A high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot and its preparation method

Abstract

The present invention discloses a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot and a preparation method thereof, belonging to the technical field of metallic materials. By mass percentage, the magnesium-lithium alloy ingot comprises the following components: Li element: 1-5.7 wt%; Al element: 1-6 wt%; Mn element: 0.2-0.6 wt%; Ce element: 0.02-0.07 wt%; the balance being Mg element and inevitable impurities. By controlling the Li element in the magnesium-lithium alloy ingot not to exceed 5.7 wt% and specific contents of Al element, Ce element and Mn element, the mechanical properties, thermal stability and corrosion resistance of the magnesium-lithium alloy are significantly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and particularly relates to a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot and a preparation method thereof. Background Art

[0002] The density of magnesium-lithium alloy is 1.35 - 1.65 g / cm 3 , which is the lightest ultra-light metal structural material at present. Compared with conventional magnesium alloys, in addition to lower density, magnesium-lithium alloy also has excellent electromagnetic shielding property, damping and shock absorption property, as well as excellent weldability, impact resistance and better processing performance, and has great application demands in lightweight fields such as aerospace, weaponry, 3C electronic products, unmanned aerial vehicles, exoskeletons, etc. However, existing magnesium-lithium alloys have problems such as few alloy grades, low absolute strength, poor corrosion resistance and thermal stability, and high price, which limit their wide application.

[0003] Alloying is an effective method to improve the comprehensive properties of magnesium-lithium alloys at present. The commonly used alloying elements include Al, Mn, Zr, RE, etc. The traditional alloying method is to add these alloying elements separately into the magnesium-lithium alloy at a certain content. The current research on as-cast α-Mg-based magnesium-lithium alloys (≤5.7 wt.% Li) is as follows: Since magnesium-lithium alloys burn severely during melting, most magnesium-lithium alloys are melted by vacuum induction melting during melting. For example, the yield strength of the as-cast Mg-4Li-3Al-2Zn-0.5Y alloy prepared by Peng et al. using vacuum induction melting is 115.3 MPa, the tensile strength is 184.3 MPa, the elongation is 4.4%, and the hardness is 62.3 HV (Transactions of Nonferrous Metals Society of China, 2022, 32: 838-849). The yield strength of the Mg-4Li-1Ca alloy prepared by S.S. Nene et al. using an intermediate frequency vacuum induction furnace is 70.6 MPa, the tensile strength is 123.6 MPa, and the hardness is 58 HV (Journal of Alloys and Compounds, 2014, 615: 501-506). The yield strength of the as-cast LATY3221 alloy prepared by Guo et al. using vacuum induction melting is 76±4 MPa, the tensile strength is 166±5 MPa, and the hardness is about 45 HV (Nonferrous Metal Materials and Engineering, 2023, 44(02): 59-66). A small number of magnesium-lithium alloys are prepared by gas-protected resistance furnace melting. For example, the yield strength of the as-cast Mg-2.76Li-3Al-2.6Zn-0.39Y alloy prepared by Sun is 123±4 MPa, and the tensile strength is 189±6 MPa (DOI: 10.27007 / d.cnki.gdbeu.2020.000489). The yield strength of the as-cast Mg-4Li-3Al alloy prepared by Deng Hongju using an SF6+CO2 gas-protected resistance pit furnace is less than 70 MPa, and the tensile strength is 178 MPa (DOI: 10.27670 / d.cnki.gcqdu.2021.001013). It can be seen that the yield strength, tensile strength, and hardness of the as-cast magnesium-lithium alloys prepared by the existing technology are relatively low, and the problems of poor heat resistance and corrosion resistance have not been solved simultaneously, which cannot meet the performance requirements of engineering components for high-performance magnesium-lithium alloy castings. At the same time, the equipment required to prepare magnesium-lithium alloys by the vacuum induction melting method is expensive, the process is complex, and the manufacturing cost is high; while the protective gas SF6+CO2 can inhibit the oxidation and combustion of Li, but the environmental pollution is serious. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot and its preparation method, which are used to overcome the problems of low strength, poor heat and corrosion resistance, and high preparation cost of magnesium-lithium alloys in the prior art.

[0005] In the first aspect, the present invention provides a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot. By mass percentage, the magnesium-lithium alloy ingot includes the following components: Li element: 1-5.7 wt%; Al element: 1-6 wt%; Mn element: 0.2-0.6 wt%; Ce element: 0.02-0.07 wt%; the balance is Mg element and inevitable impurities.

[0006] Compared with the prior art, by controlling the Li element in the magnesium-lithium alloy ingot not to exceed 5.7 wt%, an α-Mg-based magnesium-lithium alloy ingot is obtained. The α-Mg-based magnesium-lithium alloy ingot contains specific contents of Al element, Ce element and Mn element. Among them, the Al element can form second-phase particles such as Mg 17 Al 12 , AlLi, MgLi2Al, etc., improving the mechanical properties of the magnesium-lithium alloy and forming a dense oxide film on the surface to improve the corrosion resistance of the magnesium-lithium alloy; the Ce element can form a small amount of fine needle-like Al 11 Ce3 particles and significantly refine Mg 17 Al 12 , Al6Mn particles and α-Mg grains, increasing the number and uniform dispersion degree of AlLi nanoparticles, which can not only further improve the mechanical properties of the magnesium-lithium alloy, but also improve the thermal stability of the magnesium-lithium alloy; the Mn element can form a solid solution in the α-Mg matrix, thereby improving the strength of the magnesium-lithium alloy and eliminating the impurity iron in the magnesium-lithium alloy, significantly improving the corrosion resistance of the alloy. In addition, when Mn and Ce elements are added simultaneously in a specific ratio, the Ce element can also transform the high-voltage potential Al8Mn5 phase into the low-voltage potential Al8Mn4Ce phase, reducing the potential difference between the second-phase particles and the α-Mg matrix, and effectively improving the corrosion resistance of the α-Mg-based magnesium-lithium alloy.

[0007] Further, by mass percentage, the magnesium-lithium alloy ingot includes the following components: Li element: 4-5.7 wt%; Al element: 3-4.5 wt%; Mn element: 0.3-0.5 wt%; Ce element: 0.05-0.06 wt%; the balance is Mg element and inevitable impurities.

[0008] The above technical solution further limits the contents of each element in the magnesium-lithium alloy ingot. Within the above content range, each element cooperates with each other, which can further improve the mechanical properties, corrosion resistance and thermal stability of the magnesium-lithium alloy ingot.

[0009] Further, the yield strength of the above-mentioned magnesium-lithium alloy ingot is 165-200 MPa, the tensile strength is 240-290 MPa, the hardness is 70-75 HV, the corrosion potential is -1.40 to -1.50 V, and the corrosion current density is 4×10 -5 ~5.5×10 -5 A / cm 2 。

[0010] In a second aspect, the present invention provides a method for preparing a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot for preparing the above-mentioned magnesium-lithium alloy ingot, which comprises the following steps:

[0011] Prepare raw materials in proportion: pure Mg blocks, pure Al blocks, pure Li grains, Mg-Ce master alloy and Al-Mn master alloy.

[0012] At 760-810 °C, sequentially add pure Al blocks, Al-Mn master alloy, and the first covering agent for melting, keep warm, skim the slag, then sequentially add Mg-Ce master alloy and the first covering agent for melting, cool down to 710-740 °C and keep warm, skim the slag, then add the first refining agent and stir, then add the first covering agent, continue to keep warm, skim the slag, and then cast into a water-cooled copper mold for rapid cooling and forming. After cooling, an Al-Mg-Mn-Ce master alloy is obtained.

[0013] At 710-740 °C, sequentially add pure Mg blocks, Al-Mg-Mn-Ce master alloy, and the second covering agent for melting, skim the slag after keeping warm, cool down to 600-620 °C, add the pure Li grains wrapped in aluminum foil and melt them under the liquid surface of the melted alloy, then add the second covering agent, raise the temperature to 700-710 °C and continue to keep warm, skim the slag, then add the second refining agent and stir, then add the second covering agent, skim the slag after keeping warm, and cast and form. After cooling, a magnesium-lithium alloy ingot is obtained.

[0014] Compared with the prior art, the present invention first melts pure Al blocks and Al-Mn master alloy, then adds Mg-Ce master alloy for melting, and then refines, casts, and rapidly cools and forms the obtained molten alloy liquid to obtain an Al-Mg-Mn-Ce master alloy. Then, elements Al, Mn, and Ce are added to the magnesium-lithium alloy together in the form of Al-Mg-Mn-Ce master alloy. The Al-Mg-Mn-Ce master alloy obtained through the above steps consists of an α-Al matrix, uniformly dispersed Al6Mn, (AlMg) 10 Mn2Ce, Al 30The eutectic structure composed of fine particles such as Ce2Mg has a significantly lower melting point than refractory Al-Mn master alloys. This is beneficial for the melting and absorption of high-melting-point Mn elements, significantly reducing the feeding temperature and time, and reducing the oxidation and burning loss during the melting of magnesium-lithium alloys. In particular, the high-melting-point second-phase particles in this Al-Mg-Mn-Ce master alloy play a role in heterogeneous nucleation during the subsequent solidification of the magnesium-lithium alloy. Through the principle of microstructure inheritance, the α-Mg matrix and second-phase particles in the magnesium-lithium alloy can be significantly refined, enabling the magnesium-lithium alloy ingot to also have second-phase particles and α-Mg matrix grains that are fine and evenly dispersed. On the one hand, this can significantly improve the yield strength, tensile strength, and corrosion resistance of the magnesium-lithium alloy ingot. On the other hand, it can also pin the grain boundaries, inhibit grain growth, improve the stability of the magnesium-lithium alloy at high temperatures, and thus improve the high-temperature resistance of the material.

[0015] In addition, compared with the method of using vacuum induction melting to prepare magnesium-lithium alloy ingots in the prior art, the present invention uses the method of ordinary gravity casting to prepare magnesium-lithium alloy ingots, which has low raw material and manufacturing costs, a simple process, and significant economic benefits and potential for practical engineering applications.

[0016] Further, the first covering agent is MgCl2, KCl, and CaF2, and the mass ratio of MgCl2, KCl, and CaF2 is (2~3)∶(2~3)∶1.

[0017] The second covering agent is LiCl and LiF, and the mass ratio of the LiCl and LiF is (3~4)∶1.

[0018] Or, the addition amount of the first covering agent is 3%~4% of the total mass of the raw materials; the addition amount of the second covering agent is 3%~4% of the total mass of the raw materials.

[0019] Each time the first covering agent or the second covering agent is added, an inert gas is introduced for protection.

[0020] In the above technical solution, the composition and ratio of the first covering agent and the second covering agent are further defined. Both of the above two covering agents can form a protective layer on the surface of the molten alloy liquid, effectively preventing the oxidation of the molten metal liquid and avoiding metal burning loss. In addition, the protective gas can prevent the oxidation of the molten metal liquid and ensure the purity of the molten metal liquid.

[0021] The above technical solution also defines the addition amounts of the first covering agent and the second covering agent. Adding the covering agent in the above mass can fully protect the molten metal liquid, prevent its oxidation, and avoid metal burning loss.

[0022] Further, the first refining agent is MgCl2, KCl, and CaF2, and the mass ratio of the MgCl2, KCl, and CaF2 is (2~3)∶(2~3)∶4.

[0023] The second refining agent is LiCl, LiF and CaF2, and the mass ratio of LiCl, LiF and CaF2 is (3 - 4)∶1∶(0.8 - 1).

[0024] In the above technical solution, the composition components and ratios of the first refining agent and the second refining agent are defined. These first and second refining agents can adsorb non-metallic impurities in the molten alloy liquid and remove them during subsequent slag skimming, thereby improving the purity of the molten alloy liquid.

[0025] Furthermore, the addition amount of the first refining agent is 3% - 4% of the total mass of the raw materials; the addition amount of the second refining agent is 4% - 6% of the total mass of the raw materials.

[0026] The above technical solution further defines the addition amounts of the first refining agent and the second refining agent. Adding the refining agents in the above masses can fully remove non-metallic impurities in the molten alloy liquid and ensure the purity of the finally prepared alloy.

[0027] Furthermore, the heat preservation time after melting the pure Al block and the Al-Mn master alloy is 30 - 40 min.

[0028] Add the Mg-Ce master alloy and the first covering agent for melting, and the heat preservation time after cooling is 30 - 40 min.

[0029] When adding the first refining agent and stirring, and then adding the first covering agent for refining, the refining temperature is 710 - 720 °C and the refining time is 15 - 30 min.

[0030] The above technical solution defines the melting heat preservation temperature and time, and the refining temperature and time when preparing the Al-Mg-Mn-Ce master alloy, which can remove impurities, prevent oxidation, ensure the full dissolution and uniform distribution of each element in the Al-Mg-Mn-Ce master alloy, and guarantee the quality of the Al-Mg-Mn-Ce master alloy.

[0031] Furthermore, the heat preservation time after melting the pure Mg block and the Al-Mg-Mn-Ce master alloy is 30 - 40 min.

[0032] The heat preservation time when heating up to 700 - 710 °C and continuing is 30 - 40 min.

[0033] When adding the second refining agent and stirring, and then adding the second covering agent for refining, the refining temperature is 700 - 710 °C and the refining time is 15 - 30 min.

[0034] The above technical solution ensures that the final magnesium-lithium alloy ingot has uniform composition, high purity, and excellent performance by defining the melting and holding temperature and time, as well as the refining temperature and time when using the Al-Mg-Mn-Ce master alloy to prepare the magnesium-lithium alloy ingot.

[0035] Further, by mass percentage, the Al-Mg-Mn-Ce master alloy comprises the following components: Mg element: 1-3 wt%; Mn element: 4-12 wt%; Ce element: 0.4-1.4 wt%; the balance being Al element and inevitable impurities. Specific embodiments

[0036] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. It should be understood that the raw materials used in the following embodiments are all commercially available raw materials unless otherwise specified.

[0037] In a first aspect, an embodiment of the present invention provides a high-strength, tough, heat-resistant, and corrosion-resistant magnesium-lithium alloy ingot. By mass percentage, the magnesium-lithium alloy ingot comprises the following components: Li element: 1-5.7 wt%; Al element: 1-6 wt%; Mn element: 0.2-0.6 wt%; Ce element: 0.02-0.07 wt%; the balance being Mg element and inevitable impurities.

[0038] The present invention takes the α-Mg-based Mg-4Li alloy with Li element not exceeding 5.7 wt% as the research object. First, Al element is introduced to obtain the Mg-4Li-4.5Al alloy. Then, based on the Mg-4Li-4.5Al alloy, Mn element and Ce element are introduced to improve the mechanical and corrosion resistance properties of the alloy. The Mg-4Li-4.5Al alloy is composed of α-Mg, AlLi, Mg 17 Al 12 and consists. The α-Mg grains are dendrite-shaped, and high-density nano-scale AlLi particles are distributed in the grains. A large number of fine α-Mg+AlLi eutectic phases and a significant content of thick and long strip-shaped reticular α-Mg+Mg 17 Al 12 eutectic phases are distributed between the dendrites. At this time, the mechanical properties of the alloy are not high. After introducing specific contents of Mn element and Ce element, a significant content of spherical Al6Mn particles and a small amount of fine needle-shaped Al 11 Ce3 particles are formed in the α-Mg grains, and the Mg 17 Al 12, Al6Mn particles and α-Mg grains, significantly increasing the number and uniform dispersion of AlLi nanoparticles, thus effectively improving the mechanical properties of the alloy. Moreover, Ce element can also transform the Al8Mn5 phase formed by Mn element into Al8Mn4Ce phase, effectively improving the corrosion resistance of the alloy. In addition, the inventors found that when the a-Mg-based magnesium-lithium alloy ingot contains 0.03~0.07wt%, especially 0.05~0.06wt% of Ce element, the formed Al 11 Ce3 particles enable the magnesium-lithium alloy ingot to have higher advantages in high-temperature resistance performance.

[0039] Furthermore, on the basis of the above embodiments, the embodiments of the present invention further define that the magnesium-lithium alloy ingot includes the following components: Li element: 4~5.7wt%; Al element: 3~4.5wt%; Mn element: 0.3~0.5wt%; Ce element: 0.05~0.06wt%; the rest are Mg element and inevitable impurities.

[0040] The magnesium-lithium alloy ingot in the above technical solution has a more preferable element content range. With the synergistic cooperation of each element, the magnesium-lithium alloy ingot has better mechanical, corrosion resistance and high-temperature resistance performance.

[0041] Furthermore, on the basis of the above embodiments, the embodiments of the present invention further define that the yield strength of the magnesium-lithium alloy ingot is 165~200MPa, the tensile strength is 240~290MPa, the hardness is 70~75HV, the corrosion potential is -1.40~-1.50V, and the corrosion current density is 4×10 -5 ~5.5×10 -5 A / cm 2 .

[0042] The magnesium-lithium alloy ingot provided by the present invention has excellent mechanical properties, hardness and corrosion resistance.

[0043] In the second aspect, the embodiments of the present invention provide a preparation method for a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot, which is used for the above magnesium-lithium alloy ingot, and includes the following steps:

[0044] S1. Prepare raw materials according to the ratio: pure Mg blocks, pure Al blocks, pure Li grains, Mg-Ce master alloy and Al-Mn master alloy. Among them, the pure Li grains are pure Li grains wrapped with aluminum foil.

[0045] When preparing the metal materials in the above steps, the surface of other metal materials except the pure Li grains can be polished, and after treatment, they are placed in a drying oven for standby.

[0046] S2. At 760 - 810 °C, add pure Al blocks and Al-Mn master alloy, and then add the first covering agent for melting. After holding for a period of time, the first molten alloy liquid is obtained. Among them, the Al-Mn master alloy can be Al-20Mn master alloy.

[0047] The above steps can use a crucible for melting during smelting. The specific steps can be referred to as follows:

[0048] Put the crucible into an electric resistance furnace and heat it up to 760 - 810 °C. Put the pure Al blocks and Al-Mn master alloy into the crucible, then pour in the first covering agent, introduce a protective gas, and hold for 30 - 40 min.

[0049] Exemplarily, the temperature during holding can be 760 °C, 780 °C, 800 °C or 810 °C, and the holding time can be 30 min, 35 min or 40 min.

[0050] Among them, the first covering agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is (2 - 3)∶(2 - 3)∶1. The addition amount of the first covering agent is 3% - 4% of the total mass of the raw materials. Exemplarily, the mass ratio of MgCl2, KCl and CaF2 can be 2∶2∶1, 3∶3∶1 or 2∶3∶1, and the addition amount of the first covering agent can be 3%, 3.4%, 3.8% or 4% of the total mass of the raw materials. It should be understood that the total mass of the raw materials is the sum of the masses of each raw material prepared in step S1.

[0051] The first covering agent can form a protective film on the surface of the molten alloy liquid, thereby reducing heat loss, maintaining the stability of the melt temperature, preventing oxidation of the molten alloy liquid, and preventing metal burning loss.

[0052] The above steps can introduce a protective gas after adding the first covering agent. This protective gas can be a conventional inert gas. Exemplarily, the protective gas can be argon.

[0053] S3. After skimming the slag from the first molten alloy liquid, add Mg-Ce master alloy, and then add the first covering agent for melting. Cool down to 710 - 740 °C and hold for a period of time to obtain the second molten alloy liquid. Among them, the Mg-Ce master alloy can be Mg-30Ce master alloy.

[0054] The slag skimming in the above steps is to remove the protective layer formed by the first covering agent on the surface of the first molten alloy liquid.

[0055] Further, in the above steps, the heat preservation temperature is 710 - 740 °C, and the heat preservation time is 30 - 40 min. For example, the heat preservation temperature can be 710 °C, 720 °C, 730 °C or 740 °C, and the heat preservation time can be 30 min, 35 min or 40 min. The composition and addition amount of the first covering agent refer to the above step S2.

[0056] When melting the alloy in the above steps, it is carried out in the presence of a protective gas. Specifically, the protective gas can be introduced after adding the first covering agent, and the protective gas can be argon.

[0057] S4. After skimming the slag from the second molten alloy liquid, add the first refining agent and stir evenly, then add the first covering agent for refining. After skimming the slag, it is quickly cooled and formed in a water-cooled copper mold in the presence of a protective gas to obtain the Al-Mg-Mn-Ce master alloy.

[0058] By mass percentage, the above Al-Mg-Mn-Ce master alloy includes the following components: Mg element: 1 - 3 wt%; Mn element: 4 - 12 wt%; Ce element: 0.4 - 1.4 wt%; the rest are Al element and inevitable impurities.

[0059] The slag skimming in the above steps is to remove the protective layer formed by the first covering agent on the surface of the second molten alloy liquid.

[0060] Further, when adding the first refining agent and stirring evenly and adding the first covering agent for refining, the refining temperature is 710 - 720 °C, and the refining time is 15 - 30 min. For example, the refining temperature can be 710 °C, 715 °C or 720 °C, and the refining time can be 15 min, 20 min, 25 min or 30 min.

[0061] Among them, the first refining agent is MgCl2, KCl and CaF2; the mass ratio of MgCl2, KCl and CaF2 is (2 - 3):(2 - 3):4; for example, the mass ratio of MgCl2, KCl and CaF2 can be 3:3:4, 2:2:4 or 2:3:4. The addition amount of the first refining agent is 3% - 4% of the total mass of the raw materials. For example, the addition amount of the first refining agent can be 3%, 3.4%, 3.8% or 4% of the total mass of the raw materials. The composition and addition amount of the first covering agent refer to the above step S2.

[0062] In the above refining process, the refining agent can adsorb or wrap non-metallic inclusions (such as oxides, sulfides, etc.) in the melt, making them float to the surface of the melt, which is convenient for subsequent removal by slag skimming, thereby improving the purity of the alloy. It should be understood that the above refining process is also carried out in the presence of a protective gas. Specifically, the protective gas can be introduced after adding the first covering agent, and the protective gas during refining and casting can both be argon.

[0063] The Al-Mg-Mn-Ce master alloy prepared through the above melting and refining processes has a fine and uniformly dispersed microstructure. According to the principle of microstructure heredity, the magnesium-lithium alloy ingot prepared from this master alloy also has the characteristics of a fine and uniformly dispersed microstructure, thereby improving the hardness, mechanical properties, high-temperature resistance, and corrosion resistance of the magnesium-lithium alloy ingot.

[0064] S5. At 710 - 740 °C, add pure Mg blocks and the Al-Mg-Mn-Ce master alloy, and then add the second covering agent for melting, and keep warm for a period of time to obtain the third molten alloy liquid.

[0065] Exemplarily, the specific operation process can be referred to as follows:

[0066] Put the crucible into the resistance furnace and heat it up to 710 - 740 °C, put in pure Mg blocks and the Al-Mg-Mn-Ce master alloy, then add the second covering agent, introduce a protective gas, and keep warm for 30 - 40 min.

[0067] When melting the pure Mg blocks and the Al-Mg-Mn-Ce master alloy in the above steps, the holding temperature is 710 - 740 °C, and the holding time is 30 - 40 min. Exemplarily, the holding temperature can be 710 °C, 720 °C, 730 °C, or 740 °C, and the holding time is 30 min, 35 min, or 40 min.

[0068] Among them, the second covering agent is LiCl and LiF, and the mass ratio of LiCl to LiF is (3 - 4)∶1; the addition amount of the second covering agent is 3% - 4% of the total mass of the raw materials. Exemplarily, the mass ratio of LiCl to LiF can be 3∶1 or 4∶1; the addition amount of the second covering agent is 3%, 3.4%, 3.8%, or 4% of the total mass of the raw materials. It should be understood that the total mass of the raw materials is the sum of the masses of each raw material prepared in step S1.

[0069] The second covering agent can form a protective film on the surface of the molten alloy liquid, which has the functions of reducing heat loss, maintaining the stability of the melt temperature, preventing oxidation of the molten alloy liquid, and preventing metal burning loss.

[0070] In the above steps, a protective gas can be introduced after adding the first covering agent. This protective gas can be selected from conventional inert gases. Exemplarily, the protective gas can be argon.

[0071] S6. After skimming the slag from the third molten alloy liquid, cool it down to 600 - 620 °C, add pure Li particles wrapped in aluminum foil to melt under the liquid surface of the melted alloy, then add the second covering agent for melting, heat up to 700 - 710 °C and keep warm for a period of time to obtain the fourth molten alloy liquid.

[0072] The slag skimming in the above steps is to remove the protective layer formed by the second covering agent on the surface of the third molten alloy liquid.

[0073] Specifically, the detailed operation process can be referred to as follows:

[0074] After the slag skimming is completed, wait for the crucible to cool to 600 - 620 °C, then add pure Li grains wrapped in aluminum foil. Use a bell jar to press the pure Li grains wrapped in aluminum foil under the surface of the molten alloy, and then heat up to 700 - 710 °C, add the second covering agent and keep warm for 30 - 40 min.

[0075] For example, the temperature when adding the pure Li grains wrapped in aluminum foil can be 600 °C, 610 °C or 620 °C, the heat preservation temperature can be 700 °C, 705 °C or 710 °C, and the heat preservation time can be 30 min, 35 min or 40 min. Among them, the composition and addition amount of the second covering agent refer to the above step S5.

[0076] The above smelting steps are carried out in the presence of a protective gas. Specifically, the protective gas can be introduced after adding the second covering agent, and the protective gas can all be argon.

[0077] S7. After slag skimming the fourth molten alloy liquid, add the second refining agent and stir evenly, then add the second covering agent for refining. After slag skimming, cast into a mold in the presence of a protective gas, and obtain a magnesium - lithium alloy ingot after cooling.

[0078] The first slag skimming in the above step S7 is to remove the protective layer formed by the second covering agent on the surface of the fourth molten alloy liquid.

[0079] Furthermore, when adding the second refining agent and stirring evenly, then adding the second covering agent for refining, the refining temperature is 700 - 710 °C, and the refining time is 15 - 30 min. For example, the refining temperature can be 700 °C, 705 °C or 710 °C, and the refining time can be 15 min, 20 min, 25 min or 30 min.

[0080] Among them, the second refining agent is LiCl, LiF and CaF2, and the mass ratio of LiCl, LiF and CaF2 is (3 - 4)∶1∶(0.8 - 1); for example, the mass ratio of LiCl, LiF and CaF2 can be 3∶1∶0.8, 4∶1∶0.8 or 4∶1∶1. The addition amount of the second refining agent is 4% - 6% of the total mass of the raw materials. For example, the addition amount of the second refining agent is 4%, 5% or 6% of the total mass of the raw materials. The composition and addition amount of the second covering agent refer to the above step S5.

[0081] Through the refining of the above steps, non - metallic impurities in the molten alloy liquid can be effectively removed, ensuring the purity of the molten alloy liquid, and thus ensuring the purity and performance of the obtained magnesium - lithium alloy ingot.

[0082] The above refining process is carried out in the presence of a protective gas. Specifically, the protective gas can be introduced after adding the second covering agent, and the protective gas during refining and casting can both be argon gas. Example 1

[0083] An embodiment of the present invention provides a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot, which, by mass percentage, includes the following components: Li element: 4wt%; Al element: 4.5wt%; Mn element: 0.3wt%; Ce element: 0.05wt%; the balance is Mg element and inevitable impurities.

[0084] The embodiment of the present invention also provides a method for preparing the above magnesium-lithium alloy ingot, which includes the following steps:

[0085] S1. Prepare pure Mg blocks, pure Al blocks, pure Li grains wrapped in aluminum foil, Mg-30Ce master alloy and Al-20Mn master alloy according to the ratio.

[0086] S2. Place the crucible in a resistance furnace and heat it up to 780°C. Put the pure Al blocks and Al-20Mn master alloy into the crucible, then pour in the first covering agent. The addition amount of the first covering agent is 3.8% of the total mass of the raw materials. Introduce the protective gas argon and keep it warm for 30 minutes to obtain the first molten alloy liquid. Among them, the first covering agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 2:2:1.

[0087] S3. After skimming the slag from the first molten alloy liquid, add the Mg-30Ce master alloy, then add the first covering agent for smelting, introduce the protective gas argon, and keep it warm at 720°C for 30 minutes to obtain the second molten alloy liquid. The composition and addition amount of the first covering agent refer to the above step S2.

[0088] S4. After skimming the slag from the second molten alloy liquid, add the first refining agent and stir evenly, then add the first covering agent for refining. Introduce the protective gas argon and refine it at 710°C for 15 minutes. After skimming the slag, in the presence of the protective gas argon, quickly cool and form it in a water-cooled cylindrical copper mold to obtain the Al-Mg-Mn-Ce master alloy. Among them, the first refining agent is MgCl2, KCl and CaF2, the mass ratio of MgCl2, KCl and CaF2 is 3:3:4, the addition amount of the first refining agent is 3.8% of the total mass of the raw materials, and the composition and addition amount of the first covering agent refer to the above step S2.

[0089] S5. Place the crucible in a resistance furnace and heat it up to 720 °C. Put pure Mg blocks and Al-Mg-Mn-Ce master alloy into it, then add the second covering agent, introduce the protective gas argon, and keep it warm for 30 min to obtain the third molten alloy liquid. Among them, the second covering agent is LiCl and LiF, and the mass ratio of LiCl to LiF is 3:1; the addition amount of the second covering agent is 3.8% of the total mass of the raw materials.

[0090] S6. After skimming the slag from the third molten alloy liquid, wait until the crucible cools to 600 °C, then add pure Li grains wrapped in aluminum foil. Use a bell to press the pure Li grains wrapped in aluminum foil under the liquid surface of the molten alloy, then heat it up to 710 °C, add the second covering agent, introduce the protective gas argon, and keep it warm for 30 min to obtain the fourth molten alloy liquid. Among them, the composition and addition amount of the second covering agent refer to the above step S5.

[0091] S7. After skimming the slag from the fourth molten alloy liquid, add the second refining agent and stir evenly, then add the second covering agent for refining, introduce the protective gas argon, refine at 700 °C for 20 min, skim the slag, and then cast it into a cylindrical copper mold in the presence of the protective gas argon. After cooling, a magnesium-lithium alloy ingot is obtained. Among them, the second refining agent is LiCl, LiF and CaF2, and the mass ratio of LiCl, LiF and CaF2 is 3:1:0.8; the addition amount of the second refining agent is 5% of the total mass of the raw materials. The composition and addition amount of the second covering agent refer to the above step S5. Example 2

[0092] The embodiment of the present invention provides a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot, which includes the following components by mass percentage: Li element: 5.7 wt%; Al element: 3 wt%; Mn element: 0.5 wt%; Ce element: 0.06 wt%; the rest are Mg element and inevitable impurities.

[0093] The embodiment of the present invention also provides a preparation method of the above magnesium-lithium alloy ingot, which includes the following steps:

[0094] S1. Prepare pure Mg blocks, pure Al blocks, pure Li grains wrapped in aluminum foil, Mg-30Ce master alloy and Al-20Mn master alloy according to the proportion.

[0095] S2. Place the crucible in a resistance furnace and heat it up to 810 °C. Put the pure Al blocks and Al-20Mn master alloy into the crucible, then pour in the first covering agent. The addition amount of the first covering agent is 3.8% of the total mass of the raw materials. Introduce the protective gas argon and keep it warm for 35 min to obtain the first molten alloy liquid. Among them, the first covering agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 2:2:1.

[0096] S3. After skimming the slag from the first molten alloy liquid, add Mg-30Ce master alloy, then add the first covering agent for smelting, introduce the protective gas argon, keep it warm at 740 °C for 35 min to obtain the second molten alloy liquid. The composition and addition amount of the first covering agent refer to step S2 above.

[0097] S4. After skimming the slag from the second molten alloy liquid, add the first refining agent and stir evenly, then add the first covering agent for refining, introduce the protective gas argon, refine at 715 °C for 25 min, after skimming the slag, under the presence of the protective gas argon, quickly cool and form in a water-cooled cylindrical copper mold to obtain the Al-Mg-Mn-Ce master alloy. Among them, the first refining agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 3:3:4. The addition amount of the first refining agent is 3.8% of the total mass of the raw materials. The composition and addition amount of the first covering agent refer to step S2 above.

[0098] S5. Place the crucible in a resistance furnace and heat it up to 740 °C, put pure Mg blocks and Al-Mg-Mn-Ce master alloy, then add the second covering agent, introduce the protective gas argon, keep it warm for 35 min to obtain the third molten alloy liquid. Among them, the second covering agent is LiCl and LiF, and the mass ratio of LiCl and LiF is 3:1; the addition amount of the second covering agent is 3.8% of the total mass of the raw materials.

[0099] S6. After skimming the slag from the third molten alloy liquid, wait for the crucible to cool to 620 °C and add pure Li grains wrapped in aluminum foil, use a bell jar to press the pure Li grains wrapped in aluminum foil under the liquid surface of the molten alloy, then heat up to 700 °C, add the second covering agent, introduce the protective gas argon, keep it warm for 40 min to obtain the fourth molten alloy liquid. The composition and addition amount of the second covering agent refer to step S5 above.

[0100] S7. After skimming the slag from the fourth molten alloy liquid, add the second refining agent and stir evenly, then add the second covering agent for refining, introduce the protective gas argon, refine at 710 °C for 15 min, after skimming the slag, under the presence of the protective gas argon, cast and form in a cylindrical copper mold, and obtain a magnesium-lithium alloy ingot after cooling. Among them, the second refining agent is LiCl, LiF and CaF2, and the mass ratio of LiCl, LiF and CaF2 is 3:1:0.8; the addition amount of the second refining agent is 5% of the total mass of the raw materials. The composition and addition amount of the second covering agent refer to step S5 above. Example 3

[0101] An embodiment of the present invention provides a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot, which, by mass percentage, comprises the following components: Li element: 1 wt%; Al element: 1 wt%; Mn element: 0.2 wt%; Ce element: 0.02 wt%; the balance being Mg element and inevitable impurities.

[0102] An embodiment of the present invention also provides a preparation method of the above magnesium-lithium alloy ingot, comprising the following steps:

[0103] S1. Prepare pure Mg blocks, pure Al blocks, pure Li grains wrapped with aluminum foil, Mg-30Ce master alloy and Al-20Mn master alloy in proportion.

[0104] S2. Place the crucible in a resistance furnace and heat it up to 760 °C. Put the pure Al blocks and Al-20Mn master alloy into the crucible, then pour in the first covering agent. The addition amount of the first covering agent is 3% of the total mass of the raw materials. Pass in the protective gas argon and keep warm for 40 min to obtain the first molten alloy liquid. Among them, the first covering agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 3:3:1.

[0105] S3. After skimming the slag from the first molten alloy liquid, add the Mg-30Ce master alloy, then add the first covering agent for smelting. Pass in the protective gas argon and keep warm at 710 °C for 40 min to obtain the second molten alloy liquid. The composition and addition amount of the first covering agent refer to the above step S2.

[0106] S4. After skimming the slag from the second molten alloy liquid, add the first refining agent and stir evenly, then add the first covering agent for refining. Pass in the protective gas argon and refine at 720 °C for 30 min. After skimming the slag, rapidly cool and form in a water-cooled cylindrical copper mold in the presence of the protective gas argon to obtain the Al-Mg-Mn-Ce master alloy. Among them, the first refining agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 2:2:4. The addition amount of the first refining agent is 3% of the total mass of the raw materials. The composition and addition amount of the first covering agent refer to the above step S2.

[0107] S5. Place the crucible in a resistance furnace and heat it up to 710 °C. Put the pure Mg blocks and the Al-Mg-Mn-Ce master alloy into it, then add the second covering agent. Pass in the protective gas argon and keep warm for 40 min to obtain the third molten alloy liquid. Among them, the second covering agent is LiCl and LiF, and the mass ratio of LiCl and LiF is 4:1; the addition amount of the second covering agent is 3% of the total mass of the raw materials.

[0108] S6. After skimming the slag from the third molten alloy liquid, wait for the crucible to cool to 610 °C, then add pure Li pellets wrapped in aluminum foil. Use a bell jar to press the pure Li pellets wrapped in aluminum foil under the liquid surface of the molten alloy, then heat up to 705 °C, add the second covering agent, introduce the protective gas argon, and keep warm for 35 min to obtain the fourth molten alloy liquid. Among them, the composition and addition amount of the second covering agent refer to step S5 above.

[0109] S7. After skimming the slag from the fourth molten alloy liquid, add the second refining agent and stir evenly, then add the second covering agent for refining. Introduce the protective gas argon and refine at 705 °C for 30 min. After skimming the slag, cast and form in a cylindrical copper mold in the presence of the protective gas argon, and obtain a magnesium-lithium alloy ingot after cooling. Among them, the second refining agent is LiCl, LiF, and CaF2, and the mass ratio of LiCl, LiF, and CaF2 is 4:1:1; the addition amount of the second refining agent is 4% of the total mass of the raw materials. The composition and addition amount of the second covering agent refer to step S5 above. Example 4

[0110] An embodiment of the present invention provides a high-strength, tough, heat-resistant, and corrosion-resistant magnesium-lithium alloy ingot, which includes the following components by mass percentage: Li element: 3.5 wt%; Al element: 6 wt%; Mn element: 0.6 wt%; Ce element: 0.07 wt%; the rest are Mg element and inevitable impurities.

[0111] An embodiment of the present invention also provides a preparation method of the above magnesium-lithium alloy ingot, including the following steps:

[0112] S1. Prepare pure Mg blocks, pure Al blocks, pure Li pellets wrapped in aluminum foil, Mg-30Ce master alloy, and Al-20Mn master alloy according to the ratio.

[0113] S2. Place the crucible in a resistance furnace and heat up to 800 °C. Put the pure Al blocks and Al-20Mn master alloy into the crucible, then pour in the first covering agent. The addition amount of the first covering agent is 4% of the total mass of the raw materials. Introduce the protective gas argon and keep warm for 35 min to obtain the first molten alloy liquid. Among them, the first covering agent is MgCl2, KCl, and CaF2, and the mass ratio of MgCl2, KCl, and CaF2 is 2:3:1.

[0114] S3. After skimming the slag from the first molten alloy liquid, add the Mg-30Ce master alloy, then add the first covering agent for melting. Introduce the protective gas argon and keep warm at 730 °C for 35 min to obtain the second molten alloy liquid. The composition and addition amount of the first covering agent refer to step S2 above.

[0115] S4. After skimming the slag from the second molten alloy liquid, add the first refining agent and stir evenly, then add the first covering agent for refining. Introduce the protective gas argon, and refine at 715 °C for 20 min. After skimming the slag, in the presence of the protective gas argon, quickly cool and form in a water-cooled cylindrical copper mold to obtain the Al-Mg-Mn-Ce master alloy. Among them, the first refining agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 2:3:4. The addition amount of the first refining agent is 4% of the total mass of the raw materials. The composition and addition amount of the first covering agent refer to the above step S2.

[0116] S5. Place the crucible in an electric resistance furnace and heat it up to 730 °C. Put pure Mg blocks and the Al-Mg-Mn-Ce master alloy into it, then add the second covering agent, introduce the protective gas argon, and keep it warm for 35 min to obtain the third molten alloy liquid. Among them, the second covering agent is LiCl and LiF, and the mass ratio of LiCl and LiF is 4:1; the addition amount of the second covering agent is 4% of the total mass of the raw materials.

[0117] S6. After skimming the slag from the third molten alloy liquid, wait for the crucible to cool to 600 °C and add pure Li grains wrapped in aluminum foil. Use a bell jar to press the pure Li grains wrapped in aluminum foil under the liquid surface of the molten alloy, then heat up to 705 °C, add the second covering agent, introduce the protective gas argon, and keep it warm for 35 min to obtain the fourth molten alloy liquid. Among them, the composition and addition amount of the second covering agent refer to the above step S5.

[0118] S7. After skimming the slag from the fourth molten alloy liquid, add the second refining agent and stir evenly, then add the second covering agent for refining. Introduce the protective gas argon, and refine at 710 °C for 25 min. After skimming the slag, in the presence of the protective gas argon, cast and form in a cylindrical copper mold, and obtain a magnesium-lithium alloy ingot after cooling. Among them, the second refining agent is LiCl, LiF and CaF2, and the mass ratio of LiCl, LiF and CaF2 is 4:1:0.8; the addition amount of the second refining agent is 6% of the total mass of the raw materials. The composition and addition amount of the second covering agent refer to the above step S5. Comparative Example 1

[0119] Compared with the magnesium-lithium alloy ingot in Example 1, the difference is only that the content of Ce element is 0.1 wt%, and the contents of the other elements remain unchanged. Comparative Example 2

[0120] Compared with the magnesium-lithium alloy ingot in Example 1, the difference is only that the Ce element is replaced with an equal amount of Mn element, and the contents of the other elements remain unchanged.

[0121] The preparation method of the magnesium-lithium alloy ingot in this comparative example includes the following steps:

[0122] S1. Prepare pure Mg blocks, pure Al blocks, pure Li grains wrapped with aluminum foil, and Mg-5Mn master alloy in proportion.

[0123] S2. Place the crucible in a resistance furnace and heat it up to 720 °C. Put the pure Mg blocks and pure Al blocks into the crucible, then add the covering agent and keep it warm for 30 min to obtain the first molten alloy liquid. Among them, the covering agent is LiCl and LiF, and the mass ratio of LiCl to LiF is 3:1; the addition amount of the covering agent is 3.5% of the total mass of the raw materials.

[0124] S3. After skimming the slag from the first molten alloy liquid, add the Mg-5Mn master alloy, then add the covering agent for smelting, introduce the protective gas argon, and keep it warm at 720 °C for 30 min to obtain the second molten alloy liquid. The composition and addition amount of the covering agent refer to step S2 above.

[0125] S4. After skimming the slag from the second molten alloy liquid, add the pure Li grains wrapped with aluminum foil at 600 °C. Use a bell to press the pure Li grains wrapped with aluminum foil under the liquid surface of the molten alloy, then add the covering agent, introduce the protective gas argon, and keep it warm at 710 °C for 30 min to obtain the third molten alloy liquid. The composition and addition amount of the covering agent refer to step S2 above.

[0126] S5. After skimming the slag from the third molten alloy liquid, add the refining agent and stir evenly, then add the covering agent for refining, introduce the protective gas argon, refine at 710 °C for 20 min, skim the slag, and then cast and form in a cylindrical copper mold in the presence of the protective gas argon. After cooling, a magnesium-lithium alloy ingot is obtained. Among them, the composition of the refining agent is LiCl, LiF, and CaF2, and the mass ratio of LiCl, LiF, and CaF2 is 3:1:0.8. The addition amount of the refining agent is 5% of the total mass of the raw materials. The composition and addition amount of the covering agent refer to step S2 above. Comparative Example 3

[0127] Compared with the magnesium-lithium alloy ingot in Example 1, the difference is only that the content of Mn element is 0.9 wt%, and the contents of the other elements remain unchanged. Comparative Example 4

[0128] Compared with the magnesium-lithium alloy ingot in Example 1, the difference is only that the content of Li element is 6.3 wt%, and the contents of the other elements remain unchanged. Comparative Example 5

[0129] Compared with the magnesium-lithium alloy ingot in Example 1, the difference is only that the content of Al element is 7 wt%, and the contents of the other elements remain unchanged. Comparative Example 6

[0130] Compared with the preparation method of the magnesium-lithium alloy ingot in Example 1, the difference is that another method is used to prepare the magnesium-lithium alloy ingot.

[0131] In this comparative example, the preparation method of the magnesium-lithium alloy ingot comprises the following steps:

[0132] S1. Prepare pure Mg blocks, pure Al blocks, pure Li grains wrapped in aluminum foil, Mg-5Mn master alloy, and Mg-30Ce master alloy in proportion.

[0133] S2. Place the crucible in a resistance furnace and heat it up to 720 °C. Add the pure Mg blocks and pure Al blocks into the crucible, then add a covering flux for smelting. Introduce the protective gas argon and keep it warm for 30 min to obtain the first molten alloy liquid. Among them, the covering flux is LiCl and LiF, and the mass ratio of LiCl to LiF is 3:1; the addition amount of the covering flux is 3.5% of the total mass of the raw materials.

[0134] S3. After skimming the slag from the first molten alloy liquid, add Mg-5Mn and Mg-30Ce master alloys, then add a covering flux for smelting. Introduce the protective gas argon and keep it warm at 720 °C for 30 min to obtain the second molten alloy liquid. The composition and addition amount of the covering flux refer to step S2 above.

[0135] S4. After skimming the slag from the second molten alloy liquid, add the pure Li grains wrapped in aluminum foil at 600 °C. Use a bell jar to press the pure Li grains wrapped in aluminum foil under the liquid surface of the molten alloy, then add a covering flux for smelting. Introduce the protective gas argon and keep it warm at 710 °C for 30 min to obtain the third molten alloy liquid. The composition and addition amount of the covering flux refer to step S2 above.

[0136] S5. After skimming the slag from the third molten alloy liquid, add a refining agent and stir evenly, then add a covering flux for refining. Introduce the protective gas argon and refine at 710 °C for 20 min. After skimming the slag, cast it into a cylindrical copper mold in the presence of the protective gas argon and cool to obtain the magnesium-lithium alloy ingot. Among them, the composition of the refining agent is LiCl, LiF, and CaF2, and the mass ratio of LiCl, LiF, and CaF2 is 3:1:0.8. The addition amount of the refining agent is 5% of the total mass of the raw materials. The composition and addition amount of the covering flux refer to step S2 above. Comparative Example 7

[0137] Compared with the preparation method of the magnesium-lithium alloy ingot in Example 1, the difference is only that after refining in step S4, instead of casting to prepare the Al-Mg-Mn-Ce master alloy, directly skim the slag from the molten alloy liquid obtained after refining, heat it up to 720 °C, add pure Mg blocks, then add a second covering flux, introduce the protective gas argon, and keep it warm for 30 min to obtain the third molten alloy liquid.

[0138] Test Example 1

[0139] Detect the yield strength, tensile strength, elongation, hardness, corrosion potential, and corrosion current density of the magnesium-lithium alloy ingots provided in Examples 1-4 and Comparative Examples 1-7 above. The results are shown in Table 1.

[0140] Table 1

[0141]

[0142] From the above results, it can be seen that in Comparative Example 1, when the content of Ce element in the magnesium-lithium alloy ingot was increased and the content of Ce element was set to 0.1 wt%, the yield strength, tensile strength, and hardness of the magnesium-lithium alloy ingot all decreased, the corrosion potential became more negative, and the corrosion current density increased. This shows that the Ce element with a specific content in the present invention can enhance the mechanical properties and corrosion resistance of the alloy through Al 30 Ce2Mg, (AlMg) 10 Mn2Ce phases, but excessive Ce element will reduce the mechanical properties and corrosion resistance of the alloy.

[0143] In Comparative Example 2, when the Ce element was replaced with an equal amount of Mn element, the yield strength, tensile strength, and hardness of the magnesium-lithium alloy ingot all decreased, the corrosion potential became more negative, and the corrosion current density increased. This shows that the Al 30 Ce2Mg phase that refines the α-Mg grains is indispensable; at the same time, the (AlMg) 10 Mn2Ce phase generated by the Ce element and the Mn element can refine the AlLi phase and MgLiAl2, thereby improving the mechanical properties and corrosion resistance of the magnesium-lithium alloy. The combined action of the two improves the mechanical properties and corrosion resistance of the magnesium-lithium alloy.

[0144] In Comparative Example 3, when the content of Mn element in the magnesium-lithium alloy ingot was increased and the content of Mn element was set to 0.9 wt%, the yield strength, tensile strength, and hardness of the magnesium-lithium alloy ingot all decreased, the corrosion potential became more negative, and the corrosion current density increased. This shows that there is a threshold for the addition amount of Mn element, and after exceeding the threshold, the mechanical properties and corrosion resistance of the alloy show a downward trend.

[0145] In Comparative Example 4, when the content of Li element in the magnesium-lithium alloy ingot was increased and the content of Li element was set to 6.3 wt%, the yield strength and tensile strength of the magnesium-lithium alloy ingot decreased, the corrosion potential became more negative, and the corrosion current density increased. This shows that the higher the Li content, the more the matrix of the magnesium-lithium alloy changes, resulting in a decrease in the mechanical properties of the magnesium-lithium alloy and a downward trend in the corrosion resistance at the same time.

[0146] In Comparative Example 5, the content of Al element in the magnesium-lithium alloy ingot was increased. After setting the content of Al element to 7 wt%, the yield strength, tensile strength, and hardness of the magnesium-lithium alloy ingot all decreased, the corrosion potential became more negative, and the corrosion current density increased. This indicates that there is a threshold for the content of Al element. When the content is lower than 6 wt%, the mechanical properties and corrosion resistance of the magnesium-lithium alloy can be improved, but when it exceeds the threshold, the properties of the alloy will decline instead.

[0147] In Comparative Example 6, the preparation method was changed. Instead of preparing the Al-Mg-Mn-Ce master alloy, the Mn element was added in the form of a Mg-5Mn master alloy. The yield strength, tensile strength, and hardness of the magnesium-lithium alloy ingot all decreased, the corrosion potential became more negative, and the corrosion current density increased. This shows that directly adding the Mn element in the form of a Mg-5Mn master alloy without preparing the Al-Mg-Mn-Ce master alloy will cause the grains and particles of the magnesium-lithium alloy to become coarser, resulting in a significant decline in the mechanical properties and corrosion resistance of the alloy.

[0148] In Comparative Example 7, the preparation method was changed. After adding the Mn element in the form of an Al-20Mn master alloy in step S2, in the subsequent step S4, instead of casting and forming the Al-Mg-Mn-Ce master alloy, the slag on the refined molten alloy liquid was skimmed off directly, the temperature was raised to 720 °C, pure Mg blocks were put in, and then a second covering agent was added. Argon, the protective gas, was introduced, and the mixture was kept warm for 30 min to obtain a third molten alloy liquid. The yield strength, tensile strength, and hardness of the finally prepared magnesium-lithium alloy ingot all decreased, the corrosion potential became more negative, and the corrosion current density increased. This indicates that the Al-Mn compounds in the Al-20Mn master alloy have a much worse grain refinement effect on the magnesium-lithium alloy than the Al6Mn, Al 30 Ce2Mn, (AlMg) 10 Mn2Ce on the grain refinement of the magnesium-lithium alloy, but is better than the grain refinement effect of α-Mg and α-Mn in Mg-5Mn in Comparative Example 6 on the magnesium-lithium alloy grains.

[0149] Test Example 2

[0150] Detect the high-temperature resistance of the magnesium-lithium alloy ingots provided in Examples 1 to 4 and Comparative Examples 1 to 7 above.

[0151] The magnesium-lithium alloy ingots in Examples 1 to 4 and Comparative Examples 1 to 7 above were respectively subjected to solution treatment. The specific process is as follows: The above-mentioned magnesium-lithium alloy ingots were respectively placed in a furnace preheated to 200 °C, and the temperature was further raised to 350 °C and kept warm for 3 hours. After the heat preservation ended, the magnesium-lithium alloy ingots were quickly taken out of the furnace and immersed in cooling water for quenching.

[0152] After solution treatment, the yield strength, tensile strength, and elongation of the magnesium-lithium alloy ingots in Examples 1 to 4 and Comparative Examples 1 to 7 were measured respectively. The results are shown in Table 2.

[0153] Table 2

[0154]

[0155] From the above results, it can be seen that: after heat-treating the magnesium-lithium alloy ingots in Examples 1 to 4 and Comparative Examples 1 to 7, compared with Comparative Examples 1 to 7, the attenuation degree of the tensile properties of the magnesium-lithium alloy ingots in Examples 1 to 4 of the present invention is lower, and they still have better yield strength and tensile strength after heat treatment, indicating that the various elements in the magnesium-lithium alloy ingots of the present invention cooperate with each other, and can effectively improve the high-temperature resistance of the magnesium-lithium alloy ingots. In particular, the Ce element and Mn element with specific contents in the present invention generate Al 11 Ce3 and (AlMg) 10 The Mn2Ce phase can significantly improve the heat resistance of the magnesium-lithium alloy.

[0156] In addition, the yield ratio of the magnesium-lithium alloy after heat treatment in the present invention is relatively low, indicating that the magnesium-lithium alloy ingots in the present invention have excellent plastic forming properties after heat treatment, which is convenient for subsequent secondary processing.

[0157] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot, characterized in that, By mass percentage, the magnesium-lithium alloy ingot comprises the following components: Li element: 1 - 5.7 wt%; Al element: 1 - 6 wt%; Mn element: 0.2 - 0.6 wt%; Ce element: 0.02 - 0.07 wt%; the balance is Mg element and inevitable impurities; The high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot is prepared by a preparation method comprising the following steps: Prepare raw materials in proportion: pure Mg blocks, pure Al blocks, pure Li grains, Mg-30Ce master alloy and Al-20Mn master alloy; At 760 - 810 °C, sequentially add pure Al blocks, Al-20Mn master alloy, and the first covering flux for melting, keep warm, skim the slag, then sequentially add Mg-30Ce master alloy and the first covering flux for melting, cool down to 710 - 740 °C and keep warm, skim the slag, then add the first refining agent and stir, add the first covering flux again, continue to keep warm, skim the slag and then cast into shape, and obtain the Al-Mg-Mn-Ce master alloy after cooling; At 710 - 740 °C, sequentially add pure Mg blocks, Al-Mg-Mn-Ce master alloy, and the second covering flux for melting, skim the slag after keeping warm, cool down to 600 - 620 °C, add the pure Li grains wrapped with aluminum foil to melt under the liquid surface of the melted alloy, add the second covering flux again, raise the temperature to 700 - 710 °C and continue to keep warm, skim the slag, then add the second refining agent and stir, add the second covering flux again, skim the slag after keeping warm, cast into shape, and obtain the magnesium-lithium alloy ingot after cooling.

2. The magnesium-lithium alloy ingot according to claim 1, wherein, By mass percentage, the magnesium-lithium alloy ingot comprises the following components: Li element: 4 - 5.7 wt%; Al element: 3 - 4.5 wt%; Mn element: 0.3 - 0.5 wt%; Ce element: 0.05 - 0.06 wt%; the balance is Mg element and inevitable impurities.

3. The magnesium-lithium alloy ingot according to claim 1, characterized in that, The yield strength of the magnesium-lithium alloy ingot is 165-200 MPa, the tensile strength is 240-290 MPa, the hardness is 70-75 HV, the corrosion potential is -1.40 to -1.50 V, and the corrosion current density is 4×10 -5 ~5.5×10 -5 A / cm 2 .

4. A method for preparing a high-strength, tough, heat-resistant and corrosion-resistant magnesium-lithium alloy ingot, which is used to prepare the magnesium-lithium alloy ingot described in any one of claims 1 to 3, and is characterized in that, Comprises the following steps: Prepare raw materials in proportion: pure Mg blocks, pure Al blocks, pure Li grains, Mg-Ce master alloy and Al-Mn master alloy; At 760 - 810 °C, sequentially add pure Al blocks, Al-Mn master alloy, and the first covering flux for melting, keep warm, skim the slag, then sequentially add Mg-Ce master alloy and the first covering flux for melting, cool down to 710 - 740 °C and keep warm, skim the slag, then add the first refining agent and stir, add the first covering flux again, continue to keep warm, skim the slag and then cast into shape, and obtain the Al-Mg-Mn-Ce master alloy after cooling; At 710 - 740 °C, sequentially add pure Mg blocks, Al-Mg-Mn-Ce master alloy, and the second covering flux for melting, skim the slag after keeping warm, cool down to 600 - 620 °C, add the pure Li grains wrapped with aluminum foil to melt under the liquid surface of the melted alloy, add the second covering flux again, raise the temperature to 700 - 710 °C and continue to keep warm, skim the slag, then add the second refining agent and stir, add the second covering flux again, skim the slag after keeping warm, cast into shape, and obtain the magnesium-lithium alloy ingot after cooling.

5. The preparation method according to claim 4, wherein The first covering flux is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 2 - 3∶2 - 3∶1; The second covering agent is LiCl and LiF, and the mass ratio of LiCl to LiF is 3 - 4:1; Each time when adding the first covering agent or the second covering agent, an inert gas is introduced for protection; Moreover, the addition amount of the first covering agent is 3% - 4% of the total mass of the raw materials; the addition amount of the second covering agent is 3% - 4% of the total mass of the raw materials.

6. The preparation method according to claim 4, wherein The first refining agent is MgCl2, KCl and CaF2, and the mass ratio of MgCl2, KCl and CaF2 is 2 - 3:2 - 3:4; The second refining agent is LiCl, LiF and CaF2, and the mass ratio of LiCl, LiF and CaF2 is 3 - 4:1:0.8 - 1.

7. The preparation method according to claim 4, characterized in that, The addition amount of the first refining agent is 3% - 4% of the total mass of the raw materials; the addition amount of the second refining agent is 4% - 6% of the total mass of the raw materials.

8. The preparation method according to claim 4, characterized in that The heat preservation time after melting the pure Al block and the Al-Mn master alloy is 30 - 40 min; Add Mg-Ce master alloy and the first covering agent for melting, and the heat preservation time after cooling is 30 - 40 min; When adding the first refining agent and stirring, and then adding the first covering agent for refining, the refining temperature is 710 - 720 °C, and the refining time is 15 - 30 min.

9. The preparation method according to claim 4, characterized in that, The heat preservation time after melting the pure Mg block and the Al-Mg-Mn-Ce master alloy is 30 - 40 min; The heat preservation time when heating up to 700 - 710 °C and continuing is 30 - 40 min; When adding the second refining agent and stirring, and then adding the second covering agent for refining, the refining temperature is 700 - 710 °C, and the refining time is 15 - 30 min.

10. The preparation method according to claim 4, characterized in that, By mass percentage, the Al-Mg-Mn-Ce master alloy includes the following components: Mg element: 1 - 3 wt%; Mn element: 4 - 12 wt%; Ce element: 0.4 - 1.4 wt%; the rest are Al element and inevitable impurities.

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