High-toughness dual-phase iron-based medium-entropy alloy and preparation method thereof

Abstract

The application discloses a high-strength and high-toughness dual-phase iron-based medium-entropy alloy and a preparation method thereof, and relates to the field of alloy materials. The alloy comprises the following components in mass percentage: Fe: 64.5%, Co: 5.5%, Cr: 12.6%, Ni: 11%, Al: 1.0%, Si: 3.6% and Mo: 1.8%. The high-strength and high-toughness dual-phase iron-based medium-entropy alloy is obtained through the following steps: preparing raw materials, smelting, rolling forming, recrystallization annealing, microscopic structure observation and mechanical property testing. The medium-entropy alloy has a yield strength of 1.1 GPa at room temperature, a tensile strength of 1.2 GPa and an elongation of 44%, and therefore, the alloy has excellent strength and plasticity synergy at room temperature and excellent comprehensive performance. The medium-entropy alloy saves the content of high-cost elements, reduces the cost, is beneficial to large-scale production and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of alloy materials, and in particular to a high-strength and high-toughness dual-phase iron-based medium-entropy alloy and its preparation method. Background Technology

[0002] High-entropy alloys, as a novel alloy system composed of five or more elements, exhibit four unique effects: high-entropy effect, lattice distortion, slow diffusion, and cocktail effect. Medium-entropy alloys are a product of the design and development of high-entropy alloys towards alloying. In recent years, iron-based medium-entropy alloys have attracted widespread attention due to their excellent tensile properties and low cost. Improving their strength-ductility balance is a key direction for researchers to continuously optimize their performance. Current research focuses on FeCoNi, FeCoNiCr, and FeNiCr systems, which typically have low yield strengths (<700 MPa). Iron-based medium-entropy alloys with high yield strength often have low elongation (<15%). Furthermore, these alloy systems contain large amounts of the high-cost element Co, which significantly limits their large-scale application. Therefore, developing low-cost alloy systems with high strength and ductility is of great research significance and application value. Thus, it is necessary to provide a high-strength, high-toughness, dual-phase iron-based medium-entropy alloy and its preparation method to solve the above problems. Summary of the Invention

[0003] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0004] A high-strength and high-toughness dual-phase iron-based medium-entropy alloy comprises, by mass percentage: Fe: 64.5%, Co: 5.5%, Cr: 12.6%, Ni: 11%, Al: 1.0%, Si: 3.6%, and Mo: 1.8%; wherein the Fe, Co, Cr, Ni, Al, Si, and Mo metal raw materials are all high-purity raw materials, each ≥99.99 wt.%.

[0005] This invention also discloses a method for preparing a high-strength and high-toughness dual-phase iron-based medium-entropy alloy, comprising the following steps:

[0006] Step 1: Prepare raw materials: The total mass of the arc-melted master alloy is 50g. Take Fe, Co, Cr, Ni, Al, Si, and Mo metal raw materials for pretreatment. First, use a grinding wheel or a small electric drill to grind away the oxide scale on the metal surface. Weigh and mix them according to the mass percentages of Fe: 64.5%, Co: 5.5%, Cr: 12.6%, Ni: 11%, Al: 1.0%, Si: 3.6%, and Mo: 1.8%. Then weigh the calculated raw materials on a balance with an accuracy of 0.001g and weigh them again. Then ultrasonically clean them with anhydrous ethanol and dry them with a hair dryer to make the metal surfaces clean.

[0007] Step Two, Melting: Before melting, place the weighed alloy into a copper mold capable of electromagnetic stirring. After placing the raw materials, close the chamber door tightly. Then, turn on the mechanical pump to achieve a vacuum of 5 Pa inside the chamber, and then turn on the molecular pump to maintain a vacuum of 5 × 10⁻⁶ Pa. -3 Pa, turn off the molecular pump, turn the alloy ingot over after each melting and cooling, and perform electromagnetic stirring every time the alloy is completely melted into a liquid state so that the alloy can be fully mixed and uniform. Each electromagnetic stirring time is 40-60 seconds. Finally, place the uniformly melted alloy ingot on a copper mold for suction casting, and cast it into the copper mold under the action of the alloy's own gravity, finally forming an alloy block of 40mm×10mm×10mm.

[0008] Step 3: Rolling and forming: The speed of the upper and lower rolls of the rolling mill is 10m / s (3.4r / min), and the total deformation of the alloy steel ingot during cold rolling is 80%-85%;

[0009] Step 4, recrystallization annealing: Place the rolled plate in an annealing furnace at 1073K for 10 minutes, and then immediately quench it in water;

[0010] Step 5: Microstructure observation and mechanical property testing: The sample was mounted using dental plaster powder. Then, the sample was successively polished on sandpaper using 240#, 400#, 600#, 800#, 1000#, 1200#, and 1500# polishing sandpaper until the surface was smooth. Mechanical polishing was then performed using 2.5μm polishing fluid until the sample surface appeared smooth and even showed fine grain distribution under a light microscope. Simple room-temperature phase analysis was performed using CT tomography X-ray diffraction with Cu as the target material. Mechanical property testing was conducted according to GB / T 228.1-2021. A uniaxial tensile test was performed using a universal testing machine driven by a screw with a rated load of 100kN at a speed of 0.5mm / min to obtain the stress-strain curve.

[0011] Preferably, in step one, the mass of each raw material has an error of ±0.002g during the weighing process.

[0012] Preferably, in step two, all alloys are melted by electric arc and protected in an argon atmosphere. High-purity argon is used as a protective gas to facilitate arc ignition. The entire copper mold, suction casting mold, and electric arc melting chamber are connected to a water cooling device to ensure the cooling of the mold and alloys.

[0013] Beneficial effects of the present invention: Compared with the prior art, the beneficial effects of the present invention are:

[0014] (1) The room temperature yield strength of this medium entropy alloy is as high as 1.1 GPa, the tensile strength is as high as 1.2 GPa, and the elongation is as high as 44%. It can be seen that the alloy has a superior synergistic effect of strength and plasticity at room temperature and excellent comprehensive performance.

[0015] (2) This medium-entropy alloy saves on the content of high-cost elements, reduces its cost, is conducive to large-scale production, and has broad application prospects. Attached Figure Description

[0016] Figure 1 XRD patterns for the embodiments and comparative examples;

[0017] Figure 2 TEM image of the medium-entropy alloy in the example;

[0018] Figure 3 The EBSD phase distribution diagram of the medium-entropy alloy in the example is shown.

[0019] Figure 4 Stress-strain curves for the embodiments and comparative examples;

[0020] Figure 5 The EBSD phase distribution diagram is shown in the example diagram after stretching of the medium-entropy alloy.

[0021] Figure 6 The fracture morphology of the medium-entropy alloy after stretching is shown in the example. Detailed Implementation

[0022] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0023] Example

[0024] like Figures 1 to 6 As shown, a high-strength and high-toughness dual-phase iron-based medium-entropy alloy comprises: by mass percentage, Fe: 64.5%, Co: 5.5%, Cr: 12.6%, Ni: 11%, Al: 1.0%, Si: 3.6%, and Mo: 1.8%, denoted as Al2Mo according to atomic ratio; the Fe, Co, Cr, Ni, Al, Si, and Mo metal raw materials are all high-purity raw materials, all ≥99.99 wt.%.

[0025] This invention also discloses a method for preparing a high-strength and high-toughness dual-phase iron-based medium-entropy alloy, comprising the following steps:

[0026] Step 1: Prepare raw materials: The total mass of the arc-melted master alloy is 50g. Take Fe, Co, Cr, Ni, Al, Si, and Mo metal raw materials for pretreatment. First, use a grinding wheel or a small electric drill to grind away the oxide scale on the metal surface. Weigh and mix them according to the mass percentages of Fe: 64.5%, Co: 5.5%, Cr: 12.6%, Ni: 11%, Al: 1.0%, Si: 3.6%, and Mo: 1.8%. Then weigh the calculated raw materials on a balance with an accuracy of 0.001g and weigh them again. Then ultrasonically clean them with anhydrous ethanol and dry them with a hair dryer to make the metal surfaces clean.

[0027] Step Two, Melting: Before melting, place the weighed alloy into a copper mold capable of electromagnetic stirring. After placing the raw materials, close the chamber door tightly. Then, turn on the mechanical pump to achieve a vacuum of 5 Pa inside the chamber, and then turn on the molecular pump to maintain a vacuum of 5 × 10⁻⁶ Pa. -3 Pa, turn off the molecular pump. During the melting process, in order to ensure the uniformity of the alloy, the alloy needs to be melted 5 times. After each melting and cooling, the alloy ingot is turned over. When the alloy is completely melted into a liquid state, electromagnetic stirring is performed to ensure that the alloy is fully mixed and uniform. Each electromagnetic stirring time is 40-60 seconds. The time should not be too long to prevent the cavity from overheating. Finally, the uniformly melted alloy ingot is placed on a copper mold for suction casting. Under the action of the alloy's own gravity, it is cast into the copper mold, finally forming an alloy block of 40mm×10mm×10mm.

[0028] Step 3: Rolling and forming: The speed of the upper and lower rolls of the rolling mill is 10m / s (3.4r / min). The total deformation of the alloy steel ingot during cold rolling is 80%-85%. Because the reduction rate is required to be large during rolling, the entry angle must be controlled to avoid the sample failing to be rolled successfully. The reduction amount can be reduced each time and the rolling can be repeated multiple times.

[0029] Step 4, recrystallization annealing: Place the rolled plate in an annealing furnace at 1073K for 10 minutes, and then immediately quench it in water;

[0030] Step 5: Microstructure Observation and Mechanical Property Testing: Due to the small size of the sample, it was difficult to grind. Dental plating powder was used for mounting. The sample was then successively polished on sandpaper using 240#, 400#, 600#, 800#, 1000#, 1200#, and 1500# polishing sandpaper until the surface was smooth. Mechanical polishing was then performed using 2.5μm polishing fluid until the sample surface was smooth and even showed fine grain distribution under a light microscope. Simple room-temperature phase analysis was performed using CT tomography X-ray diffraction, with Cu as the target material. Figure 1 and Figure 3It can be seen that this medium-entropy alloy consists of two phases, FCC and BCC. Mechanical property tests were conducted according to GB / T228.1-2021. A uniaxial tensile test was performed using a universal testing machine driven by a screw with a rated load of 100kN at a speed of 0.5mm / min to obtain the stress-strain curves, as shown below. Figure 4 The alloy shown has a yield strength of 1.1 GPa.

[0031] In step one, the mass of each raw material has an error of ±0.002g during the weighing process.

[0032] In step two, all alloys are melted by electric arc and protected in an argon atmosphere. High-purity argon is used as a protective gas to facilitate arc ignition. The entire copper mold, suction casting mold, and electric arc melting chamber are connected to a water cooling device to ensure the cooling of the mold and alloy.

[0033] To illustrate the superior performance of this application, the following comparative examples are provided:

[0034] Comparative Example

[0035] The difference from the embodiment is that Mo is not added, and the mass percentage of each element differs, specifically as follows: by mass percentage, it includes: Fe: 65.4%, Co: 5.6%, Cr: 12.7%, Ni: 11.1%, Al: 1.5%, Si: 3.7%, denoted as Al3 according to atomic ratio; the Fe, Co, Cr, Ni, Al, and Si metal raw materials are all high-purity raw materials, all ≥99.99 wt.%. A comparative alloy was prepared according to the preparation method of the embodiment, except that in step one, the mass percentage of each element is: Fe: 65.4%, Co: 5.6%, Cr: 12.7%, Ni: 11.1%, Al: 1.5%, Si: 3.7%, while other steps are the same.

[0036] Through mechanical property testing of the examples and comparative samples, the advantages of the examples are as follows: the room temperature yield strength of this medium-entropy alloy is as high as 1.1 GPa, the tensile strength is as high as 1.2 GPa, and the elongation is as high as 44%. It can be seen that the alloy has a superior synergistic effect of strength and plasticity at room temperature, and its comprehensive performance is excellent.

[0037] In addition, this medium-entropy alloy saves on the content of high-cost elements, reduces its cost, is conducive to large-scale production, and has broad application prospects.

[0038] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A high-strength and high-toughness dual-phase iron-based medium-entropy alloy, characterized in that, include: The composition by mass percentage is: Fe: 64.5%, Co: 5.5%, Cr: 12.6%, Ni: 11%, Al: 1.0%, Si: 3.6%, Mo: 1.8%; the Fe, Co, Cr, Ni, Al, Si and Mo metal raw materials are all high-purity raw materials, all ≥99.99wt.%.

2. The method for preparing a high-strength and high-toughness dual-phase iron-based medium-entropy alloy according to claim 1, characterized in that: Includes the following steps: Step 1: Prepare raw materials: The total mass of the arc-melted master alloy is 50g. Take Fe, Co, Cr, Ni, Al, Si, and Mo metal raw materials for pretreatment. First, use a grinding wheel or a small electric drill to grind away the oxide scale on the metal surface. Weigh and mix them according to the mass percentages of Fe: 64.5%, Co: 5.5%, Cr: 12.6%, Ni: 11%, Al: 1.0%, Si: 3.6%, and Mo: 1.8%. Then weigh the calculated raw materials on a balance with an accuracy of 0.001g and weigh them again. Then ultrasonically clean them with anhydrous ethanol and dry them with a hair dryer to make the metal surfaces clean. Step Two, Melting: Before melting, place the weighed alloy into a copper mold capable of electromagnetic stirring. After placing the raw materials, close the chamber door tightly. Then, turn on the mechanical pump to achieve a vacuum of 5 Pa inside the chamber, and then turn on the molecular pump to maintain a vacuum of 5 × 10⁻⁶ Pa. -3 Pa, turn off the molecular pump, and fill with high-purity argon gas. After each melting and cooling, turn the alloy ingot over and perform electromagnetic stirring whenever the alloy is completely melted into a liquid state. Each electromagnetic stirring time is 40-60 seconds. Finally, place the uniformly melted alloy ingot on a copper mold for suction casting and cast it into the copper mold under the action of the alloy's own gravity to form an alloy block of 40mm×10mm×10mm. Step 3: Rolling and forming: The speed of both the upper and lower rolls of the rolling mill is 3.4 r / min, and the total deformation of the alloy steel ingot during cold rolling is 80%-85%; Step 4, recrystallization annealing: Place the rolled sheet in an annealing furnace at 1073K for 10 minutes, and then immediately quench it in water; Step 5: Microstructure observation and mechanical property testing: The sample was mounted using dental plaster powder. Then, the sample was successively polished on sandpaper using 240#, 400#, 600#, 800#, 1000#, 1200#, and 1500# polishing sandpaper until the surface was smooth. Mechanical polishing was then performed using 2.5μm polishing fluid until the sample surface appeared smooth and even showed fine grain distribution under a light microscope. Simple room-temperature phase analysis was performed using CT tomography X-ray diffraction with Cu as the target material. Mechanical property testing was conducted according to GB / T228.1_2021. A uniaxial tensile test was performed using a universal testing machine driven by a screw with a rated load of 100kN at a speed of 0.5mm / min to obtain the stress-strain curve.

3. The method for preparing a high-strength and high-toughness dual-phase iron-based medium-entropy alloy according to claim 2, characterized in that: In step one, the mass of each raw material has an error of ±0.002g during the weighing process.

4. The method for preparing a high-strength and high-toughness dual-phase iron-based medium-entropy alloy according to claim 2, characterized in that: In step two, all alloys are melted by electric arc and protected in an argon atmosphere. The entire copper mold, suction casting mold and electric arc melting chamber are connected to a water cooling device to ensure the cooling of the mold and alloys.

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