Recycling method of regenerated aluminum alloy, recycled aluminum alloy and application of recycled aluminum alloy

Abstract

The invention discloses a recycling method of a secondary aluminum alloy, a recycled aluminum alloy and application of the recycled aluminum alloy, and the recycling method comprises the following steps: 1) taking an Al-Mg alloy melt and an oxygen-containing compound as raw materials under the conditions of vacuumizing and then introducing inert gas for protection, and reacting to prepare an Al-MgAl2O4 intermediate alloy; 2) melting a regenerated aluminum alloy to obtain a regenerated aluminum melt, adding the Al-MgAl2O4 intermediate alloy into the regenerated aluminum melt, and melting and mixing to obtain a recycled aluminum alloy melt; and (3) the recycled aluminum alloy melt is subjected to casting solidification forming, and the recycled aluminum alloy is obtained. According to the recycling method, the Fe-containing intermetallic compound phase in the regenerated aluminum alloy can be obviously improved, air holes and defects in the regenerated aluminum alloy are obviously reduced, and the mechanical property of the regenerated aluminum alloy is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of recycled aluminum alloys, and in particular to a method for recycling recycled aluminum alloys, the recycled aluminum alloys and applications thereof, and in particular to a method for recycling recycled aluminum alloys with improved Fe-containing intermetallic compound phases, the recycled aluminum alloys and applications thereof. Background Art

[0002] In the process of recycling recycled aluminum alloys, the removal of impurity elements is a key link, especially the Fe element, which will be mixed into the alloy through various channels during use, causing its content to exceed the standard. The Fe element often forms coarse needle-shaped Fe-containing intermetallic compounds with other elements, which seriously reduce the mechanical properties of the material and increase casting defects. A lot of research has been done at home and abroad on the removal of excessive Fe impurity elements in recycled Al-Si alloys, mainly focusing on the addition of alloying elements such as Mn and Cr to convert Fe impurity elements in the melt into high-density Fe-containing compounds, and by separating the high-density Fe-containing compounds, reducing the Fe content in the melt. However, this method has low Fe removal efficiency, and a large amount of Fe content will still remain in the alloy, and a large amount of Mn, Cr and other elements will also be introduced. Therefore, it is of great significance to treat the remaining Fe elements in the alloy and convert them into Fe-containing phases that have less impact on the performance of recycled aluminum alloys.

[0003] Grain refiners are usually added to the alloy to refine the grain structure and Fe-containing phase of the alloy. Al-Ti-B master alloy is the most commonly used grain refiner, but less than 1% of the added TiB2 particles are active for nucleation, and the efficiency is very low.

[0004] Patent CN202010651481 discloses a method for refining the iron-rich phase in an Al-Si die-cast aluminum alloy. The method is to add a high content of Sr element to a high-Fe-content cast aluminum alloy to modify the Fe-rich phase, reduce the size of the Fe-rich phase and change its morphology, thereby improving its mechanical properties. However, when the amount of Sr element added is high, the air absorption tendency of the aluminum melt also increases, and additional Sr elements are introduced.

[0005] Patent CN103820683A discloses a multi-component composite refinement and modification treatment method for Fe phase in high-Fe aluminum-silicon alloy. This method is to add Al-Ti-C, Al-Mn and Al-Re intermediate alloys to the alloy to inhibit the formation of β-Fe phase in the alloy and instead generate α-Fe phase which has less effect on the mechanical properties of the alloy. However, this method introduces new elements such as Mn, Ti, C, Re, etc., and the degassing process uses C2Cl6, which will produce a large amount of highly toxic gas, limiting its application.

[0006] And although grain refiners or modifiers are usually added to aluminum alloys to refine the Fe phase, this method is rarely used in secondary aluminum alloys.

[0007] In the actual production process, there is always a tendency to form an oxide film on the surface of the liquid aluminum melt. The oxide inevitably enters the liquid aluminum alloy. Its crystal structure is similar to that of the aluminum matrix, and it can also serve as a nucleation site for iron-containing intermetallic compounds in the aluminum alloy. However, there are several difficulties in this technology. One is that it is difficult to add oxygen. There are studies that use oxygen elements introduced by oxidation on the surface of aluminum liquid, but the oxygen content of this method is not easy to control; if O2 is directly passed through the aluminum liquid, this method is more dangerous; there is also a form of adding solid oxides to the aluminum alloy, but due to the presence of an oxide film on the surface of the melt, the wettability of the solid oxide and the melt is significantly reduced, and it is easy to entrain air when a physical external field is applied in the air, resulting in a large number of pores and oxide film defects. Adding it to the target melt will reduce the purity of the subsequent melt.

[0008] How to improve the Fe-containing intermetallic compound phase in the recycled aluminum alloy and reduce the pores and defects in the recycled aluminum alloy so that its mechanical properties can be significantly improved is a technical difficulty in the field of recycled aluminum alloy. Summary of the invention

[0009] The purpose of the present invention is to overcome one or more deficiencies in the prior art and to provide an improved method for recycling recycled aluminum alloys, which can significantly improve the Fe-containing intermetallic compound phase in the recycled aluminum alloy and significantly reduce the pores and defects therein, thereby significantly improving the mechanical properties of the recycled aluminum alloy.

[0010] The present invention also provides a recycled aluminum alloy prepared by the above preparation method.

[0011] The present invention also provides a use of the recycled aluminum alloy.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A method for recycling recycled aluminum alloy, the recycling method comprising the following steps:

[0014] 1) Under the condition of first evacuating the vacuum and then introducing the protection of inert gas, Al-Mg alloy melt and oxygen-containing compound are used as raw materials to react and prepare Al-MgAl2O4 master alloy;

[0015] 2) melting the recycled aluminum alloy to obtain a recycled aluminum melt, adding the Al-MgAl2O4 master alloy to the recycled aluminum melt, melting and mixing, and obtaining a recycled aluminum alloy melt;

[0016] 3) Casting and solidifying the recycled aluminum alloy melt to obtain a recycled aluminum alloy.

[0017] In the prior art, the removal of excessive Fe impurity elements in recycled alloys such as recycled Al-Si is mainly achieved by adding alloying elements such as Mn and Cr to convert Fe impurity elements in the melt into high-density Fe-containing compounds, and by separating the high-density Fe-containing compounds, the Fe content in the melt is reduced. However, this method has low Fe removal efficiency, and a large amount of Fe content will still remain in the alloy, and a large amount of Mn, Cr and other elements will also be introduced. Without introducing other impurity elements, how to optimize and refine the Fe phase in the recycled aluminum alloy is a difficult problem. The inventor of the present application has found through research that, by preparing Al-MgAl2O4 master alloy by reaction under the condition of first evacuating the vacuum and then introducing the inert gas protection, and then adding the Al-MgAl2O4 master alloy to the recycled aluminum alloy for melting and casting, the Fe-containing intermetallic compound phase in the recycled aluminum alloy can be significantly improved, and the shape of the iron-containing phase in the recycled aluminum alloy is changed from unevenly distributed long strips and large blocks to fine particles, worms, etc., thereby achieving the refinement and improvement of the Fe-containing intermetallic compound phase, and obtaining a recycled aluminum alloy with a refined and uniformly distributed Fe phase and significantly improved mechanical properties. Compared with the ordinary atmospheric pressure environment, the condition of first evacuating the vacuum and then introducing the inert gas protection can significantly suppress the entrainment of air due to the almost absence of oxygen, so that the pores and oxide film defects of the Al-MgAl2O4 master alloy and the final recycled aluminum alloy are significantly reduced, and the mechanical properties of the final recycled aluminum alloy are further improved. Oxygen-containing compounds provide O raw materials for the master alloy. Compared with the existing method of introducing oxygen by surface oxidation of molten aluminum, the amount of oxygen-containing compounds is easier to control, that is, it is more convenient to control the oxygen content. It is safer than directly introducing oxygen. Compared with directly adding solid oxides to aluminum alloys, oxygen-containing Al-MgAl2O4 master alloys can be melted together with recycled aluminum alloys and can be mixed more evenly.

[0018] In some embodiments, the vacuum is evacuated to a pressure of 10 -5 ~100Pa; preferably 10 -3 ~10Pa, more preferably 10 -3 ~1Pa. This pressure is the actual pressure of the pressure gauge reading, which is the absolute pressure. Under this vacuum pressure, the oxygen in the air is almost completely removed and will not cause air entrainment.

[0019] In some embodiments, step 1) is performed in a vacuum furnace.

[0020] In some embodiments, the reaction temperature of step 1) is 700-850°C.

[0021] In some embodiments, the reaction time of step 1) is 10 to 120 minutes.

[0022] In some embodiments, the reaction in step 1) is carried out under stirring; preferably, the stirring is intermittent stirring.

[0023] In some embodiments, the stirring is mechanical stirring.

[0024] In some embodiments, the intermittent stirring is stirring for 2-8 minutes every 15-25 minutes.

[0025] In some embodiments, the oxygen-containing compound is selected from a combination of one or more of SiO2, H3BO3 and TiO2.

[0026] In some embodiments, the oxygen-containing compound is in the form of a solid powder.

[0027] In some embodiments, the mass of the oxygen-containing compound is 0.1% to 10.0% of the mass of the Al-Mg alloy melt; preferably 2% to 8%. If the amount of the oxygen-containing compound is too much, it is not easy to disperse evenly in the Al-Mg alloy melt, which is not conducive to the formation of evenly dispersed MgAl2O4 phases and the improvement of the iron-containing phase in the subsequent recycled aluminum alloy; if the amount of the oxygen-containing compound is too little, the amount of MgAl2O4 phase generated is very small, which is also not conducive to the improvement of the iron-containing phase in the subsequent recycled aluminum alloy.

[0028] In some embodiments, in the Al-Mg alloy melt, by weight percentage: Mg 1.0% to 10.0%, and the balance Al.

[0029] In some embodiments, the step 1) specifically includes: heating and melting pure Al ingots and pure Mg ingots under vacuum and then inert gas protection to obtain an Al-Mg alloy melt; adding the oxygen-containing compound to the Al-Mg alloy melt and dispersing it evenly to obtain an intermediate alloy melt; and heat-insulating the intermediate alloy melt while stirring, and obtaining an Al-MgAl2O4 intermediate alloy after cooling and solidification.

[0030] In some embodiments, the step 1) specifically includes: heating pure Al ingots and pure Mg ingots to 700-850°C under vacuum and then inert gas protection to melt to obtain an Al-Mg alloy melt; adding the preheated oxygen-containing compound to the Al-Mg alloy melt and dispersing it evenly to obtain an intermediate alloy melt; keeping the intermediate alloy melt at 700-850°C for reaction for 10-120 minutes, stirring it for 2-8 minutes every 15-25 minutes, and obtaining an Al-MgAl2O4 intermediate alloy after cooling and solidification.

[0031] In some embodiments, the uniform dispersion is achieved by mechanical stirring, electromagnetic stirring or ultrasonic vibration.

[0032] In some embodiments, the stirring is achieved by mechanical stirring or electromagnetic stirring.

[0033] In some embodiments, the oxygen-containing compound is added to the Al-Mg alloy melt through a titanium tube or a copper tube.

[0034] In some embodiments, the recycled aluminum alloy is selected from a combination of one or more of Al-Si recycled aluminum alloys, Al-Si-Mg recycled aluminum alloys, Al-Si-Cu recycled aluminum alloys, and Al-Si-Cu-Mg recycled aluminum alloys.

[0035] In some embodiments, the recycled aluminum alloy further includes other metals selected from a combination of one or more of Fe, Mn, Cr, V, Mo, Ti, Zn, and Cu.

[0036] Preferably, when the recycled aluminum alloy includes a combination of one or more of Fe, Mn, Cr, V, Mo, Ti and Zn, in terms of weight percentage, the Fe is 0.1% to 1.5%, the Mn is 0.01% to 3%, the Cr is 0.01% to 1.0%, the V is 0.01% to 0.5%, the Mo is 0.01% to 0.3%, the Ti is 0.01% to 0.5%, and the Zn is 0.01% to 3.0%.

[0037] Preferably, the recycled aluminum alloy further comprises other optional impurities, and the sum of the other impurities is no more than 0.3% by weight.

[0038] In some embodiments, the mass percentage of Cu in the Al-Si-Cu series recycled aluminum alloy is 0.01% to 4.0%.

[0039] In some embodiments, the mass percentage of Cu in the Al-Si-Cu-Mg series recycled aluminum alloy is 0.01% to 4.0%, and the mass percentage of Mg is 0.01% to 4.0%.

[0040] In some embodiments, the mass of the Al-MgAl2O4 master alloy is 5%-30% of the mass of the recycled aluminum alloy.

[0041] In some embodiments, step 2) is performed in air.

[0042] In some embodiments, the casting solidification molding in step 3) is selected from one or more combinations of gravity, high pressure, extrusion, low pressure, and differential pressure casting.

[0043] In some embodiments, during the casting solidification molding in step 3), the solidification rate is above 0.5°C / s; preferably 0.5-80°C / s.

[0044] The present invention also provides the recycled aluminum alloy obtained by the aforementioned recycling method of the recycled aluminum alloy.

[0045] In some embodiments, the iron-containing phase in the recycled aluminum alloy is in the form of fine particles and / or worms, with an aspect ratio of less than 2.5 and a length of less than 20 μm. It can be seen that the iron-containing phase in the recycled aluminum alloy is significantly improved by the recycling method of the present invention.

[0046] The present invention also provides the use of the aforementioned recycled aluminum alloy in the preparation of automobile chassis structural parts, engines or transmission components.

[0047] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0048] The present invention pre-prepare Al-MgAl2O4 master alloy under the condition of first evacuating the vacuum and then introducing inert gas protection (for example, in a vacuum furnace). During the preparation, the added solid oxide powder can be fully reacted and air entrainment can be prevented. The generated MgAl2O4 phase is in the form of fine particles. The MgAl2O4 phase is added to the recycled aluminum alloy and can be used as a nucleation substrate for Fe-containing intermetallic compounds to refine the Fe-containing phase therein, so that the coarse and continuous Fe-containing phase in the recycled aluminum alloy is discontinuously distributed and uniform in size, and finally evenly distributed in the recycled aluminum alloy. The mechanical properties of the alloy after recycling are good, and the tolerance of the Fe content in the recycled aluminum alloy is improved.

[0049] The present invention first prepares Al-MgAl2O4 master alloy by reaction under the condition of first evacuating a vacuum and then introducing an inert gas for protection, and then adds the master alloy into a recycled aluminum alloy for melting and casting, which can significantly improve the Fe-containing intermetallic compound phase in the recycled aluminum alloy, and transform the shape of the iron-containing phase in the recycled aluminum alloy from unevenly distributed long strips and large blocks to fine particles, worms, etc., thereby achieving the refinement and improvement of the Fe-containing intermetallic compound phase, and obtaining a recycled aluminum alloy with a refined and evenly distributed Fe-containing phase and significantly improved mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a scanning electron micrograph of the master alloy prepared in air in Comparative Example 1.

[0051] Figure 2 This is a scanning electron micrograph of the master alloy prepared under vacuum conditions in Example 1.

[0052] Figure 3 This is the metallographic structure of the recycled aluminum alloy in Comparative Example 2 without adding the intermediate alloy.

[0053] Figure 4 The metallographic structure of the regenerated aluminum of the master alloy prepared in air is added to Comparative Example 1.

[0054] Figure 5 The metallographic structure of the regenerated aluminum of the intermediate alloy prepared in vacuum is added to Example 1. DETAILED DESCRIPTION

[0055] Elements such as Mn, Cr, V, and Mo in aluminum alloy melts have a metamorphic effect, but due to their extremely complex crystal structure and composition, the structural and composition conditions required for their nucleation are very harsh. At the same time, these elements are heavy metal elements. When the content is high, they are easy to combine with Fe elements to form coarse phases and settle to the bottom of the melt, resulting in a limited number of effective nuclei for ferrous metal compounds in the melt. The refinement of ferrous intermetallic compounds restricts the high-value utilization of recycled aluminum alloys.

[0056] The present invention first prepares a highly uniform and pure MgAl2O4 nucleating agent in a reduced pressure vacuum environment. Under vacuum conditions, it can not only effectively prevent the generation of an oxide film, but also greatly improve the dispersibility of oxygen-containing compound particles and their wettability with the melt. Stirring (physical external field) can make the oxygen-containing compound powder dispersed evenly and react completely to generate a large number of dispersed MgAl2O4 particles. The particles can achieve the regulation of the crystal structure and micromorphology of Fe-containing intermetallic compounds in recycled aluminum alloys.

[0057] Step 2) The MgAl2O4 and θ-Al in the melt 13 The crystallographic orientation relationship of Fe4 is MgAl2O4 / / Al 13 Fe4,[1 1 0]MgAl2O4 / / 3.4°[0 2 1]θ-Al 13 Fe4, the two phases are in a coherent and semi-coherent relationship. MgAl2O4 phase precipitates first due to its high melting point, while θ-Al 13 The Fe4 phase will precipitate in large quantities with the MgAl2O4 particles precipitated first as the nucleation base, reducing the θ-Al 13 The barrier for the transformation of Fe4 phase to eutectic α-Fe phase. Adding MgAl2O4 nucleating agent to the melt provides high-density nucleation particles as the nucleation substrate of Fe-containing intermetallic compounds. Fe-containing intermetallic compounds can be significantly refined, and finally the shape, size and uniformity of iron-containing intermetallic compounds can be regulated, so that a large number of Fe-containing phases are nucleated and metamorphosed to form Chinese character-shaped and fishbone-shaped structures, which increases the tolerance of recycled aluminum alloy to Fe content and improves the mechanical properties of the alloy.

[0058] The above scheme is further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0059] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0060] Embodiment 1:

[0061] This example provides a recycled aluminum alloy, and the preparation method thereof is as follows:

[0062] 1) Pure Al ingot and pure Mg ingot (mass ratio of the two is 24 / 1) are first evacuated to a pressure of 10 -2 Pa, then heated to 750℃ in a vacuum furnace protected by argon to melt, then added 5% SiO2 powder of the total mass of pure Al ingot and pure Mg ingot, and mechanically stirred to make the powder dispersed evenly and react completely, kept warm for 1h and mechanically stirred for 5min every 20min, then poured into a mold to cool and solidify, to obtain Al-MgAl2O4 master alloy;

[0063] 2) heating and melting the recycled aluminum alloy in air, cutting out an Al-MgAl2O4 master alloy ingot accounting for 10% of the mass fraction of the recycled aluminum alloy melt, adding the ingot to the recycled aluminum alloy melt, heating and stirring to completely melt the master alloy;

[0064] The recycled aluminum alloy is an Al-Si-Mg alloy, and its composition, by mass percentage, is: Si 7.0%, Fe 1.0%, Mn 1.0%, Mg 0.5%, Ti 0.01%, Zn 0.01%, Cu 0.01%, impurity elements do not exceed 0.3%, and the balance is Al.

[0065] 3) After the alloy is completely melted, the crucible is taken out and allowed to stand. After cooling to 700°C, it is cast into a metal mold preheated to 200°C and cooled and solidified to obtain a recycled aluminum alloy.

[0066] Embodiment 2:

[0067] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that the SiO2 powder in step 1) is replaced by TiO2 powder.

[0068] Embodiment 3:

[0069] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that the SiO2 powder in step 1) is replaced by H3BO3 powder.

[0070] Embodiment 4:

[0071] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that the pressure after vacuuming in step 1) is adjusted to 0.1 Pa.

[0072] Embodiment 5:

[0073] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that the pressure after vacuuming in step 1) is adjusted to 10 Pa.

[0074] Embodiment 6:

[0075] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that the amount of SiO2 powder in step 1) is adjusted to 10%.

[0076] Embodiment 7:

[0077] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that the amount of SiO2 powder in step 1) is adjusted to 0.5%.

[0078] Embodiment 8:

[0079] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that the recycled aluminum alloy in step 2) is adjusted to an Al-Si-Cu-Mg alloy, and its composition, by mass percentage, is: Si 9.0%, Fe 1.0%, Mn 0.6%, Cu 1.5%, Mg 0.5%, Ti 0.08%, Zn 2.0%, impurity elements do not exceed 0.3%, and the balance is Al.

[0080] Comparative Example 1:

[0081] This example provides a recycled aluminum alloy, and its preparation method is basically the same as that of Example 1, except that: the step 1) is first evacuated to a pressure of 10 -2 Pa, and then the vacuum furnace protected by argon gas is replaced by a melting furnace under normal air conditions.

[0082] Comparative Example 2:

[0083] This example provides a recycled aluminum alloy similar to that in Example 1. The recycled aluminum alloy is an Al-Si-Mg alloy, and its composition is, by mass percentage, Si 7.0%, Fe 1.0%, Mn 1.0%, Mg 0.5%, Ti 0.01%, Zn 0.01%, Cu 0.01%, impurity elements not exceeding 0.3%, and the balance is Al. No intermediate alloy is added, and no recycling treatment is performed.

[0084] Performance Testing:

[0085] The test method for tensile strength and yield strength at room temperature: GB / T 228-2021; the test method for elongation at room temperature: GB / T 228-2021; the results are shown in Table 1 below.

[0086] Table 1

[0087] Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 161 113 3.76 Example 2 143 112 2.87 Example 3 149 111 2.54 Example 4 143 112 2.48 Example 5 139 109 2.30 Example 6 145 110 2.60 Example 7 145 112 2.52 Example 8 174 121 3.04 Comparative Example 1 130 102 2.24 Comparative Example 2 122 100 1.57

[0088] Figure 1 is a scanning electron micrograph of the master alloy prepared under non-vacuum conditions in Comparative Example 1, Figure 2 This is a scanning electron micrograph of the master alloy prepared under vacuum conditions in Example 1. The dark gray particles are added SiO2 particles. Figure 1 Due to the presence of oxide film, SiO2 particles agglomerate seriously and there are many holes. Figure 2 The SiO2 particles are dispersed evenly and almost no pores are visible. Figure 3 The microstructure of the recycled aluminum alloy without adding the master alloy in Comparative Example 2 is shown. The alloy contains a large amount of needle-like Fe-containing phase. Figure 4 The figure shows the microstructure of the recycled aluminum alloy prepared by adding the master alloy in air in Comparative Example 1. The needle-like Fe-containing phase in the alloy is reduced, but there are serious pores. Figure 5 The microstructure of the recycled aluminum alloy in Example 1 in which the master alloy prepared in vacuum is added is shown. The needle-like Fe-containing phase in the alloy is almost completely transformed into Chinese character-shaped and fishbone-shaped Fe-containing phases, and no defects such as pores are found. From Table 1, it can be seen that after adding the master alloy prepared in air to the recycled aluminum alloy in Comparative Example 1, the mechanical properties of the alloy are significantly lower than those of Example 1 in which the master alloy prepared in vacuum is added.

[0089] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0090] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A method for recycling recycled aluminum alloy, characterized in that: The recovery method comprises the following steps: 1) Under the condition of first evacuating the vacuum and then introducing the protection of inert gas, Al-Mg alloy melt and oxygen-containing compound are used as raw materials to react and prepare Al-MgAl2O4 master alloy; 2) melting the recycled aluminum alloy to obtain a recycled aluminum melt, adding the Al-MgAl2O4 master alloy to the recycled aluminum melt, melting and mixing, and obtaining a recycled aluminum alloy melt; 3) Casting and solidifying the recycled aluminum alloy melt to obtain a recycled aluminum alloy.

2. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The vacuum is pumped to a pressure of 10 -5 ~100Pa; preferably 10 -3 ~10Pa.

3. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The step 1) is carried out in a vacuum furnace; and / or the reaction temperature of the step 1) is 700-850° C.; and / or the reaction time of the step 1) is 10-120 min.

4. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The reaction in step 1) is carried out under stirring; preferably, the stirring is intermittent stirring.

5. The method for recycling recycled aluminum alloy according to claim 4, characterized in that: The intermittent stirring is stirring for 2-8 minutes every 15-25 minutes.

6. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The oxygen-containing compound is selected from a combination of one or more of SiO2, H3BO3 and TiO2; and / or, the oxygen-containing compound is in the form of solid powder.

7. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The mass of the oxygen-containing compound is 0.1% to 10.0% of the mass of the Al-Mg alloy melt.

8. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: In terms of weight percentage, the Al-Mg alloy melt contains 1.0% to 10.0% Mg and the remainder Al.

9. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The step 1) specifically includes: heating pure Al ingots and pure Mg ingots to 700-850° C. under the condition of first evacuating the vacuum and then introducing inert gas protection to melt them, so as to obtain an Al-Mg alloy melt; adding the preheated oxygen-containing compound to the Al-Mg alloy melt and dispersing it evenly to obtain an intermediate alloy melt; keeping the intermediate alloy melt at 700-850° C. for reaction for 10-120 minutes, stirring it for 2-8 minutes every 15-25 minutes, and obtaining an Al-MgAl2O4 intermediate alloy after cooling and solidification.

10. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The recycled aluminum alloy is selected from a combination of one or more of Al-Si recycled aluminum alloy, Al-Si-Mg recycled aluminum alloy, Al-Si-Cu recycled aluminum alloy and Al-Si-Cu-Mg recycled aluminum alloy.

11. The method for recycling recycled aluminum alloy according to claim 10, characterized in that: The recycled aluminum alloy further comprises other metals selected from the group consisting of one or more of Fe, Mn, Cr, V, Mo, Ti and Zn; preferably, when the recycled aluminum alloy comprises one or more of Fe, Mn, Cr, V, Mo, Ti and Zn, in terms of weight percentage, the Fe is 0.1% to 1.5%, the Mn is 0.01% to 3%, the Cr is 0.01% to 1.0%, the V is 0.01% to 0.5%, the Mo is 0.01% to 0.3%, and the Ti is 0.01% to 0.5%, and Zn is 0.01% to 3.0%; the recycled aluminum alloy also includes other optional impurities, and the sum of the other impurities is not more than 0.3% by weight; and / or, the mass percentage of Cu in the Al-Si-Cu series recycled aluminum alloy is 0.01% to 4.0%; and / or, the mass percentage of Cu in the Al-Si-Cu-Mg series recycled aluminum alloy is 0.01% to 4.0%, and the mass percentage of Mg is 0.01% to 4.0%.

12. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The mass of the Al-MgAl2O4 master alloy is 5%-30% of the mass of the recycled aluminum alloy; and / or, the step 2) is carried out in air.

13. The method for recycling recycled aluminum alloy according to claim 1, characterized in that: The casting solidification molding in step 3) is selected from one or more combinations of gravity, high pressure, extrusion, low pressure, and differential pressure casting; and / or, during the casting solidification molding in step 3), the solidification rate is above 0.5°C / s.

14. A recycled aluminum alloy obtained by the method for recycling a secondary aluminum alloy according to any one of claims 1 to 13.

15. The recycled aluminum alloy according to claim 14, characterized in that The iron-containing phase in the recycled aluminum alloy is in the form of fine particles and / or worms, with an aspect ratio of less than 2.5 and a length of less than 20 μm.

16. Use of the recycled aluminum alloy according to claim 14 or 15 in the preparation of automobile chassis structural parts, engines or transmission components.

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