ODS / NiCoCr medium-entropy alloy and preparation method thereof, additive manufacturing process and printed piece

Abstract

The invention relates to the technical field of medium-entropy alloy additive manufacturing, in particular to an ODS / NiCoCr medium-entropy alloy, a preparation method of the ODS / NiCoCr medium-entropy alloy, an additive manufacturing process and a printed piece. The invention relates to a preparation method of an ODS / NiCoCr medium-entropy alloy. The preparation method comprises the following steps: carrying out resonance acoustic mixing on Y2O3 powder and NiCoCr medium-entropy alloy powder; the Y2O3 powder is added in batches; the resonance sound mixing comprises the following steps: the vibration frequency is 30-85 Hz, the acceleration is 3-100 g, and the vibration time is 80-160 min. According to the preparation method, the NiCoCr medium-entropy alloy powder and the Y2O3 particles are adopted, the ODS / NiCoCr medium-entropy alloy composite powder which is free of Y2O3 agglomeration and uniform in distribution is prepared through resonance sound mixing, the composite powder is spherical or nearly spherical and good in fluidity, and the uniformity and stability of powder laying in the SLM process can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of medium-entropy alloy additive manufacturing, and in particular to an ODS / NiCoCr medium-entropy alloy and a preparation method thereof, an additive manufacturing process and a printed part. Background Art

[0002] Medium entropy alloys (MEAs) have many excellent properties over traditional metal materials due to their unique composition design and optimized microstructure. In particular, NiCoCr medium entropy alloys with face-centered cubic (FCC) structure have become the representative of the MEA family due to their excellent mechanical properties and damage tolerance, excellent radiation resistance and corrosion resistance, and have attracted attention due to their extremely high fracture plasticity and unique deformation mechanism at low temperatures. Medium entropy alloys exhibit good physical and mechanical properties both at room temperature and low temperature. The alloys show excellent tensile strength and ductility combination in a wide temperature range (-196°℃ to 400°C), especially in low temperature environments. This property makes them have better application potential under extreme conditions. However, the high-temperature strength and plasticity of NiCoCr medium entropy alloys currently prepared by additive manufacturing technology are insufficient. Residual stress and microcracks are the key factors affecting the improvement of their high-temperature strength and plasticity, especially when the use temperature is ≥500°C, and higher environments (≥1000°C) hinder their further application.

[0003] Selective laser sintering (SLM) is the mainstream additive manufacturing process for metals and alloys. It prepares parts for engineering applications by printing layer by layer. This technology has the characteristics of rapid heating / cyclic cooling. The large temperature gradient and rapid cooling during the laser forming process lead to large stresses inside the alloy, especially for the single-phase structure and intrinsic characteristics of the crystal structure of medium-entropy alloys. The macroscopic manifestation of the SLM-formed NiCoCr medium-entropy alloy in the material is that the printed samples are usually distributed with a large number of defects such as cracks and pores, resulting in a serious lack of plasticity of the medium-entropy alloy in additive manufacturing.

[0004] Oxide dispersion strengthened (ODS) alloys are alloys that are dispersion strengthened by adding fine oxide particles. The strengthening mechanism is mainly attributed to the Hall-Petch effect, a large number of grain boundaries per unit volume, and the Orowan strengthening mechanism induced by the reinforcing particles. By adding nano-oxide particles, a nano-coherent interface structure is constructed in the ODS / alloy matrix, which will give the composite material a stronger interface bonding, significantly relieve stress, inhibit interface defects and microcracks, and enhance the alloy strengthening and toughening effect.

[0005] How to provide an ODS medium-entropy alloy suitable for additive manufacturing, improve the high-temperature strength and plasticity of the medium-entropy alloy, and broaden its operating temperature range is of great significance to the development of medium-entropy alloys.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] One object of the present invention is to provide a method for preparing an ODS / NiCoCr medium-entropy alloy, which can improve the distribution uniformity of nanoparticles therein, make them uniformly coated on the surface of the alloy matrix, and increase the proportion of near-spherical powder to meet the requirements of continuous powder laying, uniformity of powder bed thickness and continuous printing in the SLM process.

[0008] Another object of the present invention is to provide an ODS / NiCoCr medium entropy alloy prepared by the above preparation method.

[0009] Another object of the present invention is to provide an additive manufacturing process for ODS / NiCoCr medium entropy alloy and an additive manufacturing print obtained.

[0010] In order to achieve the above-mentioned object of the present invention, the present invention provides a method for preparing an ODS / NiCoCr medium entropy alloy, comprising the following steps:

[0011] Resonant acoustic mixing of Y2O3 powder and NiCoCr medium entropy alloy powder; the Y2O3 powder is added in batches;

[0012] The resonant sound mixing includes: a vibration frequency of 30 to 85 Hz, an acceleration of 3 g to 100 g, and a vibration time of 80 to 160 min.

[0013] In a specific embodiment of the present invention, a single resonant acoustic mixing is performed after each addition of the Y2O3 powder; the single resonant acoustic mixing includes a first stage and a second stage, the vibration frequency in the first stage is smaller than the vibration frequency in the second stage, the acceleration in the first stage is smaller than the acceleration in the second stage, and the vibration time in the first stage is smaller than the vibration time in the second stage.

[0014] In a specific embodiment of the present invention, in the first stage, the vibration frequency is 30-50 Hz, the acceleration is 3g-25g, and the vibration time is 3-8 min; in the second stage, the vibration frequency is 60-85 Hz, the acceleration is 40g-100g, and the vibration time is 10-70 min.

[0015] In a specific embodiment of the present invention, adjacent single resonance sound mixtures satisfy at least one of the following characteristics:

[0016] (1) The acceleration in the first stage of the subsequent single resonance sound mixing is greater than the acceleration in the first stage of the previous single resonance sound mixing;

[0017] (2) the acceleration in the second stage of the subsequent single resonance sound mixing is greater than the acceleration in the second stage of the preceding single resonance sound mixing;

[0018] (3) the vibration frequency in the second stage of the subsequent single resonance sound mixing is greater than the vibration frequency in the second stage of the previous single resonance sound mixing;

[0019] (4) The vibration time in the second stage of the subsequent single resonance sound mixing is greater than the vibration time in the second stage of the preceding single resonance sound mixing.

[0020] In a specific embodiment of the present invention, in the first stage of the first single resonance sound mixing, the vibration frequency is 30-50 Hz; in the second stage of the first single resonance sound mixing, the vibration frequency is 60-65 Hz.

[0021] In a specific embodiment of the present invention, the acceleration in the second stage of the first single resonance sound mixing is 40g to 50g. Further, the difference between the acceleration in the second stage of the subsequent single resonance sound mixing and the acceleration in the second stage of the previous single resonance sound mixing is ≥20g.

[0022] In a specific embodiment of the present invention, the Y2O3 powder is added at least three times.

[0023] In a specific embodiment of the present invention, the single addition amount of the Y2O3 powder is gradually increased. Further, 15% to 25% of the total amount of the Y2O3 powder is added for the first time, 25% to 35% of the total amount of the Y2O3 powder is added for the second time, and 45% to 55% of the total amount of the Y2O3 powder is added for the third time.

[0024] In a specific embodiment of the present invention, in the first stage of the first single resonant sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 3g-7g, and the vibration time is 3-8 min. In the second stage of the first single resonant sound mixing, the vibration frequency is 60-65 Hz, the acceleration is 40g-50g, and the vibration time is 10-20 min. In the first stage of the second single resonant sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 8g-12g, and the vibration time is 3-8 min. In the second stage of the second single resonant sound mixing, the vibration frequency is 65-75 Hz, the acceleration is 60g-80g, and the vibration time is 20-40 min. In the first stage of the third single resonant sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 13g-25g, and the vibration time is 3-8 min. In the second stage of the third single resonant sound mixing, the vibration frequency is 75-85 Hz, the acceleration is 90g-100g, and the vibration time is 50-70 min.

[0025] In a specific embodiment of the present invention, the Y2O3 powder and the NiCoCr medium entropy alloy powder are 0.1% to 2% and 98% to 99.9% respectively in terms of mass percentage.

[0026] In a specific embodiment of the present invention, the NiCoCr medium entropy alloy includes the following components in mass percentage: Co 30% to 35%, Cr 27% to 32%, W 2% to 4%, Re 0.1% to 1.5%, Nb 0.3% to 0.9%, Al 0.2% to 0.4%, Mn 0.3% to 0.5% and Ni balance.

[0027] In a specific embodiment of the present invention, the Y2O3 powder is nano-scale Y2O3 powder. Further, the particle size of the Y2O3 powder is 20-50 nm.

[0028] Another aspect of the present invention provides an ODS / NiCoCr medium entropy alloy prepared by any one of the above-mentioned methods for preparing an ODS / NiCoCr medium entropy alloy.

[0029] In a specific embodiment of the present invention, in the ODS / NiCoCr medium entropy alloy, spherical and near-spherical powders account for ≥95wt%, particle sizes of 23 to 65 μm account for ≥99wt%, and fluidity is ≤20s / 50g.

[0030] In a specific embodiment of the present invention, in the ODS / NiCoCr medium entropy alloy, Y2O3 is coated on the surface of the NiCoCr medium entropy alloy powder, the powder coating rate is ≥95%, and the coating thickness is 1 to 3 μm.

[0031] In another aspect, the present invention provides an additive manufacturing process for ODS / NiCoCr medium entropy alloys, comprising the following steps: selectively laser sintering any one of the above-mentioned ODS / NiCoCr medium entropy alloys to prepare a printed part;

[0032] The selective laser sintering includes: laser energy density of 60 to 110 J / mm 3 , the scanning speed is 1250~1400mm / s.

[0033] In a specific embodiment of the present invention, in the selective laser sintering, the layer thickness is 30-40 μm, the powder feeding multiple is 1.5-2 times, and the inclination angle of the printed part is 10°-20°.

[0034] Another aspect of the present invention provides an additively manufactured printed part, which is produced by any one of the additive manufacturing processes of the ODS / NiCoCr medium entropy alloy described above.

[0035] In a specific embodiment of the present invention, the density of the printed part is ≥99.5%.

[0036] In a specific embodiment of the present invention, the performance of the printed part satisfies at least one of the following characteristics:

[0037] (1) Room temperature performance: tensile strength R M 700~800MPa, yield strength R P0.2 400~450MPa, elongation A is 60%~65%; Vickers hardness is 220~320HV; maximum crack size is ≤50μm, crack volume ratio is ≤0.5%, and average residual tensile stress is 0.1~0.3MPa;

[0038] (2) 700℃ performance: tensile strength R M 500~600MPa, yield strength R P0.2 200~300MPa;

[0039] (3) 1100℃ performance: tensile strength R M 140~180MPa, yield strength R P0.2 It is 130-170MPa; under the condition of stress 20MPa, the creep rupture life exceeds 2000h; under the condition of stress 31MPa, the creep rupture life exceeds 1300h; under the condition of stress 41MPa, the creep rupture life exceeds 180h.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention uses NiCoCr medium entropy alloy powder and Y2O3 particles to prepare ODS / NiCoCr medium entropy alloy composite powder with no agglomeration and uniform distribution of Y2O3 by resonant acoustic mixing. The composite powder is spherical or nearly spherical, has good fluidity, and can improve the uniformity and stability of powder spreading during the SLM process;

[0042] (2) The present invention uses ODS / NiCoCr medium-entropy alloy composite powder for SLM. The composite powder spreading process is continuous, uniform, and free of jams. The powder bed is flat and has no wavy fluctuations. The thickness of the powder spreading layer is uniform and can be printed continuously. The printed parts have high density, uniform distribution of Y2O3 particles, no agglomeration, good interface bonding, and no cracks. The printed parts have the characteristics of small residual stress, low density of cracks and defects, excellent high-temperature strength and plasticity, good fatigue and creep resistance, high limit operating temperature, and long service life, which broadens its application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A cross-sectional view and a Y element distribution diagram of the ODS / NiCoCr medium entropy alloy composite powder provided in Example 1 of the present invention;

[0045] Figure 2 A cross-sectional view and a Y element distribution diagram of the ODS / NiCoCr medium entropy alloy composite powder provided in Example 4 of the present invention;

[0046] Figure 3 A cross-sectional view and a Y element distribution diagram of the ODS / NiCoCr medium entropy alloy composite powder provided in Example 5 of the present invention;

[0047] Figure 4 TEM image of a printout of the ODS / NiCoCr medium entropy alloy composite powder provided in Example 7 of the present invention;

[0048] Figure 5 The crack (a) and the unfused defect (b) of the ODS / NiCoCr medium entropy alloy print provided in Example 8 of the present invention;

[0049] Figure 6 A crack diagram of an ODS / NiCoCr medium entropy alloy print provided in Example 9 of the present invention;

[0050] Figure 7 This is a SEM image of the tensile fracture of the ODS / NiCoCr medium-entropy alloy print provided in Example 7 of the present invention at room temperature. DETAILED DESCRIPTION

[0051] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If the specific conditions are not indicated in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0052] In the description of the present invention, it should be noted that the terms “first”, “second” and “third” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0053] In the prior art, by adding nano-oxide particles, a nano-coherent interface structure is constructed in the ODS / alloy matrix, which will give the composite material a stronger interface bond, which can significantly reduce stress, inhibit interface defects and microcracks, and enhance the alloy toughening effect. Usually, the particle size of the reinforcing phase at the nano level will be more beneficial to the synergistic improvement of the strength and plasticity of the ODS alloy. The nanoscale ODS phase can reduce the probability of stress concentration and crack generation and expansion inside the reinforcing phase during the plastic deformation of the SLM alloy. Its size, quantity, distribution and interface structure are closely related to the toughening effect. However, due to the small size, large specific surface area and high activity of nano-oxide particles, when the addition amount is high or when the size of the reinforcing particles is reduced to a certain scale, under the action of the huge van der Waals force, agglomeration is likely to occur during the preparation of the composite powder, affecting the uniformity of the composite powder, and easily leading to stress concentration of the printed part and a high density of defects such as cracks, which will be detrimental to obtaining uniform microstructure and excellent mechanical properties.

[0054] In the traditional ball milling technology for preparing ODS / alloy composite powder, although ODS / alloy composite powder containing nanoparticles can be obtained, a small amount of nano ODS particles are still agglomerated after ball milling, which makes the composite material have poor plasticity. In addition, the ball milling method uses grinding balls as grinding media. The strong collision impact during the mixing process and the high energy generated will change the shape of the spherical particles of the alloy powder, destroy its surface morphology and sphericity, and make its fluidity worse. In addition, there are cases where alloy powder particles are welded together, and the number and size of irregularly shaped powders are increased. The control window of ball milling process parameters is extremely narrow, which reduces the quality and qualified rate of composite powders, the stability of powders is poor, and the product cost is increased. The poor sphericity and fluidity also directly affect the uniformity and stability of powder spreading during the SLM process, and ultimately lead to uneven metal melting in the scanning area and the formation of internal defects, such as unfused areas, unreacted reinforcement phase particles, pores and microcracks, etc., which reduce mechanical properties.

[0055] Based on this, the present invention provides a method for preparing an ODS / NiCoCr medium-entropy alloy, which adopts nano Y2O3 as dispersion-enhanced particles and utilizes the technology of resonant acoustic mixing to prepare an ODS / NiCoCr medium-entropy alloy composite powder with high coverage, sphericity and good flowability through coordinated regulation of resonant acoustic mixing and Y2O3 addition.

[0056] The present invention provides a method for preparing an ODS / NiCoCr medium entropy alloy, comprising the following steps:

[0057] The Y2O3 powder is resonantly acoustically mixed with the NiCoCr medium entropy alloy powder; the Y2O3 powder is added in batches;

[0058] The resonant sound mixing includes: a vibration frequency of 30 to 85 Hz, an acceleration of 3 g to 100 g, and a vibration time of 80 to 160 min.

[0059] The present invention coordinates the resonant acoustic mixing and Y2O3 addition mode, does not change the alloy powder morphology, and Y2O3 is not agglomerated and is evenly coated, and the prepared ODS / NiCoCr medium entropy alloy composite powder has high sphericity and good fluidity, and no medium pollution. The preparation process parameters of the composite powder of the present invention are easy to control, and the powder performance stability and consistency are good.

[0060] For example, in different embodiments, in the resonant acoustic mixing, the vibration frequency can be 30Hz, 35Hz, 40Hz, 45Hz, 50Hz, 55Hz, 60Hz, 65Hz, 70Hz, 75Hz, 80Hz or a range consisting of any two thereof, the acceleration can be 3g, 5g, 8g, 10g, 20g, 30g, 40g, 60g, 80g, 100g or a range consisting of any two thereof, and the vibration time can be 80min, 90min, 100min, 120min, 140min, 160min or a range consisting of any two thereof. Wherein, the g in acceleration refers to the acceleration due to gravity, g=9.8m / s 2 It should be noted that the italicized g in the present invention represents the acceleration due to gravity, so as to distinguish it from the mass unit (gram) g.

[0061] In actual operation, the Y2O3 powder can be subjected to ultrasonic dispersion treatment in anhydrous ethanol in advance, and then left to stand until the anhydrous ethanol evaporates to obtain uniformly dispersed Y2O3 powder. In the ultrasonic dispersion, the ultrasonic frequency can be 20 to 22 KHz, and the ultrasonic time can be 12 to 14 hours. Through the above ultrasonic dispersion treatment, it can be further ensured that the Y2O3 powder has no obvious agglomeration phenomenon.

[0062] In a specific embodiment of the present invention, a single resonant acoustic mixing is performed after each addition of Y2O3 powder; the single resonant acoustic mixing includes a first stage and a second stage, the vibration frequency in the first stage is smaller than the vibration frequency in the second stage, the acceleration in the first stage is smaller than the acceleration in the second stage, and the vibration time in the first stage is smaller than the vibration time in the second stage.

[0063] In a specific embodiment of the present invention, in the first stage, the vibration frequency is 30-50 Hz, the acceleration is 3g-25g, and the vibration time is 3-8 min; in the second stage, the vibration frequency is 60-85 Hz, the acceleration is 40g-100g, and the vibration time is 10-70 min.

[0064] For example, in different embodiments, in the first stage, the vibration frequency can be 30Hz, 35Hz, 40Hz, 45Hz, 50Hz or a range consisting of any two thereof, the acceleration can be 3g, 5g, 8g, 10g, 15g, 20g, 25g or a range consisting of any two thereof, and the vibration time can be 3min, 4min, 5min, 6min, 7min, 8min or a range consisting of any two thereof. In the second stage, the vibration frequency can be 60Hz, 65Hz, 70Hz, 75Hz, 80Hz, 85Hz or a range consisting of any two thereof, the acceleration can be 40g, 50g, 60g, 70g, 80g, 90g, 100g or a range consisting of any two thereof, and the vibration time can be 10min, 20min, 30min, 40min, 50min, 60min, 70min or a range consisting of any two thereof.

[0065] In a specific embodiment of the present invention, adjacent single resonance sound mixtures satisfy at least one of the following characteristics:

[0066] (1) The acceleration in the first stage of the subsequent single resonance sound mixing is greater than the acceleration in the first stage of the previous single resonance sound mixing;

[0067] (2) the acceleration in the second stage of the subsequent single resonance sound mixing is greater than the acceleration in the second stage of the preceding single resonance sound mixing;

[0068] (3) the vibration frequency in the second stage of the subsequent single resonance sound mixing is greater than the vibration frequency in the second stage of the previous single resonance sound mixing;

[0069] (4) The vibration time in the second stage of the subsequent single resonance sound mixing is greater than the vibration time in the second stage of the preceding single resonance sound mixing.

[0070] In the resonant acoustic mixing process, when the natural frequency of the mixed material is close to the frequency of the external device, the mixed material will resonate, the vibration amplitude will increase, and the material mixing effect will be better. As the material is added and the degree of mixing continues to change, the natural frequency of the mixed material changes. The present invention further improves the mixing and coating effects by adjusting the frequency, acceleration, vibration time, etc. of the resonant acoustic mixing equipment.

[0071] In a specific embodiment of the present invention, in the first stage of the first single resonance sound mixing, the vibration frequency is 30-50 Hz; in the second stage of the first single resonance sound mixing, the vibration frequency is 60-65 Hz.

[0072] In a specific embodiment of the present invention, the acceleration in the second stage of the first single resonance sound mixing is 40g to 50g. Further, the difference between the acceleration in the second stage of the subsequent single resonance sound mixing and the acceleration in the second stage of the previous single resonance sound mixing is ≥20g.

[0073] For example, in different embodiments, the difference between the acceleration in the second stage of the subsequent single resonant sound mixing and the acceleration in the second stage of the previous single resonant sound mixing can be 20g, 21g, 22g, 23g, 24g, 25g, 26g, 27g, 28g, 29g, 30g or a range consisting of any two of them.

[0074] In a specific embodiment of the present invention, Y2O3 powder is added at least three times, including but not limited to 3 times, 4 times, 5 times, etc.

[0075] In a specific embodiment of the present invention, the single addition amount of Y2O3 powder increases gradually. Further, 15% to 25% of the total amount of Y2O3 powder is added for the first time, 25% to 35% of the total amount of Y2O3 powder is added for the second time, and 45% to 55% of the total amount of Y2O3 powder is added for the third time.

[0076] For example, in different embodiments, 15%, 18%, 20%, 22%, 25% or any range consisting of two of the total amount of Y2O3 powder can be added for the first time; 25%, 28%, 30%, 32%, 35% or any range consisting of two of the total amount of Y2O3 powder can be added for the second time; 45%, 48%, 50%, 52%, 55% or any range consisting of two of the total amount of Y2O3 powder can be added for the third time.

[0077] Compared with other additive manufacturing processes, the SLM process has stricter requirements on powder sphericity, fluidity, surface quality and the particle size distribution range of the powder. Controlling the size of ODS enhanced particles at the nanoscale and achieving uniform distribution is the key to improving the strong plastic properties of SLM-molded ODS / medium entropy alloys. The SLM process uses a scraper to spread powder, and spherical or nearly spherical powders have good fluidity, the powder layer thickness can be thinner, and the high sphericity also ensures the rate stability of the powder spreading process, as well as the thickness uniformity and continuity of the powder bed, which is conducive to reducing the stress of the printed part and reducing defects such as cracks, thereby improving the dimensional accuracy and surface quality of the parts, obtaining high-density and uniform organization, and improving the surface quality and mechanical properties of the parts. Therefore, in the preparation process of the present invention, a method of gradually increasing the amount of Y2O3 added is adopted, and the parameters such as vibration frequency, acceleration, and mixing time in the resonant acoustic mixing are synchronously adjusted, so that the composite powder of the ODS / NiCoCr medium entropy alloy obtained simultaneously meets the requirements of narrow particle size distribution, high sphericity, good fluidity and high bulk density.

[0078] In a specific embodiment of the present invention, in the first stage of the first single resonant sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 3g-7g, and the vibration time is 3-8 min. In the second stage of the first single resonant sound mixing, the vibration frequency is 60-65 Hz, the acceleration is 40g-50g, and the vibration time is 10-20 min. In the first stage of the second single resonant sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 8g-12g, and the vibration time is 3-8 min. In the second stage of the second single resonant sound mixing, the vibration frequency is 65-75 Hz, the acceleration is 60g-80g, and the vibration time is 20-40 min. In the first stage of the third single resonant sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 13g-25g, and the vibration time is 3-8 min. In the second stage of the third single resonant sound mixing, the vibration frequency is 75-85 Hz, the acceleration is 90g-100g, and the vibration time is 50-70 min.

[0079] By adopting the above-mentioned resonant acoustic mixing treatment conditions, in the ODS / NiCoCr medium-entropy alloy composite powder obtained, Y2O3 is coated on the outer surface of the alloy powder, and the powder coverage rate is ≥95% (powder coverage rate: the ratio of the surface area of ​​the alloy powder coated with Y2O3 in the composite powder to the original surface area of ​​the alloy powder), the coating layer is uniform and continuous, and the thickness is 1 to 3 μm; the sphericity of the alloy powder is not changed, the proportion of spherical and near-spherical powder in the composite powder is ≥95wt%, the fluidity is good, and the requirements of the SLM process for powder fluidity are met.

[0080] In a specific embodiment of the present invention, after the resonant acoustic mixing, the process further includes: screening treatment to collect materials with a particle size of 25 to 53 μm.

[0081] Through screening, materials meeting the SLM process requirements are obtained. In the composite powder obtained by the preparation method of the present invention, the proportion of particles with a particle size of 25 to 53 μm is ≥ 90 wt%.

[0082] In a specific embodiment of the present invention, the Y2O3 powder and the NiCoCr medium entropy alloy powder are 0.1% to 2% and 98% to 99.9% respectively in terms of mass percentage.

[0083] For example, in different embodiments, the amount of Y2O3 powder can be 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2% or a range consisting of any two thereof, and the amount of entropy alloy powder in NiCoCr can be 98%, 98.2%, 98.5%, 98.8%, 99%, 99.2%, 99.5%, 99.9% or a range consisting of any two thereof, calculated by mass percentage.

[0084] In a specific embodiment of the present invention, the proportion of particles with a particle size of 21 to 60 μm in the NiCoCr medium entropy alloy powder is ≥ 99 wt %. Furthermore, the bulk density of the NiCoCr medium entropy alloy powder is ≥ 4.80 g / cm 3 , fluidity ≤16.3s / 50g.

[0085] In a specific embodiment of the present invention, the NiCoCr medium entropy alloy includes the following components in mass percentage: Co 30% to 35%, Cr 27% to 32%, W 2% to 4%, Re 0.1% to 1.5%, Nb 0.3% to 0.9%, Al 0.2% to 0.4%, Mn 0.3% to 0.5% and Ni balance.

[0086] In actual operation, the NiCoCr medium entropy alloy powder is prepared by conventional medium frequency induction melting and inert gas atomization method. The NiCoCr medium entropy alloy powder used in the specific embodiment of the present invention is prepared by this method, and the particle size, bulk density and fluidity meet the above requirements.

[0087] In a specific embodiment of the present invention, the Y2O3 powder is nano-scale Y2O3 powder. Further, the particle size of the Y2O3 powder is 20-50 nm.

[0088] For example, in different embodiments, the average particle size of the Y2O3 powder can be 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or a range consisting of any two thereof.

[0089] Another aspect of the present invention provides an ODS / NiCoCr medium-entropy alloy prepared by any one of the above-mentioned methods for preparing an ODS / NiCoCr medium-entropy alloy.

[0090] In a specific embodiment of the present invention, in the ODS / NiCoCr medium entropy alloy, spherical and near-spherical powders account for ≥95wt%, particle sizes of 23 to 65μm account for ≥99wt%, and fluidity is ≤24s / 50g, preferably ≤20s / 50g.

[0091] For example, in different embodiments, in the ODS / NiCoCr medium-entropy alloy, the proportion of spherical and near-spherical powder in the composite powder can be 95wt%, 96wt%, 97wt%, 98wt%, 99wt% or a range consisting of any two of them; the fluidity can be 20s / 50g, 19.5s / 50g, 19s / 50g, 18.5s / 50g, 18s / 50g, 17.5s / 50g, 17s / 50g, 16.5s / 50g, 16s / 50g, 15.5s / 50g, 15s / 50g or a range consisting of any two of them.

[0092] In a specific embodiment of the present invention, in the ODS / NiCoCr medium entropy alloy, Y2O3 is coated on the surface of the NiCoCr medium entropy alloy powder, the powder coating rate is ≥80%, preferably ≥95%, and the coating thickness is 1 to 3 μm.

[0093] For example, in different embodiments, in the ODS / NiCoCr medium-entropy alloy, the powder coverage rate can be 95%, 95.2%, 95.4%, 95.5%, 95.6%, 95.8%, 96%, 96.5%, 97% or a range composed of any two thereof, and the coating thickness can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3 μm or a range composed of any two thereof.

[0094] In another aspect, the present invention provides an additive manufacturing process for ODS / NiCoCr medium entropy alloys, comprising the following steps: selectively laser sintering any one of the above ODS / NiCoCr medium entropy alloys to prepare a printed part;

[0095] Selective laser sintering includes: laser energy density is 60~110J / mm 3 , the scanning speed is 1250~1400mm / s.

[0096] When the ODS / NiCoCr medium entropy alloy prepared by the present invention is used in selective laser sintering, the composite powder spreading process of the ODS / NiCoCr medium entropy alloy is continuous, uniform, and has no jamming, the spreading rate is ≥0.04m / s, the powder bed is flat and has no wavy fluctuations; the thickness of the powder layer is uniform, and the thickness error is ≤ + 5%.

[0097] For example, in the selective laser sintering, the laser energy density can be 60 J / mm 3 、70J / mm 3 、80J / mm 3 、90J / mm 3 、100J / mm 3 、110J / mm 3 Or the range of any two of them, preferably 80 to 90 J / mm 3 ; The scanning speed can be 1250mm / s, 1280mm / s, 1300mm / s, 1320mm / s, 1350mm / s, 1380mm / s, 1400mm / s or a range consisting of any two of them, preferably 1250-1350mm / s.

[0098] In combination with ODS / NiCoCr medium entropy alloy, the parameters of selective laser sintering can be adjusted to further ensure the density of the printed parts and avoid defects such as cracks.

[0099] In a specific embodiment of the present invention, in the selective laser sintering, the layer thickness is 30-40 μm, the powder feeding multiple is 1.5-2 times, and the inclination angle of the printed part is 10°-20°.

[0100] In a specific embodiment of the present invention, during the selective laser sintering, the substrate is preheated at a temperature of 100 to 150° C. In actual operation, during the printing process, the temperature gradient of the molded sample is 80 to 100° C. / mm.

[0101] Another aspect of the present invention provides an additively manufactured printed part, which is produced by using any one of the above-mentioned additive manufacturing processes of the ODS / NiCoCr medium entropy alloy.

[0102] In a specific embodiment of the present invention, the density of the printed part is ≥99.5%.

[0103] The Y2O3 particles in the printout are evenly distributed (Y:O is about 2:3 in energy spectrum analysis, molar ratio), no agglomeration is observed, and the ODS / NiCoCr interface is well bonded.

[0104] Y2O3 particles with an average diameter of 20 to 50 nm are evenly dispersed in the microstructure of the printed part, and the volume proportion of Y2O3 particles in the matrix is ​​≥0.5%.

[0105] In a specific embodiment of the present invention, the performance of the printed part satisfies at least one of the following characteristics:

[0106] (1) Room temperature performance: tensile strength R M 700~800MPa, yield strength R P0.2 400~450MPa, elongation A is 60%~65%; Vickers hardness is 220~320HV; maximum crack size is ≤50μm, crack volume ratio is ≤0.5%, and average residual tensile stress is 0.1~0.3MPa;

[0107] (2) 700℃ performance: tensile strength R M 500~600MPa, yield strength R P0.2 200~300MPa;

[0108] (3) 1100℃ performance: tensile strength R M 140~180MPa, yield strength R P02 It is 130-170MPa; under the condition of stress 20MPa, the creep rupture life exceeds 2000h; under the condition of stress 31MPa, the creep rupture life exceeds 1300h; under the condition of stress 41MPa, the creep rupture life exceeds 180h.

[0109] As in different embodiments, in the room temperature performance, the tensile strength R M It can be 700MPa, 720MPa, 750MPa, 780MPa, 800MPa or a range consisting of any two of them. The yield strength R P0.2 It can be 400MPa, 410MPa, 420MPa, 430MPa, 440MPa, 450MPa or a range consisting of any two thereof; the elongation A can be 60%, 61%, 62%, 63%, 64%, 65% or a range consisting of any two thereof; the Vickers hardness can be 220HV, 240HV, 260HV, 280HV, 300HV, 320HV or a range consisting of any two thereof.

[0110] For example, in different embodiments, the tensile strength R M It can be 500MPa, 520MPa, 550MPa, 580MPa, 600MPa or any two of them. The yield strength R P0.2 It may be 200 MPa, 220 MPa, 250 MPa, 280 MPa, 300 MPa or a range consisting of any two thereof.

[0111] For example, in different embodiments, the tensile strength R M It can be 140MPa, 150MPa, 160MPa, 170MPa, 180MPa or any two of them. The yield strength R P0.2 It can be a range of 130MPa, 140MPa, 150MPa, 160MPa, 170MPa or any two of them; under the condition of 1100℃ / 20MPa, the creep rupture life exceeds 2000h; under the condition of 1100℃ / 31MPa, the creep rupture life exceeds 1300h; under the condition of 1100℃ / 41MPa, the creep rupture life exceeds 180h.

[0112] The tensile strength and yield strength of the printed parts of the ODS / NiCoCr medium entropy alloy of the present invention at high temperature are significantly improved compared with the NiCoCr medium entropy alloy without adding Y2O3.

[0113] The improvement of the high-temperature yield strength of the printed parts of the present invention is mainly contributed by dislocation strengthening (σb), second phase strengthening (σp) and grain boundary strengthening (σD), wherein each accounts for approximately: dislocation strengthening (σb) 40% to 50%, second phase strengthening (σp) 30% to 40% and grain boundary strengthening (σD) 10% to 30%. After adding Y2O3 particles, the proportion of dislocation strengthening is reduced by more than 10%, and the proportion of second phase strengthening is increased by more than 30%, which significantly reduces residual stress and inhibits the occurrence of cracks.

[0114] Compared with the NiCoCr medium entropy alloy, the maximum crack size of the printed part of the present invention is reduced by more than 20 μm, the crack volume density is reduced by more than 40%, and the average residual tensile stress is reduced by more than 30%.

[0115] The printed parts obtained by SLM using the ODS / NiCoCr medium entropy alloy of the present invention can be used as high-temperature components of a supersonic aircraft turbine combustion chamber. The service life of the parts is increased by more than 300 times compared with that without adding Y2O3, and the maximum use temperature of the parts is increased from 900°C to 1100°C. Under the condition of 1100°C / 20MPa, the creep life is increased by more than 300 times; under the condition of 1100°C / 31MPa, the creep life is increased by more than 1000 times.

[0116] Example 1

[0117] This embodiment provides a method for preparing ODS / NiCoCr medium entropy alloy composite powder, comprising the following steps:

[0118] (1) Take 10g of Y2O3 powder with an average diameter of 30nm and put it into a 200mL beaker. Slowly pour 100mL of anhydrous ethanol along the wall of the beaker and stir it continuously with a glass rod during the pouring process. Use ultrasonic dispersion equipment to disperse it. The ultrasonic frequency is 20KHz. The uniformity of the solution is ensured during the ultrasonic process. The ultrasonic time is 12h. Let it stand and wait for the anhydrous ethanol to evaporate to obtain a uniformly dispersed Y2O3 powder.

[0119] (2) Resonant sound mixing:

[0120] ① Take 2g of ultrasonically dispersed Y2O3 powder and pour it into a resonant acoustic mixing cup containing 990g of NiCoCr medium entropy alloy powder. The frequency is 40Hz and the acceleration is 5g (g = 9.8m / s 2 ), the resonant sound mixing time is 5 minutes; continue mixing, adjust the frequency to 63Hz, the acceleration to 46g, and the resonant sound mixing time to 15 minutes;

[0121] ② Continue to take 3g of ultrasonically dispersed Y2O3 powder and add it to the above resonant acoustic mixing cup, with a frequency of 40Hz, an acceleration of 8g, and a resonant acoustic mixing time of 5min; continue mixing, adjust the frequency to 70Hz, the acceleration to 70g, and the resonant acoustic mixing time to 30min;

[0122] ③ Continue to take 5g of ultrasonically dispersed Y2O3 powder and add it to the above-mentioned resonant acoustic mixing cup, with a frequency of 40Hz, an acceleration of 15g, and a resonant acoustic mixing time of 8min; continue mixing, adjust the frequency to 80Hz, the acceleration to 95g, and the resonant acoustic mixing time to 60min to obtain a better coated composite powder.

[0123] (3) The composite powder obtained in step (2) is sieved using a vibrating screen with a mesh diameter of 25 μm and 53 μm, respectively, and the powder with a mesh diameter of 25 to 53 μm is taken as qualified powder, and the qualified powder is ≥ 90% (the mass of the qualified powder accounts for the proportion of the total amount of the sieved powder).

[0124] Scanning electron microscopy (SEM) analysis revealed Figure 1 The cross-sectional view and Y element distribution diagram of the ODS / NiCoCr medium entropy alloy composite powder provided in this embodiment. It can be seen from the figure that nano Y2O3 is coated on the outer surface of the alloy powder, the powder coating rate is about 96%, the coating layer is uniform and continuous, and the thickness is about 2μm; the spherical and near-spherical powders in the composite powder account for ≥95wt%, the powder with a particle size of 30μm to 50μm accounts for about 98.5wt%, and the fluidity is 18.7s / 50g.

[0125] Embodiments 2 to 6

[0126] This embodiment provides a method for preparing ODS / NiCoCr medium entropy alloy composite powder, referring to Example 1, except that the parameters of the resonant acoustic mixing in step (2) are different.

[0127] The parameters of the resonant sound mixing in step (2) of Examples 2 to 6 are shown in Table 1.

[0128] Table 1 Parameters of resonant sound mixing in step (2) of Examples 2 to 6

[0129]

[0130] In the composite powder prepared in Example 2, nano Y2O3 is coated on the outer surface of the alloy powder, the powder coverage rate is about 82%, the coating layer is uniform and continuous, and the thickness is about 2μm; the spherical and near-spherical powders in the composite powder account for about 80wt%, the powder with a particle size of 30μm to 50μm accounts for about 80wt%, and the fluidity is 21.1 / 50g.

[0131] In the composite powder prepared in Example 3, nano Y2O3 is coated on the outer surface of the alloy powder, the powder coverage rate is about 84%, the coating layer is uniform and continuous, and the thickness is about 2μm; the spherical and near-spherical powders account for about 85wt% of the composite powder, the powder with a particle size of 30μm to 50μm accounts for about 82wt%, and the fluidity is 19.3s / 50g.

[0132] The SEM of the composite powder obtained in Example 4 is as follows: Figure 2 As shown, nano Y2O3 is coated on the outer surface of the alloy powder, the powder coating rate is about 85%, the coating layer is discontinuous, and the coating layer thickness difference is ≥ + 3μm; the powder with a particle size of 30μm to 50μm accounts for ≥78.5wt%, and the fluidity is 23.7s / 50g.

[0133] The SEM of the composite powder obtained in Example 5 is as follows: Figure 3 As shown, nano Y2O3 is coated on the outer surface of the alloy powder, the powder coating rate is about 80%, the coating layer is uneven, and the coating layer thickness difference is ≥ + 3μm; composite powder has no fluidity.

[0134] Among the composite powders prepared in Example 6, qualified powder accounts for about 55%; nano Y2O3 is coated on the outer surface of the alloy powder, and the powder coating rate is about 40%. The Y2O3 coated on the outer surface of the alloy powder is agglomerated, the coating layer is discontinuous and uneven in thickness, and the local thickness is ≥5μm; the powder has no fluidity.

[0135] Example 7

[0136] This embodiment provides an additive manufacturing process for an ODS / NiCoCr medium entropy alloy, comprising the following steps:

[0137] (1) The ODS / NiCoCr medium-entropy alloy composite powder prepared in Example 1 was dried in a vacuum drying oven at a temperature of 120° C. for 2 h.

[0138] (2) Add 3kg of dried ODS / NiCoCr medium entropy alloy composite powder to the feed chamber, use 316 stainless steel substrate, control the printing environment temperature to 25°C, humidity to 12.0RH%, use argon as protective gas, and keep the oxygen content below 1000ppm. Start printing under the conditions of filter pressure difference of 1.5mbar, fan flow rate of 3.45m / s, chamber pressure of 34.1mbar, and substrate preheating temperature of 120°C; printing process parameters are: laser energy density of 85J / mm 3 , scanning speed 1300mm / s, layer thickness 30μm, powder feeding multiple is 1.6 times, and the printed part tilt angle is 15°.

[0139] In the additive manufacturing process of this embodiment, the composite powder spreading process is continuous, uniform, and has no jamming. The spreading rate is 0.05 m / s, and the powder bed is flat without wavy fluctuations. The thickness of the powder layer is uniform, and the thickness error is about + 3%.

[0140] The printed part prepared in this embodiment was tested, and the density was ≥99.5%. The Y2O3 particles in the printed part were evenly distributed (Y:O was about 2:3 in the energy spectrum analysis, molar ratio), no agglomeration was observed, the interface was well bonded, and there were no cracks. Figure 4 The TEM image of the printed part provided in this embodiment shows that Y2O3 particles with a diameter of 49.82nm are dispersed and evenly distributed. In the printed part, Y2O3 accounts for 0.53% of the volume in the matrix; the maximum crack size is ≤35μm, the crack volume accounts for ≤0.3%, and the average residual tensile stress is 0.15MPa.

[0141] Example 8

[0142] This embodiment provides an additive manufacturing process for an ODS / NiCoCr medium entropy alloy, with reference to Embodiment 7, except that the printing process parameters in step (2) are different.

[0143] Printing process parameters of this embodiment: laser energy density is 60J / mm 3 , scanning speed 1400mm / s, layer thickness 30μm, powder feeding multiple is 1.6 times, and the printed part tilt angle is 15°.

[0144] The printed part obtained in this embodiment was tested and found to have a density of 96.5%. No obvious dissolution or precipitation of Y2O3 particles occurred in the printed part, and no cracks or unfused defects were found. Figure 5According to the microstructure analysis of the printed part, the maximum crack size is about 55μm, the crack volume accounts for 3%, and the average residual tensile stress is 1.5MPa.

[0145] Example 9

[0146] This embodiment provides an additive manufacturing process for an ODS / NiCoCr medium entropy alloy, with reference to Embodiment 7, except that the printing process parameters in step (2) are different.

[0147] Printing process parameters of this embodiment: laser energy density is 110J / mm 3 , scanning speed 1400mm / s, layer thickness 30μm, powder feeding multiple is 1.6 times, and the printed part tilt angle is 15°.

[0148] The printed part obtained in this embodiment was tested and the density was 97.5%. The ODS / NiCoCr interface in the printed part was not well bonded. The laser energy density was too high and the temperature gradient was large, resulting in a large number of cracks inside the Y2O3 and at the ODS / NiCoCr interface. Figure 6 According to the microstructure analysis of the printed part, the maximum crack size is about 75μm, the crack volume accounts for 5%, and the average residual tensile stress is 3.5MPa.

[0149] Embodiments 10 to 14

[0150] This embodiment provides an additive manufacturing process for ODS / NiCoCr medium entropy alloy, with reference to Example 7, except that Examples 10 to 14 respectively use the ODS / NiCoCr medium entropy alloy composite powders prepared in Examples 2 to 6 to replace the ODS / NiCoCr medium entropy alloy composite powders prepared in Example 1 used in Example 7.

[0151] In the additive manufacturing of Example 10, the composite powder spreading process was continuous and without any jamming, and the powder bed was flat with slight wavy undulations; the thickness of the powder layer was uneven, with a thickness error of approximately + 7%, can print continuously.

[0152] In the additive manufacturing of Example 11, the composite powder spreading process was continuous and smooth, and the powder bed was flat without obvious undulations. The thickness of the powder layer was uneven, with a thickness error of approximately + 5%, can print continuously.

[0153] In the additive manufacturing of Example 12, the composite powder spreading process was discontinuous and there were jams, the powder bed was uneven and wavy; the thickness of the powder layer was uneven, and the thickness error was about + 15%, cannot print continuously.

[0154] In the additive manufacturing of Example 13, the composite powder spreading process was discontinuous and there were jams, the powder bed was uneven and wavy; the thickness of the powder layer was uneven, and the thickness error was about + 10%, cannot print continuously.

[0155] In the additive manufacturing of Example 14, the composite powder spreading process was discontinuous and had jams, the powder bed was uneven and had wavy undulations, and continuous printing was impossible.

[0156] Comparative Example 1

[0157] Comparative Example 1 provides a method for preparing ODS / NiCoCr medium entropy alloy composite powder, referring to Example 1, except that: step (2) is different.

[0158] Step (2) of Comparative Example 1 comprises: taking 10 g of ultrasonically dispersed Y2O3 powder and pouring it into a resonant acoustic mixing cup containing 990 g of NiCoCr medium entropy alloy powder at once, with a frequency of 40 Hz and an acceleration of 50 g (g = 9.8 m / s 2 ), and the resonant acoustic mixing time was 90 min.

[0159] The qualified powder is about 45% in the ODS / NiCoCr medium entropy alloy composite powder prepared in comparative example 1. There are more agglomerated Y2O3 particles in the +53μm powder; the Y2O3 coated on the outer surface of the alloy powder is unevenly dispersed, the powder coverage is about 50%, the coating layer is discontinuous, the spherical and near-spherical powder accounts for about 55wt% in the composite powder, and the powder has no fluidity.

[0160] Referring to the additive manufacturing process of Example 7, the composite powder of Comparative Example 1 cannot complete the SLM powder spreading process and is not printable.

[0161] Comparative Example 2

[0162] The NiCoCr medium entropy alloy powder is the same as the NiCoCr medium entropy alloy powder in Example 1.

[0163] Specifically, it includes the following components in mass percentage: Co 32.6%, Cr 31.8%, W 3.2%, Re 0.12%, Nb 0.50%, Al 0.24%, Mn 0.3%, and Ni balance.

[0164] The particle size of 26-53μm accounts for ≥99.5wt%, the spherical and nearly spherical powder accounts for about 97wt%, and the bulk density is ≥4.85g / cm 3 , fluidity ≤15.8s / 50g.

[0165] The additive manufacturing was performed using NiCoCr medium entropy alloy powder, referring to the additive manufacturing process of Example 7, except that some process parameters were different. The printing process parameters of Comparative Example 2 were: laser energy density was 61 J / mm 3 , scanning speed 1260mm / s, layer thickness 30μm, scanning spacing 0.05μm.

[0166] According to the microstructure analysis of the printed parts, the maximum crack size is about 75μm, the crack volume accounts for 0.7%, and the average residual tensile stress is 0.85MPa.

[0167] Experimental example

[0168] The properties of the printed parts prepared in Examples 7 to 9 and Comparative Example 2 were tested. The test results are shown in Tables 2 and 3.

[0169] Table 2 Room temperature performance test results of different printed parts

[0170] serial number Vickers hardness / HV <![CDATA[Tensile strength R M / MPa]]> <![CDATA[Yield strength R P0.2 / MPa]]> Elongation A / % Example 7 280 750 430 60 Example 8 / 597 395 / Example 9 / 550 356 / Comparative Example 2 / 723 405 /

[0171] Table 3 High temperature performance test results of the printed parts of Example 7 and Comparative Example 2

[0172]

[0173] The study found that the contribution rates of the yield strength of the printed parts obtained in Example 7 are: dislocation strengthening (σb) 45%, second phase strengthening (σp) 35%, and grain boundary strengthening (σD) 18%. After adding Y2O3, the proportion of dislocation strengthening was reduced by more than 15%, and the proportion of second phase strengthening was increased by more than 28%.

[0174] Compared with the NiCoCr medium entropy alloy print of Comparative Example 2, the maximum crack size of the print of Example 7 is reduced by 22 μm, the crack volume density is reduced by 42%, and the average residual tensile stress is reduced by 33%; at 1100°C, the tensile strength and yield strength of the print of Example 7 are increased by more than 10% and 25% respectively compared with the print of Comparative Example 2.

[0175] Further analysis was performed on the tensile fracture of the printed part of Example 7. Figure 7 The SEM image of the tensile fracture at room temperature of the print provided in Example 7 shows that the fracture starts approximately in the middle of the geometric size of the tensile specimen and ends with shear tearing at the edge of the specimen. The fracture surface shows a typical plastic fracture mode, with microscopic voids nucleating, growing, and aggregating until fracture, forming many dense and deep equiaxed dimples, indicating that the ODS / NiCoCr medium entropy alloy of the present invention has good plasticity.

[0176] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ODS / NiCoCr medium entropy alloy, characterized in that: The steps include: Resonant acoustic mixing of Y2O3 powder and NiCoCr medium entropy alloy powder; the Y2O3 powder is added in batches; The resonant sound mixing includes: a vibration frequency of 30 to 85 Hz, an acceleration of 3 g to 100 g, and a vibration time of 80 to 160 min.

2. The method for preparing the ODS / NiCoCr medium entropy alloy according to claim 1, characterized in that: After each addition of the Y2O3 powder, a single resonant acoustic mixing was performed; The single resonance acoustic mixing includes a first stage and a second stage, the vibration frequency in the first stage is smaller than the vibration frequency in the second stage, the acceleration in the first stage is smaller than the acceleration in the second stage, and the vibration time in the first stage is smaller than the vibration time in the second stage; Preferably, in the first stage, the vibration frequency is 30-50 Hz, the acceleration is 3g-25g, and the vibration time is 3-8 min; in the second stage, the vibration frequency is 60-85 Hz, the acceleration is 40g-100g, and the vibration time is 10-70 min.

3. The method for preparing the ODS / NiCoCr medium entropy alloy according to claim 2, characterized in that: Adjacent single resonance sound mixtures satisfy at least one of the following characteristics: (1) The acceleration in the first stage of the subsequent single resonance sound mixing is greater than the acceleration in the first stage of the previous single resonance sound mixing; (2) the acceleration in the second stage of the subsequent single resonance sound mixing is greater than the acceleration in the second stage of the preceding single resonance sound mixing; (3) the vibration frequency in the second stage of the subsequent single resonance sound mixing is greater than the vibration frequency in the second stage of the previous single resonance sound mixing; (4) The vibration time in the second stage of the subsequent single resonance sound mixing is greater than the vibration time in the second stage of the preceding single resonance sound mixing.

4. The method for preparing the ODS / NiCoCr medium entropy alloy according to claim 2, characterized in that: In the first stage of the first single resonance sound mixing, the vibration frequency is 30 to 50 Hz; in the second stage of the first single resonance sound mixing, the vibration frequency is 60 to 65 Hz; In the second stage of the first single resonance acoustic mixing, the acceleration is 40g to 50g; Preferably, the difference between the acceleration in the second stage of the subsequent single resonance sound mixing and the acceleration in the second stage of the preceding single resonance sound mixing is ≥20 g.

5. The method for preparing the ODS / NiCoCr medium entropy alloy according to claim 2, characterized in that: The Y2O3 powder is added at least three times; Preferably, the single addition amount of the Y2O3 powder increases gradually; Preferably, 15% to 25% of the total amount of the Y2O3 powder is added for the first time, 25% to 35% of the total amount of the Y2O3 powder is added for the second time, and 45% to 55% of the total amount of the Y2O3 powder is added for the third time.

6. The method for preparing the ODS / NiCoCr medium entropy alloy according to claim 5, characterized in that: In the first stage of the first single resonance sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 3g-7g, and the vibration time is 3-8 minutes. In the second stage of the first single resonance sound mixing, the vibration frequency is 60-65 Hz, the acceleration is 40g-50g, and the vibration time is 10-20 minutes. In the first stage of the second single resonance sound mixing, the vibration frequency is 30-50 Hz, the acceleration is 8g-12g, and the vibration time is 3-8 minutes. In the second stage of the second single resonance sound mixing, the vibration frequency is 65-75 Hz, the acceleration is 60g-80g, and the vibration time is 20-40 minutes. In the first stage of the third single resonance sound mixing, the vibration frequency is 30-50Hz, the acceleration is 13g-25g, and the vibration time is 3-8min. In the second stage of the third single resonance sound mixing, the vibration frequency is 75-85Hz, the acceleration is 90g-100g, and the vibration time is 50-70min.

7. The method for preparing the ODS / NiCoCr medium entropy alloy according to claim 1, characterized in that: In terms of mass percentage, the Y2O3 powder and the NiCoCr medium entropy alloy powder are 0.1% to 2% and 98% to 99.9% respectively; Preferably, the NiCoCr medium entropy alloy comprises the following components in mass percentage: Co 30% to 35%, Cr 27% to 32%, W 2% to 4%, Re 0.1% to 1.5%, Nb 0.3% to 0.9%, Al 0.2% to 0.4%, Mn 0.3% to 0.5% and Ni balance; Preferably, the Y2O3 powder is nano-scale Y2O3 powder.

8. An ODS / NiCoCr medium entropy alloy, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7; Preferably, in the ODS / NiCoCr medium entropy alloy, Y2O3 is coated on the surface of the NiCoCr medium entropy alloy powder, and the powder coating rate is ≥80%; More preferably, in the ODS / NiCoCr medium entropy alloy, Y2O3 is coated on the surface of the NiCoCr medium entropy alloy powder, the powder coating rate is ≥95%, and the coating thickness is 1 to 3 μm; Preferably, the fluidity of the entropy alloy in ODS / NiCoCr is ≤24s / 50g; More preferably, the fluidity of the entropy alloy in ODS / NiCoCr is ≤20s / 50g.

9. An additive manufacturing process, characterized in that: The method comprises the following steps: selectively laser sintering the ODS / NiCoCr medium entropy alloy according to claim 8 to prepare a printed part; The selective laser sintering includes: laser energy density of 60 to 110 J / mm 3 , scanning speed is 1250~1400mm / s; Preferably, in the selective laser sintering, the layer thickness is 30-40 μm, the powder feeding multiple is 1.5-2 times, and the inclination angle of the printed part is 10°-20°.

10. An additively manufactured print, characterized in that: It is manufactured by the additive manufacturing process described in claim 9.

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