High-elongation Al-Si-Mg series die-casting aluminum alloy, preparation method thereof and structural part

Abstract

The invention provides a high-elongation Al-Si-Mg series die-casting aluminum alloy, a preparation method of the high-elongation Al-Si-Mg series die-casting aluminum alloy and a structural part. The aluminum alloy comprises, by mass, 6%-8% of Si, 1.2%-1.8% of Mg, 0.001%-0.5% of Sn, 0.01%-0.3% of Fe, 0.001%-0.5% of Cr, 0.001%-0.15% of Ti, 0.001%-0.1% of B, 0%-0.2% of RE, 0%-0.05% of Sr, and the balance aluminum and inevitable impurities. The aluminum alloy is prepared from, by mass, 6%-8% of Si, 1.2%-1.8% of Mg, 0.001%-0.5% of Sn, 0.01%-0.3% of Fe, 0.001%-0.5% of Cr, 0.001%-0.15% of Ti, 0.001%-0.1% of B, 0%-0.2% of RE, 0%-0.05% of Sr and the balance Al. The aluminum alloy comprises the following components in percentage by mass: 0 to 0.5 percent of Li, 0.01 to 2.5 percent of Zn, 0 to 0.3 percent of Cd and 0 to 0.1 percent of Cu.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and particularly relates to a high elongation rate Al-Si-Mg series die-casting aluminum alloy, a preparation method thereof, and a structural member. Background Art

[0002] Die-casting aluminum alloys have good comprehensive properties, such as high strength, low density, good mechanical properties, and easy machining and cutting, and are widely used in the fields of aerospace and military industry, new energy vehicles, consumer electronic products, household and industrial electrical appliances, and high-rise buildings.

[0003] For aluminum-silicon series die-casting aluminum alloys, with the increase of the silicon element content, the fluidity and compactness of the aluminum alloy gradually increase, and the forming performance and mechanical properties gradually improve. However, the addition of silicon element does not greatly improve the strength of the die-casting aluminum alloy, and alloying elements that can improve the strength, such as Mg element, need to be added. However, the addition of Mg element will sharply reduce the elongation rate of the aluminum-silicon series die-casting aluminum alloy, resulting in the elongation rate of the existing aluminum-silicon series die-casting aluminum alloy being difficult to meet the requirements. Summary of the Invention

[0004] In view of the above-mentioned defects of the prior art, the present invention provides a high elongation rate Al-Si-Mg series die-casting aluminum alloy.

[0005] The present invention provides a high elongation rate Al-Si-Mg series die-casting aluminum alloy, which contains Al, and also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%.

[0006] Further, the high elongation rate Al-Si-Mg series die-casting aluminum alloy further contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.3%, Fe with a mass percentage content of 0.01-0.2%, Cr with a mass percentage content of 0.01-0.3%, Ti with a mass percentage content of 0.001-0.12%, B with a mass percentage content of 0.001-0.05%, RE with a mass percentage content of 0.001-0.1%, Sr with a mass percentage content of 0.001-0.05%, Li with a mass percentage content of 0.001-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0.001-0.2%, and Cu with a mass percentage content of 0.001-0.05%.

[0007] Further, the high elongation rate Al-Si-Mg series die-casting aluminum alloy further contains Co with a mass percentage content of 0.01-0.5% and Mn with a mass percentage content of 0.01-0.5%. Among them, the sum of the mass percentage contents of Fe, Cr, Co, and Mn is 0.04-1%.

[0008] Further, the mass ratio of the sum of the mass percentage contents of Sn, Fe, B, RE, and Cd to the mass percentage content of Mg is 0.007-0.9:1.

[0009] Further, the high elongation rate Al-Si-Mg series die-casting aluminum alloy further contains at least one of Ca, Be, V, Ge, Mo, Nb, Te, Ag, In, Zr, AlTiB, SiC, BN, and AlTiC. Among them, the mass percentage content of Ca is 0-0.2%, the mass percentage content of Be is 0-0.2%, the mass percentage content of V is 0-0.2%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.2%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Ag is 0-0.1%, the mass percentage content of In is 0-0.2%, the mass percentage content of Zr is 0-0.2%, the mass percentage content of AlTiB is 0-1%, the mass percentage content of SiC is 0-35%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-1%.

[0010] The present invention also provides a preparation method for a high elongation rate Al-Si-Mg series die-casting aluminum alloy, including the following steps: Provide Si source, Mg source, Sn source, Fe source, Cr source, Ti source, B source, RE source, Sr source, Li source, Zn source, Cd source, Cu source, and Al source; Heat-treat the Al source to obtain molten aluminum; Add Si source, Mg source, Sn source, Fe source, Cr source, Ti source, B source, RE source, Sr source, Li source, Zn source, Cd source, and Cu source to the molten aluminum to obtain a mixed liquid; and Perform die-casting treatment and aging treatment on the mixed liquid to obtain the high-elongation Al-Si-Mg series die-cast aluminum alloy, wherein the high-elongation Al-Si-Mg series die-cast aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%.

[0011] Further, the die-casting treatment is high-pressure casting. In the high-pressure casting, the temperature is 600-670 °C, the low-speed injection speed is 0.23-0.3 m / s, and the high-speed injection speed is 2-2.5 m / s; or The die-casting treatment is semi-solid die-casting treatment. In the semi-solid die-casting treatment, the temperature of the mixed liquid is 580-610 °C, the stirring speed is 550-700 r / min, the stirring duration is 4-10 min, the solid fraction is 35-50%, the injection speed is 0.4-1.5 m / s, the mold temperature is 220-240 °C, and the air pressure in the mold cavity is 30-50 kPa.

[0012] Further, the temperature of the aging treatment is 170-250 °C, and the time is 0.05-30 h; or The aging treatment includes a first-stage aging treatment, a second-stage aging treatment, a third-stage aging treatment, and a fourth-stage aging treatment. The temperature of the first-stage aging treatment is 80 - 120°C, and the time is 3 - 20 h; the temperature of the second-stage aging treatment is -200~-100°C, and the time is 0.5~10 h; the temperature of the third-stage aging treatment is 170 - 250°C, and the time is 0.05 - 5 h. After the second-stage aging treatment, the temperature is adjusted to 170 - 250°C within 1 - 5 min; the fourth-stage aging treatment is natural aging treatment or water-cooling aging treatment; or The aging treatment includes a first-stage low-temperature electric-field aging treatment and a second-stage high-temperature aging treatment. Among them, the temperature of the first-stage low-temperature electric-field aging treatment is 50 - 130°C, the time is 0.1 - 100 h, and the electric field strength is 2 - 50 kV / cm; the temperature of the second-stage high-temperature aging treatment is 170 - 250°C, and the time is 0.05 - 30 h.

[0013] Furthermore, the preparation method of the high elongation rate Al-Si-Mg series die-casting aluminum alloy further includes the step of adding at least one of Co source, Mn source, Ca source, Be source, V source, Ge source, Mo source, Nb source, Te source, Ag source, In source, Zr source, AlTiB source, SiC source, BN source, and AlTiC source to the aluminum liquid. Among them, the mass percentage content of Co is 0.01 - 0.5%, the mass percentage content of Mn is 0.01 - 0.5%, the mass percentage content of Ca is 0 - 0.2%, the mass percentage content of Be is 0 - 0.2%, the mass percentage content of V is 0 - 0.2%, the mass percentage content of Ge is 0 - 0.1%, the mass percentage content of Mo is 0 - 0.2%, the mass percentage content of Nb is 0 - 0.1%, the mass percentage content of Te is 0 - 0.1%, the mass percentage content of Ag is 0 - 0.1%, the mass percentage content of In is 0 - 0.2%, the mass percentage content of Zr is 0 - 0.2%, the mass percentage content of AlTiB is 0 - 1%, the mass percentage content of SiC is 0 - 35%, the mass percentage content of BN is 0 - 1%, and the mass percentage content of AlTiC is 0 - 1%.

[0014] The present invention also provides a structural member, the material of which is the high elongation rate Al-Si-Mg series die-casting aluminum alloy, or the high elongation rate Al-Si-Mg series die-casting aluminum alloy prepared by the preparation method of the high elongation rate Al-Si-Mg series die-casting aluminum alloy.

[0015] In the technical solution of the present invention, the high elongation Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%. The elements with the above contents interact with each other, making the high elongation Al-Si-Mg series die-casting aluminum alloy have better yield strength, tensile strength and elongation rate. Detailed implementation manners

[0016] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] An embodiment of the present invention provides a high elongation Al-Si-Mg series die-casting aluminum alloy. The high elongation Al-Si-Mg series die-casting aluminum alloy has better elongation rate and is suitable for being made into various thin-walled structural parts. The thickness of the thin-walled structural parts can be 1.5-15 mm, specifically 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, or 15 mm.

[0018] The high elongation rate Al-Si-Mg series die-casting aluminum alloy contains Al, and also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%.

[0019] The mass percentage content of Si can specifically be 6%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7%, 7.1%, 7.2%, 7.3%, 7.4%, 7.5%, 7.6%, 7.7%, 7.8%, 7.9%, or 8%.

[0020] The mass percentage content of Mg can specifically be 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, or 1.8%.

[0021] The mass percentage content of Fe can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0022] The specific mass percentage contents of Sn, Cr and Li can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.

[0023] The specific mass percentage content of Zn can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, or 2.5%.

[0024] The specific mass percentage content of Cd can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, or 0.3%.

[0025] The mass percentage content of Ti may specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, or 0.15%.

[0026] The mass percentage content of B may specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0027] The mass percentage content of RE may specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, and Gd.

[0028] The mass percentage content of Sr may specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%.

[0029] The mass percentage content of Cu may specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0030] In one embodiment, the high elongation rate Al-Si-Mg series die-casting aluminum alloy further contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.3%, Fe with a mass percentage content of 0.01-0.2%, Cr with a mass percentage content of 0.01-0.3%, Ti with a mass percentage content of 0.001-0.12%, B with a mass percentage content of 0.001-0.05%, RE with a mass percentage content of 0.001-0.1%, Sr with a mass percentage content of 0.001-0.05%, Li with a mass percentage content of 0.001-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0.001-0.2%, and Cu with a mass percentage content of 0.001-0.05%.

[0031] It can be understood that the Al-Si-Mg series die-casting aluminum alloy further contains impurities, wherein the mass percentage content of a single impurity is less than 0.02%, and the sum of the mass percentage contents of the impurities is less than 0.1%.

[0032] In the technical solution of the present invention, the Al-Si-Mg series high thermal conductivity aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%. Si, Mg, Sn, Fe, Cr, Ti, B, RE, Sr, Li, Zn, Cd, and Cu within the above content ranges interact with each other as a whole, ensuring that the Al-Si-Mg series has better elongation. Specifically as follows: (1) When the mass percentage content of Si is 6-8%, Si can improve the fluidity and density of the aluminum alloy, thereby improving the forming performance and mechanical properties of the aluminum alloy. When the mass percentage content of Si is 6-8%, the improvement of strength is not obvious; when the Si content exceeds 8%, coarse elemental Si will appear, sharply reducing the elongation rate of the aluminum alloy; (2) The mass percentage content of Mg is 1.2 - 1.8%. Mg can significantly improve the mechanical properties of aluminum alloys. Mg can react with other elements to form the second phase, avoiding adverse effects on the elongation rate of aluminum alloys. Mg can react with Al, Fe, Si, Cu, Zn, B, Ni, etc. to form second phases such as MgB, Mg2Sn, Mg2Si, Mg2Zn, Mg2SiZn, (CuMg)Al2, AlFeMgSi, AlFeMgSiNi, etc. However, Mg with a mass percentage content of 1.2 - 1.8% will sharply reduce the elongation rate of aluminum alloys. (3) The mass percentage content of Sn is 0.001 - 0.5%. Sn can react with Mg to form round spherical dispersed Mg2Sn strengthening phases, which can reduce the solid solubility of Mg and Sn in the aluminum matrix, avoiding the influence of Mg dissolved in the aluminum alloy on the elongation rate of the aluminum alloy. Sn can also react with other elements to form the second phase to avoid adverse effects on the elongation rate of the aluminum alloy caused by Sn dissolved in the aluminum matrix. Specifically, Sn can react with Al to form various high-temperature strengthening phases such as Al9Sn7, Al6Sn5, Al5Sn2, Al3Sn4, etc. (4) The mass percentage content of Fe is 0.01 - 0.3%. On the one hand, Fe can reduce the mold sticking tendency of aluminum alloy castings and improve the mechanical properties of aluminum alloys. On the other hand, Fe can react with other elements as much as possible to form the second phase to avoid adverse effects on the elongation rate of the aluminum alloy caused by Fe dissolved in the aluminum matrix. Specifically, Fe can react with Al, Si, Mg, Cu, Mn, Ni, etc. to form second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiCu, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, (CrFe)Al7, (CrMn)Al 12 , AlFeSiB, FeNiAl9, etc. (5) The mass percentage content of Cr is 0.001 - 0.5%. Cr can form (CrFe)Al7 and (CrMn)Al in aluminum 12Intermetallic compounds such as these have a certain strengthening effect on aluminum alloys; Cr can also improve the toughness of aluminum alloys and reduce the sensitivity to stress corrosion cracking; Cr can also improve the morphology of Fe, converting the β-Fe phase into the α-Fe phase, reducing the splitting effect of the β-Fe phase on the aluminum matrix when it cannot be dissolved, and thus increasing the elongation of the aluminum alloy; An appropriate amount of Cr forms various fine chromium-containing compounds in as-cast aluminum alloys, which can dissolve in the α phase during the die-casting stage and precipitate various Cr-containing phases during the aging stage. These Cr-containing phases can serve as the cores for the heterogeneous nucleation of the β" phase, thereby accelerating the formation of the β" phase. The precipitation of these Cr-containing phases in the aluminum matrix will inevitably have a certain delaying effect on the formation of metastable phases precipitating at the grain boundaries, increasing the elongation of the aluminum alloy; Cr can also significantly improve the microstructure and phase distribution of the original alloy, forming some Cr-rich multi-phase phases. The changes and distribution of these phases can improve the strength of the aluminum alloy; (6)The mass percentage content of Ti is 0.001-0.15%. Ti can improve the strength and elongation of aluminum alloys. Specifically, the TiAl3 phase formed by the reaction of Ti and Al can serve as a non-spontaneous core during crystallization, refining the grains, second phases, and precipitates, thereby improving the strength and elongation of aluminum alloys; (7)The mass percentage content of B is 0.001-0.1%. B can refine the grains, second phases, and precipitates, increasing the elongation of aluminum alloys; B can react with Al, Fe, Si, Mg, Cu, etc. to form second phases such as AlFeSiB, MgB, CuB, etc., which can not only reduce the solid solubility of the above elements in the matrix and reduce the adverse effects of these elements on elongation and thermal conductivity; In addition, B can refine the grains, modify and refine elemental Si to reduce the adverse effects of coarse elemental Si on the properties of aluminum alloys, and can also convert the β-AlFeSi phase into the Chinese character-shaped α-AlFeSi phase to eliminate the adverse effects of iron-rich phases on the properties of aluminum alloys, and can inhibit the segregation of Ti3Al. Therefore, the effect is better when Ti and B are used together; The boronization effect of B can also purify the aluminum alloy liquid, further improving the strength and elongation of the aluminum alloy; (8)The mass percentage content of RE is 0-0.2%. RE can form a rare earth active film on the surface of the Fe-containing phase or combine with atoms such as Al, Fe, Ti, etc. to form rare earth compounds to effectively reduce the solid solution of harmful elements in the aluminum matrix; RE can also convert the long strip-shaped β-Fe phase into a spherical ɑ-Fe phase and modify elemental Si to eliminate the adverse effects of Fe and Si; RE can also promote the precipitation of dispersed phases such as CuAl2, (CuMg)Al2, Mg2Si, etc., further improving the strength of aluminum alloys; RE can also refine the grains, second phases, and precipitates (e.g., it can refine Al3RE, Al3Fe, Mg2Si, etc.), further increasing the elongation of aluminum alloys; The mass percentage content of Sr is 0 - 0.05%. Sr can be used for modification treatment through the heterogeneous nucleation theory or the twin trough mechanism to refine the second phases such as eutectic silicon and improve the strength and elongation of the aluminum alloy. Sr can also transform the β-Fe phase in the ingot into the α-Fe phase to reduce the cutting effect on the aluminum matrix when the β-Fe phase cannot be dissolved, thereby improving the elongation of the aluminum alloy. Sr can preferentially combine with elements such as Fe, Cu, Mn, Cr, and Si to form dispersion strengthening to avoid the adverse effect of Sr dissolved in the aluminum matrix on the elongation of the aluminum alloy. Sr can also promote the precipitation of phases such as CuAl2 and Mg2Si to reduce the solid solubility of these alloying elements in the aluminum matrix to improve the elongation of the aluminum alloy. The mass percentage content of Cd is 0 - 0.3%. Cd can refine α-Al and can also form strengthening phases such as REAl2Cd3, Al3Cd, Al2Cd3, (CuCd)Al2, Mg2(SiCdREFe), and Mg3(BiCd)2 with Al, RE, Cu, Mg, Si, Fe, and Bi to reduce their solid solubility in the aluminum matrix and increase the volume fraction of the precipitated phases to improve the strength of the aluminum alloy. In addition, a large number of Cd-vacancy clusters are formed during the aging stage, promoting and accelerating the precipitation of phases such as CuAl2 and Mg2Si to reduce the solid solubility of the above elements in the aluminum matrix and further improve the strength of the aluminum alloy. The mass percentage content of Li is 0 - 0.5%. The solid solution strengthening of Li in the aluminum matrix can improve the strength of the aluminum alloy; and increase the fraction of the aging precipitated phase δ′ phase (Al3Li) to improve the precipitation strengthening effect. In addition, the addition of Li greatly reduces the maximum solubility of elements such as Mg, Cu, and Zr in the Al solid solution, reduces the stacking fault energy, and promotes the formation of {111}Al stacking defects. Nucleation is favorable at the {111}Al stacking defects; large-angle grain boundaries and small-angle grain boundaries are favorable for the formation of the plate-like T1 phase (Al2CuLi); vacancies or vacancy groups can provide nucleation sites, with dispersed particles as the nucleation core, forming phase pinning grain boundaries such as Mg2Si to improve the strength and elongation of the aluminum alloy. (12) The mass percentage content of Zn is 0.01 - 2.5%. Zn can be solid-solved in the aluminum matrix to significantly improve the strength of the aluminum alloy through solid-solution strengthening. After aging treatment, the precipitated elemental Zn can further improve the strength of the aluminum alloy; moreover, elemental Zn is a non-brittle phase between grain boundaries, which can improve the elongation of the aluminum alloy; Zn can increase the eutectic structure of the aluminum alloy and enhance the fluidity of the aluminum alloy, making the aluminum alloy suitable for die-casting; Zn can eliminate elemental Si to reduce the adverse effects of elemental Si on the properties of the aluminum alloy. Zn can also promote the precipitation of phases such as Mg2Si and Al2Cu, improving the mechanical properties; in addition, Zn can react with other elements to form a second phase to avoid the adverse effects of Zn solid-solved in the aluminum matrix on the elongation of the aluminum alloy. Specifically, Zn can react with Al, Mg, Cu, and Si, etc. to form second phases such as MgZn2, Mg2SiZn, and Al2CuZn. (13) The mass percentage content of Cu is 0 - 0.1%. The solid-solution strengthening of Cu in the aluminum matrix can improve the strength of the aluminum alloy; when the mass percentage content of Cu is not more than 0.1%, the elongation of the aluminum alloy can be significantly improved; trace amounts of Cu can also reduce the natural aging rate, thereby reducing the adverse effects of the parking effect on the alloy.

[0033] To avoid the adverse effect of Si on the elongation rate, the present invention sets the mass percentage content of Si to 6 - 8% (preferably 6 - 7.5%). However, the improvement in the strength of the aluminum alloy by Si with a mass percentage content of 6 - 8% is not significant. Correspondingly, the present invention sets the mass percentage content of Mg to 1.2 - 1.8% (preferably 1.4 - 1.6%), the mass percentage content of Zn to 0.01 - 2.5% (preferably 0.1 - 2%), and the mass percentage content of Li to 0 - 0.5% (0.1 - 0.5%). By means of Mg, Zn, and Li, the strength of the aluminum alloy is significantly increased. However, Mg with a mass percentage content of 1.2 - 1.8% will significantly reduce the elongation rate of the aluminum alloy, and Zn and Li can also reduce the harm to the elongation rate of the aluminum alloy caused by high - content Mg. To improve the elongation rate of the aluminum alloy, the present invention sets the mass percentage contents of Fe and Cu at relatively low levels, which are 0.01 - 0.3% (preferably 0.05 - 0.2%) and 0 - 0.1% (preferably 0.001 - 0.05%) respectively, to avoid the influence of high - content Fe on the elongation rate of the aluminum alloy. The present invention also adds Cr with a mass percentage content of 0.001 - 0.5% (preferably 0.01 - 0.2%), Ti with a mass percentage content of 0.001 - 0.15% (preferably 0.01 - 0.1%), Sr with a mass percentage content of 0 - 0.05% (preferably 0.01 - 0.05%), Cd with a mass percentage content of 0 - 0.3% (preferably 0.01 - 0.1%), B with a mass percentage content of 0.001 - 0.1% (preferably 0.01 - 0.1%), and RE with a mass percentage content of 0 - 0.2% (preferably 0.01 - 0.1%). These can refine the grains, secondary phases, and precipitation phases to improve the strength and elongation rate of the aluminum alloy. When the Fe content is not high, Cr with a mass percentage content of 0.001 - 0.5% can also improve the demolding performance of the aluminum alloy. The present invention also adds Sn with a mass percentage content of 0.001 - 0.5%. Sn can react with Mg to form round - shaped and dispersed Mg2Sn strengthening phases to improve the strength of the aluminum alloy. Sn, RE, Sr, and Cd can also promote the precipitation of Mg2Sn, Mg2Si, MgB, (CuMg)Al2, etc., further improving the elongation rate of the aluminum alloy. The above - mentioned elements can also react with each other to form secondary phases, avoiding dissolving in the aluminum matrix and affecting the elongation rate of the aluminum alloy. Thus, Si, Mg, Sn, Fe, Cr, Ti, B, RE, Sr, Li, Zn, Cd, and Cu within the above - mentioned content ranges interact and influence each other as a whole, enabling the aluminum alloy elements to have better strength, elongation rate, and demolding performance.Moreover, under the further action of subsequent refining treatment, aging treatment and die-casting treatment, the solid solubility of each element in the aluminum matrix is further reduced, and the impurity elements are also further reduced. The adverse effects of alloying elements and impurity elements on the elongation of the aluminum alloy can be eliminated as much as possible. The second phase (such as Al3Fe, Mg2Sn, Mg2Si, Al2Cu, AlFeSiNi, AlMnSi, etc.) can also be refined in the aluminum matrix and at or within the grain boundaries, greatly improving the strength and elongation of the aluminum alloy.

[0034] The high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Co with a mass percentage content of 0.01-0.5% and Mn with a mass percentage content of 0.01-0.5%. Among them, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04-1%, specifically 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0035] The mass percentage contents of Co and Mn can specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49% or 0.5%.

[0036] The sum of the mass percentage contents of Fe, Cr, Co and Mn can specifically be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%.

[0037] Co can refine the grain to improve the mechanical properties of aluminum alloy; Co can also react with other elements as much as possible to form the second phase to improve the mechanical properties of aluminum alloy. Specifically, Co can react with Al, Fe, Si, etc. to form the second phases such as Al 15 (Fe,Co)3Si2, Al3(Fe,Co), etc.; The refining effect of Co on the Al3Fe phase can transform the coarse needle-shaped and flaky β-Al3Fe phase into small flower-shaped and fine strip-shaped α-Al 15 (Fe,Co)3Si2 phase, and can also promote the precipitation of α-Al 15 (Fe,Co)3Si2 phase, further improving the mechanical properties of aluminum alloy.

[0038] Mn can react with Fe to form dispersed and fine α-Al(FeMn)Si phase to improve and regulate the β-Fe-rich phase; Mn can significantly refine the recrystallized grains and the second phase, effectively transforming the coarse needle-shaped or flaky β-AlFeSi phase into small granular α-Al(FeMn)Si dispersed particles to improve the Fe morphology, thereby improving the strength and elongation of aluminum alloy.

[0039] To avoid the influence of Fe on the elongation of aluminum alloy, the mass percentage content of Fe can be set relatively low. To ensure the demoulding performance of aluminum alloy, the sum of the mass percentage contents of Fe, Cr, Co and Mn can be 0.04 - 1%, preferably 0.3 - 0.6%. When the contents of Fe and / or Cr are relatively low, smooth demoulding can also be achieved. When the surface treatment is carried out on the mold and a boron carbide layer is formed on the parting surface of the mold, the mass percentage content of Fe can be 0.01 - 0.1% (preferably 0.01 - 0.06%), and the sum of the mass percentage contents of Fe and Mn can be 0.02 - 0.1%, specifically 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0040] When the surface treatment is carried out on the mold and a boron carbide layer is formed on the parting surface of the mold, if Co and Mn are further combined, the demoulding performance of aluminum alloy can be further improved. At this time, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04 - 0.5%, preferably 0.05 - 0.3%, and further preferably 0.05 - 0.1%. In this way, better demoulding performance can be achieved, and the influence of excessive element addition on the elongation can also be avoided.

[0041] The high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Sb with a mass percentage content of 0.01 - 0.5%, Ni with a mass percentage content of 0.01 - 0.5%, and Bi with a mass percentage content of 0.01 - 0.5%.

[0042] The mass percentage contents of Sb, Ni and Bi may specifically be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.21%, 0.22%, 0.23%, 0.24%, 0.25%, 0.26%, 0.27%, 0.28%, 0.29%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, 0.4%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, or 0.5%.

[0043] The sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi is 0.05 - 1.2%. The sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi may specifically be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, or 1.2%.

[0044] The mass ratio of the sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi to the mass percentage content of Mg is 0.1 - 1:1. The mass ratio of the sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi to the mass percentage content of Mg may specifically be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1.

[0045] Sn, Sb, Ni, Fe, and Bi can all react with Mg to form secondary phases. Mg preferentially reacts with Si to form the Mg2Si phase, and then reacts with Sn, Sb, Ni, Fe, and Bi to form secondary phases such as Mg2Sn, AlFeMgSiNi, Mg3Sb2, and Mg3Bi2, which can avoid the adverse effects of Mg dissolved in the aluminum matrix on the elongation of the aluminum alloy. When the sum of the mass percentage contents of Sn, Sb, Ni, Fe, and Bi is 0.05 - 1.2%, and the mass ratio of the sum of the mass percentage contents of Sn, Sb, Ni, Fe, and Bi to the mass percentage content of Mg is 0.1 - 1:1, it can ensure that all or nearly all of the Mg reacts with other alloying elements to form secondary phases, avoiding the presence of Mg dissolved in the aluminum matrix, and at the same time avoiding the addition of excessive elements that affect the elongation of the aluminum alloy. Specifically: Sb can be used as a modifier in aluminum alloys, effectively reducing the size of eutectic silicon lamellae, greatly reducing the possibility of Si splitting the matrix, and improving the mechanical properties of the alloy; Sb can react with other elements such as Mg to form the secondary phase Mg3Sb2, further improving the mechanical properties of the alloy; in addition, the addition of Sb can also increase the mutual precipitation of elements such as Cu, Zn, and Ni with a large solid solubility in the alloy matrix, further improving the mechanical properties of the alloy.

[0046] Sn can react with Mg to form round and spherical dispersed Mg2Sn strengthening phases, which can reduce the solid solubility of Mg and Sn in the aluminum matrix. Sn can also react with other elements to form secondary phases, thereby improving the mechanical properties of the aluminum alloy. Specifically, Sn can react with Al to form various high-temperature strengthening phases such as Al9Sn7, Al6Sn5, Al5Sn2, and Al3Sn4.

[0047] Bi expands during solidification, which is beneficial for feeding, and can form strengthening phases such as Mg3Bi2 and Mg3(BiCd)2 with Mg and Cd, etc., improving the mechanical properties of the alloy.

[0048] Ni can improve the mechanical properties of aluminum alloys. Ni can also react with other elements to form the second phase, so as to avoid the adverse effect of Ni dissolved in the aluminum matrix on the elongation rate of aluminum alloys. Specifically, Ni can react with Al, Fe, Mg, Si, etc. to form the second phases such as Al3Ni, AlFeSiNi, AlFeMgSiNi, FeNiAl9, etc., promoting the precipitation of elements such as Cu, Mg, Zn, Si, Fe, etc. dissolved in the alloy; Ni can also refine the grains, promote the precipitation of strengthening phases such as CuAl2, (CuMg)Al2, Mg2Si, etc., increase the volume fraction and dispersion degree of the precipitated phases, and reduce the solid solubility of alloying elements in the aluminum matrix; Cu with a mass percentage content of 0-0.1% can cooperate with Mg with a mass percentage content of 1.2-1.8% and Ni with a mass percentage content of 0.01-0.5% to play a composite strengthening role, reduce their solid solubility in the matrix, and improve the mechanical strength and elongation rate of aluminum alloys; in addition, the composite addition of Ni with a mass percentage content of 0.01-0.5% and Co with a mass percentage content of 0.01-0.5% can effectively modify Fe and convert free Fe into the second phase to improve the mechanical properties of aluminum alloys.

[0049] The high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Zr with a mass percentage content of 0-0.2%, Mo with a mass percentage content of 0-0.2%, and Be with a mass percentage content of 0-0.2%.

[0050] The mass percentage contents of Zr, Mo, and Be can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%.

[0051] The elements Mn, Cr, RE, Mo, Co, Be, and Sr cooperate with each other, which can not only reduce the maximum solid solubility of each other in the aluminum matrix to improve the elongation rate, but also promote the reaction between Mn and Fe. Mn can occupy the position of Fe element in the second phase, making the Fe-containing phase more dispersed and fine, and promoting the effect of modifying Fe. The elements Mn, Cr, RE, Mo, Co, Be, and Sr can also form a fine and dispersed ɑ-Al(MnFeX)Si phase (where X is at least one of Cr, RE, Mo, Co, Be, and Sr) to improve the elongation rate of aluminum alloys.

[0052] The combination of Cu with a mass percentage content of 0.001-0.04%, RE with a mass percentage content of 0.001-0.2%, and Zr with a mass percentage content of 0.001-0.2% can significantly improve the dispersion degree of Mg2Si, and at the same time prevent the formation of coarse phases such as AlSiFe, Mg3Sb2, MgZn2, Mg2Si, and Al3Zr, and reduce the solid solubility of various elements in the matrix, ensuring uniform precipitation during the solidification of the alloy; the addition of trace Cu can also reduce the anisotropy that appears after adding Mn to the alloy.

[0053] In addition, Mn can form independent manganese-rich hardening phases of Al6Mn and Al6FeMn in aluminum alloys. The manganese-rich phases are distributed at or near the grain boundaries to pin the grain boundaries. Although the coherence between the manganese-rich phases and the Al matrix is relatively low and their sizes are large, and the ability to pin dislocations is weak, the combined addition of Mn and Zr can not only reduce the usage amounts of various alloying elements, but also promote mutual precipitation to form more amounts of Al6(Mn,Zr) phases, Al 3( Zr,Mn) phases and Al6(FeMnZr) phases, and the strengthening effect is much greater than that when Mn or Zr is added alone.

[0054] The high elongation Al-Si-Mg series die-casting aluminum alloy also contains Ca with a mass percentage content of 0-0.2%. The mass percentage content of Ca can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. Ca can refine the eutectic structure, improve the β-Fe phase, improve the heat treatment performance of the alloy while increasing the strength of the alloy, and can also form strengthening phases of Al4Ca, Al2Ca3, AlCa2, and AlCaCu with Cu and Al, significantly improving the strength, heat resistance, and fatigue resistance of the aluminum alloy.

[0055] The high elongation Al-Si-Mg series die-casting aluminum alloy further contains V with a mass percentage content of 0 - 0.2%. The mass percentage content of V can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. V can refine grains, second phases and precipitation phases to reduce the grain boundary area and the corrosion sensitivity at grain boundaries, thereby improving the corrosion resistance and elongation of the aluminum alloy.

[0056] The high elongation Al-Si-Mg series die-casting aluminum alloy further contains In with a mass percentage content of 0 - 0.2%. The mass percentage content of In can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. In can improve the strength of the aluminum alloy; In can also refine grains, second phases and precipitation phases to improve the elongation of the aluminum alloy.

[0057] The high elongation Al-Si-Mg series die-casting aluminum alloy also contains Ge with a mass percentage content of 0-0.1%. The mass percentage content of Ge can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Ge can improve the mechanical properties of the aluminum alloy; Ge can react with other elements to form a second phase and improve the mechanical properties of the alloy. Specifically, Ge can react with Al, Si, etc. to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe. In addition, Ge can promote the precipitation of second phases such as Mg2Si and CuAl2, refine the precipitated phases, reduce the solid solubility of the above elements in the aluminum matrix, and Ge can also replace some Si atoms in the metastable precipitated phases. The Si-Ge phase precipitated in the initial stage of aging provides a nucleation site for the main precipitated phases β", θ", etc., increasing the density of phases such as β" and θ", and further improving the mechanical properties of the aluminum alloy.

[0058] The high elongation Al-Si-Mg series die-casting aluminum alloy also contains Nb with a mass percentage content of 0-0.1%. The mass percentage content of Nb can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Nb can improve the strength of the aluminum alloy; Nb can also refine grains, second phases, and precipitated phases to improve the elongation of the aluminum alloy. When the high elongation Al-Si-Mg series die-casting aluminum alloy contains both Nb and B, strengthening metal compounds such as AlNb3, AlNb, Al3Nb, and NbB2 can be formed, significantly improving the strength of the aluminum alloy.

[0059] The high elongation Al-Si-Mg series die-casting aluminum alloy further contains Te with a mass percentage content of 0 - 0.1%. The mass percentage content of Te can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Te can modify eutectic silicon, shortening the eutectic silicon along the length direction to improve the elongation of the aluminum alloy; when the aluminum alloy contains both Sb and Te, fine petal-shaped primary crystals can be formed, further improving the strength and elongation of the aluminum alloy.

[0060] The high elongation Al-Si-Mg series die-casting aluminum alloy further contains Ag with a mass percentage content of 0 - 0.1%. The mass percentage content of Ag can specifically be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Ag can refine the second phase to improve the elongation of the aluminum alloy. Ag can promote the precipitation of the second phase (such as Al2Cu, Mg2Si, Mg2Sb, Mg3Sn2, and Mg3Bi2, etc.), refine the precipitated phase and increase the density of the precipitated phase, enhancing the precipitation strengthening effect of the aluminum alloy, and can also refine the second phase to improve the elongation and strength of the aluminum alloy.

[0061] The high elongation Al-Si-Mg series die-casting aluminum alloy further contains AlTiB with a mass percentage content of 0 - 1%, SiC with a mass percentage content of 0 - 35%, BN with a mass percentage content of 0 - 1%, and AlTiC with a mass percentage content of 0 - 1%.

[0062] The mass percentage content of AlTiB, BN, and AlTiC can specifically be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, or 1%.

[0063] The mass percentage content of SiC can specifically be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, 33.5%, 34%, 34.5%, or 35%.

[0064] When AlTiB and SiC are used in combination, the mass percentage content of SiC can be reduced to 4 - 10%, thus reducing costs. In a preferred embodiment, the mass percentage content of AlTiB is 0.3 - 0.8% of AlTiB, and the mass percentage content of SiC is 5 - 8%. Specifically, when AlTiB and SiC are used in combination, a C-TiB2 particle complex is formed at the SiC-Al interface. The C atoms in SiC tend to enhance the adhesion energy of the C-TiB2 / Al interface, causing the originally long strip-shaped TiAl3 to break and shorten, so as to avoid the enrichment and growth of TiAl3, greatly enhancing the composite refinement effect. And through multiple experimental verifications: when AlTiB with a mass percentage content of 0.1 - 0.5% and SiC with a mass percentage content of 4 - 10% are combined with each other, the strength, elongation, wear resistance, corrosion resistance, and thermal stability of the aluminum alloy can be greatly improved.

[0065] AlTiB, SiC, AlTiC, and BN all have good refinement effects. When used in combination, the content of each can be reduced to achieve a good refinement effect. When SiC is used in combination with Ti and B, a C-TiB2 particle complex is formed at the SiC-Al interface. The C atoms in SiC tend to enhance the adhesion energy of the C-TiB2 / Al interface, causing the originally long strip-shaped TiAl3 to break and shorten, so as to avoid the enrichment and growth of TiAl3, greatly enhancing the composite refinement effect; BN is dispersed at the aluminum matrix interface and grain boundaries to form AlB2 and AlN nano-nucleation, which can refine the grains and promote the uniform nucleation of grains to improve the elongation of the aluminum alloy; under the action of SiC, Ti, B, and BN, AlTiC is not easy to aggregate and has a good effect of fine grain strengthening.

[0066] The present invention also provides a preparation method of a high elongation rate Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Providing Si source, Mg source, Sn source, Fe source, Cr source, Ti source, B source, RE source, Sr source, Li source, Zn source, Cd source, Cu source, and Al source; Performing a heat treatment on the Al source to obtain molten aluminum; Adjusting the temperature of the molten aluminum to 750 - 820 °C, and adding the Si source to the molten aluminum to obtain a first mixed solution; Adjusting the temperature of the first mixed solution to 720 - 740 °C, and adding the Si source, Mg source, Sn source, Fe source, Cr source, Ti source, B source, RE source, Sr source, Li source, Zn source, Cd source, and Cu source to the first mixed solution to obtain a second mixed solution; Performing a degassing treatment, a refining treatment, and a die-casting treatment on the second mixed solution to obtain an aluminum alloy part; and Performing an aging treatment on the aluminum alloy part to obtain the high elongation rate Al-Si-Mg series die-casting aluminum alloy, wherein the high elongation rate Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6 - 8%, Mg with a mass percentage content of 1.2 - 1.8%, Sn with a mass percentage content of 0.001 - 0.5%, Fe with a mass percentage content of 0.01 - 0.3%, Cr with a mass percentage content of 0.001 - 0.5%, Ti with a mass percentage content of 0.001 - 0.15%, B with a mass percentage content of 0.001 - 0.1%, RE with a mass percentage content of 0 - 0.2%, Sr with a mass percentage content of 0 - 0.05%, Li with a mass percentage content of 0 - 0.5%, Zn with a mass percentage content of 0.01 - 2.5%, Cd with a mass percentage content of 0 - 0.3%, and Cu with a mass percentage content of 0 - 0.1%.

[0067] The Si source, Mg source, Sn source, Fe source, Cr source, Ti source, B source, RE source, Sr source, Li source, Zn source, Cd source, and Cu source can be aluminum master alloys.

[0068] In one embodiment, the die-casting process may be high-pressure casting, with a temperature of 600-670 °C, a low-speed injection speed of 0.23-0.3 m / s, and a high-speed injection speed of 2-2.5 m / s. The temperature of the existing die-casting process for die-casting aluminum alloys is approximately 680 °C, which is relatively high. When the mixture is placed in the mold at this temperature, the erosion of the mold by the mixture is extremely large, resulting in a short service life of the mold. The Al-Si-Mg series die-casting aluminum alloy of the present invention has a lower melting point, enabling the temperature of the die-casting process of the present invention to be set lower, with less erosion of the mold, and improving the service life of the mold.

[0069] In another embodiment, the die-casting process may be a semi-solid die-casting process to produce a semi-solid die-casting aluminum alloy. In the semi-solid die-casting process, a device that can increase "flow + stirring" is used to improve the uniformity of the second mixture to obtain a semi-solid slurry. Combining with vacuum-assisted technology, the air pressure in the mold cavity is reduced to 30-50 kPa, and then the semi-solid slurry is injected into the mold for semi-solid die-casting forming. The temperature of the second mixture in the semi-solid die-casting process is 580-610 °C, the stirring speed is 550-700 r / min, the stirring duration is 4-10 min, the solid fraction is controlled at 35-50%, the injection speed is 0.4-1.5 m / s, and the mold temperature is 220-240 °C.

[0070] When the die-casting process is a semi-solid die-casting process, the refining process may be as follows: Mix potassium titanate whiskers and aluminum powder to obtain a mixture; under an argon protective atmosphere, use a low-energy ball mill to crush the mixture; when mechanically stirring or electromagnetically stirring the second mixture, add the mixture of potassium titanate whiskers and aluminum powder to the second mixture. The addition of aluminum powder can improve the wettability of the mixture and the aluminum melt and avoid agglomeration. During the crushing process, the ball-to-material ratio is 6:1, the ball milling time is 30-100 minutes, and the rotation speed is 150-300 rpm. The addition ratio of the mixture is 3-10% of the mass of the second mixture, specifically 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. Utilizing the crystal orientation relationship between potassium titanate whiskers and α-Al, by controlling the temperature and holding time of the second mixture, a titanium-rich transition layer is formed on the surface of potassium titanate whiskers, reducing the interfacial mismatch degree and enhancing the heterogeneous nucleation ability. Potassium titanate whiskers, as a heterogeneous nucleation substrate, preferentially induce the nucleation of α-Al grains during the solidification process of aluminum alloy, significantly increasing the nucleation rate, thereby refining the grains. Potassium titanate whiskers can also inhibit grain growth. The dispersed potassium titanate whiskers limit the abnormal growth of grains through physical hindrance, and at the same time reduce the dendrite spacing, improving the uniformity of the aluminum alloy structure. In this way, the strength, wear resistance, and machinability of the aluminum alloy can be improved, making it suitable for manufacturing precision components such as engine cylinder liners and bearings.

[0071] In the high-pressure casting or semi-solid die-casting process, the used die includes a moving die and a fixed die. Both the moving die and the fixed die are formed with parting surfaces, and the two parting surfaces together form a cavity for accommodating the mixed melt to form an aluminum alloy product with a certain shape. Before the die-casting process, both parting surfaces can be surface-treated. The surface treatment is to form a boron carbide layer on the parting surface. The boron carbide layer can not only improve the demolding performance, but also improve the wear resistance of the die, and can further resist the erosion of chemical substances such as acids, alkalis, and salts and the thermal erosion of aluminum alloy to extend the service life of the die. The thickness of the boron carbide layer can be 1-10 mm, specifically 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, or 10 mm. Through the surface treatment, the Fe content, the sum of the mass percentage contents of Fe and Cr, or the sum of the mass percentage contents of Fe, Cr, Co, and Mn can be set at a lower level.

[0072] The surface treatment can be: mixing a boron-containing gas (such as BCl3) with a carbon-containing gas (such as CH4) to obtain a mixed gas; introducing the mixed gas into the cavity, and through chemical vapor deposition, the boron-containing gas and the carbon-containing gas react chemically and deposit on the parting surface to generate a boron carbide layer. The temperature of the chemical vapor deposition method is 900-1200 °C, the deposition pressure is 200-500 Pa, and the carrier gas flow rate is 100-200 sccm. The boron carbide layer can make the hardness of the die steel reach 3000-4000 Hv; the boron carbide layer can reduce the affinity of the mixed melt to the die surface, improve the demolding performance of the aluminum alloy, and can smoothly demold even when the Fe, Cr, Co, or Mn content is low, greatly improving the elongation of the aluminum alloy; the boron carbide layer can resist the erosion of chemical substances such as acids, alkalis, and salts and improve the corrosion resistance of the aluminum alloy; the boron carbide layer can still maintain good physical and chemical properties in a high-temperature environment and improve the thermal stability of the aluminum alloy; the boron carbide layer has an extremely low friction coefficient, improves the surface smoothness of the aluminum alloy, and can significantly reduce the wear and energy consumption generated by mechanical friction of the aluminum alloy product; the boron carbide layer also has high heat transfer performance. At the moment when the aluminum alloy is formed, the boron carbide layer can quickly conduct away the heat, improve the heat transfer speed of the die, and the heat transfer speed is 2-4 times that of an ordinary die, so that the formed aluminum alloy can be cooled faster and the structure is more refined to improve the strength and elongation of the aluminum alloy.

[0073] The degassing treatment is: adjusting the temperature of the second mixed liquid to 700-740 °C, and introducing an inert gas such as argon into the second mixed liquid by a degassing machine. The temperature of the degassing treatment can be specifically 700 °C, 710 °C, 720 °C, 730 °C, or 740 °C. The time of the degassing treatment is 10-30 min, specifically 10 min, 15 min, 20 min, 25 min, or 30 min.

[0074] In another embodiment, the refining process is as follows: when introducing inert gas such as argon into the second mixed solution by a degassing machine, a grain refiner can be added together. The eddy current formed by the rotating disk of the degassing machine in the second mixed solution can evenly disperse the grain refiner and mix it into the second mixed solution. The grain refiner can refine the alloy structure to improve the strength and elongation of the aluminum alloy, and has the advantages of good dispersibility and low cost. The time of the refining process is 10 - 30 min, specifically it can be 10 min, 15 min, 20 min, 25 min, or 30 min, and the temperature of the refining process is 700 - 740 °C, specifically it can be 700 °C, 710 °C, 720 °C, 730 °C, or 740 °C. The grain refiner contains: 5 - 10 parts of potassium hexafluoroaluminate, 6 - 20 parts of AlTi5B1 metal powder, 8 - 25 parts of potassium titanate whisker powder, 20 - 40 parts of sodium chloride + potassium chloride, 5 - 10 parts of potassium nitrate, 5 - 10 parts of potassium carbonate, and 0.5 - 3 parts of potassium silicate. It can be understood that this refining process is applicable to semi-solid die casting and high-pressure casting.

[0075] In one embodiment, the temperature of the aging treatment is 170 - 250 °C and the time is 0.05 - 30 h. The temperature of the aging treatment can specifically be 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or 250 °C, and the time can specifically be 0.05 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, or 30 h.

[0076] In another embodiment, the aging treatment includes a first-stage aging treatment, a second-stage aging treatment, and a third-stage aging treatment. The temperature of the first-stage aging treatment is 80 - 120 °C, specifically it can be 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, or 120 °C, and the time is 3 - 20 h, specifically it can be 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, or 20 h; the temperature of the second-stage aging treatment is -200 to -100 °C, specifically it can be -200 °C, -190 °C, -180 °C, -170 °C, -160 °C, -150 °C, -140 °C, -130 °C, -120 °C, -110 °C, or -100 °C, and the time is 0.5 - 10 h, specifically it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h; the temperature of the third-stage aging treatment is 170 - 250 °C, specifically it can be 170 °C, 180 °C, 190 °C, 200 °C, 210 °C, 220 °C, 230 °C, 240 °C, or 250 °C, and the time is 0.05 - 5 h, specifically it can be 0.05 h, 0.1 h, 0.2 h, 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 2 h, 3 h, 4 h, or 5 h. The temperature of the first-stage aging treatment is relatively low. In the first-stage aging treatment, solute atoms in the die-cast aluminum alloy parts are stabilized, and a dense GP zone aluminum alloy part is formed while preventing the rapid precipitation of unsaturated Zn. Thus, the Zn content can be set relatively high.During the second-stage aging treatment, the volume shrinks rapidly, generating a considerable amount of stress, which in turn produces a large number of dislocations. These dislocations interact with the stress in the alloy, the grain boundaries, and entangle with each other to increase the yield strength, tensile strength, and elongation of the alloy. During this second-stage aging treatment, the crystal structure of the material changes, and recovery recrystallization occurs during the cryogenic recovery process, resulting in grain rotation and the formation of a recrystallization texture by preferred orientation, thereby increasing the tensile strength and yield strength of the aluminum alloy. A large number of supersaturated point defects (such as vacancies) and dislocations obtained by the aluminum alloy during this second-stage aging treatment can further promote the segregation of solute atoms such as Si, Mg, Sn, Fe, Cr, Ti, B, RE, Sr, Li, Zn, Cd, and Cu, significantly increasing the range of GP zones, which can increase the nucleation rate during the third-stage aging treatment and promote the more complete precipitation of alloying elements. After the second-stage aging treatment is completed, the temperature is adjusted to 170-250°C within 1-5 minutes to ensure that the supersaturated point defects (such as vacancies) and dislocations formed during the second-stage aging treatment can be completely or nearly completely retained until the third-stage aging treatment. At this time, the GP zones gradually transform into precipitation phases with smaller sizes but larger volume fractions, precipitating all or nearly all of the alloying elements dissolved in the alloy interior, increasing the pinning effect on dislocations, and greatly improving the strength and elongation of the aluminum alloy. The combined addition of Cr, Sn, Cd, Li, and RE enables the alloy to disperse and precipitate various Cr, Sn, Cd, Li, RE-containing dispersoids during the aging stage. These dispersoids themselves can refine the grains, increasing the alloy strength and elongation; they can also serve as the cores for the heterogeneous nucleation of the β" phase, thereby accelerating the formation of the β" phase and further increasing the strength and elongation. The aging treatment may further include a fourth-stage aging treatment, which can be natural aging treatment or water-cooled aging treatment. After the fourth-stage aging treatment, the elongation of the aluminum alloy is further increased, but the strength decreases somewhat. The natural aging treatment is to place the aluminum alloy parts after the third-stage aging treatment at room temperature for 0.5-5 h, specifically 0.5 h, 1 h, 2 h, 3 h, 4 h, or 5 h. The water-cooled aging treatment is to place the aluminum alloy parts after the third-stage aging treatment in normal-temperature water for 0.5-5 h, specifically 0.5 h, 1 h, 2 h, 3 h, 4 h, or 5 h. During the natural aging treatment process, the temperature of the aluminum alloy parts will drop rapidly, and fine strengthening phases continue to precipitate, but the precipitation rate will also decrease, further increasing the strength and elongation of the aluminum alloy. During the water-cooled aging treatment process, the temperature of the aluminum alloy parts will drop even more rapidly, and fine strengthening phases continue to precipitate, but the precipitation rate will decrease even faster, further increasing the strength and elongation of the aluminum alloy. The strength and elongation of the aluminum alloy after the water-cooled aging treatment are greater than those of the aluminum alloy after the natural aging treatment.

[0077] In another embodiment, the aging treatment includes a first-stage low-temperature electric-field aging treatment and a second-stage high-temperature aging treatment. The temperature of the first-stage low-temperature electric-field aging treatment is 50 - 130°C, the time is 0.1 - 100 h, and the electric-field intensity is 2 - 50 kV / cm. The temperature of the first-stage low-temperature electric-field aging treatment can specifically be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, or 130°C, the time can specifically be 0.1 h, 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 70 h, 75 h, 80 h, 85 h, 90 h, 95 h, or 100 h, and the electric-field intensity can specifically be 2 kV / cm, 5 kV / cm, 10 kV / cm, 15 kV / cm, 20 kV / cm, 25 kV / cm, 30 kV / cm, 35 kV / cm, 40 kV / cm, 45 kV / cm, or 50 kV / cm. The second-stage high-temperature aging treatment has no electric-field effect, its temperature is 170 - 250°C, and the time is 0.05 - 30 h. The temperature of the second-stage high-temperature aging treatment can specifically be 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, or 250°C, and the time can specifically be 0.05 h, 0.1 h, 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, or 30 h. During the first-stage low-temperature electric-field aging treatment, the low temperature of 50 - 130°C can inhibit the segregation of atoms such as Mg, Cu, Ni, Li, Zn, and Si, and at the same time make the alloy have a greater degree of supercooling, significantly increasing the range of GP zones, facilitating the increase in the nucleation rate during the subsequent high-temperature process, and enabling the alloying elements to precipitate more fully. Secondly, since applying an electric field at low temperature reduces the precipitation activation energy of the phases in the alloy, low-temperature electric-field aging can accelerate the precipitation nucleation rate of the precipitate phases during aging, and increase the volume fraction of nucleation sites. The hardness of the alloy increases significantly at the initial stage of electric-field aging. During the subsequent second-stage high-temperature aging treatment, the time required for the alloy to reach the peak hardness is shortened, the volume fraction of the precipitate phases is increased, and the size of the precipitate phases is refined. As the electric-field intensity increases during the first-stage low-temperature electric-field aging treatment, the number of nucleation sites of the strengthening phases precipitated in the alloy increases sharply, indicating that increasing the electric-field intensity can increase the nucleation and precipitation rate of the precipitate phases, and has no obvious effect on the growth of the second-stage high-temperature aging phases without an electric-field effect, and no coarsening of the size will occur, thereby increasing the elongation of the aluminum alloy.

[0078] In the technical solution of the present invention, the high elongation Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%. The elements with the above contents interact with each other and influence each other, so that the high elongation Al-Si-Mg series die-casting aluminum alloy has better yield strength, tensile strength and elongation rate at the same time.

[0079] In the technical solution of the present invention, in order to avoid the adverse effect of Si on the elongation rate, the mass percentage content of Si is set to 6-8% (preferably 6-7.5%). However, the improvement of the strength of the aluminum alloy by Si with a mass percentage content of 6-8% is not high. Correspondingly, the mass percentage content of Mg is set to 1.2-1.8% (preferably 1.4-1.6%), the mass percentage content of Zn is set to 0.01-2.5% (preferably 0.1-2%), and the mass percentage content of Li is set to 0-0.5% (0.1-0.5%). The strength of the aluminum alloy is greatly improved by Mg, Zn and Li. However, Mg with a mass percentage content of 1.2-1.8% will greatly reduce the elongation rate of the aluminum alloy. Zn and Li can also reduce the harm to the elongation rate of the aluminum alloy caused by high content of Mg. In order to improve the elongation rate of the aluminum alloy, the mass percentage contents of Fe and Cu are set relatively low, which are 0.01-0.3% (preferably 0.05-0.2%) and 0-0.1% (preferably 0.001-0.05%) respectively, to avoid the influence of high content of Fe on the elongation rate of the aluminum alloy. The present invention also adds Cr with a mass percentage content of 0.001-0.5% (preferably 0.01-0.2%), Ti with a mass percentage content of 0.001-0.15% (preferably 0.01-0.1%), Sr with a mass percentage content of 0-0.05% (preferably 0.01-0.05%), Cd with a mass percentage content of 0-0.3% (preferably 0.01-0.1%), B with a mass percentage content of 0.001-0.1% (preferably 0.01-0.1%), and RE with a mass percentage content of 0-0.2% (preferably 0.01-0.1%). It can refine grains, second phases and precipitation phases to improve the strength and elongation rate of the aluminum alloy. When the content of Fe is not high, Cr with a mass percentage content of 0.001-0.5% can also improve the demolding performance of the aluminum alloy. The present invention also adds Sn with a mass percentage content of 0.001-0.5%. Sn can react with Mg to form round spherical dispersed Mg2Sn strengthening phases, which can reduce the solid solubility of Mg and Sn in the aluminum matrix and avoid the influence of Mg dissolved in the aluminum alloy on the elongation rate of the aluminum alloy. Try to increase Sn so that the proportion of Sn reacting with other elements to form second phases is increased, further improving the strength of the aluminum alloy. Sn, RE, Sr, and Cd can also promote the precipitation of Mg2Sn, Mg2Si, MgB, (CuMg)Al2, etc., further improving the elongation rate of the aluminum alloy. The above elements can also react with each other to form second phases, avoiding dissolving in the aluminum matrix and affecting the elongation rate of the aluminum alloy. Thus, Si, Mg, Sn, Fe, Cr, Ti, B, RE, Sr, Li, Zn, Cd, and Cu within the above content ranges interact and influence each other as a whole, enabling the aluminum alloy elements to have better strength, elongation rate, and demolding performance.Moreover, under the further action of subsequent refining, aging and die-casting treatments, the solid solubility of each element in the aluminum matrix of Si, Mg, Sn, Fe, Cr, Ti, B, RE, Sr, Li, Zn, Cd, and Cu within the above-mentioned content range is further reduced, and the impurity elements are also further reduced, which can eliminate the adverse effects of alloy elements and impurity elements on the elongation of the aluminum alloy as much as possible, and the second phase (such as Al3Fe, Mg2Sn, Mg2Si, Al2Cu, AlFeSiNi, AlMnSi phases, etc.) can also be refined in the aluminum matrix and at the grain boundaries or within the grain boundaries, thereby greatly improving the strength and elongation of the aluminum alloy.

[0080] The method for preparing the high elongation Al-Si-Mg die-casting aluminum alloy also includes the step of adding at least one of a Co source, a Mn source, a Sb source, a Ni source, a Bi source, a Ca source, a Be source, a V source, a Ge source, a Mo source, a Nb source, a Te source, an Ag source, an In source, a Zr source, an AlTiB source, a SiC source, a BN source, and an AlTiC source to the first mixed solution. The above elements can at least be used to improve the strength or elongation of the aluminum alloy to obtain a high elongation Al-Si-Mg die-casting aluminum alloy with better performance. The raw material of the above alloying elements can be an aluminum master alloy. For example, the RE source can be an Al-RE alloy.

[0081] Example Please refer to Table 1 for the components and contents of the aluminum alloys of Examples 1 to 10, and please refer to Table 2 for the performance test results.

[0082] Table 1 Composition and content of aluminum alloys of Examples 1 to 10 To simplify the presentation, not all impurity elements and their contents are shown.

[0083] Table 2 Performance test results of aluminum alloys of Examples 1 to 10 The aluminum alloys of Examples 1 to 10 were made into structural parts, and the tensile strength, yield strength, and elongation of the structural parts were tested. The test results are shown in Table 2. In the production process of Examples 6 to 10, the mold was surface treated to form a 2 mm boron carbide layer on the parting surface of the mold.

[0084] Table 2 shows that the aluminum alloys of Examples 1 to 10 have good tensile strength, yield strength, and elongation. Specifically, the tensile strength of the aluminum alloys of Examples 1 to 10 is not less than 400 MPa, the yield strength is not less than 310 MPa, and the elongation is not less than 5%.

[0085] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A high elongation Al-Si-Mg series die-casting aluminum alloy contains Al, and is characterized in that, The high elongation Al-Si-Mg series die-casting aluminum alloy further contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%.

2. The high elongation rate Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high elongation Al-Si-Mg series die-casting aluminum alloy further contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.3%, Fe with a mass percentage content of 0.01-0.2%, Cr with a mass percentage content of 0.01-0.3%, Ti with a mass percentage content of 0.001-0.12%, B with a mass percentage content of 0.001-0.05%, RE with a mass percentage content of 0.001-0.1%, Sr with a mass percentage content of 0.001-0.05%, Li with a mass percentage content of 0.001-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0.001-0.2%, and Cu with a mass percentage content of 0.001-0.05%.

3. The high elongation rate Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high elongation Al-Si-Mg series die-casting aluminum alloy further contains Co with a mass percentage content of 0.01-0.5% and Mn with a mass percentage content of 0.01-0.5%. Among them, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04-1%.

4. The high elongation rate Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The mass ratio of the sum of the mass percentage contents of Sn, Fe, B, RE and Cd to the mass percentage content of Mg is 0.007-0.9:

1.

5. The high elongation rate Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high elongation Al-Si-Mg series die-casting aluminum alloy further contains at least one of Ca, Be, V, Ge, Mo, Nb, Te, Ag, In, Zr, AlTiB, SiC, BN, and AlTiC. Among them, the mass percentage content of Ca is 0-0.2%, the mass percentage content of Be is 0-0.2%, the mass percentage content of V is 0-0.2%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.2%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Ag is 0-0.1%, the mass percentage content of In is 0-0.2%, the mass percentage content of Zr is 0-0.2%, the mass percentage content of AlTiB is 0-1%, the mass percentage content of SiC is 0-35%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-1%.

6. A preparation method of a high elongation Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Providing a Si source, a Mg source, a Sn source, an Fe source, a Cr source, a Ti source, a B source, a RE source, a Sr source, a Li source, a Zn source, a Cd source, a Cu source, and an Al source; Performing a heat treatment on the Al source to obtain molten aluminum; Adding the Si source, the Mg source, the Sn source, the Fe source, the Cr source, the Ti source, the B source, the RE source, the Sr source, the Li source, the Zn source, the Cd source, and the Cu source to the molten aluminum to obtain a mixed solution; and Performing die-casting treatment and aging treatment on the mixed solution to obtain the high elongation Al-Si-Mg series die-casting aluminum alloy, wherein the high elongation Al-Si-Mg series die-casting aluminum alloy contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Sn with a mass percentage content of 0.001-0.5%, Fe with a mass percentage content of 0.01-0.3%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, B with a mass percentage content of 0.001-0.1%, RE with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.05%, Li with a mass percentage content of 0-0.5%, Zn with a mass percentage content of 0.01-2.5%, Cd with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%.

7. The preparation method of the high elongation rate Al-Si-Mg series die-casting aluminum alloy according to claim 6, characterized in that, The die-casting treatment is high-pressure casting. In the high-pressure casting, the temperature is 600-670 °C, the low-speed injection speed is 0.23-0.3 m / s, and the high-speed injection speed is 2-2.5 m / s; or The die-casting process is a semi-solid die-casting process. In the semi-solid die-casting process, the temperature of the mixed liquid is 580 - 610 °C, the stirring speed is 550 - 700 r / min, the stirring duration is 4 - 10 min, the solid fraction is 35 - 50%, the injection speed is 0.4 - 1.5 m / s, the mold temperature is 220 - 240 °C, and the air pressure in the mold cavity is 30 - 50 kPa.

8. The preparation method of the high elongation rate Al-Si-Mg series die-casting aluminum alloy according to claim 6, characterized in that, The temperature of the aging treatment is 170 - 250 °C, and the time is 0.05 - 30 h; or The aging treatment includes a first-stage aging treatment, a second-stage aging treatment, a third-stage aging treatment, and a fourth-stage aging treatment. The temperature of the first-stage aging treatment is 80 - 120 °C, and the time is 3 - 20 h; the temperature of the second-stage aging treatment is -200 to -100 °C, and the time is 0.5 - 10 h; the temperature of the third-stage aging treatment is 170 - 250 °C, and the time is 0.05 - 5 h. After the second-stage aging treatment, the temperature is adjusted to 170 - 250 °C within 1 - 5 min; the fourth-stage aging treatment is natural aging treatment or water-cooling aging treatment; or The aging treatment includes a first-stage low-temperature electric field aging treatment and a second-stage high-temperature aging treatment. Among them, the temperature of the first-stage low-temperature electric field aging treatment is 50 - 130 °C, the time is 0.1 - 100 h, and the electric field strength is 2 - 50 kV / cm; the temperature of the second-stage high-temperature aging treatment is 170 - 250 °C, and the time is 0.05 - 30 h.

9. The preparation method of the high elongation rate Al-Si-Mg series die-casting aluminum alloy according to claim 6, characterized in that, The preparation method of the high elongation rate Al-Si-Mg series die-casting aluminum alloy further includes the step of adding at least one of Co source, Mn source, Ca source, Be source, V source, Ge source, Mo source, Nb source, Te source, Ag source, In source, Zr source, AlTiB source, SiC source, BN source, and AlTiC source to the aluminum liquid. Among them, the mass percentage content of Co is 0.01 - 0.5%, the mass percentage content of Mn is 0.01 - 0.5%, the mass percentage content of Ca is 0 - 0.2%, the mass percentage content of Be is 0 - 0.2%, the mass percentage content of V is 0 - 0.2%, the mass percentage content of Ge is 0 - 0.1%, the mass percentage content of Mo is 0 - 0.2%, the mass percentage content of Nb is 0 - 0.1%, the mass percentage content of Te is 0 - 0.1%, the mass percentage content of Ag is 0 - 0.1%, the mass percentage content of In is 0 - 0.2%, the mass percentage content of Zr is 0 - 0.2%, the mass percentage content of AlTiB is 0 - 1%, the mass percentage content of SiC is 0 - 35%, the mass percentage content of BN is 0 - 1%, and the mass percentage content of AlTiC is 0 - 1%.

10. A structural member, characterized in that, The material of the structural member is the high elongation rate Al-Si-Mg series die-casting aluminum alloy according to any one of claims 1 - 5, or the high elongation rate Al-Si-Mg series die-casting aluminum alloy prepared by the preparation method of the high elongation rate Al-Si-Mg series die-casting aluminum alloy according to any one of claims 6 - 9.

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