Magnesium-aluminum alloy forming process

Abstract

The invention relates to the technical field of metal semi-solid die-casting forming processes, in particular to a magnesium-aluminum alloy forming process. A magnesium-aluminum alloy forming technology comprises the following steps that magnesium-aluminum alloy smelting is conducted, specifically, magnesium-aluminum alloy powder is transferred into a smelting furnace to be melted, inert gas injection is continuously conducted on melt in the smelting process, standing is conducted for 10-16 min after smelting is completed, and dross is skimmed; semi-solid slurry is prepared, specifically, the magnesium-aluminum alloy solution is transferred into a crucible, and then the magnesium-aluminum alloy solution is cooled and stirred; and injection molding: carrying out injection molding on the semi-solid slurry through an alloy injection molding machine, and cooling to obtain the magnesium-aluminum alloy casting. According to the magnesium-aluminum alloy forming process, the yield of prepared magnesium-aluminum alloy castings is higher, and the surface quality is better.

Description

Technical Field

[0001] This application relates to the technical field of metal semi-solid die-casting forming processes, and more specifically, it relates to a magnesium alloy forming process. Background Art

[0002] Magnesium alloys have the characteristics of low density, high strength, good toughness, and excellent shock absorption. At the same time, they have good plasticity and machinability. Therefore, products with different shapes and sizes can be obtained through various processing techniques such as casting, forging, extrusion, stretching, and semi-solid die-casting forming, and are widely used in the fields of the automotive industry, aerospace, electronic products, and medical devices.

[0003] Among them, semi-solid die-casting forming is a new metal casting process developed in the early 1970s of the 20th century. Compared with the traditional die-casting forming process, it can make the grains of the prepared alloy products finer and the tissue distribution more uniform. At the same time, the shrinkage of the matrix is reduced, the tendency of hot cracking decreases, the shrinkage porosity tendency on the matrix is eliminated, the mechanical properties are greatly improved, the solidification shrinkage is small, and the forming accuracy is high. Therefore, it gradually replaces the traditional die-casting process.

[0004] However, the semi-solid die-casting process has high requirements for raw materials. Especially when processing thin-walled magnesium alloy parts, there are defects such as low yield and poor surface quality. Therefore, there is still room for improvement in the semi-solid die-casting process for magnesium alloys. Summary of the Invention

[0005] In order to improve the defects of low yield and poor surface quality when preparing thin-walled magnesium alloy parts by the semi-solid die-casting process, this application provides a magnesium alloy forming process.

[0006] A magnesium alloy forming process provided by this application adopts the following technical solutions: A magnesium alloy forming process includes the following steps: Melting of magnesium alloy: First, transfer the magnesium alloy powder to a melting furnace for melting, and continuously blow inert gas into the molten liquid during the melting process. The inert gas is one or a mixture of two of nitrogen and argon. The melting temperature is between 510 - 620 °C. After melting until the hydrogen content of the molten liquid < 0.2 cc / 100 g, let it stand for 10 - 16 min after melting is completed, and skim off the floating slag; Among them, the Al content in the magnesium alloy is between 11% - 14%, and the magnesium alloy is doped with Ce, Ti, and Yb; Preparation of semi-solid slurry: Transfer the magnesium alloy solution to a crucible, and then perform a cooling and stirring operation on the magnesium alloy solution; among them, the cooling is carried out through cooling air, and cool and stir until the solution temperature is between 450 - 470 °C, and at the same time, the solid content in the slurry is greater than 40%; Injection molding: The semi-solid slurry is injection-molded through an alloy injection molding machine and cooled to obtain a magnesium alloy casting.

[0007] During the melting process of magnesium alloy, due to the too high temperature, it is very easy to react with oxygen in the air, resulting in oxide inclusions and gases in the melt. If no purification treatment is carried out, when preparing magnesium alloy castings, it is very easy to produce casting defects such as shrinkage cavities, shrinkage porosity, and cracks, which will lead to a low yield of magnesium alloy castings and poor surface quality.

[0008] In this regard, the applicant continuously blows inert gas into the melt during the melting process, prompting the inert gas to form bubbles in the melt. Due to the pressure difference between the inert gas and the alloy melt, the hydrogen in the melt enters the inert gas bubbles under the action of the pressure difference, and then leaves the metal melt through the floating of the bubbles. At the same time, the oxidation impurities are adsorbed and carried out of the melt by using the wettability between the bubbles and the metal oxidation impurities, so as to achieve the purpose of hydrogen and impurity removal, and further promote the obvious improvement of the yield and surface quality of magnesium alloy castings.

[0009] In addition, the fluidity of magnesium alloy is poor, so it is also very easy to produce casting defects such as shrinkage cavities, shrinkage porosity, and cracks when preparing thin-walled magnesium alloy castings. At present, in order to improve the fluidity of magnesium alloy, the content of Al is usually increased, but too high Al content will also lead to an increase in the brittleness of magnesium alloy castings, that is, the mechanical properties become worse, which will further affect the normal use of magnesium alloy castings.

[0010] Rare earth elements can improve the strength and toughness of magnesium alloy by changing the grain size and morphology. Specifically, when Ce is added to magnesium alloy, the crystal size of magnesium alloy will be significantly reduced. The reason is that Ce can inhibit the interaction between the components in magnesium alloy, thereby reducing the crystallization temperature and promoting grain growth. Moreover, Ce also has a high specific surface area and high melting point, so it can form a stable structure inside the grains, thereby inhibiting the propagation of cracks. In addition, Ce also has good magnetism, which can generate a certain magnetic field effect inside the grains, further improving the mechanical properties of magnesium alloy. Adding Ti and Yb to magnesium alloy can affect the ductility and toughness of magnesium alloy, thereby further reducing the brittleness of high-aluminum magnesium alloy.

[0011] Preferably, in the melting of magnesium alloy, the blowing method of inert gas is rotary blowing.

[0012] When continuously blowing inert gas into the melt, such as when using a rotating spray head for rotating spraying, the acting force generated by rotation will prompt strong shearing between the inert bubbles and the melt, causing the bubbles to break into uniformly distributed fine bubbles, and the bubbles to float upward in a spiral manner. This is conducive to increasing the contact time and area between the bubbles and the magnesium-aluminum alloy melt, further improving the melt purification efficiency, and further enhancing the yield and surface quality of magnesium-aluminum alloy castings.

[0013] Preferably, in the preparation of the semi-solid slurry, the cooling air flow rate is 35 - 45 L / min.

[0014] When preparing the semi-solid slurry, after selecting a relatively fast cooling air flow rate of 35 - 45 L / min, the solidification rate of the melt will also increase, thereby prompting the grain morphology of the magnesium-aluminum alloy to gradually transform into spherical grains, rather than transforming into other grains such as strip-shaped and dendritic grains. Thus, better mechanical properties can be obtained, ultimately resulting in a very high yield and extremely good product surface quality.

[0015] Preferably, in the preparation of the semi-solid slurry, stirring is carried out by a two-shaft stirrer, and the stirring directions of the two stirring rods are opposite, and the stirring blades of the two stirring rods are staggered and parallel to each other.

[0016] Preferably, in the preparation of the semi-solid slurry, the stirring speed is 600 - 800 rpm.

[0017] When using a single-shaft stirrer for stirring, the grains of the slurry structure at the edge of the crucible are spherical grains, and the grain size is smaller, the roundness is higher, and the grain distribution is uniform. However, the grains of the structure at the center of the crucible are usually other grains such as strip-shaped and dendritic grains. The reason is that during the stirring process, the shear force received at the edge position close to the crucible wall is greater, which causes more intense collision and friction between the alloy melts. At the same time, the melt also interacts with the crucible wall, resulting in more complete fragmentation of the dendrites, and thus obtaining grains with better morphology.

[0018] In this application, a two-shaft stirrer is selected for stirring, and the stirring directions of the two stirring rods are opposite, and the stirring blades of the two stirring rods are staggered and parallel to each other. Therefore, during the stirring process, a strong shear force exists in each area of the slurry, which promotes the grain morphology of the magnesium-aluminum alloy slurry to be more perfect and uniform, and further improves the yield and surface quality of the magnesium-aluminum alloy castings.

[0019] A faster stirring speed can further increase the shear force, but an excessively fast stirring speed will cause the grain size to increase, which instead affects the mechanical properties of the magnesium-aluminum alloy. Therefore, it is relatively more optimal to control the stirring speed at 600 - 800 rpm.

[0020] Preferably, the magnesium-aluminum alloy comprises raw materials in the following mass percentages: 11-14% Al, 0.5-2.0% Ce, 0.1-1.0% Ti, 0.1-1.0% Yb, 0.1-1.0% Zn, 0.2-0.4% Mn, and the balance is Mg and inevitable impurities.

[0021] Preferably, the mass ratio of Ce, Ti, and Yb is 1:(0.1-0.3):(0.2-0.4).

[0022] However, excessive rare earth elements will cause a large number of defects and cracks in the crystal of the magnesium-aluminum alloy, making the magnesium-aluminum alloy more prone to fracture. Therefore, it is necessary to reasonably proportion the addition amounts of Ce, Ti, and Yb to enable the magnesium-aluminum alloy to have better fluidity and mechanical properties. In this application, through experiments, it is found that in the magnesium-aluminum alloy, when there is 11-14% Al, 0.5-2.0% Ce, 0.1-1.0% Ti, 0.1-1.0% Yb, and the mass ratio of Ce, Ti, and Yb is 1:(0.1-0.3):(0.2-0.4), the prepared magnesium-aluminum alloy will have better fluidity and mechanical properties, ultimately showing a very high yield rate and extremely good surface quality.

[0023] Preferably, Ce, Ti, and Yb are added to the magnesium-aluminum alloy in the form of a Ce-Ti-Yb master alloy.

[0024] When Ce, Ti, and Yb are first prepared into a Ce-Ti-Yb master alloy and then added to the magnesium-aluminum alloy, Ce, Ti, and Yb will more simply and conveniently form rare earth phases, thereby making the improvement of the mechanical properties of the magnesium-aluminum alloy by Ce, Ti, and Yb more effective.

[0025] Preferably, in the injection molding, the injection speed is 0.05-0.15 m / s.

[0026] In summary, this application has the following beneficial effects: 1. Continuously blowing inert gas into the molten liquid during the melting process can cause the inert gas to form bubbles in the melt. Due to the pressure difference between the inert gas and the alloy melt, the hydrogen in the melt enters the inert gas bubbles under the action of the pressure difference, and then leaves the metal melt through the floating of the bubbles. At the same time, the wettability between the bubbles and the metal oxide impurities is used to adsorb and carry out the oxide impurities from the melt, so as to achieve the purpose of hydrogen and impurity removal, and then significantly improve the yield rate and surface quality of the magnesium-aluminum alloy casting.

[0027] 2. When using a rotating spray head for rotating spray blowing, the acting force generated by rotation will cause strong shearing between the inert bubbles and the melt, breaking the bubbles into uniformly distributed fine bubbles, and the bubbles floating upward in a spiral manner, which is conducive to increasing the contact time and area between the bubbles and the magnesium-aluminum alloy melt, further improving the melt purification efficiency, and further enhancing the yield and surface quality of magnesium-aluminum alloy castings.

[0028] 3. Rare earth elements can improve the strength and toughness of magnesium-aluminum alloys by changing the grain size and morphology. Specifically, when Ce is added to magnesium-aluminum alloys, the crystal size of magnesium-aluminum alloys will be significantly reduced. The reason is that Ce can inhibit the interaction forces between the components in magnesium-aluminum alloys, thereby reducing the crystallization temperature and promoting grain growth. Moreover, Ce also has a high specific surface area and high melting point, so it can form a stable structure inside the grains, thereby inhibiting the propagation of cracks. In addition, Ce also has good magnetism, which can generate a certain magnetic field effect inside the grains, further improving the mechanical properties of magnesium-aluminum alloys. Adding Ti and Yb to magnesium-aluminum alloys can affect the ductility and toughness of magnesium-aluminum alloys, thereby further reducing the brittleness of high-aluminum magnesium-aluminum alloys. Specific embodiments

[0029] The following further elaborates on this application in combination with Examples 1 - 10 and Comparative Examples 1 - 2.

[0030] Raw materials Al CAS: 7429 - 90 - 5; Ce CAS: 7440 - 45 - 1; Ti CAS: 7440 - 32 - 6; Yb CAS: 7440 - 64 - 4; Zn CAS: 7440 - 66 - 6; Mn CAS: 7439 - 96 - 5; Mg CAS: 7439 - 95 - 4.

[0031] Example 1 A magnesium-aluminum alloy forming process includes the following steps: Melting of magnesium-aluminum alloy: First, transfer the magnesium-aluminum alloy powder to a melting furnace for melting, and continuously blow inert gas into the melt during the melting process. The inert gas is argon, and the melting temperature is between 510 - 620 °C. After melting until the hydrogen content in the melt is < 0.2 cc / 100 g, let it stand for 15 min after melting and skim off the dross; Among them, the magnesium-aluminum alloy includes the following raw materials by mass percentage: Al 13%, Ce 1%, Ti 0.2%, Yb 0.3%, Zn 0.4%, Mn 0.3%, and the balance is Mg and unavoidable impurities; The preparation process of the magnesium-aluminum alloy is as follows: Al, Ce, Ti, Yb, Zn, Mn, and Mg are mixed according to the ratio, and then transferred to a melting furnace for melting. The melting temperature is between 510 - 620 °C. After melting, it is cooled and crushed to obtain magnesium-aluminum alloy powder; Preparation of semi-solid slurry: Transfer the magnesium-aluminum alloy solution to a crucible, and then perform cooling and stirring operations on the magnesium-aluminum alloy solution. Among them, cooling is carried out by cooling air, and the cooling air flow rate is 35 L / min. Cool and stir until the solution temperature is between 450 - 470 °C, and at the same time, the solid content in the slurry is greater than 40%; Injection molding: The semi-solid slurry is injection molded through an alloy injection molding machine and cooled to obtain a magnesium-aluminum alloy casting. Among them, the injection speed is 0.10 m / s, the model of the alloy injection molding machine is Haitian - 1300T, and the molding and cooling processes are conventional processes.

[0032] Example 2 The difference from Example 1 is that in the melting of the magnesium-aluminum alloy, the injection method of the inert gas is rotary injection, that is, a rotary nozzle is selected for injecting the inert gas.

[0033] Example 3 The difference from Example 2 is that in the preparation of the semi-solid slurry, the cooling air flow rate is 40 L / min.

[0034] Example 4 The difference from Example 2 is that in the preparation of the semi-solid slurry, the cooling air flow rate is 45 L / min.

[0035] Example 5 The difference from Example 3 is that in the preparation of the semi-solid slurry, stirring is carried out by a double-shaft stirrer, and the stirring directions of the two stirring rods are opposite. The stirring blades of the two stirring rods are staggered and parallel to each other, and the stirring speed is 600 rpm.

[0036] Example 6 The difference from Example 5 is that the stirring speed is 700 rpm.

[0037] Example 7 The difference from Example 5 is that the stirring speed is 800 rpm.

[0038] Examples 8 - 9 The difference from Example 6 is that the mass percentages of the components of the magnesium-aluminum alloy are different, as shown in Table 1 specifically.

[0039] Table 1 Mass percentage table of each component of the magnesium-aluminum alloy in Example 6 and Examples 8 - 9 Example 6 Example 8 Example 9 Al 13 14 11 Ce 1 1 1 Ti 0.2 0.1 0.3 Yb 0.3 0.4 0.2 Zn 0.4 0.1 1.0 Mn 0.3 0.4 0.2 Mg and impurities Balance Balance Balance Example 10 It is different from Example 6 in that Ce, Ti, and Yb are added to the magnesium-aluminum alloy in the form of a Ce-Ti-Yb master alloy; The preparation process of the Ce-Ti-Yb master alloy is as follows: Ce, Ti, and Yb are mixed according to the ratio, and then melted in a melting furnace. The melting temperature is between 800-900 °C. After melting, it is cooled and crushed to obtain magnesium-aluminum alloy powder.

[0040] Comparative Example 1 It is different from Example 1 in that during the melting of the magnesium-aluminum alloy, inert gas injection is no longer carried out.

[0041] Comparative Example 2 It is different from Example 1 in that Ce, Ti, and Yb are no longer added to the magnesium-aluminum alloy.

[0042] Performance detection test Taking Examples 1-10 and Comparative Examples 1-2 as raw materials, plates with a thickness of 1 mm are prepared, one thousand copies are prepared, and the qualified rate of the plates is recorded; those with shrinkage porosity, cracks, peeling and other defects on the surface of the plates are unqualified products. At the same time, the samples are tapped. If cracks and other defects also occur after tapping, they are also defined as unqualified products. The detection data are shown in Table 2.

[0043] Table 2 Detection data table of Examples 1-10 and Comparative Examples 1-2 Qualified rate Qualified rate Example 1 93.8% Example 7 98.6% Example 2 95.2% Example 8 97.9% Example 3 96.5% Example 9 98.1% Example 4 96.2% Example 10 99.8% Example 5 98.4% Comparative Example 1 81.3% Example 6 98.9% Comparative Example 2 87.9% Referring to Example 1 and Comparative Example 1 and combining with Table 2, it can be seen that compared with Example 1, the qualified rate of Comparative Example 1 has decreased significantly. This shows that during the melting of the magnesium-aluminum alloy, inert gas injection can effectively improve the qualified rate of magnesium-aluminum alloy castings.

[0044] The reason is that during the melting of the magnesium-aluminum alloy, due to the high temperature, it is very easy to react with oxygen in the air, resulting in oxide inclusions and gases in the melt. If no purification treatment is carried out, during the preparation of magnesium-aluminum alloy castings, it is very easy to produce casting defects such as shrinkage porosity and cracks, resulting in a low yield of magnesium-aluminum alloy castings and poor surface quality.

[0045] During the melting process, continuous inert gas injection into the melt promotes the formation of bubbles in the melt. Due to the pressure difference between the inert gas and the alloy melt, the hydrogen in the melt enters the inert gas bubbles under the action of the pressure difference, and then leaves the metal melt through the floating of the bubbles. At the same time, the wettability between the bubbles and the metal oxide impurities is used to adsorb and carry out the oxide impurities from the melt, so as to achieve the purpose of hydrogen and impurity removal, and then promote the obvious improvement of the yield and surface quality of magnesium-aluminum alloy castings.

[0046] Referring to Example 1 and Comparative Example 1 and combining with Table 2, it can be seen that, compared with Example 1, the qualified rate of Comparative Example 2 also decreases significantly. Thus, it shows that adding Ce, Ti and Yb to the magnesium-aluminum alloy can effectively improve the qualified rate of magnesium-aluminum alloy castings.

[0047] The reason lies in that the fluidity of the magnesium-aluminum alloy is poor, so it is very easy to generate casting defects such as shrinkage cavities, shrinkage porosity and cracks when preparing thin-walled magnesium-aluminum alloy castings. At present, in order to improve the fluidity of the magnesium-aluminum alloy, the content of Al is usually increased. However, too high Al content will also lead to an increase in the brittleness of the magnesium-aluminum alloy castings, that is, the mechanical properties become worse, thus affecting the normal use of the magnesium-aluminum alloy castings.

[0048] Rare earth elements can improve the strength and toughness of magnesium-aluminum alloys by changing the grain size and morphology. Specifically, when Ce is added to the magnesium-aluminum alloy, the crystal size of the magnesium-aluminum alloy will be significantly reduced. The reason is that Ce can inhibit the interaction between the components in the magnesium-aluminum alloy, thereby reducing the crystallization temperature and promoting grain growth. Moreover, Ce also has a high specific surface area and a high melting point, so it can form a stable structure inside the grains, thereby inhibiting the propagation of cracks. In addition, Ce also has good magnetism, which can generate a certain magnetic field effect inside the grains, further improving the mechanical properties of the magnesium-aluminum alloy. Adding Ti and Yb to the magnesium-aluminum alloy can affect the ductility and toughness of the magnesium-aluminum alloy, thereby further reducing the brittleness of the high-aluminum magnesium-aluminum alloy.

[0049] Referring to Example 1 and Example 2 and combining with Table 2, it can be seen that, compared with Example 1, the qualified rate of Example 2 is further improved. Thus, it shows that when using the rotary spray method for inert gas spraying, the qualified rate of the prepared aluminum-magnesium alloy castings will be relatively higher.

[0050] The reason lies in that when continuously spraying inert gas on the melt, such as using a rotary spray head for rotary spraying, the acting force generated by the rotation will cause the inert gas bubbles to undergo strong shearing with the melt, making the bubbles break into uniformly distributed fine bubbles, and the bubbles float in a spiral manner. Therefore, it is beneficial to increase the contact time and area between the bubbles and the magnesium-aluminum alloy melt, further improving the melt purification efficiency and promoting the further improvement of the yield and surface quality of the magnesium-aluminum alloy castings.

[0051] Referring to Examples 2 - 4 and combining with Table 2, it can be seen that as the cooling air flow rate increases, the qualified rate of the magnesium-aluminum alloy castings will gradually increase. However, when the cooling air flow rate reaches 40 L / min, if the cooling air flow rate is further increased, the qualified rate of the magnesium-aluminum alloy castings will not change significantly. Thus, it shows that when the cooling air flow rate is 40 L / min, the magnesium-aluminum alloy castings will obtain a better qualified rate.

[0052] The reason is that when preparing semi-solid slurry, selecting a relatively fast cooling air flow rate can significantly increase the solidification rate of the melt, thereby promoting the gradual transformation of the grain morphology of the magnesium-aluminum alloy into spherical grains, rather than other grains such as strip-shaped and dendritic grains, and then obtaining better mechanical properties, ultimately manifested as obtaining a very high yield rate and extremely excellent product surface quality.

[0053] Referring to Example 3 and Example 5 and combining with Table 2, it can be seen that compared with Example 3, the qualified rate of Example 5 is further improved. This shows that in the preparation of semi-solid slurry, when stirring is carried out by a twin-shaft stirrer, and the stirring directions of the two stirring rods are opposite, and the stirring blades of the two stirring rods are staggered and parallel, the magnesium-aluminum alloy castings will have a better qualified rate.

[0054] The reason is that when using a single-shaft stirrer for stirring, the grain structure of the slurry at the edge of the crucible is spherical grains, and the grain size is smaller, the roundness is higher, and the grain distribution is uniform. However, the grain structure in the center of the crucible is usually other grains such as strip-shaped and dendritic grains. This is because during the stirring process, the shear force received at the edge position close to the crucible wall is greater, which makes the alloy melt collide and rub more violently. At the same time, the melt also interacts with the crucible wall, resulting in more complete fragmentation of the dendrites, and then obtaining grains with better morphology.

[0055] When using a twin-shaft stirrer for stirring, and the stirring directions of the two stirring rods are opposite, and the stirring blades of the two stirring rods are staggered and parallel, each area of the slurry has a strong shear force, which promotes the grain morphology of the magnesium-aluminum alloy slurry to be more perfect and uniform, and further improves the yield rate and surface quality of the magnesium-aluminum alloy castings.

[0056] Referring to Example 5 - Example 7 and combining with Table 2, it can be seen that Example 6 has a relatively higher qualified rate, and the qualified rates of Example 5 and Example 7 are relatively lower. This shows that when using a twin-shaft stirrer, as the stirring speed increases, the qualified rate of the magnesium-aluminum alloy castings will gradually increase. However, when the stirring speed reaches 700 rpm, if the stirring speed is further increased, the qualified rate of the magnesium-aluminum alloy castings will instead decrease.

[0057] The reason is that a faster stirring speed can further increase the shear force, but an overly fast stirring speed will cause the grain size to become larger, which instead affects the mechanical properties of the magnesium-aluminum alloy. Therefore, it is relatively better to control the stirring speed at 700 rpm.

[0058] Referring to Example 6 and Examples 8 - 9 and in combination with Table 2, it can be seen that, compared with Example 6, the qualified rates of Examples 8 and 9 are relatively lower. Thus, it shows that when the components of the magnesium-aluminum alloy adopt the mass percentages of Example 6, the magnesium-aluminum alloy will have more excellent fluidity, toughness and mechanical properties.

[0059] The reason lies in that although the addition of rare earth elements can effectively improve the strength and toughness of the magnesium-aluminum alloy, however, excessive rare earth elements will cause a large number of defects and cracks in the crystal of the magnesium-aluminum alloy, making the magnesium-aluminum alloy more prone to fracture. Therefore, it is necessary to reasonably proportion the addition amounts of Ce, Ti and Yb to enable the magnesium-aluminum alloy to have more excellent fluidity and mechanical properties.

[0060] Through experiments, it is found that in the magnesium-aluminum alloy, when Al is 13%, Ce is 1%, Ti is 0.2%, Yb is 0.3%, Zn is 0.4%, Mn is 0.3%, and the balance is Mg and inevitable impurities, the prepared magnesium-aluminum alloy will have more excellent fluidity and mechanical properties, and finally show an extremely high yield rate and extremely excellent surface quality.

[0061] Referring to Example 6 and Example 10 and in combination with Table 2, it can be seen that, compared with Example 6, the qualified rate of Example 10 is further improved. Thus, it shows that when Ce, Ti and Yb are added to the magnesium-aluminum alloy in the form of a Ce-Ti-Yb master alloy, the prepared magnesium-aluminum alloy will have more excellent fluidity, toughness and mechanical properties.

[0062] The reason lies in that when Ce, Ti and Yb are first prepared into a Ce-Ti-Yb master alloy and then added to the magnesium-aluminum alloy, Ce, Ti and Yb will more simply and conveniently form rare earth phases, thereby making the improvement of the mechanical properties of the magnesium-aluminum alloy by Ce, Ti and Yb more effective.

[0063] This specific embodiment is only an interpretation of the present application and is not a limitation to the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A magnesium-aluminum alloy forming process, characterized in that, It includes the following steps: Melting of magnesium-aluminum alloy: First, transfer the magnesium-aluminum alloy powder into a melting furnace for melting, and continuously blow inert gas into the molten liquid during the melting process. The inert gas is one or a mixture of two of nitrogen and argon. The melting temperature is between 510 - 620 °C. Melting is carried out until the hydrogen content in the molten liquid is < 0.2 cc / 100 g. After melting is completed, let it stand for 10 - 16 min and skim off the dross; Among them, the Al content in the magnesium-aluminum alloy is between 11% - 14%, and the magnesium-aluminum alloy is doped with Ce, Ti, and Yb; Preparation of semi-solid slurry: Transfer the magnesium-aluminum alloy solution into a crucible, and then perform a cooling and stirring operation on the magnesium-aluminum alloy solution; among them, cooling is carried out through cooling air, and cooling and stirring are carried out until the solution temperature is between 450 - 470 °C, and at the same time, the solid content in the slurry is greater than 40%; Injection molding: Inject and mold the semi-solid slurry through an alloy injection molding machine, and cool to obtain a magnesium-aluminum alloy casting.

2. The magnesium-aluminum alloy forming process according to claim 1, characterized in that: In the melting of the magnesium-aluminum alloy, the blowing method of the inert gas is rotary blowing.

3. The magnesium-aluminum alloy forming process according to claim 1, characterized in that: In the preparation of the semi-solid slurry, the cooling air flow rate is 35 - 45 L / min.

4. The magnesium alloy forming process according to claim 1, characterized in that: In the preparation of the semi-solid slurry, stirring is carried out by a two-shaft stirrer, and the stirring directions of the two stirring rods are opposite, and the stirring blades of the two stirring rods are staggered and parallel to each other.

5. The magnesium-aluminum alloy forming process according to claim 4, characterized in that: In the preparation of the semi-solid slurry, the stirring speed is 600 - 800 rpm.

6. The magnesium-aluminum alloy forming process according to claim 1, characterized in that: The magnesium-aluminum alloy includes the following raw materials by mass percentage: Al 11 - 14%, Ce 0.5 - 2.0%, Ti 0.1 - 1.0%, Yb 0.1 - 1.0%, Zn 0.1 - 1.0%, Mn 0.2 - 0.4%, and the balance is Mg and inevitable impurities.

7. The magnesium-aluminum alloy forming process according to claim 6, characterized in that: The mass ratio of Ce, Ti, and Yb is 1:(0.1 - 0.3):(0.2 - 0.4).

8. The magnesium-aluminum alloy forming process according to claim 7, characterized in that: Ce, Ti, and Yb are added to the magnesium-aluminum alloy in the form of a Ce-Ti-Yb master alloy.

9. The magnesium alloy forming process according to claim 1, wherein: In the injection molding, the injection speed is 0.05 - 0.15 m / s.