RU2464143C1 - Amorphous copper-based strip solder - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to soldering, particularly, to development of solder optimum shape, release and composition used in soldering tungsten and its alloys with copper and its alloys, for example, energy-intensive assemblies on nuclear power engineering. Proposed solder represents a flexible tape with amorphous structure from copper-based alloy containing in wt %: titanium - 25-31, beryllium - 0.1-3, copper making the rest. Said flexible tape features width of 10-40 mm and thickness of 40-50 mcm and unlimited length. It is made by superfast quenching at the rate of 10⁴-10⁶ deg. C/s to produce amorphous structure of alloy.

EFFECT: higher quality and thermo mechanical properties.

4 cl, 3 tbl, 10 dwg

Description

The invention relates to soldering, to the development of an optimal form for the release of solder used when soldering products from tungsten and its alloys with products from copper and its alloys, and can find application, for example, in the manufacture of energy-intensive units for nuclear and thermonuclear energy, in particular in the implementation the project of the International Thermonuclear Experimental Reactor (ITER).

One of the most energy-intensive units in the ITER fusion reactor is a divertor system. A divertor is a device designed to unload the first wall of the reactor chamber from direct exposure to plasma. The main purpose of the divertor is to ensure the utilization of the energy of charged particles leaving the main plasma, the pumping of neutral gas and helium ash and the control of impurities. The design of the divertor consists of the facing material of the first wall facing the plasma connected to the heat sink base. During the operation of the reactor, the divertor materials are subjected to powerful heat and particle fluxes of neutrons, hydrogen ions, deuterium, helium, atomized atoms of materials, etc. Energy loads on the divertor plates, in the event of a plasma cord breakdown, can reach values of 5-10 MW / m ² stationary mode and even higher loads corresponding to pulsed events, which causes significant temperature gradients and thermal stresses of structural elements. Neutron irradiation, in addition to changing the properties of the materials being joined, can lead to a deterioration in the properties of compounds due to a sharp increase in diffusion processes and to an additional increase in stresses in the structure due to uneven swelling of the materials.

The main mode of operation of the divertor is assumed to be a mode with semi-detached plasma, the temperature of which is tens of electron-volts. The energy of most particles incident on the receiving plates of the divertor is below the sputtering threshold of tungsten (~ 180 eV for deuterium ions); therefore, its erosion will occur only when plasma breaks. This circumstance, along with the remoteness of the divertor volume from the main plasma, high melting point, allows the use of tungsten for facing the divertor.

As shown in figure 1, as the divertor material facing the plasma, a carbon material (1) was selected for facing in the separatrix region and tungsten (2) in the rest of it. Bronze (3), an alloy based on copper having high mechanical and thermal properties, was chosen as a massive base. As a technology for connecting the lining with the heat sink base, soldering is used.

When soldering parts from these heterogeneous materials, it is necessary to consider:

- the degree of difference in their properties: temperature coefficients of linear expansion (CTE), thermal conductivity, melting point;

- wettability characteristics of various solders;

- the possibility and conditions for the formation of intermetallic layers.

The most difficult problem in obtaining a brazed joint of dissimilar materials is the significant difference in the thermal expansion coefficients (CTE). Table 1 shows the KTP and other physicomechanical properties of tungsten and copper, as divertor materials, the difference of which during the thermal soldering cycle can lead to the formation and growth of cracks in the joint.

The main requirements for energy-intensive bimetallic compounds of ITER are the following:

- reliable mechanical contact;

- high heat resistance and thermal conductivity of the compounds;

- manufacturability and the possibility of repair;

- high resistance to cyclic temperature changes due to the pulsed mode of operation of the reactor in the first period of operation;

- radiation resistance of the compound under neutron and ion fluxes.

The difficulty of combining tungsten with copper alloys is also due to the fact that tungsten and copper do not interact in either solid or liquid state, in addition, the strength of a number of copper alloys, such as bronzes, is due to the presence of dispersion hardening hardening phases in their structure, the stability of which does not should deteriorate in the thermal soldering cycle.

At room temperature, tungsten has high chemical resistance, but when heated above 400 ° C it is oxidized to form tungsten trioxide WO ₃ . Therefore, before soldering, the tungsten surface must be thoroughly cleaned mechanically or by etching in acids.

Tungsten is soldered in protective and reducing environments, as well as in vacuum, as this produces the most dense seams.

In the work “Problems of Obtaining Divertor Assemblies of a Thermonuclear Fusion Reactor Using Soldering” (S.V. Maksimova, V.F. Khorunov, V.R. Barabash. “Welding Production”. 1994, No. 5. P.6-9) for solders W with dispersion hardened bronze BrKhTsrMg used solders systems Cu-Ag, Cu-Ti, Cu-Mn and pure titanium. The soldering was carried out by radiation heating and the passage of current in a vacuum of 10 ^-3 Pa with the application of a pressure of 1 MPa due to the need to obtain long seams with a minimum number of defects in relation to the manufacture of the divertor. Solders were used in the form of tapes (foil) 0.02-0.3 mm thick. With Cu-Ti solder, a contact-reactive vacuum brazing method was used, based on the interaction (upon heating) of a titanium foil with copper, the result of which is the formation of an adhesive-active solder that wetts tungsten well.

Another analogue of the claimed solder is a copper based solder, which contains components in the following ratio (in wt.%):

Titanium 36-51 Beryllium 0.5-12 Copper rest

(USSR author's certificate 470382).

Solder allows you to get a brazed joint of ceramics with metal, well wetts the surface of the solder, however, it is a brittle, non-deformable alloy, which in some cases makes it difficult to use. In addition, there is no information on the use of this solder for brazing tungsten.

Recently, amorphous and microcrystalline tape solders 20-80 microns thick, obtained by ultrafast quenching from liquid metal melt, have been widely used. Due to their unique properties, such solders are used for soldering copper and copper alloys, nickel and its alloys, corrosion-resistant steels, titanium and its alloys, zirconium, beryllium, refractory metals, hard alloys, oxide ceramics, graphite, etc. ("Application amorphous tape solder STEMET 1101 for flux-free brazing of copper. "Abstracts. International scientific and practical conference on the use of science and technology in urban development, dedicated to the 850th anniversary of the founding of Moscow, Moscow: Engineer, 1996, part 1, p. 282-283).

The closest analogue of the claimed solder is a solder based on copper of the STEMET 1204 brand, containing components in the following ratio: titanium 28 wt.%, Copper - the rest (see http://www.stemet.ru/s1203).

The specified solder is made in the form of foil or tape according to the technology of rapid solidification of the melt on a rotating drum-cooler and refers to the type of solders obtained in an amorphous structural state. According to the information on the specified site, STEMET 1204 solder is intended for brazing products from oxide and nitride ceramics, as well as ceramics with metals, such as copper with Al ₂ O ₃ ceramics. The melting point of STEMET 1204 solder is 875 ° C. STEMET 1204 solder is produced in the form of an amorphous flexible tape with a thickness of 0.025-0.06 mm and a width of 5-50 mm. However, in the prior art there is no information on the use of STEMET 1204 solder for brazing tungsten or its alloys.

To date, the physicochemical and technological features of soldering with quick-hardened solders (BZP) have not been sufficiently studied. There is the possibility of optimizing the composition and development of new tape BZP, improving the properties of solders and technological soldering conditions.

The invention is aimed at solving the problem of developing new tape amorphous (quick-quenched) solders for brazing structural elements of power plants, in particular for brazing a tungsten cladding to the bronze base of the diverter of a thermonuclear reactor.

The technical result is a decrease in temperature with an increase in the quality of soldering, the formation of a solder joint without intermetallic compounds in the absence of non-solders, pores and other defects in the connection, resulting in an increase in the thermomechanical characteristics of soldered joints of parts based on copper and based on tungsten.

Another technical result is to increase the operational characteristics of the solder by ensuring the stability of the amorphous structure, a homogeneous phase composition, high diffusion, adhesive and capillary activity of its components.

When developing the invention, it was unexpectedly discovered that the introduction of beryllium into the claimed solder makes it possible to solder copper alloys such as dispersion hardened bronzes with tungsten, without reducing their strength, due to the fact that the lower temperature of the solder allows you to completely save their dispersion hardening.

The chemical and phase homogeneity of the components of the amorphous solder ensures uniform melting of the solder throughout the volume, the formation of a continuous and uniform solder joint during solidification. In addition, the increased diffusion activity of the solder leads to better wetting, faster diffusion of the alloying elements of the solder into the base metal, and to the complete absence of intermetallic compounds in the brazed joint.

To solve this problem, an amorphous tape solder for brazing tungsten and its alloys with copper and its alloys, made in the form of a flexible tape of an amorphous structure from an alloy based on copper containing titanium, is claimed. The solder additionally contains beryllium in the following ratio of components (in wt.%):

Titanium 25-31

Beryllium 0.1-3

Copper is the rest.

The additional introduction of beryllium made it possible to significantly stabilize the amorphous structure of the solder, reduce the melting point, and improve the mechanical properties of the metal strip of solder.

The claimed amorphous copper-based tape solder is made in the form of a flexible tape with a width of 10-40 mm, a thickness of 40-50 microns of unlimited length. The solder is made by ultrafast quenching from a liquid metal melt at a rate of 10 ⁴ -10 ⁶ ° C / s to obtain an amorphous alloy structure.

The developed amorphous tape solder is made with the possibility of soldering the tungsten cladding to the bronze base of the fusion reactor divertor (TNR).

The invention is illustrated in figures 1-10.

Figure 1 shows a fragment of a section of a divertor made using the claimed solder.

Figure 2 shows a diagram of the installation "Crystal-702" for producing alloys-solders by ultrafast hardening.

Figure 3 shows the manufactured amorphous tape solder.

Figure 4 shows the soldering using the claimed solder.

Figure 5 shows a study of the heat resistance of the finished solder joint.

Figure 6 shows a three-point bend test of soldered W-BrHCr samples.

Figure 7 shows photographs of the microstructure of the soldered connection of tungsten - bronze BrNHK (left - bronze, right - tungsten), obtained at different temperatures and holding times.

On Fig shows photographs of the surface of the soldering region after irradiation with high-temperature plasma.

Figures 9 and 10 are graphs illustrating the results of mechanical tests by the three-point bending method before and after irradiation of soldered samples.

Since the TNR diverter is a device operated under high vacuum (10 ^-6 ... 10 ^-7 Pa), then the materials included in its composition should not contain elements with high vapor pressure.

From the temperature dependences of the vapor pressure of chemical elements in vacuum on the temperature, the elements can be distributed as follows according to their volatility: Cr, Ge, Si, Cu, Sn, Ni, Ag, Ga, Mn, In, Pb, Mg, Zn, Cd , P. Elements such as P, Cd, Zn, Mg and Pb have high vapor pressures, and the use of these elements in the design of the divertor is highly undesirable. Solders containing silver are also not applicable to the operating conditions of TNR due to the formation of volatile cadmium under the influence of neutron irradiation. The remaining elements have satisfactory volatile characteristics and their use as alloying additives in solders based on copper is permissible. However, solders from the indicated set of elements are either obtained only in the form of powders, or they have too high melting points, wide melting intervals, or complex non-uniform seams are formed during the soldering process, which significantly affect the heat transfer from the facing material to the heat-transfer bronze.

When choosing alloying elements, their interaction was taken into account not only with copper, but also with tungsten. It has been established that it is most expedient to alloy the solder with elements that do not form intermetallic compounds with tungsten, but which form a series of solid solutions with it, in addition, alloying elements must be active to ensure the best adhesion.

When developing a solder based on copper, which is prone to amorphization, among alloying elements forming a eutectic with copper at a low melting point, Ti was selected from all possible elements. From the state diagram of the Cu-Ti alloy system, it can be seen that the Cu-Ti system contains several eutectics. The most fusible eutectic (T _pl. = 887 ° C) is an alloy with a content of 28% Ti (wt.), Consisting of Cu ₇ Ti ₃ (T _pl. = 903 ° C) and Cu ₇ Ti (T _pl. = 908 ° C). Thus, in the composition of the developed solder, taking into account the error of its manufacture, the optimal titanium content is in the range of 25-31 wt.%.

From the state diagram of Ti-W alloy systems, it was found that a continuous series of solid solutions is formed between βTi and W. A monotectoid transformation occurs at the 740 ° C side of titanium, accompanied by the separation of the solid solution (βTi, W) into solid solutions β ₁ and β ₂ .

The inventors have proposed alloying of solder with beryllium, even a low content of which leads to a significant decrease in the melting point of the alloy.

The solubility of Be in Cu at a eutectoid temperature of 600 ° C is 10 at.%, And at a retelectic temperature of 866 ° C - 16.5 at.%. In addition to solid solutions based on pure metals, the following phases exist in the system: β (Cu ₂ Be), γ (CuBe), and δ (Cu ₃ Be + Cu ₂ Be). When the content of Be in the amount of 2.6% (wt.) The melting point of copper decreases by 120 ° C and is about 960 ° C.

In order to prevent the formation of chemical compounds with beryllium in the soldered joint, taking into account the low solubility of Be in Ti, the Cu system was optimally doped with 28% Ti in the amount of beryllium in the amount of 1 wt.%. Taking into account the error, deviation from the optimum beryllium content in the solder is allowed in the range of not more than 0.1 ÷ 3.0 wt.%.

Ingots were smelted in an MIFI-9 arc furnace in argon medium.

The MIFI-9 arc furnace contains a tungsten non-consumable electrode and allows the resulting melt to be mixed with an arc to evenly distribute alloying components throughout the ingot volume. The melting process is carried out according to the principle of auto-crucible: the molten sample is separated from the copper hearth, cooled by water, a thin solid layer of sample material.

As the charge materials used:

- titanium metal, iodide (TU 48-4-282-86);

- hot-pressed beryllium with a purity of 99.98%;

- copper MO (GOST 546-79).

To simplify the process of uniform distribution of alloying components in the ingot, preliminarily melted Ti - 5 wt.% Be alloy was used as charge materials. The mixture was loaded into a water-cooled under and subjected to fusion. After each remelting, the ingot was turned over and the transfer procedure was repeated.

The chemical composition of the obtained ingots was determined by X-ray microanalysis using an INCA 350 x-act energy dispersive spectrometer (Oxford Instruments).

The production of alloys-solders in the form of flexible tapes was carried out by the method of ultrafast hardening on a rotating disk-cooler on the modernized Crystal-702 installation. This setup allows to obtain alloys-solders in an amorphous (nanostructured) or nanocrystalline state by quenching from melt with cooling rates of ~ 10 ⁴ -10 ⁶ K / s in the form of tapes with a thickness of 20 ... 100 microns and a width of 1.2 to 55 mm. The maximum amount of tape obtained per one technological cycle was (0.3 ... 0.5) kg. The installation diagram "Crystal-702" is presented in figure 2.

At the Crystal-702 installation, the solders of the Cu - 28.0 wt.% Ti compositions (STEMET 1204 prototype) and the beryllium-modified Cu solder - 28.0 wt.% Ti - 1.0 wt.% Be were obtained from the melted ingots. in the form of tapes 20 mm wide and 50 microns thick.

The Crystal-702 installation includes a control panel 4; high frequency generator 5; inert gas cylinder 6; gas inlet system 7; control device type 8; potentiometer 9; the housing of the vacuum chamber 10; quartz crucible 11; thermocouple 12; high frequency inductor 13; melt 14; quenching copper disk 15; tape stripper 16; vacuum system 17 with a VT-2A thermocouple vacuum gauge; vacuum unit 18; tape receiver 19; (rapidly quenched) amorphous solder tape 20.

Preliminarily melted in the MIFI-9 arc furnace, the solder alloy ingots were placed in a quartz crucible 11 having a nozzle. The crucible 11 with ingots was placed inside the high-frequency inductor 13. By high-frequency currents using the high-frequency generator 5 and inductor 13, the ingots were heated to the required temperature above the melting point of the alloy. The melt of solder 14 under the influence of ejection pressure of an inert helium gas supplied through a gas inlet system 7 was supplied through a nozzle of a crucible 11 to a rapidly rotating quenching copper disk 15 with a width of 50 mm and a diameter of 300 mm (12). In this case, the surface area of the melt in contact with the disk increased many times and, accordingly, a high rate of heat removal from the melt to the disk was achieved. Almost instant solidification of the melt occurred. The hardened solder melt is separated from the disk under the influence of thermal stresses and centrifugal force or cut off using a stripper 16. The resulting solder tape 20 fell into the tape receiver 19. The process of manufacturing rapidly quenched amorphous ribbons was carried out in a controlled helium gas medium created using a vacuum system 17 and an admission system inert gas 7.

In the process of manufacturing rapidly quenched amorphous tapes, a number of technological parameters were regulated, such as the heating rate, the temperature of the melt casting process, the excess gas pressure in the crucible, the speed of the quenching disk, the nozzle-disk distance, the gas medium and its pressure, the width of the nozzle, and the mass of the melt ingot and others. The width of the solder ribbon was controlled by the length of the crucible nozzle. The thickness of the solder ribbon was changed by a number of parameters: excess gas pressure during injection of the melt, speed of rotation of the quenching disk, melt viscosity, casting temperature, nozzle-disk distance, etc.

The obtained amorphous tape solder is shown in figure 3.

Determination of temperature characteristics: crystallization temperature from an amorphous state, melting temperature, and crystallization temperature of the obtained alloys-solders was carried out on a Netzsch STA 409 CD differential thermal analyzer with a heating and cooling rate of 20 ° C / min in a helium atmosphere.

The exothermic crystallization peak in the temperature range 425 - 435 ° C for the Cu alloy - 28.0 wt.% Ti - 1.0 wt.% Be, obtained on the curve of high-temperature differential thermal analysis (VDTA), indicates that the alloy has amorphous structure.

It should be noted that the beryllium-modified alloy Cu - 28.0 wt.% Ti - 1.0 wt.% Be has a thermostable amorphous structure, as evidenced by the high temperature of its crystallization.

The solidus and liquidus temperatures of the claimed solder were determined by heating and cooling the resulting alloy at a rate of 20 ° C / min. For Cu alloy - 28.0 wt.% Ti - 1.0 wt.% Be - Tsolid (when heated) = 840 ° C, Tsolid (when cooled) = 830 ° C, Tliquid (when heated) = 875 ° C, Tliquid (when cooled) = 865 ° C.

Before carrying out the brazing process using the obtained solder, preliminary preparation of samples from copper-based alloys and from tungsten was carried out. For soldering, samples were cut from monocrystalline and polycrystalline tungsten with a diameter of 10 mm and a thickness of 2 mm and from copper alloys 15 × 15 × 10 mm. For carrying out reactor and mechanical tests, samples were cut from polycrystalline tungsten 25 × 5 × 1.5 mm, from BrKhCr 40 × 25 × 4.5 mm. The surface of the samples was subjected to grinding and polishing; in the case of tungsten, it was electropolished (to relieve internal stresses).

The chemical composition and properties of soldered materials are presented in table 2.

For soldering the samples, a vacuum furnace with resistive heating СШВ-1.2.5 / 25М-04 was used, which allows soldering in a vacuum of 1.3 × 10 ^-3 Pa. Tungsten rods and a graphite plate were used as heaters.

When carrying out soldering, as shown in figure 4, the solder 21 was laid in one layer on the polished side of Cu sample 22 in the form of pieces of tape according to the size of the materials to be soldered and each piece was fixed using spot welding. Then, W sample 23 was placed on the surface of the solder with the polished side to the solder and the assembly was fixed with a load of 24 with the assembly placed in a tantalum conductor 25 on the substrate 26 so that a pressure of 0.25-0.5 kgf / cm was provided during the thermal soldering cycle ² .

Monocrystalline tungsten was used as soldered materials, as a candidate material for facing the ITER divertor and various types of bronze: BrNHK, BrHTsr. The compositions of copper alloys are given in table.2. The greatest practical interest is the soldering of bronze BrHTsr, since this alloy meets all the requirements for ITER materials. BrNKhK alloy was investigated for comparative purposes.

Soldering a series of samples was carried out in vacuum with a residual pressure of no worse than 10 ^-5 mm Hg. with a heating rate of (15 ÷ 20) ° C / min to the soldering temperature at which isothermal holding was carried out. Then the temperature was lowered to room temperature at a rate of (15 ÷ 20) ° C / min. The soldering temperature and the exposure time of the test samples are shown in table 3.

Figure 7 shows the microstructure of soldered joints of single crystal tungsten - BrNKhK, solder Cu - 28.0 wt.% Ti - 1.0 wt.% Be (left - bronze, right - tungsten): A) T = 900 ° C, exposure 2 minutes; B) T = 950 ° C, holding for 2 minutes; C) T = 950 ° C, holding 30 min.

In the study of the microstructures of soldered joints, it was found that with an increase in the holding time during soldering, titanium more intensively dissolves in the bronze copper matrix and decreases its concentration in the brazed joint. However, during the interaction of the molten solder and bronze, a certain dissolution of the latter occurs, as a result of which alloying elements Cr, Ni, and Si fall into the melt. From the results of X-ray microspectral analysis, a significant presence of silicon was established. Faceted discharge was found in the seam area. An increase in temperature and soldering holding time is accompanied by a decrease in the concentration of these precipitates and an increase in their size. The content of silicon and titanium in these precipitates reaches 15-23 wt.% And 33-64 wt.%, Respectively. Thus, in these formations, the ratio of silicon to titanium can be represented as 1: 3 and 1: 4. From the analysis of the Ti-Si state diagram, this concentration ratio corresponds to the homogeneity region of the Ti ₅ Si ₃ intermetallic compound with a maximum melting point of 2130 ° C and increased hardness. Such a process inhibits the diffusion of titanium into a bronze matrix.

Along with this, a slight dissolution of the tungsten single crystal occurs (its content in the weld reaches 4-5 wt.%). No significant erosion of single-crystal tungsten was detected (erosion depth of the order of 2-3 microns).

Lowering the soldering temperature by the declared solder to 900 ° C leads to the fact that titanium, even after holding for 2 minutes, is intensively soluble in bronze, without any significant precipitation in the area of the soldered joint, more intense than at 950 ° C and holding for 30 minutes. The soldered seam itself has small dimensions (about 10 microns, with a solder thickness of 40 microns). This can be explained by the fact that at 900 ° C a slight dissolution of bronze occurs and, accordingly, the alloying elements of the bronze substrate transfer to the melt. Therefore, the titanium contained in the solder does not bind to the compounds and diffuses intensively into the bronze copper matrix.

From the results of microhardness measurements, a decrease in strength (microhardness) in brazed joints at a distance of about 80-100 μm from the interface between the soldered seam and tungsten by на7-15% of the microhardness of the bronze matrix was revealed. This is due to the fact that at high temperatures (950 ° C) and long exposure times in the surface layer of bronze, a change in the structural-phase state occurs, associated with erosion and dissolution of alloying elements in the solder melt. Near the boundary with tungsten, the microhardness increased by a factor of 2–2.5, which is associated with the formation of refractory solid titanium silicides.

Studies show that when soldering at 950 ° C, 30 min, the alloying elements of the solder are completely dissolved in the bronze copper matrix, which leads to the formation of a uniform soldered seam.

To conduct intra-reactor and mechanical tests in one technological soldering cycle, a soldered connection of polycrystalline tungsten 25 × 5 × 1.5 mm with bronze BrKhtsr 40 × 25 × 4.5 was obtained. Then this compound was cut into samples (4 mm wide in the transverse direction relative to tungsten).

The study of the heat resistance of soldered joints was carried out by irradiating soldered W-BrHCr samples with high-temperature pulsed deuterium plasma (VTIP) flows in a pulsed plasma device of the Desna-M Z-pinch type.

To study the heat resistance of the finished solder joint (tile model), it was cut approximately in half on a spark machine, polished and irradiated from the end, as shown in Fig. 5. The study of the heat resistance of soldered joints obtained at a temperature of 950 ° C for 30 min, solder Cu - 28.0 wt.% Ti - 1.0 wt.% Be, was carried out by irradiation with high-temperature deuterium pulsed plasma (VTIP) at a fixed specific power flow W = 5 MW / cm ² and the number of pulses N = 2 (pulse duration ~ 20 μs).

An analysis of the results showed that starting from the first pulses of the VTIP flows in the irradiation regimes at the transition from moderate to hard (W = 5 MW / cm ² ), the end surface of the brazed tungsten plate cracks and melts in all cases, regardless of the composition of the solder material and the substrate. In all cases, copper-based heat transfer material (substrate) (bronze) is subject to intense melting and boiling, as evidenced by the developed relief in the form of waves of solidified melt, drops, craters and pores.

The surface of the soldering area under irradiation behaves ambiguously. The solder layer on the brazed joints of tungsten with bronze BrHCr is not subject to cracking. The seam is uniform in length, the average thickness of the layer along the length of the soldered joint is about 20 μm (see Fig. 8).

When irradiating with the pulsed deuterium plasma flows the end surface of the soldered gradient joints of tungsten plates with a copper-based heat sink material in hard mode (W = 5 MW / cm ² ), it was found that the connection with single crystal tungsten with BrXCr bronze solder Cu - 28.0 wt.% Ti - 1.0 wt.% Be.

Tests of soldered W-BrHCr samples for three-point bending (see Fig. 6) were carried out both in the irradiated state and without it. The samples were irradiated at a temperature of 200 ° C with neutrons with an energy of more than 0.1 MeV for 5 ef. days., with a fluence of 1.8 · 10 ²⁰ n / cm ² .

In the process of testing soldered samples for three-point bending, photography was carried out. It was found that before and after irradiation, the nature of the destruction of the test samples does not change. In both cases, the fracture process started first from the fillet portion of the junction site, in which a crack was generated at an angle of 45 ° to the plane of the soldered seam and spread deep into the bronze. Then, in the process of increasing the load, another crack was formed in the tungsten body at an angle of 45 ° to the material interface, which propagated to the junction area. Then, the destruction spread along the tungsten – bronze interface. A further increase in load led to the deformation of bronze.

Based on the results, it can be concluded that with a three-point bend of the solder joint, fracture arises in the stress concentration zone (fillet portion of the solder joint), and with the development of plastic deformation of the bronze base, the crack propagates along the solder joint. The development of cracks along the brazed joint is accompanied by intense plastic deformation of the bronze. Based on this, it can be concluded that an increase in the yield strength as a result of neutron irradiation leads to an increase in the strength of the soldered joint as a whole.

Mechanical tests using the three-point bending method before and after irradiation (fluence 1.8 · 10 ²⁰ n / cm ² with neutron energy more than 0.1 MeV, at 200 ° C) showed that neutron irradiation leads to hardening of the soldered joint. During the irradiation process, the yield strength of the compound increases from 330 MPa to 540 MPa (see Figs. 9-10), and the tensile strength remains virtually unchanged at 600 MPa.

Thus, the example given in the description of the preparation of an amorphous strip solder of the composition Cu-28Ti-1Be (wt.%) And the preparation of a brazed joint of a single-crystal tungsten sample with BrHCr grade bronze showed that in the soldering zone of tungsten with copper there is an intensive dissolution of alloying elements of solder in copper the basis of the product, therefore, a soldered seam is formed without intermetallic compounds, nepropathy and pores.

The mechanical tests carried out before and after the neutron irradiation of tungsten-bronze compounds soldered by tape BZP based on copper showed a high level of mechanical properties of soldered joints.

The claimed solder is suitable for precision brazing of materials of modern technology: tungsten with copper alloys as applied to the fabrication of the divertor of the ITER fusion reactor.

Table 1. Mechanical and thermophysical properties of the materials to be joined (at 20 ° C) Alloys α, 10 ^-6 , K ^-1 E, GPa σ _V , MPa δ,% Poisson's ratio, ν W (99.9) polycrystalline 4.3 (5.0) 342-400 600-900 0-5 0.26-0.35 W (single crystal) * 4.3 390-420 960 2-18 0.24-0.26 Cu 16.8 110-130 200-240 fifty

Table 2. The chemical composition and properties of soldered materials Soldered material Chemical composition, wt.% Bronze BrNHK Cu - base (2.2 ... 2.8)% Ni, (0.5 ... 1.0)% Cr, (0.4 ... 0.8)% Si, <0.01% Pb, <0.08 % Sn, <0.1% Fe, <0.15% Zn Bronze BrHCr (CuCrZr) Cu - base, 0.6% Cr, 0.08% Zr, impurities <0.1% Tungsten single crystal TU 48-0531-220-80, crystal No. 119

Table 3. Tungsten Soldering Modes - Bronze Soldering mode, ° C 900 ° C, 2 min 920 ° C, 2 min 950 ° C, 2 min 950 ° C, 10 min 950 ° C, 30 min W-BrNHK
Cu - 28.0 wt.% Ti + + + + W-BrNHK
Cu - 28.0 wt.% Ti - 1.0 wt.% Be + + + W-BrHCR
Cu - 28.0 wt.% Ti + + W-BrHCR
Cu - 28.0 wt.% Ti - 1.0 wt.% Be + +

Claims (4)

1. Amorphous tape solder for brazing tungsten and its alloys with copper and its alloys, in particular with bronze, made in the form of a flexible tape with an amorphous structure from an alloy based on copper containing titanium, characterized in that it additionally contains beryllium in the following ratio components, wt.%:
Titanium 25-31
Beryllium 0.1-3
Copper rest 2. The solder according to claim 1, characterized in that it is made in the form of a flexible tape with an amorphous structure with a width of 10-40 mm and a thickness of 40-50 microns, while the amorphous structure of the alloy is obtained by ultrafast quenching from a liquid metal melt at a speed of 10 ⁴ - 10 ^6th hail. C / s 3. Amorphous tape solder for brazing tungsten and its alloys with copper and its alloys, made in the form of a flexible tape with an amorphous structure from an alloy based on copper containing titanium, characterized in that it additionally contains beryllium in the following ratio of components, wt.% :
Titanium 28.0
Beryllium 1.0
Copper rest 4. The solder according to claim 3, characterized in that it is used for brazing the tungsten cladding to the bronze base of the divertor of the thermonuclear reactor.

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