A Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material and its preparation method

Abstract

This invention discloses a Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material and its preparation method. The nominal atomic percentage composition of the Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material is (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 100‑x Mn x Where 5 ≤ x ≤ 15. The preparation method includes weighing Ni, Co, Cr, Mo and Mn raw materials according to the proportions, arc melting under an inert atmosphere, repeated ingot remelting and casting, followed by homogenization heat treatment, water quenching, cold rolling and recrystallization annealing to obtain a single-phase face-centered cubic recrystallized structure. By controlling the Mn content, the formation and distribution of the ε phase during low-temperature deformation can be regulated, the coarse through-phase network can be suppressed, and the low-temperature fracture resistance, ductility and strength-plasticity matching performance of the alloy at 77 K can be improved.

Description

Technical Field

[0001] This invention relates to the field of multi-principal element alloy materials technology, and in particular to a Ni-Co-Cr-Mo-Mn multi-principal element low-temperature alloy material and its preparation method. Background Technology

[0002] Multi-principal element alloys (MPAs) possess high strength, high plasticity, good fracture toughness, and excellent environmental adaptability, making them promising candidates for applications in low-temperature structural materials. In particular, face-centered cubic Ni-Co-Cr based MPAs exhibit high work hardening capacity and good low-temperature mechanical properties due to their low stacking fault energy. During low-temperature deformation, MPAs can sequentially activate various deformation mechanisms, including planar dislocation slip, stacking faults, deformation twinning, and stress-induced phase transformation.

[0003] However, existing Ni-Co-Cr based multi-principal alloys often undergo a stress-induced transformation from a face-centered cubic phase to a hexagonal close-packed phase when a strong phase transformation-induced plasticity mechanism is introduced at low temperatures. While this transformation helps improve the material's strength, if the resulting ε phase further grows, connects, or even forms a through-network, it can easily lead to significant deformation inconsistencies and localized strain concentrations at the matrix-phase interface. This, in turn, can cause crack initiation, propagation, and early cracking of the material, reducing the alloy's plasticity and limiting its application in the field of low-temperature damage-tolerant materials.

[0004] In the existing technology, research on Ni-Co-Cr based multi-principal element alloys has focused on improving strength, plasticity, or corrosion resistance. However, there is still a lack of effective material design solutions for how to achieve high plasticity, good fracture resistance, and excellent microstructure stability at low temperatures, especially how to suppress the formation of coarse through-networks of ε phase and improve low-temperature fracture resistance and comprehensive mechanical properties.

[0005] Therefore, designing a Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material with excellent strength-plasticity synergy under low-temperature conditions, which can suppress the formation of coarse through-phase networks and improve low-temperature fracture resistance, and its preparation method, has important theoretical significance and engineering application value. Summary of the Invention

[0006] Purpose of the Invention: The purpose of this invention is to provide a Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy material and its preparation method. By introducing an appropriate amount of Mn element into the Ni-Co-Cr-Mo based multi-principal-element alloy and controlling the Mn content within the range of 5 at.% to 15 at.%, the microstructure evolution behavior during low-temperature deformation is regulated, the formation, content and distribution of the ε phase are improved, and the formation of coarse, interconnected ε phase networks is suppressed, thereby improving the low-temperature fracture resistance and comprehensive mechanical properties of the material.

[0007] Technical Solution: To achieve the above objective, this invention provides a Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material, wherein the atomic percentage composition of the Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material is: (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 100-x Mn x , where 5≤x≤15.

[0008] Where x is 5 or 10.

[0009] This invention also provides a method for preparing Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy materials, comprising the following steps:

[0010] Step S1: Composition by atomic percentage (Ni) 28.2 Co 56.4 Cr 9.4 Mo6) 100-x Mn x Weigh the raw materials in the proportions specified for Ni, Co, Cr, Mo and Mn, where 5 ≤ x ≤ 15.

[0011] Step S2: The weighed Ni, Co, Cr, Mo and Mn metal elements are subjected to electric arc melting under an inert protective atmosphere, and the ingot is repeatedly turned and remelted at least 5 times to obtain a cast ingot with uniform composition.

[0012] Step S3: The material after suction casting is then sealed in a vacuum environment for high-temperature homogenization to eliminate component segregation, followed by water quenching.

[0013] Step S4: Roll the homogenized material to refine the microstructure and provide deformation energy storage for subsequent heat treatment;

[0014] Step S5: The rolled material is heat-treated and then water-quenched to refine the grain structure and obtain a recrystallized alloy structure, thereby preparing Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy material.

[0015] In step S1, the purity of the Ni, Co, Cr, Mo and Mn metallic elements is greater than or equal to 99.99%.

[0016] In step S2, to compensate for the volatilization of Mn during the smelting process, the actual Mn content added can be slightly higher than the nominal design value, but the overall content is still close to the designed atomic percentage.

[0017] Preferably, in this invention, the amount of Mn added is increased by an additional 10 wt.% Mn.

[0018] In step S2, the furnace cavity is evacuated to 10°C before melting. -3 The pressure is then increased to -0.02 MPa by Pa, followed by the introduction of argon gas. The arc melting current is ≤450 A, and the argon gas is ultra-high purity argon. To ensure uniform mixing of the various metal raw materials, the arc melting is repeated at least 5 times. After each melting, the alloy ingot is flipped over and melted again. After melting, the resulting molten alloy is cast into rod-shaped materials, preferably with a rod size of 8×8×80 mm. 3 The vacuum electric arc furnace is model Beijing Wuke Optoelectronics WK-II, and it has a suction casting function.

[0019] In step S3, the high-temperature homogenization treatment conditions are 1200 ℃ for 24 hours, and the temperature difference in the furnace is controlled within ±10℃. After the homogenization treatment is completed, the sample is quenched with water.

[0020] The specific steps in step S3 are as follows: after suction casting, the sample is sealed using a sealing machine; hydrogen is generated by electrolyzing water using a hydrogen-oxygen generator; the quartz tube is melted by burning hydrogen to encapsulate the rod-shaped material; the inside of the tube is repeatedly purged; during purging, a vacuum of 10 is drawn. -3 The tube was treated with Pa, then purged with argon gas to a pressure of -0.02 MPa, repeated three times, and then purged with argon gas to a pressure of -0.09 MPa, maintaining a vacuum inside the tube. A box-type heat treatment furnace was used, with homogenization heat treatment conditions of 1200 ℃ for 24 h and a furnace temperature difference of ±10 ℃. The tube sealing machine was model OKFKJ3000.

[0021] In step S4, the mill speed is 300 r / min, and the rolling ratio is 80%~85%. The rolling depth is preferably no more than 0.4 mm per cycle, and the rolling is repeated at least 5 times until the predetermined rolling ratio is reached. The mill model is Xingxiang Φ350-400.

[0022] In step S4, the heat treatment temperature is 1000 ℃ and the heat treatment time is 1 hour, followed by water quenching.

[0023] The Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material obtained by the above steps preferably exhibits a single-phase face-centered cubic (FCC) solid solution microstructure in the annealed state.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0025] (1) This invention introduces Mn element into Ni-Co-Cr-Mo based multi-principal element alloys and controls its content in the range of 5 at.% to 15 at.% to enable the material to obtain better comprehensive mechanical properties under low temperature conditions. According to existing experimental results, Mn5, Mn10 and Mn15 alloys all exhibit high ductility and good strength-plasticity matching performance at 77 K.

[0026] (2) This invention suppresses the formation of coarse, interconnected ε phase networks by regulating the formation, content and distribution of ε phase during low-temperature deformation, thereby reducing local strain concentration and suppressing early cracking.

[0027] (3) The preparation process adopted in this invention is clear, easy to operate, uses conventional equipment, has good repeatability, and is easy to obtain Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy materials with uniform structure and stable performance. Attached Figure Description

[0028] Figure 1 Synchrotron radiation X-ray diffraction patterns of the Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy materials obtained in Examples 1-3 and Comparative Examples 1-3 in the annealed state;

[0029] Figure 2 The engineering stress-strain curves of the Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy materials obtained in Examples 1-3 and Comparative Examples 1-3 are shown at 77 K.

[0030] Figure 3 The fracture morphology of the Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy materials obtained in Examples 1-3 and Comparative Examples 1-3 after tensile fracture at 77 K is shown.

[0031] Figure 4 Synchrotron radiation X-ray diffraction patterns of Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy materials obtained in Examples 1-3 and Comparative Examples 1-3 after tensile fracture at 77 K;

[0032] Figure 5 The EBSD phase distribution diagrams of the Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy materials obtained in Examples 1-3 and Comparative Examples 1-3 after tensile fracture at 77 K are shown. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. All equivalent substitutions, improvements and modifications made within the spirit and principles of the present invention should fall within the scope of protection of the present invention.

[0034] The vacuum electric arc furnace is model WK-Ⅱ from Beijing Wuke Optoelectronics, the rolling mill is Φ350-400 from Wuxi Xingxiang Metallurgical Machinery Factory, and the tube sealing machine is OKFKJ3000 from Hunan Walker Energy Technology Co., Ltd.

[0035] Example 1 (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 95 Preparation of Mn5 Multi-Primary Element Cryogenic Alloy Materials

[0036] The preparation method of the Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy material of the present invention includes the following steps:

[0037] (1) The composition by nominal atomic percentage is (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 95 Mn5 is used as the raw material, with Ni, Co, Cr, Mo and Mn metallic elements selected as raw materials, and the purity of the raw materials is 99.99%. To compensate for the volatilization loss of Mn element during the smelting process, an additional 10 wt.% Mn is added relative to the nominal Mn addition.

[0038] (2) Place the above raw materials in a vacuum arc melting furnace for melting. Before melting, evacuate the furnace cavity to 10°C. -3 The pressure was then increased to -0.02 MPa by argon gas; this vacuuming and argon purging process was repeated three times. Subsequently, arc melting was performed under an argon protective atmosphere, with the melting current controlled below 450 A. To ensure uniform distribution of elements, arc melting was repeated at least five times, with the alloy ingot being flipped after each melting process. After melting, the molten alloy was vacuum-cast into a shape measuring 8×8×80 mm. 3 Bars.

[0039] (3) The cast rod-shaped material is sealed using a sealing machine. During the sealing process, hydrogen is generated by electrolyzing water using a hydrogen-oxygen generator. The hydrogen is then burned to melt the quartz tube and complete the sample encapsulation. The inside of the quartz tube is repeatedly purged during the sealing process, specifically by evacuating to 10°C. -3 The pressure was then increased to -0.02 MPa by Pa, and repeated three times. Then, argon gas was introduced to -0.09 MPa to maintain a vacuum environment inside the tube. The sealed sample was placed in a box-type heat treatment furnace for homogenization under the following conditions: 1200 ℃ for 24 h, with the temperature difference controlled within ±10℃. After homogenization, the sample was water-quenched.

[0040] (4) The homogenized sample is rolled at a mill speed of 300 r / min and a total rolling ratio of 80%. Each rolling adjustment is no more than 0.4 mm, and the rolling is repeated at least 5 times until the predetermined rolling ratio is reached.

[0041] (5) The rolled material is heat-treated at 1000℃ for 1 h to refine the grain structure and obtain a recrystallized alloy structure. Then, it is water-quenched to obtain Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy material.

[0042] Following the steps described above, a nominal atomic percentage composition of (Ni) was obtained. 28.2 Co 56.4 Cr 9.4 Mo6) 95 A Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy of Mn5 was obtained. Under tensile conditions at 77 K, the resulting alloy exhibited a yield strength of approximately 502 MPa, a tensile strength of approximately 1208 MPa, and a total elongation of approximately 107%. Microstructural analysis revealed that the ε-phase formed during cryogenic deformation primarily exhibited a fine, dispersed, non-penetrating lamellar or plate-like structure, which is beneficial for reducing local strain concentration and suppressing early cracking.

[0043] Example 2

[0044] The same preparation method as in Example 1 was used, except that the nominal atomic percentage composition of the alloy was adjusted to (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 90 Mn 10 An additional 10 wt.% of Mn was added during smelting to prepare the sample of Example 2. The resulting alloy, under tensile conditions at 77 K, exhibited a yield strength of approximately 493 MPa, a tensile strength of approximately 1190 MPa, and a total elongation of approximately 102%. Microstructural analysis showed that the alloy exhibited good overall low-temperature performance, and no obvious HCP phase was detected; plastic deformation was dominated by deformation twins.

[0045] Example 3

[0046] The same preparation method as in Example 1 was used, except that the nominal atomic percentage composition of the alloy was adjusted to (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 85 Mn 15An additional 10 wt.% of Mn was added during smelting to prepare the sample of Example 3. The resulting alloy, under tensile conditions at 77 K, exhibited a yield strength of approximately 490 MPa, a tensile strength of approximately 1147 MPa, and a total elongation of approximately 104%. Microstructural analysis showed that the alloy also possessed high ductility and good strength-ductility balance at low temperatures.

[0047] Comparative Example 1

[0048] The same preparation method as in Example 1 was used, except that the nominal atomic percentage composition of the alloy was adjusted to Ni. 28.2 Co 56.4 Cr 9.4 Mo6 was used to prepare the comparative example 1 sample. Under tensile conditions at 77 K, the resulting alloy exhibited a yield strength of approximately 518 MPa, a tensile strength of approximately 1003 MPa, and a total elongation of approximately 32%. During low-temperature deformation, this alloy readily forms a coarse, interconnected ε-phase lamellar network, which easily induces local strain concentration and early cracking.

[0049] Comparative Example 2

[0050] The same preparation method as in Example 1 was used, except that the nominal atomic percentage composition of the alloy was adjusted to (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 98 Mn2. An additional 10 wt.% of Mn was added during smelting to prepare Comparative Example 2. The resulting alloy, under tensile conditions at 77 K, exhibited a yield strength of approximately 510 MPa, a tensile strength of approximately 1215 MPa, and a total elongation of approximately 63%. Although this alloy possesses high tensile strength, its low-temperature plasticity is significantly lower than that of Examples 1-3, and it still exhibits noticeable ε-phase and interfacial strain concentration.

[0051] Comparative Example 3

[0052] The same preparation method as in Example 1 was used, except that the nominal atomic percentage composition of the alloy was adjusted to (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 80 Mn 20 During smelting, an additional 10 wt.% Mn was added to prepare Comparative Example 3. The resulting alloy, under tensile conditions at 77 K, exhibited a yield strength of approximately 488 MPa, a tensile strength of approximately 1052 MPa, and a total elongation of approximately 82%. Compared to Examples 1-3, while this alloy still maintains a certain degree of ductility, its overall strength-ductility synergistic performance has declined.

[0053] Synchrotron X-ray diffraction was used to test the annealed phase structure of the Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloys prepared in Examples 1-3 and Comparative Examples 1-3. The results are as follows: Figure 1 As shown, all annealed samples exhibited a single-phase face-centered cubic (FCC) structure, with no obvious second phase detected, indicating that the prepared alloy has good microstructural stability.

[0054] The tensile properties of the alloys obtained in Examples 1-3 and Comparative Examples 1-3 were tested at 77 K using a universal tensile testing machine. The engineering stress-strain curves are shown below. Figure 2 As shown in Table 1, the results indicate that the Mn5, Mn10, and Mn15 alloys corresponding to Examples 1-3 all exhibited high ductility and good strength-ductility matching at 77 K, with total elongations of approximately 107%, 102%, and 104%, respectively. In contrast, the total elongation of the Mn0 alloy in Comparative Example 1 was only about 32%, the total elongation of the Mn2 alloy in Comparative Example 2 was about 63%, and the total elongation of the Mn20 alloy in Comparative Example 3 was about 82%. These results demonstrate that controlling the Mn content within the range of 5 at.% to 15 at.% is beneficial for obtaining better low-temperature comprehensive mechanical properties, especially with an Mn content of 5 at.%, where the tensile strength is significantly higher than that at other atomic percentages.

[0055] Table 1

[0056]

[0057] Fracture morphology analysis was performed on the sample after tensile fracture at 77 K, and the results are as follows: Figure 3 As shown, Mn0 and Mn2 alloys exhibit mixed fracture characteristics, with both dimples and cleavage regions present in the fracture surface, indicating that they are more prone to local damage accumulation and early cracking during low-temperature deformation. In contrast, the fracture surfaces of Mn5, Mn10, Mn15, and Mn20 alloys mainly show dimple-type transgranular fracture characteristics, indicating that they underwent sufficient plastic deformation before fracture under low-temperature conditions.

[0058] Synchrotron X-ray diffraction was used to further analyze the phase of the sample after tensile fracture at 77 K, and the results are as follows: Figure 4 As shown, after fracture, the Mn0 alloy exhibited obvious HCP phase diffraction peaks, the Mn2 alloy still showed relatively obvious HCP phase diffraction peaks, the HCP phase diffraction peaks of the Mn5 alloy were further weakened, while no obvious HCP phase diffraction peaks were detected in the Mn10, Mn15, and Mn20 alloys. This result indicates that as the Mn content increases, the driving force of the γ→ε transformation gradually weakens; when the Mn content is controlled within the range of 5 at.% to 15 at.%, the evolution of the low-temperature deformation microstructure is more conducive to obtaining higher ductility and better low-temperature damage tolerance.

[0059] Further EBSD phase distribution analysis was performed on the fractured samples of Examples 1-3 and Comparative Examples 1-3, and the results are as follows: Figure 5 As shown, the ε phase in Mn0 alloys exhibits a coarse, interconnected lamellar network structure that spans grain boundaries, while the ε phase morphology in Mn2 alloys is intermediate. The ε phase in Mn5 alloys mainly presents as a fine, dispersed, non-penetrating lamellar structure, primarily confined within the grains. Mn10, Mn15, and Mn20 alloys essentially maintain a fully γ-phase microstructure. These results indicate that the introduction of Mn significantly affects the formation, content, and distribution of the ε phase during low-temperature deformation, and effectively suppresses the formation of coarse, interconnected ε phase networks within the range of 5 at.% to 15 at.%.

[0060] Combination Figure 2 The tensile properties shown Figure 3 The fracture morphology shown Figure 4 Post-fracture phase analysis and Figure 5 The EBSD microstructure characterization results show that when the Mn content is controlled within the range of 5 at.% to 15 at.%, the alloy maintains high tensile strength and achieves high elongation at 77K, exhibiting good overall low-temperature performance. The results indicate that the introduction of an appropriate amount of Mn is beneficial for controlling the formation, content, and distribution of the ε phase during low-temperature deformation, inhibiting the formation of coarse, interconnected ε phase networks, and thus improving the low-temperature damage tolerance of the material.

Claims

1. A Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material, characterized in that, The atomic percentage composition of the Ni-Co-Cr-Mo-Mn multi-principal element cryogenic alloy material is as follows: (Ni 28.2 Co 56.4 Cr 9.4 Mo6) 100-x Mn x , where 5≤x≤15.

2. The Ni-Co-Cr-Mo-Mn multi-principal-element cryogenic alloy material according to claim 1, characterized in that, The value of x is 5 or 10.

3. The preparation method of a Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy material according to claim 1 or 2, characterized in that, Includes the following steps: Step S1: Composition by atomic percentage (Ni) 28.2 Co 56.4 Cr 9.4 Mo6) 100-x Mn x Weigh the raw materials in the proportions specified for Ni, Co, Cr, Mo and Mn, where 5 ≤ x ≤ 15. Step S2: The weighed Ni, Co, Cr, Mo and Mn metal elements are subjected to electric arc melting under an inert protective atmosphere, and the ingot is repeatedly turned and remelted at least 5 times to obtain a cast ingot with uniform composition. Step S3: The material after suction casting is then sealed in a vacuum environment for high-temperature homogenization to eliminate component segregation, followed by water quenching. Step S4: Roll the homogenized material; Step S5: The rolled material is heat-treated and then water-quenched to refine the grain structure, thereby preparing Ni-Co-Cr-Mo-Mn multi-principal-element low-temperature alloy material.

4. The preparation method according to claim 3, characterized in that, The purity of the Ni, Co, Cr, Mo and Mn metallic elements mentioned in step S1 is greater than or equal to 99.99%.

5. The preparation method according to claim 3, characterized in that, In step S2, the amount of Mn added is increased by an additional 10 wt.%.

6. The preparation method according to claim 3, characterized in that, In step S2, the furnace cavity is evacuated to 10°C before melting. -3 Pa, then argon gas is introduced to a pressure of -0.02 MPa; the arc melting current is ≤450 A.

7. The preparation method according to claim 3, characterized in that, In step S3, the high-temperature homogenization treatment conditions are 1200℃ for 24 hours.

8. The preparation method according to claim 3, characterized in that, The specific steps in step S3 are as follows: After suction casting, the sample is sealed using a sealing machine; hydrogen is generated by electrolyzing water using a hydrogen-oxygen generator; the quartz tube is melted by burning the hydrogen to encapsulate the rod-shaped material; the inside of the tube is repeatedly purged; during purging, a vacuum of 10 is drawn. -3 The tube was treated with Pa, then purged with argon to a pressure of -0.02 MPa, and repeated three times. After that, the tube was purged with argon to a pressure of -0.09 MPa, and the vacuum inside the tube was maintained. A box-type heat treatment furnace was used, and the homogenization heat treatment conditions were 1200℃ for 24 h, with a temperature difference of ±10℃ inside the furnace.

9. The preparation method according to claim 3, characterized in that, In step S4, the mill speed is 300 r / min, and the rolling ratio is 80%-85%.

10. The preparation method according to claim 3, characterized in that, The heat treatment temperature in step S4 is 1000 ℃, and the heat treatment time is 1 hour.

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