Low-activation high-hardness medium-entropy steel and preparation method thereof

Abstract

The invention discloses low-activation high-hardness medium-entropy steel and a preparation method thereof, and belongs to the technical field of medium-entropy alloys. The alloy molecular formula of the medium-entropy steel is FeaCrbAlcMndTieVf, and according to the atomic mole percentage in each component, a + b + c + d + e + f = 100, a = 100-(b + c + d + e + f), b = 12-43, c = 9-35, d = 7-13, e = 5-9, and f = 0-4. The alloy molecular formula of the medium-entropy steel is as follows: a + b + c + d + e + f = 100, a = 100-(b + c + d + e + f), b = 12-43, c = 9-35, d = 7-13, e = 5-9, and f = 0-4. The medium-entropy steel is a non-equal-atomic-ratio medium-entropy alloy, and the structure of the medium-entropy steel is composed of a body-centered cubic solid solution phase. The preparation method comprises the steps that burdening is conducted according to the proportion of the raw materials, the raw materials are placed in a crucible, smelting is conducted under the 5 * 10 <-3 > Pa vacuum and inert gas protection environment, during smelting, Al and Mn are placed at the bottom of the crucible, and Cr, Ti and V are placed on the upper layer of the crucible; and the alloy liquid obtained after uniform smelting is solidified and formed, and the medium-entropy steel is obtained. According to steel components in the medium-entropy steel, the proportion of non-noble metal elements is remarkably increased, a simple and stable phase structure can be formed, the economic cost is remarkably reduced, and meanwhile, due to the fact that the medium-entropy steel has the body-centered cubic solid solution phase, the medium-entropy steel has higher hardness compared with other medium-entropy steel.

Description

Technical Field

[0001] The present invention belongs to the technical field of medium-entropy alloys, and in particular relates to a low-activation high-hardness medium-entropy steel and a preparation method thereof. Background Art

[0002] Steel is a vital industrial material, widely used in mechanical components, civil engineering, and cutting tools. The development of high-end manufacturing industries, such as aerospace, energy, and automotive, is placing higher demands on the comprehensive performance of materials. Traditional alloys have performance limitations in certain extreme environments (such as high and low temperatures, and severe corrosion), making traditional steel increasingly unable to adapt to the rapid technological advancements of modern society.

[0003] With the development of high-entropy alloys, a new steel concept, medium-entropy steel, has been proposed to improve the mechanical properties of traditional steel. Its mixing entropy is higher than that of ordinary steel, and it contains more iron than traditional high-entropy alloys. The high proportion of iron reduces the configurational entropy and improves the cost-effectiveness of medium-entropy steel. Through multi-element alloying design, medium-entropy steel can exhibit excellent mechanical properties and durability under various complex working conditions. At present, although multi-component medium-entropy steel has many excellent properties, due to the use of a large amount of precious metal elements, its economic cost is very high compared to traditional steel materials, making it very difficult to achieve industrial production.

[0004] Therefore, there is an urgent need to design a medium-entropy steel material with a higher proportion of non-precious metal elements, which can reduce production costs while maintaining certain performance requirements. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the use of a large amount of precious metal elements in existing multi-component medium-entropy steels makes industrial production difficult, and to provide a low-activation, high-hardness medium-entropy steel and a preparation method thereof, so as to increase the proportion of non-precious metal elements, reduce the production cost of the material, and at the same time make it have higher hardness.

[0006] To achieve the above object, the present invention adopts the following technical solution: a low activation high hardness medium entropy steel, the alloy formula of the medium entropy steel is Fe a Cr b Al c Mn d Ti e V f , where the atomic molar percentage of each component is: a+b+c+d+e+f=100, a=100-(b+c+d+e+f), b=12~43, c=9~35, d=7~13, e=5~9, f=0~4.

[0007] Furthermore, the medium entropy steel is a non-equiatomic medium entropy alloy, and its structure is composed of a body-centered cubic solid solution phase.

[0008] Furthermore, each alloy raw material in the medium entropy steel is a pure metal sheet or cylindrical particle with a purity greater than 99%.

[0009] The present invention also discloses a method for preparing low-activation, high-hardness, medium-entropy steel, comprising the following steps: S1. Fe, Cr, Al, Mn, Ti, and V are prepared according to the atomic molar percentage of the components, wherein Fe is 100-(b+c+d+e+f)%, Cr is 12-43%, Al is 9-35%, Mn is 7-13%, Ti is 5-9%, and V is 0-4%; S2, put the above components into a crucible, -3 The smelting is carried out under a vacuum degree of Pa and an inert gas protection environment. During smelting, Al and Mn are placed at the bottom of the crucible, and Cr, Ti, and V are placed on the upper layer of the crucible. S3. Solidifying and forming the alloy liquid obtained after uniform melting to obtain the medium entropy steel.

[0010] Furthermore, in step S2, argon is used as the inert gas, and argon is filled until the pressure in the furnace reaches half the atmospheric pressure.

[0011] Furthermore, in step S2, the smelting method adopts vacuum induction melting and stepped induction heating. The stepped power should be 15kw~30kw, 50kw~100kw, and 100kw~150kw respectively. The heating time is 2~3 minutes, 4~5 minutes, and 7~8 minutes respectively. The smelting process is repeated 2~3 times.

[0012] Furthermore, in step S3, the molding method is casting or suction casting.

[0013] The beneficial effects of the present invention are: 1) The steel composition of the medium-entropy steel prepared by the present invention significantly increases the proportion of non-precious metal elements, which not only forms a simple and stable phase structure but also significantly reduces economic costs. At the same time, due to its body-centered cubic solid solution phase, it has higher hardness than other medium-entropy steels.

[0014] 2) The medium entropy steel of the present invention has good high-temperature stability and can still maintain good hardness after high-temperature annealing, overcoming the high-temperature softening problem that is difficult to solve for traditional alloys.

[0015] 3) The preparation process of the present invention adopts vacuum induction melting, which has a simple process, a short preparation flow and high production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the metallographic diagram of the medium entropy steel in Example 2; Figure 2 The hardness comparison diagram of three test points of the medium entropy steel in each embodiment is selected; Figure 3 This is the X-ray diffraction pattern of the medium entropy steel after annealing at 900 degrees Celsius in Example 1. DETAILED DESCRIPTION

[0017] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0018] Example 1: The present invention provides a low activation high hardness medium entropy steel, the alloy formula of which is Fe 25 Cr 18 Al 35 Mn 13 Ti5V4, the alloy structure consists of a body-centered cubic solid solution phase.

[0019] The preparation steps are as follows: Fe, Cr, Al, Mn, Ti, and V flake raw materials with a purity greater than 99% were weighed according to the atomic molar percentages shown in the molecular formula and then placed in a copper crucible of a vacuum electromagnetic induction melting furnace. The sample chamber of the vacuum magnetic levitation melting furnace was evacuated, and when the vacuum degree reached 5×10 -3 After Pa, industrial argon is filled until the pressure in the furnace reaches half atmosphere, and 30kw, 80kw, and 120kw step-by-step power induction heating are used, and the heating time is 2-3 minutes, 4-5 minutes, and 7-8 minutes respectively. The smelting process needs to be repeated 3 times to obtain a molten alloy; the melted alloy is cast to obtain a medium-entropy steel alloy ingot with uniform composition.

[0020] Example 2: The present invention provides a low activation high hardness medium entropy steel, the alloy formula of which is Fe 63 Cr 12 Al9Mn7Ti5V4, the alloy structure consists of a body-centered cubic solid solution phase.

[0021] The preparation steps are as follows: The Fe, Cr, Al, Mn, Ti, and V granular raw materials with a purity greater than 99% were weighed according to the atomic molar percentage shown in the molecular formula and then placed in a copper crucible of an electromagnetic induction furnace. The sample chamber of the vacuum magnetic levitation melting furnace was evacuated. When the vacuum degree reached 5×10 -3 After Pa, industrial argon is filled until the pressure in the furnace reaches half atmosphere, and 15kw, 50kw, and 100kw step-by-step power induction heating are used, and the heating time is 2-3 minutes, 4-5 minutes, and 7-8 minutes respectively. The smelting process needs to be repeated 3 times to obtain a molten alloy; the melted alloy is cast to obtain a medium-entropy steel alloy ingot with uniform composition.

[0022] Example 3: The present invention provides a low activation high hardness medium entropy steel, the alloy formula of which is Fe 20 Cr 43 Al 17 Mn 11 Ti7V2, the alloy structure consists of a body-centered cubic solid solution phase.

[0023] The preparation steps are as follows: The Fe, Cr, Al, Mn, Ti, and V granular raw materials with a purity greater than 99% were weighed according to the atomic molar percentage shown in the molecular formula and then placed in a copper crucible of an electromagnetic induction furnace. The sample chamber of the vacuum magnetic levitation melting furnace was evacuated. When the vacuum degree reached 5×10 -3 After Pa, industrial argon is filled until the pressure in the furnace reaches half atmosphere, and 30kw, 100kw, and 150kw step-by-step induction heating are performed, with heating times of 2-3 minutes, 4-5 minutes, and 7-8 minutes, respectively. The smelting process needs to be repeated three times to obtain a molten alloy; the melted alloy is suction-casted to obtain a medium-entropy steel alloy ingot with uniform composition.

[0024] Example 4: The present invention provides a low activation high hardness medium entropy steel, the alloy formula of which is Fe 35 Cr 18 Al 25 Mn 13 Ti9, the alloy structure consists of a body-centered cubic solid solution phase.

[0025] The preparation steps are as follows: Fe, Cr, Al, Mn, and Ti flake raw materials with a purity greater than 99% were weighed according to the atomic molar percentages shown in the molecular formula and then placed in a copper crucible of an electromagnetic induction furnace. The sample chamber of the vacuum magnetic levitation melting furnace was evacuated. When the vacuum degree reached 5×10 -3 After reaching 1.5 Pa, industrial argon is introduced until the furnace pressure reaches half atmosphere. Induction heating is performed in a stepped power range of 25 kW, 70 kW, and 130 kW, with heating times of 2-3 minutes, 4-5 minutes, and 7-8 minutes, respectively. This melting process is repeated twice to obtain a molten alloy. The molten alloy is suction-casted to obtain a medium-entropy steel alloy ingot with uniform composition.

[0026] Figure 1 These are the metallographic images of the medium-entropy steel in Example 2, where the upper two images are metallographic images under a 5x microscope, and the lower two images are metallographic images under a 20x microscope. It can be seen that under low-magnification observation, some phase structures inside the alloy material sample are concentrated in certain areas, such as the MnV phase, and some other free phase structures exist in these concentrated areas; further magnification observation and analysis shows that some free phase structures are still freely distributed in the system.

[0027] Composed of the alloy elements of Examples 1 to 4 above and Figure 2 It can be seen from the performance test results that when the Fe and Cr contents in the alloy are high, the alloy steel can exhibit higher hardness, while when the Al content is too high, the hardness of the alloy steel will decrease; and different step heating powers will cause the hardness to change. When the heating power is high, it will cause Al to burn and volatilize, thereby reducing the Al content and increasing the hardness of the alloy steel.

[0028] Figure 3 This is the X-ray diffraction pattern of the medium-entropy steel after annealing at 900 degrees Celsius in Example 1. It can be seen from the figure that the body-centered cubic solid solution phase and intermetallic compounds in the alloy are both present after high-temperature annealing, indicating that the structure of the medium-entropy steel is relatively stable at high temperatures.

[0029] The steel composition in the medium-entropy steel prepared by the present invention significantly increases the proportion of non-precious metal elements, which can not only form a simple and stable phase structure, but also significantly reduce the economic cost. At the same time, because it has a body-centered cubic solid solution phase, it has higher hardness than other medium-entropy steels.

[0030] The above description is only used to illustrate the technical solution of the present invention and is not intended to limit the present invention. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in this field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A low activation, high hardness, medium entropy steel, characterized by: The alloy formula of the medium entropy steel is Fe a Cr b Al c Mn d Ti e V f , where the atomic molar percentage of each component is: a+b+c+d+e+f=100, a=100-(b+c+d+e+f), b=12~43, c=9~35, d=7~13, e=5~9, f=0~4.

2. The low activation, high hardness, medium entropy steel according to claim 1, characterized in that: The medium entropy steel is a non-equiatomic medium entropy alloy, and its structure consists of a body-centered cubic solid solution phase.

3. The low activation, high hardness, medium entropy steel according to claim 1, characterized in that: All alloy raw materials in the medium entropy steel are pure metal sheets or cylindrical particles with a purity greater than 99%.

4. The method for preparing low-activation, high-hardness, medium-entropy steel according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Fe, Cr, Al, Mn, Ti, and V are prepared according to the atomic molar percentage of the components, wherein Fe is 100-(b+c+d+e+f)%, Cr is 12-43%, Al is 9-35%, Mn is 7-13%, Ti is 5-9%, and V is 0-4%; S2, put the above components into a crucible, -3 The smelting is carried out under a vacuum degree of Pa and an inert gas protection environment. During smelting, Al and Mn are placed at the bottom of the crucible, and Cr, Ti, and V are placed on the upper layer of the crucible. S3. Solidifying and forming the alloy liquid obtained after uniform melting to obtain the medium entropy steel.

5. The preparation method according to claim 4, characterized in that: In step S2, argon is used as the inert gas, and argon is filled until the pressure in the furnace reaches half the atmospheric pressure.

6. The preparation method according to claim 4, characterized in that: In step S2, vacuum induction melting is used for smelting, and stepped induction heating is adopted. The stepped power should be 15kw~30kw, 50kw~100kw, and 100kw~150kw respectively. The heating time is 2~3 minutes, 4~5 minutes, and 7~8 minutes respectively. The smelting process is repeated 2~3 times.

7. The preparation method according to claim 4, characterized in that: In step S3, the molding method is casting or suction casting.

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