Fe-ni-co-cr-v-nb-c-n multi-component cast iron alloy and preparation method thereof

Abstract

This invention discloses a Fe-Ni-Co-Cr-V-Nb-C-N multi-component Invar alloy and its preparation method. The alloy exhibits stable low expansion characteristics under different heat treatment conditions. In atomic percentage, the alloy is composed of the following chemical components: Fe 53-57%, Ni 21-24%, Co 15-17%, Cr 4-6%, V 0.1-1.0%, Nb 0.05-0.3%, C 0.4-1.0%, and N 0.05-0.3%. This invention yields a series of Fe-Ni-Co-Cr-V-Nb-C-N Invar multi-component alloys with significantly improved strength, solving the problem of low strength in traditional Invar alloys and further expanding the application range of Invar alloys in load-bearing environments.

Description

Technical Field

[0001] This invention belongs to the field of metal material preparation technology, specifically involving a Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy and its preparation method. Background Technology

[0002] Invar alloys, due to their extremely low thermal expansion, have significant application value in precision instruments, temperature-sensitive components, and related structural parts. For their engineering applications, the material typically faces differentiated performance requirements at different stages: during forming and processing, good machinability and high plasticity are needed to meet the fabrication requirements of complex components; in the final service state, good comprehensive mechanical properties and reliability are required. However, existing Invar alloy systems still have shortcomings in the synergistic control of performance, especially when the microstructure changes, it is often difficult to simultaneously maintain a low coefficient of thermal expansion. At the same time, commonly used alloying strengthening or microstructure control methods can easily cause changes in magnetic state and phase structure, thereby weakening the Invar effect, making it difficult to simultaneously maintain low expansion stability in the processed, transition, and service states. Therefore, developing an Invar alloy that maintains low thermal expansion in different states while possessing good machinability, excellent strength and plasticity, and good comprehensive mechanical properties is of great significance for expanding its engineering applications. Summary of the Invention

[0003] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0004] In view of the problem of low room temperature strength of low expansion materials in the above and / or prior art, the present invention is proposed.

[0005] One objective of this invention is to provide a Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy, which introduces different contents of V, Nb, C, and N elements into the FeNiCoCr-based multi-principal alloy and uses appropriate thermomechanical processes to obtain microstructures in different heat treatment states (homogenized state / aged state). This ensures that the material composition and microstructure remain stable and have low expansion characteristics, while providing an excellent combination of alloy strength and plasticity.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy, wherein the alloy exhibits stable low expansion characteristics under different heat treatment states, and the alloy is composed of the following chemical components in atomic percentage: Fe 53-57%, Ni 21-24%, Co 15-17%, Cr 4-6%, V 0.1-1.0%, Nb 0.05-0.3%, C 0.4-1.0%, N 0.05-0.3%;

[0007] The total atomic percentage of Fe, Ni, Co, and Cr is 97-99%, and the total atomic percentage of V, Nb, C, and N is 1-3%. The ratio of the total atomic percentage of V and Nb to the total atomic percentage of C and N is 0.5-2. The total atomic percentage of all components of the alloy is 100%.

[0008] As a preferred embodiment of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, the alloy comprises, by atomic percentage, 54-56% Fe, 22-23% Ni, 15-16% Co, 5-6% Cr, 0.08-0.2% Nb, 0.5-0.9% V, 0.08-0.9% C, and 0.08-0.3% N.

[0009] As a preferred embodiment of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, the alloy has the following characteristics:

[0010] (a) The coefficient of thermal expansion is as low as 1.5 × 10⁻⁶ K before 378 K. -6 ~4.5×10 -6 K -1 ;

[0011] (b) The saturation magnetization at room temperature is 0.7~1.3 T;

[0012] (c) Coercivity at room temperature is 50~250 A / m;

[0013] (d) The Curie temperature is above 430 K;

[0014] (e) The tensile yield strength at room temperature is above 210 MPa, and the tensile strength is above 350 MPa;

[0015] (f) Tensile strain value at room temperature is greater than 30%.

[0016] Another object of the present invention is to provide a method for preparing the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described above, comprising: taking each component according to the atomic percentage of the alloy, first evacuating the vacuum, then injecting nitrogen as a protective atmosphere for melting, casting to obtain an alloy billet, and heat-treating the billet to obtain the alloy.

[0017] In a preferred embodiment of the preparation method of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, the nitrogen injection is carried out at 50 Pa as a protective atmosphere.

[0018] The melting process is carried out at a temperature greater than 1950 K, and the melt is held at that temperature for 3 to 5 minutes after melting.

[0019] As a preferred embodiment of the preparation method of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, the heat treatment includes first eliminating casting defects by hot rolling, high-temperature homogenization heat treatment, then introducing deformation by cold rolling, medium-high temperature annealing heat treatment, and then aging heat treatment at medium-low temperature.

[0020] As a preferred embodiment of the preparation method of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, the hot rolling is carried out in multiple passes at a temperature of 1300~1500 K, with a single pass reduction of ≤10% and a total reduction of 40~60%.

[0021] As a preferred embodiment of the preparation method of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, wherein: the high-temperature homogenization heat treatment is performed if the sum of the atomic percentages of V and Nb is 0.8~1.2% and the sum of the atomic percentages of C and N is 0.5~0.7%, the homogenization heat treatment temperature is 1590~1610 K and the holding time is more than 0.5 hours;

[0022] If the sum of the atomic percentages of V and Nb is 0.5-0.7%, and the sum of the atomic percentages of C and N is 0.5-0.7%, the homogenization heat treatment temperature is 1525-1555 K, and the holding time is more than 0.5 hours.

[0023] If the sum of the atomic percentages of V and Nb is 0.5-0.7%, and the sum of the atomic percentages of C and N is 0.8-1.2%, the homogenization heat treatment temperature is 1565-1585 K, and the holding time is more than 0.5 hours.

[0024] In a preferred embodiment of the preparation method of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, the high-temperature homogenization heat treatment involves loading the sample into a quartz glass tube and vacuum sealing it, with the vacuum degree inside the quartz tube being less than 2 Pa and the sample encapsulation weight being less than 0.8 g / cm³. 3 .

[0025] As a preferred embodiment of the preparation method of Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, wherein: the cold rolling adopts multi-pass cold rolling, the single-pass rolling reduction is ≤10%, and the total reduction is 50~95%.

[0026] In a preferred embodiment of the preparation method of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy of the present invention, the annealing is a first annealing or a second annealing; wherein the first annealing temperature is 1300~1380 K and the holding time is 5~15 minutes; the second annealing temperature is 1200~1280 K and the holding time is 5~15 minutes;

[0027] The aging temperature is 730~830 K, and the holding time is 24~48 hours.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention provides a series of Fe-Ni-Co-Cr-V-Nb-CN Invar multi-component alloys with significantly improved strength, solving the problem of low strength in traditional Invar alloys and further expanding the application range of Invar alloys in load-bearing environments. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0031] Figure 1 This is the XRD pattern of the alloy material in the homogenized state in Example 1 of the present invention.

[0032] Figure 2 These are scanning electron microscope (SEM) images of the homogenized state, fully recrystallized aged state, and partially recrystallized aged state of the alloy material in Example 1 of this invention.

[0033] Figure 3 This is a transmission electron microscope (TEM) image of the alloy material in the fully recrystallized aged state according to Example 1 of the present invention.

[0034] Figure 4 These are transmission electron microscopy (TEM) images and energy dispersive spectroscopy (EDS) distributions of the alloy material in the fully recrystallized aged state according to Example 1 of this invention.

[0035] Figure 5 This is a thermal expansion performance diagram of the alloy material in Example 1 of the present invention.

[0036] Figure 6 This is a hysteresis loop diagram of the alloy material in Embodiment 1 of the present invention.

[0037] Figure 7 This is a demagnetization curve of the alloy material in the homogenized state in Example 1 of the present invention.

[0038] Figure 8 This is a room temperature tensile stress-strain curve of the alloy material in Embodiment 1 of the present invention.

[0039] Figure 9 This is the XRD pattern of the alloy material in the homogenized state in Example 2 of the present invention.

[0040] Figure 10 These are scanning electron microscope (SEM) images of the homogenized state, fully recrystallized aged state, and partially recrystallized aged state of the alloy material in Example 2 of this invention.

[0041] Figure 11 This is a thermal expansion performance diagram of the alloy material in Example 2 of the present invention.

[0042] Figure 12 This is the hysteresis loop diagram of the alloy material in Embodiment 2 of the present invention.

[0043] Figure 13 This is a demagnetization curve of the alloy material in the homogenized state in Example 2 of the present invention.

[0044] Figure 14 This is a room temperature tensile stress-strain curve of the alloy material in Embodiment 2 of the present invention.

[0045] Figure 15 This is the XRD pattern of the alloy material in the homogenized state in Example 3 of the present invention.

[0046] Figure 16 These are scanning electron microscope (SEM) images of the homogenized state, fully recrystallized aged state, and partially recrystallized aged state of the alloy material in Example 3 of this invention.

[0047] Figure 17 This is a thermal expansion property diagram of the alloy material in Example 3 of the present invention.

[0048] Figure 18 This is the hysteresis loop diagram of the alloy material in Embodiment 3 of the present invention.

[0049] Figure 19This is a demagnetization curve of the alloy material in the homogenized state in Example 3 of the present invention.

[0050] Figure 20 This is a room temperature tensile stress-strain curve of the alloy material in Example 3 of the present invention.

[0051] Figure 21 These are ingot diagrams of the alloy materials of Comparative Example 1 and Example 1 of the present invention.

[0052] Figure 22 This is a scanning electron microscope (SEM) image of the alloy material in Comparative Example 2 of this invention.

[0053] Figure 23 These are diagrams showing the quartz tube bursting and the high-temperature furnace heating tube damage of the alloy material in Comparative Example 3 of this invention. Detailed Implementation

[0054] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0055] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0056] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0057] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0058] Example 1

[0059] (1) According to the chemical formula Fe 54.6 Ni 22.8 Co 15.6 Cr 5.4 V 0.8 Nb 0.2 C 0.5 N 0.1 The raw materials are prepared according to atomic percentages. Fe, Ni, Co, Cr, V, and Nb are prepared using their corresponding elemental bulk materials (purity ≥ 99.9%). N is introduced through CrN and nitrogen pressure, and C is introduced through high-purity graphite. After evacuating the vacuum induction melting furnace, nitrogen is introduced to 50 Pa. After melting and holding at that temperature for 3-5 minutes, the vacuum is broken and the ingot is cast.

[0060] (2) The obtained billet was hot-rolled at 1323 K with a reduction of 50%. Next, after high-temperature homogenization, the block was cut into appropriate sizes, then placed into a quartz glass tube and vacuum-sealed. The vacuum level inside the quartz tube was less than 2 Pa, and the sample sealing weight was 0.8 g / cm³. 3 (i.e., 1 cm) 3 (A 0.8 g sample was packaged). The packaged sample was heated in a furnace and then subjected to a homogenization heat treatment at 1593 K for 3 h to obtain the homogenized alloy of Example 1. It was then cold-rolled with a reduction of 70%. Subsequently, two recrystallization annealing regimes were used: one, holding at 1323 K for 10 min to obtain a partially recrystallized structure; the other, holding at 1223 K for 10 min to obtain a partially recrystallized structure. After recrystallization annealing, both groups of samples were aged under the same conditions, i.e., held at 773 K for 32 h, to obtain the corresponding aged alloy. All alloy samples were vacuum-sealed (pressure ≤ 2 Pa) before heat treatment, and all heat-treated samples were water-quenched.

[0061] Depend on Figures 1-2 As can be seen, the alloy matrix obtained in this embodiment has a face-centered cubic (FCC) structure. The fully recrystallized aged microstructure has fine and uniform grains, while the area fraction of the unrecrystallized region in the incompletely recrystallized aged microstructure is close to 50%. Taking the fully recrystallized aged microstructure as an example, Figure 3 This indicates that a large number of precipitates are dispersed in the microstructure, and these precipitates can effectively pin grain boundaries and promote fine-grain strengthening of the alloy. Figure 4 The HAADF and BF images and corresponding energy dispersive spectroscopy (EDS) images from transmission electron microscopy reveal that the nanoscale precipitates are complex carbonitrides enriched with V, Nb, C, and N.

[0062] Figure 5 This indicates that Example 1 with different tissue states exhibits a stable and significant low expansion effect near room temperature. From room temperature to 373 K, the coefficients of thermal expansion of the homogenized state, the fully recrystallized aged state, and the incompletely recrystallized aged state remain as low as 3.46 × 10⁻⁶. -6 2.72×10 -6 3.13×10 -6 K -1 . Figure 6 The results show that the saturation magnetization of the alloy in the homogenized state, the fully recrystallized aged state, and the incompletely recrystallized aged state at room temperature are 0.85, 0.94, and 0.91 T, respectively, and the coercivity is 59, 142, and 235 A / m, respectively. Figure 7 This indicates that the Curie temperature for the homogenized state test in Example 1 was 455 K.

[0063] Depend on Figure 8It can be seen that Example 1 exhibits differentiated performance characteristics under different states: the homogenized alloy has better plastic deformation capacity and is conducive to subsequent processing and forming, with a yield strength of 259.3 MPa, a tensile strength of 490.0 MPa, and an elongation after fracture of 49.5%. The fully recrystallized aged alloy, obtained by cold rolling and recrystallization annealing followed by the same aging treatment, has a yield strength of 370.1 MPa, a tensile strength of 640.8 MPa, and an elongation after fracture of 47.1%. The incompletely recrystallized aged alloy has a yield strength of 573.2 MPa, a tensile strength of 781.8 MPa, and an elongation after fracture of 30.5%. Compared with the homogenized state, the strength of both aged alloys is further improved.

[0064] Example 2

[0065] (1) According to the chemical formula Fe 55 Ni 22.8 Co 15.6 Cr 5.4 V 0.5 Nb 0.1 C 0.5 N 0.1 The raw materials are prepared according to atomic percentages. Fe, Ni, Co, Cr, V, and Nb are prepared using their corresponding elemental bulk materials (purity ≥ 99.9%). N is introduced through CrN and nitrogen pressure, and C is introduced through high-purity graphite. After evacuating the vacuum induction melting furnace, nitrogen is introduced to 50 Pa. After melting and holding at that temperature for 3-5 minutes, the vacuum is broken and the ingot is cast.

[0066] (2) The obtained billet was hot-rolled at 1323 K with a reduction of 50%. Next, after high-temperature homogenization, the block was cut into appropriate sizes, then placed into a quartz glass tube and vacuum-sealed. The vacuum level inside the quartz tube was less than 2 Pa, and the sample sealing weight was 0.8 g / cm³. 3 (i.e., 1 cm) 3 (A 0.8 g sample was packaged). The packaged sample was heated in a furnace and then subjected to a homogenization heat treatment at 1553 K for 3 h to obtain the homogenized alloy of Example 2. It was then cold-rolled with a reduction of 70%. Subsequently, two recrystallization annealing regimes were used: one, holding at 1323 K for 10 min to obtain a partially recrystallized structure; the other, holding at 1223 K for 10 min to obtain a partially recrystallized structure. After recrystallization annealing, both groups of samples were aged under the same conditions, i.e., held at 773 K for 32 h, to obtain the corresponding aged alloy. All alloy samples were vacuum-sealed (pressure ≤ 2 Pa) before heat treatment, and all heat-treated samples were water-quenched.

[0067] Depend on Figures 9-10As can be seen, the alloy matrix obtained in this embodiment has a face-centered cubic (FCC) structure. The fully recrystallized aged microstructure has fine and uniform grains, while the area fraction of the unrecrystallized region in the incompletely recrystallized aged microstructure is close to 40%. Furthermore, a large number of precipitates are dispersed in the annealed microstructure.

[0068] Figure 11 This indicates that Example 2, with different tissue states, exhibits a stable and significantly low expansion effect near room temperature. From room temperature to 373 K, the coefficients of thermal expansion for the homogenized state, the fully recrystallized aged state, and the incompletely recrystallized aged state remain as low as 3.37 × 10⁻⁶. -6 2.69×10 -6 2.94×10 -6 K -1 . Figure 12 The results show that the saturation magnetization of the alloy in the homogenized state, the fully recrystallized aged state, and the incompletely recrystallized aged state at room temperature are 0.92, 1.02, and 1.00 T, respectively, and the coercivity is 63, 132, and 175 A / m, respectively. Figure 13 This indicates that the Curie temperature for the homogenized state test in Example 2 was 454 K.

[0069] Depend on Figure 14 It can be seen that Example 2 exhibits differentiated performance characteristics under different states: the homogenized alloy has better plastic deformation capacity and is conducive to subsequent processing and forming, with a yield strength of 213.4 MPa, a tensile strength of 356.3 MPa, and an elongation after fracture of 52.3%. The fully recrystallized aged alloy, obtained by cold rolling and recrystallization annealing followed by the same aging treatment, has a yield strength of 395.2 MPa, a tensile strength of 670.1 MPa, and an elongation after fracture of 48.0%. The incompletely recrystallized aged alloy has a yield strength of 504.7 MPa, a tensile strength of 731.0 MPa, and an elongation after fracture of 39.2%.

[0070] Example 3

[0071] (1) According to the chemical formula Fe 54.6 Ni 22.8 Co 15.6 Cr 5.4 V 0.5 Nb 0.1 C 0.8 N 0.2 The raw materials are prepared according to atomic percentages. Fe, Ni, Co, Cr, V, and Nb are prepared using their corresponding elemental bulk materials (purity ≥ 99.9%). N is introduced through CrN and nitrogen pressure, and C is introduced through high-purity graphite. After evacuating the vacuum induction melting furnace, nitrogen is introduced to 50 Pa. After melting and holding at that temperature for 3-5 minutes, the vacuum is broken and the ingot is cast.

[0072] (2) The obtained billet was hot-rolled at 1323 K with a reduction of 50%. Next, after high-temperature homogenization, the block was cut into appropriate sizes, then placed into a quartz glass tube and vacuum-sealed. The vacuum level inside the quartz tube was less than 2 Pa, and the sample sealing weight was 0.8 g / cm³. 3 (i.e., 1 cm) 3 (A 0.8 g sample was packaged). The packaged sample was heated in a furnace and then subjected to a homogenization heat treatment at 1573 K for 3 h to obtain the homogenized alloy of Example 3. It was then cold-rolled with a reduction of 70%. Subsequently, two recrystallization annealing regimes were used: one, holding at 1323 K for 10 min to obtain a partially recrystallized structure; the other, holding at 1223 K for 10 min to obtain a partially recrystallized structure. After recrystallization annealing, both groups of samples were aged under the same conditions, i.e., held at 773 K for 32 h, to obtain the corresponding aged alloy. All alloy samples were vacuum-sealed (pressure ≤ 2 Pa) before heat treatment, and all heat-treated samples were water-quenched.

[0073] Depend on Figures 15-16 As can be seen, the alloy matrix obtained in this embodiment has a face-centered cubic (FCC) structure. The fully recrystallized aged microstructure has fine and uniform grains, while the area fraction of the unrecrystallized region in the incompletely recrystallized aged microstructure is close to 30%. Furthermore, a large number of precipitates are dispersed in the annealed microstructure.

[0074] Figure 17 This indicates that Example 3, with different tissue states, exhibits a stable and significantly low expansion effect near room temperature. From room temperature to 373 K, the coefficients of thermal expansion for the homogenized state, the fully recrystallized aged state, and the incompletely recrystallized aged state remain as low as 3.20 × 10⁻⁶. -6 2.66×10 -6 3.05×10 -6 K -1 . Figure 18 The results show that the saturation magnetization of the alloy in the homogenized state, the fully recrystallized aged state, and the incompletely recrystallized aged state at room temperature are 0.93, 0.99, and 0.97 T, respectively, and the coercivity is 72, 122, and 156 A / m, respectively. Figure 19 This indicates that the Curie temperature of the homogenized state test in Example 3 was 471 K.

[0075] Depend on Figure 20It can be seen that Example 3 exhibits differentiated performance characteristics under different states: the homogenized alloy has better plastic deformation capacity and is conducive to subsequent processing and forming, with a yield strength of 243.4 MPa, a tensile strength of 469.7 MPa, and an elongation after fracture of 49.0%. The fully recrystallized aged alloy, obtained by cold rolling and recrystallization annealing followed by the same aging treatment, has a yield strength of 375.1 MPa, a tensile strength of 635.7 MPa, and an elongation after fracture of 46.0%. The incompletely recrystallized aged alloy has a yield strength of 496.6 MPa, a tensile strength of 695.4 MPa, and an elongation after fracture of 34.6%.

[0076] Comparative Example 1

[0077] Comparative Example 1, based on Example 1, extends the holding time after melting in step (1) to 10-15 minutes, while maintaining the same other smelting conditions as Example 1. A comparison of the ingot diagrams obtained in Comparative Example 1 and Example 1 is shown below. Figure 21 As shown.

[0078] As can be seen from the figure, compared with the dense ingot obtained under the control parameters of Example 1 ( Figure 21 Compared to c and d), when the holding time is extended to 10 to 15 minutes, the ingot obtained in Comparative Example 1 ( Figure 21 a) and b) can lead to instability in gas dissolution and precipitation behavior, resulting in supersaturated precipitation and the formation of a large number of bubbles inside the molten metal. However, within the parameter range defined in Example 1, by strictly controlling the melting temperature and atmosphere conditions, the violent gas precipitation can be effectively suppressed, the number of bubbles can be significantly reduced, and the density of the microstructure and the yield can be improved.

[0079] Comparative Example 2

[0080] According to the chemical formula Fe 55 Ni 22.8 Co 15.6 Cr 5.4 V 0.5 Nb 0.1 C 0.5 N 0.1 The raw materials are prepared according to atomic percentages. Fe, Ni, Co, Cr, V, and Nb are prepared using their corresponding elemental blocks (purity ≥ 99.9%). N is introduced through CrN and nitrogen pressure, and C is introduced through high-purity graphite. After the gas pressure in the vacuum induction melting furnace is evacuated, nitrogen is introduced to 50 Pa. After melting and holding at that temperature for 3-5 minutes, the vacuum is broken during casting to obtain the ingot.

[0081] The resulting ingot was hot-rolled at 1323 K with a reduction of 50%. It was then homogenized at 1573 K for 3 h to obtain the homogenized alloy of Comparative Example 2. Figure 22As can be seen, excessively high homogenization temperatures lead to the formation of numerous oxide inclusions, resulting in a decline in metal properties. Compared to the homogenization parameters in Example 2, the unoptimized melting process severely affects grain uniformity and reduces ingot quality. Meanwhile, holding at 1073 K for 4 hours yielded... Figure 22 In the aging alloy corresponding to Comparative Example 2 (b), when the aging temperature is too high, precipitates tend to accumulate along grain boundaries, leading to grain boundary embrittlement. Such precipitation behavior significantly reduces the mechanical properties of the material, especially tensile strength and ductility.

[0082] Comparative Example 3

[0083] This comparative example 3 is based on example 3, but the sample packaging amount in step (2) is adjusted to 0.9 g / cm3, and other heat treatment conditions are the same as in example 3.

[0084] like Figure 23 As shown, when the vacuum level inside the quartz tube is below 2 Pa, the critical value for the sample encapsulation weight after high-temperature heat treatment is 0.8 g / cm³. 3 (i.e., 1 cm) 3 (The volume weight of the sample is 0.8 g). Otherwise, if a vacuum quartz glass tube with a large package weight is directly placed into a 1573 K high-temperature furnace, the gas pressure inside the tube will rise rapidly, causing the quartz glass tube to burst. Figure 23 a). A ruptured quartz glass tube can also damage the heating element of a high-temperature furnace. Figure 23 (b) Increased equipment maintenance and usage costs.

[0085] The Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy series, by designing appropriate V, Nb, C, and N contents, samples with different properties were obtained under different heat treatment states. Excellent machinability was achieved in the homogenized state. After aging, the alloy exhibited high strength and good plasticity. When the (V+Nb) / (C+N) ratio was close to 1.6, V and Nb played a dominant role, reducing the diffusion coefficient and refining the grains. When the (V+Nb) / (C+N) ratio was close to 0.6, C and N played a dominant role, resulting in stronger basic solid solution strengthening. Furthermore, as the ratio decreased, after holding at 1223 K for 10 min, the proportion of the non-recrystallized region decreased from approximately 50% to approximately 30%. In addition, the alloy's low thermal expansion properties remained stable during changes in composition and microstructure. However, as shown in Example 1 and Comparative Example 1, if the parameters are not strictly controlled when adding C and N elements, it is easy to lead to a large number of pores in the ingot, resulting in melting failure. Further comparison of Example 2 and Comparative Example 2 revealed that inappropriate homogenization parameters led to a sharp increase in inclusions, while annealing at excessively high temperatures promoted the continuous precipitation of precipitates, significantly deteriorating alloy properties. This phenomenon indicates that precise control of process parameters is crucial for regulating alloy microstructure and obtaining excellent properties. Comparing Example 3 and Comparative Example 3, the sample encapsulation amount within the quartz glass tube during heat treatment had a significant impact on the sample preparation results. For material systems containing C and N elements, the sample loading size, vacuum encapsulation, and heating rate during operation should be strictly regulated to avoid compositional fluctuations and abnormal gas pressure leading to quartz glass tube rupture, equipment damage, and processing failure. The process window guidance provided by the patent offers key guidance for controlling the microalloying content of V, Nb, C, and N and the thermomechanical processes, effectively preventing the aforementioned problems and thus improving the overall performance of the alloy.

[0086] This invention designs a series of multi-component Invar alloys through V, Nb, C, and N microalloying. Different contents of V, Nb, C, and N are introduced into FeCoNiCr alloys, combined with different thermomechanical processes, to ensure the excellent performance of the alloys under various heat treatment states and maintain a significantly low thermal expansion effect, thereby improving the overall performance of the alloys. Furthermore, it can obtain FCC matrix alloys with precipitation strengthening and dislocation strengthening, promoting the research, application, and development of novel Invar alloys.

[0087] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy, characterized in that: The alloy exhibits stable low expansion characteristics under different heat treatment conditions. In atomic percentage, the alloy is composed of the following chemical components: Fe 53–57%, Ni 21–24%, Co 15–17%, Cr 4–6%, V 0.1–1.0%, Nb 0.05–0.3%, C 0.4–1.0%, N 0.05–0.3%. The total atomic percentage of Fe, Ni, Co, and Cr is 97-99%, and the total atomic percentage of V, Nb, C, and N is 1-3%. The ratio of the total atomic percentage of V and Nb to the total atomic percentage of C and N is 0.5-2. The total atomic percentage of all components of the alloy is 100%.

2. The Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in claim 1, characterized in that: It consists of Fe 54–56%, Ni 22–23%, Co 15–16%, Cr 5–6%, Nb 0.08–0.2%, V 0.5–0.9%, C 0.08–0.9%, and N 0.08–0.3% by atomic percentage.

3. The Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in claim 1 or 2, characterized in that: The alloy has the following properties: (a) The coefficient of thermal expansion is as low as 1.5 × 10⁻⁶ K before 378 K. -6 ~4.5×10 -6 K -1 ; (b) The saturation magnetization at room temperature is 0.7~1.3 T; (c) Coercivity at room temperature is 50~250 A / m; (d) The Curie temperature is above 430 K; (e) The tensile yield strength at room temperature is above 210 MPa, and the tensile strength is above 350 MPa; (f) Tensile strain value at room temperature is greater than 30%.

4. The method for preparing the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in any one of claims 1 to 3, characterized in that: The process includes preparing each component according to the atomic percentage of the alloy, first evacuating the vacuum, then injecting nitrogen as a protective atmosphere for melting, casting to obtain an alloy billet, and then heat-treating the billet to obtain the alloy.

5. The preparation method of the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in claim 4, characterized in that: The nitrogen gas is injected to a pressure of 50 Pa as a protective atmosphere. The melting process is carried out at a temperature greater than 1950 K, and the melt is held at that temperature for 3 to 5 minutes after melting.

6. The method for preparing the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in claim 4, characterized in that: The heat treatment includes first eliminating casting defects through hot rolling, then high-temperature homogenization heat treatment, followed by cold rolling to introduce deformation, medium-high temperature annealing heat treatment, and finally aging heat treatment at medium and low temperatures.

7. The method for preparing the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in claim 6, characterized in that: The hot rolling process employs multi-pass hot rolling at a temperature of 1300~1500 K, with a single-pass reduction of ≤10% and a total reduction of 40~60%.

8. The method for preparing the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in claim 6 or 7, characterized in that: The high-temperature homogenization heat treatment is performed when the sum of the atomic percentages of V and Nb is 0.8-1.2% and the sum of the atomic percentages of C and N is 0.5-0.7%, the homogenization heat treatment temperature is 1590-1610 K and the holding time is more than 0.5 hours. If the sum of the atomic percentages of V and Nb is 0.5-0.7%, and the sum of the atomic percentages of C and N is 0.5-0.7%, the homogenization heat treatment temperature is 1525-1555 K, and the holding time is more than 0.5 hours. If the sum of the atomic percentages of V and Nb is 0.5-0.7%, and the sum of the atomic percentages of C and N is 0.8-1.2%, the homogenization heat treatment temperature is 1565-1585 K, and the holding time is more than 0.5 hours.

9. The method for preparing the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in claim 8, characterized in that: The cold rolling process employs multi-pass cold rolling, with a single pass reduction of ≤10% and a total reduction of 50~95%.

10. The method for preparing the Fe-Ni-Co-Cr-V-Nb-CN multi-component Invar alloy as described in any one of claims 6, 7, and 9, characterized in that: The annealing is either a first annealing or a second annealing; wherein, the first annealing temperature is 1300~1380K and the holding time is 5~15 minutes; the second annealing temperature is 1200~1280K and the holding time is 5~15 minutes; The aging temperature is 730~830 K, and the holding time is 24~48 hours.

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