A low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and a preparation method thereof

Abstract

The present application relates to a kind of low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method, belong to low-temperature structural material and its preparation technical field.The purpose of the present application is to provide a kind of low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method, comprising the following steps: by vacuum magnetic suspension melting preparation as-cast FeCoCrNiMn multi-principal element alloy, after 24h solid solution treatment at 1200°C, again by cryogenic rolling under liquid helium temperature is reduced to the thickness of solid solution treatment alloy 60%, finally annealing treatment 5min at 680°C, obtain double-scale heterogeneous FeCoCrNiMn multi-principal element alloy.The present application is combined by extremely low-temperature cryogenic rolling and medium-temperature rapid annealing process, significantly improves the dynamic yield strength of FeCoCrNiMn multi-principal element alloy in low-temperature environment.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature structural materials and their preparation technology, specifically relating to a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal-element alloy and its preparation method. Background Technology

[0002] Structural materials are inevitably affected by extreme environments under extreme operating conditions. To prevent catastrophic failures during service, there is an urgent need for materials with sufficient mechanical properties over a wide temperature range from room temperature to cryogenic temperatures. Generally, the strength of most metals or alloys increases with decreasing temperature, but this comes at the cost of toughness. This makes it difficult to fully utilize materials that exhibit excellent mechanical properties at room temperature at low temperatures. Face-centered cubic alloys, such as austenitic stainless steel and aluminum alloys, typically retain good ductility as temperatures decrease. Recent studies have shown that certain CoCrNi-based alloys also exhibit similar properties. In particular, the FeCoCrNiMn alloy developed by Cantor et al. exhibits a tensile strength of ~1.28 GPa and a tensile strength exceeding ~270 MPa·m at 77 K. 1 / 2 Its fracture toughness is excellent. This superior performance at low temperatures is comparable to that of 9% Ni steel and stainless steel, making it a strong candidate for potential applications in extreme environments such as high strain rates and low temperatures.

[0003] However, the low yield strength is a major obstacle to the application of these materials as critical engineering components. Significant efforts have been devoted to improving this, especially under extreme loading conditions. Constructing heterostructures is an effective approach. For heterostructure grain sizes at the micrometer scale, larger grains are more flexible, providing a greater capacity to store geometrically necessary dislocations, while smaller grains are harder and more effectively resist dislocation movement. Due to the deformation incompatibility between these heterostructure components, geometrically necessary dislocations tend to accumulate at the heterostructure interface, leading to effective strain hardening. From this perspective, heterostructures involving multiple levels (e.g., a combination of nanoscale twin boundaries and micrometer-scale bimodal grain sizes) hold promise for more effectively promoting this hardening.

[0004] Patent ZL201910978598.4 invented a radiation-resistant and impact-resistant FeCoCrNiMn high-entropy alloy, but the preparation process of this alloy (copper mold suction casting-homogenization treatment-cold rolling-heat treatment-irradiation treatment) is significantly different from that of this invention, and the service conditions involve high strain rate loading at room temperature, which is also significantly different from that of this invention. Summary of the Invention

[0005] The main objective of this invention is to provide a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method. The technical problem to be solved is to achieve high yield strength of the FeCoCrNiMn multi-principal element alloy and solve the application problem of it as a key engineering component in extreme environments.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method, comprising the following steps:

[0008] 1) Fe, Co, Cr, Ni and Mn are mixed in a certain percentage and alloy ingots are obtained by vacuum magnetic levitation melting;

[0009] 2) Perform solution treatment on the alloy ingot described in step 1);

[0010] 3) The solution-treated alloy described in step 2) is subjected to deep cryogenic rolling.

[0011] 4) Anneal the hot-rolled alloy described in step 3).

[0012] Preferably, the alloy composition and molar percentage in step 1) are Fe-20%, Co-20%, Cr-20%, Ni-20%, and Mn-20%.

[0013] Preferably, in step 2), the solution treatment temperature is 1200°C, the holding time is 24 hours, and the cooling method is water cooling;

[0014] Preferably, in step 3), the alloy is immersed in liquid helium for 20 minutes before and after each pass of cryogenic rolling.

[0015] Preferably, the deformation amount of the cryogenic rolling process in step 3) is 60%;

[0016] Preferably, in step 4), the annealing temperature is 680°C, the holding time is 5 minutes, and the cooling method is water cooling.

[0017] The advantages and beneficial effects of this invention are:

[0018] 1) The room temperature strength and ductility of FeCoCrNiMn multi-principal-element alloys can be significantly improved at low temperatures without affecting toughness;

[0019] 2) The low stacking fault energy of FeCoCrNiMn multi-principal alloys at liquid helium temperature helps promote the development of planar defects;

[0020] 3) Select an appropriate annealing temperature to allow partial recrystallization. Attached Figure Description

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0022] Figure 1 The true stress-strain curves of high strain rate compression for heterogeneous FeCoCrNiMn multi-principal-element alloys;

[0023] Figure 2 A schematic diagram of the preparation process of heterogeneous FeCoCrNiMn multi-principal element alloy;

[0024] Figure 3 The results are from X-ray diffraction analysis of heterogeneous FeCoCrNiMn multi-principal element alloys.

[0025] Figure 4 The grain distribution and average nucleus misalignment of heterogeneous FeCoCrNiMn multi-principal element alloys;

[0026] Figure 5 Field emission transmission electron microscope images of nanotwins and the 9R phase in a heterogeneous FeCoCrNiMn multi-principal-element alloy. Detailed Implementation

[0027] The invention will now be described in further detail with reference to the accompanying drawings.

[0028] This invention belongs to the field of low-temperature structural materials and their preparation technology, specifically relating to a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method. The purpose of this invention is to provide a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method.

[0029] To achieve the objective of this invention, the technical solution adopted is as follows:

[0030] A low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method are disclosed. The alloy composition and molar percentage are Fe-20%, Co-20%, Cr-20%, Ni-20%, and Mn-20%.

[0031] A low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy and its preparation method, comprising the following steps:

[0032] 1) Fe, Co, Cr, Ni and Mn are mixed in a certain percentage and alloy ingots are obtained by vacuum magnetic levitation melting;

[0033] 2) Perform solution treatment on the alloy ingot described in step 1);

[0034] 3) The solution-treated alloy described in step 2) is subjected to deep cryogenic rolling.

[0035] 4) Anneal the hot-rolled alloy described in step 3).

[0036] The solution treatment temperature is 1200°C, the holding time is 24 hours, and the cooling method is water cooling;

[0037] Before and after each pass of the cryogenic rolling process, the alloy is immersed in liquid helium for 20 minutes.

[0038] The deformation amount of the deep cryogenic rolling process is 60%;

[0039] The annealing process is performed at a temperature of 680°C for 5 minutes, and the cooling method is water cooling.

[0040] The invention will now be further described in detail through comparative examples and embodiments:

[0041] Comparative Example 1

[0042] This comparative example presents a method for preparing fully recrystallized FeCoCrNiMn multi-principal element alloys:

[0043] 1) Magnetic levitation melting: Five elemental metal raw materials are mixed according to the target molar percentage (Fe-20%, Co-20%, Cr-20%, Ni-20%, Mn-20%), and a cast FeCoCrNiMn multi-principal element alloy plate with dimensions of 80mm (length) × 80mm (width) × 10mm (thickness) is prepared by vacuum magnetic levitation melting technology;

[0044] 2) Solution treatment: The solution treatment temperature is 1200°C, the holding time is 24 hours, and the cooling method is water cooling;

[0045] 3) Deep cryogenic rolling treatment: The deformation amount of deep cryogenic rolling is 60%, and the alloy is immersed in liquid helium for 20 minutes before and after each pass;

[0046] 4) Annealing treatment: The annealing temperature is 900°C, the holding time is 10 minutes, and the cooling method is water cooling;

[0047] 5) Mechanical Testing: Cylindrical samples with a height and diameter of 3 mm were cut from the annealed alloy sheet obtained in step 4) using wire cutting. High-strain-rate compression tests were conducted on the cylindrical samples at a compressive strain rate of 2.1 × 10³ s⁻¹ using a Hopkinson test apparatus equipped with a cryogenic cooling system. To reduce friction, the contact interface between the rod and the sample was thoroughly lubricated with molybdenum disulfide before each loading. The actual stress-strain curves were output using Origin software; see [link to Origin software]. Figure 1 As shown, the low-temperature yield strength of the annealed multi-principal element alloy is 707 MPa, and the low-temperature maximum compressive plasticity is 17.5%.

[0048] Example 1

[0049] This invention proposes a method for preparing partially recrystallized FeCoCrNiMn multi-principal element alloys:

[0050] 1) Magnetic levitation melting: Five elemental metal raw materials are mixed according to the target molar percentage (Fe-20%, Co-20%, Cr-20%, Ni-20%, Mn-20%), and a cast FeCoCrNiMn multi-principal element alloy plate with dimensions of 80mm (length) × 80mm (width) × 10mm (thickness) is prepared by vacuum magnetic levitation melting technology;

[0051] 2) Solution treatment: The solution treatment temperature is 1200°C, the holding time is 24 hours, and the cooling method is water cooling;

[0052] 3) Deep cryogenic rolling treatment: The deformation amount of deep cryogenic rolling is 60%, and the alloy is immersed in liquid helium for 20 minutes before and after each pass;

[0053] 4) Annealing treatment: The annealing temperature is 680°C, the holding time is 5 minutes, and the cooling method is water cooling;

[0054] 5) Mechanical Testing: Cylindrical samples with a height and diameter of 3 mm were cut from the annealed alloy sheet obtained in step 4) using wire cutting. High-strain-rate compression tests were conducted on the cylindrical samples at a compressive strain rate of 2.1 × 10³ s⁻¹ using a Hopkinson test apparatus equipped with a cryogenic cooling system. To reduce friction, the contact interface between the rod and the sample was thoroughly lubricated with molybdenum disulfide before each loading. The actual stress-strain curves were output using Origin software; see [link to Origin software]. Figure 1 As shown, the low-temperature yield strength of the annealed multi-principal element alloy is 1382 MPa, and the low-temperature maximum compressive plasticity is 18.4%.

[0055] 6) Phase composition analysis of the rolled-annealed alloy was performed using X-ray diffraction with scanning angles ranging from 20° to 100°. See the results below. Figure 3 As shown, characteristic peaks corresponding to the (111), (200), (220), (311) and (222) crystal planes were found in the X-ray diffraction spectrum, indicating that the rolled-annealed alloy formed a single face-centered cubic phase structure;

[0056] 7) Electron backscattering diffraction was used to perform crystallographic analysis on the rolled-annealed alloy with a step size of 0.2 μm. The results are shown in [reference needed]. Figure 4As shown, the rolled-annealed alloy is characterized by two sets of FCC grains of different sizes, indicating partial recrystallization. Smaller grains were identified as recrystallized grains, while larger grains were considered non-recrystallized grains. Statistical analysis results show that fine grains with a grain size less than or equal to 5 μm (average grain size: ~0.75 μm) account for approximately ~30% of the total volume, while coarse grains with a grain size greater than 5 μm (average grain size: ~11.9 μm) account for approximately ~70%. Furthermore, the nucleus-averaged dislocation results indicate that dislocations tend to be distributed in the non-recrystallized grains;

[0057] 8) Field emission transmission electron microscopy was used to perform nanoscale analysis on the rolled-annealed alloy. The results are shown in [reference needed]. Figure 5 As shown, the results indicate the presence of nanotwins and 9R phase in the rolled-annealed alloy, with thicknesses of approximately 10-25 nm and 15-30 nm, respectively.

[0058] The results of the embodiments show that the present invention enables the partial recrystallization of FeCoCrNiMn multi-principal alloy through a series of rolling-annealing processes, and exhibits heterogeneity on two levels: microscopic heterogeneity in terms of grain structure and nanoscale heterogeneity involving dislocations, nanotwins and 9R phase. This dual-scale heterogeneous structure significantly improves the yield strength of FeCoCrNiMn multi-principal alloy, endowing it with excellent mechanical properties under extreme loads, which are far superior to similar fully recrystallized alloys.

[0059] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the basic principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy, characterized in that, Includes the following steps: Step 1): Mix the five elemental metals according to their molar percentages and perform vacuum magnetic levitation melting to obtain an alloy ingot; Step 2): The alloy ingot is subjected to solution treatment, deep cryogenic rolling and annealing in sequence to obtain an alloy sample.

2. The method for preparing a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy according to claim 1, characterized in that, The alloy composition and molar percentage in step 1) are: Fe-20%, Co-20%, Cr-20%, Ni-20%, Mn-20%.

3. The method for preparing a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy according to claim 1, characterized in that, In step 2), the solution treatment temperature is 1200°C, the holding time is 24 hours, and the cooling method is water cooling.

4. The method for preparing a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy according to claim 1, characterized in that, In step 2), the alloy is immersed in liquid helium for 20 minutes before and after each deep cold rolling process.

5. The method for preparing a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy according to claim 1, characterized in that, The deformation amount of the deep cold rolling process in step 2) is 60%.

6. The method for preparing a low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy according to claim 1, characterized in that, In step 2), the annealing temperature is 680°C, the holding time is 5 minutes, and the cooling method is water cooling.

7. A low-temperature impact-resistant heterogeneous FeCoCrNiMn multi-principal element alloy, characterized in that, Prepared by any one of the preparation methods according to claims 1-6.

Images