A heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity and brazability and a preparation method thereof

Abstract

This invention belongs to the technical field of industrial magnesium alloy materials, specifically a heat-resistant magnesium alloy with high strength, toughness, high conductivity, and brazability, and its preparation method. By mass percentage, the magnesium alloy comprises: Zn 5.0%–8.0%, Mn 0.5%–1.5%, Cu 0.5%–3.5%, Ag 0.05%–3.5%, Ca 0.01%–1.5%, with the balance being Mg. The magnesium alloy material prepared by the method combined with specific processes has a tensile strength ≥360MPa, elongation ≥10%, conductivity ≥19MS / m, tensile strength ≥200MPa at 200℃, and a tensile strength decrease of ≤10% after brazing at 350–450℃. Furthermore, it can be brazed into complex cavity components integrating load-bearing and conductive functions, enabling service in high-temperature environments up to 200℃. It has significant application value in electronic signal and microwave signal transmission components in aerospace, aviation, transportation, and weaponry fields.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial magnesium alloy materials, and particularly relates to a heat-resistant magnesium alloy with high strength, toughness, high electrical conductivity, and brazing capability, and its preparation method. Background Technology

[0002] Magnesium alloys are currently the lightest engineering structural metals in the world, with a density only 2 / 3 that of aluminum alloys. With the rapid development of magnesium alloy strength, electrical and thermal conductivity, heat resistance, and related protection technologies, the application of magnesium alloys in simple load-bearing components in the aerospace field is rapidly increasing, making them an ideal material for lightweighting in aerospace, weaponry, and transportation.

[0003] In recent years, with the urgent need for lightweight electronic signal transmission components in aerospace, transportation, and weaponry, extremely high comprehensive performance requirements have been placed on magnesium alloy materials: 1) High strength and toughness mechanical properties (tensile strength ≥360MPa, elongation ≥10%); 2) High electrical conductivity (≥19MS / m); 3) Heat resistance, with an operating temperature of 200℃ (tensile strength ≥200MPa at 200℃); 4) Because the transmission channels for electronic or microwave signals are composed of multiple layers of sealed space with complex internal structures that cannot be obtained through machining, they need to be assembled by brazing multiple layers of magnesium alloy materials. Currently, the welding temperature of magnesium alloys is greater than 400℃, requiring that the performance of the base material decreases little during the brazing process (the tensile strength of the base material decreases by ≤10% after brazing at temperatures of 350~450℃). In short, these fields require magnesium alloys to possess high strength and toughness while also meeting comprehensive performance requirements such as high electrical conductivity, heat resistance, and brazing capability.

[0004] The properties of existing magnesium alloys are shown in Table 1. It can be observed that the heat resistance, brazing properties, and electrical conductivity of magnesium alloys are mutually exclusive. Alloying combined with various strengthening methods can improve the strength, toughness, and heat resistance of magnesium alloys, but inevitably, it will severely affect the alloy's electrical conductivity. For example: ① Mg-RE alloys have the best strength, heat resistance, and brazing properties among all magnesium alloys, but they have poor toughness and the lowest electrical conductivity, decreasing by about 80% compared to pure magnesium. The mechanism is that the atomic radii of rare earth elements differ greatly from those of magnesium atoms. When rare earth elements dissolve into the magnesium matrix, they cause severe lattice distortion in the magnesium matrix, leading to scattering of free electrons during flow, increasing the alloy resistivity, and reducing the electrical conductivity of magnesium. Even adding trace amounts of rare earth elements has a significant impact on electrical conductivity, making it impossible to achieve the high electrical conductivity required for magnesium alloys. ② On the other hand, Mg-Zn alloys, which have the highest electrical conductivity, lack sufficient strength, heat resistance, and brazing properties. They soften significantly at temperatures above 100℃, making them unsuitable for brazing and service in environments above 200℃. Therefore, developing a heat-resistant magnesium alloy that simultaneously possesses high strength, toughness, high conductivity, and brazing capability is an important direction for lightweight development in fields such as radar and microwave signal transmission in aerospace, transportation, and weaponry.

[0005] Table 1. Performance comparison of existing magnesium alloy systems

[0006]

[0007]

[0008] Studies have shown that Mg-Zn alloys possess high strength and toughness. A traditional method involves adding rare earth elements to form special compounds with Mg and Zn. These compounds exhibit heat-resistant properties, improving the material's thermal performance. However, they significantly reduce the alloy's electrical conductivity, severely inhibiting signal transmission efficiency and making them unsuitable for signal transmission components. For example:

[0009] Patent CN116657009A discloses "a high-strength, high-thermal-conductivity magnesium alloy and its preparation method," with the following composition by weight percentage: Zn: 5.0–8.0%; Cu: 0.5–3.0%; Zr: 0.1–1%; Mn: 0–1%; Sr: 0–1%; La: 0.5–3%; Ce: 0.5–3%, with the balance including Mg and unavoidable impurities. The study only addresses the thermal conductivity, yield strength, and elongation of the magnesium alloy material, without disclosing technical solutions or content on how to improve the electrical conductivity and high-temperature performance of the magnesium alloy. Furthermore, the aforementioned magnesium alloy is mainly processed using semi-solid thixotropic injection molding technology, belonging to the field of cast magnesium alloys, and cannot be used for plastic deformation. Its microstructure and properties are far inferior to wrought magnesium alloys, making it unsuitable for structural components such as signal transmission parts.

[0010] The electrical conductivity results on page 38 of Dai Xiaoteng's master's thesis "Study on Thermal Conductivity of Mg-6Zn-xCe Alloy [D]" published by Beijing General Research Institute of Nonferrous Metals in 2022 show that the addition of 0.5, 1.0, and 1.5 wt.% Ce to Mg-6Zn alloy caused its electrical conductivity to decrease from 19.0 to 18.5, 18.1, and 17.8, respectively, which seriously affected the electrical conductivity of the alloy.

[0011] The electrical conductivity of Mg-6Zn-3Sn-xCu (x=0, 0.5, 1, 1.5wt.%) alloys, as published on page 108 of Liu Yanhui's 2022 doctoral dissertation "Study on Microstructure Regulation, Mechanical Properties and Electromagnetic Shielding Performance of Mg-Zn-Sn-Cu Alloy [D]" at the Beijing General Research Institute of Nonferrous Metals, is 12.2, 12.5, 12.7 and 13 MS / m, respectively. The low electrical conductivity indicates that adding Sn to Mg-Zn alloys leads to a significant decrease in their electrical conductivity.

[0012] Currently, there are no publicly available patents or articles on high-strength, high-toughness, high-conductivity, and heat-resistant magnesium alloys. Therefore, providing a magnesium alloy that simultaneously possesses high strength and toughness (mechanical properties), high conductivity, heat resistance (can be used at high temperatures up to 200°C), and brazing capability will be of great significance for expanding the application of magnesium alloys. Summary of the Invention

[0013] To address the aforementioned problems, this invention aims to provide a heat-resistant magnesium alloy possessing high strength, toughness, high electrical conductivity, and brazing capability, along with its preparation and processing method. In the Mg-Zn-Mn-Cu-Ag-Ca magnesium alloy, by introducing elements such as Zn, Cu, Ag, Ca, and Mn, and utilizing deformation processes such as forging, extrusion, and rolling, as well as aging treatment, the alloy simultaneously possesses high strength, toughness, high electrical conductivity, brazing capability, and heat resistance.

[0014] This application prepares magnesium alloys by adding alloying elements, which has little impact on the conductivity of magnesium and can also form a high-temperature stable phase, improving the heat resistance of the alloy. Combined with multi-directional forging blanking and extrusion / rolling / forging and other combined deformation methods, the strength and toughness of the alloy are greatly improved, and ultimately a high-strength, high-toughness, high-conductivity, brazable heat-resistant magnesium alloy can be developed.

[0015] This application provides a heat-resistant magnesium alloy that is high in strength and toughness, high in electrical conductivity and brazing-compatible. By mass percentage, the magnesium alloy contains 5.0% to 8.0% Zn, 0.5% to 1.5% Mn, 0.5% to 3.5% Cu, 0.05% to 3.5% Ag, 0.01% to 1.5% Ca, and the balance is Mg.

[0016] In some preferred embodiments, the magnesium alloy contains 5.5-6.2% Zn, 0.8-1.2% Mn, 1.0-1.5% Cu, 0.1-1% Ag, 0.1-0.5% Ca, and the balance is Mg.

[0017] In some preferred embodiments, the impurity content in the magnesium alloy is ≤0.003%; in some more preferred embodiments, the Fe impurity content in the magnesium alloy is ≤0.003%.

[0018] Zn: Zn is the main strengthening element in alloys. Its maximum solid solubility in magnesium matrix is ​​6.2 wt.%, and the solid solubility decreases sharply with decreasing temperature, reaching almost zero at room temperature. Therefore, Zn can be used for age strengthening. Its age-determined phase MgZn2 is coherent with the matrix, resulting in good strengthening effect. Moreover, the atomic radius of Zn is close to that of magnesium, and the lattice distortion caused by solid solution in the matrix is ​​small, which has little impact on electrical conductivity. Zn is the most ideal main alloying element for achieving high strength, toughness and high electrical conductivity in magnesium alloys.

[0019] Mn: Mn does not form compounds with Mg or Zn. It precipitates rapidly at high temperatures. The precipitated phase exists in elemental form and is not coherent with the matrix. It has little effect on the conductivity of Mg and mainly plays the role of dynamic recrystallization nucleation core and grain refinement.

[0020] Cu: Cu has low solid solubility in magnesium matrix and provides a lot of free electrons for conduction. It can react with Zn to form MgCuZn phase. This phase has high conductivity and a heat resistance temperature of up to 420℃. It is distributed on the grain boundaries and can improve the conductivity, heat resistance and brazing properties of Mg-Zn alloys.

[0021] Ag: Ag forms the MgZnAg phase with the Mg and Zn matrix, which can further improve the electrical conductivity, heat resistance and brazing properties of Mg-Zn alloys. However, it should not be used in excess, as excessive use will consume Zn, reduce alloy strength, decrease corrosion resistance and significantly increase material costs.

[0022] Ca: Ca is a trace element that improves high-temperature performance, has little effect on electrical conductivity, promotes the precipitation of the strengthening phase MgZn2 second phase, and at the same time plays a role in refining alloy grains. It plays an important role in improving the strength, toughness, heat resistance and brazingability of the alloy.

[0023] Another objective of this invention is to provide the above-mentioned heat-resistant magnesium alloy with high strength, toughness, high electrical conductivity, and brazing capability, as well as its preparation and processing methods, to obtain heat-resistant magnesium alloy deformable materials with high strength, toughness, high electrical conductivity, and brazing capability.

[0024] In addition, this application also provides a method for preparing a heat-resistant magnesium alloy that combines high strength, toughness, high electrical conductivity, and brazing capability, comprising the following steps:

[0025] 1) Material preparation:

[0026] The materials are prepared according to the components described in claim 1, wherein magnesium, Zn, Cu, Ag, and Ca are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride; and the materials are preheated at 200℃~250℃ for 2~4 hours or more.

[0027] 2) Add alloying elements in stages during melting:

[0028] Magnesium is completely melted at 650–750°C;

[0029] Raise the temperature to 815–845°C, preferably 830°C, and add Cu and Ag sequentially until all of them are melted.

[0030] Lower the temperature to 785-815℃, preferably 800℃, and add anhydrous manganese chloride and Ca element in sequence until all is melted.

[0031] Lower the temperature to 685-715℃, preferably 700℃, add pure Zn, and stop heating after the alloy has melted completely;

[0032] Adding alloying elements in this order involves first melting the high-melting-point alloying elements (Cu and Ag), then adding Mn and Ca to ensure a uniform distribution of elemental Mn and Ca in the alloy melt, followed by the addition of Zn. The advantages of this order are twofold: firstly, it reduces the loss of Zn (which has the lowest melting point); secondly, by controlling the temperature to control the amount of compounds formed between Zn and Cu and Ag, it minimizes excessive Zn consumption, thus ensuring the alloy's strength, toughness, and performance.

[0033] 3) Casting: The melt obtained in step 2) is allowed to stand for 30-40 minutes. When the melt temperature drops to 650℃±10℃, it is semi-continuously cast into an ingot. Before casting, the melt is purified. The purification process adopts an adsorption filtration method.

[0034] The melt is transferred to the crystallizer using a transfer pump and then semi-continuously cast into ingots. Forced adsorption filtration is performed during the transfer process. A multi-stage adsorption filtration device is installed at the transfer pump inlet to purify the melt.

[0035] The multi-stage adsorption filtration device consists of a filter screen and multiple layers of MgO ceramic particles. When the melt passes through the filtration device, a forced filtration channel is formed to purify the melt.

[0036] In some preferred embodiments, the ingot is machined to remove the skin, riser, and bottom, resulting in an ingot with good surface quality.

[0037] 4) Homogenization heat treatment:

[0038] The ingot is subjected to homogenization heat treatment at a temperature of 320–390℃ for 10–40 hours.

[0039] In some preferred embodiments, step 4) involves a homogenization heat treatment process that may be single-stage or multi-stage. This forms a supersaturated solid solution, with the unremelted thermally stable phase dispersed within the matrix, preparing the microstructure for subsequent deformation and aging toughening.

[0040] 5) Combined plastic deformation:

[0041] The ingot after homogenization heat treatment is forged into a blank and then combined and deformed to obtain the forging product;

[0042] The forging temperature is 300-390℃; after forging, the ingot has a uniform and fine structure, and its plastic deformation capacity is improved.

[0043] The combined deformation is selected from any one or more of the following groups: extrusion, rolling, forging;

[0044] The forgings are selected from any one of the following groups: plates, pipes, profiles, bars, and wires;

[0045] The temperature of the combined deformation is 300–390°C;

[0046] The residual heat after forging can be used for combined extrusion / rolling / forging deformation, or the forged billet can be machined into the billet shape for the next process before being subjected to extrusion / rolling / forging deformation; combined deformation is the key process to achieve strength and toughness.

[0047] 6) Quenching:

[0048] The quenching includes online quenching and / or offline quenching; the offline quenching temperature is 350-400℃, and the holding time is 1.5-2 hours.

[0049] 7) Cold deformation eliminates residual stress:

[0050] Cold deformation eliminates residual stress; pre-stretching or forging cold deformation, with a deformation amount of 1-2%; while eliminating quenching residual stress, it also increases dislocation density, preparing the microstructure for the next toughening process.

[0051] 8) Aging-enhancing treatment:

[0052] After holding at 80-100℃ for 1-24 hours, increase the temperature to 160-220℃ and hold for 12-96 hours.

[0053] In some preferred embodiments, a gas is used for protection in step 2) and / or step 3); the gas is a mixture of argon and tetrafluoroethane in a volume ratio of 15 to 20:1.

[0054] In some preferred embodiments, the stirring state is maintained in step 2); preferably, mechanical stirring and / or electromagnetic stirring are used;

[0055] In some preferred embodiments, scum is continuously removed in step 2).

[0056] After ultrasonic or X-ray non-destructive testing of the final product, the magnesium alloy has a tensile strength ≥360MPa, elongation ≥10%, conductivity ≥19MS / m, tensile strength at 200℃ ≥200MPa, and a decrease in tensile strength of the base material ≤10% after brazing at 350~450℃.

[0057] Beneficial effects:

[0058] 1. By adding Zn, Cu, Mn, Ag, and Ca elements, various thermally stable phases such as MgZnCu, MgZnAg, and MgCaZn are formed, and the composition and content of these phases are controlled. These phases are distributed at grain boundaries, are incoherent with the matrix, and have little impact on the electrical conductivity of the alloy. Moreover, these phases themselves have high electrical conductivity density. These microstructural features solve the problem of the mutual incompatibility between high electrical conductivity and heat resistance of magnesium alloys, ensuring that the alloy maintains high electrical conductivity while possessing heat resistance and brazing properties. Through a combination of various deformation processes, high strength and toughness mechanical properties are obtained, enabling the magnesium alloy to simultaneously possess high strength, toughness, high electrical conductivity, brazing properties, and heat resistance.

[0059] 2. The magnesium alloy material can simultaneously achieve the following indicators: tensile strength ≥360MPa, elongation ≥10%, conductivity ≥19MS / m, tensile strength at 200℃ ≥200MPa, and tensile strength decrease of ≤10% after brazing at 350~450℃. This allows the magnesium alloy to possess high strength and toughness and high conductivity, while also being able to be brazed into complex cavity components that integrate load-bearing and conductive functions, and to be able to serve in an environment of 200℃.

[0060] 3. The magnesium alloy material has extremely important application value in electronic signal and microwave signal transmission components in aerospace, transportation, weaponry and other fields. Attached Figure Description

[0061] Figure 1 Typical microstructure diagram of Mg-Zn-Mn-Cu-Ag-Ca alloy;

[0062] Figure 2 This is a typical microstructure diagram of a Mg-Zn-Mn-Cu-Ag-Ca alloy after homogenization treatment;

[0063] Figure 3 This is a tissue diagram for Comparative Example 1;

[0064] Figure 4 This is a tissue diagram after homogenization treatment in Comparative Example 1. Detailed Implementation

[0065] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0066] This invention provides a heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability, which is prepared and processed through the following steps: material preparation, raw material preheating, smelting, purification treatment, homogenization heat treatment, multi-directional forging, plastic processing, residual stress reduction, and toughening aging treatment.

[0067] 1) Material preparation: Prepare materials according to the components described in claim 1, with Mg, Zn, Cu, Ag and Ca elements added in the form of pure metals, and Mn added in the form of anhydrous manganese chloride; preheat at 200℃~250℃ for more than 2~4 hours respectively;

[0068] 2) Stepwise melting: At 650–850℃, melt Mg, Cu, Ag, anhydrous manganese chloride, Ca, and Zn in sequence; stop heating after the alloy has melted completely.

[0069] Magnesium ingots are completely melted under a protective gas atmosphere at a temperature controlled between 650 and 750°C, with slag removal performed multiple times during the process. Once the magnesium is completely melted, the temperature of the alloy melt is raised to 830°C ± 15°C, and Cu and Ag elements are added sequentially. The melt is mechanically / electromagnetically stirred until all alloying elements have melted. The temperature is then lowered to 800°C ± 15°C, and anhydrous manganese chloride and Ca elements are added sequentially. The melt is mechanically / electromagnetically stirred until all alloying elements have melted. Finally, the temperature is lowered to 700°C ± 15°C, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy has melted completely, the power is turned off to stop heating.

[0070] 3) Ingot Casting: The melt obtained in step 2) is allowed to stand for 30-40 minutes. When the melt temperature drops to 640℃-660℃, the melt is transferred to a crystallizer using a transfer pump for semi-continuous casting to prepare an ingot. Forced adsorption filtration is performed during the transfer process. The ingot is then machined to remove the skin, risers, and bottom, resulting in an ingot with good surface quality. The typical alloy microstructure is as follows: Figure 1 As shown;

[0071] 4) Homogenization heat treatment: The ingot is subjected to homogenization heat treatment at a temperature of 320–390℃ for 10–40 hours. The homogenized alloy microstructure is as follows: Figure 2 As shown;

[0072] 5) Combined plastic deformation: The ingot after homogenization heat treatment is forged and then subjected to combined deformation to obtain the forging product;

[0073] 6) Quenching: The quenching includes online quenching and / or offline quenching;

[0074] 7) Cold deformation to eliminate residual stress: Cold deformation eliminates residual stress, pre-stretching or forging cold deformation, with a deformation amount of 1-2%;

[0075] 8) Aging and toughening treatment: Keep at 80-220℃ for 1-96 hours.

[0076] Example 1:

[0077] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 6.0%, Mn 1%, Cu 0.5%, Ag 0.5%, Ca 0.3%, and the balance Mg. The alloy is prepared according to the following steps:

[0078] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0079] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0080] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0081] (4) The ingot is subjected to homogenization heat treatment at a temperature of 370℃ and held for 12 hours.

[0082] (5) Multi-directional forging of the ingot and direct extrusion, forging and extrusion temperature 350℃, extrusion ratio 15:1;

[0083] (6) Online quenching;

[0084] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 2%;

[0085] (8) T5 aging treatment was used to obtain extruded sheets, with an aging regime of 90℃×12h+180℃×36h.

[0086] Example 2:

[0087] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 6.0%, Mn 1%, Cu 1.0%, Ag 0.5%, Ca 0.3%, and the balance Mg. The alloy is prepared according to the following steps:

[0088] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0089] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0090] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0091] (4) The ingot is subjected to homogenization heat treatment at a temperature of 370℃ and held for 12 hours.

[0092] (5) Multi-directional forging and direct extrusion of the ingot, forging and extrusion temperature 350℃, extrusion ratio 15:1;

[0093] (6) Online quenching;

[0094] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 2%;

[0095] (8) T5 aging treatment was used to obtain extruded sheets, with an aging regime of 90℃×12h+180℃×36h.

[0096] Example 3:

[0097] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 6.0%, Mn 1%, Cu 1.5%, Ag 0.5%, Ca 0.3%, and the balance Mg. The alloy is prepared according to the following steps:

[0098] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0099] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0100] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0101] (4) The ingot is subjected to homogenization heat treatment at a temperature of 370℃ and held for 12 hours.

[0102] (5) Multi-directional forging and direct extrusion of the ingot, forging and extrusion temperature 350℃, extrusion ratio 15:1;

[0103] (6) Online quenching;

[0104] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 2%;

[0105] (8) T5 aging treatment was used to obtain extruded sheets, with an aging regime of 90℃×12h+180℃×36h.

[0106] Example 4:

[0107] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 8.0%, Mn 1%, Cu 0.5%, Ag 3.0%, Ca 0.1%, and the balance Mg. The alloy is prepared according to the following steps:

[0108] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0109] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0110] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0111] (4) The ingot is subjected to homogenization heat treatment at a temperature of 370℃ and held for 12 hours.

[0112] (5) The ingot is subjected to multi-directional forging and direct rolling. The forging and rolling temperature is 370℃ and the rolling reduction is 30%.

[0113] (6) Online quenching;

[0114] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 2%;

[0115] (8) T5 aging treatment to obtain rolled plates, aging regime 100℃×12h+170℃×30h.

[0116] Example 5:

[0117] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 5.0%, Mn 0.5%, Cu 0.5%, Ag 0.05%, Ca 0.01%, and the balance Mg. The alloy is prepared according to the following steps:

[0118] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0119] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0120] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0121] (4) The ingot is subjected to homogenization heat treatment at a temperature of 370℃ and held for 12 hours.

[0122] (5) Multi-directional forging and direct extrusion of the ingot, forging and extrusion temperature 370℃, extrusion ratio 20:1;

[0123] (6) Online quenching;

[0124] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 2%;

[0125] (8) T5 aging treatment was used to obtain extruded bars, with an aging regime of 90℃×24h+200℃×60h.

[0126] Example 6:

[0127] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 5.0%, Mn 1.5%, Cu 3.5%, Ag 3.5%, Ca 1.5%, and the balance Mg. The alloy is prepared according to the following steps:

[0128] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0129] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0130] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0131] (4) The ingot is subjected to homogenization heat treatment, and the heat treatment regime is 340℃×12h+370℃×8h;

[0132] (5) Multi-directional forging and direct extrusion of the ingot, forging and extrusion temperature 370℃, extrusion ratio 20:1;

[0133] (6) Online quenching;

[0134] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 2%;

[0135] (8) T5 aging treatment yields extruded pipes, with an aging regime of 90℃×10h+200℃×72h.

[0136] Example 7:

[0137] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 6.2%, Mn 1%, Cu 1.5%, Ag 1%, Ca 0.5%, and the balance Mg. The alloy is prepared according to the following steps:

[0138] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0139] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0140] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0141] (4) The ingot is subjected to homogenization heat treatment, and the heat treatment regime is 320℃×24h+380℃×6h;

[0142] (5) Multi-directional forging and direct extrusion of the ingot, forging and extrusion temperature 360℃, extrusion ratio 20:1;

[0143] (6) Online quenching;

[0144] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 3%;

[0145] (8) T5 aging treatment was used to obtain extruded sheets, with an aging regime of 90℃×10h+180℃×72h.

[0146] Example 8:

[0147] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 8.0%, Mn 1.5%, Cu 3.5%, Ag 3.5%, Ca 1.5%, and the balance Mg. The alloy is prepared according to the following steps: Mg-8.0Zn-1.5Mn-3.5Cu-3.5Ag-1.5Ca

[0148] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0149] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0150] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0151] (4) The ingot is subjected to homogenization heat treatment, and the heat treatment regime is 320℃×24h+370℃×12h;

[0152] (5) Multi-directional forging and direct extrusion of the ingot, forging and extrusion temperature 370℃, extrusion ratio 30:1;

[0153] (6) Offline quenching, quenching regime 370℃×2h;

[0154] (7) Pre-stretching cold deformation to eliminate residual stress, with a pre-stretching amount of 2%;

[0155] (8) T6 aging treatment was used to obtain extruded bars, with an aging regime of 90℃×12h+175℃×48h.

[0156] Example 9:

[0157] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 6.2%, Mn 1%, Cu 1%, Ag 0.5%, Ca 0.5%, and the balance Mg. The alloy is prepared according to the following steps:

[0158] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0159] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0160] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0161] (4) The ingot is subjected to homogenization heat treatment, and the heat treatment regime is 330℃×24h+370℃×4h;

[0162] (5) The ingot is subjected to multi-directional forging forging and direct forging at a forging temperature of 370℃;

[0163] (6) Offline quenching, quenching regime: 390℃×2h;

[0164] (7) Cold deformation eliminates residual stress, with a cold deformation amount of 2%;

[0165] (8) The forging was obtained by T6 aging treatment, with an aging regime of 90℃×10h+180℃×48h.

[0166] Example 10:

[0167] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 5.5%, Mn 1%, Cu 1.5%, Ag 0.5%, Ca 0.5%, and the balance Mg. The alloy is prepared according to the following steps:

[0168] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0169] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0170] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0171] (4) The ingot is subjected to homogenization heat treatment, and the heat treatment regime is 330℃×24h+370℃×8h;

[0172] (5) The ingot is subjected to multi-directional forging forging and direct forging at a forging temperature of 370℃;

[0173] (6) Offline quenching, quenching regime: 390℃×4h;

[0174] (7) Cold deformation eliminates residual stress, with a cold deformation amount of 2%;

[0175] (8) The forging was obtained by T6 aging treatment, with an aging regime of 90℃×8h+190℃×48h.

[0176] Example 11:

[0177] The selected alloy is a Mg-Zn-Mn-Cu-Ag-Ca alloy, with the following mass percentages: Zn 6.2%, Mn 1%, Cu 0.5%, Ag 1.5%, Ca 0.3%, and the balance Mg. The alloy is prepared according to the following steps:

[0178] (1) Prepare the ingredients according to the alloy composition requirements. Mg, Zn, Cu, Ag and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. Preheat Mg ingots, pure Zn, Cu, Ag, Ca and anhydrous manganese chloride in the furnace at 200℃~250℃ for more than 2 hours to prepare for smelting.

[0179] (2) The magnesium ingot is completely melted under the protection of a protective gas, and the temperature is controlled at 650-750℃. During this period, slag is removed multiple times. After the magnesium is completely melted, the temperature of the alloy melt is raised to 835℃, and Cu and Ag elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 815℃, and anhydrous manganese chloride and Ca elements are added in sequence. The melt is mechanically / electromagnetically stirred until all the alloy elements are melted. The temperature is lowered to 710℃, and pure Zn is added. The melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0180] (3) Slag removal is carried out during the stirring process. A multi-stage adsorption and filtration device is set in the transfer pump. After standing for 30 minutes, when the melt temperature drops to 650℃, the melt is transferred to the crystallizer for semi-continuous casting to prepare ingots. The ingot is machined to remove the skin, riser and bottom, and ingots with good surface quality are obtained.

[0181] (4) The ingot is subjected to homogenization heat treatment, and the heat treatment regime is 330℃×24h+390℃×4h;

[0182] (5) Multi-directional forging of the ingot, machining into a hollow ingot, heating and extrusion, forging temperature 370℃, heating temperature before extrusion 370℃×4h, extrusion ratio 28:1.

[0183] (6) Offline quenching, quenching regime: 370℃×4h;

[0184] (7) Cold deformation eliminates residual stress, with a cold deformation amount of 2%;

[0185] (8) T6 aging treatment was used to obtain pipes, with an aging regime of 90℃×10h+200℃×48h.

[0186] Table 2. Relevant properties of magnesium alloys prepared in Examples 1-11

[0187]

[0188]

[0189] As can be seen from Table 1, the magnesium alloys of Examples 1 to 11 obtained using the magnesium alloy composition and preparation method of this application have tensile strengths of 362 to 395 MPa, elongation of 10 to 15%, electrical conductivity ≥ 19.2 to 21.0 MS / m, high-temperature tensile strength at 200℃ ≥ 201 to 246 MPa, and strength decrease of 3% to 10% after holding at a brazing temperature of 350 to 450℃ for 10 minutes. The magnesium alloy of this invention simultaneously possesses the properties of high strength and toughness, high electrical conductivity, brazing capability, and heat resistance (high-temperature service).

[0190] Comparative Example 1: Differences in the order of feeding materials

[0191] Based on Example 2, the melting and feeding sequence in step (2) was changed, while the content of other components and the preparation steps were the same as those in Comparative Example 2, and a comparative experiment was conducted.

[0192] Step (2) of Comparative Example 1: The magnesium ingot was completely melted under the protection of a protective gas, and the temperature was controlled at 700±15℃. Slag was removed multiple times during the process. After the magnesium was completely melted, the temperature was raised to 710℃, pure Zn was added, and the melt was mechanically / electromagnetically stirred. The temperature was raised to 815℃, anhydrous manganese chloride and Ca were added in sequence, and the melt was mechanically / electromagnetically stirred. The temperature was raised to 835℃, Cu and Ag were added in sequence, and the melt was mechanically / electromagnetically stirred until all the alloying elements were completely melted.

[0193] Table 3. Relevant Properties of Magnesium Alloys: Differences in Feeding Sequence

[0194]

[0195]

[0196] Results analysis:

[0197] The results of Comparative Example 1 show that when the order of element addition is adjusted, the Zn burn-off increases, and the amount of MgCuZn and MgAgZn phases in the alloy also increases. Figure 3 This leads to a large consumption of Zn, and these phases cannot be re-dissolved during homogenization, remaining continuously distributed at the grain boundaries. Figure 4 This ultimately leads to a rapid decline in the alloy's strength, toughness, and electrical conductivity, making it unable to meet service requirements.

[0198] The above comparison shows that by adopting the feeding sequence of this application, the room temperature tensile strength is increased by more than 8%, the elongation is increased by 100%, the electrical conductivity is increased by about 10%, and the high temperature tensile strength at 200℃ is increased by about 14%. The mechanical properties, electrical conductivity, and high temperature resistance of the magnesium alloy material are significantly improved. Furthermore, the reduction rate of tensile strength after brazing is significantly reduced by 37.5%, and the brazingability is significantly improved.

[0199] Comparative Examples 2-3: Differences in Magnesium Alloy Composition

[0200] Based on Example 5, the composition of the magnesium alloy was changed, while other preparation processes remained unchanged.

[0201] Comparative Example 2:

[0202] The Zn content was reduced, and the alloy composition is as follows: by mass percentage, Zn content is 4.0%, Mn content is 0.5%, Cu content is 0.5%, Ag content is 0.05%, Ca content is 0.01%, and the balance is Mg.

[0203] Comparative Example 3:

[0204] The Zn content was increased, resulting in a Mg-Zn-Mn-Cu-Ag-Ca alloy. By mass percentage, the Zn content was 8.5%, the Mn content was 1.5%, the Cu content was 3.5%, the Ag content was 3.5%, the Ca content was 1.5%, and the balance was Mg.

[0205] Table 4. Relevant Properties of Magnesium Alloys: Compositional Differences in Magnesium Alloys

[0206]

[0207] The above comparison shows that the Zn content in this application is 5.0% to 8.0%, for example, 5.0% in Example 5. Comparative Example 2 shows that when the mass percentage of the main element Zn is less than 5.0% (e.g., 4.0% in Comparative Example 2), the strength and heat resistance decrease. Specifically, the tensile strength at room temperature and 200°C decreases by about 20-30 MPa compared to Example 5, and the tensile strength of the body after brazing decreases by as much as 15%, failing to meet the requirements for strength and heat resistance. When the mass percentage of the main element Zn exceeds 8.0% (e.g., 8.5% in Comparative Example 3), the electrical conductivity decreases to below 18.0 MS / m, and the elongation also decreases rapidly (more than 60% lower than in Example 5), also failing to meet the requirements for high electrical conductivity and high toughness.

[0208] Comparative Example 4: Differences in Magnesium Alloy Composition

[0209] Based on Example 1, Cu and Ag elements are omitted.

[0210] The selected alloy is a Mg-Zn-Mn-Ca alloy, with a Zn content of 6.0%, a Mn content of 1%, a Ca content of 0.3%, and the balance being Mg by mass percentage. Step (2) the melting process is as follows:

[0211] Magnesium ingots are completely melted under the protection of a protective gas, with the temperature controlled at 650–750°C, and slag is removed multiple times during the process. When the temperature is raised to 815°C, anhydrous manganese chloride and Ca are added in sequence, and the melt is mechanically / electromagnetically stirred until all alloying elements are completely melted. When the temperature is lowered to 710°C, pure Zn is added, and the melt is mechanically / electromagnetically stirred. After the alloy is completely melted, the power is turned off and heating is stopped.

[0212] The other steps are the same as in Example 1.

[0213] Table 5. Relevant Properties of Magnesium Alloys: Compositional Differences in Magnesium Alloys

[0214]

[0215] Results analysis:

[0216] When Cu and Ag are not present, the alloy's strength, electrical conductivity, heat resistance, and brazing properties cannot meet the requirements.

[0217] When Mn and Ca are absent, the alloy cracks during deformation and cannot be formed.

[0218] Comparative Example 5:

[0219] Based on Example 1, the combined deformation forging blanking step in preparation process step (5) is omitted.

[0220] (5) Directly extrude the ingot at an extrusion temperature of 350°C and an extrusion ratio of 15:1; other steps are consistent with those in Example 1.

[0221] Table 6. Relevant Properties of Magnesium Alloys: Differences in Manufacturing Processes

[0222]

[0223] As can be seen from Comparative Example 5, without combined deformation, the room temperature mechanical properties, high temperature mechanical properties, and toughness of the alloy will decrease significantly, failing to meet service requirements.

[0224] Comparative Examples 6–9:

[0225] Based on Example 1, 1 wt.% of rare earth elements Gd, Ce, Sn, and Sc were added respectively.

[0226] Comparative Example 6, with the addition of Gd: The selected alloy is a Mg-Zn-Mn-Gd-Cu-Ag-Ca alloy, with Zn content of 6.0%, Mn content of 1%, Gd content of 1%, Cu content of 0.5%, Ag content of 0.5%, Ca content of 0.3%, and the balance being Mg by mass percentage.

[0227] Comparative Example 7, with the addition of Ce element: The selected alloy is a Mg-Zn-Mn-Ce-Cu-Ag-Ca alloy, with Zn content of 6.0%, Mn content of 1%, Ce content of 1%, Cu content of 0.5%, Ag content of 0.5%, Ca content of 0.3%, and the balance being Mg by mass percentage.

[0228] Comparative Example 8, with the addition of Sn element: The selected alloy is a Mg-Zn-Mn-Sn-Cu-Ag-Ca alloy, with Zn content of 6.0%, Mn content of 1%, Sn content of 1%, Cu content of 0.5%, Ag content of 0.5%, Ca content of 0.3%, and the balance being Mg by mass percentage.

[0229] Comparative Example 9, with the addition of Sc element: The selected alloy is a Mg-Zn-Mn-Sc-Cu-Ag-Ca alloy, with Zn content of 6.0%, Mn content of 1%, Sc content of 1%, Cu content of 0.5%, Ag content of 0.5%, Ca content of 0.3%, and the balance being Mg by mass percentage.

[0230] The melting process in step (2) is as follows:

[0231] Magnesium ingots were completely melted under a protective gas atmosphere at a temperature controlled between 650 and 750°C, with slag removal performed multiple times during the process. When the temperature was raised to 815°C, anhydrous manganese chloride and Ca were added sequentially, and the melt was mechanically / electromagnetically stirred until all alloying elements were completely melted. Gd, Ce, Sn, and Sc were added to different comparative proportions. When the temperature was lowered to 710°C, pure Zn was added, and the melt was mechanically / electromagnetically stirred. After the alloy was completely melted, the power was turned off and heating was stopped.

[0232] The other steps are the same as in Example 1.

[0233] Table 7. Relevant Properties of Magnesium Alloys: Compositional Differences in Magnesium Alloys

[0234]

[0235]

[0236] Results analysis:

[0237] When 1 wt.% of rare earth elements Gd, Ce, Sn, and Sc are added respectively, the most obvious effect is a significant decrease in electrical conductivity. This is because the atomic radii of these elements are much different from those of magnesium atoms, resulting in huge lattice distortion in the magnesium matrix. This leads to greater obstruction of electron transport, causing the alloy's electrical conductivity to drop rapidly. Therefore, these elements cannot be found in high-strength, high-toughness, high-conductivity, brazable, and heat-resistant magnesium alloys.

Claims

1. A heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability, wherein the magnesium alloy comprises, by mass percentage: 5.0%~8.0% Zn, 0.5%~1.5% Mn, 0.5%~3.5% Cu, 0.05%~3.5% Ag, 0.01%~1.5% Ca, and the balance being Mg; The Mg, Zn, Cu, Ag, and Ca elements are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride. During preparation, the mixture is preheated at 200℃~250℃ for 2~4 hours or more. Then, Mg, Cu, Ag, anhydrous manganese chloride, Ca, and Zn are melted sequentially at 650~850℃. Heating is stopped after the alloy is completely melted. The magnesium alloy has a tensile strength ≥360MPa, elongation ≥10%, conductivity ≥19MS / m, tensile strength at 200℃ ≥200MPa, and a decrease in tensile strength of the base material ≤10% after brazing at 350~450℃.

2. A heat-resistant magnesium alloy with high strength, high toughness, high conductivity, and brazing capability according to the preceding claims, wherein the magnesium alloy has the following composition: Zn content of 5.5~6.2%, Mn content of 0.8~1.2%, Cu content of 1.0~1.5%, Ag content of 0.1~1%, Ca content of 0.1~0.5%, and the balance being Mg.

3. A method for preparing a heat-resistant magnesium alloy with high strength, toughness, high electrical conductivity, and brazing capability as described in any of the preceding claims, comprising the following steps: 1) Material preparation: The materials are prepared according to the components described in claim 1 or 2, wherein Mg, Zn, Cu, Ag, and Ca are added in the form of pure metals, and Mn is added in the form of anhydrous manganese chloride; and the materials are preheated at 200℃~250℃ for 2~4 hours or more. 2) Step-by-step melting: Under conditions of 650~850℃, Mg, Cu, Ag, anhydrous manganese chloride, Ca, and Zn are melted in sequence; heating is stopped after the alloy has melted completely. 3) Casting: Let the melt obtained in step 2) stand for 30 to 40 minutes. When the melt temperature drops to 640℃ to 660℃, prepare the ingot by semi-continuous casting. 4) Homogenization heat treatment: The ingot is subjected to homogenization heat treatment at a temperature of 320~390℃ for 10~40h. 5) Combined plastic deformation: The homogenized heat-treated ingot is forged into a blank and then combined and deformed to obtain the finished product. 6) Quenching: The quenching includes online quenching or offline quenching; 7) Cold deformation eliminates residual stress: Cold deformation eliminates residual stress; pre-stretching or forging cold deformation, with a deformation amount of 1~2%. 8) Aging-enhancing treatment: Keep warm at 80~220℃ for 1~96 hours.

4. The method for preparing a heat-resistant magnesium alloy with high strength, toughness, high electrical conductivity, and brazing capability according to claim 3, wherein, The forging and / or combined deformation temperature is 300~390℃.

5. The method for preparing a heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability according to claim 3, wherein, The combined deformation is selected from any one or more of the following groups: extrusion, rolling, forging.

6. The method for preparing a heat-resistant magnesium alloy with high strength, toughness, high electrical conductivity, and brazing capability according to claim 3, wherein, The melting process in step 2) is as follows: Magnesium is completely melted at 650~750℃; Raise the temperature to 815~845℃, and add Cu and Ag in sequence until they are completely melted; Lower the temperature to 785~815℃, and add anhydrous manganese chloride and Ca element in sequence until it is completely melted. Reduce the temperature to 685~715℃, add pure Zn, and stop heating after the alloy has melted completely.

7. The method for preparing a heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability according to claim 3, wherein, The aging and toughening treatment is carried out in stages, with the following steps: heat treatment at 80~100℃ for 1~24h, and then increase the temperature to 160~220℃ and heat treatment for 12~96h.

8. The method for preparing a heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability according to claim 3, wherein, The offline quenching temperature is 350~400℃, and the holding time is 1.5~2h.

9. The method for preparing a heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability according to claim 3, wherein, In step 2) and / or step 3), a gas is used for protection; the gas is a mixture of argon and tetrafluoroethane, with a volume ratio of 15~20:

1.

10. The method for preparing a heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability according to claim 3, wherein, In step 2), the stirring process is maintained.

11. The method for preparing a heat-resistant magnesium alloy with high strength, high toughness, high electrical conductivity, and brazing capability according to claim 10, wherein, Step 2) involves mechanical stirring and / or electromagnetic stirring.

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