A rare earth magnesium alloy with high corrosion resistance and a preparation method thereof

Abstract

The application discloses a rare earth magnesium alloy with high corrosion resistance and a preparation method thereof, and relates to the technical field of metal materials. The mass percentage of each raw material component is as follows: Gd: 1-8%; Al: 1.0-1.3%; the balance of Mg and inevitable impurities. The application adds the rare earth element Gd, so that the corrosion resistance of the magnesium alloy in a 3.5 wt.% sodium chloride solution is improved, and the corrosion resistance of the magnesium alloy is further improved in combination with a solid solution heat treatment process. When the addition amount of Gd reaches 8%, the polarization resistance of the electrochemical impedance spectrum reaches 2400 ohm*cm2, which is much higher than the polarization resistance (about 800 ohm*cm2) of a conventional magnesium alloy.

Description

Technical Field

[0001] This invention discloses a rare earth magnesium alloy with high corrosion resistance and its preparation method, which relates to the field of metal materials technology. Background Technology

[0002] To address the poor corrosion resistance of magnesium alloys, rare earth elements can be added. These elements reduce the interphase potential difference in magnesium alloys, inhibiting microgalvanic corrosion. Furthermore, they enhance the stability of the corrosion product film, further improving the corrosion resistance. Previous reports have shown that alloying magnesium alloys with yttrium (Y) and al (Al) can significantly improve their corrosion resistance. However, due to the high chemical reactivity of yttrium (Y), it readily combines with oxygen atoms during Mg-Y-Al alloy preparation, forming oxide inclusions that drastically reduce the purity of the magnesium alloy and severely limit its practical application. Summary of the Invention

[0003] This invention aims to address the problems of poor corrosion resistance in traditional magnesium alloys and the tendency of existing rare-earth magnesium alloys to generate oxide inclusions, resulting in poor overall mechanical and corrosion resistance properties of magnesium alloy materials. Yttrium (Y) is chemically reactive and more easily oxidized to Y₂O₃ during smelting than elements commonly found in magnesium alloys such as Al and Zn, forming oxide inclusions. These oxide inclusions prevent castings from achieving Class I casting quality, and for profiles, significantly reduce their ultrasonic testing grade. This leads to numerous technical bottlenecks in the engineering application of Y-containing magnesium alloys, making stable mass production difficult. This invention provides a rare-earth magnesium alloy with high corrosion resistance and its preparation method. This invention uses gadolinium (Gd) instead of Y, effectively avoiding the formation of large amounts of oxide inclusions. Furthermore, since Gd also has a significant strengthening effect, it can improve the mechanical properties of the magnesium alloy while ensuring its processing performance, achieving a dual improvement in mechanical strength and mechanical properties.

[0004] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: A rare earth magnesium alloy with high corrosion resistance, wherein the mass percentage of each raw material component is as follows: Gd: 1%~8%; Al: 1.0%~1.3%; The balance is Mg and unavoidable impurities.

[0005] Preferred, unavoidable impurities include: Si, Fe, Ni, Cu, and Co.

[0006] Preferably, the Gd content is 7.0% to 7.4%.

[0007] Preferably, the mass percentages of each raw material component are: Gd: 7.2%; Al: 1.2%; with the balance being Mg and unavoidable impurities.

[0008] A method for preparing a rare earth magnesium alloy with high corrosion resistance includes the following steps: Step 1: Weigh out pure magnesium, pure aluminum, and magnesium-gadolinium master alloy according to the mass percentage of the magnesium alloy material; Step 2: Melt pure magnesium. After the pure magnesium melts, add pure aluminum and magnesium gadolinium master alloy and continue melting until all materials melt to obtain a molten liquid. Step 3: Refine the molten liquid and then cast it to obtain an ingot; Step 4: Heat treat the ingot and cool it to room temperature in the furnace to obtain magnesium alloy material; Step 5: Perform solution heat treatment on the magnesium alloy material and quench it with cold water to obtain rare earth magnesium alloy.

[0009] Preferably, in step one, the mass percentage of Gd element in the magnesium-gadolinium master alloy is 30%.

[0010] Preferably, in step two, pure magnesium is melted at a temperature of 650~680℃ for 1.5~2 hours.

[0011] Preferably, the pure aluminum and magnesium gadolinium master alloy is melted at a temperature of 720~750℃ for 30~45 minutes.

[0012] Preferably, in step four, the ingot is kept at a temperature of 480~500℃ for 10~12 hours.

[0013] Preferably, in step five, the solution heat treatment method is to hold the solution at 500~520℃ for 8~12 hours.

[0014] The beneficial effects of this invention are: I. The present invention provides a rare earth magnesium alloy with high corrosion resistance. By adding the rare earth element Gd, the corrosion resistance of the magnesium alloy in 3.5 wt.% sodium chloride solution is improved. Furthermore, the corrosion resistance of the magnesium alloy is further enhanced by the solid solution heat treatment process. When the amount of Gd added reaches 8%, its polarization resistance of electrochemical impedance spectroscopy reaches 2400 ohm·cm², which is much higher than the polarization resistance of conventional magnesium alloys (approximately 800 ohm·cm²).

[0015] II. The present invention provides a rare earth magnesium alloy with high corrosion resistance. By utilizing the high activity of rare earth element Gd, the microgalvanic corrosion of magnesium alloy is effectively reduced, and the formation of a protective film on the surface of magnesium alloy is promoted, thus realizing the preparation of a high corrosion-resistant magnesium alloy.

[0016] III. The present invention provides a rare earth magnesium alloy with high corrosion resistance and its preparation method. The cost of Gd element is lower than that of Y element, and its addition amount (1-8%) can achieve performance optimization, which significantly reduces material cost compared with traditional Mg-Y-Al alloy.

[0017] IV. The present invention provides a rare earth magnesium alloy with high corrosion resistance and its preparation method. The high corrosion resistance (polarization resistance up to 2400 ohm·cm²) and mechanical properties of this alloy make it suitable for corrosive environments such as marine and chemical industries, and meet the production needs of corrosion-resistant and lightweight components in the aerospace field. Attached Figure Description

[0018] Figure 1 These are the electrochemical impedance spectra of cast magnesium alloys with different Gd contents in this invention. Figure 2 These are the electrochemical impedance spectra of magnesium alloys with different Gd contents after solution heat treatment in this invention. Figure 3 These are the electrochemical impedance spectra of magnesium alloys with different Gd contents after aging heat treatment in this invention. Figure 4 This is the potentiodynamic polarization curve of Mg-Gd-Al-T4 magnesium alloy with a Gd content of 7.2% in this invention in a 3.5wt% sodium chloride solution. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0020] Example 1 A rare earth magnesium alloy with high corrosion resistance, wherein the mass percentage of each raw material component is as follows: Gd: 7.2%; Al: 1.2%; The balance is Mg and unavoidable impurities.

[0021] Unavoidable impurities include Si, Fe, Ni, Cu, and Co. These elements mainly originate from primary magnesium, smelting crucibles, and casting copper molds and crystallizers.

[0022] A method for preparing a rare earth magnesium alloy with high corrosion resistance includes the following steps: Step 1: Weigh out pure magnesium, pure aluminum, and magnesium-gadolinium master alloy according to the mass percentage of the magnesium alloy material; Step 2: Melt pure magnesium. After the pure magnesium melts, add pure aluminum and magnesium gadolinium master alloy and continue melting until all materials melt to obtain a molten liquid. Step 3: Refine the molten liquid and then cast it to obtain an ingot; Step 4: Heat treat the ingot and cool it to room temperature in the furnace to obtain magnesium alloy material; Step 5: Perform solution heat treatment on the magnesium alloy material and quench it with cold water to obtain rare earth magnesium alloy.

[0023] In step one, the mass percentage of Gd in the magnesium-gadolinium master alloy is 30%.

[0024] In step two, pure magnesium is melted at a temperature of 650-680°C for 1.5-2 hours; pure aluminum and gadolinium master alloy is melted at a temperature of 720-750°C for 30-45 minutes.

[0025] In step four, the ingot is held at a temperature of 480-500℃ for 10-12 hours.

[0026] In step five, the solution heat treatment method involves holding the solution at 500-520°C for 8-12 hours.

[0027] The polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reached 2460 ohm·cm².

[0028] Example 2 In this embodiment, a rare earth magnesium alloy with high corrosion resistance is described, and the mass percentage of each raw material component is as follows: Gd: 1%; Al: 1.3%; The balance is Mg and unavoidable impurities.

[0029] Unavoidable impurities include Si, Fe, Ni, Cu, and Co. These elements mainly originate from primary magnesium, smelting crucibles, and casting copper molds and crystallizers.

[0030] A method for preparing a rare earth magnesium alloy with high corrosion resistance is described in Example 1.

[0031] The polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reached 223 ohms·cm².

[0032] Example 3 In this embodiment, a rare earth magnesium alloy with high corrosion resistance is described, and the mass percentage of each raw material component is as follows: Gd: 8%; Al: 1%; The balance is Mg and unavoidable impurities.

[0033] Unavoidable impurities include Si, Fe, Ni, Cu, and Co. These elements mainly originate from primary magnesium, smelting crucibles, and casting copper molds and crystallizers.

[0034] A method for preparing a rare earth magnesium alloy with high corrosion resistance is described in Example 1.

[0035] The polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reached 2410 ohm·cm².

[0036] Example 4 In this embodiment, a rare earth magnesium alloy with high corrosion resistance is described, and the mass percentage of each raw material component is as follows: Gd: 7.0%; Al: 1.2%; The balance is Mg and unavoidable impurities.

[0037] Unavoidable impurities include Si, Fe, Ni, Cu, and Co. These elements mainly originate from primary magnesium, smelting crucibles, and casting copper molds and crystallizers.

[0038] A method for preparing a rare earth magnesium alloy with high corrosion resistance is described in Example 1.

[0039] The polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reached 2408 ohms·cm².

[0040] Example 5 In this embodiment, a rare earth magnesium alloy with high corrosion resistance is described, and the mass percentage of each raw material component is as follows: Gd: 7.4%; Al: 1.2%; The balance is Mg and unavoidable impurities.

[0041] Unavoidable impurities include Si, Fe, Ni, Cu, and Co. These elements mainly originate from primary magnesium, smelting crucibles, and casting copper molds and crystallizers.

[0042] A method for preparing a rare earth magnesium alloy with high corrosion resistance is described in Example 1.

[0043] The polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reached 2480 ohm·cm².

[0044] Experimental Example 1 The difference between this experimental example and the embodiment is that the Gd content is 1.7%, 3.5%, and 7.2%, respectively.

[0045] like Figure 1The electrochemical impedance spectroscopy (EIS) spectra of magnesium alloys with different Gd contents in 3.5 wt% sodium chloride solution are shown. All three samples were as-cast and had not undergone subsequent heat treatment. The blue, red, and magenta data represent Gd contents of 1.7%, 3.5%, and 7.2%, respectively, while the Al content remained at 1.2%. It can be seen that the corrosion resistance of Mg-Gd-Al magnesium alloys gradually decreases with increasing Gd content.

[0046] like Figure 2 The electrochemical impedance spectroscopy (EIS) spectra of magnesium alloys with different Gd contents in 3.5 wt% sodium chloride solution are shown. All three samples underwent solution heat treatment. The blue, red, and magenta data represent Gd contents of 1.7%, 3.5%, and 7.2%, respectively, while the Al content remained at 1.2%. It can be seen that the corrosion resistance of the Mg-Gd-Al magnesium alloy first decreases and then increases with increasing Gd content, exhibiting the highest corrosion resistance at a Gd content of 7.2%.

[0047] like Figure 3 As shown, the electrochemical impedance spectroscopy (EIS) spectra of magnesium alloys with different Gd contents in 3.5 wt% sodium chloride solution are presented. All three samples underwent aging heat treatment. The blue, red, and magenta data correspond to Gd contents of 1.7%, 3.5%, and 7.2%, respectively, while the Al content remained at 1.2%. It can be seen that the corrosion resistance of the Mg-Gd-Al magnesium alloy exhibits a trend of first decreasing and then increasing with increasing Gd content, reaching its highest resistance at a Gd content of 7.2%. Furthermore, the polarization resistance of the samples after aging heat treatment is lower than that after solution heat treatment. Based on these results, it can be concluded that the Mg-Gd-Al magnesium alloy exhibits the best corrosion resistance with a Gd content ≥7%, and the optimal heat treatment process is solution heat treatment. Further aging heat treatment would actually reduce its corrosion resistance.

[0048] like Figure 4 As shown, the polarization curve of Mg-7.2Gd-Al magnesium alloy after solution heat treatment in sodium chloride solution shows that its corrosion current density is about 15 μA / cm², which is much lower than the corrosion current density of traditional magnesium alloys (≥100 μA / cm²).

[0049] Comparative Example 1 The difference between this comparative example and Example 1 is that Al: 0.8%; the polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reaches 2211 ohms·cm².

[0050] Comparative Example 2 The difference between this comparative example and Example 1 is that Al: 1.5%; the polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reaches 2348 ohms·cm².

[0051] Comparative Example 3 The difference between this comparative example and Example 1 is that: Gd: 0.8%; the polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reaches 210 ohm·cm².

[0052] Comparative Example 4 The difference between this comparative example and Example 1 is that: Gd: 8.2%; the polarization resistance of the electrochemical impedance spectroscopy of the prepared rare earth magnesium alloy reaches 2156 ohms·cm².

[0053] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A rare earth magnesium alloy with high corrosion resistance, characterized in that: The mass percentage of each raw material component is as follows: Gd: 1%~8%; Al：1.0%~1.3%； The balance is Mg and unavoidable impurities.

2. The rare earth magnesium alloy with high corrosion resistance according to claim 1, characterized in that: Unavoidable impurities include: Si, Fe, Ni, Cu, and Co.

3. A rare earth magnesium alloy with high corrosion resistance according to claim 1, characterized in that: The Gd content is 7.0%~7.4%.

4. A rare earth magnesium alloy with high corrosion resistance according to claim 1, characterized in that: The mass percentage of each raw material component is as follows: Gd: 7.2%; Al: 1.2%; balance Mg and unavoidable impurities.

5. A method for preparing a rare earth magnesium alloy with high corrosion resistance according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: Weigh out pure magnesium, pure aluminum, and magnesium-gadolinium master alloy according to the mass percentage of the magnesium alloy material; Step 2: Melt pure magnesium. After the pure magnesium melts, add pure aluminum and magnesium gadolinium master alloy and continue melting until all materials melt to obtain a molten liquid. Step 3: Refine the molten liquid and then cast it to obtain an ingot; Step 4: Heat treat the ingot and cool it to room temperature in the furnace to obtain magnesium alloy material; Step 5: Perform solution heat treatment on the magnesium alloy material and quench it with cold water to obtain rare earth magnesium alloy.

6. The method for preparing a rare earth magnesium alloy with high corrosion resistance according to claim 5, characterized in that: In step one, the mass percentage of Gd element in the magnesium gadolinium master alloy is 30%.

7. The method for preparing a rare earth magnesium alloy with high corrosion resistance according to claim 6, characterized in that: In step two, pure magnesium is melted at a temperature of 650~680℃ for 1.5~2 hours.

8. The method for preparing a rare earth magnesium alloy with high corrosion resistance according to claim 7, characterized in that: In step two, the pure aluminum and magnesium gadolinium master alloy is melted at a temperature of 720~750℃ for 30~45 minutes.

9. The method for preparing a rare earth magnesium alloy with high corrosion resistance according to claim 8, characterized in that: In step four, the ingot is held at a temperature of 480~500℃ for 10~12 hours.

10. The method for preparing a rare earth magnesium alloy with high corrosion resistance according to claim 9, characterized in that: In step five, the solution heat treatment method involves holding the solution at 500-520℃ for 8-12 hours.

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