High-toughness corrosion-resistant Mg-Al-Zn series magnesium alloy and preparation method thereof

Abstract

The application provides a high-strength and high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy and a preparation method thereof, and belongs to the technical field of magnesium alloy materials, and solves the technical problem that traditional magnesium alloys cannot be considered in terms of strength, corrosion resistance and formability in the prior art. The high-strength and high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy comprises the following components in percentage by weight: Al: 4.00% to 6.00%, Zn: 0.80% to 1.00%, Sc: 1.60% to 2.00%, Mn: 0.15% to 0.50%, and the balance of Mg and inevitable impurities. The Mg-Al-Zn magnesium alloy has a neutral salt spray test weight loss corrosion rate of 3 to 5 mm / y, a yield strength of 170 to 180 MPa, a tensile strength of 320 to 330 MPa, and an elongation of 9 to 11%, and has high strength and toughness and corrosion resistance, and can be applied to service parts under severe environmental conditions and with high strength requirements.

Description

Technical Field

[0001] This invention belongs to the field of magnesium alloy materials technology, and relates to a high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy and its preparation method. Background Technology

[0002] With the widespread application of lightweight and high-performance materials in aerospace, automotive industry and electronic equipment, magnesium alloys have attracted increasing attention because their density is only 2 / 3 that of aluminum and 1 / 4 that of iron, making them one of the lightest structural metal materials currently available.

[0003] However, despite the unparalleled advantages of magnesium alloys in lightweighting, some inherent performance limitations cannot be ignored. For example, while traditional cast magnesium alloys offer good formability and low cost, they suffer from significant deficiencies in strength. Wrought magnesium alloys, on the other hand, while possessing high strength, suffer from high processing costs and limitations in forming shapes. Furthermore, the high reactivity and poor corrosion resistance of magnesium alloys restrict the widespread application of complex shapes or intricate structures in high-strength or harsh environmental conditions. For instance, in the aerospace field, aircraft must withstand extreme flight conditions and complex climatic environments, placing extremely stringent requirements on the strength, toughness, corrosion resistance, and formability of materials. In the automotive industry, with the rapid development of electric vehicles and autonomous driving technologies, the demand for lightweight materials is increasingly urgent, but these materials must also possess good collision safety performance and long-term corrosion resistance.

[0004] To overcome these shortcomings, it is particularly important to develop magnesium alloy materials with high strength, high corrosion resistance, and the ability to meet complex forming requirements. Summary of the Invention

[0005] In view of the above-mentioned current technical situation, this invention proposes a high-strength, high-toughness, and corrosion-resistant Mg-Al-Zn magnesium alloy and its preparation method, which solves the technical problem that traditional magnesium alloys cannot simultaneously achieve strength, corrosion resistance, and formability. This is mainly achieved through the following technical solutions: On the one hand, the present invention provides a high-strength, tough and corrosion-resistant Mg-Al-Zn magnesium alloy, wherein the magnesium alloy composition by weight percentage is: Al: 4.00%~6.00%, Zn: 0.80%~1.00%, Sc: 1.60%~2.00%, Mn: 0.15%~0.50%, with the balance being Mg and unavoidable impurities.

[0006] Furthermore, the magnesium alloy composition by weight percentage is: Al: 5.00%, Zn: 0.90%, Sc: 1.80%, Mn: 0.30%, with the balance being Mg and unavoidable impurities.

[0007] On the other hand, the present invention also provides a method for preparing the above-mentioned magnesium alloy, comprising the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, Al-Mn master alloy and Mg-Sc master alloy according to the weight percentage of the elements in the high-strength, tough and corrosion-resistant Mg-Al-Zn magnesium alloy. S2. Raw materials are put into an induction melting furnace, heated, stirred and kept warm under a protective atmosphere to obtain a melt; S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting, and obtain a magnesium alloy casting.

[0008] Furthermore, in step S1, the Al-Mn master alloy is Al-50Mn by weight percentage; the Mg-Sc master alloy is Mg-5Sc by weight percentage.

[0009] Furthermore, step S2 includes the following sub-steps: S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 710~730℃ under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at the temperature after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-Mn master alloy and Mg-Sc master alloy are added and completely melted into a melt, then stirred and kept at a constant temperature.

[0010] Furthermore, in steps S2.1 and S2.2, the heat preservation time is 8~12 minutes.

[0011] Furthermore, in step 3, the melt is kept at 720~730℃, and degassing is performed using a preheated rotary argon-blown graphite rotor. After degassing, the melt is kept at a constant temperature for 8~12 minutes.

[0012] Furthermore, the argon flow rate is 1~3L / min, and the degassing time is 10~15min.

[0013] Furthermore, in steps 2 and 3, the protective atmosphere is a mixture of SF6 and CO2, with the volume fraction of SF6 in the mixture being 0.5-1%.

[0014] Furthermore, in step S4, the preheating temperature of the pressure chamber is 100~150℃, the injection speed is 0.5~1.5m / s, the injection specific pressure is 80~150MPa, and the mold temperature is maintained at 150~250℃.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The Mg-Al-Zn magnesium alloy of the present invention, through composition design and processing optimization, achieves a weight loss corrosion rate of 3~5 mm / y, a yield strength of 170~180 MPa, a tensile strength of 320~330 MPa, and an elongation of 9~11% in a 7-day neutral salt spray test. It has both high strength and toughness and corrosion resistance, and can be used for service parts that are in harsh environments and have high strength requirements.

[0016] 2. The present invention uses the extrusion casting process, which not only makes the formed parts have fine grains, dense structure and low porosity, but also has a shorter and more stable process flow compared with the deformation process. It can form complex structural parts in one step and is suitable for mass production of complex parts at low cost. Attached Figure Description

[0017] Figure 1 The image shows the microstructure of the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy casting from Example 1. Detailed Implementation

[0018] The following detailed description, in conjunction with specific embodiments, provides a high-strength, high-toughness, and corrosion-resistant Mg-Al-Zn magnesium alloy and its preparation method. These embodiments are for illustrative purposes only, and the present invention is not limited to these embodiments.

[0019] On one hand, the present invention provides a high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, which, by weight percentage, comprises: Al: 4.00%~6.00%, Zn: 0.80%~1.00%, Sc: 1.60%~2.00%, Mn: 0.15%~0.50%, with the balance being Mg and unavoidable impurities. Impurities include, but are not limited to, one or more of Fe, Cu, and Ni.

[0020] The above-mentioned high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloys, after a 7-day neutral salt spray test, showed a weight loss corrosion rate of 3~5 mm / y, an alloy yield strength of 170~180 MPa, a tensile strength of 320~330 MPa, and an elongation of 9~11%.

[0021] It should be noted that Al forms Mg. 17 Al 12 The eutectic phase provides alloy fluidity and castability, pins dislocations, and improves the strength of magnesium alloys. Simultaneously, it forms an Al2O3 oxide film on the casting surface, increasing the alloy's corrosion resistance. However, excessive addition will result in excess Mg. 17 Al 12 Mg 17 Al 12 The presence of a hardened phase reduces the alloy's plasticity and elongation; therefore, this invention limits the Al content to 4.00%~6.00%.

[0022] Zn: Zn element is dissolved into the Mg alloy matrix to improve the strength of the magnesium alloy. It forms the ScZn phase with Sc to improve the strength of the alloy. At the same time, during the corrosion of Mg alloy, the ScZn phase will form a corrosion product protective film to improve the corrosion resistance of the alloy. Excessive addition will form coarse Zn-rich phase and reduce the mechanical properties of the alloy. Therefore, the Zn content is limited to 0.80%~1.00% in this invention.

[0023] Sc: The formation of the Al3Sc phase can act as a heterogeneous nucleation point for primary α-Mg grains, refining primary magnesium grains and improving the strength and toughness of the alloy. At the same time, the addition of Sc can inhibit Mg growth to a certain extent. 17 Al 12 Phase, and for Mg 17 Al 12 The phase refinement effect is achieved. In addition, Sc and Zn form the ScZn phase. During corrosion, the ScZn phase forms a protective film of corrosion products, which improves the corrosion resistance of the alloy. If the amount added is too large, the Al3Sc phase in the microstructure will be coarse, which will cut the matrix and reduce the mechanical properties of the alloy. Therefore, the Sc content is limited to 1.60%~2.00% in this invention.

[0024] Mn combines with Fe in the melt to form intermetallic compounds for impurity removal, increases the Fe content tolerance, improves the strength and plasticity of the alloy, and at the same time forms the Al8Mn5 phase to refine the primary α-Mg grains, improving the strength and toughness of the alloy. Excessive addition forms Mn-rich intermetallic phases, which reduces the mechanical properties of the alloy; therefore, this invention limits the Mn content to 0.15%~0.50%.

[0025] Further preferably, the above-mentioned high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy has the following composition by weight percentage: Al: 5.0%, Zn: 0.90%, Sc: 1.8%, Mn: 0.30%, with the balance being Mg and unavoidable impurities.

[0026] On the other hand, the present invention also provides a method for preparing the above-mentioned high-strength, high-toughness, and corrosion-resistant Mg-Al-Zn magnesium alloy, comprising the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-Mn and Mg-Sc master alloys according to the weight percentage of the elements in the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy. S2. Raw materials are fed into an induction melting furnace and heated, stirred and kept warm under a protective atmosphere to obtain a melt; S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 8-12 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting, and obtain a magnesium alloy casting.

[0027] In step S1, the weight percentages of each metal in the Al-Mn master alloy and the Mg-Sc master alloy are Al-50Mn and Mg-5Sc, respectively; Al-50Mn means that the weight percentage of Mn in the Al-Mn master alloy is 50%; Mg-5Sc means that the weight percentage of Sc in the Mg-Sc master alloy is 5%. Because the master alloys have lower melting points and faster dissolution rates, the composition of the prepared magnesium alloy is accurate and stable.

[0028] The specific steps of step S2 are as follows: S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 710~730℃ under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 8~12 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, add Al-Mn master alloy and Mg-Sc master alloy, and after completely melting into a melt, stir and keep warm for 8~12 minutes; Small amounts of SF6, such as 0.5-1% by volume, can form an effective protective film on the surface of molten magnesium alloy, effectively preventing further reaction between the molten magnesium alloy and oxygen and water vapor. Excessive SF6 gas levels increase costs and cause environmental pollution.

[0029] Melt temperature and holding time: If the temperature is too low and the holding time is too short, the aluminum ingot will melt slowly and cannot be fully dissolved; if the temperature is too high and the holding time is too long, not only will elements such as magnesium and zinc be burned off, affecting the yield, but over-melting will also lead to hydrogen absorption and increased oxide inclusions, resulting in a decline in the performance of the casting.

[0030] In step S3, the melt is kept at 720~730℃, and degassing is performed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 1~3L / min and a degassing time of 10~15min. After degassing, the melt is kept at a constant temperature for 8~12min, and after slag removal, die casting is performed. If the melt holding temperature is too low, the temperature will drop after degassing, resulting in a melt temperature that cannot meet the requirements for die casting; if the temperature is too high, magnesium and zinc elements will be burned off. If the argon flow rate is too low or the degassing time is too short, the number of bubbles will be small, affecting the degassing effect; if the argon flow rate is too high, it will cause melt splashing. If the degassing and holding time is too short, the slag in the melt cannot fully float to the surface; if the holding time is too long, the melt will reabsorb gas, affecting the melt quality.

[0031] Specifically, in steps S2 and S3, the volume fraction of SF6 gas in the SF6 and CO2 mixture is 0.5% to 1%; In step S4, the preheating temperature of the pressure chamber is 100~150℃, the injection speed is 0.5~1.5m / s, the injection specific pressure is 80~150MPa, and the mold temperature is maintained at 150~250℃.

[0032] When the preheating temperature of the pressure chamber is too low, the melt solidifies and forms a crust on the surface of the chamber after entering, leading to an increase in coarse pre-crystallized structures inside the melt and reducing the mechanical properties of the casting. Conversely, if the preheating temperature is too high, the melt cooling rate is too low, resulting in coarse internal structures in the casting. An appropriate injection speed ensures complete filling and surface quality of the casting; excessively high injection speed leads to gas entrapment in the melt, reducing the density of the casting; excessively low injection speed results in incomplete filling and poor surface quality. An appropriate injection specific pressure, such as 80~150MPa, provides feeding and ensures the internal quality of the casting; excessively high injection specific pressure increases the clamping force of the equipment and reduces mold life; excessively low injection specific pressure prevents the filling of shrinkage cavities inside the casting, causing defects and poor mechanical properties. Insufficient mold holding temperature affects complete filling of the casting; excessively high mold holding temperature reduces the cooling rate of the casting, resulting in coarse internal structures in the casting.

[0033] It should be noted that during the squeeze casting process, the melt solidifies under pressure and undergoes a certain degree of plastic deformation. The final formed part has fine grains, dense structure, and low porosity. The squeeze casting process is applicable to a wide range of alloys and can also be used for casting Mg-Al-Zn magnesium alloys with relatively limited fluidity. In addition, compared with the ingot deformation process, the squeeze casting process is shorter and can form complex structural parts in one step. The process is stable and suitable for mass production of complex parts at low cost.

[0034] This invention refers to GB / T 10125-2021 Artificial Atmosphere Corrosion Test - Salt Spray Test for neutral salt spray test.

[0035] The following are several specific embodiments and comparative examples of the present invention.

[0036] Example 1 This embodiment provides a high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, which, by weight percentage, contains Al: 4.50%, Zn: 0.90%, Sc: 1.80%, Mn: 0.33%, with the balance being Mg and unavoidable impurities.

[0037] The preparation method of the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, totaling 30kg. S2. Magnesium ingots, aluminum ingots, and zinc blocks are placed into an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt; the protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 0.5%; S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 715°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 720°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 1 L / min and a degaussing time of 10 minutes. S4. Transfer the melt obtained in step S3 to a container and pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 120℃, the injection speed is 1.2m / s, the injection specific pressure is 110MPa, and the mold temperature is 160℃ to obtain magnesium alloy castings. The weight of each part is 1~2kg, and a total of 14 parts are obtained.

[0038] Figure 1 This is a microstructure image of the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy casting in this embodiment. As can be seen from the image, the microstructure is uniform and dense, with the main precipitated phases being primary α-Mg and β-Mg phases. 17 Al 12 The primary α-Mg phase exhibits a fine, equiaxed dendritic morphology with a grain size of 20–40 μm, while the β-Mg phase... 17 Al 12 The phase is distributed at the primary α-Mg grain boundaries. In addition, ScZn and Al8Mn5 phases also precipitate at the grain boundaries. The dispersed ScZn phase is too small to be observed.

[0039] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 4.2 mm / y, an alloy yield strength of 172 MPa, a tensile strength of 325 MPa, and an elongation of 9.2%.

[0040] Example 2 This embodiment provides a high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, which, by weight percentage, contains Al: 5.60%, Zn: 0.96%, Sc: 1.86%, Mn: 0.42%, with the balance being Mg and unavoidable impurities.

[0041] The preparation method of the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, totaling 30kg. S2. Magnesium ingots, aluminum ingots, and zinc blocks are placed into an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt; the protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 0.5%; S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 710°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 12 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 8 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 730°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 3 L / min and a degaussing time of 15 minutes. S4. Transfer the melt obtained in step S3 to a container and pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 150℃, the injection speed is 0.8m / s, the injection specific pressure is 130MPa, and the mold is kept at 200℃ to obtain magnesium alloy castings. The weight of a single piece is 1~2kg, and a total of 14 pieces are obtained.

[0042] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 3.9 mm / y, an alloy yield strength of 175 MPa, a tensile strength of 321 MPa, and an elongation of 9.5%.

[0043] Example 3 This embodiment provides a high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, which, by weight percentage, contains Al: 5.00%, Zn: 0.90%, Sc: 1.80%, Mn: 0.30%, with the balance being Mg and unavoidable impurities.

[0044] The preparation method of the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, with a total weight of 30kg. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 720°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 725°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 2 L / min and a degaussing time of 12.5 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 125℃, the injection speed is 1.0m / s, the injection pressure is 115MPa, and the mold is kept at 200℃ to obtain magnesium alloy castings. The weight of each part is 1~2kg, and a total of 14 parts are obtained.

[0045] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 3.5 mm / y, an alloy yield strength of 170 MPa, a tensile strength of 330 MPa, and an elongation of 10.5%.

[0046] Comparative Example 1 This comparative example provides a Mg-Al-Zn magnesium alloy, which is the composition of AZ91 magnesium alloy. By weight percentage, Al: 9.70%, Zn: 0.62%, Mn: 0.22%, with the balance being Mg and unavoidable impurities.

[0047] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn master alloy according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 715°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, add Al-50Mn master alloy, and after it is completely melted into a melt, stir and keep it at the temperature for 10 minutes; S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 725°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 2 L / min and a degaussing time of 12 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 130℃, the injection speed is 1.2m / s, the injection specific pressure is 90MPa, and the mold is kept at 220℃ to obtain a magnesium alloy casting.

[0048] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 8.2 mm / y, an alloy yield strength of 145 MPa, a tensile strength of 252 MPa, and an elongation of 6.1%.

[0049] Comparative Example 2 This comparative example provides a Mg-Al-Zn magnesium alloy, which, by weight percentage, contains Al: 2.53%, Zn: 0.43%, Sc: 1.60%, Mn: 0.35%, with the balance being Mg and unavoidable impurities.

[0050] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 715°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 725°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 2 L / min and a degaussing time of 13 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 120℃, the injection speed is 1.0m / s, the injection pressure is 100MPa, and the mold is kept at 200℃ to obtain a magnesium alloy casting.

[0051] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 9.1 mm / y, an alloy yield strength of 130 MPa, a tensile strength of 240 MPa, and an elongation of 5.3%.

[0052] Comparative Example 3 This comparative example provides a Mg-Al-Zn magnesium alloy, which, by weight percentage, comprises Al: 5.33%, Zn: 0.98%, Sc: 3.21%, Mn: 0.20%, with the balance being Mg and unavoidable impurities.

[0053] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 720°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 730°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 1 L / min and a degaussing time of 10 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 120℃, the injection speed is 1.2m / s, the injection pressure is 110MPa, and the mold is kept at 200℃ to obtain a magnesium alloy casting.

[0054] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 5.9 mm / y, an alloy yield strength of 179 MPa, a tensile strength of 300 MPa, and an elongation of 5.3%.

[0055] Comparative Example 4 This comparative example provides a Mg-Al-Zn magnesium alloy, which, by weight percentage, comprises Al: 4.90%, Zn: 0.83%, Sc: 1.80%, Mn: 0.26%, with the balance being Mg and unavoidable impurities.

[0056] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 750°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 720°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 3 L / min and a degaussing time of 15 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 150℃, the injection speed is 1.2m / s, the injection specific pressure is 120MPa, and the mold is kept at 150℃ to obtain a magnesium alloy casting.

[0057] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 5.1 mm / y, an alloy yield strength of 165 MPa, a tensile strength of 315 MPa, and an elongation of 8.2%.

[0058] Comparative Example 5 This comparative example provides a Mg-Al-Zn magnesium alloy, which, by weight percentage, comprises Al: 4.32%, Zn: 0.90%, Sc: 1.68%, Mn: 0.35%, with the balance being Mg and unavoidable impurities.

[0059] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 725°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 20 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 20 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 20 minutes. The melt is kept at a constant temperature of 725°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 1.5 L / min and a degaussing time of 14 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 100℃, the injection speed is 1.1m / s, the injection specific pressure is 130MPa, and the mold is kept at 150℃ to obtain a magnesium alloy casting.

[0060] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 5.2 mm / y, an alloy yield strength of 166 MPa, a tensile strength of 318 MPa, and an elongation of 8.5%.

[0061] Comparative Example 6 This comparative example provides a Mg-Al-Zn magnesium alloy, which, by weight percentage, comprises Al: 5.68%, Zn: 0.80%, Sc: 1.75%, Mn: 0.44%, with the balance being Mg and unavoidable impurities.

[0062] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 720°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 724°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 2.5 L / min and a degaussing time of 11 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into an unheated extrusion casting chamber for die casting, with an injection speed of 1.2 m / s, an injection pressure of 110 MPa, and a mold temperature of 200°C to obtain a magnesium alloy casting.

[0063] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 5.3 mm / y, an alloy yield strength of 150 MPa, a tensile strength of 315 MPa, and an elongation of 7.1%.

[0064] Comparative Example 7 This comparative example provides a Mg-Al-Zn magnesium alloy, which, by weight percentage, comprises Al: 5.21%, Zn: 0.85%, Sc: 1.87%, Mn: 0.16%, with the balance being Mg and unavoidable impurities.

[0065] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 720°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 722°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 2 L / min and a degaussing time of 10 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 120℃, the injection speed is 3.0m / s, the injection specific pressure is 130MPa, and the mold is kept at 200℃ to obtain a magnesium alloy casting.

[0066] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 5.6 mm / y, an alloy yield strength of 160 MPa, a tensile strength of 305 MPa, and an elongation of 6.2%.

[0067] Comparative Example 8 This comparative example provides a Mg-Al-Zn magnesium alloy, which, by weight percentage, comprises Al: 4.35%, Zn: 0.86%, Sc: 1.91%, Mn: 0.17%, with the balance being Mg and unavoidable impurities.

[0068] The preparation method of the Mg-Al-Zn magnesium alloy includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc master alloys according to the weight percentage of the elements in the Mg-Al-Zn magnesium alloy. S2. Magnesium ingots, aluminum ingots, and zinc blocks are added to an induction melting furnace and heated, stirred, and held at a constant temperature under a protective atmosphere to obtain a melt. The protective atmosphere is a mixture of SF6 and CO2, with the SF6 gas volume fraction in the mixture being 1.0%. S2.1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 720°C under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at that temperature for 10 minutes after they are completely melted. S2.2 Under the protective atmosphere of SF6 and CO2 mixed gas, Al-50Mn and Mg-Sc master alloys are added and completely melted into a melt, then stirred and kept at the temperature for 10 minutes. S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature for 10 minutes. The melt is kept at a constant temperature of 725°C, and degassed using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 1 L / min and a degaussing time of 10 minutes. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting. The chamber preheating temperature is 120℃, the injection speed is 1.5m / s, the injection pressure is 50MPa, and the mold is kept at 150℃ to obtain a magnesium alloy casting.

[0069] After a 7-day neutral salt spray test, the magnesium alloy casting exhibited a weight loss corrosion rate of 5.2 mm / y, an alloy yield strength of 169 MPa, a tensile strength of 319 MPa, and an elongation of 8.5%.

[0070] Table 1 shows the magnesium alloy composition of the above embodiments and comparative examples; Table 2 shows the magnesium alloy preparation process parameters of the above embodiments and comparative examples; Table 3 shows the mechanical properties of the magnesium alloy castings of the above embodiments and comparative examples.

[0071] Table 1. Magnesium alloy composition of the examples and comparative examples

[0072] Table 2. Magnesium alloy preparation process parameters for the examples and comparative examples.

[0073] Table 3 Mechanical properties of magnesium alloy castings from the examples and comparative examples

[0074] As can be seen from Tables 1 to 3, the weight loss corrosion rates of Examples 1 to 3 using the components and preparation process of the present invention are all in the range of 3 to 5 mm / y, the yield strength is all in the range of 170 to 180 MPa, the tensile strength is all in the range of 320 to 330 MPa, and the elongation is all in the range of 9 to 11%. Comparative Example 1 uses a conventional AZ91 magnesium alloy composition, with an Al content of 9.7% higher than that of the present invention and a Zn content of 0.62% lower than that of the present invention, and no Sc is added. Comparative Example 2 has an Al content of 2.53% and a Zn content of 0.43%, both lower than that of the present invention. Comparative Example 3 has a Sc content of 3.21%, higher than that of the present invention. Except for the composition, the preparation processes of Comparative Examples 1 to 3 are all within the scope of the present invention. However, the weight loss corrosion rate of Comparative Examples 1 to 3 is higher than 5 mm / y, the yield strength except for Comparative Example 3 is lower than 150 MPa, the tensile strength is not higher than 300 MPa, and the elongation is lower than 7%. This shows that the composition of the present invention has unique advantages, and also shows that the combination of the preparation process and the composition of the present invention is necessary to achieve better technical results. The components of Comparative Examples 4-8 are all within the scope of this invention, except for some preparation process parameters which are outside the scope of this invention. Specifically, the heating temperature of Comparative Example 4 is 750℃, which is higher than that of this invention; the holding time of Comparative Example 5 is 20 min, which is higher than that of this invention; the pressure chamber of Comparative Example 6 is not preheated; the injection speed of Comparative Example 7 is 3.0 m / s, which is higher than that of this invention; the specific pressure of Comparative Example 8 is 50 MPa, which is lower than that of this invention; the weight loss corrosion rate of Comparative Examples 4-8 is higher than 5 mm / y, the yield strength is lower than 170 MPa, the tensile strength is lower than 320 MPa, and the elongation is lower than 9%. The corrosion resistance and mechanical properties are significantly worse than those of Examples 1-3. This shows that the components of this invention can only achieve better technical effects under the preparation process conditions of this invention.

[0075] In summary, the combination of the Mg-Al-Zn magnesium alloy composition and the preparation process of this invention results in a magnesium alloy with excellent comprehensive mechanical properties and corrosion resistance. Compared with wrought magnesium alloys, the process flow is shorter, complex structural parts can be formed in one step, the process is stable, and it is suitable for mass production of complex parts at low cost.

[0076] The above description of the present invention represents only some embodiments, but the present invention is not limited to the specific implementations described above. The specific implementations described above are illustrative and not restrictive. All specific extensions using the materials and methods of the present invention, without departing from the spirit and scope of the claims, are within the protection scope of the present invention.

Claims

1. A high-strength, tough, and corrosion-resistant Mg-Al-Zn magnesium alloy, characterized in that, The magnesium alloy composition, by weight percentage, is: Al: 4.00%~5.60%, Zn: 0.90%~1.00%, Sc: 1.60%~2.00%, Mn: 0.15%~0.50%, with the balance being Mg and unavoidable impurities; The magnesium alloy exhibits a 7-day neutral salt spray test with a weight loss corrosion rate of 3-5 mm / y, a yield strength of 170-180 MPa, a tensile strength of 320-330 MPa, and an elongation of 9-11%.

2. The magnesium alloy according to claim 1, characterized in that, The magnesium alloy composition, by weight percentage, is: Al: 5.00%, Zn: 0.90%, Sc: 1.80%, Mn: 0.30%, with the balance being Mg and unavoidable impurities.

3. A method for preparing a magnesium alloy as described in claim 1 or 2, characterized in that, The method includes the following steps: S1. Weigh magnesium ingots, aluminum ingots, zinc blocks, Al-Mn master alloy and Mg-Sc master alloy according to the weight percentage of the elements in the high-strength, tough and corrosion-resistant Mg-Al-Zn magnesium alloy. S2. Raw materials are fed into an induction melting furnace and heated, stirred and kept warm under a protective atmosphere to obtain a melt; S3. Under a protective atmosphere, the melt obtained in step S2 is refined, degassed, slag removed, and stirred, and then kept at a constant temperature. The degasing is carried out using a preheated rotary argon-blowing graphite rotor with an argon flow rate of 1~3L / min and a degasing time of 10~15min. S4. Transfer the melt obtained in step S3 to a container, pour it into a preheated extrusion casting chamber for die casting, and obtain a magnesium alloy casting; the preheating temperature of the chamber is 100~150℃, the injection speed is 0.5~1.5m / s, and the injection specific pressure is 110~150MPa. In steps S2 and S3, the protective atmosphere is a mixture of SF6 and CO2, wherein the volume fraction of SF6 in the mixture is 0.5-1%.

4. The method according to claim 3, characterized in that, In step S1, the Al-Mn master alloy is Al-50Mn by weight percentage; the Mg-Sc master alloy is Mg-5Sc by weight percentage.

5. The method according to claim 3, characterized in that, Step S2 includes the following sub-steps: S2.

1. Put magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heat them to 710~730℃ under a protective atmosphere of SF6 and CO2 mixed gas, and hold them at the temperature after they are completely melted. S2.2 Under a protective atmosphere of SF6 and CO2 mixed gas, add Al-Mn master alloy and Mg. The Sc intermediate alloy is completely melted into a molten body and then stirred and kept at a constant temperature.

6. The method according to claim 5, characterized in that, In both steps S2.1 and S2.2, the heat preservation time is 8 to 12 minutes.

7. The method according to claim 3, characterized in that, In step S3, the melt is kept at 720~730℃, degassed, and then kept at that temperature for 8~12 minutes.

8. The method according to claim 3, characterized in that, In step S4, the mold is kept at a temperature of 150~250℃.

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