Preparation method of niobium-tungsten alloy

Abstract

The invention provides a niobium-tungsten alloy and a preparation method thereof. The preparation method comprises the following steps: 1) performing vacuum reduction sintering on a powder blank comprising niobium powder, first tungsten powder, first molybdenum powder and yttrium powder to obtain a niobium-tungsten-molybdenum alloy strip; (2) carrying out aluminothermic reaction on powder comprising niobium oxide, aluminum powder, second tungsten powder and second molybdenum powder to obtain a niobium-tungsten-molybdenum-aluminum alloy block; (3) the niobium-tungsten-molybdenum-aluminum alloy block is subjected to vacuum electron beam melting, and a niobium-tungsten-molybdenum alloy plate is obtained; 4) forming a smelting electrode by using the zirconium sheet niobium-tungsten-molybdenum alloy strip, the niobium-tungsten-molybdenum alloy plate and the niobium wire; and (5) the smelting electrode is subjected to vacuum electron beam smelting, and the niobium-tungsten alloy is obtained and comprises, by mass, 4.5%-5.5% of tungsten, 1.5%-2.5% of molybdenum, 1.4%-2.2% of zirconium, smaller than or equal to 0.08% of yttrium, 0.002%-0.02% of carbon, smaller than or equal to 0.2% of tantalum, smaller than or equal to 0.023% of oxygen, smaller than or equal to 0.015% of nitrogen, smaller than or equal to 0.002% of hydrogen and the balance niobium and inevitable impurities, and the inevitable impurities must contain yttrium.

Description

Technical Field

[0001] The present invention relates to the field of alloys, and in particular to a niobium-tungsten alloy and a preparation method thereof. Background Art

[0002] Niobium-tungsten alloy (Nb-W) is widely used in aerospace hot-end components, nuclear reactor cladding materials, high-temperature protective coatings, and other fields due to its excellent high-temperature strength, creep resistance, and corrosion resistance. Adding molybdenum (Mo) and zirconium (Zr) to form a niobium-tungsten-molybdenum-zirconium (Nb-W-Mo-Zr) alloy system further enhances the alloy's performance: Mo refines the grain structure and enhances the alloy's high-temperature stability; Tungsten forms a substitutional solid solution through solid solution strengthening, effectively improving the material's high-temperature strength and creep resistance; and Zr promotes the precipitation of second-phase particles through a dispersion strengthening mechanism, further enhancing the alloy's heat resistance. This multi-component synergistic strengthening design strategy enables this alloy system to exhibit excellent performance in high-temperature applications. Summary of the Invention

[0003] In order to solve the problems existing in the existing niobium-tungsten-molybdenum-zirconium alloy preparation technology, while ensuring the precise control of each element, taking into account the uniformity of composition, impurity control and process economy, the present invention proposes a niobium-tungsten alloy and a preparation method thereof.

[0004] In a first aspect of the present invention, the present invention provides a method for preparing a niobium-tungsten alloy, comprising the following steps:

[0005] 1) vacuum reduction sintering a powder compact comprising niobium powder, first tungsten powder, first molybdenum powder, and yttrium powder to obtain a niobium-tungsten-molybdenum alloy bar;

[0006] 2) subjecting the powder materials including niobium oxide, aluminum powder, second tungsten powder, and second molybdenum powder to a thermite reaction to obtain a niobium-tungsten-molybdenum-aluminum alloy block;

[0007] 3) subjecting the niobium-tungsten-molybdenum-aluminum alloy block to vacuum electron beam melting to obtain a niobium-tungsten-molybdenum alloy plate;

[0008] 4) Placing the zirconium sheet between the niobium-tungsten-molybdenum alloy bar and the niobium-tungsten-molybdenum alloy plate to form a stacked structure, and fixing the stacked structure with niobium wire to obtain a smelting electrode;

[0009] 5) The smelting electrode is subjected to vacuum electron beam melting to obtain niobium tungsten alloy.

[0010] Calculated by mass percentage, niobium-tungsten alloy includes: 4.5%-5.5% tungsten, 1.5%-2.5% molybdenum, 1.4%-2.2% zirconium, ≤0.08% yttrium, 0.002%-0.02% carbon, ≤0.2% tantalum, ≤0.023% oxygen, ≤0.015% nitrogen, ≤0.002% hydrogen, and the remainder of niobium and unavoidable impurities, which must contain yttrium.

[0011] Through the above-mentioned preparation method, the present invention not only improves process economy and controls costs, but also achieves improved alloy properties. The synergistic solid solution strengthening effect of tungsten (4.5%-5.5%) and molybdenum (1.5%-2.5%) significantly enhances the alloy's high-temperature strength and creep resistance above 1600°C. The addition of molybdenum refines the grains, hinders dislocation movement at grain boundaries, and improves the material's mechanical properties. Zirconium (1.4%-2.2%) further enhances the alloy's strength through dispersion strengthening and combines with trace amounts of carbon (0.002%-0.02%) to form a uniformly dispersed ZrC phase, enabling the alloy to maintain excellent deformation resistance even at extreme temperatures. This method reduces energy consumption by optimizing the smelting process, achieving synergistic improvements in the high-temperature performance, room-temperature plasticity, and impurity control of niobium-tungsten alloys.

[0012] In any embodiment of the first aspect, the metal element blank in the powder blank includes 4.5%-5.5% tungsten, 1.5%-2.5% molybdenum, ≤0.18% tantalum, 0.1%-0.5% yttrium, and the balance niobium and unavoidable metal impurities.

[0013] In any embodiment of the first aspect, the niobium powder comprises, by mass percentage, 0.3%-0.35% carbon, 0.2%-0.25% oxygen, ≤0.18% tantalum, ≤0.06% nitrogen, and the balance niobium and unavoidable impurities.

[0014] In any embodiment of the first aspect, step 1) includes: mixing a binder, niobium powder, a first tungsten powder, a first molybdenum powder and yttrium powder and pressing the mixture to obtain a powder blank; and vacuum reduction sintering the powder blank to obtain a niobium tungsten molybdenum alloy bar.

[0015] Optionally, the binder includes alcohol and / or shellac. Optionally, the pressing pressure is 10mbar-36mbar. Optionally, the temperature of the vacuum reduction sintering is 1650℃-1800℃ and the vacuum degree is ≤5×10 -3 mbar.

[0016] In any embodiment of the first aspect, the mass ratio of tungsten to molybdenum in the powder is (4.5-5.5):(1.5-2.5).

[0017] In any embodiment of the first aspect, the aluminum powder content in the powder is 40%-45% by weight. Optionally, the powder further comprises a slag-forming agent and / or an exothermic agent. Optionally, the powder comprises 5%-10% of the slag-forming agent and / or 6%-12% of the exothermic agent, by weight percentage. Optionally, after the thermite reaction, the powder is vacuum cooled to below 200°C.

[0018] In any embodiment of the first aspect, the vacuum electron beam melting of the niobium-tungsten-molybdenum-aluminum alloy block satisfies any one or more of the following conditions: melting power of 160 kW to 260 kW; melting speed of 40 kg / h to 60 kg / h; vacuum degree ≤ 5×10 -3 mbar; the vacuum electron beam melting method is horizontal melting.

[0019] In any embodiment of the first aspect, the vacuum electron beam melting of the niobium, tungsten, molybdenum, and aluminum alloy block includes two vacuum electron beam meltings, and the two vacuum electron beam meltings satisfy any one or more of the following conditions: the primary melting power ≥ the secondary melting power; the primary melting speed ≥ the secondary melting speed.

[0020] In any embodiment of the first aspect, the weight ratio of the niobium-tungsten-molybdenum alloy strip to the niobium-tungsten-molybdenum alloy plate is (30-40):(60-70).

[0021] In any embodiment of the first aspect, the niobium tungsten molybdenum alloy strips and the niobium tungsten molybdenum alloy plates are alternately stacked, and the zirconium sheets are disposed between adjacent niobium tungsten molybdenum alloy strips and niobium tungsten molybdenum alloy plates.

[0022] In any embodiment of the first aspect, each layer of zirconium sheets, each layer of niobium tungsten molybdenum alloy strips and each layer of niobium tungsten molybdenum alloy plates have the same area perpendicular to the stacking direction, and their projections on any niobium tungsten molybdenum alloy plate along the stacking direction are the same.

[0023] In any embodiment of the first aspect, the zirconium sheet is formed by splicing n polygonal zirconium sheet units. Optionally, the zirconium sheet unit is four trapezoidal zirconium sheet units of equal area.

[0024] In any embodiment of the first aspect, the thickness of the niobium, tungsten, and molybdenum alloy strips is 5 mm to 50 mm, the thickness of the niobium, tungsten, and molybdenum alloy plates is 5 mm to 50 mm, and the thickness of the zirconium sheets is 0.1 mm to 1 mm. Optionally, the width ratio of the niobium, tungsten, and molybdenum alloy strips to the niobium, tungsten, and molybdenum alloy plates is 1:(2-10). Optionally, the niobium, tungsten, and molybdenum alloy strips are arranged sequentially along the width of the niobium, tungsten, and molybdenum alloy plates. Optionally, the zirconium sheet units are arranged sequentially along the width of the niobium, tungsten, and molybdenum alloy plates.

[0025] In any embodiment of the first aspect, the vacuum electron beam melting of the melting electrode satisfies any one or more of the following conditions: melting power is 360 kW-370 kW; melting speed is 70 kg / h-100 kg / h; vacuum degree is ≤4×10 - 4 mbar.

[0026] In any embodiment of the first aspect, the vacuum electron beam melting of the smelting electrode includes two vacuum electron beam meltings, and the two vacuum electron beam meltings satisfy any one or more of the following conditions: the ingot diameters of the two vacuum electron beam meltings are each independently φ150 mm-300 mm; the first melting is horizontal melting, and the second melting is vertical melting; the first melting power is ≤ the second melting power; and the first melting speed is ≥ the second melting speed.

[0027] In a second aspect of the present invention, the present invention provides a niobium-tungsten alloy, which is prepared by the preparation method described in the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 shows a front view of the melting electrode in Example 1;

[0030] Figure 2a shows a top view of the niobium tungsten molybdenum alloy plate in Example 1;

[0031] Figure 2b shows a top view of the zirconium sheet layer in Example 1;

[0032] Figure 2c A top view of the niobium-tungsten-molybdenum alloy strip in Example 1 is shown.

[0033] Attached photos:

[0034] 10. Niobium-tungsten-molybdenum alloy plate; 20. Zirconium sheet; 30. Niobium-tungsten-molybdenum alloy bar. DETAILED DESCRIPTION

[0035] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be obtained commercially.

[0036] At present, some products in the Nb-W5 alloy industry comply with the following standards:

[0037] However, the conventional preparation process of the above-mentioned Nb-W5 alloy usually adopts the electric arc furnace melting method, which has the following significant defects: First, the process of electric arc furnace melting is relatively cumbersome, and the electrodes need to be prepared through precision machining to form consumable electrodes that meet the size requirements, and the electrode composition uniformity and surface finish need to be strictly controlled during the process, resulting in a long production cycle; and because the temperature distribution of the molten pool is uneven and the cooling rate is difficult to accurately control during the arc melting process, defects such as pores and shrinkage cavities are easily formed in the ingot, especially for alloy systems containing active elements (such as zirconium and yttrium). The interaction between these elements and residual oxygen and nitrogen will further aggravate the formation of pores, resulting in a decrease in the density of the alloy, affecting the mechanical properties and high-temperature stability of the material; in addition, in order to meet the stringent requirements for material purity in high-end application fields such as aircraft engine hot end components, the industry generally believes that the lower the carbon content, the better, and the use of raw materials containing carbon elements is avoided as much as possible during the preparation process.

[0038] However, the inventors discovered that a specific amount of trace carbon in the alloy is conducive to the formation of a dispersed ZrC phase with the Zr element, which can further hinder dislocation movement and enable the alloy to maintain excellent deformation resistance at extreme temperatures; and the vacuum electron beam melting method can more accurately control the content of low-melting-point impurity elements such as carbon, and can effectively reduce the dissolution of interstitial impurity elements in the molten metal, thereby reducing the formation of precipitation pores.

[0039] Based on this discovery, the present invention provides a niobium-tungsten alloy and a preparation method thereof.

[0040] A first embodiment of the present invention provides a method for preparing a niobium-tungsten alloy, comprising the following steps:

[0041] 1) vacuum reduction sintering a powder compact comprising niobium powder, first tungsten powder, first molybdenum powder, and yttrium powder to obtain a niobium-tungsten-molybdenum alloy bar;

[0042] 2) subjecting the powder materials including niobium oxide, aluminum powder, second tungsten powder, and second molybdenum powder to a thermite reaction to obtain a niobium-tungsten-molybdenum-aluminum alloy block;

[0043] 3) subjecting the niobium-tungsten-molybdenum-aluminum alloy block to vacuum electron beam melting to obtain a niobium-tungsten-molybdenum alloy plate;

[0044] 4) Placing the zirconium sheet between the niobium-tungsten-molybdenum alloy bar and the niobium-tungsten-molybdenum alloy plate to form a stacked structure, and fixing the stacked structure with niobium wire to obtain a smelting electrode;

[0045] 5) The smelting electrode is subjected to vacuum electron beam melting to obtain niobium tungsten alloy.

[0046] Calculated by mass percentage, niobium-tungsten alloy includes: 4.5%-5.5% tungsten, 1.5%-2.5% molybdenum, 1.4%-2.2% zirconium, ≤0.08% yttrium, 0.002%-0.02% carbon, ≤0.2% tantalum, ≤0.023% oxygen, ≤0.015% nitrogen, ≤0.002% hydrogen, and the remainder of niobium and unavoidable impurities, which must contain yttrium.

[0047] In the above preparation method, niobium powder is used as a raw material to prepare niobium-tungsten-molybdenum alloy bars. Carbon is introduced through the niobium powder. Niobium oxide is also used as a raw material to prepare niobium-tungsten-molybdenum-aluminum alloy blocks through an aluminothermic reduction reaction. This solves the problem of excessive carbon introduced by the use of niobium powder, which is difficult to remove. This allows the carbon content to be controlled between 0.002% and 0.02%. The niobium-tungsten-molybdenum-aluminum alloy blocks are then melted in a vacuum electron beam furnace to fully remove the introduced aluminum. The niobium-tungsten alloy is then obtained through steps 4) and 5). In particular, the vacuum electron beam melting in step 5) allows for more precise control of the content of low-melting-point impurity elements such as carbon and effectively reduces the dissolution of interstitial impurity elements in the molten metal, thereby reducing the formation of precipitation pores. Through this preparation method, a uniform niobium-tungsten alloy with the above-mentioned composition is successfully produced. In this ratio, the synergistic solid solution strengthening of tungsten (4.5%-5.5%) and molybdenum (1.5%-2.5%) significantly improves the alloy's high-temperature strength and creep resistance above 1600°C. The addition of molybdenum also refines the grain size and inhibits dislocation motion. Zirconium (1.4%-2.2%), through dispersion strengthening, combines with trace carbon (0.002%-0.02%) to form a dispersed ZrC phase, further enhancing the alloy's strength and maintaining excellent deformation resistance even at extreme temperatures. Yttrium (≤0.08%), as a trace alloying element, refines the grain size during alloy preparation and enhances the alloy's high-temperature oxidation resistance. This method, by optimizing the smelting process, not only improves process economy and controls costs, but also enhances the alloy's performance.

[0048] In some embodiments, the metal element composition of the powder blank includes 4.5%-5.5% tungsten, 1.5%-2.5% molybdenum, ≤0.18% tantalum, 0.1%-0.5% yttrium, and the remainder niobium and unavoidable metallic impurities. The tungsten and molybdenum contents correspond to the target alloy. The trace amount of tantalum further enhances the alloy's solid solution strengthening, improving high-temperature stability and radiation resistance while avoiding adverse effects on plasticity. The introduction of a trace amount of yttrium effectively refines grains, improves sintered density, and enhances oxidation resistance.

[0049] In some embodiments, the niobium powder comprises, by weight, 0.3%-0.35% carbon, 0.2%-0.25% oxygen, ≤0.18% tantalum, ≤0.06% nitrogen, and the balance niobium and unavoidable impurities. The appropriate amount of carbon in the niobium powder not only reacts with the oxygen in the niobium powder and escapes without excessively forming brittle carbides, but also combines with Zr to form a dispersed ZrC phase, resulting in the final niobium, tungsten, and molybdenum alloy having excellent overall properties.

[0050] In some embodiments, step 1) includes: mixing a binder, niobium powder, a first tungsten powder, a first molybdenum powder, and yttrium powder, and then pressing to obtain a powder compact; and vacuum reduction sintering the powder compact to obtain a niobium-tungsten-molybdenum alloy bar. The addition of the binder significantly improves the powder formability and strength of the compact, preventing looseness caused by variations in powder flowability. Furthermore, the binder decomposes or volatilizes under heat during the subsequent vacuum sintering process, helping to form a uniform pore structure, facilitating gas escape, and reducing the impact of residual impurities on alloy properties.

[0051] In some embodiments, the binder includes alcohol and / or shellac flakes. Shellac flakes (commonly also called lacquer flakes) used in the present invention are natural resin binders typically composed of lac resin, wax, and minor impurities. Shellac flakes are used as temporary binders in powder metallurgy. They exhibit excellent adhesion, thermoplasticity, and low-temperature decomposition properties, enhancing the strength of the powder blank during the pressing phase and completely pyrolyzing and volatilizing during the subsequent sintering process, leaving no residue. Their naturally biodegradable nature also makes them an environmentally friendly process additive.

[0052] In some embodiments, the pressing pressure is between 10 mbar and 36 mbar, for example, 10 mbar, 12 mbar, 14 mbar, 16 mbar, 18 mbar, 20 mbar, 22 mbar, 24 mbar, 26 mbar, 28 mbar, 30 mbar, 32 mbar, 34 mbar, or 36 mbar, or within a range of any two of the foregoing pressures. Such a pressure can provide the powder compact with an appropriate density and mechanical strength, thereby preventing cracking during subsequent handling or sintering, and preventing problems such as powder particle breakage caused by excessive pressure.

[0053] In some embodiments, the vacuum reduction sintering temperature is 1650°C-1800°C, for example, 1650°C, 1660°C, 1670°C, 1680°C, 1690°C, 1700°C, 1710°C, 1720°C, 1730°C, 1740°C, 1750°C, 1760°C, 1770°C, 1780°C, 1790°C, 1800°C, or any two of the above temperatures. This temperature range allows for more complete metallization of high-melting-point metal powders such as niobium, tungsten, and molybdenum, achieving dense sintering, promoting a thorough carbon-oxygen reaction, and completely decomposing and volatilizing the binder, while also avoiding over-burning caused by excessively high temperatures.

[0054] In some embodiments, the vacuum degree is ≤5×10 -3 mbar, for example 5×10 -3 mbar, 4×10 -3 mbar, 3×10 - 3 mbar, 2×10 -3 mbar, 1×10 -3 mbar, 9×10 -4 mbar, 8×10 -4 mbar, 7×10 -4 mbar, 6×10 -4 mbar, 5×10 -4 mbar, or within the range of any two of the above values, or less than 5×10 -4 mbar. This vacuum range can effectively eliminate residual oxygen and water vapor in the furnace, prevent oxidation of active metals such as niobium, tungsten, and molybdenum at high temperatures, ensure precise control of alloy composition, and ultimately obtain high-purity and dense niobium, tungsten, and molybdenum alloy materials.

[0055] In some embodiments, the mass ratio of tungsten to molybdenum in the powder is (4.5-5.5): (1.5-2.5), so that the alloy composition after smelting matches the composition of the target niobium tungsten molybdenum alloy and controls the composition deviation caused by the large deviation of the tungsten and molybdenum ratio in the powder and the powder blank.

[0056] In some embodiments, the aluminum content of the powder is 40%-45% by weight, for example, 40%, 41%, 42%, 43%, 44%, 45%, or any range between two of the foregoing values. This content range provides sufficient heat to ensure sufficient reduction of niobium oxide and complete fusion of the refractory metal, while also preventing excessive boiling caused by excessive aluminum, achieving thermal equilibrium in the system and producing a dense alloy block with uniform distribution of niobium, tungsten, molybdenum, and aluminum elements and low oxygen content.

[0057] In some embodiments, the powder further comprises a slag forming agent and / or a heat generating agent. The slag forming agent is used to react with the metal oxide to generate a low melting point slag, which is convenient for separating metals from impurities. The type of slag forming agent that can be used in the present invention is not particularly limited, and includes but is not limited to calcium fluoride, silicon dioxide, calcium oxide, aluminum oxide, etc. Although the powder already contains 40%-45% by mass of aluminum powder as the main heat generating agent and reducing agent, additional heat generating agents can still be added to the system of the present invention to adjust the reaction rate, temperature or product composition. The type of heat generating agent that can be used in the present invention is not particularly limited, and includes but is not limited to magnesium powder, ferrosilicon, etc.

[0058] In some embodiments, the powder includes 5%-10% by weight of a slag-forming agent, for example, 5%, 6%, 7%, 8%, 9%, 10%, or any range between two of the foregoing values. The slag-forming agent in such a concentration reacts with the metal oxide to form a low-melting-point slag, which facilitates the slag's aggregation and buoyancy, while not excessively diluting the heat of the reaction system.

[0059] In some embodiments, the powder includes 6%-12% of an exothermic agent, for example, 6%, 7%, 8%, 9%, 10%, 11%, or 12% of an exothermic agent, or within the range of any two of the above values, in terms of mass percentage. In addition to the original aluminum powder, the system includes the exothermic agent in the above amount to assist the aluminum powder in increasing the total heat release of the system, maintaining the stability of the high-temperature environment, promoting metal melting and subsequent separation from the slag, thereby enhancing reaction stability and preventing loss of control or the introduction of excessive impurities due to excessive exothermic agent.

[0060] In some embodiments, the temperature of the thermite reaction is above 1650°C, for example, 1650°C, 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, or within a range of any two of the foregoing temperatures or higher. A thermite reaction temperature of 1650°C or above can completely reduce difficult-to-reduced metal oxides, thereby improving metal recovery. Furthermore, the high temperature can reduce slag viscosity, accelerate metal droplet settling, and improve product purity.

[0061] In some embodiments, after the thermite reaction, the metal is cooled in vacuum to a temperature below 200° C., such as 200° C., 190° C., 180° C., 170° C., 160° C., 150° C., 140° C., 130° C., 120° C., 110° C., 100° C., 90° C., 80° C., 70° C., 60° C., 50° C., 40° C., 30° C., or below 30° C., or within a range of any two of the foregoing temperatures. Cooling to the above temperatures under vacuum can prevent surface oxidation of the high-temperature metal during cooling.

[0062] In some embodiments, the vacuum electron beam melting power of the niobium-tungsten-molybdenum-aluminum alloy ingot is 160 kW to 260 kW, such as 160 kW, 170 kW, 180 kW, 190 kW, 200 kW, 210 kW, 220 kW, 230 kW, 240 kW, 250 kW, or 260 kW, or within a range of any two of these values. This melting power balances energy efficiency and melting quality, promotes uniform distribution of refractory elements such as niobium, tungsten, and molybdenum, and avoids compositional segregation.

[0063] In some embodiments, the melting rate of the vacuum electron beam melting of the niobium, tungsten, molybdenum, and aluminum alloy ingot is 40 kg / h to 60 kg / h, for example, 40 kg / h, 41 kg / h, 42 kg / h, 43 kg / h, 44 kg / h, 45 kg / h, 46 kg / h, 47 kg / h, 48 kg / h, 49 kg / h, 50 kg / h, 51 kg / h, 52 kg / h, 53 kg / h, 54 kg / h, 55 kg / h, 56 kg / h, 57 kg / h, 58 kg / h, 59 kg / h, 60 kg / h, or within the range of any two of the above values. The above moderate melting rate can fully melt the alloy and maintain a sufficient high temperature residence time, effectively remove impurities such as oxygen and nitrogen, improve purity, and achieve an optimal match between melting quality and cost.

[0064] In some embodiments, the vacuum degree of the vacuum electron beam melting of the niobium-tungsten-molybdenum-aluminum alloy block is ≤ 5×10 -3 mbar, for example 5×10 -3 mbar, 4×10 -3 mbar, 3×10 -3 mbar, 2×10 -3 mbar, 1×10 -3 mbar, 9×10 -4 mbar, 8×10 -4 mbar, 7×10 -4 mbar, 6×10 -4 mbar, 5×10 -4 mbar, or within the range of any two of the above values, or less than 5×10 -4 The high vacuum environment can remove interstitial impurities such as oxygen, nitrogen, and hydrogen in the alloy, significantly reducing the impurity content and improving the alloy's structural density and composition homogeneity.

[0065] In some embodiments, vacuum electron beam melting of niobium-tungsten-molybdenum-aluminum alloy blocks is horizontal melting, wherein horizontal flow of the melt promotes floating of low-density inclusions such as Al2O3 to the surface, combined with a high vacuum environment to achieve deep purification.

[0066] In some embodiments, vacuum electron beam melting of the niobium-tungsten-molybdenum-aluminum alloy ingot involves two vacuum electron beam melting cycles. The first melting cycle removes most impurities such as oxygen and nitrogen, while the second melting cycle further purifies the alloy, reducing the impurity content to extremely low levels. Furthermore, the two vacuum electron beam melting cycles ensure sufficient diffusion of high-melting-point elements such as tungsten and molybdenum, eliminating segregation and achieving a balance between purity and performance.

[0067] In some embodiments, the two vacuum electron beam melting of the niobium, tungsten, molybdenum, and aluminum alloy blocks satisfy the requirement that the first melting power ≥ the second melting power, wherein the first high-power melting achieves deep purification and coarse grain crushing, and the second lower-power melting focuses on homogenizing the structure, refining the grains, and repairing micro defects.

[0068] In some embodiments, the two vacuum electron beam melting of the niobium, tungsten, molybdenum, and aluminum alloy blocks satisfy the requirement that the first melting speed is greater than or equal to the second melting speed. The first rapid melting breaks up the crystal structure, achieving preliminary purification and impurity removal of the thermite alloy block. The second lower speed melting promotes uniform nucleation and further reduces the impurity content.

[0069] In some embodiments, the weight ratio of the niobium, tungsten, and molybdenum alloy strips to the niobium, tungsten, and molybdenum alloy plates is (30-40):(60-70), such as 30:70, 31:69, 32:68, 33:67, 34:66, 35:65, 36:64, 37:63, 38:62, 39:61, or 40:60, or any range within any two of these ratios. By combining niobium, tungsten, and molybdenum alloy strips and niobium, tungsten, and molybdenum alloy plates with a specific carbon content in the above ratios, the overall carbon content can be precisely controlled at a low cost, achieving a balance between material performance and production costs.

[0070] On the other hand, the alloy's high Zr content makes it more difficult to control its segregation during the smelting process, making it difficult to achieve uniform dispersion of the ZrC phase. In some embodiments, niobium-tungsten-molybdenum alloy strips and niobium-tungsten-molybdenum alloy plates are alternately stacked, with zirconium sheets positioned between adjacent niobium-tungsten-molybdenum alloy strips and plates. This stacked structure ensures a uniform smelting composition, eliminates localized molybdenum enrichment, and ensures the target niobium-tungsten ratio. Furthermore, the placement of zirconium sheets between layers controls their segregation and ensures uniform dispersion and precipitation.

[0071] In some embodiments, each layer of zirconium sheets, each layer of niobium-tungsten-molybdenum alloy strip, and each layer of niobium-tungsten-molybdenum alloy plate has the same area perpendicular to the stacking direction, and their projections along the stacking direction onto any niobium-tungsten-molybdenum alloy plate are the same. Using this equal-area stacked design for melting electrodes ensures uniform distribution of electron beam energy across the same cross-sectional area, reducing compositional segregation during the melting process and resulting in niobium-tungsten alloy with isotropic mechanical properties.

[0072] In some embodiments, the zirconium sheet is composed of n polygonal zirconium sheet units. n can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. The polygons can be triangles, quadrilaterals, pentagons, hexagons, heptagons, or other irregular shapes. The polygonal unit structure increases the contact interface between the zirconium sheet and the niobium, tungsten, and molybdenum alloy strip / plate, promoting element diffusion and interlayer position stability during smelting, thereby balancing smelting efficiency and production reliability.

[0073] In some embodiments, the zirconium sheet unit is four trapezoidal zirconium sheet units with equal areas.

[0074] In some embodiments, the thickness of the niobium, tungsten, and molybdenum alloy strip is 5 mm to 50 mm, such as 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, or 50 mm, or within a range of any two of the foregoing values. In some embodiments, the thickness of the niobium, tungsten, and molybdenum alloy plate is 5 mm to 50 mm, such as 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, or 50 mm, or within a range of any two of the foregoing values. In some embodiments, the thickness of the zirconium sheet is 0.1 mm to 1 mm, such as 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm, or within a range of any two of the foregoing values. The thickness matching relationship between these three can ensure that the stacked structure is heated evenly and has a reasonable composition distribution during the melting process, which not only ensures the melting efficiency but also helps to control the composition and organizational stability of the final alloy.

[0075] In some embodiments, the width ratio of the niobium-tungsten-molybdenum alloy strip to the niobium-tungsten-molybdenum alloy plate is 1:(2-10), such as 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any range of any two of these ratios. This width ratio ensures that the alloy strip fits snugly within the alloy plate, improving structural stability while ensuring uniform heat conduction or current distribution.

[0076] In some embodiments, the niobium tungsten molybdenum alloy strips are arranged in sequence along the width direction of the niobium tungsten molybdenum alloy plate. The above arrangement of the niobium tungsten molybdenum alloy strips maintains a high fit with the niobium tungsten molybdenum alloy plate. Compared with the arrangement along the length direction, it is more conducive to processing alignment and overall assembly accuracy, improves the mechanical consistency and heat transfer path integrity of the components during use, and enhances the overall performance of the system.

[0077] In some embodiments, the zirconium sheet units are arranged in sequence along the width direction of the niobium tungsten molybdenum alloy plate. This arrangement direction is conducive to the bundling of assembled niobium wires. When the arrangement directions of the zirconium sheet units and the niobium tungsten molybdenum alloy strips are consistent, it is conducive to the consistent transmission direction of heat flow and force flow in each layer.

[0078] In some embodiments, the vacuum electron beam melting power for melting the electrode is 360 kW to 370 kW, such as 360 kW, 361 kW, 362 kW, 363 kW, 364 kW, 365 kW, 366 kW, 367 kW, 368 kW, 369 kW, or 370 kW, or within a range of any two of these values. This high-power electron beam can instantly penetrate the zirconium-niobium-tungsten-molybdenum multilayer interface, effectively and completely eutecticating the alloy strip / plate with the zirconium sheet.

[0079] In some embodiments, the vacuum electron beam melting process for melting the electrode can be performed at a melting rate of 70 kg / h to 100 kg / h, such as 70 kg / h, 75 kg / h, 80 kg / h, 85 kg / h, 90 kg / h, 95 kg / h, or 100 kg / h, or within a range of any two of these values. These melting rates enable rapid melting while maintaining a sufficient high-temperature residence time, ensuring scalable production efficiency.

[0080] In some embodiments, the vacuum degree of the vacuum electron beam melting of the melting electrode is ≤ 4×10 -4 mbar, for example 4×10 -4 mbar, 3×10 -4 mbar, 2×10 -4 mbar, 1×10 -4 mbar or within the range of any two of the above values, or less than 1×10 -4 The high vacuum environment can effectively reduce the oxidation of impurity elements and gas inclusions, improve the purity of the smelting process, and thus enhance the structural uniformity and performance stability of the resulting niobium-tungsten alloy.

[0081] In some embodiments, the vacuum electron beam melting of the smelting electrode includes two vacuum electron beam meltings. The first melting can remove most impurities, and the second melting further purifies the electrode to reduce the impurity content to an extremely low level. The two meltings can further promote the uniform distribution of alloy components and improve the structural density of the alloy.

[0082] In some embodiments, the ingot diameters of the two vacuum electron beam melting processes are each independently φ150 mm-300 mm, for example, 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, 200 mm, 210 mm, 220 mm, 230 mm, 240 mm, 250 mm, 260 mm, 270 mm, 280 mm, 290 mm, 300 mm, or within the range of any two of the above values.

[0083] In some embodiments, two vacuum electron beam melting processes are performed, with the first melting being horizontal and the second melting being vertical. The first horizontal melting facilitates initial alloy formation, while the subsequent vertical melting enhances the removal of impurity elements, further promotes uniform element diffusion, effectively eliminates stratification and segregation, and improves structural uniformity and compositional consistency.

[0084] In some embodiments, the two vacuum electron beam melting processes satisfy the condition that the power of the first melting process is less than or equal to the power of the second melting process. The first melting process at a lower power helps to heat slowly and avoid splashing and gas inclusions, while the second melting process at a higher power can deepen the molten pool, enhance the stirring effect, further purify the alloy, and improve the uniformity of the structure.

[0085] In some embodiments, the two vacuum electron beam melting processes satisfy the requirement that the first melting speed ≥ the second melting speed. The faster first melting process can achieve efficient initial melting and forming, and the slower second melting process helps to extend the molten pool maintenance time, enhance the volatilization of impurity elements and the uniformity of composition, thereby improving the homogeneity of the alloy.

[0086] A second embodiment of the present invention provides a niobium-tungsten alloy, which is prepared by the preparation method described in any one of the first embodiments of the present invention.

[0087] Example

[0088] The following examples and comparative examples will further illustrate the beneficial effects of the present application, but the scope of the present invention is not limited to these examples.

[0089] Test Method

[0090] Quantitative analysis of oxygen (O), nitrogen (N), and hydrogen (H) was performed using a LECO elemental analyzer in accordance with the Chinese national standard GB / T 15076.14.

[0091] Quantitative analysis of carbon (C) was performed using the CS-822 carbon and sulfur analyzer in accordance with the Chinese national standard GB / T 15076.8-2008.

[0092] (2) Using a plasma spectrometer, quantitative analysis of metallic impurity elements in niobium was performed according to the Chinese national standard GB / T 15076.10;

[0093] (3) X-ray fluorescence spectrometry (XRF) was used to quantitatively analyze tungsten (W), molybdenum (Mo), yttrium (Y), zirconium (Zr), niobium (Nb) and other elements in accordance with the Chinese national standards GB / T 15076.5 and GB / T15076.6.

[0094] (4) Using an Instron universal material testing machine, the tensile strength (R m ), specified plastic extension strength (Rp 0.2 ), and elongation after fracture (A), wherein the alloy samples were obtained by successively subjecting the alloy ingots to the following heat treatment and forging: (1) Heat treatment process: heating to 1200-1600℃ and then keeping warm for 4h, then cooling to below 200℃ with the furnace; (2) Forging process: preheating at 800℃, then heating to 1650℃ and starting forging, forging in 5 passes with a deformation of 20% in each pass, and the final forging temperature ≥1100℃.

[0095] Example 1

[0096] Step 1: Preparation of niobium tungsten molybdenum alloy bars

[0097] Niobium powder preparation process

[0098] First, niobium oxide and carbon black are mixed in a mass ratio to ensure that the amount of carbon black added meets the stoichiometric ratio for the reaction with niobium oxide. In this embodiment, the purity of niobium pentoxide is not less than 99.50%, and the purity of carbon black is not less than 98.0%.

[0099] Next, two carbonization processes are performed to produce niobium powder. Specifically, the first carbonization process is carried out at a temperature range of 1150°C to 1200°C for 1-2 hours; the second carbonization process is carried out within the same temperature range, but for a longer period of 6-10 hours, resulting in niobium powder. The composition of the niobium powder measured using the above method is: 99.25% niobium, 0.32% carbon, 0.089% tantalum, 0.23% oxygen, 0.057% nitrogen, and the remainder impurities.

[0100] The obtained niobium powder was mixed evenly with tungsten powder (4.95%), molybdenum powder (1.87%) and yttrium powder (0.2%).

[0101] 2) Anhydrous ethanol was added as a binder at a ratio of 5% by weight relative to the total weight of the powder to the mixed powder, and the mixture was pressed under a pressure of 15 mbar to form a powder blank with a size of 20 × 24 × 450 mm.

[0102] 3) The powder is sintered in a vacuum reduction furnace with the temperature controlled within the range of 1650℃-1800℃ and the vacuum degree ≤5×10-3 mbar, made of niobium tungsten molybdenum alloy bars.

[0103] Step 2: Preparation of niobium-tungsten-molybdenum alloy blocks by aluminothermic reduction method

[0104] 1) Niobium oxide (42.16%), aluminum powder (42.5%), tungsten powder (5.2%), molybdenum powder (2.14%), and a slag-forming agent (calcium oxide, purity not less than 93%, 3%) are mixed uniformly in proportion for more than 4 hours to obtain a powder.

[0105] 2) The powder is put into an aluminothermic reduction furnace and a heating agent (sodium chlorate, 5%) is added to carry out aluminothermic reaction. The reaction temperature is higher than 1650℃ until the pressure in the reaction chamber drops, indicating that the smelting is completed.

[0106] 3) After smelting, vacuum cool to 200°C to obtain niobium-tungsten-molybdenum-aluminum alloy blocks.

[0107] Step 3: Preparation of niobium-tungsten-molybdenum alloy plate

[0108] The niobium-tungsten-molybdenum-aluminum alloy block obtained in step 2 was melted once and twice in a 600KW horizontal electron beam furnace to produce a niobium-tungsten-molybdenum alloy plate. The power of the first melting was 220kw, the melting speed was 50kg / h, and the vacuum degree was controlled at ≤5×10 - 3 mbar; the power of the secondary smelting is 208kw, the smelting speed is 46.5kg / h, and the vacuum degree is controlled at ≤5×10 -3 mbar.

[0109] Step 4: Prepare electrodes

[0110] 1) The niobium tungsten molybdenum alloy bar is 450mm long, 24mm wide and 20mm thick, while the niobium tungsten molybdenum alloy plate is cut into 450mm long, 96mm wide and 18mm thick. The zirconium sheet is accurately weighed at a ratio of (niobium tungsten molybdenum alloy bar + niobium tungsten molybdenum alloy plate): zirconium sheet of 100:3.2. The zirconium sheet is selected to be 0.2mm thin.

[0111] 2) Cut the weighed zirconium sheets into trapezoidal units of equal area, each piece also 450 mm long.

[0112] 3) If Figure 1 Front view of melting electrode and Figures 2a-2cAs shown in the top view of the layers, the four layers are laid out from bottom to top. The first layer is a niobium-tungsten-molybdenum alloy plate 10, on which four zirconium sheets 20 are laid, completely covering the alloy plate without overlapping and aligned with the front, back, left, and right edges of the alloy plate. The second layer is four niobium-tungsten-molybdenum alloy bars 30, also ensuring that they are aligned with the first layer of alloy plates, and the length of the alloy bars is the same as the height direction of the zirconium sheet units. Then, four zirconium sheets 20, niobium-tungsten-molybdenum alloy plates 10, four zirconium sheets 20, and niobium-tungsten-molybdenum alloy bars 30 are laid out again in the same manner as before, ensuring that they are aligned with the overall structure. After stacking is completed, niobium wire is used to fix and bundle them together to obtain a smelting electrode.

[0113] Step 5: Smelting and preparing niobium-tungsten-molybdenum-zirconium alloy in

[0114] The smelting electrode was subjected to primary and secondary smelting in a 600KW electron beam furnace to obtain the final product, NbW5-2 alloy ingot. The ingot diameter of the primary smelting was φ220mm, the power was 350kw, the smelting speed was 90.0kg / h, the lower electrode speed was 0.4RPM, and the vacuum degree was ≤4.0×10 -4 mbar; the ingot diameter for secondary smelting is φ220 mm, the power is 360 kW, the smelting speed is 80.0 kg / h, the lower electrode speed is 0.4 RPM, and the vacuum degree is ≤4.0×10 -4 mbar.

[0115] Table 1 shows the compositional analysis data of the resulting niobium, tungsten, molybdenum, and zirconium alloy ingot, measured at different locations. The upper portion of the ingot represents 200 mm from the top, the lower portion represents 1 / 2 of the ingot, and the lower portion represents 200 mm from the bottom. The elemental content of the upper, middle, and lower portions of the ingot in Example 1 was relatively uniform, with minimal deviation.

[0116] Table 1: Composition analysis data of niobium-tungsten-molybdenum-zirconium alloy ingots

[0117] The content of component Y was low and not detected.

[0118] Comparative Example 1

[0119] The difference from Example 1 is that step 1 is not used to prepare the niobium tungsten molybdenum alloy strip. The niobium tungsten molybdenum alloy plate obtained in step 3 is cut into alloy strips with a length of 450 mm, a width of 24 mm, and a thickness of 20 mm, which replace the niobium tungsten molybdenum alloy strip in step 1 to form an electrode. The rest is the same as Example 1.

[0120] Comparative Example 2

[0121] The difference from Example 1 is that the steps 2 and 3 of preparing the niobium tungsten molybdenum alloy plate are replaced by the following method:

[0122] 1) Niobium powder is the same as the niobium powder in Example 1, and the niobium powder is mixed evenly with tungsten powder (5.15%), molybdenum powder (2.34%), and yttrium powder (0.2%).

[0123] 2) 5% of anhydrous ethanol was added to the mixed powder as a binder relative to the total weight of the powder, and the mixed powder was pressed under a pressure of 15 mbar to form a plate-shaped powder blank with dimensions of 18 × 96 × 450 mm.

[0124] 3) The powder is sintered in a vacuum reduction furnace with the temperature controlled within the range of 1650℃-1800℃ and the vacuum degree ≤5×10 -3 mbar, made of niobium tungsten molybdenum alloy plate.

[0125] Comparative Example 3

[0126] The difference from Example 1 is that in step 4, when preparing the electrode, the weighed zirconium sheets are evenly overlapped and laid below the bottom niobium tungsten molybdenum alloy plate and above the top niobium tungsten molybdenum alloy strip.

[0127] The above method was used to measure the performance parameters of the ingots obtained in Example 1 and Comparative Examples 1-3. The average values of the element contents in the upper, middle and lower parts of the ingots, as well as R m 、Rp 0.2 The test results of and A are recorded in Tables 2 and 3.

[0128] Table 2 Composition analysis data of niobium-tungsten-molybdenum-zirconium alloy ingots

[0129] Table 3 Performance parameters

[0130] It can be seen that compared with Comparative Example 1, the tensile strength and tensile strength of Example 1 are significantly improved, while the elongation after fracture is only slightly reduced, indicating that it significantly improves the alloy strength without sacrificing much plasticity. However, since the niobium tungsten molybdenum alloy bars and plates prepared entirely by the aluminothermic reduction method in Comparative Example 1 have a significantly reduced carbon content, it is difficult to form a dispersed ZrC phase to hinder dislocation movement. At the same time, the residual trace amount of solid-solution aluminum may reduce the high-temperature performance of the alloy, so the strength is significantly lower than that of Example 1. The ingot prepared in Comparative Example 2 has a higher carbon content, which can form a dispersed precipitate phase, thereby hindering dislocation movement and significantly improving the tensile strength. However, the accumulation of more carbides can lead to stress concentration and may even cause work hardening, thereby reducing ductility, causing increased brittleness and reduced plasticity, which is manifested as low tensile strength and elongation after fracture. Comparative Example 3 exhibits the lowest strength and increased plasticity, resulting in the weakest overall mechanical properties. This is likely due to the susceptibility of zirconium to oxidation or volatilization in the outer layer during high-temperature smelting, which reduces the effective zirconium content and prevents uniform diffusion into the alloy matrix, weakening the solid solution strengthening and ZrC dispersion strengthening effects, leading to a decline in mechanical properties. In comparison, Example 1 achieves a better balance between strength and plasticity, better meeting the practical application requirements of niobium-tungsten alloys.

[0131] The following investigates the effects of melting power and melting speed on the composition and properties of niobium-tungsten-molybdenum-aluminum alloy blocks during two vacuum electron beam melting processes.

[0132] Example 2

[0133] The difference from Example 1 is that in step 3, the power of the first smelting is 216 kw, and the smelting speed is 43 kg / h; the power of the second smelting is 228 kw, and the smelting speed is 48 kg / h.

[0134] The component analysis data and properties of Example 2 were measured, and the test results are recorded in Tables 4 and 5.

[0135] Table 4 Composition analysis data of niobium-tungsten-molybdenum-zirconium alloy ingots

[0136] Table 5 Performance parameters

[0137] Comparing Example 2 with Example 1, it can be seen that when the primary melting power is greater than the secondary melting power and the primary melting speed is greater than the secondary melting speed in step 3, the tensile strength and tensile strength are slightly increased, and the elongation after fracture is slightly decreased. The three performance characteristics generally maintain a good balance.

[0138] The following examines the effects of the melting power and melting speed of the two vacuum electron beam melting processes on the composition and properties of the melting electrode.

[0139] Example 3

[0140] The difference from Example 1 is that in step 5, the power of the first smelting is 350 kW, and the smelting speed is 70 kg / h; the power of the second smelting is 340 kW, and the smelting speed is 80 kg / h.

[0141] The component analysis data and performance test results of Measurement Example 3 are recorded in Tables 6 and 7.

[0142] Table 6 Composition analysis data of niobium-tungsten-molybdenum-zirconium alloy ingots

[0143] Table 7 Performance parameters

[0144] In step 5 of Example 1, the primary melting power is less than the secondary melting power and the primary melting speed is greater than the secondary melting speed, while in step 5 of Example 3, the primary melting power is greater than the secondary melting power and the primary melting speed is less than the secondary melting speed. According to the data in Table 6, it can be seen that the carbon content and Zr content in the ingot of Example 3 are relatively low, indicating that there is a certain degree of segregation of the elements, resulting in the loss of some dispersion strengthening effect, causing a decrease in strength performance, while bringing about an improvement in plasticity.

[0145] The following examines the effect of the zirconium sheet laying method on the composition and performance.

[0146] Example 4

[0147] The difference from Example 1 is that the zirconium sheets are not cut, but are laid in the form of whole sheets aligned with the edges of the niobium-tungsten-molybdenum alloy plates.

[0148] The component analysis data and performance test results of Measurement Example 4 are recorded in Tables 8 and 9.

[0149] Table 8 Composition analysis data of niobium-tungsten-molybdenum-zirconium alloy ingots

[0150] Table 9

[0151] Comparing Examples 1 and 4, it can be seen that when the zirconium sheet is not cut and laid in the form of a whole sheet aligned with the edge of the niobium tungsten molybdenum alloy plate, the zirconium content of the resulting niobium tungsten molybdenum zirconium alloy ingot is reduced, resulting in a certain decrease in tensile strength and tensile strength, while the room temperature plasticity is slightly increased due to the decrease in defects, that is, the splicing structure can improve the strength performance after melting by increasing the contact between the zirconium sheet and the niobium tungsten molybdenum alloy strip / plate, while maintaining a certain plasticity.

[0152] Although the specific embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and substitutions may be made to those details based on all the teachings disclosed, and these changes are all within the scope of protection of the present invention. The full scope of the present invention is given by the appended claims and any equivalents thereof.

Claims

1. A method for preparing a niobium-tungsten alloy, comprising the following steps: 1) vacuum reduction sintering a powder compact comprising niobium powder, first tungsten powder, first molybdenum powder, and yttrium powder to obtain a niobium-tungsten-molybdenum alloy bar; 2) subjecting the powder materials including niobium oxide, aluminum powder, second tungsten powder, and second molybdenum powder to a thermite reaction to obtain a niobium-tungsten-molybdenum-aluminum alloy block; 3) performing vacuum electron beam melting on the niobium-tungsten-molybdenum-aluminum alloy block to obtain a niobium-tungsten-molybdenum alloy plate; 4) placing a zirconium sheet between the niobium-tungsten-molybdenum alloy bar and the niobium-tungsten-molybdenum alloy plate to form a stacked structure, and fixing the stacked structure with a niobium wire to obtain a smelting electrode; 5) subjecting the smelting electrode to vacuum electron beam melting to obtain niobium tungsten alloy, The niobium-tungsten alloy comprises, in terms of mass percentage, 4.5%-5.5% tungsten, 1.5%-2.5% molybdenum, 1.4%-2.2% zirconium, ≤0.08% yttrium, 0.002%-0.02% carbon, ≤0.2% tantalum, ≤0.023% oxygen, ≤0.015% nitrogen, ≤0.002% hydrogen, and the remainder of niobium and unavoidable impurities, which must contain yttrium.

2. The preparation method according to claim 1, wherein The metal elements in the powder blank include 4.5%-5.5% of tungsten, 1.5%-2.5% of molybdenum, ≤0.18% of tantalum, 0.1%-0.5% of yttrium, and the balance of niobium and inevitable metal impurities.

3. The preparation method according to claim 1 or 2, wherein Calculated by mass percentage, the niobium powder includes 0.3%-0.35% of carbon, 0.2%-0.25% of oxygen, ≤0.18% of tantalum, ≤0.06% of nitrogen, and the balance of niobium and unavoidable impurities.

4. The preparation method according to any one of claims 1 to 3, wherein The step 1) comprises: Mixing a binder, the niobium powder, the first tungsten powder, the first molybdenum powder, and the yttrium powder, and then pressing the mixture to obtain the powder blank; performing vacuum reduction sintering on the powder blank to obtain the niobium tungsten molybdenum alloy bar; Optionally, the adhesive comprises alcohol and / or shellac flakes; Optionally, the pressing pressure is 10 mbar-36 mbar; Optionally, the vacuum reduction sintering temperature is 1650°C-1800°C and the vacuum degree is ≤5×10 -3 mbar.

5. The preparation method according to any one of claims 1 to 4, wherein The mass ratio of tungsten to molybdenum in the powder is (4.5-5.5): (1.5-2.5).

6. The preparation method according to any one of claims 1 to 5, wherein The mass content of the aluminum powder in the powder is 40%-45%; Optionally, the powder further comprises a slag-forming agent and / or a heat-generating agent. Optionally, the powder comprises 5%-10% of the slag-forming agent and / or 6%-12% of the exothermic agent in terms of mass percentage; Optionally, the aluminothermic reaction is followed by vacuum cooling to below 200°C.

7. The preparation method according to any one of claims 1 to 6, wherein The vacuum electron beam melting of the niobium-tungsten-molybdenum-aluminum alloy block satisfies any one or more of the following conditions: Melting power is 160kw-260kw; Melting speed is 40kg / h-60kg / h; Vacuum degree ≤5×10 -3 mbar; Vacuum electron beam melting is horizontal melting.

8. The preparation method according to claim 7, wherein The vacuum electron beam melting of the niobium-tungsten-molybdenum-aluminum alloy block includes two vacuum electron beam meltings, and the two vacuum electron beam meltings meet any one or more of the following conditions: The primary melting power is greater than or equal to the secondary melting power; The primary melting speed is greater than or equal to the secondary melting speed.

9. The preparation method according to any one of claims 1 to 8, wherein The weight ratio of the niobium-tungsten-molybdenum alloy strip to the niobium-tungsten-molybdenum alloy plate is (30-40):(60-70).

10. The preparation method according to any one of claims 1 to 9, wherein The niobium-tungsten-molybdenum alloy strips and the niobium-tungsten-molybdenum alloy plates are alternately stacked, and the zirconium sheet is arranged between adjacent niobium-tungsten-molybdenum alloy strips and the niobium-tungsten-molybdenum alloy plates.

11. The preparation method according to claim 10, wherein The areas of the zirconium sheets, niobium-tungsten-molybdenum alloy strips and niobium-tungsten-molybdenum alloy plates in each layer perpendicular to the stacking direction are the same, and their projections on any niobium-tungsten-molybdenum alloy plate along the stacking direction are the same.

12. The preparation method according to any one of claims 1 to 11, wherein The zirconium sheet is composed of n polygonal zirconium sheet units. Optionally, the zirconium sheet unit is four trapezoidal zirconium sheet units with equal areas.

13. The preparation method according to any one of claims 1 to 12, wherein The thickness of the niobium-tungsten-molybdenum alloy strip is 5mm-50mm, the thickness of the niobium-tungsten-molybdenum alloy plate is 5mm-50mm, and the thickness of the zirconium sheet is 0.1mm-1mm. Optionally, the width ratio of the niobium-tungsten-molybdenum alloy strip to the niobium-tungsten-molybdenum alloy plate is 1:(2-10), Optionally, the niobium-tungsten-molybdenum alloy strips are arranged in sequence along the width direction of the niobium-tungsten-molybdenum alloy plate. Optionally, the zirconium sheet units are arranged sequentially along the width direction of the niobium-tungsten-molybdenum alloy plate.

14. The preparation method according to any one of claims 1 to 13, wherein The vacuum electron beam melting of the melting electrode satisfies any one or more of the following conditions: Melting power is 360kw-370kw; Melting speed is 70kg / h-100kg / h; Vacuum degree ≤4×10 -4 mbar.

15. The preparation method according to claim 14, wherein The vacuum electron beam melting of the melting electrode includes two vacuum electron beam meltings, and the two vacuum electron beam meltings meet any one or more of the following conditions: The ingot diameters of the two vacuum electron beam melting processes are independently φ150mm-300mm; The first smelting is horizontal smelting, and the second smelting is vertical smelting; Primary melting power ≤ secondary melting power; The primary melting speed is greater than or equal to the secondary melting speed.

16. A niobium-tungsten alloy prepared by the preparation method according to any one of claims 1 to 15.

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