A rare earth modified aluminum alloy and its preparation method and application

Abstract

The present invention relates to the technical field of alloy materials, and specifically discloses a rare earth modified aluminum alloy and a preparation method and application thereof. The rare earth modified aluminum alloy includes Be and RE elements, wherein the RE includes a light rare earth component and a heavy rare earth component, and the percentage of the chemical composition of the rare earth modified aluminum alloy satisfies 0.3%≤RE+Be+Ti≤0.45%. The present invention utilizes the combined action of rare earth elements, Be and Ti to modify and refine the aluminum silicon alloy, and successfully obtains an A356 aluminum alloy with a high degree of grain refinement and small and uniform secondary dendrite spacing, which makes up for the defects of the A356 aluminum alloy in the prior art. The present invention effectively solves the problem in the prior art that the A356 alloy after grain refinement by Sr and rare earth composite modifier still has limited grain refinement effect, and the different secondary dendrite spacing leads to differences in alloy performance stability, and provides a new idea for the research and development of eutectic aluminum silicon alloy.

Description

Technical Field

[0001] The invention relates to the technical field of alloy materials, and specifically discloses a rare earth modified aluminum alloy and a preparation method and application thereof. Background Art

[0002] A356 aluminum alloy is a casting aluminum alloy developed in the 1970s. It is a type of hypoeutectic aluminum-silicon alloy. A356 aluminum alloy has high specific strength and corrosion resistance, and low preparation cost. It is widely used in the aerospace field and the automotive industry. In particular, more than 80% of the aluminum alloys for automobile wheels cast by low-pressure casting and spin casting are A356 hypoeutectic aluminum-silicon alloys. After proper heat treatment, this alloy can be used as most automobile wheel materials, but there is still room for improvement in its mechanical properties. Based on this, engineers have conducted a lot of research on A356 aluminum alloy.

[0003] The study found that the microstructure of A356 aluminum alloy without refinement and modification is coarse dendrite α-Al and lamellar eutectic silicon. Coarse dendrites are prone to cause component segregation. Unmodified eutectic Si has sharp tips, which will form stress concentration during the stress process, severely split the matrix, and cause the alloy to break and damage under lower stress, reducing the performance of the alloy. At present, Sr is a good modifier used in eutectic aluminum silicon alloy, but it has the disadvantage of hydrogen absorption. There are also reports on the use of Sr and rare earth to modify eutectic aluminum silicon alloy, but there are still problems such as limited grain refinement effect, different sizes of secondary dendrite spacing, and different performance stability of the obtained aluminum alloy. Based on this, the development of an aluminum alloy with better grain refinement effect and more stable performance has great practical significance for the application of A356 aluminum alloy. Summary of the invention

[0004] Aiming at the problems that the A356 alloy after being refined by Sr and rare earth composite modifier in the prior art still has limited refining effect and the different secondary dendrite spacing leads to different alloy performance stability, the present invention provides a rare earth modified aluminum alloy and a preparation method and application thereof, and utilizes the combined action of rare earth elements, Be and Ti to modify and refine the aluminum silicon alloy, and successfully obtains an A356 aluminum alloy with high refining degree and small and uniform secondary dendrite spacing, which makes up for the defects of the A356 aluminum alloy in the prior art and provides a new idea for the research and development of aluminum silicon alloy.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A first aspect of the present invention provides a rare earth modified aluminum alloy, wherein the mass percentage of the chemical components of the rare earth modified aluminum alloy is: Si: 6.00%-8.00%, Mg: 0.28%-0.40%, Cu: 0.10%-0.30%, Fe: 0.15%-0.25%, Zn: 0.05%-0.15%, Mn: 0.03%-0.08%, Be: 0.10%-0.20%, Ti: 0.10%-0.25%, RE: 0.05%-0.15% and the remainder of Al and unavoidable impurities; wherein the RE includes a light rare earth component and a heavy rare earth component, and the percentage of the chemical components of the rare earth modified aluminum alloy satisfies 0.3%≤RE+Be+Ti≤0.45%.

[0007] The present invention adds Be, Ti and RE elements to the A356 aluminum alloy to form a rare earth modified aluminum alloy with excellent performance. The addition of Be changes the growth mode of eutectic Si, mainly twinning growth, to achieve the purpose of refining eutectic Si; the addition of Ti is to form TiAl with Al element in the matrix. 3 It acts as a nucleation core to accelerate the nucleation of α-Al, thereby refining the α-Al grains. The presence of rare earth elements can not only strengthen the formation of secondary dendrites of aluminum alloys, reduce the dendrite spacing, and effectively refine the internal structure of the grains, thereby achieving a strengthening effect on the performance of aluminum alloys; it can also form a needle-shaped alloy strengthening phase with Al in the aluminum alloy, which is beneficial to reduce the solid solution-precipitation effect at high temperature, hinder the grain boundary sliding, and further strengthen the alloy matrix.

[0008] Furthermore, heavy rare earth elements can provide more prominent solid solution strengthening and aging strengthening effects on aluminum alloys, and can also further improve the refinement effect of α-Al grains, thereby strengthening the mechanical properties of aluminum alloys. Light rare earth elements can react with other metal elements to form high-melting-point intermetallic compounds, which can not only eliminate coarse blocky structures, but also make up for the crystal defects of the aluminum alloy phase, refine the structure, and improve the uniformity of the secondary dendrite spacing, so as to achieve the effect of stabilizing the grain boundaries and improving the performance stability of the aluminum alloy. The present invention also sets the mass percentage of RE+Be+Ti to ensure that the secondary dendrite spacing of the obtained aluminum alloy is small and uniform, control the refinement degree of α-Al grains, avoid excessive metamorphism, and the grain size of α-Al grains becomes larger, thereby reducing the performance stability of the aluminum alloy.

[0009] Preferably, the mass ratio of the light rare earth component to the heavy rare earth component is 1:0.1-1:0.3.

[0010] Preferably, the light rare earth component is any one of Ce or Nb.

[0011] Preferably, the heavy rare earth component is any one of Dy, Ho, Er or Y.

[0012] The second aspect of the present invention provides a method for preparing the rare earth modified aluminum alloy, comprising the following steps:

[0013] Step 1, in an inert atmosphere, Al-RE master alloy and Al-Ti master alloy are mixed according to the designed ratio of chemical components, and smelted at 500°C-650°C for a first time, and kept warm to obtain Al-RE-Ti alloy liquid; Al-Be master alloy is added to the Al-RE-Ti alloy liquid, and then the temperature is raised to 720°C-800°C for secondary smelting to obtain Al-RE-Ti-Be alloy liquid;

[0014] Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-RE-Ti-Be alloy liquid according to the designed ratio of chemical components, and smelting at 800° C.-850° C. to obtain a mixed alloy liquid; adding a refining agent to the mixed alloy liquid, cooling the temperature to 600° C.-650° C. for insulation, and pouring to obtain an aluminum alloy ingot;

[0015] Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 560°C-600°C, and then subjecting it to aging heat treatment at 200°C-250°C to obtain a rare earth modified aluminum alloy.

[0016] Preferably, in step 1, the holding time of the primary smelting is 2h-5h.

[0017] Preferably, in step 1, the holding time of the secondary smelting is 3h-6h.

[0018] Preferably, in step 2, the refining agent comprises the following raw material components in percentage by mass: 35%-40% quartz sand, 15%-20% fluorite and the remainder industrial sodium salt.

[0019] Preferably, in step 2, the amount of the refining agent added is 0.1%-0.5% of the mass of the mixed alloy liquid.

[0020] Preferably, in step 2, the smelting holding time is 1h-3h.

[0021] Preferably, in step 2, the insulation time is 8h-12h.

[0022] Preferably, in step three, the holding time of the solution heat treatment is 10h-12h.

[0023] Preferably, in step three, the holding time of the aging heat treatment is 4h-6h.

[0024] The third aspect of the present invention provides the application of the rare earth modified aluminum alloy in the automotive industry.

[0025] In summary, the present invention provides a rare earth modified aluminum alloy and a preparation method and application thereof, and utilizes the combined action of rare earth elements, Be and Ti to modify and refine the aluminum silicon alloy, and successfully obtains an A356 aluminum alloy with high degree of grain refinement, small and uniform secondary dendrite spacing, which makes up for the defects of the A356 aluminum alloy in the prior art. The technical solution of the present invention effectively solves the problem that the A356 alloy after grain refinement by Sr and rare earth composite modifier in the prior art still has limited grain refinement effect, and the different secondary dendrite spacing leads to different alloy performance stability, which provides a new idea for the research and development of eutectic aluminum silicon alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the metallographic structure diagram of the rare earth modified aluminum alloy obtained in Example 1;

[0027] Figure 2 The metallographic structure diagram of the rare earth modified aluminum alloy obtained in Example 2;

[0028] Figure 3 The metallographic structure diagram of the rare earth modified aluminum alloy obtained in Comparative Example 1;

[0029] Figure 4 This is the metallographic structure diagram of the rare earth modified aluminum alloy obtained in Comparative Example 2. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment provides a rare earth modified aluminum alloy, which specifically includes the following contents:

[0033] The mass percentage of the chemical components of the rare earth modified aluminum alloy is: Si: 7%, Mg: 0.34%, Cu: 0.24%, Fe: 0.16%, Zn: 0.11%, Mn: 0.06%, Be: 0.12%, Ti: 0.17%, Ce: 0.10%, Dy: 0.01% and the balance of Al and unavoidable impurities;

[0034] The preparation method of the rare earth modified aluminum alloy comprises the following steps:

[0035] Step 1, weighing each master alloy according to the designed ratio, mixing the Al-Ce master alloy, Al-Dy master alloy and Al-Ti master alloy according to the designed ratio of chemical composition in an inert atmosphere, performing a primary smelting at 600° C., and keeping the temperature for 3 hours to obtain Al-Ce and Dy-Ti alloy liquids; adding Al-Be master alloy to the Al-Ce and Dy-Ti alloy liquids, and then heating to 750° C. for secondary smelting to obtain Al-Ce and Dy-Ti-Be alloy liquids;

[0036] Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-Ce and Dy-Ti-Be alloy liquids according to the designed ratio of chemical components, heating to 830° C. for smelting to obtain a mixed alloy liquid; adding 0.3wt% of a refining agent to the mixed alloy liquid, cooling to 650° C. for 10 hours, and pouring to obtain an aluminum alloy ingot;

[0037] Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 580° C. and keeping the temperature for 11 hours, then cooling the temperature to 230° C. and conducting aging heat treatment and keeping the temperature for 5 hours to obtain a rare earth modified aluminum alloy.

[0038] Example 2

[0039] This embodiment provides a rare earth modified aluminum alloy, which specifically includes the following contents:

[0040] The mass percentage of the chemical components of the rare earth modified aluminum alloy is: Si: 7%, Mg: 0.34%, Cu: 0.24%, Fe: 0.16%, Zn: 0.11%, Mn: 0.06%, Be: 0.12%, Ti: 0.17%, Nb: 0.10%, Dy: 0.01% and the balance of Al and unavoidable impurities;

[0041] The preparation method of the rare earth modified aluminum alloy comprises the following steps:

[0042] Step 1, weighing each master alloy according to the designed ratio, mixing the Al-Nb master alloy, the Al-Dy master alloy and the Al-Ti master alloy according to the designed ratio of chemical composition in an inert atmosphere, performing a primary smelting at 600° C., and keeping the temperature for 3 hours to obtain Al-Nb and Dy-Ti alloy liquids; adding Al-Be master alloy to the Al-Nb and Dy-Ti alloy liquids, and then heating to 750° C. for secondary smelting to obtain Al-Nb and Dy-Ti-Be alloy liquids;

[0043] Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-Nb and Dy-Ti-Be alloy liquids according to the designed ratio of chemical components, heating to 830° C. for smelting to obtain a mixed alloy liquid; adding 0.3wt% of a refining agent to the mixed alloy liquid, cooling to 650° C. for 10 hours, and pouring to obtain an aluminum alloy ingot;

[0044] Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 580° C. and keeping the temperature for 11 hours, then cooling the temperature to 230° C. and conducting aging heat treatment and keeping the temperature for 5 hours to obtain a rare earth modified aluminum alloy.

[0045] Example 3

[0046] This embodiment provides a rare earth modified aluminum alloy, which specifically includes the following contents:

[0047] The mass percentage of the chemical components of the rare earth modified aluminum alloy is: Si: 0.62%, Mg: 0.40%, Cu: 0.12%, Fe: 0.17%, Zn: 0.13%, Mn: 0.04%, Be: 0.12%, Ti: 0.17%, Ce: 0.10%, Er: 0.01% and the balance of Al and unavoidable impurities;

[0048] The preparation method of the rare earth modified aluminum alloy comprises the following steps:

[0049] Step 1, weighing each master alloy according to the designed ratio, mixing the Al-Ce master alloy, Al-Er master alloy and Al-Ti master alloy according to the designed ratio of chemical composition under an inert atmosphere, performing a primary smelting at 600° C., and keeping the temperature for 3 hours to obtain Al-Ce and Er-Ti alloy liquids; adding Al-Be master alloy to the Al-Ce and Er-Ti alloy liquids, and then heating to 750° C. for secondary smelting to obtain Al-Ce and Er-Ti-Be alloy liquids;

[0050] Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-Ce and Er-Ti-Be alloy liquids according to the designed ratio of chemical components, heating to 830° C. for smelting to obtain a mixed alloy liquid; adding 0.25wt% of a refining agent to the mixed alloy liquid, cooling to 650° C. for 10 hours, and pouring to obtain an aluminum alloy ingot;

[0051] Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 570° C. and keeping the temperature for 12 hours, then cooling the temperature to 230° C. and conducting aging heat treatment and keeping the temperature for 5 hours to obtain a rare earth modified aluminum alloy.

[0052] Example 4

[0053] This embodiment provides a rare earth modified aluminum alloy, which specifically includes the following contents:

[0054] The mass percentage of the chemical composition of the rare earth modified aluminum alloy is: Si: 6.83%, Mg: 0.31%, Cu: 0.26%, Fe: 0.16%, Zn: 0.14%, Mn: 0.03%, Be: 0.17%, Ti: 0.15%, Ce: 0.10%, Y: 0.02% and the balance of Al and unavoidable impurities;

[0055] The preparation method of the rare earth modified aluminum alloy comprises the following steps:

[0056] Step 1, weighing each master alloy according to the designed ratio, mixing the Al-Ce master alloy, Al-Y master alloy and Al-Ti master alloy according to the designed ratio of chemical composition under an inert atmosphere, performing a primary smelting at 600° C., and keeping the temperature for 3 hours to obtain Al-Ce and Y-Ti alloy liquids; adding Al-Be master alloy to the Al-Ce and Y-Ti alloy liquids, and then heating to 750° C. for secondary smelting to obtain Al-Ce and Y-Ti-Be alloy liquids;

[0057] Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-Ce and Y-Ti-Be alloy liquids according to the designed ratio of chemical components, heating to 830° C. for smelting to obtain a mixed alloy liquid; adding 0.3wt% of a refining agent to the mixed alloy liquid, cooling to 650° C. for 10 hours, and pouring to obtain an aluminum alloy ingot;

[0058] Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 580° C. and keeping the temperature for 11 hours, then cooling the temperature to 230° C. and conducting aging heat treatment and keeping the temperature for 5 hours to obtain a rare earth modified aluminum alloy.

[0059] Comparative Example 1

[0060] This comparative example provides a rare earth modified aluminum alloy, which is different from Example 1 in that Be in the rare earth modified aluminum alloy is replaced by an equal amount of Sr, specifically including the following contents:

[0061] The mass percentage of the chemical components of the rare earth modified aluminum alloy is: Si: 7%, Mg: 0.34%, Cu: 0.24%, Fe: 0.16%, Zn: 0.11%, Mn: 0.06%, Sr: 0.12%, Ti: 0.17%, Ce: 0.10%, Dy: 0.01% and the balance of Al and unavoidable impurities;

[0062] The preparation method of the rare earth modified aluminum alloy comprises the following steps:

[0063] Step 1, weighing each master alloy according to the designed ratio, mixing the Al-Ce master alloy, the Al-Dy master alloy and the Al-Ti master alloy according to the designed ratio of chemical composition under an inert atmosphere, performing a primary smelting at 600° C., and keeping the temperature for 3 hours to obtain an Al-RE-Ti alloy liquid; adding an Al-Sr master alloy to the Al-RE-Ti alloy liquid, and then heating to 750° C. for secondary smelting to obtain an Al-RE-Ti-Be alloy liquid;

[0064] Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-RE-Ti-Be alloy liquid according to the designed ratio of chemical components, heating to 830° C. for smelting to obtain a mixed alloy liquid; adding 0.3wt% of a refining agent to the mixed alloy liquid, cooling to 650° C. for 10 hours, and pouring to obtain an aluminum alloy ingot;

[0065] Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 580° C. and keeping the temperature for 11 hours, then cooling the temperature to 230° C. and conducting aging heat treatment and keeping the temperature for 5 hours to obtain a rare earth modified aluminum alloy.

[0066] Comparative Example 2

[0067] This comparative example provides a rare earth modified aluminum alloy, which is different from Example 1 in that the rare earth modified aluminum alloy meets the requirement of RE+Be+Ti being 0.5%, and specifically includes the following contents:

[0068] The mass percentage of the chemical components of the rare earth modified aluminum alloy is: Si: 7.00%, Mg: 0.34%, Cu: 0.24%, Fe: 0.16%, Zn: 0.11%, Mn: 0.06%, Be: 0.16%, Ti: 0.20%, Ce: 0.13%, Dy: 0.01% and the balance of Al and unavoidable impurities;

[0069] The preparation method of the rare earth modified aluminum alloy comprises the following steps:

[0070] Step 1, weighing each master alloy according to the designed ratio, mixing the Al-Ce master alloy, the Al-Dy master alloy and the Al-Ti master alloy according to the designed ratio of chemical composition under an inert atmosphere, performing a primary smelting at 600° C., and keeping the temperature for 3 hours to obtain an Al-RE-Ti alloy liquid; adding an Al-Be master alloy to the Al-RE-Ti alloy liquid, and then heating to 750° C. for secondary smelting to obtain an Al-RE-Ti-Be alloy liquid;

[0071] Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-RE-Ti-Be alloy liquid according to the designed ratio of chemical components, heating to 830° C. for smelting to obtain a mixed alloy liquid; adding 0.3wt% of a refining agent to the mixed alloy liquid, cooling to 650° C. for 10 hours, and pouring to obtain an aluminum alloy ingot;

[0072] Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 580° C. and keeping the temperature for 11 hours, then cooling the temperature to 230° C. and conducting aging heat treatment and keeping the temperature for 5 hours to obtain a rare earth modified aluminum alloy.

[0073] In order to further verify the technical effect of the present invention, the present invention conducted metallographic structure tests on the rare earth modified aluminum alloys obtained in Examples 1-2 and Comparative Examples 1-2, and observed them using a ZEISS Axio Observer A1m metallographic microscope. The specific test results are as follows: Figure 1-4 As shown. Figure 1 It can be seen that the secondary dendrite spacing of the rare earth modified aluminum alloy obtained in Example 1 is small and uniform, and α-Al has no long columnar crystals, mostly equiaxed crystals. The secondary dendrite spacing of the rare earth modified aluminum alloy obtained in Example 2 is small and uniform, but there are a small number of long columnar crystals, most of which are equiaxed crystals. The rare earth modified aluminum alloy obtained in Comparative Example 1 is uniform, but the secondary dendrite spacing is large, and there is a local Si segregation phenomenon; the rare earth modified aluminum alloy obtained in Comparative Example 2 not only has a large secondary dendrite spacing, but also has a local Si segregation phenomenon, and the crystal morphology is poor.

[0074] The present invention also tests the tensile strength and yield strength of the rare earth modified aluminum alloys obtained in Examples 1-4 and Comparative Examples 1-2, with reference to standard GB / T16865-2013; the hardness test refers to standard GB / T231.1-2018, and the results are shown in Table 1, and the elongation refers to standard GB / 228.1-2010.

[0075] Table 1 Mechanical properties test results of rare earth modified aluminum alloys obtained in various embodiments and comparative examples

[0076]

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A rare earth modified aluminum alloy, characterized in that: The mass percentage of the chemical components of the rare earth modified aluminum alloy is: Si: 6.00%-8.00%, Mg: 0.28%-0.40%, Cu: 0.10%-0.30%, Fe: 0.15%-0.25%, Zn: 0.05%-0.15%, Mn: 0.03%-0.08%, Be: 0.10%-0.20%, Ti: 0.10%-0.25%, RE: 0.05%-0.15% and the balance of Al and inevitable impurities; wherein the RE includes a light rare earth component and a heavy rare earth component, and the percentage of the chemical components of the rare earth modified aluminum alloy satisfies 0.3%≤RE+Be+Ti≤0.45%; The method for preparing the rare earth modified aluminum alloy comprises the following steps: Step 1, in an inert atmosphere, Al-RE master alloy and Al-Ti master alloy are mixed according to the designed ratio of chemical components, and smelted at 500°C-650°C for a first time, and kept warm to obtain Al-RE-Ti alloy liquid; Al-Be master alloy is added to the Al-RE-Ti alloy liquid, and then the temperature is raised to 720°C-800°C for secondary smelting to obtain Al-RE-Ti-Be alloy liquid; Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-RE-Ti-Be alloy liquid according to the designed ratio of chemical components, and smelting at 800° C.-850° C. to obtain a mixed alloy liquid; adding a refining agent to the mixed alloy liquid, cooling the temperature to 600° C.-650° C. for insulation, and pouring to obtain an aluminum alloy ingot; Step 3, subjecting the aluminum alloy ingot to solution heat treatment at 560° C.-600° C., and then subjecting the ingot to aging heat treatment at 200° C.-250° C., to obtain a rare earth modified aluminum alloy; The mass ratio of the light rare earth component to the heavy rare earth component is 1:0.1-1:0.3; The light rare earth component is any one of Ce or Nb; The heavy rare earth component is any one of Dy, Ho, Er or Y.

2. A method for preparing a rare earth modified aluminum alloy as claimed in claim 1, characterized in that: The steps include: Step 1, in an inert atmosphere, Al-RE master alloy and Al-Ti master alloy are mixed according to the designed ratio of chemical components, and smelted at 500°C-650°C for a first time, and kept warm to obtain Al-RE-Ti alloy liquid; Al-Be master alloy is added to the Al-RE-Ti alloy liquid, and then the temperature is raised to 720°C-800°C for secondary smelting to obtain Al-RE-Ti-Be alloy liquid; Step 2, adding Al-Si master alloy, Al-Mg master alloy, Al-Cu master alloy, Al-Fe master alloy, Al-Zn master alloy and Al-Mn master alloy to the Al-RE-Ti-Be alloy liquid according to the designed ratio of chemical components, and smelting at 800° C.-850° C. to obtain a mixed alloy liquid; adding a refining agent to the mixed alloy liquid, cooling the temperature to 600° C.-650° C. for insulation, and pouring to obtain an aluminum alloy ingot; Step 3: subjecting the aluminum alloy ingot to solution heat treatment at 560°C-600°C, and then subjecting it to aging heat treatment at 200°C-250°C to obtain a rare earth modified aluminum alloy.

3. The method for preparing the rare earth modified aluminum alloy according to claim 2, characterized in that: In step 1, the holding time of the first smelting is 2h-5h; and / or In step 1, the holding time of the secondary smelting is 3h-6h.

4. The method for preparing the rare earth modified aluminum alloy according to claim 2, characterized in that: In step 2, the refining agent includes the following raw material components in percentage by weight: 35%-40% quartz sand, 15%-20% fluorite and the balance of industrial sodium salt.

5. The method for preparing the rare earth modified aluminum alloy according to claim 2 or 4, characterized in that: In step 2, the amount of the refining agent added is 0.1%-0.5% of the mass of the mixed alloy liquid.

6. The method for preparing the rare earth modified aluminum alloy according to claim 2, characterized in that: In step 2, the smelting holding time is 1h-3h; and / or In step 2, the insulation time is 8h-12h.

7. The method for preparing a rare earth modified aluminum alloy according to claim 2, characterized in that: In step 3, the holding time of the solution heat treatment is 10h-12h; and / or In step three, the holding time of the aging heat treatment is 4h-6h.

8. Application of the rare earth modified aluminum alloy as claimed in claim 1 in the automotive industry.

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