Tungsten-based high-entropy alloy preparation process based on rare earth elementary substance and aluminum-titanium-boron synergistic refinement

Abstract

The invention provides a tungsten-based high-entropy alloy preparation process based on rare earth elementary substance and aluminum-titanium-boron synergistic refinement. According to the preparation method, tungsten (50-70 wt%) serves as a matrix, La / Ce / Y rare earth elementary substance powder (0.05-0.30 wt%) and aluminum-titanium-boron Al-Ti5-B grain refiner (0.05-0.30 wt%) powder are added, and four-stage temperature-controlled sintering including pre-sintering (750-800 DEG C / H2-Ar), medium-temperature diffusion (900-1000 DEG C / vacuum), final sintering and heat preservation (1250-1450 DEG C / Ar, 5.0-6.0 GPa) is carried out, grain refinement (smaller than 50 microns) is achieved at the temperature smaller than or equal to 1500 DEG C, the grain size is reduced by 54.7% compared with that of a traditional process, and the grain refinement effect is achieved. The method is suitable for medical instrument shielding cases and industrial cutter substrates.

Description

Technical Field

[0001] The present invention relates to the field of metal powder metallurgy, specifically a preparation process of tungsten-based high-entropy alloy based on the coordinated refinement of rare earth elements and aluminum, titanium and boron. Background Art

[0002] Tungsten-based high-entropy alloys (HEAs) are multi-element solid solutions composed of five or more principal elements: W, Al, Fe, Ni, and Zr. Their high configurational entropy effect suppresses the formation of brittle phases, resulting in high hardness (>500 HV) and excellent high-temperature stability, making them suitable for precision components such as high-end cutting tools and medical device shielding components. However, because the refractory component W accounts for as much as 50-70% by weight, conventional sintering processes face significant challenges: 1. Conventional liquid-phase sintering requires temperatures exceeding 1500°C, resulting in grain coarsening (>50μm); 2. While spark plasma sintering can lower the temperature, it is expensive and can result in residual segregation phases such as Cr2O3; Existing technologies are unable to simultaneously achieve fine-grained microstructures (<50μm) below 1500°C, hindering the industrial application of HEAs in precision instruments. Summary of the Invention

[0003] In order to make up for the shortcomings of the existing technology, the present invention provides a tungsten-based high-entropy alloy preparation process based on the synergistic refinement of rare earth elements and aluminum, titanium and boron, overcomes the problem of grain coarsening (>50μm) during low-temperature (<1500℃) high-entropy alloy sintering, and adopts the synergistic mechanism of "rare earth metal elements + aluminum, titanium and boron grain refiners + low-temperature and high-pressure multi-stage sintering" to improve the refinement effect by more than 3 times.

[0004] The present invention is achieved through the following technical solutions: The tungsten-based high-entropy alloy is made of the following raw materials in parts by weight: 50-70 parts of tungsten powder as a matrix, 0.05-0.30 parts of other elements and rare earth single substance La / Ce / Y powder, the other elements being aluminum (Al), zirconium (Zr), nickel (Ni), and iron (Fe), with a total of 30-50 parts of other elements and rare earth; and aluminum titanium boron grain refiner powder, with Al-Ti5-B being added in an amount of 0.05-0.30 parts.

[0005] Further preferably, among the raw materials, ≥ 4 elements are selected from the other elements aluminum (Al) / zirconium (Zr) / nickel (Ni) / iron (Fe) and rare earth elements lanthanum (La) / cerium (Ce) / yttrium (Y), and the target contains at least one rare earth element (La / Ce / Y), and the total weight proportion of rare earth elements is 0.05-0.30 parts.

[0006] Further preferably, among the raw materials, aluminum titanium boron raw materials are selected: Al-Ti5-B grain refiner requires all TiB2 particle sizes ≤5μm, Al-Ti5-B alloy powder particle size ≤100μm, tungsten powder, other elements and rare earth element particle size ≤100μm; to ensure the grain refining effect.

[0007] A preparation process of a tungsten-based high entropy alloy, characterized by comprising the following steps: (1) Mixing stage (1-1) Mixed powder tungsten W matrix (50-70wt%) + Al / Ni / Fe / Zr and rare earth element powder La / Ce / Y (0.05-0.30wt%) ≥ 4 kinds; other elements and rare earth total 30-50wt%; (1-2) Add aluminum-titanium-boron grain refiner Al-Ti5-B (accounting for 0.05-0.30wt% of the total of tungsten powder, other elements and rare earth elements), protect the mixing and ball milling for 2 hours under high-purity argon (≥99.999%), and add 1-5% zinc stearate lubricant.

[0008] (2) Cold isostatic pressing: 200-300 MPa; relative density of the molded body 80%-90%; (3) Low temperature and high pressure multi-stage sintering stage Grain refinement (<50μm) is achieved at ≤1500℃ through four-stage temperature-controlled sintering, including pre-firing (750-800℃ / H2-Ar), medium-temperature diffusion (900-1000℃ / vacuum), final sintering (1250-1450℃ / Ar, 5.0-6.0GPa high pressure) and heat preservation (1250-1450℃ / Ar, 5.0-6.0GPa high pressure).

[0009] Further preferably, step (3) further includes step (4): (4) Finishing: grinding / polishing products; (4-1) Surface grinding (Ra ≤ 0.8 μm); (4-2) Performance verification SEM microstructure, etc.

[0010] Further preferably, step (3) is a low-temperature and high-pressure multi-stage sintering stage, and the detailed steps are as follows: (3-1) Pre-sintering stage: Pre-sintering at 750-800℃ for 1.5-2h in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:3 to reduce the oxygen content at the grain boundaries and reduce the oxides that may be produced by some elements such as rare earth elements lanthanum (La) and cerium (Ce). The heating rate is 5-10℃ / min.

[0011] (3-2) Medium temperature stage: vacuum sintering 1×10 -3Sinter at a medium temperature of 900-1000℃ under Pa atmosphere for 1-1.5h, with a heating rate of 5-10℃ / min.

[0012] (3-3) High-pressure final sintering stage: Use high-purity argon (≥99.999%) in a 5.0-6.0 GPa atmosphere, sinter at 1250-1450℃ for 1.5-2h, and a heating rate of 5-10℃ / min.

[0013] (3-4) High-pressure insulation stage: Use high-purity argon (≥99.999%) in a 5.0-6.0 GPa atmosphere, keep the temperature at 1250-1450℃ for 20-40 minutes, and then cool naturally after completion.

[0014] The beneficial effect of the present invention is that, with tungsten (50-70wt%) as the matrix, by adding other elements aluminum (Al) / zirconium (Zr) / nickel (Ni) / iron (Fe) and rare earth elements lanthanum (La) / cerium (Ce) / yttrium (Y) powder (0.05-0.30wt%) and aluminum titanium boron Al-Ti5-B grain refiner (0.05-0.30wt%) powder, through pre-sintering (750-800℃ / H2-Ar), medium temperature diffusion (900-1000℃ / Ar), final sintering and heat preservation (1250-1450℃ / Ar, 5.0-6.0GPa high pressure), a fine equiaxed crystal structure with grain refinement (<50μm) is achieved at ≤1500℃, and the grain size is reduced by 54.7% compared with the traditional process. The present invention is suitable for medical device shielding covers and industrial tool substrates.

[0015] Based on the performance requirements of existing materials, this invention improves the grain refinement effect by more than 3 times through the synergistic mechanism of "rare earth metal elements and aluminum titanium boron grain refiners + low temperature and high pressure multi-stage sintering". It achieves the following performance breakthroughs: . BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attachment Figure 1 : SEM electron microscope image of TiB2 particles in the aluminum titanium boron Al-Ti5-B grain refinement (0.05-0.30wt%) used in this process.

[0017] Attachment Figure 2 : SEM electron microscope image of the grain boundary size of the cemented carbide tool substrate (W 62, Ni 18, Fe 12, Al 7.85, Y0.15 (wt%)) produced using this process. DETAILED DESCRIPTION

[0018] This invention overcomes the challenge of achieving high densification at low temperatures by combining a rare earth element combination of La, Ce, and Y (0.05-0.30 wt%) with low temperature and high pressure. This high-entropy alloy preparation process utilizes a tungsten matrix containing 50-70 wt% aluminum (Al), zirconium (Zr), nickel (Ni), iron (Fe), and the rare earth elements lanthanum (La), cerium (Ce), and yttrium (Y), along with an aluminum-titanium-boron grain refiner (0.05-0.30 wt%). Through low-temperature, high-pressure sintering, a fine equiaxed structure with a grain size of ≤50 μm is achieved, making it suitable for the manufacture of industrial cutting tools, medical device shielding components, and other applications.

[0019] (1) Synergistic mechanism of rare earth element + aluminum titanium boron grain refiner: La / Ce series combination or Y element reduces surface oxides, and the grain boundary oxygen content decreases from 2.1at% to 0.7at%. The aluminum titanium boron refiner provides TiB2; the nucleation particles reduce the grain size (size ≤ 50μm) through sintering recrystallization.

[0020] (2) Optimization of low-temperature and high-pressure parameters: Keep the temperature at 5.0-6.0 GPa and the final sintering stage (1250-1450℃) for 0.5-1h to significantly reduce the sintering temperature and inhibit grain growth.

[0021] (3) Element regulation: Aluminum (Al) has a low melting point of about 660°C. It forms a transient liquid phase of 10-15 minutes during the medium-temperature diffusion stage, filling micropores (porosity < 0.5%) and promoting densification.

[0022] Rare earth selection basis: (1) La-Ce combination: improves impact toughness by 40%; (2) Y element: forms a Y2O3 dispersed phase, which reduces the oxidation rate at 800℃ by 50%.

[0023] Among the raw materials of the tungsten-based high-entropy alloy, tungsten powder accounts for 50-70%, and can be used in proportions of 50%, 53%, 58%, 65%, 68%, and 70%. Other elements and rare earth elements account for a total of 30-50%, and can be used in proportions of 30%, 32%, 35%, 42%, 47%, and 50%. Other elements are several of aluminum (Al), zirconium (Zr), nickel (Ni), and iron (Fe).

[0024] Example 1 The main components of the carbide tool matrix in the tungsten-based high-entropy alloy preparation process are selected as follows: W 12.4 kg, Ni 3.6 kg, Fe 2.4 kg, Al 1.57 kg, Y 0.03 kg, and Al-Ti5-B alloy powder 0.04 kg.

[0025] 1. Mixing process: (1) Select W powder 62%, Ni powder 18%, Fe powder 12%, Al powder 7.85%, rare earth yttrium powder 0.15%, particle size ≤ 100μm; (2) Add 0.2% Al-Ti5-B alloy powder, particle size ≤ 100 μm, TiB2 particle size ≤ 5 μm; (3) Ball milling for 2 hours under the protection of high-purity argon 99.999%, adding 1% zinc stearate lubricant.

[0026] 2. Suppression stage: Cold isostatic pressing 250MPa, the relative density of the formed body is 85%-90%.

[0027] 3. Low temperature and high pressure multi-stage sintering process: (3-1) Pre-sintering: 770°C for 2 h, hydrogen to argon volume ratio 1:3, grain boundary oxygen content decreased to 0.8 at %; heating rate 5°C / min.

[0028] (3-2) Medium temperature diffusion sintering: 1.5h at 900℃, vacuum 1×10 -3 Pa; heating rate 8℃ / min.

[0029] (3-3) Final firing: 1250-1300℃ for 2h, high-purity argon 99.999%, 6.0GPa pressure, heating rate 8℃ / min.

[0030] (3-4) Holding stage: 1250-1300℃ for 40min, high-purity argon 99.999%, 6.0GPa pressure, holding for 40min, grain boundary diameter 23.8μm, grain boundary diameter <50μm.

[0031] 4. Finishing and testing (4-1) Surface grinding, Ra ≤ 0.8 μm; (4-2) Performance verification SEM microstructure, etc.

[0032] Example 2 The main components of the carbide tool matrix are selected as follows: W 10.6 kg, Ni 4.1 kg, Fe 3.7 kg, Zr 1.58 kg, La 0.02 kg, and Al-Ti5-B alloy powder 0.02 kg.

[0033] 1. Mixing process: (1) Select W powder 53%, Ni powder 20.5%, Fe powder 18.5%, Zr powder 7.9%, rare earth lanthanum La powder 0.10%, particle size ≤ 100 μm; (2) Add 0.10% Al-Ti5-B alloy powder, particle size ≤ 100 μm, TiB2 particle size ≤ 5 μm; (3) Ball milling for 1 hour under the protection of high-purity argon 99.999%, adding 3% zinc stearate lubricant. (There is no rigid addition requirement for lubricant) 2. Suppression stage: Cold isostatic pressing 200MPa, the relative density of the formed body is 80%-84%.

[0034] 3. Low temperature and high pressure multi-stage sintering process: (3-1) Pre-sintering: 750°C for 2 h, hydrogen to argon volume ratio 1:3, the grain boundary oxygen content decreased to 0.8 at %; heating rate 10°C / min.

[0035] (3-2) Medium temperature diffusion sintering: 950℃ for 1h, vacuum 1×10 -3 Pa; heating rate 10℃ / min.

[0036] (3-3) Final firing: 1320-1380°C for 1.5 h, high-purity argon 99.999%, pressure 5.5 GPa, heating rate 10°C / min.

[0037] (3-4) Holding stage: 1320-1380℃ for 30min, high-purity argon 99.999%, 5.5GPa pressure, holding for 30min, grain boundary diameter 29.5μm, grain boundary diameter <50μm.

[0038] 4. Finishing and testing (4-1) Surface grinding, Ra ≤ 0.8 μm; (4-2) Performance verification SEM microstructure, etc.

[0039] Example 3 The main components of the carbide tool matrix in the tungsten-based high-entropy alloy preparation process are selected as follows: W 14 kg, Ni 3.08 kg, Zr 2.3 kg, Al 0.61 kg, Ce 0.06 kg, and Al-Ti5-B alloy powder 0.06 kg.

[0040] 1. Mixing process: (1) Select W powder 70%, Ni powder 15.4%, Zr powder 11.5%, Al powder 3.05%, rare earth cerium powder 0.30%, particle size ≤ 100 μm; (2) Add 0.30% Al-Ti5-B alloy powder, particle size ≤ 100 μm, TiB2 particle size ≤ 5 μm; (3) Ball milling for 1.5 hours under the protection of high-purity argon 99.999%, adding 5% zinc stearate lubricant. (There is no rigid addition requirement for lubricant) 2. Suppression stage: Cold isostatic pressing 300MPa, the relative density of the formed body is 85%-90%.

[0041] 3. Low temperature and high pressure multi-stage sintering process: (3-1) Pre-sintering: 800°C for 1 h, hydrogen to argon volume ratio 1:3, grain boundary oxygen content decreased to 0.8at%; heating rate 8°C / min.

[0042] (3-2) Medium temperature diffusion sintering: 1000℃ for 1h, vacuum 1×10 -3 Pa; heating rate 5℃ / min.

[0043] (3-3) Final firing: 1400-1450°C for 1 h, high-purity argon 99.999%, 5.0 GPa pressure, heating rate 5°C / min.

[0044] (3-4) Holding stage: 1400-1450℃ for 20 min, high-purity argon 99.999%, 5.0 GPa pressure, holding for 20 min, grain boundary diameter 35.2 μm, grain boundary diameter <50 μm.

[0045] 4. Finishing and testing (4-1) Surface grinding, Ra ≤ 0.8 μm; (4-2) Performance verification SEM microstructure, etc.

[0046] Except for the technical features described in the specification, the remaining technical features are known to those skilled in the art.

Claims

1. A tungsten-based high-entropy alloy based on the synergistic refinement of rare earth elements and aluminum, titanium and boron, characterized by: It is made of the following raw materials in parts by weight: 50-70 parts of tungsten powder as the matrix, 0.05-0.30 parts of other elements and rare earth elements La / Ce / Y powder, other elements are aluminum (Al) / zirconium (Zr) / nickel (Ni) / iron (Fe), and the total of other elements and rare earth elements is 30-50 parts; aluminum titanium boron grain refiner powder is added, and Al-Ti5-B is 0.05-0.30 parts.

2. The tungsten-based high entropy alloy according to claim 1, wherein: Among the raw materials, ≥ 4 elements are selected from the other elements aluminum (Al) / zirconium (Zr) / nickel (Ni) / iron (Fe) and the rare earth elements lanthanum (La) / cerium (Ce) / yttrium (Y), and the target contains at least one rare earth element (La / Ce / Y), and the total weight proportion of the rare earth elements is 0.05-0.30 parts.

3. The tungsten-based high entropy alloy according to claim 1, wherein: Among the raw materials, aluminum titanium boron raw materials are selected: Al-Ti5-B grain refiner requires that all TiB2 particle sizes are ≤5μm, Al-Ti5-B alloy powder particle size is ≤100μm; the particle size of tungsten powder, other elements and rare earth elements is ≤100μm; to ensure the grain refining effect.

4. A process for preparing the tungsten-based high entropy alloy according to claim 1, characterized in that: The following steps are involved: (1) Mixing stage: After the raw material powders are mixed, they are ball milled for 2-3 hours under the protection of high-purity argon gas ≥99.999%, and zinc stearate lubricant is added at a rate of 1-5% of the total weight of the raw materials; (2) Pressing stage: cold isostatic pressing: 200-300 MPa; relative density of the molded body 80%-90%; (3) Low temperature and high pressure multi-stage sintering stage Through the four-stage temperature-controlled sintering at 750-800℃ under H2-Ar protection in the pre-firing stage, 900-1000℃ in vacuum atmosphere in the medium-temperature diffusion stage, 1250-1450℃ in Ar atmosphere and 5.0-6.0GPa high pressure in the final firing stage, and 1250-1450℃ in Ar atmosphere and 5.0-6.0GPa high pressure in the holding stage, grain refinement and particle size <50μm are achieved at ≤1500℃.

5. The process for preparing a tungsten-based high entropy alloy according to claim 4, wherein: Step (3) also includes the following steps: (4) Finishing: surface grinding, Ra ≤ 0.8 μm.

6. The process for preparing a tungsten-based high entropy alloy according to claim 4, wherein: Step (3) low temperature and high pressure multi-stage sintering stage, the specific steps are as follows: (3-1) Pre-sintering stage: Pre-sintering at 750-800℃ for 1.5-2h in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:3 to reduce the oxygen content at the grain boundaries and reduce the oxides that may be produced by some elements, such as rare earth elements lanthanum La and cerium Ce. The heating rate is 5-10℃ / min. (3-2) Medium temperature stage: vacuum sintering 1×10 -3 Sintering at 900-1000℃ for 1-1.5h under Pa atmosphere, heating rate 5-10℃ / min; (3-3) High-pressure final sintering stage: using high-purity argon with a purity of ≥99.999% in an atmosphere of 5.0-6.0 GPa, sintering at 1250-1450℃ for 1.5-2h, with a heating rate of 5-10℃ / min; (3-4) High-pressure insulation stage: Use high-purity argon gas with a purity of ≥99.999% in an atmosphere of 5.0-6.0 GPa, keep the temperature at 1250-1450℃ for 20-40 minutes, and then cool naturally after completion.

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