A method for regulating uniform distribution of tungsten-nickel-iron binder phase by synergistic circulation pressure relief sintering

Abstract

The application discloses a kind of synergic circulation pressure relief sintering regulation tungsten nickel iron binder phase distribution method, comprising the following steps: taking raw material and mixing according to mass percentage;Mixed raw material is loaded into mould, is placed in discharge plasma sintering equipment, and is sintered under vacuum or inert atmosphere condition;5~20MPa pre-pressure is applied in room temperature to first temperature interval heating process;When mould temperature rises to 1000~1280 DEG C, implement low-frequency stage formula circulation pressure relief-recompression procedure;Subsequently, the pressure is adjusted to 30~65MPa, and is kept at 1300~1500 DEG C for 2~12 min, then cooling, to get fine-grained tungsten nickel iron alloy.The application uses stage formula circulation pressure relief-recompression sintering method, promotes Ni-Fe binder phase repeated redistribution;Reduce the probability of local Ni-Fe binder phase over-wide enrichment and continuous binder phase pool formation;Increase the uniformity of Ni-Fe binder phase width distribution, improve organization consistency;It is favorable to simultaneously improve strength and plastic toughness matching.

Description

Technical Field

[0001] This invention relates to the field of refractory alloy technology, specifically to a method for regulating the uniform distribution of tungsten-nickel-iron binder phases through synergistic cyclic decompression sintering. Background Technology

[0002] Tungsten-nickel-iron alloys are a typical class of high-density tungsten-based heavy alloys, composed of a high-melting-point, high-strength W phase and a relatively soft Ni-Fe binder phase. They are widely used in high-density structural components, inertial elements, and high-performance functional components. Existing methods for preparing W-Ni-Fe high-density alloys are relatively mature. For example, attempts have been made to add small amounts of ceramic particles to W-Ni-Fe alloys to improve their strength or high-temperature performance through particle dispersion strengthening or interfacial pinning effects.

[0003] However, currently, there is a lack of a process scheme in the W-Ni-Fe system that introduces a small amount of specific ceramic particles as a second phase and implements minute-level staged cyclic decompression-recompression during the rapid densification stage, so that the ceramic particles and the variable pressure field can synergistically regulate the flow, distribution and bridging width of the Ni-Fe binder phase, while suppressing the coarsening of the W phase.

[0004] Under traditional constant-pressure SPS, the Ni-Fe binder phase tends to accumulate along local low-resistivity paths during densification, forming excessively wide binder phase regions or continuous binder phase pools, leading to local softening, uneven microstructure, and fluctuations in mechanical properties. While the addition of a conventional second phase can provide some grain refinement and dispersion strengthening, it often fails to adequately control the spatial distribution and width of the Ni-Fe binder phase. This invention utilizes the synergistic effect of a "ceramic second phase + staged cyclic depressurization-repressurization" to enhance the synchronous regulation of the morphological evolution of the W skeleton and the Ni-Fe binder phase in the dual-phase microstructure. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome existing defects and provide a method for regulating the uniform distribution of the tungsten-nickel-iron binder phase through synergistic cyclic decompression sintering. This method employs a staged cyclic decompression-recompression sintering process, which promotes repeated redistribution of the Ni-Fe binder phase; reduces the probability of excessive local enrichment of the Ni-Fe binder phase and the formation of continuous binder phase pools; improves the uniformity of the Ni-Fe binder phase width distribution and enhances microstructure consistency; and facilitates simultaneous improvement in strength and ductility matching. Furthermore, this method can be achieved solely through synergistic optimization of the composition and pressure program, without relying on complex equipment modifications, effectively solving the problems in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for regulating the uniform distribution of tungsten-nickel-iron binder phase through synergistic cyclic decompression sintering, comprising the following steps: S1. Weigh the raw materials according to the mass percentage and mix them evenly, wherein W: 90%~98%, Ni: 1.5%~7%, Fe: 0.5%~4%, ceramic particle second phase: 0.05%~3.0%, and the balance is unavoidable impurities; S2. After the raw materials are mixed evenly, they are loaded into a graphite mold. Graphite paper can be laid on the mold wall. The mold is then placed in a discharge plasma sintering equipment and sintered under vacuum or inert atmosphere conditions. S3. Apply 5-20 MPa during the heating process from room temperature to the first temperature range, and heat at 50-200℃ / min. The pre-pressure is used to improve the initial particle contact and compact stability. S4. When the mold temperature rises to 1000~1280℃, implement a low-frequency staged cyclic depressurization-repressurization procedure, specifically including: High pressure holding phase: 35-70 MPa, held for 60-240 seconds; Low pressure holding phase: 5-30 MPa, held for 30-180 seconds; The high-pressure holding phase and the low-pressure holding phase alternate for 3 to 10 cycles, with each cycle lasting 90 to 600 seconds. S5. After completing S4, adjust the pressure to 30-65 MPa and hold at 1300-1500℃ for 2-12 minutes to further densify the material. Then cool to obtain a fine-grained tungsten-nickel-iron alloy.

[0007] As a preferred embodiment of the present invention, in S1, the tungsten powder is ceramic particle-doped tungsten powder prepared by liquid-liquid wet chemical method, and the particle size of the tungsten powder is 1 to 2 μm.

[0008] In a preferred embodiment of the present invention, in S1, the second phase of the ceramic particles is selected from one or more of oxides or carbides.

[0009] As a preferred embodiment of the present invention, in S4, the starting temperature of the cyclic depressurization-repressurization procedure is 1050–1230°C. In a preferred embodiment of the present invention, in S1, the average particle size of the second phase of ceramic particles is 50 nm to 3 μm.

[0010] As a preferred technical solution of the present invention, the mixing method in S1 is wet ball milling or mechanical mixing. The wet ball milling medium is one or more of ethanol or anhydrous ethanol, and the ball milling time is 4 to 24 hours. After the mixing is completed, the mixture is dried and sieved to obtain a composite powder with uniform composition.

[0011] In a preferred embodiment of the present invention, the mass ratio of Ni to Fe in S1 is 2:1 to 5:1.

[0012] As a preferred embodiment of the present invention, the heating rate in S3 is 50-100 °C / min.

[0013] As a preferred embodiment of the present invention, in S4, the pressure difference between the high pressure and the low pressure is 15 to 40 MPa, and the pressure during the low pressure holding stage is not lower than 5 MPa.

[0014] As a preferred embodiment of the present invention, in S5, the Ni-Fe binder phase forms a discrete connecting bridge structure between W particles in the obtained fine-grained tungsten-nickel-iron alloy.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The synergistic cyclic decompression sintering method for regulating the uniform distribution of the tungsten-nickel-iron binder phase, as exemplified by this invention, demonstrates a synergistic effect between the ceramic second phase and the staged cyclic decompression-recompression process during sintering. This effect is mainly manifested in the following ways: ceramic particles act as grain boundary pinning and interface stabilization around the W phase and near the W / Ni-Fe interface, inhibiting W grain growth; ceramic particles can serve as separation points and hindrance points for the local flow of the Ni-Fe binder phase, reducing the tendency of long-distance aggregation and local over-enrichment of the binder phase; the high-pressure stage promotes particle rearrangement, pore compression, and sintering neck growth; the low-pressure stage allows the Ni-Fe binder phase to obtain redistribution space, mitigating the extrusion or accumulation of the binder phase along local channels under continuous high pressure; after multiple cycles, the Ni-Fe binder phase is more inclined to form a discrete connecting bridge structure with controlled width and uniform distribution between adjacent W particles.

[0016] 2. Compared with existing constant-pressure SPS or simple second-phase addition methods, this invention inhibits thermal softening and reduces the width of the adiabatic shear band by using ceramic particle second phase; promotes repeated redistribution of Ni-Fe binder phase through staged cyclic depressurization-repressurization; reduces the probability of excessive local enrichment of Ni-Fe binder phase and formation of continuous binder phase pools; improves the uniformity of Ni-Fe binder phase width distribution and improves microstructure consistency; facilitates simultaneous improvement of strength and ductility matching; and can be achieved through synergistic optimization of composition and pressure program without relying on complex equipment modifications. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the staged cyclic depressurization-repressurization pressure-time and temperature rise curve of the present invention; Figure 2 This is a microstructure diagram of the Ni-Fe binder phase in Example 1; Figure 3 This is a microstructure diagram of the Ni-Fe binder phase in Comparative Example 1; Figure 4 This is a microstructure diagram of the Ni-Fe binder phase in Comparative Example 2; Figure 5 This is a microstructure diagram of the Ni-Fe binder phase in Comparative Example 3; Figure 6 This is a comparison diagram of the compressive strength of the sample of this invention and the comparative sample. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: As Figure 1 , Figure 2 and Figure 6 As shown, the specific solution is as follows: Weigh the following by mass percentage: W 93.0%, Ni 4.9%, Fe 2.0%, ZrO2 0.1%; wherein the W powder is ZrO2 particle doped tungsten powder prepared by liquid-liquid wet chemical method with an average particle size of 2.5μm, the Ni powder and Fe powder have an average particle size of 1μm, and the ZrO2 particles have an average particle size of 200nm. Wet ball milling was performed for 12h using anhydrous ethanol as the ball milling medium, and after drying and sieving, it was loaded into a graphite mold. SPS sintering was carried out under vacuum conditions: a pre-pressure of 10 MPa was applied, and the temperature was increased at 100 °C / min; when the mold temperature reached 1160 °C, the pressure relief and re-pressure were cyclically started: high pressure of 60 MPa was maintained for 120 s, and low pressure of 15 MPa was maintained for 60 s, for a total of 5 cycles; after the cycle was completed, the sample was held at 1400 °C and 55 MPa for 8 min and then cooled to obtain the sample.

[0020] In the obtained samples, the W phase grains are relatively fine, the Ni-Fe binder phase is distributed in a relatively uniform bridging manner between the W particles, and the local continuous enrichment area is reduced.

[0021] Example 2, the specific solution is as follows: Weigh out the following by mass percentage: W 94.0%, Ni 4.0%, Fe 1.8%, Al2O3 0.2%. The raw material preparation method and mixing method are the same as in Example 1.

[0022] During sintering, a pre-pressure of 8 MPa was applied, and the temperature was increased at 90 °C / min. When the mold temperature reached 1120 °C, the pressure was cyclically depressurized and repressurized: high pressure of 50 MPa was maintained for 180 s, and low pressure of 10 MPa was maintained for 60 s, for a total of 4 cycles. Then, the sample was held at 1460 °C and 50 MPa for 6 min and cooled to obtain the sample.

[0023] In the obtained samples, the width fluctuation of the Ni-Fe binder phase decreased, and the uniformity of the microstructure was improved.

[0024] Example 3, the specific solution is as follows: Weigh out the following components by mass percentage: W 92.5%, Ni 5.0%, Fe 2.0%, ZrC 0.5%, ball mill for 10 hours, and then load into the mold. Apply a pre-pressure of 12 MPa during SPS sintering and heat up at 110℃ / min. When the mold temperature reaches 1200℃, start the cycle of depressurization-repressurization: high pressure 65 MPa held for 90s, low pressure 20 MPa held for 90s, for a total of 6 cycles. Then hold at 1380℃ and 60 MPa for 5 minutes and cool to obtain the sample.

[0025] The resulting samples showed more pronounced W phase refinement and a more controlled Ni-Fe binder phase distribution.

[0026] Comparative Example 1: Figure 3 and Figure 6 As shown, the same composition and heating regime as in Example 1 were used, but a constant pressure of 55 MPa was maintained throughout the SPS process, and the cyclic depressurization-repressurization procedure was not implemented. As a result, the ceramic particles in the obtained sample were prone to agglomeration, which affected the effect.

[0027] Comparative Example 2: Figure 4 and Figure 6 As shown, the same cyclic depressurization-repressurization system as in Example 1 was used, but no ceramic particles were added as a second phase. The distribution of the binder phase was improved, but it was still broader than that in Example 1.

[0028] Comparative Example 3: Figure 5 and Figure 6 As shown, the same composition as in Example 1 was used, but neither the cyclic decompression-recompression procedure nor the ceramic particle second phase was added. The particles in sample W were larger and the binder phase was wider.

[0029] This invention employs a staged cyclic depressurization-repressurization sintering method, which promotes repeated redistribution of the Ni-Fe binder phase; reduces the probability of excessive enrichment of the local Ni-Fe binder phase and the formation of continuous binder phase pools; improves the uniformity of the Ni-Fe binder phase width distribution and enhances the consistency of the microstructure; facilitates the simultaneous improvement of strength and ductility matching; and can be achieved solely through the synergistic optimization of composition and pressure program, without relying on complex equipment modifications.

[0030] All parts not disclosed in this invention are prior art, and their specific structures, materials, and working principles will not be described in detail. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for regulating the uniform distribution of tungsten-nickel-iron binder phase through synergistic cyclic decompression sintering, characterized in that, Includes the following steps: S1. Weigh the raw materials according to the mass percentage and mix them evenly, wherein W: 90%~98%, Ni: 1.5%~7%, Fe: 0.5%~4%, ceramic particle second phase: 0.05%~3.0%, and the balance is unavoidable impurities; S2. The mixed raw materials are loaded into a graphite mold and placed in a discharge plasma sintering equipment for sintering under vacuum or inert atmosphere conditions. S3. Apply a pre-pressure of 5-20 MPa during the heating process from room temperature to the first temperature range; S4. When the mold temperature rises to 1000~1280℃, implement a low-frequency staged cyclic depressurization-repressurization procedure, specifically including: High pressure holding phase: 35-70 MPa, held for 60-240 seconds; Low pressure holding phase: 5-30 MPa, held for 30-180 seconds; The high-pressure holding phase and the low-pressure holding phase alternate for 3 to 10 cycles, with each cycle lasting 90 to 600 seconds. S5. After completing S4, adjust the pressure to 30-65 MPa and hold at 1300-1500℃ for 2-12 minutes, then cool to obtain fine-grained tungsten-nickel-iron alloy.

2. The method for regulating the uniform distribution of the tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1, characterized in that: In S1, the tungsten powder is ceramic particle-doped tungsten powder prepared by liquid-liquid wet chemical method, and the particle size of the tungsten powder is 1-2 μm.

3. The method for regulating the uniform distribution of the tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1, characterized in that: In S1, the second phase of the ceramic particles is selected from one or more of oxides or carbides.

4. The method for regulating the uniform distribution of the tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1 or 2, characterized in that: In S1, the average particle size of the ceramic particles in the second phase is 50 nm to 3 μm.

5. The method for regulating the uniform distribution of the tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1, characterized in that: The mixing method in S1 is wet ball milling or mechanical mixing. The wet ball milling medium is one or more of ethanol or anhydrous ethanol, and the ball milling time is 4 to 24 hours.

6. The method for regulating the uniform distribution of the tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1, characterized in that: In S1, the mass ratio of Ni to Fe is 2:1 to 5:

1.

7. The method for regulating the uniform distribution of tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1, characterized in that: The heating rate in S3 is 50–100 °C / min.

8. The method for regulating the uniform distribution of the tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1, characterized in that: In S4, the pressure difference between high pressure and low pressure is 15-40 MPa, and the pressure during the low pressure maintenance stage is not lower than 5 MPa.

9. The method for regulating the uniform distribution of the tungsten-nickel-iron binder phase by synergistic cyclic decompression sintering according to claim 1, characterized in that: In S5, the fine-grained tungsten-nickel-iron alloy obtained has a Ni-Fe binder phase forming a discrete connecting bridge structure between W particles.

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