A superplastic heterogeneous duplex stainless steel and its preparation method

Abstract

This invention provides a superplastic heterogeneous duplex stainless steel and its preparation method, comprising: (1) supersaturated solution treatment: placing the duplex stainless steel in a furnace at 1250-1350°C and holding it at that temperature for 10-60 minutes, then removing it and quenching it in oil; (2) heavy cold rolling and duplex annealing treatment: using a cold rolling mill to roll the duplex stainless steel in multiple passes at room temperature, with a rolling reduction of 70%-90%, then annealing it at 1000-1200°C for 10-30 minutes, air cooling, and then repeating the cold rolling of the duplex stainless steel, with a rolling reduction of 70%-90%; then annealing it again at 1000-1200°C for 10-30 minutes, and air cooling to obtain a heterogeneous duplex stainless steel with a "double peak" distribution of both phase size and grain size, which has excellent superplasticity. The superplastic heterogeneous duplex stainless steel prepared by this invention has a fracture elongation of ≥900%.

Description

Technical Field

[0001] This invention relates to the field of materials technology, specifically to a superplastic heterogeneous duplex stainless steel and its preparation method. Background Technology

[0002] Superplasticity refers to the excellent ductility and plasticity of metallic materials under specific conditions, with elongation exceeding 300% without defects such as necking or fracture. In contrast, the elongation of ordinary steel materials at room temperature is only 30%–60%. Superplastic materials are suitable for manufacturing parts with complex shapes requiring large deformations, offering advantages such as reduced manufacturing costs, simplified processing, and elimination of defects during machining. Currently, superplastic materials are widely used in many industrial production fields.

[0003] Heterogeneous metallic materials are a new type of metallic material composed of heterogeneous regions with significantly different mechanical or physical properties. The interactions and coupling effects between these heterogeneous regions enable the overall performance of the material to exceed the levels predicted by the mixing rule, thus giving heterogeneous metallic materials excellent mechanical or physical properties that far surpass those of traditional metallic materials, demonstrating enormous application potential in the field of structural materials.

[0004] Duplex stainless steel is a material composed of ferritic and austenitic phases, typically with each phase comprising approximately 50%. This steel combines the characteristics of both austenitic and ferritic stainless steels, exhibiting high plasticity and toughness. Duplex stainless steel also shows significant improvements in intergranular corrosion resistance and weldability, while retaining the 475℃ brittleness and high thermal conductivity of ferritic stainless steel. Compared to austenitic stainless steel, duplex stainless steel has higher strength and significantly improved resistance to intergranular corrosion and chloride stress corrosion. Duplex stainless steel itself possesses superplasticity, meaning that certain materials can exhibit very high ductility and deformation capacity under high-temperature conditions, achieving extremely large plastic deformation without necking. The application demand for duplex stainless steel in the construction and petrochemical industries is increasing; however, the formation of these steels is extremely difficult due to their poor plasticity at room temperature. Therefore, superplastic forming has profound application prospects and offers significant cost savings in manufacturing. Summary of the Invention

[0005] To address the aforementioned technical problems, a superplastic heterogeneous duplex stainless steel and its preparation method are provided.

[0006] The technical means employed in this invention are as follows:

[0007] A method for preparing superplastic heterogeneous duplex stainless steel, comprising:

[0008] (1) Supersaturated solution treatment:

[0009] The duplex stainless steel is placed in a furnace at 1250–1350°C and held at that temperature for 10–60 minutes, then removed and oil-quenched. In the microstructure of the duplex stainless steel after saturated solution treatment, the proportion of ferrite phase is 80%–90%, and the proportion of residual undissolved austenite phase is 10%–20%.

[0010] The chemical composition and mass percentage of the duplex stainless steel are as follows: C: 0.04-0.05%; N: 0.2-0.25%; Cr: 20-22%; Mn: 2.9-3.5%; Cu: 1.8-2.1%; Mo: 0.3-0.7%; Ni: 0.9-1.4%; Si: 0.8-1.2%; with the balance being Fe and unavoidable trace elements.

[0011] (2) Heavy cold rolling and two-phase annealing treatment:

[0012] Duplex stainless steel is rolled in multiple passes at room temperature using a cold rolling mill with a rolling reduction of 70%–90%. It is then annealed at 1000–1200℃ for 10–30 minutes, air-cooled, and then cold-rolled again with a rolling reduction of 70%–90%. Finally, it is annealed again at 1000–1200℃ for 10–30 minutes and air-cooled to obtain superplastic heterogeneous duplex stainless steel.

[0013] The austenite phase in the superplastic heterogeneous duplex stainless steel exhibits a heterogeneous and inhomogeneous structure, while the ferrite phase exhibits a homogeneous structure, with an austenite-ferrite ratio close to 1:1. The ferrite has uniform grain size and phase size, with a grain size of 10–15 μm. The austenite, however, exhibits a bimodal distribution in both grain size and phase size. The austenite grain size is divided into fine austenite and coarse austenite, with the fine austenite having an average size of 10.5 μm and the coarse austenite having an average size of 83 μm. The austenite grain size is also divided into fine grain size and coarse grain size, with fine grains ranging from 2–8 μm and coarse grains from 15–25 μm. The volume fraction of fine austenite and fine-grained austenite accounts for 60%–70% of the total austenite volume fraction, while the volume fraction of coarse austenite and coarse-grained austenite accounts for 30%–40%.

[0014] Isothermal superplastic deformation test on superplastic heterogeneous duplex stainless steel:

[0015] Superplastic heterogeneous duplex stainless steel was subjected to isothermal tensile testing at 900℃ with a strain rate of 0.001 s⁻¹. -1 The fracture elongation of superplastic heterogeneous duplex stainless steel was ≥900%, and water cooling was used to preserve the superplastic structure after deformation.

[0016] The present invention also provides a superplastic heterogeneous duplex stainless steel, which is prepared by the above-described preparation method.

[0017] The introduction of elements into duplex stainless steel has a positive impact on superplastic materials:

[0018] ① Annealing strengthening effect: Fe, N, and C elements can increase the strength and hardness of materials through the annealing strengthening mechanism, thereby improving the high-temperature resistance of materials. This can prevent local plastic failure and fracture during superplastic deformation.

[0019] ② Grain boundary properties: Appropriate amounts of Cu, Cr, Mo, and Ni elements can improve grain boundary properties, such as grain boundary energy and grain boundary migration rate. This helps to improve the stability and plasticity of grain boundaries, thereby promoting superplastic deformation of the material.

[0020] ③ Phase control: The addition of Mo and Mn elements can change the phase composition and phase distribution of the material, thereby adjusting the grain size and morphology. Appropriate grain refinement and uniform distribution help improve the plasticity and ductility of the material.

[0021] ④ Dynamic recrystallization: The presence of Fe may be beneficial to the dynamic recrystallization process of superplastic materials. Dynamic recrystallization can improve the plasticity of materials by eliminating stress accumulation and refining grains, thereby promoting superplastic deformation of the materials.

[0022] Duplex stainless steel is characterized by superplasticity. Superplasticity refers to the ability of certain materials to exhibit very high ductility and deformation capacity under high temperature conditions, enabling them to achieve large plastic deformation without necking.

[0023] After the above preparation process, a heterogeneous structure was obtained. A heterogeneous structure refers to a composite material composed of two or more materials with different properties, whose microstructure and properties differ at the microscale. The microstructural characteristics of heterogeneous materials can significantly affect superplasticity, as reflected in:

[0024] ① Interphase interfaces: Interphase interfaces in heterogeneous materials can provide dislocation stacking that hinders dislocation slip, thereby increasing the material's ductility. These interfaces can increase interactions between crystals, impede dislocation propagation, and thus promote plastic deformation of the material.

[0025] ② Phase size and distribution: The size and distribution of different phases in heterogeneous materials play an important role in superplastic properties. Smaller phase sizes and more uniformly distributed phases can provide more dislocation stacking and interfaces, thereby increasing the ductility of the material.

[0026] ③ Dislocation slip: Different phases in heterogeneous materials may have different crystal structures and dislocation densities, which affects the dislocation slip behavior. Some phases have lower dislocation slip stress, making the material more susceptible to plastic deformation.

[0027] In summary, this further enhances the mechanical and physical properties of the material. Furthermore, after isothermal superplastic deformation testing, it was found that its elongation at break is significantly increased, even reaching over 900%.

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

[0029] This method enables the preparation of superplastic heterogeneous duplex stainless steel. Through supersaturated solution treatment, the microstructure of the duplex stainless steel comprises 80-90% ferrite and 10-20% austenite, thus preventing phase transformation during cold rolling. This allows for multi-pass, heavy cold rolling deformation, providing sufficient nucleation sites for austenite precipitates in the subsequent duplex annealing process. Simultaneously, the abundant austenite precipitation hinders ferrite coarsening, resulting in uniform and refined ferrite grains. The duplex stainless steel treated with supersaturated solution treatment and heavy cold rolling annealing exhibits a fine microstructure with an austenite-to-ferrite ratio approaching 1:1.

[0030] The resulting superplastic heterogeneous duplex stainless steel possesses two grain-mixed phases within a specific range. The interaction between these two grain-mixed phases produces a synergistic effect, enabling the material's overall properties to exceed the predictions of the mixing rules, exhibiting superior mechanical and physical properties far surpassing those of traditional homogeneous materials. This method has strong process applicability, requires no additional equipment, and can be mass-produced on conventional cold rolling and annealing lines.

[0031] Based on the above reasons, this invention can be widely applied in fields such as superplastic heterogeneous duplex stainless steel. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart illustrating a method for preparing superplastic heterogeneous duplex stainless steel according to a specific embodiment of the present invention.

[0034] Figure 2The images show the microstructure of the duplex stainless steel that underwent heavy cold rolling and duplex annealing in Example 1 of this invention, where a) is a characteristic image of coarse and fine austenite grains, and b) is a characteristic image of coarse and fine austenite phases.

[0035] Figure 3 This is a diagram showing the bimodal grain size distribution of austenite in Example 1 of the present invention.

[0036] Figure 4 This is a size distribution diagram of the austenite bimodal crystal phase in Embodiment 1 of the present invention.

[0037] Figure 5 This is a diagram showing the ferrite grain size distribution in Example 1 of the present invention.

[0038] Figure 6 This is a ferrite crystal phase size distribution diagram in Embodiment 1 of the present invention.

[0039] Figure 7 This is an engineering stress-strain curve diagram during the isothermal superplastic deformation process in Embodiment 1 of the present invention.

[0040] Figure 8 This is a microstructure diagram of duplex stainless steel after heavy cold rolling and duplex annealing treatment in Comparative Example 1 of the present invention.

[0041] Figure 9 This is a stress-strain curve diagram of the isothermal superplastic deformation process in Comparative Example 1 of the present invention.

[0042] Figure 10 This is a microstructure diagram of duplex stainless steel after heavy cold rolling and duplex annealing treatment in Comparative Example 2 of the present invention.

[0043] Figure 11 This is a stress-strain curve diagram of the isothermal superplastic deformation process in Comparative Example 2 of the present invention.

[0044] Figure 12 The image shows the microstructure of duplex stainless steel after heavy cold rolling and duplex annealing treatment, as shown in Comparative Example 3 of this invention.

[0045] Figure 13 This is a stress-strain curve diagram of the isothermal superplastic deformation process in Comparative Example 3 of the present invention. Detailed Implementation

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] A method for preparing superplastic heterogeneous duplex stainless steel, the flowchart of which is shown below. Figure 1 As shown, it includes:

[0050] (1) Supersaturated solution treatment: After heating the furnace to 1300℃ at a heating rate of ≥15℃ / min, the duplex stainless steel was placed in the furnace and held at 1300℃ for 30 minutes, and then removed for oil quenching. The chemical composition (wt.%) of the duplex stainless steel is: C: 0.046%; N: 0.242%; Cr: 21.2%; Mn: 3.15%; Cu: 1.94%; Mo: 0.52%; Ni: 1.17%; Si: 0.92%; the balance is Fe and unavoidable trace elements. After supersaturated solution treatment, the proportion of ferrite phase in the microstructure reaches 85%, and the proportion of austenite phase reaches 15%. Some undissolved austenite phase exhibits a "short rod" morphology after strong deformation and annealing treatment. The remaining austenite mainly precipitates on the ferrite triple grain boundaries and gradually grows to form austenite phase with independent grains of a certain size.

[0051] (2) Heavy cold rolling and duplex annealing: The plate material after supersaturated solution treatment is subjected to multiple cold rolling passes at room temperature using a two-roll mill, with the rolling reduction controlled at 85%. After completion, the duplex stainless steel is heated to 1100℃ and held for 15 minutes for annealing and air cooling. Then, the duplex stainless steel is repeatedly rolled, with the rolling reduction controlled at 85%. After completion, the duplex stainless steel is heated to 1100℃ and held for 15 minutes for annealing and air cooling to obtain superplastic heterogeneous duplex stainless steel.

[0052] After undergoing heavy cold rolling and duplex annealing, duplex stainless steel exhibits a two-phase microstructure consisting of austenite and ferrite phases in approximately a 1:1 ratio. At this stage, coarse austenite comprises 35% and fine austenite 65%. Furthermore, the austenite grain size displays a bimodal heterogeneous distribution. The EBSD image of the duplex stainless steel obtained after these two steps is shown below. Figure 2As shown in the figure, figure a) illustrates the characteristics of coarse and fine austenite grains, and figure b) illustrates the characteristics of coarse and fine austenite phases. The size diagram of the bimodal grain structure of austenite is shown below. Figure 3 As shown, the average grain size of fine austenite is 3.5 μm, and the average grain size of coarse austenite is 21 μm. Its bimodal phase size diagram is shown below. Figure 4 As shown, the average crystal size of the fine austenite phase is 10.5 μm, and the average crystal size of the coarse austenite phase is 83 μm. The ferrite grain size diagram is shown below. Figure 5 As shown, the average grain size of ferrite is 13 μm. The ferrite crystal size distribution diagram is shown below. Figure 6 As shown, the average size of the ferrite crystal phase is 38 μm.

[0053] Isothermal superplastic deformation test: The superplastic heterogeneous duplex stainless steel was rapidly heated to 900℃. To ensure uniform temperature distribution, the superplastic heterogeneous duplex stainless steel was held at 900℃ for 1 minute before testing. Then, the superplastic heterogeneous duplex stainless steel obtained in Example 1 was subjected to isothermal tensile testing at a strain rate of 0.001 s⁻¹. -1 The elongation at break of superplastic heterogeneous duplex stainless steel is approximately 942.6%, such as... Figure 7 As shown, after deformation, water cooling is used to preserve the superplastic structure.

[0054] Comparative Example 1

[0055] Different rolling parameters are used.

[0056] (1) Supersaturated solution treatment: The furnace was heated to 1300℃ at a heating rate of ≥15℃ / min. The duplex stainless steel was then placed in the furnace and held at 1300℃ for 30 min, and then removed for oil quenching. The chemical composition (wt.%) of the duplex stainless steel was: C: 0.041%; N: 0.23%; Cr: 20.7%; Mn: 3.15%; Cu: 1.84%; Mo: 0.42%; Ni: 1.37%; Si: 1.12%; with the balance being Fe and unavoidable trace elements. After supersaturated solution treatment, the proportion of ferrite phase in the microstructure reached 65%, and the proportion of austenite phase in the microstructure reached 35%. Some undissolved austenite phases exhibited a "short rod" morphology after strong deformation and annealing treatment. The remaining austenite mainly precipitated on the ferrite triple grain boundaries and gradually grew to form austenite phases with independent grains of a certain size.

[0057] (2) Heavy cold rolling and duplex annealing: The supersaturated solution-treated sheet was rolled multiple times at room temperature on a cold rolling mill, with a total deformation of 60%. Then, the duplex stainless steel was annealed at 1100°C for 15 minutes, followed by air cooling and then rolled again with a reduction of 60%. The duplex stainless steel was then annealed at 1100°C for 15 minutes. After heavy cold rolling and duplex annealing, the duplex stainless steel obtained a two-phase microstructure of austenite and ferrite, with a phase ratio close to 1:1. The microstructure of the duplex stainless steel is shown in the image below. Figure 8 As shown. However, at this time, the austenite phase is uniformly distributed, does not exhibit isomerism, and there is no obvious difference between the coarse and fine phases.

[0058] Isothermal superplastic deformation test: The duplex stainless steel obtained after the first two steps was rapidly heated to 900℃. To ensure uniform temperature distribution, the sample was held at 900℃ for 1 minute before testing. Then, comparative example 1 was subjected to isothermal tensile testing at a strain rate of 0.001 s⁻¹. -1 The sample's elongation at break was approximately 553.7%, such as Figure 9 As described above, after deformation, water cooling is used to preserve the superplastic structure.

[0059] Comparative Example 2

[0060] Different solid solution techniques are employed.

[0061] (1) Ordinary solution treatment: After heating the furnace to 900℃ at a heating rate of ≥15℃ / min, the duplex stainless steel is placed in the furnace and held for 80min before being removed and oil quenched. The chemical composition (wt.%) of the duplex stainless steel is as follows: C: 0.045%; N: 0.212%; Cr: 21.36%; Mn: 3.35%; Cu: 2.033%; Mo: 0.652%; Ni: 1.26%; Si: 0.852%; Fe balance. After ordinary solution treatment, the overall microstructure of the duplex stainless steel is uniform, with ferrite phase accounting for 60% and austenite phase accounting for 40%. Some undissolved austenite phases exhibit an "island" morphology after strong deformation and annealing. The remaining austenite mainly precipitates at the ferrite triple grain boundaries and gradually grows to form austenite phases with independent grains of a certain size.

[0062] (2) Heavy cold rolling and duplex annealing: The sheet material after ordinary solution treatment is rolled multiple times at room temperature using a two-roll mill, with a rolling reduction of 85%. After completion, the duplex stainless steel is heated to 1100℃ and held for 15 minutes for annealing. Then, the duplex stainless steel is subjected to repeated cold rolling with a rolling reduction of 85%, followed by holding at 1100℃ for 15 minutes for annealing and air cooling. The microstructure of the duplex stainless steel after heavy cold rolling and duplex annealing is shown in the figure below. Figure 10 As shown, a two-phase microstructure with a ferrite matrix and an austenite structure was obtained, with the ratio of austenite to ferrite phases close to 2:1. The ferrite phase is elongated and dark in color, with a uniform distribution in size and no significant difference in size.

[0063] Isothermal superplastic deformation test: The duplex stainless steel obtained after the first two steps was rapidly heated to 900℃. To ensure uniform temperature distribution, the sample was held at 900℃ for 1 minute before testing. Then, comparative example 2 was subjected to isothermal tensile testing at a strain rate of 0.001 s⁻¹. -1 The sample's elongation at break was approximately 469.4%, such as Figure 11 As shown. After deformation, water cooling was used to preserve the superplastic structure.

[0064] Comparative Example 3

[0065] Different duplex stainless steel compositions are used.

[0066] (1) Supersaturated solution treatment: After heating to 1300℃ in a furnace at a heating rate of ≥15℃ / min, the duplex stainless steel was placed in the furnace and held for 30min before being removed and oil quenched. The chemical composition (wt.%) of the duplex stainless steel was: C: 0.182%; N: 0.53%; Cr: 18.2%; Mn: 4.22%; Cu: 1.65%; Mo: 0.135%; Ni: 1.56%; Si: 1.46%; Fe balance. After supersaturated solution heat treatment, the ferrite phase accounted for 35% and the austenite phase accounted for 65% of the microstructure of the duplex stainless steel. Some of the undissolved austenite phase exhibited a "short rod" morphology after strong deformation and annealing treatment, while the remaining austenite mainly precipitated at the triple grain boundaries of ferrite and gradually grew to form austenite phases with independent grains of a certain size.

[0067] (2) Heavy cold rolling and duplex annealing: The sheet material after supersaturated solution treatment is rolled multiple times at room temperature using a two-roll mill, with the rolling reduction controlled at 85%. Then, the duplex stainless steel is annealed at 1100℃ for 15 minutes, followed by repeated rolling with the rolling reduction controlled at 85%, and then annealed again at 1100℃ for 15 minutes and air-cooled. The scanning electron microscope (SEM) image of the duplex stainless steel after heavy cold rolling and duplex annealing is shown below. Figure 12 As shown, a two-phase microstructure of ferrite and austenite was obtained. The austenite phase appears as large, island-like structures, exhibiting a bright color, and still contains relatively large crystalline phases (grains). These large grains may affect the superplastic properties. The ferrite phase, on the other hand, shows a dark, banded distribution. The austenite phase is relatively uniformly distributed with no significant size variation.

[0068] (3) Isothermal superplastic deformation: The duplex stainless steel after the first two steps was heated to 900℃. To ensure uniform temperature distribution, the sample was held at 900℃ for 1 minute before testing. Then, comparative example 3 was subjected to isothermal tensile testing at a strain rate of 0.001s. -1 The sample's elongation at break was approximately 389.5%. Figure 13 As shown. After deformation, water cooling was used to preserve the superplastic structure.

[0069] As can be seen from Comparative Examples 1 to 3, under the same conditions, the elongation at break of the materials obtained by using rolling parameters not disclosed in this invention (Comparative Example 1), supersaturated solution treatment parameters not disclosed in this invention (Comparative Example 2), and duplex stainless steel composition not disclosed in this invention (Comparative Example 3) are far inferior to those of the present invention.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a superplastic heterogeneous duplex stainless steel, characterized by, Comprise: (1) supersaturated solid solution treatment: Put the duplex stainless steel into the furnace at 1250-1350℃, keep at this temperature for 10-60 minutes, take out and oil quench; the chemical composition of the duplex stainless steel and its mass percentage are: C: 0.04-0.05%; N: 0.2-0.25%; Cr: 20-22%; Mn: 2.9-3.5%; Cu: 1.8-2.1%; Mo: 0.3-0.7%; Ni: 0.9-1.4%; Si: 0.8-1.2%; the balance is Fe and inevitable trace elements; (2) heavy cold rolling and duplex phase annealing treatment: Use a cold rolling mill to roll the duplex stainless steel at room temperature in multiple passes, with a rolling reduction of 70%-90%, then anneal at 1000-1200℃ for 10-30 minutes, and then repeat the cold rolling of the duplex stainless steel, with a rolling reduction of 70%-90%; then anneal again at 1000-1200℃ for 10-30 minutes, and then air cool to obtain a superplastic heterogeneous duplex stainless steel; The austenite phase in the superplastic heterogeneous duplex stainless steel exhibits a heterogeneous non-uniform structure, the ferrite phase exhibits a uniform structure, and the ratio of the austenite phase to the ferrite phase is 1:1, wherein the crystal phase size and grain size of the ferrite are uniform, and the crystal phase size and grain size of the austenite are both "bimodal" distribution; The crystal phase size of the austenite in the superplastic heterogeneous duplex stainless steel is divided into fine austenite phase and coarse austenite phase; the average size of the fine austenite phase is 10.5µm, and the average size of the coarse austenite phase is 83µm; The grain size of the austenite is divided into fine grain size and coarse grain size; The fine grain size is 2-8µm; the coarse grain size is 15-25µm The volume fraction of the fine phase and fine grain size of the austenite accounts for 60%-70% of the total volume fraction of the austenite; The volume fraction of the coarse austenite phase and coarse grain size of the austenite accounts for 30%-40% of the total volume fraction of the austenite.

2. The method of claim 1, wherein the superplastic heterogeneous duplex stainless steel is prepared by the steps of: preparing a mixture of a first stainless steel powder and a second stainless steel powder; and sintering the mixture to form the superplastic heterogeneous duplex stainless steel. After step (1) treatment, the proportion of the ferrite phase in the duplex stainless steel is 80%-90%, and the proportion of the residual undissolved austenite phase is 10%-20%.

3. The method for preparing a superplastic heterogeneous duplex stainless steel according to claim 1, characterized in that, The superplastic isomeric duplex stainless steel is subjected to isothermal superplastic deformation test, and the superplastic isomeric duplex stainless steel is subjected to isothermal stretching at 900 DEG C with a strain rate of 0.001 s -1 , and the fracture elongation of the superplastic isomeric duplex stainless steel is greater than or equal to 900%.

4. A superplastic isomorphous duplex stainless steel, characterized by It is prepared by the preparation method of any one of claims 1-3.

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