A heat treatment method for regulating the nano-network δ phase in CoCuFeNiTa high-entropy alloys

Abstract

Based on the demand for improving the density and toughness of CoCuFeNi alloy, the present invention adds 7% to 30% Ta element by mass, and based on the DSC curve, combined with the heat treatment process of 920℃ to 1050℃ high temperature furnace annealing, successfully regulates the nano-network δ phase in the CoCuFeNi alloy to improve the density and toughness of the CoCuFeNi alloy, wherein the Ta element is additionally regulated to enhance the density of the above alloy, thereby increasing the density by 10% to 21%; annealing treatment is performed to generate the nano-network δ phase to enhance the yield strength by 10% to 30%, and to improve the plasticity by 15% to 32%. Provided is a preparation and heat treatment method for a high-density, high-strength, high-plasticity alloy.

Description

Technical Field

[0001] The invention relates to the field of material technology, and in particular to a heat treatment method for regulating and controlling a nano-network delta phase in a CoCuFeNiTa high entropy alloy. Background Art

[0002] In recent years, the research on high-density alloys has continued to receive widespread attention. At present, most high-density alloys are copper-based alloys, and their application accounts for about 30% of the total application of high-density alloys. Although high-density alloys made of pure tantalum and pure tungsten have higher density than copper alloys, their high cost limits large-scale production and application. In addition, high-density alloys such as Ta and W usually have problems such as poor plasticity and difficulty in processing, which further limits their application in practical engineering. The development of new high-density alloys to reduce costs and improve the poor plasticity of high-density alloys such as Ta and W has important economic benefits and practical significance.

[0003] FCC alloys have many slip systems, so they show excellent plasticity, high forming efficiency and uniform formability, making them ideal for preparation and forming. However, the density of existing FCC alloys, such as CoCuFeNi, does not meet the requirements of high-density alloys (density greater than 8.94g / cm 3 ), and its yield strength and hardness are lower than the requirements of industrial production. Therefore, it is necessary to further design and optimize the composition of the alloy, by adding high-density metal elements such as Ta and W to the traditional FCC alloy; at the same time, optimize the heat treatment and processing technology, reduce internal defects such as holes and cracks, so as to improve the forming efficiency and comprehensive performance of high-density alloys.

[0004] The addition of Ta element to CoCuFeNiTa alloy leads to an increase in the second phase such as Laves phase, thereby increasing the Young's modulus and hardness of the matrix and enhancing its yield strength and other properties. Therefore, alloys containing Ta element become an ideal choice for preparing high-density alloys with excellent strength. However, the increase of Laves phase will also cause the plasticity of the alloy to decrease. In addition, the electronegativity of Cu element in CoCuFeNiTa alloy is quite different from that of other elements, resulting in significant element segregation. By rationally regulating the content of Ta element and selecting the optimal heat treatment parameters to optimize the heat treatment process, a new type of nano-network structure δ phase is generated, its plasticity is improved, and the alloy is given high strength, high modulus and excellent ductility. Therefore, the development of this improved method has great practical value and important scientific significance. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In recent years, the research on high-density alloys has received extensive attention, but the existing high-density alloys such as pure tantalum and pure tungsten are expensive, have poor plasticity, and are difficult to process, which limits their large-scale production and application. Although copper-based high-density alloys have low costs, their density and mechanical properties cannot meet the needs of high-end manufacturing. To this end, it is urgent to develop new high-density alloys to reduce costs and improve plasticity to meet the strategic needs of key fields such as aerospace and national defense science and technology. FCC-structured alloys have more slip systems and show excellent plasticity and forming properties, but their density and strength do not meet the requirements of high-density alloys. By adding high-density metal elements such as Ta and W to traditional FCC alloys, the density and mechanical properties of the alloy can be improved. However, the addition of Ta elements will lead to an increase in Laves phases, which will increase the Young's modulus and hardness, but also lead to a decrease in plasticity. In addition, the electronegativity difference between Cu and other elements is large, which is prone to element segregation and internal defects. Therefore, it is necessary to reasonably control the Ta content, optimize the heat treatment and processing technology, reduce internal defects such as holes and cracks, generate a new type of nano-network structure δ phase, and improve the plasticity and comprehensive properties of the alloy. The development of this alloy with high density, high strength, high modulus and excellent ductility has important economic benefits and practical significance.

[0007] 2. Technical solution

[0008] In order to achieve the above-mentioned purpose, the present invention is based on developing optimized annealing parameters to regulate the nano-network δ phase in CoCuFeNiTa alloy to improve its strength and toughness. Among them, the annealing treatment with optimal parameters regulates the nano-network δ phase so that the yield strength is as high as 1800MPa, providing a preparation and heat treatment method of a high-density, high-strength, and high-plasticity alloy.

[0009] The present invention provides a CoCuFeNiTa alloy, which comprises the following components in mass percentage: 20-25% of Co, 4-8% of Cu, 20-24% of Fe, 20-25% of Ni, 10-25% of Ni, and 7-23% of Ta; wherein the sum of the components of Co, Cu, Fe, Ni, and Ta is 100%.

[0010] The present invention provides a CoCuFeNiTa alloy, which comprises the following components in mass percentage: 20-28% of Co, 2%-15% of Cu, 17-26% of Fe, 10%-30% of Ni, 20%-27% of Fe, and 10%-30% of Ta; wherein the sum of the components of Co, Cu, Fe, Ni, and Ta is 100%.

[0011] Furthermore, it was measured that the proportion of the network nano-δ second phase was 12% to 52%, and the size was 120nm to 200nm.

[0012] Furthermore, the microhardness of the alloy is 360 HV to 620 HV.

[0013] Furthermore, the yield strength of the alloy is 1200MPa to 1800MPa.

[0014] Furthermore, the density of the alloy is 9 g / cm 3 ~10.2g / cm 3 .

[0015] The present invention also provides a method for optimizing the heat treatment parameters of CoCuFeNi alloy by using DSC, the method comprising the following steps:

[0016] Step 1: Use a differential scanning calorimeter to perform DSC experiments under argon protection at three different heating rates β, such as 2°C / min, 5°C / min, and 10°C / min. Heat the sample to a maximum temperature of 1400°C under argon protection, obtain the corresponding DSC curve, and record the peak temperature T of the exothermic peak at each heating rate. p .

[0017] Step 2: Using the Kissinger equation Analyze the experimental data. Fit the data to get the slope m, and use the activation energy formula Q = -m × R to calculate the activation energy Q;

[0018] Step 3: Substitute the activation energy Q into the rate constant formula in the JMAK equation: Combining experimental data with the JMAK equation: X(t) = 1-exp(-kt n ), calculate the transformation amount at different temperatures, and thus determine the optimal temperature with the fastest growth rate of δ phase and the smallest segregation;

[0019] Step 4: annealing in a muffle furnace for 4 hours;

[0020] Wherein, the annealing parameters include: annealing at 920° C. to 1050° C. in a muffle furnace for 4 hours.

[0021] Compared with the current prior art, the present invention has the following characteristics:

[0022] Based on the demand for improving the density and toughness of CoCuFeNi alloy, the present invention adds 7% to 30% Ta element by mass, and based on the DSC curve, combined with the heat treatment process of 920℃ to 1050℃ high temperature furnace annealing, successfully regulates the nano-network δ phase in the CoCuFeNi alloy to improve the density and toughness of the CoCuFeNi alloy, wherein the Ta element is additionally regulated to enhance the density of the above alloy, thereby increasing the density by 10% to 21%; annealing treatment is performed to generate the nano-network δ phase to enhance the yield strength by 10% to 30%, and to improve the plasticity by 15% to 32%. Provided is a preparation and heat treatment method for a high-density, high-strength, high-plasticity alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplifications do not constitute limitations on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute proportional limitations.

[0024] Figure 1 It is CoCu 0.5 FeNiTa 0.1 SEM images of

[0025] Figure 2 It is CoCu 0.4 FeNiTa 0.2 SEM images of

[0026] Figure 3 It is CoCu 0.3 FeNiTa 0.3 SEM images of

[0027] Figure 4 It is CoCu 0.2 FeNiTa 0.4 Scanning electron microscope image of . DETAILED DESCRIPTION

[0028] The inventors found that the alloy CoCuFeNi is the preferred material of the present invention. Compared with pure copper, the alloy CoCuFeNi contains a large amount of L12 phase, which can achieve Orowan pinning dislocation strengthening, thereby significantly improving the mechanical properties of the alloy. However, the density of the pure alloy CoCuFeNi is low and cannot meet the application requirements of high-density alloys. In order to increase the density of the alloy and have excellent plasticity, the inventors regulated the alloy by adding Ta elements. However, it is challenging to reasonably design the Ta content to maintain good forming ability. Therefore, it is particularly necessary to design a reasonable heat treatment process. The present invention proposes a Ta element regulation and annealing process, which can make a large number of network nano δ phases grow in the CoCuFeNiTa alloy to make up for the plasticity loss caused by hard and brittle phases such as laves. Taking the CoCuFeNiTa alloy that has been optimized for heat treatment as an example, its density is as high as 10.2g / cm 3 , with a yield strength of more than 1200Mpa. The heat-treated CoCuFeNiTa alloy not only has high density and high strength, but also has excellent plasticity and good thermal stability. Through the high-temperature annealing process with optimal parameters, the element segregation and internal defects in the alloy can be effectively reduced, and its comprehensive performance can be significantly improved. This innovative method has become the key to the development of new high-density, high-strength, and high-plasticity alloys, and has important practical value and scientific significance.

[0029] Hereinafter, the specific embodiments of the present application will be described in detail with reference to the accompanying drawings. According to these detailed descriptions, those skilled in the art can clearly understand the present application and can implement the present application. Without violating the principles of the present application, the features in the various embodiments can be combined to obtain new implementations, or certain features in certain embodiments can be replaced to obtain other preferred implementations.

[0030] The present invention provides a CoCuFeNiTa alloy, which comprises the following components in mass percentage: 20-25% of Co, 4-8% of Cu, 20-24% of Fe, 20-25% of Ni, 10-25% of Ni, and 7-23% of Ta; wherein the sum of the components of Co, Cu, Fe, Ni, and Ta is 100%.

[0031] It should be noted that Co, Cu, Ni, and Fe can also be replaced by other elements such as Cr. The above-mentioned elements are of the same type and can form FCC structures. Therefore, alloys with equivalent properties can be prepared using them as raw materials.

[0032] The present invention provides a CoCuFeNiTa alloy, which comprises the following components in mass percentage: 20-28% of Co, 2%-15% of Cu, 17-26% of Fe, 10%-30% of Ni, 20%-27% of Fe, and 10%-30% of Ta; wherein the sum of the components of Co, Cu, Fe, Ni, and Ta is 100%.

[0033] The present invention also provides a method for optimizing CoCuFeNi alloy by heat treatment, the method comprising the following steps:

[0034] Step 1: Use a differential scanning calorimeter to perform DSC experiments under argon protection at three different heating rates β, such as 2°C / min, 5°C / min, and 10°C / min. Heat the sample to a maximum temperature of 1400°C under argon protection, obtain the corresponding DSC curve, and record the peak temperature T of the exothermic peak at each heating rate. p .

[0035] Step 2: Using the Kissinger equation Analyze the experimental data. Fit the data to get the slope m, and use the activation energy formula Q = -m × R to calculate the activation energy Q.

[0036] Step 3: Substitute the activation energy Q into the rate constant formula in the JMAK equation: Combining experimental data with the JMAK equation: X(t) = 1-exp(-kt n ), calculate the transformation amount at different temperatures, and thus determine the optimal temperature with the fastest δ phase growth rate and minimum segregation.

[0037] Step 4: Use a muffle furnace to anneal for 4 hours.

[0038] The annealing parameters include: annealing in a muffle furnace at 920° C. to 1050° C. for 4 hours. The present invention is described in detail below in conjunction with specific implementation methods.

[0039] Example 1

[0040] Provided is a method for optimizing CoCuFeNi alloy by using Ta content and heat treatment, the method comprising the following steps:

[0041] According to the mass percentage of the alloy: Fe: 26.39%, Co: 26.39%, Cu: 14.23%, Ni: 26.28%, Ta: 8.1%, the sum of the five components is 100%, and a high entropy alloy is prepared. Using a differential scanning calorimeter, three different heating rates β are selected under argon protection, such as 2°

[0042] The DSC experiment was carried out at 3700℃ / min, 5℃ / min and 10℃ / min. The sample was heated to a maximum temperature of 1400℃ under argon protection, and the corresponding DSC curve was obtained. The optimal temperature was determined to be 920℃ through the JMAK equation.

[0043] The alloy was furnace annealed at 920℃ for 4h; after annealing, it was ground into a cylinder with a diameter of 6mm and a height of 9mm. The final scanning electron microscope photo of the alloy is as follows Figure 1 As shown, the yield strength is 1200MPa and the density is 9g / cm 3 The width of the nano-network δ phase is 110nm, accounting for 12%. The engineering strain is 50.2%, and the plasticity is improved by 32%.

[0044] Example 2

[0045] Provided is a method for optimizing CoCuFeNi alloy by using Ta content and heat treatment, the method comprising the following steps:

[0046] According to alloy CoCu 0.4 FeNiTa 0.2 The mass percentage of Fe: 23.76%, Co: 25.07%, Cu: 10.81%, Ni: 24.97% Ta: 15.39%, the sum of the five components is 100%, and a high entropy alloy is prepared. Using a differential scanning calorimeter, three different heating rates β are selected under argon protection, such as 2℃ / min, 5℃ / min, and 10℃ / min for DSC experiments. Under argon protection, the sample is heated to a maximum temperature of 1400℃, and the corresponding DSC curve is obtained. The optimal temperature is determined to be 1000℃ through the JMAK equation.

[0047] The alloy was furnace annealed at 1000℃ for 4h; after annealing, it was ground into a cylinder with a diameter of 6mm and a height of 9mm. The final scanning electron microscope photo of the alloy is as follows: Figure 2 As shown, the yield strength is 1350MPa and the density is 9.3g / cm 3 The width of the nano-network δ phase is 126nm, accounting for 25%, the engineering strain is 39%, and the plasticity is improved by 27%.

[0048] Example 3

[0049] Provided is a heat treatment method for regulating and controlling a nano-network delta phase in a CoCuFeNiTa high entropy alloy, the method comprising the following steps:

[0050] According to alloy CoCu 0.3 FeNiTa 0.3The mass percentage of Fe: 26.39%, Co: 23.88%, Cu: 7.72%, Ni: 23.78%, Ta: 21.99%, the sum of the five components is 100%, and a high entropy alloy is prepared. Using a differential scanning calorimeter, three different heating rates β are selected under argon protection, such as 2℃ / min, 5℃ / min, and 10℃ / min for DSC experiments. Under argon protection, the sample is heated to a maximum temperature of 1400℃, and the corresponding DSC curve is obtained. The optimal temperature is determined to be 980℃ through the JMAK equation.

[0051] The alloy was furnace annealed at 980℃ for 4h; after annealing, it was ground into a cylinder with a diameter of 6mm and a height of 9mm. The final scanning electron microscope photo of the alloy is as follows Figure 3 As shown, the yield strength is 1680MPa and the density is 9.6g / cm 3 The width of the nano-network δ phase is 86nm, accounting for 32%, the engineering strain is 36%, and the plasticity is improved by 18%.

[0052] Example 4

[0053] Provided is a heat treatment method for regulating and controlling a nano-network delta phase in a CoCuFeNiTa high entropy alloy, the method comprising the following steps:

[0054] According to alloy CoCu 0.2 FeNiTa 0.4 The mass percentage of Fe: 21.60%, Co: 22.79%, Cu: 4.92%, Ni: 22.70%, Ta: 27.99%, the sum of the five components is 100%, and a high entropy alloy is prepared. Using a differential scanning calorimeter, three different heating rates β are selected under argon protection, such as 2℃ / min, 5℃ / min, and 10℃ / min for DSC experiments. Under argon protection, the sample is heated to a maximum temperature of 1400℃, and the corresponding DSC curve is obtained. The optimal temperature is determined to be 1050℃ through the JMAK equation.

[0055] The alloy was furnace annealed at 1050℃ for 4h and then ground into a cylinder with a diameter of 6mm and a height of 9mm. The final scanning electron microscope photo of the alloy is as follows: Figure 1 As shown, the yield strength is 1800MPa and the density is 10.2g / cm 3 The width of the nano-network δ phase is 139nm, accounting for 46%, the engineering strain is 32%, and the plasticity is improved by 15%.

Claims

1. A CoCuFeNiTa alloy, characterized in that: The alloy comprises the following components in mass percentage: 20% to 28% Co, 2% to 15% Cu, 17% to 26% Fe, 10% to 30% Ni, and 10% to 30% Ta; wherein the sum of the components of Co, Cu, Fe, Ni, and Ta is 100%, the proportion of the mesh nano-delta second phase of the alloy is 12% to 52%, and the size is 86nm to 139nm.

2. The alloy according to claim 1, characterized in that The microhardness of the alloy is 460HV~620HV.

3. The alloy according to claim 1, characterized in that The density of the alloy is 9g / cm 3 ~10.2g / cm 3 .

4. The alloy according to claim 1, characterized in that The yield strength of the alloy is 1200MPa to 1800MPa.

5. The alloy according to claim 1, characterized in that The engineering strain of the alloy is 32% to 50%.

6. A heat treatment method for the alloy according to claim 1, characterized in that: The method comprises the following steps: Step 1: Use a differential scanning calorimeter to perform a DSC experiment under argon protection at three different heating rates, such as 2°C / min, 5°C / min, and 10°C / min. Heat the sample to a maximum temperature of 1400°C under argon protection, obtain the corresponding DSC curve, and record the peak temperature of the exothermic peak at each heating rate. Step 2: Using the Kissinger equation Analyze the experimental data, fit the data to get the slope m, and use the activation energy formula Q = -m × R to calculate the activation energy Q; Step 3. Substitute the activation energy Q into the rate constant formula in the JMAK equation: Combining experimental data with the JMAK equation: X(t) = 1-exp(-kt n ), calculate the transformation amount at different temperatures, and thus determine the optimal temperature with the fastest growth rate of δ phase and the smallest segregation; Step 4: annealing in a muffle furnace for 4 hours; Wherein, the annealing parameters include: annealing at 920° C. to 1050° C. in a muffle furnace for 4 hours.

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