A method for preparing an as-cast corrosion-resistant rare earth magnesium-based composite material

Abstract

A method for preparing a cast corrosion-resistant rare-earth magnesium-based composite material, belonging to the field of rare-earth magnesium-based composite material preparation technology, solves the technical problems of insufficient corrosion resistance and coarse second-phase grains in high-content rare-earth magnesium alloys, including the following steps: S1, SiC p Pretreatment; S2, Weighing raw materials; S3, Applying a high-temperature resistant coating agent after preheating the crucible; S4, Melting pure Mg blocks; S5, Adding pure Zn granules to the magnesium melt to obtain an alloy liquid; S6, Adding the pretreated SiC... p The alloy is uniformly dispersed in the molten alloy; S7, magnesium gadolinium and magnesium yttrium master alloys are added to the molten alloy; S8, die casting is performed. This invention introduces SiC into rare earth magnesium alloys. p Heterogeneous reinforcement significantly alters the precipitation behavior of the second phase, refining it and enabling its dispersed distribution; simultaneously, SiC p The introduction of [a specific substance] can also reduce the volume fraction of the second phase, increase the solid solubility of alloying elements, and thus optimize the chemical composition of the oxide film, thereby further improving the corrosion resistance of the alloy.

Description

Technical Field

[0001] This invention belongs to the field of rare earth magnesium-based composite material preparation technology, specifically relating to a method for preparing a cast corrosion-resistant rare earth magnesium-based composite material. Background Technology

[0002] Magnesium alloys possess high specific strength, specific stiffness, and excellent electromagnetic shielding properties, making them promising candidates for applications in aerospace, automotive lightweighting, and 3C electronic products. However, the oxide film forming on the surface of magnesium alloys is porous and lacks protective properties, exhibiting poor thermodynamic stability and physical barrier performance, thus failing to effectively prevent continuous corrosion from corrosive media. Furthermore, due to the low potential of the magnesium matrix, the potential difference between the second phase and the matrix often induces severe microgalvanic corrosion, impairing the alloy's corrosion resistance and significantly hindering the large-scale production and application of magnesium alloys.

[0003] Adding rare earth elements (such as Gd and Y) to the magnesium matrix is ​​an effective way to improve the microstructure and properties of magnesium alloys. Most of the second phases in magnesium alloys have a good strengthening effect; however, the potential of the second phase is higher than that of the magnesium matrix, and there is a significant potential difference between the two phases. This leads to micro-galvanic corrosion between the two phases, which reduces the alloy's corrosion resistance. In recent years, the application of magnesium alloys has become increasingly high-end, with strong demand in aerospace, radar electronics, and defense industries, significantly increasing the requirements for high-temperature stability. Currently, the mainstream technical solution is to add high-content rare earth elements to form a high-density, high-temperature stable rare earth phase, thereby improving the high-temperature performance of magnesium alloys. However, the corrosion resistance of the alloy is also affected by factors such as the type, distribution, and content of the second phase. The addition of high-content rare earth elements introduces coarse Mg-RE second phases, further exacerbating micro-galvanic corrosion between the second phase and the matrix. Therefore, how to improve the corrosion resistance of high-rare-earth content magnesium alloys is a pressing problem that needs to be solved.

[0004] Existing technologies primarily mitigate microgalvanic corrosion by reducing the size and volume fraction of the second phase in alloys through heat treatment. However, rare earth phases typically have high solution temperatures, such as Mg5Gd (melting point 658℃) and Mg3Zn3Gd2 (melting point above 530℃). These second phases have high melting points, and once formed during solidification, they are difficult to refine or eliminate through hot working. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings of existing technologies, solve the technical problems of insufficient corrosion resistance in high-content rare-earth magnesium alloys and the difficulty in refining or eliminating the second phase through hot working, and provide a method for preparing as-cast Mg-5Gd-3Zn-1Y corrosion-resistant rare-earth magnesium-based composite materials, using SiC pUnder the regulation of the material, the second phase structure of the composite material becomes more uniform and refined, and the distribution of rare earth phase in the matrix is ​​changed, which significantly improves the corrosion resistance of the entire alloy. A dense and highly protective corrosion product film can be generated on the surface of the composite material, thus enabling rare earth magnesium-based composite materials to have good corrosion resistance in complex service environments.

[0006] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a cast corrosion-resistant rare earth magnesium-based composite material, comprising the following steps: S1, SiC p Pretreatment: SiC with an average particle size of 8-12 μm p The pretreated SiC is obtained by sequentially washing with water, acid washing, washing with water, drying, and sieving. p spare; S2. Weighing raw materials: Weigh pure Mg blocks, pure Zn granules, Mg-30Gd master alloy, and Mg-30Y master alloy according to the composition and mass percentage content of the cast corrosion-resistant rare earth magnesium-based composite material. The blocky raw materials are ground to remove the surface oxide scale before use in the next step. The composition and mass percentage content of the cast corrosion-resistant rare earth magnesium-based composite material are: Gd: 4-6 wt.%, Y: 0.5-1.5 wt.%, Zn: 3-5 wt.%, with the balance being Mg. S3. Place the clean crucible into the melting furnace for preheating. When the preheated temperature of the crucible reaches 450-550℃, take it out and evenly coat the inner wall of the crucible with a high-temperature resistant coating agent. The purpose is to prevent impurities in the crucible from falling off and affecting the purity of the substrate. S4. After the high-temperature resistant coating agent has completely cured, heat the melting furnace to 740-760℃, add the pure Mg block prepared in step S2 into the crucible, and continuously introduce a protective atmosphere into the melting furnace during the melting process of the pure Mg block. After all the pure Mg block has melted, magnesium liquid is obtained. S5. When the magnesium liquid is cooled to 700-720℃ with the furnace, remove the oxide layer generated on the surface of the magnesium liquid, then add the pure Zn particles prepared in step S2 to the magnesium liquid and stir for 30-90s, and finally keep it at the temperature for 10-20min to obtain the alloy liquid; during the holding process, place the stirring paddle coated with high temperature resistant coating above the alloy liquid for preheating. S6. First, wrap the SiC pretreated in step S1 with aluminum foil. p The crucible is then placed in a stainless steel crucible and transferred to a muffle furnace for preheating at a temperature of 590-610℃ for later use. Then, when the alloy liquid obtained in step S5 is cooled to 660-680°C in the furnace, the oxide layer generated on the surface of the alloy liquid is removed for the second time. Then, a preheated stirring paddle is placed in the alloy liquid and placed in the middle and lower part of the alloy liquid. The stirring device is started for mechanical stirring for 3-5 minutes. Finally, after the alloy liquid forms a stable eddy, remove the SiC preheated in step S6. p Slowly add SiC to the molten alloy, the feeding process lasting 10-15 minutes. p The amount of SiC added is 2%-10% of the total volume of the alloy liquid. After addition, staged variable-speed stirring is performed: for the first 5-15 minutes, the stirring speed is 300-350 rpm; for the last 15-25 minutes, the stirring speed is 400-500 rpm to ensure the SiC... p It can be evenly dispersed in the melt; S7. Reheat the melting furnace to 710-720℃, stirring continuously during the reheating process. When the temperature reaches the target temperature, keep it heated while stirring for 10-15 minutes to carry out dispersion treatment. Then, put the Mg-30Gd master alloy and Mg-30Y master alloy prepared in step S2 into the alloy liquid. After the solid alloy melts, start the stirring device again for mechanical stirring. S8. First, preheat the casting mold to 380-420℃; then, remove the oxide layer generated on the surface of the alloy liquid prepared in step S7 three times, pour the alloy liquid into the mold for die casting, with a pressure of 400-500kN and a holding time of 150-200s; finally, after the holding time is completed, remove the mold and air cool it to room temperature to obtain a cast corrosion-resistant rare earth magnesium-based composite material ingot.

[0007] Further, in step S1, SiC p Preprocessing includes the following steps: S1-1, First, SiC p Wash the SiC with deionized water 3-5 times. p After removal, add 5-10 wt.% HF solution for acid washing, stir thoroughly and let stand for at least 5 minutes to remove surface oxides; S1-2, Rinse the acid-washed SiC again with deionized water. p Continue this process until the pH of the washing solution reaches 6.5-7.5; S1-3, the cleaned SiC p Lay it flat on a tray lined with aluminum foil and dry it at 80-100℃ until constant weight, with a drying time of not less than 24 hours; S1-4, the dried SiC pThe SiC was uniformly dispersed in an ultrasonic vibrating sieve and passed through a sieve with a 10 μm aperture. p Pretreated SiC was obtained by sealing and storing it. p .

[0008] Further, in step S2, the purity of the magnesium block is ≥99.9%, the purity of the zinc granules is ≥99.9%, the purity of the Mg-30Gd master alloy is ≥99.9%, and the purity of the Mg-30Y master alloy is ≥99.9%.

[0009] Further, in step S3, the high-temperature resistant coating agent is composed of talc powder coating and zinc oxide coating. The composition and ratio of the talc powder coating are: 80g talc powder, 20g water glass and 250ml water; the ratio of the zinc oxide coating is: 45g zinc oxide, 45g water glass and 250ml water.

[0010] Furthermore, in step S4, the protective atmosphere is a mixture of CO2 and SF6, with a volume ratio of CO2 to SF6 of 99:1.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention employs a segmented variable-speed stirring process during the stirring process, which effectively suppresses the growth of SiC. p Agglomeration and sedimentation within the melt ensure a more uniform microstructure in the prepared composite material; 2. This invention directly prepares rare earth magnesium-based composite materials, eliminating the need for subsequent heat treatment, simplifying the process, and reducing the complexity of the process; at the same time, the preparation process is more controllable. 3. This invention introduces SiC into rare earth magnesium alloys. p This significantly refines the size of the second phase, reducing the tendency for micro-galvanic corrosion between the rare earth phase and the magnesium matrix; simultaneously, it optimizes the distribution of the second phase in the matrix, allowing the rare earth phase to... p Enrichment in the surrounding area effectively weakens the interfacial effect between particles and the matrix; 4. In the rare earth magnesium-based composite material prepared by this invention, the size of the second phase is significantly reduced and its distribution is more uniform. Hydrogen evolution test results in a 3.5 wt.% NaCl solution for 72 hours show that its hydrogen evolution rate is significantly higher than that without the addition of SiC. p The rare earth magnesium alloy has a reduction of one order of magnitude, resulting in a significant improvement in corrosion resistance.

[0012] In summary, this invention introduces SiC into rare earth magnesium alloys. p Heterogeneous reinforcements can serve as heterogeneous nucleation sites for grains and the second phase during solidification, significantly altering the precipitation behavior of the second phase, refining it, and promoting its dispersed distribution. Simultaneously, SiC...p The introduction of [a specific substance] can also reduce the volume fraction of the second phase, increase the solid solubility of alloying elements, and thus optimize the chemical composition of the oxide film, thereby further improving the corrosion resistance of the alloy. Attached Figure Description

[0013] Figure 1 As-cast SiC prepared in Example 1 p Surface microstructure of / Mg-5Gd-3Zn-1Y corrosion-resistant rare earth magnesium matrix composite material; Figure 2 As-cast SiC prepared in Example 1 p SiC in Mg-5Gd-3Zn-1Y corrosion-resistant rare earth magnesium matrix composites p SEM and EDS images; Figure 3 As-cast SiC prepared in Example 1 p Microstructure morphology of the oxide film layer of / Mg-5Gd-3Zn-1Y corrosion-resistant rare earth magnesium matrix composite material after immersion in NaCl solution (mass fraction 3.5%) for 72 h; Figure 4 The surface microstructure morphology of the as-cast Mg-5Gd-3Zn-1Y alloy prepared in Comparative Example 1 is shown in the figure. Figure 5 Comparative Example 1 and Example 1: Microstructure of oxide film layers after immersion in 3.5% NaCl solution for 72 hours. Figure 6 The hydrogen evolution curves and hydrogen evolution rate curves of the cast rare earth magnesium alloys prepared in Example 1 and Comparative Example 1 after immersion in a 3.5% NaCl solution for 72 hours are shown. Detailed Implementation

[0014] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Example 1

[0015] A method for preparing a cast corrosion-resistant rare earth magnesium-based composite material includes the following steps: S1, SiC p Pretreatment: SiC with an average particle size of 8 μm was subjected to pretreatment. p The pretreated SiC is obtained by sequentially washing with water, acid washing, washing with water, drying, and sieving. p Backup; SiC p Preprocessing includes the following steps: S1-1, First, SiC p Wash the SiC three times with deionized water. pAfter removal, add 5 wt.% HF solution for acid washing, stir thoroughly, and let stand for 5 minutes. S1-2, Rinse the acid-washed SiC again with deionized water. p Continue until the pH of the washing solution reaches 7; S1-3, the cleaned SiC p Lay it flat on a tray lined with aluminum foil and dry it at 80°C until constant weight for 24 hours; S1-4, the dried SiC p The SiC was uniformly dispersed in an ultrasonic vibrating sieve and passed through a sieve with a 10 μm aperture. p Pretreated SiC was obtained by sealing and storing it. p .

[0016] S2. Weighing Raw Materials: Weigh pure Mg blocks, pure Zn granules, Mg-30Gd master alloy, and Mg-30Y master alloy according to the composition and mass percentage content of the cast corrosion-resistant rare earth magnesium matrix composite material. The blocky raw materials are ground to remove the surface oxide scale before use in the next step. The composition and mass percentage content of the cast corrosion-resistant rare earth magnesium matrix composite material are: Gd: 5wt.%, Y: 1wt.%, Zn: 3wt.%, with the balance being Mg. The purity of the magnesium blocks is ≥99.9%, the purity of the zinc granules is ≥99.9%, the purity of the Mg-30Gd master alloy is ≥99.9%, and the purity of the Mg-30Y master alloy is ≥99.9%.

[0017] S3. Place the clean crucible into the melting furnace for preheating. When the preheated temperature of the crucible reaches 500°C, remove it and evenly coat the inner wall of the crucible with a high-temperature resistant coating agent. The high-temperature resistant coating agent consists of talc powder coating and zinc oxide coating. The composition and ratio of the talc powder coating are: 80g talc powder, 20g water glass and 250ml water. The ratio of the zinc oxide coating is: 45g zinc oxide, 45g water glass and 250ml water.

[0018] S4. After the high-temperature resistant coating agent has completely cured, heat the melting furnace to 740°C, add the pure Mg block prepared in step S2 into the crucible, and continuously introduce a protective atmosphere into the melting furnace during the melting process of the pure Mg block. After all the pure Mg block has melted, magnesium liquid is obtained. The protective atmosphere is a mixed gas composed of CO2 and SF6, and the volume ratio of CO2 to SF6 is 99:1.

[0019] S5. When the magnesium liquid is cooled to 710°C in the furnace, remove the oxide layer generated on the surface of the magnesium liquid, then add the pure Zn particles prepared in step S2 to the magnesium liquid and stir for 40 seconds. Finally, keep it at the temperature for 10 minutes to obtain the alloy liquid. During the heat preservation process, place the stirring paddle coated with high temperature resistant coating above the alloy liquid for preheating.

[0020] S6. First, wrap the SiC pretreated in step S1 with aluminum foil. p The crucible is then placed in a stainless steel crucible and transferred to a muffle furnace for preheating at 610°C for later use. Then, when the alloy liquid obtained in step S5 is cooled to 660°C in the furnace, the oxide layer generated on the surface of the alloy liquid is removed for the second time. Then, a preheated stirring paddle is placed in the alloy liquid and placed in the middle and lower part of the alloy liquid. The stirring device is started for mechanical stirring for 3 minutes. Finally, after the alloy liquid forms a stable eddy, remove the SiC preheated in step S6. p Slowly add SiC to the molten alloy, the feeding process lasting 12 minutes. p The amount of additive is 5% of the total volume of the alloy liquid. After the addition is complete, the stirring is carried out in stages with variable speed: the stirring speed is 300 rpm for the first 5 minutes and 400 rpm for the last 15 minutes.

[0021] S7. Reheat the melting furnace to 720℃. Stir continuously during the reheating process. When the temperature reaches the target temperature, keep it heated for 12 minutes while stirring to carry out dispersion treatment. Then, put the Mg-30Gd master alloy and Mg-30Y master alloy prepared in step S2 into the alloy liquid. After the solid alloy melts, start the stirring device again for mechanical stirring. S8. First, preheat the casting mold to 400℃; then, remove the oxide layer generated on the surface of the alloy liquid prepared in step S7 three times, pour the alloy liquid into the mold for die casting, with a pressure of 450kN and a holding time of 150s; finally, after the holding time is completed, take it out and air cool it to room temperature to obtain a cast corrosion-resistant rare earth magnesium-based composite material ingot.

[0022] Depend on Figure 1 It can be seen that the as-cast SiC prepared in Example 1 p In the corrosion-resistant rare earth magnesium matrix composite material / Mg-5Gd-3Zn-1Y, the size of the second phase is significantly reduced, and the second phase is uniformly distributed on the matrix, with the particles exhibiting a discontinuous network distribution at the grain boundaries.

[0023] Depend on Figure 2 It can be seen that SiC p There are obvious rare earth enrichment areas in the surrounding SiC. p The nucleation of the second phase was suppressed, resulting in a significant reduction in the number of second phases.

[0024] Depend on Figure 3 It can be seen that as-cast SiC pAfter being immersed in a 3.5% NaCl solution for 72 hours, the corrosion morphology of the Mg-5Gd-3Zn-1Y corrosion-resistant rare earth magnesium-based composite material was rough and uneven, with numerous pores and depressions appearing on the surface. Furthermore, SiC was observed on the corrosion product layer. p The presence of these particles indicates that they have a certain hindering effect on the corrosive medium. Comparative Example 1

[0025] A method for preparing a rare earth magnesium alloy includes the following steps: S1. Raw Material Selection: Weigh magnesium blocks, zinc granules, magnesium-gadolinium master alloy, and magnesium-yttrium master alloy to ensure the composition and mass percentage of each element in the raw materials are: Gd: 5 wt.%, Y: 1 wt.%, Zn: 3 wt.%, with the balance being Mg. Mix pure Mg blocks, pure Zn granules, Mg-30Gd (wt.%), and Mg-30Y (wt.%) according to the mass percentage. All block raw materials should be polished to remove the oxide scale on the surface before use in the next step. S2. Place the clean crucible into the melting furnace for preheating. When the preheated temperature of the crucible reaches 500°C, take it out and evenly coat the inner wall of the crucible with a high-temperature resistant coating agent. S3. After the coating agent has completely cured, heat the melting furnace to 740°C and add the magnesium block prepared in step S1 into the crucible. During the melting process of the magnesium block, a protective atmosphere should be continuously introduced into the melting furnace. After all the raw materials have melted, magnesium liquid is obtained. S4. When the magnesium liquid obtained in step S3 is cooled to 710°C, remove the oxide layer formed on the surface of the magnesium liquid, add the zinc granules prepared in step S1 to the magnesium liquid and stir for 45 seconds, then keep it warm for 10 minutes; and place the stirring paddle coated with high temperature resistant coating on the melt for preheating. S5. The melting furnace is heated to 710°C again. During the heating process, the furnace is continuously stirred. When the temperature reaches the target temperature, the magnesium gadolinium master alloy and magnesium yttrium master alloy prepared in step S1 are then placed into the melt. After the solid alloy melts, the stirring paddle coated with high-temperature resistant agent is placed in the furnace for mechanical stirring. S6. Preheat the casting mold to 420℃, then remove the oxide layer generated on the surface of the melt in step S5. Pour the melt into the mold in a measured quantity, setting the pressure to 450kN and maintaining the pressure for 150s for die casting. Finally, remove the ingot and cool it to room temperature to obtain a rare earth magnesium alloy ingot.

[0026] The surface microstructure morphology of the as-cast Mg-5Gd-3Zn-1Y alloy prepared in Comparative Example 1 is as follows: Figure 4 As shown.

[0027] Figure 1 , Figure 4 The comparison shows that the as-cast SiC prepared in Example 1...p The number of the second phase in the corrosion-resistant rare earth magnesium matrix composite material / Mg-5Gd-3Zn-1Y is significantly reduced compared to the Mg-5Gd-3Zn-1Y alloy prepared in Comparative Example 1; in the Mg-5Gd-3Zn-1Y alloy prepared in Comparative Example 1, the semi-continuous second phase is interrupted, and the particles are uniformly dispersed on the matrix.

[0028] Depend on Figure 5 It can be seen that, compared to the as-cast Mg-5Gd-3Zn-1Y alloy, the as-cast SiC... p After being immersed in 3.5% NaCl solution for 72 hours, the thickness of the oxide film obtained after corrosion of the / Mg-5Gd-3Zn-1Y corrosion-resistant rare earth magnesium-based composite material decreased from 188μm to 28μm, and the oxide film layer became denser without obvious microcracks.

[0029] Depend on Figure 6 It can be seen that after immersion in 3.5% NaCl solution for 72 hours, the two as-cast alloys showed better performance compared to the as-cast Mg-5Gd-3Zn-1Y alloy. p The hydrogen evolution volume of the / Mg-5Gd-3Zn-1Y corrosion-resistant rare earth magnesium matrix composite material is significantly reduced, and the hydrogen evolution rate decreases by nearly an order of magnitude. Example 2

[0030] A method for preparing a cast corrosion-resistant rare earth magnesium-based composite material includes the following steps: S1, SiC p Pretreatment: SiC with an average particle size of 10 μm was subjected to pretreatment. p The pretreated SiC is obtained by sequentially washing with water, acid washing, washing with water, drying, and sieving. p Backup; SiC p Preprocessing includes the following steps: S1-1, First, SiC p Wash the SiC three times with deionized water. p After removal, add 7 wt.% HF solution for acid washing, stir thoroughly, and let stand for 5 minutes; S1-2, Rinse the acid-washed SiC again with deionized water. p Continue until the pH of the washing solution reaches 7; S1-3, the cleaned SiC p Lay it flat on a tray lined with aluminum foil and dry it at 90°C until constant weight for 24 hours; S1-4, the dried SiC p The SiC was uniformly dispersed in an ultrasonic vibrating sieve and passed through a sieve with a 10 μm aperture. pPretreated SiC was obtained by sealing and storing it. p .

[0031] S2. Weighing Raw Materials: Weigh pure Mg blocks, pure Zn granules, Mg-30Gd master alloy, and Mg-30Y master alloy according to the composition and mass percentage content of the cast corrosion-resistant rare earth magnesium matrix composite material. The blocky raw materials are ground to remove the surface oxide scale before use in the next step. The composition and mass percentage content of the cast corrosion-resistant rare earth magnesium matrix composite material are: Gd: 4wt.%, Y: 0.5wt.%, Zn: 4wt.%, with the balance being Mg. The purity of the magnesium blocks is ≥99.9%, the purity of the zinc granules is ≥99.9%, the purity of the Mg-30Gd master alloy is ≥99.9%, and the purity of the Mg-30Y master alloy is ≥99.9%.

[0032] S3. Place the clean crucible into the melting furnace for preheating. When the preheated temperature of the crucible reaches 450°C, remove it and evenly coat the inner wall of the crucible with a high-temperature resistant coating agent. The high-temperature resistant coating agent consists of talc powder coating and zinc oxide coating. The composition and ratio of the talc powder coating are: 80g talc powder, 20g water glass and 250ml water. The ratio of the zinc oxide coating is: 45g zinc oxide, 45g water glass and 250ml water.

[0033] S4. After the high-temperature resistant coating agent has completely cured, heat the melting furnace to 750°C, add the pure Mg block prepared in step S2 into the crucible, and continuously introduce a protective atmosphere into the melting furnace during the melting process of the pure Mg block. After all the pure Mg block has melted, magnesium liquid is obtained. The protective atmosphere is a mixed gas composed of CO2 and SF6, and the volume ratio of CO2 to SF6 is 99:1.

[0034] S5. When the magnesium liquid is cooled to 710°C in the furnace, remove the oxide layer generated on the surface of the magnesium liquid, then add the pure Zn particles prepared in step S2 to the magnesium liquid and stir for 30 seconds. Finally, keep it at the temperature for 15 minutes to obtain the alloy liquid. During the heat preservation process, place the stirring paddle coated with high temperature resistant coating above the alloy liquid for preheating.

[0035] S6. First, wrap the SiC pretreated in step S1 with aluminum foil. p The crucible is then placed in a stainless steel crucible and transferred to a muffle furnace for preheating at 610°C for later use. Then, when the alloy liquid obtained in step S5 is cooled to 680°C in the furnace, the oxide layer generated on the surface of the alloy liquid is removed for the second time. Then, a preheated stirring paddle is placed in the alloy liquid and placed in the middle and lower part of the alloy liquid. The stirring device is started for mechanical stirring for 5 minutes. Finally, after the alloy liquid forms a stable eddy, remove the SiC preheated in step S6.p Slowly add SiC to the molten alloy, the feeding process lasting 15 minutes. p The amount of additive is 2% of the total volume of the alloy liquid. After the addition is complete, the stirring is carried out in stages with variable speed: the stirring speed is 350 rpm for the first 10 minutes and 470 rpm for the last 15 minutes.

[0036] S7. Reheat the melting furnace to 720℃. Stir continuously during the reheating process. When the temperature reaches the target temperature, keep it heated for 15 minutes while stirring to carry out dispersion treatment. Then, put the Mg-30Gd master alloy and Mg-30Y master alloy prepared in step S2 into the alloy liquid. After the solid alloy melts, start the stirring device again for mechanical stirring. S8. First, preheat the casting mold to 420℃; then, remove the oxide layer generated on the surface of the alloy liquid prepared in step S7 three times, pour the alloy liquid into the mold for die casting, with a pressure of 500kN and a holding time of 150s; finally, after the holding time is completed, take it out and air cool it to room temperature to obtain a cast corrosion-resistant rare earth magnesium-based composite material ingot. Example 3

[0037] A method for preparing a cast corrosion-resistant rare earth magnesium-based composite material includes the following steps: S1, SiC p Pretreatment: SiC with an average particle size of 12 μm was subjected to pretreatment. p The pretreated SiC is obtained by sequentially washing with water, acid washing, washing with water, drying, and sieving. p Backup; SiC p Preprocessing includes the following steps: S1-1, First, SiC p Wash the SiC five times with deionized water. p After removal, add 5-10 wt.% HF solution for acid washing, stir thoroughly, and let stand for 5 minutes. S1-2, Rinse the acid-washed SiC again with deionized water. p Continue until the pH of the washing solution reaches 7.5; S1-3, the cleaned SiC p Lay it flat on a tray lined with aluminum foil and dry it at 100°C until constant weight for 24 hours. S1-4, the dried SiC p The SiC was uniformly dispersed in an ultrasonic vibrating sieve and passed through a sieve with a 10 μm aperture. p Pretreated SiC was obtained by sealing and storing it. p .

[0038] S2. Weighing Raw Materials: Weigh pure Mg blocks, pure Zn granules, Mg-30Gd master alloy, and Mg-30Y master alloy according to the composition and mass percentage content of the cast corrosion-resistant rare earth magnesium matrix composite material. The blocky raw materials are ground to remove the surface oxide scale before use in the next step. The composition and mass percentage content of the cast corrosion-resistant rare earth magnesium matrix composite material are: Gd: 6wt.%, Y: 1.5wt.%, Zn: 5wt.%, with the balance being Mg. The purity of the magnesium blocks is ≥99.9%, the purity of the zinc granules is ≥99.9%, the purity of the Mg-30Gd master alloy is ≥99.9%, and the purity of the Mg-30Y master alloy is ≥99.9%.

[0039] S3. Place the clean crucible into the melting furnace for preheating. When the preheated temperature of the crucible reaches 550°C, remove it and evenly coat the inner wall of the crucible with a high-temperature resistant coating agent. The high-temperature resistant coating agent consists of talc powder coating and zinc oxide coating. The composition and ratio of the talc powder coating are: 80g talc powder, 20g water glass and 250ml water. The ratio of the zinc oxide coating is: 45g zinc oxide, 45g water glass and 250ml water.

[0040] S4. After the high-temperature resistant coating agent has completely cured, heat the melting furnace to 760°C, add the pure Mg block prepared in step S2 into the crucible, and continuously introduce a protective atmosphere into the melting furnace during the melting process of the pure Mg block. After all the pure Mg block has melted, magnesium liquid is obtained. The protective atmosphere is a mixed gas composed of CO2 and SF6, and the volume ratio of CO2 to SF6 is 99:1.

[0041] S5. When the magnesium liquid is cooled to 720°C in the furnace, remove the oxide layer generated on the surface of the magnesium liquid, then add the pure Zn particles prepared in step S2 to the magnesium liquid and stir for 90 seconds. Finally, keep it at the temperature for 20 minutes to obtain the alloy liquid. During the heat preservation process, place the stirring paddle coated with high temperature resistant coating above the alloy liquid for preheating.

[0042] S6. First, wrap the SiC pretreated in step S1 with aluminum foil. p The crucible is then placed in a stainless steel crucible and transferred to a muffle furnace for preheating at 610°C for later use. Then, when the alloy liquid obtained in step S5 is cooled to 680°C in the furnace, the oxide layer generated on the surface of the alloy liquid is removed for the second time. Then, a preheated stirring paddle is placed in the alloy liquid and placed in the middle and lower part of the alloy liquid. The stirring device is started for mechanical stirring for 5 minutes. Finally, after the alloy liquid forms a stable eddy, remove the SiC preheated in step S6. p Slowly add SiC to the molten alloy, the feeding process lasting 15 minutes. pThe amount of additive is 10% of the total volume of the alloy liquid. After the addition is complete, the stirring is carried out in stages with variable speed: the stirring speed is 350 rpm for the first 15 minutes and 500 rpm for the last 15 minutes.

[0043] S7. Reheat the melting furnace to 720℃. Stir continuously during the reheating process. When the temperature reaches the target temperature, keep it heated for 15 minutes while stirring to carry out dispersion treatment. Then, put the Mg-30Gd master alloy and Mg-30Y master alloy prepared in step S2 into the alloy liquid. After the solid alloy melts, start the stirring device again for mechanical stirring. S8. First, preheat the casting mold to 420℃; then, remove the oxide layer generated on the surface of the alloy liquid prepared in step S7 three times, pour the alloy liquid into the mold for die casting, with a pressure of 400kN and a holding time of 200s; finally, after the holding time is completed, remove the mold and air cool it to room temperature to obtain a cast corrosion-resistant rare earth magnesium-based composite material ingot.

[0044] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a cast corrosion-resistant rare earth magnesium-based composite material, characterized in that, Includes the following steps: S1, SiC p Pretreatment: SiC with an average particle size of 8-12 μm p The pretreated SiC is obtained by sequentially washing with water, acid washing, washing with water, drying, and sieving. p spare; S2. Weighing raw materials: Weigh pure Mg blocks, pure Zn granules, Mg-30Gd master alloy, and Mg-30Y master alloy according to the composition and mass percentage content of the cast corrosion-resistant rare earth magnesium-based composite material. The blocky raw materials are ground to remove the surface oxide scale before use in the next step. The composition and mass percentage content of the cast corrosion-resistant rare earth magnesium-based composite material are: Gd: 4-6 wt.%, Y: 0.5-1.5 wt.%, Zn: 3-5 wt.%, with the balance being Mg. S3. Place the clean crucible into the melting furnace for preheating. When the preheated temperature of the crucible reaches 450-550℃, take it out and evenly coat the inner wall of the crucible with a high-temperature resistant coating agent. S4. After the high-temperature resistant coating agent has completely cured, heat the melting furnace to 740-760℃, add the pure Mg block prepared in step S2 into the crucible, and continuously introduce a protective atmosphere into the melting furnace during the melting process of the pure Mg block. After all the pure Mg block has melted, magnesium liquid is obtained. S5. When the magnesium liquid is cooled to 700-720℃ in the furnace, remove the oxide layer generated on the surface of the magnesium liquid, then add the pure Zn particles prepared in step S2 into the magnesium liquid and stir for 30-90s, and finally keep it at the temperature for 10-20min to obtain the alloy liquid. During the heat preservation process, the stirring paddle coated with high-temperature resistant agent is placed above the alloy liquid for preheating; S6. First, wrap the SiC pretreated in step S1 with aluminum foil. p The crucible is then placed in a stainless steel crucible and transferred to a muffle furnace for preheating at a temperature of 590-610℃ for later use. Then, when the alloy liquid obtained in step S5 is cooled to 660-680°C in the furnace, the oxide layer generated on the surface of the alloy liquid is removed for the second time. Then, a preheated stirring paddle is placed in the alloy liquid and placed in the middle and lower part of the alloy liquid. The stirring device is started for mechanical stirring for 3-5 minutes. Finally, after the alloy liquid forms a stable eddy, remove the SiC preheated in step S6. p Slowly add SiC to the molten alloy, the feeding process lasting 10-15 minutes. p The amount of additive is 2%-10% of the total volume of the alloy liquid. After the addition is completed, the stirring is carried out in stages with variable speed: for the first 5-15 minutes, the stirring speed is 300-350 rpm, and for the last 15-25 minutes, the stirring speed is 400-500 rpm. S7. Reheat the melting furnace to 710-720℃, stirring continuously during the reheating process. When the temperature reaches the target temperature, keep it heated while stirring for 10-15 minutes to carry out dispersion treatment. Then, put the Mg-30Gd master alloy and Mg-30Y master alloy prepared in step S2 into the alloy liquid. After the solid alloy melts, start the stirring device again for mechanical stirring. S8. First, preheat the casting mold to 380-420℃; then, remove the oxide layer generated on the surface of the alloy liquid prepared in step S7 three times, pour the alloy liquid into the mold for die casting, with a pressure of 400-500kN and a holding time of 150-200s; finally, after the holding time is completed, remove the mold and air cool it to room temperature to obtain a cast corrosion-resistant rare earth magnesium-based composite material ingot.

2. The method for preparing a cast corrosion-resistant rare earth magnesium-based composite material according to claim 1, characterized in that, In step S1, SiC p Preprocessing includes the following steps: S1-1, First, SiC p Wash the SiC with deionized water 3-5 times. p After removal, add 5-10 wt.% HF solution for acid washing, stir thoroughly and let stand for at least 5 minutes; S1-2, Rinse the acid-washed SiC again with deionized water. p Continue this process until the pH of the washing solution reaches 6.5-7.5; S1-3, the cleaned SiC p Lay it flat on a tray lined with aluminum foil and dry it at 80-100℃ until constant weight, with a drying time of not less than 24 hours; S1-4, the dried SiC p The SiC was uniformly dispersed in an ultrasonic vibrating sieve and passed through a sieve with a 10 μm aperture. p Pretreated SiC was obtained by sealing and storing it. p .

3. The method for preparing a cast corrosion-resistant rare earth magnesium-based composite material according to claim 1, characterized in that, In step S2, the purity of the magnesium block is ≥99.9%, the purity of the zinc granules is ≥99.9%, the purity of the Mg-30Gd master alloy is ≥99.9%, and the purity of the Mg-30Y master alloy is ≥99.9%.

4. The method for preparing a cast corrosion-resistant rare earth magnesium-based composite material according to claim 1, characterized in that, In step S3, the high-temperature resistant coating agent is composed of talc powder coating and zinc oxide coating. The composition and ratio of the talc powder coating are: 80g talc powder, 20g water glass and 250ml water; the ratio of the zinc oxide coating is: 45g zinc oxide, 45g water glass and 250ml water.

5. The method for preparing a cast corrosion-resistant rare earth magnesium-based composite material according to claim 1, characterized in that, In step S4, the protective atmosphere is a mixture of CO2 and SF6, with a volume ratio of CO2 to SF6 of 99:1.

Images