Preparation method of Fe-Mn-Al-Ni-C light steel alloy

Abstract

The invention relates to the technical field of laser additive manufacturing, in particular to a preparation method of a Fe-Mn-Al-Ni-C light steel alloy. The Fe-Mn-Al-Ni-C alloy powder is prepared through a vacuum induction melting gas atomization furnace, a tight coupling type nozzle and powder screening equipment according to the component proportion; alloy powder is preset on the surface of the base material; the method comprises the following steps: setting process parameters of laser additive manufacturing of the Fe-Mn-Al-Ni-C alloy, and carrying out layer-by-layer printing and stacking forming on the Fe-Mn-Al-Ni-C alloy; and the Fe-Mn-Al-Ni-C alloy subjected to laser additive manufacturing is subjected to heat treatment. According to the high-strength low-density steel and the preparation method thereof, the high-strength level that the yield strength is larger than or equal to 900 MPa and the ultimate tensile strength is larger than or equal to 1 GPa is achieved on the basis of low density of the material by matching precise component regulation and control with a subsequent heat treatment process, and the technical problem that density reduction and loss are high generally existing in light steel is solved.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, and more specifically, to a method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy. Background Technology

[0002] With the increasing urgency of energy conservation, weight reduction, and performance improvement demands in high-end equipment sectors such as aerospace, rail transportation, and new energy vehicles, lightweighting has become one of the core directions for the development of advanced materials. As the mainstream material for key load-bearing structural components, the lightweight design of steel materials has significant strategic importance and application value. Against this backdrop, Fe-Mn-Al-C lightweight steel, characterized by its high specific strength, has attracted widespread attention. This type of steel, by adding a higher proportion of lightweight elements such as Mn and Al to replace some traditional alloying elements, significantly reduces the material density while effectively maintaining or improving its mechanical properties through the strengthening effect of various nanoscale precipitates such as κ-carbides and B2 phases, demonstrating excellent comprehensive performance potential and economic advantages.

[0003] However, the compositional design of lightweight steel presents a typical performance trade-off challenge. Studies have shown that while the density of the material continues to decrease with the increase of densification elements such as Al, its key mechanical properties, such as room temperature and high temperature strength and plasticity, may show a significant decline. At the same time, the material's work hardening behavior, phase transformation characteristics, and final microstructure also undergo complex changes. Therefore, how to achieve a synergistic effect of high strength and high toughness while ensuring low density through precise design and microalloying of multi-component components is the primary scientific problem currently facing the research and development of lightweight steel materials.

[0004] Meanwhile, advanced forming technologies, represented by laser additive manufacturing, have provided a new approach for the integrated and high-performance manufacturing of complex lightweight steel components. This technology, with its high flexibility, rapid prototyping, and near-net-shape forming capabilities, is particularly suitable for the aerospace industry's demand for customized, lightweight components. However, lightweight steel, especially high-aluminum-content lightweight steel, faces severe process challenges in laser additive manufacturing. High Al content easily leads to changes in molten pool viscosity and surface tension, increasing process instability and causing forming defects such as porosity and hot cracking. Furthermore, the extreme non-equilibrium thermal cycle unique to rapid laser melting and solidification easily causes the segregation of elements such as Al and Mn at the microscale, resulting in inhomogeneous microstructure, abnormal phase composition, and the precipitation of harmful brittle phases, thus severely restricting the reliability and consistency of the component's mechanical properties. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one aspect of the present invention is to provide a method for preparing Fe-Mn-Al-Ni-C lightweight steel alloy, the specific steps of which are as follows: S1. Prepare Fe-Mn-Al-Ni-C alloy powder by using a vacuum induction melting gas atomizing furnace, a tightly coupled nozzle, and a powder sieving equipment according to the component ratio; S2. Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate; S3. Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy, and perform layer-by-layer printing and deposition of Fe-Mn-Al-Ni-C alloy; S4. Heat-treat the Fe-Mn-Al-Ni-C alloy produced by laser additive manufacturing.

[0006] Preferably, the composition of S1 is as follows: Mn is 10wt.%-35wt.%, Al is 3wt.%-13wt.%, Ni is 4wt.%-14wt.%, C is 0.3wt.%-1.5wt.%, and the remainder is Fe.

[0007] Preferably, the vacuum induction melting gas atomizing furnace in S1 has a melting temperature of 1580℃-1620℃ and a holding time of 15min-30min.

[0008] Preferably, in S1, under the conditions of atomization pressure of 3MPa and metal flow velocity of 16kg / min for the tightly coupled nozzle, alloy powder is obtained after atomization cooling for 40min.

[0009] Preferably, in S1, the sieving equipment sieves the powder particles into D10=14μm±7μm, D50=36μm±10μm, and D90=65μm±10μm, and then vacuum-dries them at 80℃-120℃ for 1 hour before vacuum sealing.

[0010] Preferably, the pre-positioning method in S2 is scraping, the thickness of a single-layer powder bed is 36μm±10μm, and the substrate preheating temperature is 100℃-300℃.

[0011] Preferably, in S3, the laser power is 80W-140W, the galvanometer scanning speed is 700mm / s-1200mm / s, the overlap rate is 40%-70%, the laser spot size is 55μm-100μm, and the laser scanning deflection angle is 0-180°.

[0012] Preferably, the ambient oxygen content during the laser additive manufacturing process in S3 is ≤100ppm, and the scanning path is one or more of the following: "Z", "S", ring or loop.

[0013] Preferably, the heat treatment in S4 is annealing heat treatment, with a temperature range of 1000℃-1200℃, a holding time of 0.5h-2h, and a furnace cooling method.

[0014] Preferably, the heat treatment in S4 is an aging treatment with a temperature range of 600℃-700℃ and a holding time of 2h-6h. When the aging treatment temperature is 600℃~650℃, the preferred holding time is 3h-6h.

[0015] The beneficial effects of this invention are as follows: Successfully achieving a synergistic balance between lightweight design and high performance: This invention, through optimized Fe-Mn-Al-Ni-C composition system design, achieves a density ≤7 g / cm³. 3 The lightweight steel alloy has a significantly lower density than traditional structural steel, effectively meeting the urgent needs of aerospace, transportation and other fields for material weight reduction. At the same time, through precise composition control and subsequent heat treatment processes, the material achieves a high strength level of yield strength ≥900MPa and ultimate tensile strength ≥1GPa on the basis of low density, overcoming the technical problem of "reduced density and loss of strength" that is common in lightweight steel.

[0016] This invention addresses a key technological bottleneck in additive manufacturing of high-strength lightweight steel: It clarifies the range of laser additive manufacturing and heat treatment process parameters applicable to this material system. Through optimized laser scanning strategies and process parameters, it successfully suppresses defects such as porosity and cracks that are easily caused by high Al content, and obtains high-quality formed blanks with a density of ≥99%, providing a reliable process guarantee for the direct near-net-shape forming of lightweight components with complex structures.

[0017] This invention establishes a controllable technological path integrating "composition-process-structure-performance": It systematically integrates and synergistically optimizes material composition design, laser additive manufacturing, and heat treatment processes. By controlling the content of key elements such as Fe, Mn, Al, Ni, and C, combined with specific laser manufacturing parameters and subsequent annealing / aging treatments, it achieves effective control over the alloy's microstructure (such as the type, size, and distribution of precipitates) and phase composition, thereby stably obtaining the expected high mechanical properties. This method features a clear process chain and strong controllability.

[0018] Possessing excellent technical feasibility and promising prospects for industrial application: The powder pre-placed laser additive manufacturing technology adopted in this invention is highly mature, with a relatively simple process flow and no special requirements for equipment. The entire preparation process (from powder to final high-performance parts) is efficient and controllable, and the resulting products have excellent and stable performance, making it easy to achieve large-scale production. This lays a solid technical foundation for the industrial application of high-performance lightweight steel in the field of high-end equipment.

[0019] In summary, this invention not only provides a lightweight steel alloy material that combines low density, ultra-high strength, and high density, but also provides a complete and controllable composition and process scheme for preparing this material, which has significant technological breakthrough and broad application value.

[0020] Additional aspects and advantages of the invention will become apparent from the description which follows, or may be learned by practice of the invention. Attached Figure Description

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 These are electron microscope images of lightweight steel alloy spherical powder materials prepared by vacuum atomization in Embodiments 1 and 2 of this invention; Figure 2 These are the microstructures of Embodiment 1 and Comparative Example 1 of the present invention; Figure 3 These are the stretching curves of Embodiment 1 and Comparative Example 1 of the present invention; Figure 4 These are the microstructures of Examples 2 to 4 and Comparative Example 2 of the present invention; Figure 5 These are the stretching curves of Embodiments 2 to 4 and Comparative Examples 2 and 3 of the present invention; Figure 6 The microstructures of Comparative Examples 1, 2, 4, and 5 of this invention are shown. Figure 7 These are the tensile property data of Embodiments 1 to 4 and Comparative Examples 1 to 5 of the present invention. Detailed Implementation

[0022] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0023] 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 implemented in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0024] Example 1 Step 1: Prepare spherical Fe-Mn-Al-Ni-C alloy powder (e.g., by vacuum atomization) Figure 1 As shown), the powder purity is ≥99%, and the powder particle size is: D10=8.0μm, D50=32.8μm, D90=58.8μm. The Fe-Mn-Al-Ni-C powder material has the following element contents: Mn 30wt.%, Al 11wt.%, Ni 12wt.%, C 1wt.%, and the remainder is Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 95W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°; Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z".

[0025] Step 5: The Fe-Mn-Al-Ni-C alloy manufactured by laser additive manufacturing is subjected to annealing heat treatment at a temperature of 1100℃ for 1 hour and furnace cooling. The density of the annealed lightweight steel alloy is approximately 6.1 g / cm³. 3 The density was 98.2%, and the size and distribution density of the precipitated phases in the microstructure increased significantly compared to before heat treatment (e.g., Figure 2 As shown), the yield strength in the tensile test was 930.2 MPa, and the ultimate tensile strength was 1021.1 MPa (as shown). Figure 3 (As shown).

[0026] Example 2 Step 1: Prepare spherical Fe-Mn-Al-Ni-C alloy powder (e.g., by vacuum atomization) Figure 1 As shown), the powder purity is ≥99%, and the powder particle size is: D10=20.8μm, D50=40.0μm, D90=69.8μm. The Fe-Mn-Al-Ni-C powder material has the following elements: Mn content 15wt.%, Al content 5.5wt.%, Ni content 6.0wt.%, C content 0.5wt.%, and the remainder is Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 120W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°. Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z" shape; Step 5: Perform aging heat treatment on the laser additive manufacturing Fe-Mn-Al-Ni-C alloy. The aging temperature is 600℃, the holding time is 4h, and the cooling method is air cooling. The density of the lightweight steel alloy after aging treatment is approximately 6.9 g / cm³. 3 The density was 99.4%, and the size and distribution density of the precipitates in the microstructure showed a slight increase compared to before heat treatment (e.g., Figure 4 As shown), the yield strength in the tensile test was 937.7 MPa, and the ultimate tensile strength was 1025.1 MPa (as shown). Figure 5 (As shown).

[0027] Example 3 Step 1: Spherical Fe-Mn-Al-Ni-C alloy powder was prepared by vacuum atomization. The powder purity was ≥99%, and the powder particle size was: D10=20.8μm, D50=40.0μm, D90=69.8μm. The Fe-Mn-Al-Ni-C powder material contained 15wt.% Mn, 5.5wt.% Al, 6.0wt.% Ni, and 0.5wt.% C, with the remainder being Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 120W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°. Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z" shape; Step 5: Perform aging heat treatment on the laser additive manufacturing Fe-Mn-Al-Ni-C alloy. The aging temperature is 650℃, the holding time is 2h, and the cooling method is air cooling. The density of lightweight steel alloy is approximately 6.9 g / cm³. 3 The density was 99.4%, and the size and distribution density of the precipitates in the microstructure further increased (e.g., Figure 4 As shown), the yield strength in the tensile test was 943.6 MPa, and the ultimate tensile strength was 1116.9 MPa (as shown). Figure 5 (As shown).

[0028] Example 4 Step 1: Spherical Fe-Mn-Al-Ni-C alloy powder was prepared by vacuum atomization. The powder purity was ≥99%, and the powder particle size was: D10=20.8μm, D50=40.0μm, D90=69.8μm. The Fe-Mn-Al-Ni-C powder material contained 15wt.% Mn, 5.5wt.% Al, 6.0wt.% Ni, and 0.5wt.% C, with the remainder being Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 120W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°. Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z" shape; Step 5: Perform aging heat treatment on the laser additive manufacturing Fe-Mn-Al-Ni-C alloy. The aging temperature is 650℃, the holding time is 4h, and the cooling method is air cooling. The density of lightweight steel alloy is approximately 6.9 g / cm³. 3 The density was 99.4%, and the uniformity of the precipitated phase distribution in the microstructure was significantly improved (e.g., Figure 4 As shown), the yield strength in the tensile test was 985.7 MPa, and the ultimate tensile strength was 1150.4 MPa (as shown). Figure 5 (As shown).

[0029] Comparative Example 1 Step 1: Spherical Fe-Mn-Al-Ni-C alloy powder was prepared by vacuum atomization. The powder purity was ≥99%, and the powder particle size was D10=8.0μm, D50=32.8μm, D90=58.8μm. The Fe-Mn-Al-Ni-C powder material had the following element contents: Mn 30wt.%, Al 11wt.%, Ni 12wt.%, C 1wt.%, and the remainder was Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 95W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°; Step 4: Perform layer-by-layer printing and deposition of the Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100 ppm and a "Z" shaped scanning path; the density of the lightweight steel alloy is approximately 6.1 g / cm³. 3 The density is 98.2%, and the precipitated phase in the microstructure is a fine network structure (such as...). Figure 2 As shown), the yield strength in the tensile test was 821.1 MPa, and the ultimate tensile strength was 837.5 MPa (as shown). Figure 3 (As shown).

[0030] Comparative Example 2 Step 1: Spherical Fe-Mn-Al-Ni-C alloy powder was prepared by vacuum atomization. The powder purity was ≥99%, and the powder particle size was: D10=20.8μm, D50=40.0μm, D90=69.8μm. The Fe-Mn-Al-Ni-C powder material contained 15wt.% Mn, 5.5wt.% Al, 6.0wt.% Ni, and 0.5wt.% C, with the remainder being Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 120W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°. Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z" shape; The density of lightweight steel alloy is approximately 6.9 g / cm³. 3 The density is 99.4%, and the fine precipitates in the microstructure also exhibit a network-like morphology (e.g., Figure 4 As shown), the yield strength in the tensile test was 736.9 MPa, and the ultimate tensile strength was 943.5 MPa (as shown). Figure 5 (As shown).

[0031] Comparative Example 3 Step 1: Spherical Fe-Mn-Al-Ni-C alloy powder was prepared by vacuum atomization. The powder purity was ≥99%, and the powder particle size was: D10=20.8μm, D50=40.0μm, D90=69.8μm. The Fe-Mn-Al-Ni-C powder material contained 15wt.% Mn, 5.5wt.% Al, 6.0wt.% Ni, and 0.5wt.% C, with the remainder being Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 120W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°. Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z" shape; Step 5: Perform aging heat treatment on the laser additive manufacturing Fe-Mn-Al-Ni-C alloy. The aging temperature is 600℃, the holding time is 2h, and the cooling method is air cooling. The density of lightweight steel alloy is approximately 6.9 g / cm³. 3 The density is 99.4%, the yield strength is 884.8 MPa, and the ultimate tensile strength is 1025.1 MPa (e.g., Figure 5 (As shown).

[0032] Comparative Example 4 Step 1: Spherical Fe-Mn-Al-Ni-C alloy powder was prepared by vacuum atomization. The powder purity was ≥99%, and the powder particle size was D10=8.0μm, D50=32.8μm, D90=58.8μm. The Fe-Mn-Al-Ni-C powder material had the following element contents: Mn 30wt.%, Al 11wt.%, Ni 12wt.%, C 1wt.%, and the remainder was Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 90W, galvanometer scanning speed 800mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°; Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z" shape; Lightweight steel alloys contain numerous pore defects (such as...) Figure 6 As shown in the figure, the density is approximately 5.9 g / cm³. 3 The density is 97.5%, the yield strength is 800.8 MPa, and the ultimate tensile strength is 825.7 MPa (e.g., Figure 7 (As shown).

[0033] Comparative Example 5 Step 1: Spherical Fe-Mn-Al-Ni-C alloy powder was prepared by vacuum atomization. The powder purity was ≥99%, and the powder particle size was: D10=20.8μm, D50=40.0μm, D90=69.8μm. The Fe-Mn-Al-Ni-C powder material contained 15wt.% Mn, 5.5wt.% Al, 6.0wt.% Ni, and 0.5wt.% C, with the remainder being Fe. Step 2: Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate by a scraping method. The thickness of a single powder bed is about 30μm, and the substrate preheating temperature is 140℃. Step 3: Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy: laser power 95W, galvanometer scanning speed 1400mm / s, overlap rate 60%, laser spot size 70μm, and laser scanning deflection angle 67°. Step 4: Perform layer-by-layer printing and stacking of Fe-Mn-Al-Ni-C alloy, with an ambient oxygen content of 100ppm and a scanning path of "Z" shape; Significant porosity defects exist in lightweight steel alloys (such as...) Figure 6 (As shown), density is approximately g / cm³ 3 The density is 78.5%, the yield strength is 518.1 MPa, and the ultimate tensile strength is 628.1 MPa (e.g., Figure 7 (As shown).

[0034] As shown in Example 1 and Comparative Example 1, further annealing after laser additive manufacturing of Fe-Mn-Al-Ni-C alloy can improve the yield strength and ultimate tensile strength of lightweight steel. As shown in Examples 2, 3, 4, and Comparative Example 2, aging treatment can also improve the yield strength and ultimate tensile strength of additively manufactured lightweight steel alloys. The improvement in the strength of lightweight steel alloys is mainly due to the elimination of grain defects and the homogenization of precipitated phases during heat treatment. Figure 2 and Figure 4 ).

[0035] As shown in Examples 2, 3, 4, and Comparative Example 3, the temperature and time of aging heat treatment are important factors affecting the strength of lightweight steel alloys. With increasing aging temperature and time, the degree of grain defect elimination and precipitate homogenization transformation improves (…). Figure 4 This leads to a gradual increase in the yield strength and ultimate tensile strength of lightweight steel alloys. Figure 5 ).

[0036] According to Comparative Examples 1 and 2, reducing the levels of Mn, Al, Ni, and C in lightweight steel alloys increases the alloy density; however, its formability and strength gradually improve. According to Comparative Examples 1 and 4, and Comparative Examples 2 and 5, (…) Figure 6 When the laser power decreases or the scanning speed increases, the decrease in laser energy density leads to an increase in porosity defects in the lightweight steel alloy, resulting in a decrease in alloy density, compactness, and strength. Figure 7 ).

[0037] Based on the above embodiments and comparative examples, it can be seen that by optimizing the composition of lightweight steel alloys and the parameters of laser additive manufacturing and heat treatment processes, a density ≤7g / cm³ can be obtained. 3 Lightweight steel alloy with a density ≥98%, yield strength ≥900MPa, and ultimate tensile strength ≥1GPa. Figure 7 ).

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy, characterized in that: The specific steps of the preparation method are as follows: S1. Prepare Fe-Mn-Al-Ni-C alloy powder by using a vacuum induction melting gas atomizing furnace, a tightly coupled nozzle, and a powder sieving equipment according to the component ratio; S2. Fe-Mn-Al-Ni-C alloy powder is pre-placed on the surface of the substrate; S3. Set the laser additive manufacturing process parameters for Fe-Mn-Al-Ni-C alloy, and perform layer-by-layer printing and deposition of Fe-Mn-Al-Ni-C alloy; S4. Heat-treat the Fe-Mn-Al-Ni-C alloy produced by laser additive manufacturing.

2. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: The composition of S1 is as follows: Mn is 10wt.%-35wt.%, Al is 3wt.%-13wt.%, Ni is 4wt.%-14wt.%, C is 0.3wt.%-1.5wt.%, and the remainder is Fe.

3. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: The vacuum induction melting gas atomizing furnace in S1 has a melting temperature of 1580℃-1620℃ and a holding time of 15min-30min.

4. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: Under the conditions of atomization pressure of 3MPa and metal flow velocity of 16kg / min in the tightly coupled nozzle of S1, alloy powder is obtained after atomization and cooling for 40min.

5. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: The sieving equipment in S1 sieves the powder particles into D10=14μm±7μm, D50=36μm±10μm, and D90=65μm±10μm. After vacuum drying at 80℃-120℃ for 1 hour, the powder is vacuum sealed.

6. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: The pre-positioning method in S2 is scraping, with a single-layer powder bed thickness of 36μm±10μm and a substrate preheating temperature of 100℃-300℃.

7. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: In S3, the laser power is 80W-140W, the galvanometer scanning speed is 700mm / s-1200mm / s, the overlap rate is 40%-70%, the laser spot size is 55μm-100μm, and the laser scanning deflection angle is 0-180°.

8. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: In the laser additive manufacturing process described in S3, the ambient oxygen content is ≤100ppm, and the scanning path is one or more of the following: "Z", "S", ring or loop.

9. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: The heat treatment in S4 is annealing heat treatment, with a temperature range of 1000℃-1200℃, a holding time of 0.5h-2h, and a furnace cooling method.

10. The method for preparing a Fe-Mn-Al-Ni-C lightweight steel alloy according to claim 1, characterized in that: The heat treatment in S4 is an aging treatment with a temperature range of 600℃-700℃ and a holding time of 2h-6h. When the aging treatment temperature is 600℃~650℃, the preferred holding time is 3h-6h.

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