Twin structure reinforced CoCrFeNi high-entropy alloy and preparation method thereof

Abstract

The application provides a twin structure reinforced CoCrFeNi high-entropy alloy and a preparation method thereof, and the preparation method comprises the following steps: CoCrFeNi high-entropy alloy gas atomization powder is formed by laser melting deposition additive manufacturing, and ultrasonic impact treatment is performed layer by layer in the forming process, so that a single-phase FCC high-entropy alloy containing a twin structure reinforcement with good strength and plasticity matching is obtained. The preparation method of laser melting deposition additive manufacturing plus ultrasonic impact is adopted, the generation of the twin structure in the CoCrFeNi high-entropy alloy is realized, and the high-entropy alloy has higher yield strength and tensile strength. The preparation method is simple and convenient to operate, and one-time forming can effectively solve the defects of insufficient strength of the existing additive manufacturing high-entropy alloy, and an effective regulation method for the microstructure and performance of the laser melting deposition additive manufacturing high-entropy alloy is obtained.

Description

Technical Field

[0001] This invention belongs to the field of microstructure and property control in laser melting deposition additive manufacturing, specifically relating to a twin-structure reinforced CoCrFeNi high-entropy alloy and its preparation method. Background Technology

[0002] High-entropy alloys, as a novel type of alloy, possess high mixing entropy, which suppresses the formation of intermetallic compounds. They typically tend to form solid solution phases with FCC, BCC, and HCP crystal structures. Consequently, high-entropy alloys generally exhibit characteristics such as high strength, high hardness, good thermal stability, and excellent wear and corrosion resistance. Currently, research on CoCrFeNi high-entropy alloys mainly focuses on the study of the FCC single phase. The limitation of this structure is that while it has high plasticity, its strength is relatively low, which cannot meet the requirements for application.

[0003] Laser melting deposition additive manufacturing (LDM) can directly fabricate solid parts based on three-dimensional data, thereby improving part utilization and showing great potential in the preparation of CoCrFeNi high-entropy alloys. However, the LDM additive manufacturing process for metals involves complex physical metallurgical processes. The melting, solidification, and cooling of the material during forming are all completed under extremely rapid conditions. Its solidification process is characterized by high temperature gradients, high cooling rates, and complex thermal cycling-induced local remelting of the deposited material. Currently, the microstructure of high-entropy alloys manufactured by additive manufacturing is usually coarse columnar crystals, leading to anisotropy of mechanical properties and a mismatch between strength and plasticity in the deposited layer. Summary of the Invention

[0004] This invention provides a twinned structure reinforced CoCrFeNi high-entropy alloy and its preparation method. The method uses laser melting deposition additive manufacturing combined with ultrasonic impact treatment to improve the microstructure and properties of the CoCrFeNi high-entropy alloy. Through plastic deformation, recovery recrystallization and twinning behavior, a CoCrFeNi high-entropy alloy with good strength and plasticity matching is obtained.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a twinned CoCrFeNi high-entropy alloy includes the following steps:

[0007] Step 1, substrate cleaning;

[0008] Step 2: After the CoCrFeNi high-entropy alloy powder is formed by laser melting deposition in one pass, the laser melting deposition layer is treated by ultrasonic impact.

[0009] Step 3: Repeat step 2. After each layer of CoCrFeNi high-entropy alloy powder is formed by laser melting deposition, ultrasonic impact is used to treat the laser melting deposition layer.

[0010] The above-mentioned method for preparing a twinned structure reinforced CoCrFeNi high-entropy alloy involves an ultrasonic impact power of 50W-1200W and an ultrasonic amplitude of 10-25μm.

[0011] The above-mentioned method for preparing a twinned structure reinforced CoCrFeNi high-entropy alloy, wherein the CoCrFeNi high-entropy alloy powder has a particle size of 45-105 μm.

[0012] In the above-mentioned method for preparing a twinned structure reinforced CoCrFeNi high-entropy alloy, the laser power during the laser melting deposition process is 500-2500W, the scanning speed is 200mm / min-1000mm / min, and the powder feeding rate is 10g / min-30g / min.

[0013] A twinned structure reinforced CoCrFeNi high-entropy alloy is prepared by the above-mentioned preparation method of a twinned structure reinforced CoCrFeNi high-entropy alloy. The twinned structure reinforced CoCrFeNi high-entropy alloy has a single-phase FCC structure with fine equiaxed grains and a grain size of 5μm-200μm.

[0014] The aforementioned twin-structure reinforced CoCrFeNi high-entropy alloy contains uniformly distributed twin structures, the width of which is 5μm-20μm and the length of which is 20μm-100μm.

[0015] The above-mentioned twinned structure reinforced CoCrFeNi high-entropy alloy has a volume fraction of 5%-40% in the CoCrFeNi high-entropy alloy.

[0016] Some beneficial effects of the present invention:

[0017] This invention prepares CoCrFeNi high-entropy alloys by laser melting deposition additive manufacturing combined with ultrasonic impact technology. This preparation method avoids the limitations of traditional processes such as complexity and high cost. It is formed in one step and does not require subsequent processing to meet the material performance requirements. It can be used as a common method for preparing CoCrFeNi high-entropy alloys.

[0018] This invention employs a combination of laser melting deposition additive manufacturing and ultrasonic impaction to achieve free manufacturing of parts. It enables layer-by-layer plastic deformation and recrystallization of the as-cast structure, eliminates residual stress in the additive structure, and ultimately improves the mechanical properties of the material through the introduction of deformation twins. By changing different ultrasonic impaction process parameters, the plastic deformation, recovery recrystallization, and twinning behavior of high-entropy alloys manufactured by laser melting deposition additive manufacturing are controlled. Finally, a CoCrFeNi high-entropy alloy with excellent comprehensive mechanical properties, yield strength ≥500MPa, tensile strength ≥670MPa, and elongation ≥30%, is obtained. Attached Figure Description

[0019] Figure 1 The CoCrFeNi high-entropy alloy microstructure prepared in the embodiments of the present invention is shown in (a) as the laser melting deposition state and (b) as the laser melting deposition state plus ultrasonic shock treatment state.

[0020] Figure 2 The XRD patterns of the CoCrFeNi high-entropy alloy prepared in the embodiments of the present invention and the CoCrFeNi high-entropy alloy prepared by laser melting deposition alone are shown below.

[0021] Figure 3 This is a comparison of the tensile properties of the CoCrFeNi high-entropy alloy prepared in the embodiments of the present invention and the CoCrFeNi high-entropy alloy prepared only by laser melting deposition. Detailed Implementation

[0022] The following example demonstrates the preparation of CoCrFeNi high-entropy alloys using laser melting deposition additive manufacturing combined with ultrasonic impaction technology. This will provide a thorough understanding and description of the invention. However, it should be noted that the brazing method of this invention is applicable to different types of high-entropy alloys. Therefore, the following examples are merely illustrative and not intended to limit the scope of the invention in any way. Furthermore, the terminology used in this invention, unless otherwise specified, generally has the meanings commonly understood by those skilled in the art.

[0023] Example

[0024] The first step is preparation for laser melting deposition forming of high-entropy alloys. Before laser melting deposition forming of high-entropy alloys, the substrate surface is cleaned with industrial anhydrous ethanol to remove oil and contaminants, preventing them from affecting the forming of the high-entropy alloy.

[0025] The second step involves preparing high-entropy alloy components through laser melting deposition forming followed by ultrasonic impact treatment. After one pass of laser melting deposition forming of the CoCrFeNi high-entropy alloy, it is subjected to ultrasonic impact treatment, followed by a second pass of laser melting deposition forming, and then another ultrasonic impact treatment. This process of sequential laser melting deposition and ultrasonic impact treatment allows for the step-by-step control of the microstructure and properties of the CoCrFeNi high-entropy alloy manufactured by laser melting deposition additive manufacturing. The experimental substrate is Q235 steel, and the high-entropy alloy powder is prepared by gas atomization, with a particle size of 45-105 μm and atomic percentages of: Co: 23%-27%, Cr: 22%-27%, Fe: 22%-27%, Ni: 22%-27%. High-entropy alloy components were formed using the same experimental parameters. Specifically, the laser power was controlled within the range of 500W-2500W (1500W was selected in this embodiment), the scanning speed was within the range of 200mm / min-1000mm / min (300mm / min was selected in this embodiment), the powder feeding rate was within the range of 10g / min-30g / min (20g / min was selected in this embodiment), the ultrasonic power was within the range of 50W-1200W (200W was selected in this embodiment), and the ultrasonic amplitude was within the range of 10-25μm (18μm was selected in this embodiment). Simultaneously, the same laser melting deposition process parameters were used to form a CoCrFeNi high-entropy alloy.

[0026] Figure 1 The microstructures of CoCrFeNi high-entropy alloys prepared by laser melting deposition additive manufacturing combined with ultrasonic impaction are shown. (a) shows the laser melting deposition state, and (b) shows the state after laser melting deposition followed by ultrasonic impaction. It can be seen that the CoCrFeNi high-entropy alloy prepared by laser melting deposition has a coarse columnar crystal structure. The CoCrFeNi high-entropy alloy prepared by laser melting deposition followed by ultrasonic impaction has fine equiaxed grains with a grain size of 5μm-100μm. It contains twinned structures with a volume fraction of 20%, with widths of 5μm-20μm and lengths of 20μm-100μm.

[0027] Figure 2 The XRD pattern of the CoCrFeNi high-entropy alloy prepared by laser melting deposition additive manufacturing and ultrasonic impaction technology is shown. It can be seen that the CoCrFeNi high-entropy alloy prepared by laser melting deposition and ultrasonic impaction treatment has a single-phase FCC structure.

[0028] Figure 3The tensile properties of a CoCrFeNi high-entropy alloy prepared by laser melting deposition additive manufacturing combined with ultrasonic impaction were investigated. Experimental results show that the CoCrFeNi high-entropy alloy obtained without ultrasonic impaction treatment has a room temperature yield strength of 399.6 MPa, a tensile strength of 572.9 MPa, and an elongation of 34%. After passing through successive ultrasonic impactions, the CoCrFeNi high-entropy alloy exhibits a yield strength of 501 MPa, a tensile strength of 713 MPa, and an elongation of 35%, significantly improving its strength while maintaining good plasticity.

[0029] In summary, this invention discloses a twin-structure-reinforced CoCrFeNi high-entropy alloy and its preparation method. The preparation method includes the following steps: CoCrFeNi high-entropy alloy gas-atomized powder is shaped by laser melting deposition additive manufacturing, and ultrasonic impact treatment is performed in successive passes during the forming process to obtain a single-phase FCC high-entropy alloy with twin-structure reinforcement that exhibits good strength and plasticity matching. This invention employs a laser melting deposition additive manufacturing method combined with ultrasonic impact, avoiding the limitations of traditional high-entropy alloy preparation methods such as complex processes and high costs. It can effectively solve the defect of insufficient strength in existing additive-manufactured high-entropy alloys. Furthermore, it provides an effective method for controlling the microstructure and properties of high-entropy alloys manufactured by laser melting deposition additive manufacturing.

[0030] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its scope and spirit, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a twin structure reinforced CoCrFeNi high-entropy alloy, characterized in that, Includes the following steps: Step 1, substrate cleaning; Step 2: After the CoCrFeNi high-entropy alloy powder is formed by laser melting deposition in one pass, the laser melting deposition layer is treated by ultrasonic impact. Step 3: Repeat step 2. After each layer of CoCrFeNi high-entropy alloy powder is formed by laser melting deposition, the laser melting deposition layer is treated with ultrasonic impact. The ultrasonic impact power is 50W-1200W, and the ultrasonic amplitude is 10-25μm. The volume fraction of twinned structures in CoCrFeNi high-entropy alloys is 5%-40%.

2. The method for preparing a twin structure reinforced CoCrFeNi high-entropy alloy according to claim 1, characterized in that, The CoCrFeNi high-entropy alloy powder has a particle size of 45-105 μm.

3. The method of claim 1, wherein the CoCrFeNi high-entropy alloy is prepared by a twin structure strengthening method, characterized in that, During the laser melting deposition process, the laser power is 500-2500W, the scanning speed is 200 mm / min - 1000 mm / min, and the powder feeding rate is 10g / min - 30g / min.

4. A twin structure enhanced CoCrFeNi high-entropy alloy, characterized in that, The high-entropy alloy of CoCrFeNi reinforced by twin structure is prepared by any one of claims 1-3. The high-entropy alloy of CoCrFeNi reinforced by twin structure is a single-phase FCC structure with fine equiaxed grains and a grain size of 5μm-200μm.

5. The twinned structure reinforced CoCrFeNi high-entropy alloy according to claim 4, characterized in that, The twin-structure-reinforced CoCrFeNi high-entropy alloy contains uniformly distributed twin structures with a width of 5 μm-20 μm and a length of 20 μm-100 μm.

6. The twinned structure reinforced CoCrFeNi high-entropy alloy according to claim 4, characterized in that, The volume fraction of the twin structure in the CoCrFeNi high-entropy alloy is 5%-40%.

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