SU1478260A1 - Method for producing magnetostrictive materials - Google Patents

Abstract

The invention relates to the field of metallurgy, in particular to methods for producing magnetic materials with high magnetostriction values. A method is proposed for manufacturing materials based on intermetallic iron compounds with rare earth elements such as RFE ₂ . The aim of the invention is to increase the strength characteristics. The proposed method differs from the well-known fact that a casting of the composition R _{1 + X} FE _{2-X is made} (X≤0.3 with a higher content of rare-earth element than in the stoichiometric composition; before starting the heat treatment, a thin layer of metal M is created on the surface of the ingot forming a rare-earth element eutectic with a lower eutectic transformation temperature than the initial components, and the heat treatment mode is selected so that the metal M from the surface layer penetrates into the ingot volume mainly due to diffusion along the grain boundaries to form a grain space strengthening phase (presumably, M ₂ R). This enables changing the parameters X and thickness to create a surface layer to obtain materials with optimal MAGNETOELASTIC and mechanical properties, have higher strength than the materials of similar composition TYPE R _{1 + X} FE _2-X , WITHOUT A SIGNIFICANT REDUCTION OF MAGNETOELASTIC PARAMETERS. 2 TABLE.

Description

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The invention relates to metallurgy, in particular to methods for producing magnetic materials based on intermetallic compounds of the type RFe, where R is a rare-earth element with high magnetomechanical parameters.

The purpose of the invention is to increase the strength characteristics.

The method is carried out as follows.

A mixture of components of a given composition containing a rare earth element R and iron is melted in an electric arc furnace with a non-consumable electrode on a copper water-cooled hearth in an inert gas atmosphere, poured into a mold of a given shape and

annealed to obtain a given level of properties.

The proposed method differs from the known one in that the initial mixture of components with a higher content of rare-earth element is prepared than in the stoichiometric composition in such a way that after smelting, a casting of the composition RHXFe4 x is obtained. Before the start of heat treatment, a thin layer of metal M is formed on the surface of the casting, forming a eutectic with a lower-earth element with a lower eutectic transition temperature than in the initial mixture of components, and the heat treatment mode is selected so that the metal M from the surface layer penetrates deep into the material due to diffusion along the grain boundaries, forming a hardening phase in the material (presumably composition RM2).

As a result of heat treatment, a material consisting of RFeЈ phase grains with high magnetoelastic parameters is obtained, the adhesion strength of which is increased due to the formation of a hardening phase in intergranular regions.

The proposed method allows to obtain high-strength materials with a magnetostriction level of about 10.

The method was tested in the manufacture of a material based on the TbFe2 intermetallic compound using copper as a hardening additive. The initial mixture of composition Tbu Fei-x (X 0; 0.05; 0.10; 0.15; 0.20; 0.25; 0.30) is placed on the water-cooled copper under the chambers of an electric arc furnace with a non-consumable tungsten electrode. A cylindrical mold is used, the inner surface of which is lined with copper foil 50 μm thick so that it fits snugly to the surface. The inert atmosphere in the furnace is created by pumping with a forepump pump and sequential rinsing with argon three times. After a double electric arc remelting of the initial charge, the crystallized ingot is placed on a mold and melted using an electric arc for casting into a mold. In the interaction of the melt with copper foil on the surface of the ingot receive a thin layer of copper with the formation

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in the near-surface layer of the compounds of the Tb – Fe – Cu system.

The obtained ingots are annealed at 900 ° C for 30 minutes.

The properties of the materials obtained (A p are longitudinal magnetostrictions; Јt, are the residual deformations of the magnetomechanical hysteresis loopJ (fcjk T is the mechanical compressive strength $ G polcT — the mechanical tensile strength) are given in Table 1.

At a given thickness of the surface layer (copper 50 µm), the material properties increase with increasing parameter X. The low level of properties at small X is due to the fact that the volume of intergranular regions enriched in terbium is small, making it difficult for copper to diffuse from the surface layer into the material and form the intergranular strength of the hardening phase, and the formation of the surface layer reduces the magnetoelastic characteristics of the material.

At large values of X (0.25-0.3 and more), the mechanical strength does not deteriorate, but the volume of the TbFe2 phase decreases, which leads to a decrease in the magnetoelastic characteristics.

Thus, by changing the thickness of the deposited layer and the concentration of the components, it is possible to control the ratio of magnetoelastic and mechanical parameters, optimizing the characteristics of materials.

In tab. 2 compares the properties of the materials obtained by the proposed method, by the known method and by the eutectic hardening method.

From tab. 2, it can be seen that the proposed method allows to obtain materials with higher mechanical characteristics, while in materials of a similar composition in terms of R and Fe, hardening is achieved without a significant decrease in the magnetoelastic properties.

The proposed method can be used in the preparation of materials for magnetostrictive transducers and sensitive elements of memory pressure and acceleration sensors.

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55 claims

The method of obtaining magnetostrictive materials based on intermetallic compounds of iron with rare earth elements like RFez, including fusing the initial mixture of components in an inert gas atmosphere, casting the alloy into a mold

and subsequent annealing of the casting, characterized in that, in order to increase the strength characteristics,

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a stoichiometric composition of the land element; on the surface of the casting, a thin layer of metal M is formed, which forms a eutectic with a rare-earth element at a temperature lower than in the initial mixture of components, and annealing is performed at a temperature higher than the eutectic transition temperature

the casting is obtained with the content of rarely D-M systems.

Note

 A ,, is the longitudinal magnetostriction caused by the displacement of the domain boundaries at H = -1600 kA / m; Јh - residual deformation of MMG (at (Aczhvt 80 MPa); rast - tensile strength (before failure); - compressive strength (before destruction). All given numerical values of the parameters were obtained by averaging over three samples.

Table 1

table 2

Claims (1)

Claim A method of producing magnetostrictive materials based on inter5 metal compounds of iron with rare-earth elements of the type RFe _z , comprising fusing the initial mixture of components in an inert gas atmosphere, casting the alloy into a mold and subsequent annealing of the casting, so that, in order to increase the strength characteristics, the casting is obtained with a rare earth element with a stoichiometric composition; a thin layer of metal M is formed on the surface of the casting, forming a eutectic with a rare earth element at perature is lower than in the initial mixture of components, and annealing is carried out at a temperature above the eutectic temperature of the system transition RM. Table 1 * 1 0- 0.05 I 0.10 t ( 1 ------------------ 1 1 1 ΙΟΙ I »I I - I 1 Ln 1 eleven I 0.20 I 0.25 I 0.3- Note έ / y ‘‘ 160 180 220 410 420 405 400 When _Compressed = £ = 60 MPa ! „· 10’, cm 480 600 950 1050 1400 780 When Η = = 1600 kA / m MPa 7.0 - 26 60 90 - 105 T a blitz 2 Sample Sample Composition Hardening method cm Eg / Yu ' ⁶ θραοτ ’ MPa <^ * ατ 'AND ¹¹³ thirteen TbFe _a Famous 1680 420 4 - 5 100-150 4-6 ^Tb 1, l ^Fe 1. ₈ Eutectic 1080 400 20 - thirty 300 7-9 TH, _g Fe, _e Proposed 1060 600 100 - 150 > 500 (copper) Note. Ά, is the longitudinal magnetostriction due to the processes of the displacement of the domain walls at Н ^β 1600 kA / m; Е, is the MIG residual deformation (at (e _grit = 80 MPa); С> rasp “tensile strength (before fracture); - compressive strength (before fracture). All the numerical parameters given are obtained by averaging over three samples.