Medium-entropy alloy preparation method based on additive manufacturing and medium-entropy alloy prepared through medium-entropy alloy preparation method

Abstract

The invention relates to a medium-entropy alloy preparation method based on additive manufacturing and a medium-entropy alloy prepared through the medium-entropy alloy preparation method. The medium-entropy alloy preparation method comprises the following steps that N -Co-V pre-alloyed powder is prepared through a plasma rotating electrode; cooling at an interlayer cooling rate gt by a direct energy deposition process; forming is conducted under the condition of 105 K / s, the laser energy density is controlled to be 48-240 J / mm < 2 >, and a microstructure with a fault network and an L12 strengthening phase is obtained; after deposition is completed, naturally cooling to room temperature, and not carrying out heat treatment; and performance detection: determining the tensile strength of the material and confirming that no sigma phase exists. According to the method, an additional conventional strengthening means is not needed, the heat treatment process is reduced, the production cost is reduced, the plasma rotating electrode powder manufacturing is creatively combined with the direct energy deposition technology, and the preparation of the novel medium-entropy alloy with high strength and high plasticity is realized through the coordinated regulation and control of process parameters.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material preparation, and particularly relates to a method for preparing medium-entropy alloys based on additive manufacturing, and more particularly to a process for preparing Ni-Co-V series medium-entropy alloys with an in-situ formed stacking fault strengthening structure by using the direct energy deposition technique and the obtained materials. Background Art

[0002] Traditional medium / high-entropy alloys are mostly prepared by arc melting combined with casting processes, which have the following technical defects: (1) brittle σ phase is easily precipitated during solidification, seriously damaging the plasticity of the materials; (2) the cooling rate of the molten pool is low (usually <10^3 K / s), resulting in serious element segregation and poor compositional uniformity; (3) conventional strengthening means (such as precipitation strengthening) require complex heat treatment processes, increasing production costs. Existing additive manufacturing technologies are mostly limited to powder bed melting processes in the preparation of medium-entropy alloys, with problems such as low forming efficiency and poor powder utilization. The present invention innovatively adopts plasma rotating electrode powder making combined with direct energy deposition technology, and through coordinated regulation of process parameters, realizes the preparation of a new type of medium-entropy alloy with both high strength and high plasticity. Summary of the Invention

[0003] The problem solved by the present invention is to provide a method for preparing medium-entropy alloys based on additive manufacturing, which solves the problems raised in the above background art.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for additive manufacturing of medium-entropy alloys, which includes the following steps:

[0006] Step 1. Raw material preparation, preparing Ni-Co-V pre-alloy powder by using a plasma rotating electrode;

[0007] Step 2. Printing the raw materials in Step 1, forming by direct energy deposition process under the condition that the interlayer cooling rate >10^5 K / s, and controlling the laser energy density at 48 - 240 J / mm^2 to obtain a microstructure with stacking fault networks and L12 strengthening phases;

[0008] Step 3. Post-treatment, naturally cooling to room temperature after deposition, without heat treatment;

[0009] Step 4. Performance detection, determining the tensile strength of the material and confirming the absence of σ phase.

[0010] As an improved technical solution, the chemical formula of the L12 phase in Step 2 is (Ni,Co)_3V.

[0011] As an improved technical solution, the Ni-Co-V medium-entropy alloy based on direct energy deposition and stacking fault-L12 co-strengthening further includes a nano-L12 phase with a volume fraction of ≥5%, and the σ-phase content is <1 vol%.

[0012] As an improved technical solution, in step 1, the pre-alloy powder with a particle size of 53-106 μm is prepared by the plasma rotating electrode atomization method, the oxygen content is <200 ppm, and the sphericity is >0.9.

[0013] As an improved technical solution, in step 2, the laser power is 600-1000 W, the scanning speed is 500 mm / min, and the interlayer cooling rate is >10^5 K / s, effectively suppressing the precipitation of the σ phase;

[0014] The material obtained by the above preparation method is a Ni-Co-V medium-entropy alloy based on direct energy deposition and stacking fault-L12 co-strengthening. The Ni-Co-V (atomic percentage) ternary system is adopted, and the stacking fault energy is regulated by the atomic size difference (Ni: 0.124 nm, Co: 0.125 nm, V: 0.132 nm) to promote the formation of the stacking fault structure; the alloy composition range is: 29 wt% ≤ Ni ≤ 34%, 33 wt% ≤ Co ≤ 38%, 27 wt% ≤ V ≤ 32%, O ≤ 0.02%, N ≤ 0.05 wt%.

[0015] As an improved technical solution, the microstructural characteristics are: a high-density stacking fault network is formed, the stacking fault spacing is 10-50 nm, and nano-scale L12 ordered phases (size 20-500 nm, volume fraction 5-15%) are in-situ precipitated at the interfaces;

[0016] As an improved technical solution, the mechanical property indexes are: the tensile strength is ≥1200 MPa (≥200 MPa higher than that of the as-cast state), and the elongation after fracture remains at 25%, realizing the synergistic improvement of strength and plasticity.

[0017] As an improved technical solution, this medium-entropy alloy can be applied to aerospace load-bearing components.

[0018] The beneficial effects of the present invention are:

[0019] 1. The alloy obtained by the preparation method has no brittle σ phase, ensuring the strength of the alloy;

[0020] 2. The cooling rate of the molten pool is high, and the elements are evenly distributed;

[0021] 3. No additional conventional strengthening means are required, reducing the heat treatment process and production cost. The plasma rotating electrode powder making combined with the direct energy deposition technology is innovatively adopted, and through the coordinated regulation of process parameters, the preparation of a new medium-entropy alloy with both high strength and high plasticity is realized. Description of the Drawings

[0022] Figure 1 It is the TEM microstructure of the alloy in Example 1, showing a uniform equiaxed crystal structure without σ-phase characteristics.

[0023] Figure 2 It is the TEM analysis diagram, showing the symbiotic structure of stacking fault networks and L12 strengthening phases.

[0024] Figure 3 It is the comparison of the engineering stress-strain curves of the as-printed and as-cast alloys.

[0025] Figure 4 It is the morphology and particle size distribution of the alloy powder prepared by the plasma rotating electrode. Detailed Implementation Manner

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0027] A method for additive manufacturing of a medium-entropy alloy, which includes the following steps:

[0028] Step 1. Raw material preparation, using a plasma rotating electrode to prepare Ni-Co-V pre-alloy powder; in Step 1, the pre-alloy powder with a particle size of 53-106 μm is prepared by the plasma rotating electrode atomization method, the oxygen content is <200 ppm, and the sphericity is >0.9.

[0029] Step 2. Printing the raw materials in Step 1, forming by the direct energy deposition process under the condition that the interlayer cooling rate >10^5 K / s, and controlling the laser energy density at 48-240 J / mm^2 to obtain a microstructure with stacking fault networks and L12 strengthening phases; the chemical formula of the L12 phase in Step 2 is (Ni,Co)_3V. The Ni-Co-V medium-entropy alloy based on direct energy deposition and stacking fault-L12 synergistic strengthening also contains a nano-L12 phase with a volume fraction ≥5%, and the σ-phase content is <1 vol%. In Step 2, the laser power is 600-1000 W, the scanning speed is 500 mm / min, and the interlayer cooling rate >10^5 K / s, effectively suppressing the precipitation of the σ-phase;

[0030] Step 3. Post-treatment, naturally cooling to room temperature after deposition, without heat treatment;

[0031] Step 4. Performance detection, determining the tensile strength of the material and confirming the absence of the σ-phase.

[0032] Refer toFigures 1 - 4 As shown, the material obtained by the above preparation method is a Ni-Co-V medium entropy alloy based on direct energy deposition and stacking fault-L12 co-strengthening. A ternary system of Ni-Co-V (atomic percentage) is adopted, and the stacking fault energy is regulated through the atomic size difference (Ni: 0.124 nm, Co: 0.125 nm, V: 0.132 nm) to promote the formation of stacking fault structures. The alloy composition range is: 29 wt% ≤ Ni ≤ 34%, 33 wt% ≤ Co ≤ 38%, 27 wt% ≤ V ≤ 32%, O ≤ 0.02%, N ≤ 0.05 wt%. Microstructural characteristics: A high-density stacking fault network is formed, with a stacking fault spacing of 10 - 50 nm, and nano-scale L12 ordered phases (size 20 - 500 nm, volume fraction 5 - 15%) are in-situ precipitated at the interfaces. Mechanical property indicators: The tensile strength ≥ 1200 MPa (≥ 200 MPa higher than that of the as-cast state), and the elongation after fracture remains 25%, achieving the synergistic improvement of strength and plasticity. This medium entropy alloy can be applied in aerospace load-bearing components.

[0033] Example 1:

[0034] (1) Raw material preparation: Using a plasma rotating electrode atomization device, pre-alloyed powder is prepared under argon protection, with an electrode rotation speed of 20000 rpm and an atomization pressure of 6 MPa;

[0035] (2) Printing process: Using a BLT-C400 type direct energy deposition device, setting the laser power at 600 W - 1000 W, the spot diameter at 0.5 mm - 1.5 mm, the scanning rate at 500 mm / min, the powder feeding rate at 1 - 3 g / min, and the layer thickness at 0.2 - 0.4 mm;

[0036] (3) Post-treatment: After deposition, it is naturally cooled to room temperature without heat treatment;

[0037] (4) Performance testing: The tensile strength of 1200 MPa and the elongation of 25% are measured through a universal testing machine, and TEM analysis confirms the absence of σ phase.

[0038] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a medium-entropy alloy based on additive manufacturing and a medium-entropy alloy prepared therefrom, characterized in that: It includes the following steps: Step 1. Raw material preparation: preparing Ni-Co-V pre-alloyed powder using a plasma rotating electrode; Step 2. Print the raw material of step 1, and form it by direct energy deposition process under the condition of interlayer cooling rate>10^5K / s, and control the laser energy density at 48-240J / mm^2 to obtain a microstructure with stacking fault network and L12 strengthening phase; Step 3. Post-treatment: After the deposition is completed, it is naturally cooled to room temperature without heat treatment; Step 4. Performance testing to determine the tensile strength of the material and confirm the absence of σ phase.

2. A method for preparing a medium-entropy alloy based on additive manufacturing according to claim 1, characterized in that: The chemical formula of the L12 phase in step 2 is (Ni,Co)_3V.

3. A method for preparing a medium-entropy alloy based on additive manufacturing according to claim 1, characterized in that The Ni-Co-V medium-entropy alloy based on direct energy deposition and stacking fault-L12 synergistic strengthening also contains a nano-L12 phase with a volume fraction of ≥5%, and the σ phase content is <1vol%.

4. The method for preparing a medium-entropy alloy based on additive manufacturing according to claim 1, characterized in that: In step 1, a plasma rotating electrode atomization method is used to prepare a pre-alloyed powder with a particle size of 53-106 um, an oxygen content of <200 ppm, and a sphericity of >0.

9.

5. The method for preparing a medium-entropy alloy based on additive manufacturing according to claim 1, characterized in that: In step 2, the laser power is 600-1000W, the scanning speed is 500mm / min, and the interlayer cooling rate is >10^5K / s, which effectively inhibits the precipitation of σ phase.

6. A medium-entropy alloy prepared by a method for preparing a medium-entropy alloy based on additive manufacturing according to any one of claims 1 to 5, characterized in that: The material obtained by the above preparation method is a Ni-Co-V medium-entropy alloy based on direct energy deposition and stacking fault-L12 synergistic strengthening. The Ni-Co-V (atomic percentage) ternary system is adopted, and the stacking fault energy is regulated by the atomic size difference (Ni: 0.124nm, Co: 0.125nm, V: 0.132nm) to promote the formation of stacking fault structure; the alloy composition range is: 29wt%≤Ni≤34%, 33wt%≤Co≤38%, 27wt%≤V≤32%, O≤0.02%, N≤0.05wt%.

7. The medium entropy alloy according to claim 6, characterized in that: Microstructural characteristics: A high-density stacking fault network is formed with a stacking fault spacing of 10-50nm, and a nanoscale L12 ordered phase (size 20-500nm, volume fraction 5-15%) is precipitated in situ at its interface.

8. The medium entropy alloy according to claim 6, characterized in that: Mechanical performance indicators: tensile strength ≥1200MPa (≥200MPa higher than the cast state), elongation after fracture maintained at 25%, achieving synergistic improvement in strength and plasticity.

9. The medium entropy alloy according to any one of claims 6 to 8, characterized in that: The medium entropy alloy can be used in aerospace load-bearing components.

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