A method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components
By introducing SF6/CO2 into the magnesium melt to generate graphene and combining it with ultrasonic treatment, problems such as hot cracking and shrinkage cavities in the magnesium alloy casting process were solved, improving the fluidity and microstructure uniformity of the magnesium alloy, and enhancing the forming quality and mechanical properties of the castings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN DONGAN ENGINE GRP
- Filing Date
- 2026-05-26
- Publication Date
- 2026-07-31
AI Technical Summary
Magnesium alloys are prone to defects such as hot cracking, shrinkage cavities, shrinkage porosity, and coarse microstructure during the casting process, which affect the forming quality and mechanical properties of the castings. Existing methods are difficult to effectively improve these defects in a coordinated manner.
SF6/CO2 mixed gas is introduced into the magnesium melt to prevent oxidation, generate graphene, and add alloying elements. Combined with ultrasonic treatment, the solidification structure and heat and mass transfer are regulated to promote the alloying process.
It significantly improves the fluidity and microstructure uniformity of magnesium alloys, reduces casting defects, and enhances the formability and mechanical properties of complex thin-walled components.
Smart Images
Figure CN122480239A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of magnesium alloy casting technology, and specifically relates to a method for improving the forming ability and mechanical properties of cast magnesium alloy complex thin-walled components. Background Technology
[0002] Magnesium alloys possess characteristics such as low density, high specific strength, high specific stiffness, good vibration damping performance, and excellent electromagnetic shielding properties, making them promising for applications in automotive lightweighting, aerospace, electronics and information technology, rail transportation, and defense equipment. Particularly in the casting field, magnesium alloys can be used to fabricate complex-shaped parts with high dimensional accuracy through gravity casting, low-pressure casting, metal mold casting, and die casting, thus becoming a key development direction for lightweight structural materials. However, a series of technical problems still hinder the widespread application of magnesium alloys in actual casting processes, particularly defects such as hot cracking, shrinkage cavities, porosity, uneven microstructure, and insufficient fluidity, which severely affect the casting quality, mechanical properties, and service reliability.
[0003] To improve the casting properties of magnesium alloys, existing technologies typically employ alloying, melt purification, modification treatment, grain refinement, and optimization of casting process parameters. For example, adding rare earth elements, carbonaceous refining agents, or other intermediate alloys improves the microstructure and refines the grains; controlling pouring temperature, mold temperature, and cooling rate regulates the solidification process; and refining, degassing, and protective atmosphere treatment improve melt purity. While these methods can improve the microstructure and properties of magnesium alloys to some extent, they still have some shortcomings. First, some refining or modifying elements are costly, limiting their industrial application. Second, some added particles are prone to agglomeration, uneven dispersion, or poor wettability with the matrix in the melt, making it difficult to exert a stable effect. Third, most existing processes focus on controlling single defects, and are insufficient for the synergistic improvement of multiple casting problems such as hot cracking, shrinkage cavities, and porosity.
[0004] In our previous research (see Chinese patent application CN111471886A), we effectively suppressed the formation of hot cracks in magnesium alloys by introducing CO2 gas into the melt to generate uniformly dispersed graphene in situ. However, further research revealed that because CO2 gas contains oxygen, it easily generates a large amount of magnesium oxide during the process, thereby reducing the cleanliness and fluidity of the melt and making it difficult to fully improve the casting quality and mechanical properties, thus failing to achieve the optimal improvement effect. Therefore, how to provide a relatively simple and easy-to-implement process that can effectively improve the solidification behavior of magnesium alloys, thereby reducing the formation of defects such as hot cracks, shrinkage cavities, and porosity, and further improving fluidity, microstructure uniformity, overall casting quality, and mechanical properties has become an urgent problem to be solved by those skilled in the art. Summary of the Invention
[0005] The purpose of this invention is to solve the problems of hot cracking, shrinkage cavities, shrinkage porosity, and coarse microstructure that are easily generated in the casting process of magnesium alloys, and to further improve fluidity, microstructure uniformity, overall forming quality of castings, and mechanical properties, by providing a method to improve the forming ability and mechanical properties of complex thin-walled components made of cast magnesium alloys.
[0006] This invention provides a simple and stable method that is suitable for improving the forming ability and mechanical properties of complex thin-walled cast magnesium alloy components.
[0007] A method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components is specifically accomplished through the following steps:
[0008] 1. Continuously blow SF6 / CO2 mixed gas into the crucible to prevent oxidation and combustion of the magnesium melt. Place pure magnesium into the crucible heated to 680℃-900℃. After the pure magnesium melts, continuously introduce hydrocarbon gas into the magnesium melt at 670℃-870℃ with continuous stirring until the graphene reaches 0.1wt.%-1wt.% of the total melt mass.
[0009] 2. After the gas is ventilated, keep the melt temperature at 100℃-300℃ and add the required alloying elements to the magnesium melt in sequence. After each alloying element is added, it should be allowed to stand before adding the next alloying element. After the last alloying element is added and allowed to stand, stir the melt at a certain speed to make the elements inside the melt evenly dispersed and fully react.
[0010] 3. After stirring, adjust the melt temperature to 700℃-850℃, and then use an ultrasonic device to ultrasonically treat the melt. After ultrasonic treatment, let it stand. After standing, remove the slag and pour the melt into a preheated mold. After pouring, let it cool and solidify naturally, let it stand, and demold to obtain a cast magnesium alloy with improved forming quality.
[0011] Compared with the prior art, the present invention has at least the following advantages:
[0012] I. This invention first introduces hydrocarbon gas into pure magnesium melt, causing an in-situ reaction to generate graphene. Subsequently, the desired alloying elements are added to formulate the target magnesium alloy. Compared with directly treating magnesium alloy melts with complex compositions, this method can achieve hydrocarbon gas decomposition and graphene generation in a relatively simple pure magnesium system, which is beneficial to improving the controllability and dispersion uniformity of the reaction process. The in-situ generated graphene can be more fully distributed in the melt during subsequent alloying, thus providing a more stable basis for solidification structure control and casting defect improvement.
[0013] Second, the graphene generated in this invention is graphene nanosheets with a large contact area. During the subsequent alloying process, it can fully react with some elements to generate related second phases, which can serve as heterogeneous nucleation cores, promote the nucleation process of primary phases or eutectic structures, improve grain refinement, and thus improve the uniformity of the casting structure. At the same time, this type of in-situ generated phase also helps to control the alloy solidification path, shorten the solidification interval to a certain extent, shorten the duration of the solid-liquid coexistence stage, and improve the feeding and stress coordination conditions of the melt at the end of solidification, thereby reducing the tendency to form defects such as hot cracks, shrinkage cavities, and shrinkage porosity.
[0014] Third, the present invention introduces ultrasonic treatment, which can significantly enhance the heat transfer, mass transfer and flow behavior inside the melt by utilizing the ultrasonic cavitation effect and acoustic flow effect. This makes it easier for hydrogen, oxide inclusions and agglomerated particles in the melt to be broken, migrated and discharged. At the same time, it promotes the homogenization of the temperature field and composition field, and reduces local segregation and local overheating. Furthermore, ultrasonic treatment can promote the activation of nucleation cores, inhibit the growth of coarse dendrites, and further refine, disperse and uniformly distribute the primary phase and the second phase, thereby reducing casting defects such as shrinkage cavities, porosity and gas pores, and improving the density and uniformity of the casting structure.
[0015] Fourth, for complex thin-walled components, the above effects help improve the stable filling ability and forming integrity of the melt in narrow and tortuous cavities, reduce the risk of defects such as under-casting and cold shut, and help achieve simultaneous improvement in strength, plasticity and comprehensive mechanical properties in terms of component service performance.
[0016] Fifth, furthermore, since the present invention can simultaneously act on the melt state, solidification behavior, and microstructure evolution process, its technical effect is not limited to the suppression of a single defect, but rather manifests as a comprehensive improvement in the casting performance of magnesium alloys. After adopting this method, the melt fluidity and filling capacity are expected to be improved, the solidification structure is more refined and uniformly distributed, and the internal density and quality stability of the casting are also improved. The method of the present invention has a clear process concept, combining the characteristics of in-situ reaction and alloying preparation, and has good feasibility and engineering application prospects. Attached Figure Description
[0017] Figure 1 The figures show the surface morphology of the castings. Figure a shows the surface morphology of the ZM5 casting prepared without the introduction of methane in Comparative Example 1, and Figure b shows the surface morphology of the ZM5-CH4 casting prepared with the introduction of methane in Example 1.
[0018] Figure 2 Figure a shows the microstructure of the castings. Figure a is the microstructure of the ZM5 casting prepared without methane in Comparative Example 1, and Figure b is the microstructure of the ZM5-CH4 casting prepared with methane in Example 1.
[0019] Figure 3 The figures show the optical microstructure of the castings. Figure a shows the optical microstructure of the ZM5 casting prepared without the introduction of methane in Comparative Example 1, and Figure b shows the optical microstructure of the ZM5-CH4 casting prepared with the introduction of methane in Example 1.
[0020] Figure 4 The figures are SEM images of the castings. In the figure, a is the SEM image of the ZM5 casting prepared without the introduction of methane in Comparative Example 1, and b is the SEM image of the ZM5-CH4 casting prepared with the introduction of methane in Example 1.
[0021] Figure 5 The figure represents the hardness of the casting. ZM5 in the figure is the hardness of the ZM5 casting prepared without the introduction of methane in Comparative Example 1, and ZM5-CH4 is the hardness of the ZM5-CH4 casting prepared with the introduction of methane in Example 1. Detailed Implementation
[0022] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the essence of the invention are within the scope of the present invention.
[0023] Specific Implementation Method 1: This implementation method is a method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components, specifically completed according to the following steps:
[0024] 1. Continuously blow SF6 / CO2 mixed gas into the crucible to prevent oxidation and combustion of the magnesium melt. Place pure magnesium into the crucible heated to 680℃-900℃. After the pure magnesium melts, continuously introduce hydrocarbon gas into the magnesium melt at 670℃-870℃ with continuous stirring until the graphene reaches 0.1wt.%-1wt.% of the total melt mass.
[0025] 2. After the gas is ventilated, keep the melt temperature at 100℃-300℃ and add the required alloying elements to the magnesium melt in sequence. After each alloying element is added, it should be allowed to stand before adding the next alloying element. After the last alloying element is added and allowed to stand, stir the melt at a certain speed to make the elements inside the melt evenly dispersed and fully react.
[0026] 3. After stirring, adjust the melt temperature to 700℃-850℃, and then use an ultrasonic device to ultrasonically treat the melt. After ultrasonic treatment, let it stand. After standing, remove the slag and pour the melt into a preheated mold. After pouring, let it cool and solidify naturally, let it stand, and demold to obtain a cast magnesium alloy with improved forming quality.
[0027] Furthermore, the graphene content can be increased to 0.1 wt.%-0.5 wt.% of the total melt mass. Changing the graphene content may affect the melt's fluidity and the number of nucleation sites generated in subsequent reactions, thereby affecting the degree of improvement in the forming quality of cast magnesium alloys.
[0028] Furthermore, after stirring, the melt temperature is adjusted to 700℃-820℃, and then the melt is ultrasonically treated using an ultrasonic device. After ultrasonic treatment, the melt is allowed to stand, and after standing, the slag is removed. Then the melt is poured into a preheated mold. Changing the pouring temperature may affect the cooling rate of the final melt, which in turn affects the filling capacity of the melt and the distribution of the second phase.
[0029] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the volume fraction of SF6 in the SF6 / CO2 mixed gas mentioned in step one is 2.4%. The other steps are the same as in Specific Implementation Method One.
[0030] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the hydrocarbon gas mentioned in step one is methane, ethane, propane, butane, ethylene, or acetylene. The other steps are the same as in Specific Implementation Method One or Two.
[0031] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: in step one, hydrocarbon gas is continuously introduced into the magnesium melt at a flow rate of 100 mL / min to 800 mL / min under conditions of 670℃-870℃ and continuous stirring; the continuous stirring speed mentioned in step one is 200 r / min to 1000 r / min. Other steps are the same as in Specific Implementation Methods One to Three.
[0032] Furthermore, in step one, hydrocarbon gas is continuously introduced into the magnesium melt at a flow rate of 100 mL / min to 400 mL / min under conditions of 700℃-800℃ and continuous stirring; the continuous stirring speed mentioned in step one is 400 r / min to 700 r / min.
[0033] By changing the gas temperature of hydrocarbons, the formation efficiency and morphology of graphene may be affected, which in turn affects the forming quality of subsequent magnesium alloys.
[0034] Changing the flow rate of hydrocarbon gas may affect the bubble size, the rate of graphene formation, and its morphology.
[0035] By changing the stirring speed during the aeration process, the reaction rate in the melt and the distribution of graphene may be affected, thereby affecting the degree of improvement in the final casting quality.
[0036] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the settling time in step two is 10-30 minutes; and the melt is stirred at a certain speed for 5-40 minutes in step two to ensure that the elements inside the melt are evenly dispersed and fully reacted. Other steps are the same as in Specific Implementation Methods One to Four.
[0037] Furthermore, the settling time mentioned in step two is 10-20 minutes; changing the settling time after ventilation may affect the content of residual gas in the melt and the distribution of graphene, thereby affecting the subsequent solidification behavior and tissue evolution.
[0038] Furthermore, in step two, the melt is stirred at a certain speed for 10-20 minutes to ensure that the elements inside the melt are evenly dispersed and fully reacted. Changing the settling time after adding alloying elements may affect the melting degree of the intermediate alloy, and thus affect the dispersion and reaction state of subsequent alloying elements.
[0039] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the alloying element mentioned in step two is one or more of Al, Zn, and Mn. The other steps are the same as in Specific Implementation Methods One to Five.
[0040] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One through Six is that after the last alloying element is added in step two and the mixture has settled, the melt is stirred at a speed of 200 r / min to 600 r / min to ensure that the elements inside the melt are evenly dispersed and react fully for 15 min to 25 min. The other steps are the same as in Specific Implementation Methods One through Six.
[0041] Changing the stirring time may affect the reaction and dispersion of graphene and alloying elements in the melt, thereby affecting the final casting quality and microstructure evolution.
[0042] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that steps one, two and three are all carried out under the protection of SF6 / CO2 mixed gas to prevent the magnesium melt from oxidizing and burning.
[0043] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the ultrasonic treatment power in step three is 10MHz-30MHz, and the time is 5min-30min; the settling time in step three is 10min-30min. Other steps are the same as in Specific Implementation Methods One to Eight.
[0044] Changing the ultrasonic treatment time may affect the breaking and dispersion of agglomerated particles inside the melt, the discharge of gas, and the uniformity of the melt temperature, thereby affecting the final casting quality.
[0045] Furthermore, the ultrasonic power described in step three is 10MHz-20MHz; changing the ultrasonic power may affect the cleanliness of the melt and the size of the particles inside the melt, thereby affecting the integrity and uniformity of the final casting.
[0046] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the preheating temperature of the mold in step three is 100℃-400℃; after pouring in step three, allow it to cool and solidify naturally, stand for 10-30 minutes, and then demold. Other steps are the same as in Specific Implementation Methods One to Nine.
[0047] Furthermore, the preheating temperature of the mold mentioned in step three is 200℃-250℃; changing the mold temperature may change the duration of the solid-liquid coexistence state, thereby affecting the filling capacity of the final melt.
[0048] The beneficial effects of the present invention are verified using the following embodiments:
[0049] Example 1: A method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components, specifically accomplished through the following steps:
[0050] 1. Continuously blow SF6 / CO2 mixed gas into the crucible to prevent oxidation and combustion of the magnesium melt. Place pure magnesium into the crucible heated to 740℃. After the pure magnesium melts, continuously introduce methane into the magnesium melt at a flow rate of 100mL / min under the condition of continuous stirring at 720℃ and 700r / min until the graphene reaches 0.5wt.% of the total mass of the melt.
[0051] 2. After the aeration is completed, let it stand for 20 minutes and maintain the melt temperature at 300℃. Then take Al, Zn and Mn elements and add them to the magnesium melt in sequence. After each alloying element is added, let it stand for 15 minutes before adding the next alloying element. After the last alloying element is added and the melt has been left to stand, stir the melt at a speed of 500 r / min to make the elements in the melt evenly dispersed and fully react for 20 minutes.
[0052] In step two, the amount of Al added is 9 wt.% of the total melt mass.
[0053] In step two, the amount of Zn added is 1 wt.% of the total melt mass.
[0054] In step two, the amount of Mn added is 0.3 wt.% of the total melt mass.
[0055] 3. After stirring, adjust the melt temperature to 750℃, and then use an ultrasonic device to ultrasonically treat the melt for 10 minutes with an ultrasonic power of 20MHz. After ultrasonic treatment, let it stand for 10 minutes. After standing, remove the slag and pour the melt into a mold at 200℃. After pouring, let it cool and solidify naturally. Let it stand for 30 minutes and then demold to obtain the cast magnesium alloy (ZM5-CH4 casting) with improved forming quality.
[0056] In Example 1, steps one, two, and three were all carried out under the protection of SF6 / CO2 mixed gas to prevent the magnesium melt from oxidizing and burning.
[0057] Comparing with Example 1: The method for preparing ZM5 castings without introducing methane is specifically carried out according to the following steps:
[0058] 1. Place pure magnesium in a crucible heated to 740°C, and continuously blow SF6 / CO2 mixed gas onto the surface of the melt to prevent the magnesium melt from oxidizing and burning. After the pure magnesium melts, magnesium melt is obtained.
[0059] 2. Keep the melt temperature to 300℃, then take Al, Zn and Mn elements and add them to the magnesium melt in sequence. After each alloying element is added, let it stand for 15 minutes before adding the next alloying element. After the last alloying element is added and the stand is finished, stir the melt at a speed of 500r / min to make the elements in the melt evenly dispersed and fully react for 20 minutes.
[0060] In step two, the amount of Al added is 9 wt.% of the total melt mass.
[0061] In step two, the amount of Zn added is 1 wt.% of the total melt mass.
[0062] In step two, the amount of Mn added is 0.3 wt.% of the total melt mass.
[0063] 3. After stirring, adjust the melt temperature to 750℃, and then use an ultrasonic device to ultrasonically treat the melt for 10 minutes with an ultrasonic power of 20MHz. After ultrasonic treatment, let it stand for 10 minutes. After standing, remove the slag and pour the melt into a mold at 200℃. After pouring, let it cool and solidify naturally, stand for 30 minutes, and then demold to obtain a magnesium alloy casting (ZM5 casting).
[0064] In contrast to Example 1, steps one, two, and three were all carried out under the protection of an SF6 / CO2 mixed gas to prevent the magnesium melt from oxidizing and burning.
[0065] Characterization of magnesium alloy castings, see Figure 1 As shown;
[0066] Figure 1 The figures show the surface morphology of the castings. Figure a shows the surface morphology of the ZM5 casting prepared without the introduction of methane in Comparative Example 1, and Figure b shows the surface morphology of the ZM5-CH4 casting prepared with the introduction of methane in Example 1.
[0067] from Figure 1 It can be observed that the ZM5 casting prepared without methane in Comparative Example 1 has obvious pores at the surface edge; while no obvious defects were observed on the surface of the ZM5-CH4 casting prepared with methane in Example 1. This indicates that the method can significantly improve the fluidity and filling ability of the melt, thereby improving the forming ability of complex thin-walled components.
[0068] In Example 1, the minimum wall thickness of the ZM5-CH4 casting prepared by introducing methane was 4 mm, and the maximum wall thickness was 10 mm.
[0069] A sample was taken from the casting for testing. See Figure 2 As shown;
[0070] Figure 2 Figure a shows the microstructure of the castings. Figure a is the microstructure of the ZM5 casting prepared without methane in Comparative Example 1, and Figure b is the microstructure of the ZM5-CH4 casting prepared with methane in Example 1.
[0071] from Figure 2 It can be observed that the ZM5 casting prepared without the introduction of methane in Comparative Example 1 has more shrinkage cavities and porosity defects; while the ZM5-CH4 casting prepared with the introduction of methane in Example 1 does not have obvious shrinkage cavities. This indicates that the method is beneficial to improving the fluidity of the melt, thereby making the filling and feeding of the melt more sufficient during the casting process, and significantly reducing the generation of defects such as micro-shrinkage cavities.
[0072] Figure 3 The figures show the optical microstructure of the castings. Figure a shows the optical microstructure of the ZM5 casting prepared without methane in Comparative Example 1, and figure b shows the optical microstructure of the ZM5-CH4 casting prepared with methane in Example 1.
[0073] from Figure 3 It can be observed that the introduction of methane gas significantly refined the alloy grains, and the microstructure distribution was more uniform compared to before the gas was introduced.
[0074] Figure 4 The figures are SEM images of the castings. In the figure, a is the SEM image of the ZM5 casting prepared without the introduction of methane in Comparative Example 1, and b is the SEM image of the ZM5-CH4 casting prepared with the introduction of methane in Example 1.
[0075] from Figure 4It can be observed that after ventilation in Example 1, the Mg-Al phase inside the alloy changed from a continuous coarse network to a discontinuous fine strip and rod shape, and the distribution became more uniform, indicating that the method has a good refining effect on the microstructure of the alloy.
[0076] Hardness testing was performed on the alloy, see [link / reference]. Figure 5 As shown;
[0077] Figure 5 The figure represents the hardness of the casting. ZM5 in the figure represents the hardness of the ZM5 casting prepared without the introduction of methane in Comparative Example 1, and ZM5-CH4 represents the hardness of the ZM5-CH4 casting prepared with the introduction of methane in Example 1.
[0078] from Figure 5 It can be observed that the hardness of the ZM5 casting prepared without the introduction of methane in Comparative Example 1 is 54.5 HV, while the hardness of the ZM5-CH4 casting prepared with the introduction of methane in Example 1 is increased to 61.7 HV, an increase of 7.2 HV. This indicates that the introduction of hydrocarbon gas can significantly improve the mechanical properties of the material.
Claims
1. A method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components, characterized in that... The method is specifically implemented according to the following steps:
1. Continuously blow SF6 / CO2 mixed gas into the crucible to prevent oxidation and combustion of the magnesium melt. Place pure magnesium into the crucible heated to 680℃-900℃. After the pure magnesium melts, continuously introduce hydrocarbon gas into the magnesium melt at 670℃-870℃ with continuous stirring until the graphene reaches 0.1wt.%-1wt.% of the total melt mass.
2. After stopping the flow of hydrocarbon gas, maintain the melt temperature at 100℃-300℃ and add the required alloying elements to the magnesium melt in sequence. After each alloying element is added, it should be allowed to stand before adding the next alloying element. After the last alloying element is added and the melt has been allowed to stand, stir the melt at a certain speed to make the elements inside the melt evenly dispersed and fully react.
3. After stirring, adjust the melt temperature to 700℃-850℃, and then use an ultrasonic device to ultrasonically treat the melt. After ultrasonic treatment, let it stand. After standing, remove the slag and pour the melt into a preheated mold. After pouring, let it cool and solidify naturally, let it stand, and demold to obtain a cast magnesium alloy with improved forming quality.
2. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... The volume fraction of SF6 in the SF6 / CO2 mixed gas mentioned in step one is 2.4%.
3. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... The hydrocarbon gas mentioned in step one is methane, ethane, propane, butane, ethylene, or acetylene.
4. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... In step one, hydrocarbon gas is continuously introduced into the magnesium melt at a flow rate of 100 mL / min to 800 mL / min under conditions of 670℃-870℃ and continuous stirring; the continuous stirring speed mentioned in step one is 200 r / min to 1000 r / min.
5. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... The settling time mentioned in step two is 10-30 minutes; the melt is stirred at a certain speed for 5-40 minutes in step two to ensure that the elements inside the melt are evenly dispersed and fully reacted.
6. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... The alloying element mentioned in step two is one or more of Al, Zn, and Mn.
7. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... After the last alloying element in step two is added and the mixture has been allowed to stand, stir the melt at a speed of 200r / min-600r / min to ensure that the elements inside the melt are evenly dispersed and react fully for 15min-25min.
8. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... Steps one, two, and three are all carried out under the protection of SF6 / CO2 mixed gas to prevent the magnesium melt from oxidizing and burning.
9. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... The ultrasonic treatment power in step three is 10MHz-30MHz, and the time is 5min-30min; the settling time in step three is 10min-30min.
10. The method for improving the formability and mechanical properties of cast magnesium alloy complex thin-walled components according to claim 1, characterized in that... The preheating temperature of the mold mentioned in step three is 100℃-400℃; after pouring in step three, allow it to cool and solidify naturally, stand for 10min~30min, and then demold.