of the UFG structure and, accordingly, maintaining mechanical strength after exposure to high temperatures.

Structural changes in aluminum alloys are implemented by the proposed processing method, subject to the specified conditions for its implementation.

In general, the formation of the UFG structure described above in an aluminum alloy of the Al-RE system in the proposed combination of features of the invention leads to a simultaneous increase in their mechanical strength and heat resistance while maintaining satisfactory electrical conductivity in comparison with other aluminum alloys used in electrical products.

The invention is illustrated by drawings, where:

in FIG. 1 - shows a General view of the UFG structure of the alloy, the arrows indicate grains with a size of not more than 400 nm, formed in the alloy according to the claimed method;

in FIG. 2 - nanoscale particles of the eutectic phase Al ₁₁ RE ₃ having a spherical shape and evenly distributed in the volume of grains, arrows indicate grains with a size of not more than 400 nm, and particles of the intermetallic phase located inside it (indicated by arrows).

в интервале гомологических температур 0.3-0.5Т_пл, приложенном давлении 0.5-6.0 ГПа, с последующим отжигом в температурном интервале 280…400°C продолжительностью не менее 1 часа.Ultrafine-grained aluminum alloy is obtained by intensive plastic deformation carried out with true accumulated deformation

in the range of homological temperatures 0.3-0.5T _pl , applied pressure 0.5-6.0 GPa, followed by annealing in the temperature range 280 ... 400 ° C for at least 1 hour.

To form an UFG structure with an average grain size of not more than 400 nm, an initial alloy billet is used with at least one alloying component selected from the group of rare-earth metals (La, Ce, Nd, Pr) in an amount of 7.0–9.0 mass. %, as well as 0.05-0.1 iron, 0.05-0.1 silicon, aluminum - the rest.

в интервале гомологических температур 0.3-0.5Т_пл., и приложенном давлении 0.5-6.0 ГПа. ИПД можно осуществлять кручением или равноканальным угловым прессованием, или равноканальным угловым прессованием в параллельных каналах, или непрерывным угловым прессованием. На данном этапе происходит измельчение микроструктуры в объеме заготовки без изменения ее размеров. В результате эволюции структуры в процессе ИПД в алюминиевом сплаве формируется однородная УМЗ структура со средним размером зерна не более 400 нм. Одновременно с формированием УМЗ структуры в процессе ИПД происходит дробление и сфероидизация частиц эвтектической фазы, в результате чего в алюминиевой матрице они равномерно расположены в объеме зерен. Нанометрический размер частиц и их равномерное распределение обеспечивает дополнительный прирост прочности и заданную термостойкость материала.At the first stage, the initial billet is subjected to IPD processing with true accumulated deformation

in the range of homological temperatures of 0.3-0.5T _square , and an applied pressure of 0.5-6.0 GPa. SPD can be carried out by torsion or equal channel angular pressing, or equal channel angular pressing in parallel channels, or continuous angular pressing. At this stage, the microstructure is crushed in the bulk of the workpiece without changing its size. As a result of the evolution of the structure during the SPD process, a homogeneous UFG structure with an average grain size of no more than 400 nm is formed in an aluminum alloy. Simultaneously with the formation of the UFG structure in the SPD process, the particles of the eutectic phase are crushed and spheroidized, as a result of which they are uniformly located in the grain volume in the aluminum matrix. Nanometric particle size and their uniform distribution provides an additional increase in strength and a given heat resistance of the material.

At the second stage of UFG, the billet is subjected to heat treatment — annealing in the temperature range of 280–400 ° C for a duration of at least 1 hour, as a result of which grain size is stabilized and the necessary electrical conductivity of the alloy is ensured.

An example embodiment of the invention.

. Затем одну деформированную заготовку извлекли из инструмента/оснастки для проведения ИПД и подвергли термической обработке - отжигу в течение 1 часа при температуре 280°C; другую заготовку после ИПД подвергли отжигу при 400°С.First, a melt was prepared in an induction furnace made of primary aluminum and rare-earth metals. Then, 2 cast alloy billets with a content of 5.5 wt.% Ce, 3.0 wt.% La, 0.2S (Fe + Si) were obtained in the mold, the rest was aluminum, in the form of rods with a diameter of 20 mm. From cast rods, blanks were made in the form of a disk with a diameter of 20 mm and a thickness of 2 mm and subjected to intense plastic torsion deformation (IPDK) at room temperature with an applied pressure of 6 GPa, to the true accumulated deformation

. Then one deformed workpiece was removed from the tool / tool for SPD and subjected to heat treatment - annealing for 1 hour at a temperature of 280 ° C; another blank after SPD was annealed at 400 ° C.

Samples for studying the microstructure, mechanical properties, and electrical conductivity were made from the obtained blanks.

The microstructure was analyzed by transmission electron microscopy using a Jeol JEM 2100 microscope.

Mechanical testing of the samples was carried out in accordance with the requirements of GOST 1497-84. The electrical conductivity of the samples was determined in accordance with the requirements of GOST 27333-87.

The obtained ultrafine-grained structure in the alloy preform (Fig. 1), which was formed during the implementation of the proposed processing method, has an average grain size in the range of 210-400 nm. Along with ultrafine grains in the structure are observed nanoscale particles of the eutectic phase Al ₁₁ RE ₃ (Fig. 2), having a spherical shape and an average size of 45 nm, uniformly distributed over the grain size of the aluminum matrix. The distance between nanoscale particles is 75 nm.

Table 1 presents the results of mechanical tests and measurements of the electrical conductivity of the workpieces after processing them according to the proposed method, as well as the properties of known analogues.

Table 1 also shows the mechanical properties and conductivity values of the workpieces obtained by the proposed method after evaluating the level of their heat resistance, namely, after annealing for 400 hours at a temperature of 310 ° C, in accordance with the requirements of the international standard IEC 62004. 2007.

As can be seen from the table, the aluminum alloy obtained by the proposed processing method, in comparison with known analogues has higher strength and heat resistance, as well as satisfactory electrical conductivity.

The technical and economic efficiency of the claimed invention, as shown by the results of testing, consists in the possibility of obtaining an aluminum alloy having increased strength and heat resistance while maintaining electrical conductivity using a simple and economical method. The use of the claimed high-strength and heat-resistant aluminum alloy will expand the national market of conductors with special properties for the production of electrotechnical products operating at high mechanical stress and experiencing high temperatures during operation, and the introduction of such a high-strength and heat-resistant aluminum alloy will increase the reliability and service life of electrical products and power networks, as well as reduce the cost of their maintenance, h of the claimed invention can be attributed to import substitution technologies.

Bibliography

1. Patent EP0787811, IPC С22С 21/00, publ. 06/08/1997,

2. Patent RU2492258, IPC C22C 21/00, publ. 09/10/2013,

3. Patent RU2344187, IPC С22С 1/02, publ. 01/20/2009,

4. Patent RU 2478136, IPC C22F 1/05, publ. 03/27/2013 (prototype),

5. M.E. Drits, E.S. Kadaner, N.D. Shoah. The solubility of rare earth metals in aluminum in the solid state. Izv. USSR Academy of Sciences, Metals, No. 1, (1967), p. 219-223.

6. Y. Lee, N. Fujimura, K. Higashi, T. Ito. A candidate for interconnection material: Al-Y alloy thin films. Mater, letters 10, (1991), p. 344-347.

7. P. Z. Valiev, I.V. Aleksandrov, Volumetric nanostructured metallic materials. - M.: IKC "Akademkniga", 2007 - 308 p. (p. 322-328).

8. A. Ma, M. Takagi, N. Saito et al., Tensile properties of an Al-11 mass% Si alloy at elevated temperatures processed by rotary-die equal-channel angular pressing. Materials Science and Engineering A, 408 (2005), p. 147-153.

9.X. Sauvage, E.V. Bobruk, M.Yu. Murashkin, Y. Nasedkina, N.A. Enikeev, R.Z. Valiev. Optimization of electrical conductivity and strength combination by structure design at the nanoscale in Al-Mg-Si alloys. Acta Materialia, Vol. 98 (2015), p. 355-366.

Claims (5)

1. Conducting ultrafine-grained aluminum alloy containing at least one alloying component selected from the group of rare-earth metals, iron and silicon, characterized in that at least one alloying component is selected from the group of rare-earth elements (RE) containing La, Ce, Nd and Pr, with the following content of components, wt.%: at least one alloying component selected from the group La, Ce, Nd, Pr 7.0-9.0 iron 0.05-0.1 silicon 0.05-0.1 aluminum rest, the alloy has a structure with an average grain size of not more than 400 nm and particles of the eutectic phase Al ₁₁ RE ₃ , which are uniformly distributed over the grain volume and have a spherical shape with a size of not more than 50 nm, and the interparticle distance is not more than 150 nm. 2. A method of producing a conductive ultrafine-grained aluminum alloy according to claim 1, including deformation and subsequent heat treatment, the deformation is carried out with a true cumulative degree of deformation e≥4 by the method of intense plastic deformation at a pressure of 0.5-6.0 GPa in the range of homological temperatures 0.3-0.5T _pl , and subsequent heat treatment is carried out by annealing in the temperature range of 280-400 ° C for a duration of at least 1 hour. 3. The method according to p. 2, characterized in that the intense plastic deformation is carried out by the method of torsion under pressure, or equal channel angular pressing, or equal channel angular pressing in parallel channels, or continuous angular pressing.

Images