A Co-Cr-Fe-Ni system ODS high entropy alloy and its preparation method and application

Abstract

The present invention proposes a Co‑Cr‑Fe‑Ni based ODS high entropy alloy and its preparation method and application, which belong to the technical field of metal-based composite materials. The Co‑Cr‑Fe‑Ni based ODS high entropy alloy is obtained by SLM forming via a mixed raw material powder consisting of Co‑Cr‑Fe‑Ni high entropy pre-alloyed powder, Fe‑Y powder and TiO2 powder; in the raw materials, the ratio of Fe‑Y powder is 0.7-2.0wt.%, the ratio of TiO2 powder is 0.8-2.4wt.%, and the ratio of Co‑Cr‑Fe‑Ni high entropy pre-alloyed powder is 95.6-98.5wt.%. The present invention uses high entropy pre-alloyed powder and additive manufacturing containing Y pre-alloyed powder to prepare an ODS high entropy alloy with a relatively ideal microstructure more quickly and efficiently, which is expected to be widely used in the field of metal-based composite materials, especially the field of ODS alloys.

Description

Technical Field

[0001] The present invention relates to the technical field of metal matrix composite materials, and in particular to a Co-Cr-Fe-Ni series ODS high entropy alloy and a preparation method and application thereof. Background Art

[0002] High-entropy alloys (HEAs) are a new type of multi-element alloy with broad application prospects in aerospace, new energy, and biomedicine. FCC HEAs, one of the earliest developed and extensively researched systems, exhibit excellent plasticity, toughness, thermal stability, and good oxidation resistance. However, their development and application are limited by their relatively low hardness and strength at room temperature.

[0003] Oxide dispersion strengthening (ODS) is an important method for strengthening metals. ODS alloys contain highly thermodynamically stable, densely packed oxide particles (such as Y2O3) measuring just a few nanometers or tens of nanometers. These particles enhance the material's strength by pinning grain boundaries and dislocations. Incorporating ODS design concepts into FCC high-entropy alloys (FCA) is expected to overcome their room-temperature strength and hardness deficiencies, resulting in superior overall mechanical properties.

[0004] Currently, ODS alloys are mostly prepared through mechanical alloying (MA). This process utilizes the prolonged collision and compression of grinding media (typically grinding balls) with powders contained in a grinding vessel, causing atomic-level fragmentation and re-welding of the powders. This promotes the interdiffusion and solid solution of the elements within the powders to form a supersaturated solid solution. Subsequently, through solidification, forming, and heat treatment, nano-oxide particles are precipitated in situ from the matrix to form the ODS alloy. During the ball milling process, due to the solid-phase diffusion of atoms, the formation of a supersaturated solid solution typically requires dozens or even hundreds of hours. Furthermore, the subsequent solidification process is generally incapable of directly producing complex components. Consequently, the MA process is characterized by long process times, low efficiency, contamination, and limited product size and shape, significantly hindering the production and application of ODS alloys.

[0005] With the rise of additive manufacturing technology, the preparation and forming of metal materials have ushered in new breakthroughs. Selective Laser Melting (SLM) is one of the most widely used and most promising technologies in the field of additive manufacturing. The main process flow of this technology can be divided into two stages: data processing and processing and manufacturing. The main task of the data processing stage is to use computer software to complete the modeling of the parts to be processed. In the processing and manufacturing stage, a thin layer of powder is first evenly laid on the forming substrate and a high-energy laser beam is used to scan the powder according to the specified path and process parameters. Then the forming substrate is lowered by one layer and the powder laying and laser scanning are repeated to make the metal accumulate layer by layer, and finally the structural parts are obtained. Compared with traditional methods such as MA, this technology can obtain complex components with high precision, good surface quality and excellent mechanical properties, which greatly improves work efficiency. Therefore, the present invention provides a method for preparing FCC structure Co-Cr-Fe-Ni ODS high entropy alloy by SLM. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention aims to provide a method for preparing an FCC-structured Co-Cr-Fe-Ni ODS high-entropy alloy using SLM. This method uses Co-Cr-Fe-Ni high-entropy pre-alloyed powder, Fe-Y pre-alloyed powder, and nano-TiO2 powder as raw materials. After thorough mixing, the material is printed using SLM technology to form a bulk material, which is then annealed. This method, which utilizes SLM technology to prepare ODS high-entropy alloys, is expected to provide experimental evidence and application foundation for the efficient manufacture of ODS high-entropy alloys.

[0007] The technical solution of the present invention is achieved as follows: The present invention provides a Co-Cr-Fe-Ni based ODS high entropy alloy, wherein the Co-Cr-Fe-Ni based ODS high entropy alloy is obtained by SLM forming a mixed raw material powder consisting of Co-Cr-Fe-Ni high entropy pre-alloyed powder, Fe-Y powder and TiO2 powder;

[0008] The elements Co, Cr, Fe and Ni in the Co-Cr-Fe-Ni high entropy pre-alloyed powder are in equiatomic ratios;

[0009] Among the raw materials, the proportion of Fe-Y powder is 0.7-2.0wt.%, the proportion of TiO2 powder is 0.8-2.4wt.%, and the proportion of Co-Cr-Fe-Ni high entropy pre-alloyed powder is 95.6-98.5wt.%.

[0010] On the basis of the above technical solution, preferably, in the raw materials, the ratio of Fe-Y powder is 1.0wt.%, the ratio of TiO2 powder is 1.2wt.%, and the ratio of Co-Cr-Fe-Ni high entropy pre-alloyed powder is 97.8wt.%.

[0011] Based on the above technical solution, preferably, the content of Y element in the Fe-Y powder is 6.0 wt.%.

[0012] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned Co-Cr-Fe-Ni based ODS high entropy alloy, comprising the following steps:

[0013] Step S1: Co-Cr-Fe-Ni high entropy pre-alloyed powder, Fe-Y powder and TiO2 powder are used as raw materials and mixed to obtain a mixed powder;

[0014] Step S2: The mixed powder is formed by SLM printing and annealing to obtain the Co-Cr-Fe-Ni based ODS high entropy alloy.

[0015] On the basis of the above technical solution, preferably, in step S2, the annealing gas is an inert gas, and the inert gas is selected from at least one of argon, helium, and neon.

[0016] Based on the above technical solution, preferably, the annealing temperature is 800-950° C., and the annealing time is 1-2 hours.

[0017] On the basis of the above technical solution, preferably, the annealing temperature is independently selected from any value of 800°C, 820°C, 850°C, 880°C, 900°C, 950°C or a range between any two of the above values.

[0018] On the basis of the above technical solution, preferably, the annealing time is independently selected from any value of 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, or a range between any two of the above values.

[0019] Based on the above technical solution, preferably, the heating rate of the annealing is 10-15°C / min.

[0020] On the basis of the above technical solution, preferably, in step S2, the mixed powder is dried before SLM printing.

[0021] On the basis of the above technical solution, preferably, the drying temperature is 120-130° C., and the drying time is 20-30 h.

[0022] On the basis of the above technical solution, preferably, in step S2, the process parameters of the SLM printing are set as follows: the powder layer thickness is a fixed value of 40 μm, the scanning mode is a layer-by-layer rotation of 67°, the laser power is 200-300 W, the scanning spacing is 70-80 μm, and the scanning speed is 600-1200 mm / s.

[0023] On the basis of the above technical solution, preferably, in step S2, the substrate formed by SLM printing is a stainless steel substrate, and the size of the substrate is 100 mm×100 mm.

[0024] Based on the above technical solution, preferably, the substrate is preheated to 120° C. before printing, and then vacuumed and filled with argon for protection, and formal printing is started after the oxygen content drops below 0.01%.

[0025] On the basis of the above technical solution, preferably, in step S1, a planetary ball mill is used for mixing, and no grinding balls or process control agents are added to the ball mill.

[0026] On the basis of the above technical solution, preferably, the planetary ball mill has a rotation speed of 200 rpm to 250 rpm and an operating time of 4 to 6 hours.

[0027] On the basis of the above technical solution, preferably, the protective gas during the mixing is argon, and the amount of the argon is 0.1 MPa to 0.15 MPa.

[0028] Based on the above technical solution, preferably, in step S1, during the ball milling, the ball mill jar is sealed and vacuumed using a vacuum pump, and then filled with 0.1 MPa argon as a protective gas without adding any grinding balls or process control agents.

[0029] According to another aspect of the present invention, there is provided an application of the above-mentioned Co-Cr-Fe-Ni based ODS high entropy alloy and the Co-Cr-Fe-Ni based ODS high entropy alloy prepared by the above-mentioned preparation method in the fields of metal-based composite materials, aerospace, new energy, and biomedicine.

[0030] As an optional embodiment, the present invention is implemented by the following technical solutions:

[0031] A method for preparing a Co-Cr-Fe-Ni based ODS high entropy alloy comprises the following steps:

[0032] S1. preparing a mixture of raw material powders of Co-Cr-Fe-Ni based ODS high entropy alloy;

[0033] S2. The mixed powder is subjected to SLM forming to prepare a Co-Cr-Fe-Ni based ODS high entropy alloy bulk material, and the bulk material is subjected to annealing heat treatment to obtain a Co-Cr-Fe-Ni based ODS high entropy alloy.

[0034] Optionally, in step S2, before performing the SLM forming technology, the mixed powder is first placed in a vacuum drying oven and kept warm at 120°C for 20 hours, and then the mixed powder is taken out and poured into the powder feeding bin of the printing device and flattened.

[0035] Optionally, in step S2, the substrate of the printing device uses a stainless steel substrate with a substrate size of 100 mm × 100 mm. After the substrate is installed in the printing device, it is preheated to 120° C., and then the printing device is vacuumed and filled with high-purity argon as a protective gas. Printing is officially started after the oxygen content in the device drops below 0.01%.

[0036] Optionally, in step S2, the basic process parameters of the SLM forming technology are set as follows: the powder layer thickness is a fixed value of 40 μm, a scanning strategy of rotating 67° layer by layer is adopted, the laser power is 200-300 W, the scanning spacing is 70-80 μm, and the scanning speed is 600-1200 mm / s.

[0037] On the one hand, the present invention utilizes a laser heat source to completely melt the mixed powder to form a high-entropy alloy system rich in Y, Ti, and O. A portion of the Y, Ti, and O elements directly react in situ during the solidification and cooling process to form a Y-Ti-O composite oxide with higher thermal stability than Y2O3. Due to the small molten pool and fast solidification and cooling rate during the SLM forming process, the agglomeration and growth of nano-oxide particles are inhibited, which can ensure that the nano-particles in the bulk alloy are small in size and evenly distributed. At the same time, the printed bulk alloy is further annealed to promote the in-situ precipitation of more Y, Ti, and O elements from the matrix in the form of nano-oxide particles. The dispersion strengthening effect of the precipitated nano-oxide particles can improve the comprehensive mechanical properties of the high-entropy alloy, further ensuring that the nano-particles in the ODS high-entropy alloy have a high number density.

[0038] On the other hand, the present invention utilizes the advantages of SLM such as no need for molds and high forming efficiency to achieve direct rapid forming of ODS high entropy alloys, solving the problems of traditional powder metallurgy technology (such as MA) in preparing ODS alloys, such as long cycle, multiple processes, and difficulty in preparing complex components.

[0039] The Co-Cr-Fe-Ni ODS high entropy alloy of the present invention has the following beneficial effects compared with the prior art:

[0040] (1) The existing MA method for preparing ODS alloys requires high-energy ball milling of the raw material powder for dozens or even hundreds of hours to obtain a supersaturated solid solution, which is time-consuming, prone to pollution, and inefficient. The present invention only requires a short mixing of the raw material powder to obtain a mixed powder that is directly used in the SLM process, which has a short process time, is not prone to pollution, and is highly efficient.

[0041] (2) The present invention uses Co-Cr-Fe-Ni high entropy pre-alloyed powder, Fe-Y pre-alloyed powder, and nano-TiO2 powder as raw materials for mixing. The mixed powder is completely melted in the SLM process, so that the Y, Ti, and O elements can form Y-Ti-O particles through in-situ reaction during the solidification and cooling process of SLM. These particles are more stable than Y2O3 and are generally smaller in size.

[0042] (3) The present invention uses SLM additive manufacturing technology to gradually form the required metal components under the control of a computer program without the need for molds, achieving near-net shape, thus solving the problem that existing powder metallurgy technology is difficult to prepare complex ODS alloy components.

[0043] (4) The present invention uses SLM additive manufacturing technology. The molten pool formed by the laser heat source is small and the molten pool solidifies quickly, which can inhibit the agglomeration and growth of oxide particles and obtain an ODS high-entropy alloy block with uniformly distributed nano-oxide particles.

[0044] (5) The present invention further performs annealing treatment on the bulk alloy obtained by printing to promote the in-situ precipitation of more nano-oxide particles from the matrix, so that the nano-particles in the ODS high entropy alloy have a higher number density. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0046] Figure 1 Flow chart of the preparation method of Co-Cr-Fe-Ni based ODS high entropy alloy provided in an embodiment of the present invention;

[0047] Figure 2 This is a scanning electron microscope photograph of the Co-Cr-Fe-Ni based ODS high entropy alloy after being corroded by aqua regia in Example 1 of the present invention;

[0048] Figure 3 This is a HAADF-STEM photograph of the Co-Cr-Fe-Ni based ODS high entropy alloy in Example 1 of the present invention under a transmission electron microscope;

[0049] Figure 4 This is a scanning electron microscope photograph of the alloy in Comparative Example 1 of the present invention after being corroded by aqua regia. DETAILED DESCRIPTION

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The SLM forming technology disclosed in the present invention has great advantages in preparing processed material parts because of its advantages such as fast processing efficiency, few and convenient post-processing steps, and the formed materials usually having a fine organizational structure. It is expected to become a new process for preparing ODS high entropy alloys. Therefore, the present invention adopts the solution of preparing ODS high entropy alloys using SLM forming technology, hoping to provide an experimental basis and application basis for preparing ODS high entropy alloys using SLM forming technology.

[0051] Specifically, using Figure 1 The preparation steps shown are for preparing Co-Cr-Fe-Ni based ODS high entropy alloy, including:

[0052] S1. Preparation of Co-Cr-Fe-Ni ODS high entropy alloy raw material powder

[0053] S1.1. Ingredient design and ingredients

[0054] Co-Cr-Fe-Ni high entropy pre-alloyed powder, Fe-Y pre-alloyed powder and nano-TiO2 powder are uniformly mixed as raw materials in a certain proportion. Preferably, the ratio of Co-Cr-Fe-Ni high entropy pre-alloyed powder is 97.8wt.%, the ratio of Fe-Y powder is 1.0wt.%, and the ratio of TiO2 powder is 1.2wt.%.

[0055] Preferably, the elements in the Co-Cr-Fe-Ni high entropy pre-alloyed powder are in equiatomic ratios, and the content of Y element in the Fe-Y powder is 6.0 wt.%.

[0056] S1.2 Powder mixing

[0057] The required raw material powders were weighed using an electronic balance according to the above ratios. The mixed powders were then poured into a stainless steel ball mill. After the mill was sealed, it was evacuated using a vacuum pump and then filled with 0.1 MPa argon as a protective gas. No grinding balls or process control agents were added. A planetary ball mill was run at 200 rpm for 6 hours to ensure uniform mixing of the various powders within the mixed powder, resulting in a mixed powder suitable for the SLM process.

[0058] S2. Preparation of Co-Cr-Fe-Ni ODS high entropy alloy blocks by SLM forming

[0059] S2.1. Pre-forming treatment

[0060] Before printing begins, the raw material powder is placed in a vacuum drying oven and kept at 120°C for 20 hours. The raw material powder is then poured into the powder feed hopper of the printer and evenly distributed. The stainless steel substrate is then preheated to 120°C in the printer. The printer is then evacuated and filled with high-purity argon as a protective gas. Printing officially begins only after the oxygen content in the printer drops below 0.01%.

[0061] S2.2, SLM forming

[0062] The ODS high entropy alloy block material was prepared using SLM forming technology. After printing, it was separated from the substrate using wire cutting equipment.

[0063] The SLM printing process parameters are preferably: a powder layer thickness of 40 μm; a laser power of 200-300 W; a scanning pitch of 70-80 μm; and a scanning speed of 600-1200 mm / s. To reduce thermal stress in the component, the scanning strategy uses a 67° rotation layer by layer (i.e., the scanning angle of each successive layer needs to be rotated 67° in the same direction).

[0064] S3. Performing annealing heat treatment on the bulk material.

[0065] The ODS high entropy alloy bulk materials prepared by SLM were annealed under argon protection using a tube furnace.

[0066] Preferably, the annealing temperature is 900° C., the holding time is 1 h, and the heating rate is set to 10° C. / min.

[0067] The above technical solution is described in detail below in conjunction with specific embodiments.

[0068] Example 1

[0069] This embodiment provides a SLM preparation method of a Co-Cr-Fe-Ni based ODS high entropy alloy, which is as follows:

[0070] (1) Using Co-Cr-Fe-Ni high entropy pre-alloyed powder with equal atomic ratios of each element, Fe-Y pre-alloyed powder containing 6.0wt.% Y element, and TiO2 powder as raw materials, the required powders were weighed according to the ratio of 97.8wt.% Co-Cr-Fe-Ni, 1.0wt.% Fe-Y, and 1.2wt.% TiO2. The weighed powders were mixed and poured into a 500ml stainless steel ball mill (400g of mixed powder per jar). After the ball mill was sealed, it was vacuumed using a vacuum pump and then filled with 0.1MPa argon as a protective gas without adding any grinding balls or process control agents. A planetary ball mill was then used to operate at a speed of 200rpm for 6h to ensure that the various powders in the mixed powder were evenly mixed, thereby obtaining the raw material mixed powder for the SLM process. The raw material mixed powder was placed in a vacuum drying oven and kept warm at 120℃ for 20h. The raw material mixed powder was then taken out and poured into the powder feeding bin of the printing device and flattened. A 100 mm × 100 mm stainless steel substrate was installed in the printing equipment and preheated to 120°C.

[0071] (2) The basic SLM process parameters were set as follows: powder layer thickness of 40 μm, laser power of 200 W, scanning pitch of 70 μm, and scanning speed of 800 mm / s. The printing equipment was evacuated and filled with high-purity argon as a protective gas. Printing began when the oxygen content in the equipment dropped below 0.01%. After printing, a 5 mm × 8 mm × 10 mm rectangular sample was obtained, and the printed sample was separated from the substrate using wire cutting.

[0072] (3) Annealing treatment was performed on each ODS high entropy alloy bulk material prepared by SLM in a tube furnace under argon protection. The annealing temperature was 900°C, the holding time was 1 h, and the heating rate was set at 10°C / min.

[0073] Determination by density balance and Vickers hardness tester shows that the Co-Cr-Fe-Ni based ODS high entropy alloy block has good forming performance, a density of 98.4% and a hardness of 270.5HV. Figure 2 This is a scanning electron microscope (SEM) photograph of the alloy after aqua regia corrosion. The molten pool boundary and the substructure within the grains can be clearly seen, and no other impurity phases exist in the sample. Figure 3 This is the HAADF-STEM photo of the alloy under a transmission electron microscope. It can be observed that a large number of nanoparticles (black particles in the figure) are dispersed in the matrix, with an average size of about 7nm and a number density of about 7.6×10 22 m -3 After calibration, these nanoparticles were identified as Y2Ti2O7.

[0074] Example 2

[0075] This embodiment provides a SLM preparation method of a Co-Cr-Fe-Ni based ODS high entropy alloy, which is as follows:

[0076] (1) Using Co-Cr-Fe-Ni high entropy pre-alloyed powder with equal atomic ratios of each element, Fe-Y pre-alloyed powder containing 6.0wt.% Y element, and TiO2 powder as raw materials, the required powders were weighed according to the ratio of 97.8wt.% Co-Cr-Fe-Ni, 1.0wt.% Fe-Y, and 1.2wt.% TiO2. The weighed powders were mixed and poured into a 500ml stainless steel ball mill (400g of mixed powder per jar). After the ball mill was sealed, it was vacuumed using a vacuum pump and then filled with 0.15MPa argon as a protective gas. No grinding balls or process control agents were added. A planetary ball mill was then used to operate at a speed of 250rpm for 4h to ensure that the various powders in the mixed powder were evenly mixed, thereby obtaining the raw material mixed powder for the SLM process. The raw material powder mixture was placed in a vacuum drying oven and kept at 130°C for 30 hours. The raw material powder mixture was then poured into the powder feed hopper of the printing device and evenly spread. A 100mm x 100mm stainless steel substrate was placed in the printing device and preheated to 120°C.

[0077] (2) The basic SLM process parameters were set as follows: powder layer thickness of 40 μm, laser power of 200 W, scanning pitch of 80 μm, and scanning speed of 600 mm / s. The printing equipment was evacuated and filled with high-purity argon as a protective gas. Printing began when the oxygen content in the equipment dropped below 0.01%. After printing, a 5 mm × 8 mm × 10 mm rectangular sample was obtained, and the printed sample was separated from the substrate using wire cutting.

[0078] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0079] The Co-Cr-Fe-Ni-based ODS high entropy alloy has good bulk formability, a density of 98.7%, and a hardness of 261.7 HV. The microstructure of the alloy is similar to that of Example 1, with a large number of Y2Ti2O7 nanoparticles dispersed in the matrix.

[0080] Example 3

[0081] This embodiment provides a SLM preparation method of a Co-Cr-Fe-Ni based ODS high entropy alloy, which is as follows:

[0082] (1) Using Co-Cr-Fe-Ni high entropy pre-alloyed powder with equal atomic ratios of each element, Fe-Y pre-alloyed powder containing 6.0wt.% Y element, and TiO2 powder as raw materials, the required powders were weighed according to the ratio of 97.8wt.% Co-Cr-Fe-Ni, 1.0wt.% Fe-Y, and 1.2wt.% TiO2. The weighed powders were mixed and poured into a 500ml stainless steel ball mill (400g of mixed powder per jar). After the ball mill was sealed, it was vacuumed using a vacuum pump and then filled with 0.12MPa argon as a protective gas. No grinding balls or process control agents were added. A planetary ball mill was then used to operate at a speed of 220rpm for 5h to ensure that the various powders in the mixed powder were evenly mixed, thereby obtaining the raw material mixed powder for the SLM process. The raw material powder mixture was placed in a vacuum drying oven and kept at 125°C for 25 hours. The raw material powder mixture was then poured into the powder feed hopper of the printing device and evenly spread. A 100mm x 100mm stainless steel substrate was placed in the printing device and preheated to 120°C.

[0083] (2) The basic SLM process parameters were set as follows: powder layer thickness of 40 μm, laser power of 200 W, scanning pitch of 80 μm, and scanning speed of 1200 mm / s. The printing equipment was evacuated and filled with high-purity argon as a protective gas. Printing began when the oxygen content in the equipment dropped below 0.01%. After printing, a 5 mm × 8 mm × 10 mm rectangular sample was obtained, and the printed sample was separated from the substrate using wire cutting.

[0084] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0085] The Co-Cr-Fe-Ni-based ODS high entropy alloy has good bulk formability, a density of 98.7%, and a hardness of 265.1 HV. The microstructure of the alloy is similar to that of Example 1, with a large number of Y2Ti2O7 nanoparticles dispersed in the matrix.

[0086] Example 4

[0087] This embodiment provides a SLM preparation method of a Co-Cr-Fe-Ni based ODS high entropy alloy, which is as follows:

[0088] (1) Prepare the raw material mixed powder and perform pre-printing preparation in the same manner as step (1) of Example 1.

[0089] (2) The basic SLM process parameters were set as follows: powder layer thickness of 40 μm, laser power of 300 W, scanning pitch of 80 μm, and scanning speed of 800 mm / s. The printing equipment was evacuated and filled with high-purity argon as a protective gas. Printing began when the oxygen content in the equipment dropped below 0.01%. After printing, a 5 mm × 8 mm × 10 mm rectangular sample was obtained, and the printed sample was separated from the substrate using wire cutting.

[0090] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0091] The Co-Cr-Fe-Ni-based ODS high entropy alloy has good bulk formability, a density of 98.5%, and a hardness of 265.0 HV. The microstructure of the alloy is similar to that of Example 1, with a large number of Y2Ti2O7 nanoparticles dispersed in the matrix.

[0092] Example 5

[0093] (1) Using Co-Cr-Fe-Ni high-entropy pre-alloyed powder with equal atomic ratios of each element, Fe-Y pre-alloyed powder containing 6.0 wt.% Y element, and TiO2 powder as raw materials, the required powders are weighed according to a ratio of 95.6 wt.% Co-Cr-Fe-Ni, 2.0 wt.% Fe-Y, and 2.4 wt.% TiO2. The weighed powders are mixed and poured into a stainless steel ball mill with a volume of 500 ml (400 g of mixed powder per jar); the remaining preparation steps are consistent with (1) in Example 1.

[0094] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0095] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0096] The Co-Cr-Fe-Ni-based ODS high entropy alloy has good bulk formability, a density of 98.0%, and a hardness of 273.3 HV. The microstructure of the alloy is similar to that of Example 1, with a large number of Y2Ti2O7 nanoparticles dispersed in the matrix.

[0097] Example 6

[0098] (1) Using Co-Cr-Fe-Ni high-entropy pre-alloyed powder with equal atomic ratios of each element, Fe-Y pre-alloyed powder containing 6.0 wt.% Y element, and TiO2 powder as raw materials, the required powders are weighed according to a ratio of 98.5 wt.% Co-Cr-Fe-Ni, 0.7 wt.% Fe-Y, and 0.8 wt.% TiO2. The weighed powders are mixed and poured into a stainless steel ball mill with a volume of 500 ml (400 g of mixed powder per jar); the remaining preparation steps are consistent with (1) in Example 1.

[0099] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0100] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0101] The Co-Cr-Fe-Ni-based ODS high entropy alloy has good bulk formability, a density of 98.9%, and a hardness of 266.7 HV. The microstructure of the alloy is similar to that of Example 1, with a large number of Y2Ti2O7 nanoparticles dispersed in the matrix.

[0102] Example 7

[0103] (1) Prepare the raw material mixed powder and perform pre-printing preparation in the same manner as step (1) of Example 1.

[0104] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0105] (3) Annealing treatment was performed on each ODS high entropy alloy bulk material prepared by SLM in a tube furnace under argon protection. The annealing temperature was 800°C, the holding time was 2 h, and the heating rate was set at 10°C / min.

[0106] The Co-Cr-Fe-Ni-based ODS high entropy alloy has good bulk formability, a density of 98.1%, and a hardness of 266.2 HV. The microstructure of the alloy is similar to that of Example 1, with a large number of Y2Ti2O7 nanoparticles dispersed in the matrix.

[0107] Example 8

[0108] (1) Prepare the raw material mixed powder and perform pre-printing preparation in the same manner as step (1) of Example 1.

[0109] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0110] (3) Annealing of each ODS high entropy alloy bulk material prepared by SLM was performed in a tube furnace under argon protection. The annealing temperature was 950°C, the holding time was 1 h, and the heating rate was set at 15°C / min.

[0111] The Co-Cr-Fe-Ni-based ODS high entropy alloy has good bulk formability, a density of 98.7%, and a hardness of 274.4 HV. The microstructure of the alloy is similar to that of Example 1, with a large number of Y2Ti2O7 nanoparticles dispersed in the matrix.

[0112] Comparative Example 1

[0113] The specific implementation steps of this comparative example are as follows:

[0114] (1) Using Co-Cr-Fe-Ni high entropy pre-alloyed powder and Y2O3 powder with equal atomic ratios of each element as raw materials, the required powders were weighed according to the ratio of 99.5wt.% Co-Cr-Fe-Ni and 0.5wt.% Y2O3. The weighed powders were mixed and poured into a 500ml stainless steel ball mill (400g of mixed powder per jar). After the ball mill was sealed, it was vacuumed using a vacuum pump and then filled with 0.1MPa argon as a protective gas without adding any grinding balls or process control agents. A planetary ball mill was then used to operate at a speed of 200rpm for 6h to ensure that the various powders in the mixed powder were evenly mixed, thereby obtaining the raw material mixed powder for the SLM process. The raw material mixed powder was placed in a vacuum drying oven and kept warm at 120℃ for 20h. The raw material mixed powder was then taken out and poured into the powder feed bin of the printing device and flattened. A 100 mm × 100 mm stainless steel substrate was installed in the printing equipment and preheated to 120°C.

[0115] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0116] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0117] It has been determined that the high entropy alloy block has good forming performance. Figure 4 The scanning electron microscope (SEM) photograph of the alloy after aqua regia corrosion shows that Y2O3 agglomerates to the micron level, failing to achieve the dispersion strengthening effect. Since Y2O3 powder and Co-Cr-Fe-Ni high-entropy pre-alloyed powder are directly used as raw materials for printing, Y2O3 has a high melting point and cannot fully melt into the SLM melt pool, resulting in agglomeration during the SLM melting and solidification process. However, the present invention uses Co-Cr-Fe-Ni high-entropy pre-alloyed powder, Fe-Y pre-alloyed powder, and nano-TiO2 powder as raw materials. Each powder is fully melted, and a portion of the Y, Ti, and O elements directly react in situ during the solidification and cooling process to form a Y-Ti-O composite oxide with higher thermal stability than Y2O3. Subsequent annealing promotes further in-situ reaction, ultimately achieving a dispersed distribution of fine-sized nano-oxide particles.

[0118] Comparative Example 2

[0119] The specific implementation steps of this comparative example are as follows:

[0120] (1) Prepare the raw material mixed powder and perform pre-printing preparation in the same manner as step (1) of Example 1.

[0121] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0122] The results show that the high entropy alloy has good bulk forming performance, but the number density of oxide particles in the matrix is ​​only 4.8×10 20 m -3 , two orders of magnitude lower than that of Example 1. If the bulk alloy prepared by SLM printing is not annealed, more Y, Ti, and O elements cannot be in-situ precipitated from the matrix in the form of nano-oxide particles, resulting in a low number density of oxide particles in the matrix, which cannot meet the requirements.

[0123] Comparative Example 3

[0124] The specific implementation steps of this comparative example are as follows:

[0125] (1) Using Co-Cr-Fe-Ni high entropy pre-alloyed powder with equal atomic ratios of each element, Fe-Y pre-alloyed powder containing 6.0wt.% Y element, and TiO2 powder as raw materials, the required powders were weighed according to the ratio of 99.6wt.% Co-Cr-Fe-Ni, 0.2wt.% Fe-Y, and 0.2wt.% TiO2. The weighed powders were mixed and poured into a 500ml stainless steel ball mill (400g of mixed powder per can). After the ball mill was sealed, it was vacuumed using a vacuum pump and then filled with 0.1MPa argon as a protective gas without adding any grinding balls or process control agents. A planetary ball mill was then used to operate at a speed of 200rpm for 6h to ensure that the various powders in the mixed powder were evenly mixed, thereby obtaining the raw material mixed powder for the SLM process. The raw material mixed powder was placed in a vacuum drying oven and kept warm at 120℃ for 20h. The raw material mixed powder was then taken out and poured into the powder feeding bin of the printing device and flattened. A 100 mm × 100 mm stainless steel substrate was installed in the printing equipment and preheated to 120°C.

[0126] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0127] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0128] Measurements show that the high-entropy alloy has excellent bulk formability, but nanoscale oxide particles are virtually undetectable in the matrix. Because the amounts of Fe-Y and TiO2 powders used are smaller than those used in the present invention, the Y-Ti-O composite oxide formed by the direct in-situ reaction of Y, Ti, and O during solidification and cooling is minimal and virtually undetectable.

[0129] Comparative Example 4

[0130] The specific implementation steps of this comparative example are as follows:

[0131] (1) Using Co-Cr-Fe-Ni high entropy pre-alloyed powder with equal atomic ratios of each element, Fe-Y pre-alloyed powder containing 6.0wt.% Y element, and TiO2 powder as raw materials, the required powders are weighed according to the ratio of 99.6wt.% Co-Cr-Fe-Ni, 5.0wt.% Fe-Y, and 5.0wt.% TiO2. The weighed powders are mixed and poured into a 500ml stainless steel ball mill (400g of mixed powder per can). After the ball mill is sealed, it is vacuumed using a vacuum pump and then filled with 0.1MPa argon as a protective gas without adding any grinding balls or process control agents. A planetary ball mill is then used to operate at a speed of 200rpm for 6h to ensure that the various powders in the mixed powder are evenly mixed, thereby obtaining the raw material mixed powder for the SLM process. The raw material mixed powder is placed in a vacuum drying oven and kept warm at 120℃ for 20h. The raw material mixed powder is then taken out and poured into the powder feed bin of the printing device and flattened. A 100 mm × 100 mm stainless steel substrate was installed in the printing equipment and preheated to 120°C.

[0132] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0133] (3) The printed alloy is subjected to annealing heat treatment in the same manner as step (3) of Example 1.

[0134] Measurements have shown that the high-entropy alloy block has good forming performance, but the oxide particles in the matrix are significantly agglomerated, reaching a size of microns, and have no dispersion strengthening effect. Since the amount of Fe-Y powder and TiO2 powder used is greater than the range of Fe-Y powder and TiO2 powder in the present invention, the amount of Y-Ti-O composite oxide formed by direct in-situ reaction of Y, Ti, and O elements during the solidification and cooling process is excessive, making it easy for the nanoparticles to contact each other and agglomerate.

[0135] Comparative Example 5

[0136] The specific implementation steps of this comparative example are as follows:

[0137] (1) Prepare the raw material mixed powder and perform pre-printing preparation in the same manner as step (1) of Example 1.

[0138] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0139] (3) Annealing treatment was performed on each ODS high entropy alloy bulk material prepared by SLM in a tube furnace under argon protection. The annealing temperature was 700°C, the holding time was 1 h, and the heating rate was set at 10°C / min.

[0140] The number density of oxide particles in the high entropy alloy block was determined to be only 8.9×10 20 m -3 , which is two orders of magnitude lower than that of Example 1. This is because the annealing temperature is lower than the range of the present invention and cannot provide enough energy to fully precipitate the nanoparticles in situ.

[0141] Comparative Example 6

[0142] The specific implementation steps of this comparative example are as follows:

[0143] (1) Prepare the raw material mixed powder and perform pre-printing preparation in the same manner as step (1) of Example 1.

[0144] (2) The same SLM process as in step (2) of Example 1 was performed to prepare the bulk alloy.

[0145] (3) Annealing treatment was performed on each ODS high entropy alloy bulk material prepared by SLM in a tube furnace under argon protection. The annealing temperature was 1000°C, the holding time was 1 h, and the heating rate was set at 10°C / min.

[0146] The average size of the oxide particles in the high entropy alloy bulk was measured to be over 80 nm, which was significantly larger than that in Example 1. This was because the annealing temperature was higher than the range of the present invention, causing the oxide particles to grow rapidly.

[0147] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A Co-Cr-Fe-Ni based ODS high entropy alloy, characterized in that: The Co-Cr-Fe-Ni ODS high entropy alloy is obtained by SLM forming a mixed raw material powder consisting of Co-Cr-Fe-Ni high entropy pre-alloyed powder, Fe-Y powder and TiO2 powder, followed by annealing; the annealing temperature is 800-950°C, and the annealing time is 1-2 hours; The elements Co, Cr, Fe and Ni in the Co-Cr-Fe-Ni high entropy pre-alloyed powder are in equiatomic ratios; Among the raw materials, the ratio of Fe-Y powder is 0.7~2.0 wt.%, the ratio of TiO2 powder is 0.8~2.4 wt.%, and the ratio of Co-Cr-Fe-Ni high entropy pre-alloyed powder is 95.6~98.5 wt.%.

2. The Co-Cr-Fe-Ni based ODS high entropy alloy according to claim 1, wherein: The content of Y element in the Fe-Y powder is 6.0 wt.%.

3. The method for preparing a Co-Cr-Fe-Ni based ODS high entropy alloy according to claim 1 or 2, wherein: The following steps are involved: Step S1: Co-Cr-Fe-Ni high entropy pre-alloyed powder, Fe-Y powder and TiO2 powder are used as raw materials and mixed to obtain a mixed powder; Step S2: The mixed powder is formed by SLM printing and annealing to obtain the Co-Cr-Fe-Ni based ODS high entropy alloy.

4. The preparation method according to claim 3, wherein In step S2, the annealing gas is an inert gas, and the inert gas is selected from at least one of argon, helium, and neon; The heating rate of the annealing is 10-15°C / min.

5. The preparation method according to claim 3, wherein In step S2, the mixed powder is dried before SLM printing; The drying temperature is 120-130° C., and the drying time is 20-30 hours.

6. The preparation method according to claim 3, wherein In step S2, the process parameters of the SLM printing are set as follows: the powder layer thickness is a fixed value of 40 μm, the scanning mode is a layer-by-layer rotation of 67°, the laser power is 200-300 W, the scanning spacing is 70-80 μm, and the scanning speed is 600-1200 mm / s.

7. The preparation method according to claim 3, wherein In step S2, the substrate formed by SLM printing is a stainless steel substrate, and the size of the substrate is 100 mm×100 mm; The substrate is preheated to 120°C before printing, then vacuumed and filled with argon for protection, and formal printing begins after the oxygen content drops below 0.01%.

8. The preparation method according to claim 3, wherein In step S1, a planetary ball mill is used for mixing, and no grinding balls or process control agents are added to the ball mill; The rotation speed of the planetary ball mill is 200 rpm to 250 rpm, and the operation time is 4 to 6 hours.

9. The preparation method according to claim 3, wherein In the step S1, the protective gas during the mixing is argon, and the amount of the argon is 0.1 MPa to 0.15 MPa.

10. Application of the Co-Cr-Fe-Ni based ODS high entropy alloy according to claim 1 or 2 or the Co-Cr-Fe-Ni based ODS high entropy alloy prepared by the preparation method according to any one of claims 3 to 9 in the fields of metal matrix composites, aerospace, new energy, and biomedicine.

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