A high electromagnetic shielding magnesium-lithium alloy ingot and its preparation method

Abstract

This invention discloses a high electromagnetic shielding magnesium-lithium alloy ingot, composed of the following mass percentages: Li 5.0%~11.7%, Zn 5.5%~6.5%, Y 1.5%~2.5%, Ag 0~0.5%, with the remainder being Mg and unavoidable impurities. The preparation method is as follows: 1. Selecting raw materials; 2. Adding materials; 3. Vacuuming; 4. Heating to melt the raw materials and then casting to obtain the magnesium-lithium alloy ingot. In this invention, the addition of Zn, Y, and Ag elements is controlled to introduce multi-scale precipitates that exert a synergistic strengthening effect, improving the strength, toughness, and electromagnetic shielding performance of the magnesium-lithium alloy. Furthermore, grain refinement and reduction of solid solution elements improve the alloy's conductivity, optimizing its electromagnetic shielding performance. This invention achieves precise control of the compositional deviation and grain size of the magnesium-lithium alloy ingot through strict control of each melting stage, resulting in a magnesium-lithium alloy ingot suitable for precision electronic components.

Description

Technical Field

[0001] This invention belongs to the field of functional structure integrated material preparation technology, specifically relating to a high electromagnetic shielding magnesium-lithium alloy ingot and its preparation method. Background Technology

[0002] Magnesium-lithium alloy (Mg-Li alloy) is one of the lightest metallic structural materials currently available, with a density typically around 1.3 g / cm³. 3 ~1.6g / cm 3 Between these values, the levels are far lower than those of aluminum alloys (2.7g / cm³). 3 Furthermore, with the rapid development of the 5G era, electromagnetic radiation pollution has become an increasingly serious problem. In addition to excellent room temperature and high temperature mechanical properties, some components used in aerospace and defense industries also need to have excellent electromagnetic shielding effects to prevent electromagnetic leakage or the entry of electromagnetic waves.

[0003] Currently, high electromagnetic shielding magnesium alloys mainly rely on the second phase within the alloy to increase the multiple reflection losses of incident electromagnetic waves, thereby improving shielding performance. However, the addition of alloying elements often leads to a decrease in the material's conductivity, thus limiting further improvements in its electromagnetic shielding performance. Therefore, it is necessary to develop novel magnesium-lithium alloys that improve both their room-temperature mechanical properties and conductivity, thereby further enhancing their electromagnetic shielding effectiveness and promoting the application of magnesium alloys in a wider range of industrial fields. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a high electromagnetic shielding magnesium-lithium alloy ingot. By controlling the addition amounts of Zn, Y, and Ag elements in this magnesium-lithium alloy ingot, on the one hand, multi-scale precipitates are introduced to exert a synergistic strengthening effect, improving the strength, toughness, and electromagnetic shielding performance of the magnesium-lithium alloy; on the other hand, grain refinement and reduction of solid solution elements improve the alloy's conductivity, optimizing the alloy's electromagnetic shielding performance. This solves the problem that the conductivity of magnesium-lithium alloys is a limiting factor for electromagnetic shielding performance after the addition of alloying elements.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a high electromagnetic shielding magnesium-lithium alloy ingot, characterized in that it is composed of the following components by mass percentage: Li 5.0%~11.7%, Zn 5.5%~6.5%, Y 1.5%~2.5%, Ag 0~0.5%, with the remainder being Mg element and unavoidable impurities. The above-mentioned high electromagnetic shielding magnesium-lithium alloy ingot is characterized by being composed of the following components by mass percentage: Li 5.0%~11.0%, Zn 5.5%~6.5%, Y 1.5%~2.0%, Ag 0~0.5%, with the remainder being Mg and unavoidable impurities. Meanwhile, the present invention also discloses a method for preparing the high electromagnetic shielding magnesium-lithium alloy ingot as described above, characterized in that the method includes the following steps: Step 1: Based on the composition of the target product, magnesium-lithium alloy ingot, select Mg ingot, Li ingot, Zn segment, Ag granules and Mg-30Y master alloy as raw materials. Among them, Li ingot is vacuum-sealed in aluminum bag to avoid oxidation. Step 2: Preheat the casting mold and place it in a vacuum induction melting furnace. Then, put the raw materials into the crucible and the feeding trough. Step 3: Close the furnace door of the vacuum induction melting furnace, and then evacuate the furnace. Step 4: Adjust the power of the vacuum induction melting furnace until the temperature rises to 720℃~750℃, so that the Mg ingots and Li ingots placed in the crucible melt. Then, add Zn segments, Ag particles and Mg-30Y master alloy in sequence through the feeding tank. After all the raw materials have melted, mechanically stir and keep warm, and then cast to obtain magnesium-lithium alloy ingots.

[0006] The above method is characterized in that the preheating temperature of the casting mold in step two is not lower than 300°C, and the time is not lower than 30 minutes. This invention controls the preheating temperature and time of the casting mold to prevent insufficient feeding during solidification after casting, which could lead to excessive riser depth and increased waste.

[0007] The above method is characterized in that, in step three, the vacuum level inside the furnace before melting is 2 × 10⁻⁶. -2 Pa ~ 6×10 -2 Pa. This invention employs a higher vacuum level to reduce the introduction of impurity elements, ensuring uniform microstructure and composition of the cast ingot, and improving the quality of magnesium-lithium alloy ingots.

[0008] The method described above is characterized in that the mechanical stirring time in step four is 10-20 minutes, and the holding time is 5-10 minutes. This invention uses mechanical stirring to improve the compositional uniformity of the ingot and reduce component segregation; simultaneously, it increases the fluidity of the molten metal obtained during holding, thus avoiding defects.

[0009] Compared with the prior art, the present invention has the following advantages: 1. This invention, through compositional design, adds a certain amount of Zn, Y, and Ag elements to magnesium-lithium alloy ingots. On the one hand, it regulates the content and size of multi-scale alloy phases, including increasing the volume fraction of the β-Li phase and inducing the precipitation of the Mg3Zn3Y2 micron eutectic phase and the MgLiZn nano-dispersed phase. The synergistic effect of the multi-scale alloy phases enhances the electromagnetic wave multiple reflection and dislocation pinning capabilities, thereby improving the strength, toughness, and electromagnetic shielding performance of the magnesium-lithium alloy. On the other hand, it utilizes the interaction of multiple elements to refine the grains and reduce solid solution elements, improving the alloy's conductivity and further optimizing its electromagnetic shielding performance, making it suitable for different scenarios.

[0010] 2. Unlike conventional magnesium-lithium alloy smelting, which often results in severe component segregation and burn-off due to layering materials based on melting points, this invention uses a vacuum induction melting furnace for vacuum casting. By adding a feeding device, materials are added in stages, i.e., Mg / Li is melted first, followed by Zn / Ag / Y. Combined with mechanical stirring and other processes, material loss is reduced and material uniformity is improved. The process is simple and easy to popularize, has the potential for large-scale production, and can significantly lower the threshold for industrial application.

[0011] 3. In the preparation process of this invention, by strictly controlling the vacuum degree before melting to reduce inclusions, by preheating the casting mold to improve the ingot riser, and by mechanical stirring and heat preservation to improve the uniformity of the ingot structure, the composition deviation and grain size of the magnesium-lithium alloy ingot are precisely controlled, resulting in magnesium-lithium alloy ingots with a composition deviation of no more than ±0.3wt.% and a grain size of 20μm~50μm, and a yield of more than 87.5%, thus ensuring the stability of the quality of the magnesium-lithium alloy ingot.

[0012] 4. The magnesium-lithium alloy ingot prepared by this invention has a smooth and flat surface without obvious defects. At the same time, the fine grains are evenly distributed, and the strength and toughness are balanced. Its tensile strength reaches 180MPa~219MPa, and the shielding effectiveness (SE) is stable at ≥95dB in a wide frequency band of 30MHz~1500MHz, which is more than 35% higher than that of traditional magnesium alloys (SE<70dB). The conductivity is also improved by more than 12%, breaking through the industry bottleneck of conductivity restricting shielding performance. It is suitable for processing precision electronic components.

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0014] Figure 1 The image shows the metallographic structure of the Mg-7.65Li-5.95Zn-1.82Y-0.5Ag alloy ingot prepared in Example 1 of this invention.

[0015] Figure 2This is a TEM image of the Mg-7.65Li-5.95Zn-1.82Y-0.5Ag alloy ingot prepared in Example 1 of this invention.

[0016] Figure 3 The image shows the fracture morphology of the Mg-7.65Li-5.95Zn-1.82Y-0.5Ag alloy ingot prepared in Example 1 of this invention. Detailed Implementation

[0017] Example 1 The high electromagnetic shielding magnesium-lithium alloy ingot of this embodiment is composed of the following components by mass percentage: Li 7.65%, Zn 5.95%, Y 1.82%, Ag 0.50%, with the remainder being Mg and unavoidable impurities. The preparation method of the high electromagnetic shielding magnesium-lithium alloy ingot in this embodiment includes the following steps: Step 1: Based on the composition of the target product, magnesium-lithium alloy ingot, select Mg ingot, Li ingot, Zn segment, Ag granules and Mg-30Y master alloy as raw materials. The total weight of the raw materials is 4kg. Among them, Li ingot is vacuum-sealed in aluminum bags to avoid oxidation. Step 2: Preheat the casting mold to 350℃ for 30 minutes, and then place it in a vacuum induction melting furnace. Then, put the Mg ingots and Li ingots from the raw materials into the crucible, and put the Zn segments, Ag particles and Mg-30Y master alloy into different feeding tanks. Step 3: Close the furnace door of the vacuum induction melting furnace, and then evacuate the furnace until the pre-melting vacuum level is 2×10⁻⁶. -2 Pa; Step 4: Adjust the power of the vacuum induction melting furnace until the temperature reaches 740℃, so that the Mg ingot and Li ingot placed in the crucible melt. Then, add Zn segments, Ag particles and Mg-30Y master alloy in sequence through the feeding tank. After all the raw materials have melted, perform full-speed mechanical stirring for 20 minutes and hold for 5 minutes. Then, cast the mixture to obtain magnesium-lithium alloy ingots.

[0018] Figure 1 The image shows the metallographic structure of the Mg-7.65Li-5.95Zn-1.82Y-0.5Ag alloy ingot prepared in this embodiment. Figure 1 It can be seen that the metallographic structure of the ingot contains both light-colored α-Mg and gray β-Li matrix phases. The matrix also contains a eutectic second phase and coarse grain phases, while fine primary grain phases are distributed along the phase boundaries of the matrix phase. Due to the addition of Ag, the α-Mg phase is significantly refined and spheroidized, with an average size of 43 μm. The average grain size of the β-Li phase is refined to 14.19 μm.

[0019] Figure 2The image shown is a TEM microstructure of the Mg-7.65Li-5.95Zn-1.82Y-0.5Ag alloy ingot prepared in this embodiment. Figure 2 It can be seen that the second phase in the ingot is mainly distributed in the β-Li phase. In addition to the submicron-scale bulk phase, a large number of dispersed nanoscale particles were also observed in the matrix. The synergistic effect of the two can effectively improve the mechanical and electromagnetic properties of the material.

[0020] Figure 3 The image shows the fracture morphology of the Mg-7.65Li-5.95Zn-1.82Y-0.5Ag alloy ingot prepared in this embodiment. Figure 3 It can be seen that the fracture surface of the ingot shows a large number of dimples and a small number of tear ridges, which belongs to quasi-cleavage fracture. This indicates that the addition of Ag element will lead to a decrease in the plasticity of the material. Example 2 The high electromagnetic shielding magnesium-lithium alloy ingot of this embodiment is composed of the following components by mass percentage: Li 5.0%, Zn 6.03%, Y 1.50%, with the remainder being Mg and unavoidable impurities. The preparation method of the high electromagnetic shielding magnesium-lithium alloy ingot in this embodiment includes the following steps: Step 1: Based on the composition of the target product, magnesium-lithium alloy ingot, select Mg ingot, Li ingot, Zn segment and Mg-30Y master alloy as raw materials. The total weight of the raw materials is 4.5 kg. Among them, Li ingot is vacuum-sealed in aluminum bag to avoid oxidation. Step 2: Preheat the casting mold to 350℃ for 45 minutes, and then place it in a vacuum induction melting furnace. Then, put the Mg ingot and Li ingot from the raw materials into the crucible, and put the Zn segment and Mg-30Y master alloy into different feeding tanks. Step 3: Close the furnace door of the vacuum induction melting furnace, and then evacuate the furnace until the pre-melting vacuum level is 2.3 × 10⁻⁶. -2 Pa; Step 4: Adjust the power of the vacuum induction melting furnace until the temperature reaches 750℃, so that the Mg ingot and Li ingot placed in the crucible melt. Then, add Zn segment and Mg-30Y master alloy in sequence through the feeding tank. After all the raw materials have melted, perform full-speed mechanical stirring for 15 minutes and hold for 5 minutes. Then, cast the mixture to obtain magnesium-lithium alloy ingots.

[0021] Example 3 The high electromagnetic shielding magnesium-lithium alloy ingot of this embodiment is composed of the following components by mass percentage: Li 8.62%, Zn 6.50%, Y 1.89%, with the remainder being Mg and unavoidable impurities. The preparation method of the high electromagnetic shielding magnesium-lithium alloy ingot in this embodiment includes the following steps: Step 1: Based on the composition of the target product, magnesium-lithium alloy ingot, select Mg ingot, Li ingot, Zn segment and Mg-30Y master alloy as raw materials. The total weight of the raw materials is 4kg. Among them, Li ingot is vacuum-sealed in aluminum bag to avoid oxidation. Step 2: Preheat the casting mold to 350℃ for 30 minutes, and then place it in a vacuum induction melting furnace. Then, put the Mg ingot and Li ingot from the raw materials into the crucible, and put the Zn segment and Mg-30Y master alloy into different feeding tanks. Step 3: Close the furnace door of the vacuum induction melting furnace, and then evacuate the furnace until the pre-melting vacuum level is 6×10⁻⁶. -2 Pa; Step 4: Adjust the power of the vacuum induction melting furnace until the temperature reaches 740℃, so that the Mg ingot and Li ingot placed in the crucible melt. Then, add Zn segment and Mg-30Y master alloy in sequence through the feeding tank. After all the raw materials have melted, perform full-speed mechanical stirring for 15 minutes and hold for 10 minutes. Then, cast the mixture to obtain magnesium-lithium alloy ingots.

[0022] Example 4 The high electromagnetic shielding magnesium-lithium alloy ingot of this embodiment is composed of the following components by mass percentage: Li 11.7%, Zn 5.5%, Y 2.50%, with the remainder being Mg and unavoidable impurities. The preparation method of the high electromagnetic shielding magnesium-lithium alloy ingot in this embodiment includes the following steps: Step 1: Based on the composition of the target product, magnesium-lithium alloy ingot, select Mg ingot, Li ingot, Zn segment and Mg-30Y master alloy as raw materials. The total weight of the raw materials is 3kg. Among them, Li ingot is vacuum-sealed in aluminum bag to avoid oxidation. Step 2: Preheat the casting mold to 300℃ for 30 minutes, and then place it in a vacuum induction melting furnace. Then, put the Mg ingot and Li ingot from the raw materials into the crucible, and put the Zn segment and Mg-30Y master alloy into different feeding tanks. Step 3: Close the furnace door of the vacuum induction melting furnace, and then evacuate the furnace until the pre-melting vacuum level is 2.1 × 10⁻⁶. -2 Pa; Step 4: Adjust the power of the vacuum induction melting furnace until the temperature reaches 720℃, so that the Mg ingot and Li ingot placed in the crucible melt. Then, add Zn segment and Mg-30Y master alloy in sequence through the feeding tank. After all the raw materials have melted, perform full-speed mechanical stirring for 10 minutes and hold for 5 minutes. Then, cast the mixture to obtain magnesium-lithium alloy ingots.

[0023] The mechanical and electromagnetic properties of the magnesium-lithium alloy ingots prepared in Examples 1-4 of this invention and the commonly used commercial LZ91 alloy were tested, and the results are shown in Table 1.

[0024] Table 1

[0025] As can be seen from Table 1, compared with the commonly used magnesium-lithium alloy, namely the commercial LZ91 alloy, the magnesium-lithium alloy ingots prepared in Examples 1 to 4 of this invention have excellent mechanical properties, with a stable shielding effectiveness (SE) of ≥95dB in a wide frequency band of 30MHz to 1500MHz, and improved conductivity, breaking through the industry bottleneck of conductivity restricting shielding performance.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A high electromagnetic shielding magnesium-lithium alloy ingot, characterized in that, It consists of the following components by mass percentage: Li 5.0%~11.7%, Zn 5.5%~6.5%, Y 1.5%~2.5%, Ag 0~0.5%, with the remainder being Mg and unavoidable impurities.

2. The high electromagnetic shielding magnesium-lithium alloy ingot according to claim 1, characterized in that, It consists of the following components by mass percentage: Li 5.0%~11.0%, Zn 5.5%~6.5%, Y 1.5%~2.0%, Ag 0~0.5%, with the remainder being Mg and unavoidable impurities.

3. A method for preparing a high electromagnetic shielding magnesium-lithium alloy ingot as described in claim 1 or 2, characterized in that, The method includes the following steps: Step 1: Based on the composition of the target product, magnesium-lithium alloy ingot, select Mg ingot, Li ingot, Zn segment, Ag granules and Mg-30Y master alloy as raw materials. Among them, Li ingot is vacuum-sealed in aluminum bag to avoid oxidation. Step 2: Preheat the casting mold and place it in a vacuum induction melting furnace. Then, put the raw materials into the crucible and the feeding trough. Step 3: Close the furnace door of the vacuum induction melting furnace, and then evacuate the furnace. Step 4: Adjust the power of the vacuum induction melting furnace until the temperature rises to 720℃~750℃, so that the Mg ingots and Li ingots placed in the crucible melt. Then, add Zn segments, Ag particles and Mg-30Y master alloy in sequence through the feeding tank. After all the raw materials have melted, mechanically stir and keep warm, and then cast to obtain magnesium-lithium alloy ingots.

4. The method according to claim 3, characterized in that, In step two, the preheating temperature of the casting mold shall not be lower than 300℃ and the time shall not be lower than 30 minutes.

5. The method according to claim 3, characterized in that, In step three, the vacuum level inside the furnace before melting is 2 × 10⁻⁶. -2 Pa ~ 6×10 -2 Pa.

6. The method according to claim 3, characterized in that, The mechanical stirring time in step four is 10-20 minutes, and the heat preservation time is 5-10 minutes.

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