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

Abstract

The invention provides a high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy and a preparation method thereof, belongs to the technical field of magnesium alloy materials, and solves the technical problem that in the prior art, the strength, the corrosion resistance and the formability of a traditional magnesium alloy cannot be considered at the same time. The invention relates to a high-toughness corrosion-resistant Mg-Al-Zn series magnesium alloy. The magnesium alloy comprises the following components in percentage by weight: 4.00%-6.00% of Al, 0.80%-1.00% of Zn, 1.60%-2.00% of Sc, 0.15%-0.50% of Mn and the balance of Mg and inevitable impurities. According to the Mg-Al-Zn series magnesium alloy, the 7-day neutral salt spray test weightlessness corrosion rate is 3-5 mm / y, the yield strength is 170-180 MPa, the tensile strength is 320-330 MPa, the elongation is 9-11%, and the Mg-Al-Zn series magnesium alloy has the high toughness and corrosion resistance and can be suitable for serving parts with the high strength requirement under the severe environment condition.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnesium alloy materials, and relates to a high-strength and high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy and a preparation method thereof. BACKGROUND

[0002] With the wide application of lightweight and high-performance materials in the fields of aerospace, automobile industry and electronic equipment, magnesium alloys have attracted more and more attention because they are currently the lightest structural metal materials with a density of only 2 / 3 of that of aluminum and 1 / 4 of that of iron.

[0003] However, although magnesium alloys have incomparable advantages in terms of lightweight, their inherent performance short boards cannot be ignored. For example, although traditional cast magnesium alloys have good formability and low cost, they have obvious deficiencies in strength. Although deformed magnesium alloys have high strength, they have defects such as high processing cost and limited forming shape. In addition, the high activity and poor corrosion resistance of magnesium alloys limit the wide application of magnesium alloy parts with complex shape or fine structure in high-strength requirements or harsh environmental conditions. For example, in the field of aerospace, aircraft need to withstand extreme flight conditions and complex climate environments, and have extremely strict requirements for the strength, toughness, corrosion resistance and formability of materials. In the automobile industry, with the rapid development of electric vehicles and autonomous driving technology, vehicles have an increasingly urgent demand for lightweight materials, but also require these materials to have good crash safety performance and corrosion resistance during long-term use.

[0004] In order to overcome the above defects, it is particularly important to develop magnesium alloy materials with high strength, high corrosion resistance and complex forming. SUMMARY

[0005] In view of the above technical status, the application provides a high-strength and high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy and a preparation method thereof, which solves the technical problem that traditional magnesium alloys in the prior art cannot be considered in terms of strength, corrosion resistance and formability. The main technical scheme is as follows: On the one hand, the application provides a high-strength and high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy, and the magnesium alloy composition comprises, by weight percentage: 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 is Mg and inevitable impurities.

[0006] Further, the magnesium alloy composition comprises, by weight percentage: Al: 5.00%, Zn: 0.90%, Sc: 1.80%, Mn: 0.30%, and the balance is Mg and inevitable impurities.

[0007] In another aspect, the application also provides a preparation method of the magnesium alloy, comprising the following steps: S1, taking magnesium ingot, aluminum ingot, zinc block, Al-Mn intermediate alloy and Mg-Sc intermediate alloy according to the weight percentage of the elements of the high-strength and high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy; S2, putting the raw materials into an induction melting furnace, heating, stirring and holding under a protective atmosphere to obtain a melt; S3, under a protective atmosphere, refining, degassing and deslagging the melt obtained in step S2, and then holding after stirring; S4, transferring the melt obtained in step S3 to a container, pouring into a preheated extrusion casting pressure chamber for pressure casting to obtain a magnesium alloy casting.

[0008] Further, in step S1, the Al-Mn intermediate alloy is Al-50Mn according to the weight percentage, and the Mg-Sc intermediate alloy is Mg-5Sc according to the weight percentage.

[0009] Further, step S2 comprises the following sub-steps: S2.1, putting the magnesium ingot, aluminum ingot and zinc block into the induction melting furnace, heating to 710-730℃ under SF6 and CO2 mixed gas protective atmosphere, holding after complete melting; S2.2, under SF6 and CO2 mixed gas protective atmosphere, adding Al-Mn intermediate alloy and Mg-Sc intermediate alloy, holding after complete melting into a melt.

[0010] Further, in steps S2.1 and S2.2, the holding time is 8-12 min.

[0011] Further, in step 3, the melt is held at 720-730℃, argon gas is used for degassing by using a preheated rotary argon gas blowing graphite rotor, and the melt is held for 8-12 min after degassing.

[0012] Further, the argon gas flow is 1-3 L / min, and the degassing time is 10-15 min.

[0013] Further, in steps 2 and 3, the protective atmosphere is SF6 and CO2 mixed gas, and the volume fraction of SF6 gas in the mixed gas is 0.5-1%.

[0014] Further, in step S4, the pressure chamber preheating temperature is 100-150℃, the injection speed is 0.5-1.5 m / s, the injection specific pressure is 80-150 MPa, and the mold holding temperature is 150-250℃.

[0015] Compared with the prior art, the application has the following beneficial effects: 1. The Mg-Al-Zn magnesium alloy of the present application has 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, and has high strength and toughness and corrosion resistance, and can be applied to service parts under harsh environmental conditions and with high strength requirements.

[0016] 2. The present application uses an extrusion casting process, which not only makes the formed parts have fine grains, dense structure and low porosity, but also has a short and stable process flow compared with the deformation treatment process, and can form complex structural parts at one time, and is suitable for mass production of complex parts at low cost. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Figure 1 is a microstructure diagram of the high-strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy of Example 1. DETAILED DESCRIPTION

[0018] The high-strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy and the preparation method thereof are further described in detail below in combination with specific examples, which are only used for the purpose of explanation, and the present application is not limited to these examples.

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

[0020] The high-strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy has 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% after a 7-day neutral salt spray test.

[0021] It should be noted that Al: forms Mg 17 Al 12 Eutectic phase, provides alloy fluidity and castability, pins dislocations, improves magnesium alloy strength, and at the same time forms an Al2O3 oxide film on the surface of the casting, increasing the corrosion resistance of the alloy; excessive addition will form excessive Mg 17 Al 12 , Mg 17 Al 12 phase as a hard quenched phase will reduce the plasticity of the alloy and reduce the elongation; therefore, the Al content is limited to 4.00%-6.00% in the present application.

[0022] Zn: Zn element solid solution in Mg alloy matrix to improve magnesium alloy strength, and Sc forms ScZn phase to improve alloy strength, while ScZn phase will form corrosion product protective film to improve alloy corrosion resistance during Mg alloy corrosion, and excessive addition will form coarse Zn-rich phase to reduce the mechanical properties of the alloy; therefore, the Zn content is limited to 0.80%~1.00% in the application.

[0023] Sc: forms Al3Sc phase which can be used as primary alpha-Mg grain heteronucleation point to refine primary magnesium grains and improve alloy strength and toughness, and the addition of Sc element can inhibit the growth of Mg 17 Al 12 phase to a certain extent, and the Al3Sc phase has a refining effect on Mg 17 Al 12 phase, in addition, Sc and Zn form ScZn phase which forms a corrosion product protective film to improve the corrosion resistance of the alloy during corrosion, and excessive addition of the Al3Sc phase in the organization is coarse and cuts the matrix to reduce the mechanical properties of the alloy; therefore, the Sc content is limited to 1.60%~2.00% in the application.

[0024] Mn: combined with Fe in the melt to form intermetallic compounds to remove impurities, improve Fe content tolerance, and improve the strength and plasticity of the alloy, at the same time, Al8Mn5 phase is formed to refine primary alpha-Mg grains and improve the strength and toughness of the alloy, and excessive addition of Mn forms Mn-rich intermetallic phase to reduce the mechanical properties of the alloy; therefore, the Mn content is limited to 0.15%~0.50% in the application.

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

[0026] On the other hand, the application also provides a preparation method of the high-strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy described above, which comprises the following steps: S1, magnesium ingot, aluminum ingot, zinc block, and Al-Mn and Mg-Sc intermediate alloy are weighed according to the weight percentage of the elements of the high-strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy; S2, the raw materials are put into an induction melting furnace, heated and stirred under a protective atmosphere to obtain a melt; S3, the melt obtained in step S2 is refined, degassed, and deslagged under a protective atmosphere, and then stirred and placed for 8~12min; S4, the melt obtained in step S3 is transferred to a container and poured into a preheated extrusion casting pressure chamber for pressure casting to obtain a magnesium alloy casting.

[0027] In step S1, the weight percentage of each metal of the Al-Mn intermediate alloy and the Mg-Sc intermediate alloy is Al-50Mn and Mg-5Sc, respectively; Al-50Mn means that the weight percentage of Mn in the Al-Mn intermediate alloy is 50%; Mg-5Sc means that the weight percentage of Sc in the Mg-Sc intermediate alloy is 5%. Because the intermediate alloy has a lower melting point and a faster dissolution speed, the composition of the prepared magnesium alloy is accurate and stable.

[0028] The specific operation steps of step S2 are as follows: S2.1, put the magnesium ingot, aluminum ingot and zinc block into an induction melting furnace, heat to 710-730℃ under the protection of SF6 and CO2 mixed gas, and keep the temperature for 8-12 min after complete melting; S2.2, under the protection of SF6 and CO2 mixed gas, add the Al-Mn intermediate alloy and the Mg-Sc intermediate alloy, completely melt into a melt, and keep the temperature for 8-12 min after stirring; A small amount of SF6, such as 0.5-1% by volume, can form an effective protective film on the surface of the magnesium alloy melt, effectively preventing further reaction of the magnesium alloy melt with oxygen and water vapor. Too high SF6 gas will increase the cost and pollute the environment.

[0029] Melt temperature and holding time: too low temperature and too short holding time will result in slow melting rate of the added aluminum ingot, which cannot be fully dissolved; too high temperature and too long holding time will not only cause burning loss of magnesium, zinc and other elements, affecting the yield, but also cause excessive melting, which will increase hydrogen absorption and oxidation inclusions, resulting in performance degradation of the casting.

[0030] In step S3, the melt is kept at 720-730℃, a preheated rotating argon gas graphite rotor is used for degassing, the argon gas flow is 1-3L / min, the degassing time is 10-15 min, the melt is kept for 8-12 min after standing after degassing, and the casting is pressed after slagging; When the melt holding temperature is too low, the melt temperature will be too low after degassing, which cannot meet the requirements of die casting; when the temperature is too high, the magnesium and zinc elements will be burned. Too low argon gas flow or too short degassing time will affect the degassing effect due to the small number of bubbles; too high argon gas flow will cause the melt to splash. Too short standing time after degassing will cause the dross in the melt to not float to the surface; too long standing time will cause the melt to absorb gas again, affecting the quality of the melt.

[0031] Specifically, in steps S2 and S3, the volume fraction of SF6 gas in the SF6 and CO2 mixed gas is 0.5-1%. 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 kept at 150-250℃.

[0032] When the preheating temperature of the compression chamber is too low, the melt causes melt solidification crust on the surface of the compression chamber after entering the compression chamber, resulting in an increase in the coarse pre-crystallization structure inside the melt, reducing the mechanical properties of the casting, and when the preheating temperature is too high, the low cooling rate of the melt causes the coarse structure inside the casting. Appropriate injection speed ensures complete filling of the casting and surface quality; too high injection speed causes melt gas entrapment, reducing the density of the casting; too low injection speed causes incomplete filling and poor surface quality. Appropriate injection pressure, such as 80-150 MPa, can provide feeding to ensure the internal quality of the casting; too high injection pressure increases the locking force of the equipment and reduces the service life of the mold; too low injection pressure cannot feed the shrinkage cavity inside the casting, causing defects and poor mechanical properties of the casting. Too low mold temperature affects complete filling of the casting; too high mold temperature reduces the cooling rate of the casting, causing coarse structure inside the casting.

[0033] It should be noted that in the process of extrusion casting, the melt solidifies under pressure and undergoes plastic deformation, resulting in fine grains, dense structure and low porosity of the final formed part. Extrusion casting process is suitable for a wide range of alloys and can also be used for casting and forming of Mg-Al-Zn magnesium alloys with relatively limited fluidity. In addition, compared with the ingot deformation processing technology, the extrusion casting preparation process is short, can form complex structural parts at one time, and is stable and suitable for mass production of complex parts at low cost.

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

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

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

[0037] The preparation method of the high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy comprises the following steps: S1, the magnesium ingot, aluminum ingot, zinc block, and Al-50Mn and Mg-5Sc intermediate alloy are weighed according to the weight percentage of the elements of the high-toughness corrosion-resistant Mg-Al-Zn magnesium alloy, and the total amount is 30 kg; S2, the magnesium ingot, aluminum ingot, zinc block are put into the induction melting furnace, heated and stirred under protective atmosphere to obtain the melt; the protective atmosphere is SF6 and CO2 mixed protective atmosphere, and the volume fraction of SF6 gas in the mixed gas is 0.5%; S2.1, put magnesium ingot, aluminum ingot and zinc block into an induction melting furnace, heat to 715℃ under SF6 and CO2 mixed gas protective atmosphere, keep for 10 minutes after complete melting; S2.2, under SF6 and CO2 mixed gas protective atmosphere, add Al-50Mn and Mg-Sc intermediate alloy, keep for 10 minutes after complete melting into melt and stirring; S3, under protective atmosphere, carry out refining degassing, deslagging and stirring to the melt obtained in step S2, and then keep for 10 minutes; keep the melt to 720℃, use preheated rotary argon blowing graphite rotor to degas, argon flow is 1L / min, and degassing time is 10 minutes; S4, transfer the melt obtained in step S3 to a container, pour into a preheated squeeze casting pressure chamber to carry out pressure casting, the preheating temperature of the pressure chamber is 120℃, the injection speed is 1.2m / s, the injection specific pressure is 110MPa, and the mold is kept at 160℃, so that magnesium alloy castings are obtained, the weight of a single piece is 1-2kg, and a total of 14 pieces are obtained.

[0038] Figure 1 It is a microstructure diagram of the high strength and toughness corrosion resistant Mg-Al-Zn magnesium alloy casting of the embodiment. As can be seen from the diagram, the microstructure is uniform and dense, wherein the main precipitated phases are primary α-Mg phase and β-Mg 17 Al 12 phase, the primary α-Mg phase presents fine equiaxed dendritic morphology, the grain size is 20-40μm, the β-Mg 17 Al 12 phase is distributed at the grain boundary of the primary α-Mg phase, in addition, ScZn phase and Al8Mn5 phase are also precipitated at the grain boundary, and the dispersed ScZn phase cannot be observed due to its small size.

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

[0040] Embodiment 2 The embodiment provides a high strength and toughness corrosion resistant Mg-Al-Zn magnesium alloy, wherein Al is 5.60%, Zn is 0.96%, Sc is 1.86%, Mn is 0.42%, and the balance is Mg and inevitable impurities.

[0041] The preparation method of the high strength and toughness corrosion resistant Mg-Al-Zn magnesium alloy comprises the following steps: S1, magnesium ingot, aluminum ingot, zinc block, Al-50Mn and Mg-5Sc intermediate alloy are weighed according to the weight percentage of the elements of the high strength and toughness corrosion resistant Mg-Al-Zn magnesium alloy, and the total amount is 30kg; S2, the magnesium ingot, aluminum ingot, zinc block is put into the induction smelting furnace, is heated under the protection atmosphere and is stirred and is kept warm to obtain the melt; the protection atmosphere is SF6 and CO2 mixed protection atmosphere, the SF6 gas volume fraction in the mixed gas is 0.5%; S2.1, the magnesium ingot, aluminum ingot, zinc block is put into the induction smelting furnace, is heated to 710 DEG C under the SF6 and CO2 mixed gas protection atmosphere, is kept warm for 12 min after complete melting; S2.2, under the SF6 and CO2 mixed gas protection atmosphere, Al-50Mn and Mg-Sc intermediate alloy are added, after complete melting into the melt, stirring and keeping warm for 8 min; S3, after the melt obtained in step S2 is refined, degassed, deslagged and stirred under the protection atmosphere, it is kept warm for 10 min;The melt is kept warm to 730 DEG C, and the preheated rotary argon blowing graphite rotor is used for degassing, and the argon flow is 3L / min, and the degassing time is 15 min; S4, the melt obtained in step S3 is transferred to a container, poured into a preheated squeeze casting pressure chamber to carry out pressure casting, the pressure chamber preheating temperature is 150 DEG C, the injection speed is 0.8 m / s, the injection specific pressure is 130 MPa, and the mold is kept warm at 200 DEG C, to obtain magnesium alloy castings, the single piece weight is 1-2 kg, and a total of 14 pieces.

[0042] The magnesium alloy castings are measured after 7-day neutral salt spray test, and the weight loss corrosion rate is 3.9 mm / y, the alloy yield strength is 175 MPa, the tensile strength is 321 MPa, and the elongation is 9.5%.

[0043] Example 3 The embodiment provides a high strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy, and the high strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy contains, by weight percentage, Al: 5.00%, Zn: 0.90%, Sc: 1.80%, Mn: 0.30%, and the balance of Mg and inevitable impurities.

[0044] The preparation method of the high strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy comprises the following steps: S1, the magnesium ingot, aluminum ingot, zinc block, and Al-50Mn and Mg-5Sc intermediate alloy are weighed according to the weight percentage of the elements of the high strength and toughness corrosion-resistant Mg-Al-Zn magnesium alloy, and the total weight is 30 kg; S2, the magnesium ingot, aluminum ingot, zinc block is put into the induction smelting furnace, is heated under the protection atmosphere and is stirred and is kept warm to obtain the melt; the protection atmosphere is SF6 and CO2 mixed protection atmosphere, the SF6 gas volume fraction in the mixed gas is 1.0%; S2.1, the magnesium ingot, aluminum ingot, zinc block is put into the induction smelting furnace, is heated to 720 DEG C under the SF6 and CO2 mixed gas protection atmosphere, is kept warm for 10 min after complete melting; S2.2, under SF6 and CO2 mixed gas protective atmosphere, Al-50Mn and Mg-Sc intermediate alloy were added, after complete melting into melt, stirring and holding for 10 min; S3, under protective atmosphere, the melt obtained in step S2 was subjected to refining, degassing, slag removal and stirring, and then was placed and held for 10 min; the melt was held at 725℃, and was degassed using a preheated rotary argon gas blowing graphite rotor, argon flow rate was 2L / min, and the degassing time was 12.5 min; S4, the melt obtained in step S3 was transferred into a container, and was poured into a preheated squeeze casting pressure chamber to perform pressure casting, the preheating temperature of the pressure chamber was 125℃, the injection speed was 1.0 m / s, the injection specific pressure was 115 MPa, and the mold holding temperature was 200℃, thereby obtaining magnesium alloy castings, the weight of a single piece was 1-2 kg, and a total of 14 pieces were obtained.

[0045] After the magnesium alloy castings were subjected to 7-day neutral salt spray test, the weight loss corrosion rate was 3.5 mm / y, the yield strength of the alloy was 170 MPa, the tensile strength was 330 MPa, and the elongation was 10.5%.

[0046] Comparative Example 1 This comparative example provided a Mg-Al-Zn magnesium alloy, which was AZ91 magnesium alloy composition, and the weight percentage of Al was 9.70%, the weight percentage of Zn was 0.62%, the weight percentage of Mn was 0.22%, and the rest was Mg and inevitable impurities.

[0047] The preparation method of the Mg-Al-Zn magnesium alloy included the following steps: S1, magnesium ingot, aluminum ingot, zinc block, and Al-50Mn intermediate alloy were weighed according to the weight percentage of the elements of the Mg-Al-Zn magnesium alloy; S2, the magnesium ingot, the aluminum ingot, and the zinc block were put into an induction melting furnace, and were heated and stirred under protective atmosphere to obtain a melt; the protective atmosphere was SF6 and CO2 mixed protective atmosphere, and the volume fraction of SF6 gas in the mixed gas was 1.0%; S2.1, the magnesium ingot, the aluminum ingot, and the zinc block were put into an induction melting furnace, and were heated to 715℃ under SF6 and CO2 mixed gas protective atmosphere, and were held for 10 min after complete melting; S2.2, under SF6 and CO2 mixed gas protective atmosphere, Al-50Mn intermediate alloy was added, and after complete melting into melt, stirring and holding for 10 min; S3, under protective atmosphere, the melt obtained in step S2 was subjected to refining, degassing, slag removal and stirring, and then was placed and held for 10 min; the melt was held at 725℃, and was degassed using a preheated rotary argon gas blowing graphite rotor, argon flow rate was 2L / min, and the degassing time was 12 min; S4, the melt obtained in step S3 is transferred to a container, poured into a preheated squeeze casting pressure chamber for die casting, the preheating temperature of the pressure chamber is 130℃, the injection speed is 1.2m / s, the injection specific pressure is 90MPa, the mold temperature is 220℃, and a magnesium alloy casting is obtained.

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

[0049] Comparative Example 2 This comparative example provides a Mg-Al-Zn magnesium alloy, in terms of weight percentage, Al: 2.53%, Zn: 0.43%, Sc: 1.60%, Mn: 0.35%, and the balance being Mg and inevitable impurities.

[0050] The preparation method of the Mg-Al-Zn magnesium alloy comprises the following steps: S1, magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc intermediate alloys are weighed according to the weight percentage of the elements of the Mg-Al-Zn magnesium alloy; S2, the magnesium ingots, aluminum ingots, and zinc blocks are put into an induction melting furnace, heated and stirred under a protective atmosphere to obtain a melt; the protective atmosphere is a mixed protective atmosphere of SF6 and CO2, and the volume fraction of SF6 gas in the mixed gas is 1.0%; S2.1, the magnesium ingots, aluminum ingots, and zinc blocks are put into an induction melting furnace, heated to 715℃ under a mixed gas protective atmosphere of SF6 and CO2, and after complete melting, the temperature is maintained for 10min; S2.2, under the mixed gas protective atmosphere of SF6 and CO2, the Al-50Mn and Mg-Sc intermediate alloys are added, and after complete melting into a melt, the temperature is maintained for 10min after stirring; S3, after refining, degassing, and stirring of the melt obtained in step S2 under a protective atmosphere, the melt is maintained for 10min; the melt is maintained at 725℃, and a preheated rotary argon gas blowing graphite rotor is used for degassing, the argon gas flow is 2L / min, and the degassing time is 13min; S4, the melt obtained in step S3 is transferred to a container, poured into a preheated squeeze casting pressure chamber for die casting, the preheating temperature of the pressure chamber is 130℃, the injection speed is 1.2m / s, the injection specific pressure is 90MPa, the mold temperature is 220℃, and a magnesium alloy casting is obtained.

[0051] The magnesium alloy casting has a weight loss corrosion rate of 8.2mm / y, an alloy yield strength of 145MPa, a tensile strength of 252MPa, and an elongation of 6.1% after 7-day neutral salt spray testing.

[0052] Comparative Example 3 The present comparative example provides a Mg-Al-Zn magnesium alloy, in terms of weight percentage, Al: 5.33%, Zn: 0.98%, Sc: 3.21%, Mn: 0.20%, and the balance being Mg and inevitable impurities.

[0053] The preparation method of the Mg-Al-Zn magnesium alloy comprises the following steps: S1, magnesium ingot, aluminum ingot, zinc block, and Al-50Mn and Mg-5Sc intermediate alloy are weighed according to the weight percentage of the elements of the Mg-Al-Zn magnesium alloy; S2, the magnesium ingot, aluminum ingot, and zinc block are put into an induction melting furnace, heated and stirred under a protective atmosphere to obtain a melt; the protective atmosphere is a mixed protective atmosphere of SF6 and CO2, and the volume fraction of SF6 gas in the mixed gas is 1.0%; S2.1, the magnesium ingot, aluminum ingot, and zinc block are put into an induction melting furnace, heated to 720℃ under a mixed gas protective atmosphere of SF6 and CO2, and after complete melting, heat preservation for 10 min; S2.2, under the mixed gas protective atmosphere of SF6 and CO2, Al-50Mn and Mg-Sc intermediate alloy is added, and after complete melting into a melt, stirring and heat preservation for 10 min; S3, after refining, degassing, and deslagging of the melt obtained in step S2 under a protective atmosphere, and after stirring and heat preservation for 10 min, the melt is heat preserved to 730℃, and a preheated rotary argon gas blowing graphite rotor is used for degassing, with an argon gas flow of 1L / min and a degassing time of 10 min; S4, the melt obtained in step S3 is transferred to a container and poured into a preheated squeeze casting pressure chamber for pressure casting, with a pressure chamber preheating temperature of 120℃, a shot speed of 1.2m / s, a shot specific pressure of 110MPa, and a mold heat preservation temperature of 200℃, to obtain a magnesium alloy casting.

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

[0055] Comparative Example 4 The present comparative example provides a Mg-Al-Zn magnesium alloy, in terms of weight percentage, Al: 5.33%, Zn: 0.98%, Sc: 3.21%, Mn: 0.20%, and the balance being Mg and inevitable impurities.

[0056] The preparation method of the Mg-Al-Zn magnesium alloy comprises the following steps: S1, taking magnesium ingot, aluminum ingot, zinc block, and Al-50Mn and Mg-5Sc intermediate alloy according to the weight percentage of elements of the Mg-Al-Zn magnesium alloy; S2, the magnesium ingot, aluminum ingot, zinc block is put into the induction melting furnace, and is heated and stirred under the protection atmosphere to obtain the melt; the protection atmosphere is SF6 and CO2 mixed protection atmosphere, and the volume fraction of SF6 gas in the mixed gas is 1.0%; S2.1, the magnesium ingot, aluminum ingot, zinc block is put into the induction melting furnace, and is heated to 750 DEG C under the SF6 and CO2 mixed gas protection atmosphere, and is kept for 10 min after complete melting; S2.2, under the SF6 and CO2 mixed gas protection atmosphere, Al-50Mn and Mg-Sc intermediate alloy is added, and after complete melting into the melt, stirring and keeping for 10 min; S3, after refining, degassing, deslagging and stirring of the melt obtained in step S2 under the protection atmosphere, standing and keeping for 10 min; the melt is kept at 720 DEG C, and the preheated rotary argon blowing graphite rotor is used for degassing, the argon flow is 3L / min, and the degassing time is 15 min; S4, the melt obtained in step S3 is transferred to a container, poured into a preheated squeeze casting pressure chamber to perform die casting, the pressure chamber preheating temperature is 150 DEG C, the injection speed is 1.2 m / s, the injection specific pressure is 120 MPa, and the mold is kept at 150 DEG C, so that the magnesium alloy casting is obtained.

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

[0058] Comparative Example 5 This comparative example provides a Mg-Al-Zn magnesium alloy, according to the weight percentage, Al: 4.32%, Zn: 0.90%, Sc: 1.68%, Mn: 0.35%, and the balance is Mg and inevitable impurities.

[0059] The preparation method of the Mg-Al-Zn magnesium alloy comprises the following steps: S1, taking magnesium ingot, aluminum ingot, zinc block, and Al-50Mn and Mg-5Sc intermediate alloy according to the weight percentage of elements of the Mg-Al-Zn magnesium alloy; S2, the magnesium ingot, aluminum ingot, zinc block is put into the induction melting furnace, and is heated and stirred under the protection atmosphere to obtain the melt; the protection atmosphere is SF6 and CO2 mixed protection atmosphere, and the volume fraction of SF6 gas in the mixed gas is 1.0%; S2.1, put the magnesium ingot, aluminum ingot and zinc block into an induction melting furnace, heat to 725℃ under SF6 and CO2 mixed gas protective atmosphere, completely melt and keep for 20 minutes; S2.2, under SF6 and CO2 mixed gas protective atmosphere, add Al-50Mn and Mg-Sc intermediate alloy, completely melt into melt, then keep for 20 minutes after stirring; S3, under protective atmosphere, the melt obtained in step S2 is subjected to refining, degassing, slag removal and stirring, then keep for 20 minutes after standing; keep the melt at 725℃, use preheated rotary argon blowing graphite rotor for degassing, argon flow is 1.5L / min, degassing time is 14 minutes; S4, transfer the melt obtained in step S3 to a container, pour into a preheated squeeze casting pressure chamber for pressure casting, the pressure chamber is preheated to 100℃, the injection speed is 1.1m / s, the injection specific pressure is 130MPa, the mold is kept at 150℃, to obtain a magnesium alloy casting.

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

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

[0062] The preparation method of the Mg-Al-Zn magnesium alloy comprises the following steps: S1, take magnesium ingot, aluminum ingot, zinc block, and Al-50Mn and Mg-5Sc intermediate alloy according to the weight percentage of elements of the Mg-Al-Zn magnesium alloy; S2, put the magnesium ingot, aluminum ingot and zinc block into an induction melting furnace, heat and stir under protective atmosphere to obtain a melt; the protective atmosphere is SF6 and CO2 mixed protective atmosphere, the volume fraction of SF6 gas in the mixed gas is 1.0%; S2.1, put the magnesium ingot, aluminum ingot and zinc block into an induction melting furnace, heat to 720℃ under SF6 and CO2 mixed gas protective atmosphere, completely melt and keep for 10 minutes; S2.2, under SF6 and CO2 mixed gas protective atmosphere, add Al-50Mn and Mg-Sc intermediate alloy, completely melt into melt, then keep for 10 minutes after stirring; S3, under a protective atmosphere, the melt obtained in step S2 is subjected to refining, degassing, slag removal and stirring, and then is left to stand for 10 min; the melt is heated to 724 DEG C, and is degassed using a preheated rotary argon gas blowing graphite rotor, argon flow rate is 2.5 L / min, and the degassing time is 11 min; S4, the melt obtained in step S3 is transferred into a container, and is poured into an unpreheated squeeze casting pressure chamber for pressure casting, the injection speed is 1.2 m / s, the injection specific pressure is 110 MPa, the mold is heated to 200 DEG C, and a magnesium alloy casting is obtained.

[0063] The magnesium alloy casting has 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% after a 7-day neutral salt spray test.

[0064] Comparative Example 7 This comparative example provides a Mg-Al-Zn magnesium alloy, according to the weight percentage, Al: 5.21%, Zn: 0.85%, Sc: 1.87%, Mn: 0.16%, and the balance is Mg and inevitable impurities.

[0065] The preparation method of the Mg-Al-Zn magnesium alloy comprises the following steps: S1, magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc intermediate alloys are weighed according to the weight percentage of the elements of the Mg-Al-Zn magnesium alloy; S2, the magnesium ingots, aluminum ingots, and zinc blocks are put into an induction melting furnace, and a melt is obtained by heating, stirring and holding under a protective atmosphere; the protective atmosphere is a mixed SF6 and CO2 protective atmosphere, and the volume fraction of SF6 gas in the mixed gas is 1.0%; S2.1, the magnesium ingots, aluminum ingots, and zinc blocks are put into an induction melting furnace, and are heated to 720 DEG C under a mixed SF6 and CO2 gas protective atmosphere, and are held for 10 min after complete melting; S2.2, under a mixed SF6 and CO2 gas protective atmosphere, the Al-50Mn and Mg-Sc intermediate alloys are added, and after complete melting into a melt, the melt is stirred and held for 10 min; S3, under a protective atmosphere, the melt obtained in step S2 is subjected to refining, degassing, slag removal and stirring, and then is left to stand for 10 min; the melt is heated to 724 DEG C, and is degassed using a preheated rotary argon gas blowing graphite rotor, argon flow rate is 2.5 L / min, and the degassing time is 11 min; S4, the melt obtained in step S3 is transferred into a container, and is poured into an unpreheated squeeze casting pressure chamber for pressure casting, the injection speed is 1.2 m / s, the injection specific pressure is 110 MPa, the mold is heated to 200 DEG C, and a magnesium alloy casting is obtained.

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

[0067] Comparative Example 8 The present comparative example provides a Mg-Al-Zn magnesium alloy, wherein the content of Al is 4.35%, the content of Zn is 0.86%, the content of Sc is 1.91%, the content of Mn is 0.17%, and the rest is Mg and inevitable impurities.

[0068] The preparation method of the Mg-Al-Zn magnesium alloy comprises the following steps: S1, taking magnesium ingots, aluminum ingots, zinc blocks, and Al-50Mn and Mg-5Sc intermediate alloys according to the weight percentage of elements of the Mg-Al-Zn magnesium alloy; S2, putting the magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heating and stirring under a protective atmosphere to obtain a melt; the protective atmosphere is a mixed protective atmosphere of SF6 and CO2, and the volume fraction of SF6 gas in the mixed gas is 1.0%; S2.1, putting the magnesium ingots, aluminum ingots, and zinc blocks into an induction melting furnace, heating to 720℃ under a mixed gas protective atmosphere of SF6 and CO2, and keeping the temperature for 10 min after complete melting; S2.2, adding Al-50Mn and Mg-Sc intermediate alloys under a mixed gas protective atmosphere of SF6 and CO2, and keeping the temperature for 10 min after complete melting into a melt; S3, after refining, degassing, and deslagging of the melt obtained in step S2 under a protective atmosphere, and keeping the temperature for 10 min after stirring; keeping the temperature of the melt at 725℃, and degassing using a preheated rotary argon gas graphite rotor, with an argon gas flow of 1 L / min and a degassing time of 10 min; S4, transferring the melt obtained in step S3 to a container, and pouring into a preheated squeeze casting pressure chamber to perform die casting, with a pressure chamber preheating temperature of 120℃, a shooting speed of 1.5 m / s, a shooting specific pressure of 50 MPa, and a mold temperature of 150℃, to obtain a magnesium alloy casting.

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

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

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

[0072] Table 2 Magnesium alloy preparation process parameters of examples and comparative examples

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

[0074] As shown in Tables 1-3, the weight loss corrosion rates of Examples 1-3 are all in the range of 3-5 mm / y, the yield strengths are all in the range of 170-180 MPa, the tensile strengths are all in the range of 320-330 MPa, and the elongations are all in the range of 9-11%. Comparative Example 1 is a conventional AZ91 magnesium alloy composition, the Al content of which is 9.7%, higher than that of the present application, the Zn content of which is 0.62%, lower than that of the present application, and no Sc is added; the Al content of Comparative Example 2 is 2.53%, and the Zn content is 0.43%, both of which are lower than those of the present application; the Sc content of Comparative Example 3 is 3.21%, higher than that of the present application; the weight loss corrosion rates of Comparative Examples 1-3 are all higher than 5 mm / y, the yield strengths of Comparative Examples 1-3 are all lower than 150 MPa except for Comparative Example 3, the tensile strengths of Comparative Examples 1-3 are all not more than 300 MPa, and the elongations of Comparative Examples 1-3 are all less than 7%; it is shown that the composition of the present application has unique advantages, and it is also shown that the preparation process of the present application and the composition of the present application are combined to achieve better technical effects. The compositions of Comparative Examples 4-8 are all within the range of the present application, and except for some preparation process parameters not within the range of the present application, the rest are within the range of the present application; specifically, the heating temperature of Comparative Example 4 is 750℃, higher than that of the present application; the holding time of Comparative Example 5 is all 20 min, higher than that of the present application; the compression chamber of Comparative Example 6 is not preheated; the injection speed of Comparative Example 7 is 3.0 m / s, higher than that of the present application; the specific pressure of Comparative Example 8 is 50 MPa, lower than that of the present application; the weight loss corrosion rates of Comparative Examples 4-8 are all higher than 5 mm / y, the yield strengths of Comparative Examples 4-8 are all lower than 170 MPa, the tensile strengths of Comparative Examples 4-8 are all lower than 320 MPa, and the elongations of Comparative Examples 4-8 are all less than 9%, the corrosion resistance and mechanical properties of Comparative Examples 4-8 are all obviously not as good as those of Examples 1-3; it is shown that the composition of the present application can only achieve better technical effects under the preparation process of the present application.

[0075] In summary, the Mg-Al-Zn magnesium alloy of the present application and the preparation process are combined to obtain a magnesium alloy with excellent comprehensive mechanical properties and corrosion resistance, and compared with the deformation magnesium alloy process, the magnesium alloy can be once formed into a complex structure part, the process is stable, and is suitable for mass production of complex parts at low cost.

[0076] The above description of the application is only some embodiments, but the application is not limited to the above specific embodiments. The above specific embodiments are illustrative, not restrictive. Any specific extension using the materials and methods of the application, without departing from the purpose of the application and the scope of the claims, all specific extensions are within the scope of the application.

Claims

1. A high-strength, high-toughness, and corrosion-resistant Mg-Al-Zn magnesium alloy, characterized in that, 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.

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. 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.

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 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.

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 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.

8. The method according to claim 7, characterized in that, The argon flow rate is 1~3L / min, and the degassing time is 10~15min.

9. The method according to claim 3, characterized in that, In steps 2 and 3, the protective atmosphere is a mixture of SF6 and CO2, wherein the volume fraction of SF6 in the mixture is 0.5-1%.

10. The method according to claim 3, characterized in that, 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℃.

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