High-elongation die-casting Al-Mg alloy and preparation method and application thereof

Abstract

The invention provides an elongation die-casting Al-Mg alloy as well as a preparation method and application thereof. The high-elongation die-casting Al-Mg alloy comprises the following components in percentage by mass: 4.00 to 7.50 percent of Mg, 0.10 to 0.70 percent of Mn, 0.05 to 0.50 percent of Fe, 0.50 to 3.00 percent of Si, 0.0010 to 0.0090 percent of B, 0.02 to 0.30 percent of Ti, 0.05 to 0.30 percent of Zn and the balance of Al. According to the elongation die-casting Al-Mg alloy, the tensile strength is 310-340 MPa, the yield strength is 160-200 MPa, and the elongation is 20%-34%. According to the method, the Al-Mg alloy with the high elongation rate can be prepared at low cost by cooperatively regulating and controlling the three aspects of alloy components, TiB2 nanocrystalline alloy addition and die casting process parameters, and the method is suitable for batch industrial production.

Description

Technical Field

[0001] The invention relates to aluminum alloy technology, and in particular to a high-elongation die-casting Al-Mg alloy, a preparation method and application thereof. Background Art

[0002] With the rapid development of the automotive industry and the requirements for lightweight automobiles, the demand for die-cast aluminum alloys will continue to increase. Due to the complicated processing process of deformed aluminum alloys and the long production cycle, the near-net formability of die-cast aluminum alloys can directly obtain parts with complex structures, which improves production efficiency and reduces production costs. Al-Mg alloys are a type of aluminum alloy commonly used in die-casting, with strong corrosion resistance and excellent mechanical properties at room temperature. However, the casting performance of the alloy is poor, the mechanical properties are greatly affected by the wall thickness, and the tendency to hot cracking is serious. At the same time, limited by the coupling of flow and solidification under die-casting conditions, the micro-alloying method under gravity casting conditions has limited control over the alloy structure, especially the elongation is difficult to meet the further demand for die-casting alloys for large-scale thin-walled car body parts. For the development of Al-Mg alloy forming and service performance, the alloying of elements such as Mg and Si is currently the main approach. Although the increase in Mg content can increase the strength of the alloy, it will widen the solidification range of the alloy and make the casting performance worse. The addition of Si content can improve the casting performance of the alloy, but the formation of Mg2Si phase will sharply deteriorate the elongation of the alloy. Therefore, combining the characteristics of Al-Mg alloy itself with the characteristics of the die-casting process itself, developing a microalloying method suitable for fast flow and high solidification rate of die-casting, and then simultaneously improving the preparation method of Al-Mg alloy forming and elongation, has become a technical problem to be urgently solved in this field. Summary of the invention

[0003] The purpose of the present invention is to address the problem that it is difficult to improve the elongation of Al-Mg alloy die-castings currently prepared by die-casting technology, and to propose a high-elongation die-casting Al-Mg alloy with excellent mechanical properties and fewer structural defects.

[0004] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising", etc. and similar meanings, as well as closed-ended "composed of", "composed of", etc. and similar meanings.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a high elongation die-casting Al-Mg alloy, the composition of which is: Mg: 4.00-7.50wt.%, Mn: 0.10-0.70wt.%, Fe: 0.05-0.50wt.%, Si: 0.50-3.00wt.%, B: 0.0010-0.0090wt.%, Ti: 0.02-0.30wt.%, Zn: 0.05-0.30wt.%, and the balance is Al.

[0006] Furthermore, the high elongation die-casting Al-Mg alloy composition is preferably: Mg: 5.00-6.50wt.%, Mn: 0.20-0.55wt.%, Fe: 0.10-0.30wt.%, Si: 1.00-2.60wt.%, B: 0.0040-0.0080wt.%, Ti: 0.08-0.18wt.%, Zn: 0.05-0.30wt.%, and the balance is Al.

[0007] Furthermore, the high elongation die-cast Al-Mg alloy has a tensile strength of 310 MPa-340 MPa, a yield strength of 160 MPa-200 MPa, and an elongation of 20%-34%.

[0008] Another object of the present invention is to disclose a method for preparing a high elongation die-cast Al-Mg alloy, comprising the following steps:

[0009] Step (1) smelting: melting industrial pure aluminum, adding Al-Mn, Al-Si, Al-Ti, pure Zn and pure Mg in sequence after the aluminum ingot is completely melted, refining under the condition of passing inert gas, adding TiB2 nanocrystalline seed alloy during the refining process (degassing process), and slagging and heat preservation after the refining is completed;

[0010] Step (2) high pressure die casting: heating the mold and the blank, pouring aluminum liquid into the barrel, and after the die casting is completed, taking the casting out of the separated mold and air cooling it to prepare a high elongation die-casting Al-Mg alloy.

[0011] The preparation method of the high elongation die-cast Al-Mg alloy of the present invention has simple process and low cost, and the elongation of the prepared die-cast alloy is significantly improved, which can better meet the service requirements.

[0012] Furthermore, the smelting in step (1) is as follows: the pure aluminum ingot is melted at 730-800°C, and then Al-Mn, Al-Si, Al-Ti, pure Zn, and pure Mg are added in sequence, and kept warm at 750-780°C for 1-3h. To ensure uniform diffusion of the elements, the aluminum liquid temperature is then reduced to 700-720°C, and refined under the condition of the rotor rotating and introducing inert gas. The total refining time is 10-25min. When the refining is carried out for 5-10min, TiB2 nanocrystalline seed alloy is added, that is, TiB2 nanocrystalline seed alloy is added during the refining process. This addition order can ensure the impurity removal effect and avoid burning. After the refining is completed, slag is removed and the alloy liquid is then kept warm.

[0013] Furthermore, the content of Mn in the Al-Mn is 5%-30%, preferably 10%.

[0014] Furthermore, the content of Si in the Al-Si is 5%-30%, preferably 10%.

[0015] Furthermore, the content of Ti in the Al-Ti is 5%-30%, preferably 10%.

[0016] Furthermore, the rotor speed is 240-520 r / min, preferably 358-438 r / min.

[0017] Furthermore, the insulation time in step (1) is 10-30 minutes, preferably 15 minutes.

[0018] Furthermore, the inert gas in step (1) is nitrogen and / or argon, preferably argon, and the flow rate of the inert gas is 3-9 L / min, preferably 7-8 L / min.

[0019] Furthermore, the insulation temperature of step (1) is 745-785° C., and the insulation time is 1.5-2 h.

[0020] Furthermore, the refining time in step (1) is 15-20 minutes.

[0021] Furthermore, an auxiliary process is used during refining in step (1), wherein the auxiliary process is ultrasonic melt vibration, and the ultrasonic melt vibration time is 5-15 minutes. The use of ultrasonic vibration technology can promote the degassing effect and element dissolution.

[0022] Furthermore, the TiB2 nanocrystalline seed alloy in step (1) is nanoparticles with a particle size of 50nm-300nm.

[0023] Furthermore, the aluminum liquid pouring temperature in step (2) is 680-720°C, preferably 700-710°C.

[0024] Furthermore, in step (2), the mold is heated to maintain a mold temperature of 170-230°C, preferably 190°C-210°C.

[0025] Furthermore, the die-casting parameters of step (2) are: slow injection speed is 0.1-0.6 m / s, preferably 0.22-0.43 m / s, fast injection speed is 1 m / s-6 m / s, preferably 2.0-4.5 m / s, and holding pressure is 100-120 MPa.

[0026] Another object of the present invention is to disclose the use of a high elongation die-casting Al-Mg alloy in the field of preparing aluminum alloy die-castings for automobiles.

[0027] Furthermore, the high elongation die-casting Al-Mg alloy of the present invention is particularly suitable for preparing heat-treatment-free Al-Si alloy die-castings for automobiles.

[0028] The high elongation die-cast Al-Mg alloy of the present invention, its preparation method and use have the following advantages compared with the prior art:

[0029] 1) The present invention adopts a specific TiB2 nanocrystalline seed alloy, an addition amount and an addition process to successfully achieve the regulation of the solidification structure in the Al-Mg alloy, thereby improving the elongation. The uniformity of the structure in the die casting is closely related to the rheological shear behavior of the solid-liquid mixed phase in the holding stage. When the Mg content in the Al-Mg alloy is increased, the solid-liquid two-phase region will expand, thereby aggravating the aggregation of the liquid phase during the shear deformation of the solid-liquid mixed phase in the cavity, thereby causing the inhomogeneity of the structure and the macro-segregation to increase. By introducing a trace amount of TiB2 particles, the nucleation supercooling of the α-Al grains can be reduced, heterogeneous nucleation can be promoted, and the solid phase fraction gradient caused by the temperature gradient in the cavity can be weakened, thereby improving the uniformity of the structure of the die-cast Al-Mg alloy and improving the elongation. However, most of the Al-Ti-B seed alloys commonly used in industry, such as Al-3Ti-B and Al-5Ti-B, are micron-sized particles, and the effect is not obvious under high-pressure casting conditions. Therefore, it is necessary to use particles suitable for solidification conditions with high cooling rates. Since the increase of B element will significantly increase the viscosity of the melt, thereby deteriorating the filling performance of the alloy in the die casting process, the amount of particles added is crucial. This patent application has been verified through a large number of experiments: for the target component aluminum alloy, when the TiB2 particle size is 50-300nm, and the B and Ti contents in the alloy are 0.0040-0.0080% and 0.08-0.20% respectively, the organizational optimization effect is most obvious.

[0030] 2) The present invention optimizes the structure of die-cast Al-Mg alloy by online addition of TiB2 nano-seed alloy. The promoting effect of TiB2 particles on α-Al heterogeneous nucleation is closely related to the alloy system and solidification environment. In addition, the dispersion degree of particles is also crucial to the actual effect. Therefore, a suitable addition method (such as online addition of TiB2 nano-seed alloy) is the guarantee for obtaining the target solidification structure. For the die-casting of target component Al-Mg alloy, in order to ensure that the particles are fully in contact with the melt and have sufficient incubation time, it is necessary to select a suitable addition temperature and addition method. In order to further promote the contact and wetting of nano-TiB2 with the melt, melt processing auxiliary technology (such as ultrasonic melt vibration) is also required. This patent application has been verified through a large number of experiments: for the target alloy composition, TiB2 nanocrystalline seed alloy is added online when the rotary degassing is carried out for 5-10 minutes, and ultrasonic vibration treatment is added at the same time. The ultrasonic time is 5 minutes, the rotor speed is 358-438r / min, and the refining time is 15-20 minutes. The use of the TiB2 nanocrystalline seed alloy can effectively refine the grain size of the die-casting, reduce defects, and achieve a synergistic improvement in the strength and plasticity of the Al-Mg alloy.

[0031] In summary, the preparation method of the high elongation die-casting Al-Mg alloy of the present invention has easy conditions to implement, low production cost, and can be suitable for industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the optical microstructure diagram of the die-casting structure of Comparative Example 1;

[0033] Figure 2 This is the optical microstructure diagram of the die-casting structure of Comparative Example 2;

[0034] Figure 3 This is the optical microstructure diagram of the die-casting structure of Example 1;

[0035] Figure 4 This is the optical microstructure diagram of the die-casting structure of Example 2. DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to the examples. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0037] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0038] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0039] In the present specification, a numerical range expressed using "above" or "below" means a numerical range including the number.

[0040] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0041] In this specification, the use of "optional" or "optional" indicates that certain substances, components, execution steps, application conditions and other factors are used or not used.

[0042] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 15-25°C.

[0043] In this manual, the reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.

[0044] Comparative Example 1

[0045] Comparative Example 1 discloses a method for preparing a die-cast Al-Mg alloy, comprising the following components in mass percentage: Mg: 6.13%, Mn: 0.53%, Fe: 0.13%, Si: 1.01%, Ti: 0.09%, Zn: 0.13%, and the balance is Al. The preparation method comprises the following steps:

[0046] Step (1) smelting: melt the pure aluminum ingot at 780°C, then add Al-10Mn, Al-10Si, Al-10Ti, pure Zn and pure Mg in sequence, keep warm at 800°C for 1h to ensure uniform diffusion of the elements, then reduce the aluminum liquid temperature to 720°C, and refine under the condition of rotating the rotor and introducing argon gas at a speed of 360r / min for 20min. The melt is subjected to ultrasonic vibration treatment for 5min. After refining, slag is removed, and then the alloy liquid is allowed to stand for 15min and cooled to a pouring temperature of 705°C for die casting.

[0047] Step (2) high pressure die casting: the mold temperature is maintained at 200°C, the slow injection speed is 0.31m / s, the fast injection speed is 3m / s, the holding pressure is 110MPa, and after the die casting is completed, it is taken out and air-cooled to prepare a die-cast Al-Mg alloy.

[0048] Comparative Example 2

[0049] Comparative Example 2 discloses a method for preparing a die-cast Al-Mg alloy, comprising the following components in mass percentage: Mg: 6.13%, Mn: 0.53%, Fe: 0.13%, Si: 1.01%, B: 0.0063%, Ti: 0.11%, Zn: 0.13%, and the balance is Al. The preparation method comprises the following steps:

[0050] Step (1) smelting: melt the pure aluminum ingot at 780°C, then add Al-10Mn, Al-10Si, Al-10Ti, pure Zn and pure Mg in sequence, keep warm at 800°C for 1h to ensure uniform diffusion of the elements, then reduce the aluminum liquid temperature to 720°C, and refine under the condition of rotating the rotor and introducing argon gas at a speed of 360r / min for 20min. The melt is subjected to ultrasonic vibration treatment for 5min. After refining, add nano-TiB2 seed alloy and stir manually for 30s. Then, the alloy liquid is allowed to stand for 15min before slagging and cooling to the pouring temperature of 705°C for die casting.

[0051] Step (2) high pressure die casting: the mold temperature is maintained at 200°C, the slow injection speed is 0.31m / s, the fast injection speed is 3m / s, the holding pressure is 110MPa, and after the die casting is completed, it is taken out and air-cooled to prepare a die-cast Al-Mg alloy.

[0052] Example 1

[0053] This embodiment 1 discloses a method for preparing a high elongation die-cast Al-Mg alloy, comprising the following components in mass percentage: Mg: 6.13%, Mn: 0.53%, Fe: 0.13%, Si: 1.01%, B: 0.0063%, Ti: 0.11%, Zn: 0.13%, and the balance is Al. The preparation method comprises the following steps:

[0054] Step (1) smelting: melt the pure aluminum ingot at 780-800°C, then add Al-10Mn, Al-10Si, Al-10Ti, pure Zn and pure Mg in sequence, keep warm at 800°C for 1h to ensure uniform diffusion of the elements, then reduce the aluminum liquid temperature to 720°C, and refine under the condition of rotating the rotor and introducing argon gas at a speed of 360r / min for 20min. When the refining is carried out for 10min, add TiB2 nanocrystalline seed alloy with a particle size of 50-300nm, and simultaneously perform ultrasonic vibration treatment on the melt for 5min. Then, the alloy liquid is allowed to stand for 15min before slagging and cooling to the pouring temperature of 705°C for die casting.

[0055] Step (2) high pressure die casting: the mold temperature is maintained at 200°C, the slow injection speed is 0.31m / s, the fast injection speed is 3m / s, the holding pressure is 110MPa, and after the die casting is completed, it is taken out and air-cooled to prepare a high elongation die-cast Al-Mg alloy.

[0056] Example 2

[0057] This embodiment 2 discloses a method for preparing a high elongation die-cast Al-Mg alloy, including the following components in mass percentage: Mg: 6.12%, Mn: 0.52%, Fe: 0.13%, Si: 1.02%, B: 0.0090%, Ti: 0.19%, Zn: 0.11%, and the balance is Al. Specifically, the preparation method includes the following steps:

[0058] Step (1) smelting: melt the pure aluminum ingot at 780-800°C, then add Al-10Mn, Al-10Si, Al-10Ti, pure Zn and pure Mg in sequence, keep warm at 800°C for 1h to ensure uniform diffusion of the elements, then reduce the aluminum liquid temperature to 720°C, and refine under the condition of rotating the rotor and introducing argon gas at a speed of 360r / min for 20min. When the refining is carried out for 10min, add TiB2 nanocrystalline seed alloy with a particle size of 50-300nm, and simultaneously perform ultrasonic vibration treatment on the melt for 5min. Then, the alloy liquid is allowed to stand for 15min before slagging and cooling to the pouring temperature of 705°C for die casting.

[0059] Step (2) high pressure die casting: the mold temperature is maintained at 200°C, the slow injection speed is 0.31m / s, the fast injection speed is 3m / s, the holding pressure is 110MPa, and after the die casting is completed, it is taken out and air-cooled to prepare a high elongation die-cast Al-Mg alloy.

[0060] Example 3

[0061] This embodiment 3 discloses a method for preparing a high elongation die-cast Al-Mg alloy, comprising the following components in mass percentage: Mg: 6.13%, Mn: 0.53%, Fe: 0.13%, Si: 1.01%, B: 0.0063%, Ti: 0.11%, Zn: 0.13%, and the balance is Al. The preparation method comprises the following steps:

[0062] Step (1) smelting: melt the pure aluminum ingot at 780-800°C, then add Al-10Mn, Al-10Si, Al-10Ti, pure Zn and pure Mg in sequence, keep warm at 800°C for 1h to ensure uniform diffusion of the elements, then reduce the aluminum liquid temperature to 720°C, and refine under the condition of rotating the rotor and introducing argon gas at a speed of 360r / min for 20min. When the refining is carried out for 10min, add TiB2 nanocrystalline seed alloy with a particle size of 50-300nm, and simultaneously perform ultrasonic vibration treatment on the melt for 5min. Then, the alloy liquid is allowed to stand for 15min before slagging and cooling to the pouring temperature of 705°C for die casting.

[0063] Step (2) high pressure die casting: the mold temperature is maintained at 200°C, the slow injection speed is 0.31m / s, the fast injection speed is 2m / s, the holding pressure is 110MPa, and after the die casting is completed, it is taken out and air-cooled to prepare a high elongation die-cast Al-Mg alloy.

[0064] Combined with the comparative examples and embodiments, the microstructure characteristics and mechanical properties are as follows Figure 1 As shown in Table 2:

[0065] Figure 1 This is the optical microstructure diagram of the die-casting structure of Comparative Example 1; Figure 2 This is the optical microstructure diagram of the die-casting structure of Comparative Example 2; Figure 3 This is the optical microstructure diagram of the die-casting structure of Example 1; Figure 4 This is an optical microstructure diagram of the die casting structure of Example 2. Figure 1 It can be seen that when no nano-TiB2 seed alloy is added, the α-Al grain size is 15.3 μm, and the grain boundaries are Mg2Si and Al3Mg2 phases. Figure 2 It can be seen that when the nanocrystalline seed alloy is added, the B and Ti contents in the alloy are 0.0061% and 0.10% respectively, but the addition method is manual stirring after rotary degassing, and the die-casting alloy structure does not change significantly, and the grain size is 15.11. Figure 3 It can be seen that after adding nanocrystalline TiB2 alloy, when the contents of B and Ti in the alloy are 0.0063% and 0.11% respectively, the addition method is to add ultrasonic treatment during the rotary degassing process, and the die casting alloy structure is better. Figure 1 and 2 The grain size is obviously refined, and the grain size is 10.7μm. Figure 4 It can be seen that when the content of nanocrystalline TiB2 alloy is increased, the contents of B and Ti in the alloy are 0.0080% and 0.14%, respectively, and the average grain size of the alloy is 12.3 μm, which is Figure 1 and Figure 2 The grain size is somewhat refined compared to Figure 3The grain refining effect decreased, and large-sized Al3Mg2 phases appeared in the alloy. It can be seen that the addition of nanocrystalline seed alloy can significantly refine the target Al-Mg alloy grains, but its effect depends on the addition method and amount. The best effect can be achieved when rotary degassing is combined with ultrasonic vibration treatment. When the B and Ti contents in the alloy are within the preferred range, the refining effect is the best and the alloy structure is optimal.

[0066] Table 1 Mechanical properties of comparative examples and embodiments

[0067] Experimental groups Tensile strength / MPa Yield strength / MPa Elongation / % Comparative Example 1 306.2±12 167.2±6 15.6±3 Comparative Example 2 315.5±8 168.3±4 17.6±2 Example 1 328.6±5 173.9±1 26.7±3 Example 2 328.3±2 172.3±1 26.5±2 Example 3 320.2±3 170±1 20.5±3

[0068] Table 1 shows the mechanical properties of the comparative examples and embodiments. It can be seen that the mechanical properties of embodiments 1 and 2 are significantly better than those of comparative examples 1 and 2, especially the elongation. It can be seen that the addition of nano-TiB2 seed alloy can significantly improve the elongation of the die-casting alloy, but the effect depends on the addition method. When manually stirred after refining, there is no improvement effect. When ultrasonic vibration is used during the rotary degassing process, the alloy performance is significantly improved. This is because the change of the solidification behavior of TiB2 particles in the die-casting process depends on its heterogeneous nucleation effect, and the full dispersion of particles and the wettability with aluminum melt are the guarantee of the effect. Mechanical stirring and ultrasonic vibration treatment during the rotary degassing process are used to facilitate the uniform dispersion of particles and the wettability with Al liquid. In addition, the addition amount of particles needs to be controlled within the preferred range, that is, the B and Ti contents in the melt are 0.0040-0.0080% and 0.08-0.18% respectively. When the amount of particles added is too much, the formation of coarse Al3Mg2 phase in the alloy is promoted, and the alloy performance is no longer improved. The die-casting process parameters also have an important influence on the performance of the die-casting. The fast injection speed used in Example 3 is 2 m / s, which is the lower limit of the preferred injection speed range, and the elongation of the obtained die-casting alloy is lower than that of Examples 1 and 2. In summary, the preparation method for the target Al-Mg alloy composition described in this publication can be used to prepare Al-Mg alloy with high elongation at low cost.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high elongation die-casting Al-Mg alloy, characterized in that: Its composition is: Mg: 4.00-7.50wt.%, Mn: 0.10-0.70wt.%, Fe: 0.05-0.50wt.%, Si: 0.50-3.00wt.%, B: 0.0010-0.0090wt.%, Ti: 0.02-0.30wt.%, Zn: 0.05-0.30wt.%, and the balance is Al.

2. A method for preparing the high elongation die-cast Al-Mg alloy according to claim 1, characterized in that: The following steps are involved: Step (1) smelting: melting industrial pure aluminum, adding Al-Mn, Al-Si, Al-Ti, pure Zn and pure Mg in sequence after the aluminum ingot is completely melted, refining under the condition of passing inert gas, adding TiB2 nanocrystalline seed alloy during the refining process, and slagging and heat preservation after the refining is completed; Step (2) high pressure die casting: heating the mold and the blank, pouring aluminum liquid into the barrel, and after the die casting is completed, taking the casting out of the separated mold and air cooling it to prepare a high elongation die-casting Al-Mg alloy.

3. The method for preparing a high elongation die-cast Al-Mg alloy according to claim 2, characterized in that: The following steps are involved: The smelting in step (1) is as follows: the pure aluminum ingot is melted at 730-800°C, and then Al-Mn, Al-Si, Al-Ti, pure Zn, and pure Mg are added in sequence, and the mixture is kept at 750-780°C for 1-3 hours, and then the aluminum liquid temperature is reduced to 700-720°C, and the mixture is refined under the condition that the rotor rotates and an inert gas is introduced. The total refining time is 10-25 minutes. When the refining is carried out for 5-10 minutes, TiB2 nanocrystalline seed alloy is added.

4. The method for preparing a high elongation die-cast Al-Mg alloy according to claim 2 or 3, characterized in that: The content of Mn in the Al-Mn is 5-30wt.%; And / or, the content of Si in the Al-Si is 5-30wt.%; And / or, the content of Ti in the Al-Ti is 5-30wt.%.

5. The method for preparing a high elongation die-cast Al-Mg alloy according to claim 2 or 3, characterized in that: The insulation time is 10-30min; And / or, the inert gas is nitrogen and / or argon; And / or, the inert gas flow rate is 3-9 L / min.

6. The method for preparing a high elongation die-cast Al-Mg alloy according to claim 2 or 3, characterized in that: An auxiliary process is used during refining, wherein the auxiliary process is ultrasonic melt vibration, and the ultrasonic melt vibration time is 5-15 minutes.

7. The method for preparing high elongation die-cast Al-Mg alloy according to claim 2, characterized in that: The particle size of the TiB2 nanocrystalline seed alloy is 50nm-300nm.

8. The method for preparing high elongation die-cast Al-Mg alloy according to claim 2, characterized in that: The aluminum liquid pouring temperature in step (2) is 680-720°C; And / or, the mold is heated to maintain the mold temperature at 170-230°C.

9. The method for preparing high elongation die-cast Al-Mg alloy according to claim 2, characterized in that: The following steps are involved: In step (2), the slow injection speed is 0.1-0.6 m / s, the fast injection speed is 1 m / s-6 m / s, and the holding pressure is 100-120 MPa.

10. Use of the high elongation die-casting Al-Mg alloy according to claim 1 in the field of preparing aluminum alloy die-castings for automobiles.

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