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

Abstract

The invention provides a high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, a preparation method thereof and a structural part. The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy contains Al, the high-strength aluminum alloy material further comprises the following components in percentage by mass: 6 to 8 percent of Si, 1.2 to 1.8 percent of Mg, 0.001 to 2.5 percent of Zn, 0.01 to 0.4 percent of Fe, 0.001 to 0.5 percent of Cr, 0.001 to 0.15 percent of Ti, 0 to 0.05 percent of Sr, 0 to 0.3 percent of Mn, 0 to 0.3 percent of Zr and the balance of Al. The mass percent content of Li is 0-0.5%, and the mass percent content of Cu is 0-0.1%.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and particularly relates to a high-strength and high-elongation 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, easy machining and cutting, etc., and are widely used in fields such as aerospace and military industry, new energy vehicles, consumer electronic products, household and industrial electrical appliances, and high-rise buildings. For aluminum-silicon series die-casting aluminum alloys, 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 of the aluminum-silicon series die-casting aluminum alloy. Therefore, there is an urgent need to provide an aluminum-silicon series die-casting aluminum alloy with better tensile strength, yield strength and elongation. Summary of the Invention

[0003] Aiming at the above-mentioned defects of the prior art, the present invention provides a high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, which has better tensile strength, yield strength and elongation.

[0004] The present invention provides a high-strength and high-elongation 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5%, and Cu with a mass percentage content of 0-0.1%.

[0005] Furthermore, the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Si with a mass percentage content of -8%, Mg with a mass percentage content of 1.2 - 1.8%, Zn with a mass percentage content of 0.001 - 2%, Fe with a mass percentage content of 0.01 - 0.4%, Cr with a mass percentage content of 0.001 - 0.5%, Ti with a mass percentage content of 0.001 - 0.15%, Sr with a mass percentage content of 0.001 - 0.05%, Mn with a mass percentage content of 0.001 - 0.3%, Zr with a mass percentage content of 0.001 - 0.3%, Li with a mass percentage content of 0.001 - 0.5%, and Cu with a mass percentage content of 0.001 - 0.1%.

[0006] Furthermore, the mass ratio of Mg to Zn is 0.1 - 10:1.

[0007] Furthermore, the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains at least one of Sb, Sn, Co, Bi, Ca, Be, V, Ge, Mo, Nb, Te, Ag, In, AlTiB, SiC, BN, and AlTiC. Among them, the mass percentage content of Sb is 0 - 0.3%, the mass percentage content of Sn is 0 - 0.3%, the mass percentage content of Co is 0 - 0.3%, the mass percentage content of Bi is 0 - 0.3%, 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 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%.

[0008] The present invention also provides a preparation method for a high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Providing a Si source, a Mg source, a Zn source, an Fe source, a Cr source, a Ti source, a Sr source, a Mn source, a Li source, a Zr 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 Zn source, the Fe source, the Cr source, the Ti source, the Sr source, the Mn source, the Li source, the Zr source, and the Cu source to the molten aluminum to obtain a mixed solution; and The mixed solution is subjected to die-casting treatment and aging treatment to obtain the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy. Among them, the high-strength and 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5% and Cu with a mass percentage content of 0-0.1%.

[0009] Furthermore, the preparation method of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy further includes a step of surface treatment of the mold, and the surface treatment is to form a boron carbide layer on the parting surface of the mold.

[0010] Furthermore, 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 solution 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.

[0011] Furthermore, the temperature of the aging treatment is 170-250 °C, and the time is 0.05-30 h; or The aging treatment includes the first-stage aging treatment, the second-stage aging treatment, the third-stage aging treatment and the 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-cooled 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.

[0012] Furthermore, the method for preparing the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy further includes the step of adding at least one of an Sb source, an Sn source, a Co 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, an AlTiB source, a SiC source, a BN source, and an AlTiC source to the aluminum liquid. Among them, the mass percentage content of Sb is 0-0.3%, the mass percentage content of Sn is 0-0.3%, the mass percentage content of Co is 0-0.3%, the mass percentage content of Bi is 0-0.3%, 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 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%.

[0013] The present invention also provides a structural member, the material of which is the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, or the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy prepared by the method for preparing the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy.

[0014] In the technical solution of the present invention, the high-strength and 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr 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 affect each other, so that the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy has better yield strength, tensile strength and elongation rate. Detailed implementation manners

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described 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.

[0016] An embodiment of the present invention provides a high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy. The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy has better tensile strength, yield strength and elongation rate, and is suitable for being made into various structural parts. The thickness of the structural part 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.

[0017] The high-strength and high-elongation 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5%, and Cu with a mass percentage content of 0-0.1%.

[0018] 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%.

[0019] The mass percentage content of Mg can specifically be 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, or 1.8%.

[0020] The mass percentage content of Zn 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%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.45%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.78%, 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%. The mass percentage content of Mg and the mass percentage content of Zn can be in direct proportion. When the Mg content is high, the Zn content can also be set higher to generate more second phases with a dispersed distribution of MgZn2, thereby significantly improving the strength of the aluminum alloy. The mass ratio of Mg to Zn is 0.1 - 10:1, and can specifically be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1.

[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%, 0.3%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38%, 0.39%, or 0.4%.

[0022] The mass percentage content of Cr and Li 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%, 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 mass percentage content of Ti 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%, or 0.15%.

[0024] The mass percentage content of Mn and Zr 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%, 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 Sr 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%, or 0.05%.

[0026] 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%.

[0027] In one embodiment, the high-strength and 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%, Zn with a mass percentage content of 0.001-2%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0.001-0.05%, Mn with a mass percentage content of 0.001-0.3%, Zr with a mass percentage content of 0.001-0.3%, and Cu with a mass percentage content of 0.001-0.1%.

[0028] It can be understood that the Al-Si-Mg series die-casting aluminum alloy further contains impurities, where 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%.

[0029] 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, and Cu with a mass percentage content of 0-0.1%. Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, 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 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 alloy; Mg can react with other elements to form the second phase, avoiding adverse effects on the elongation rate of aluminum alloy. 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 alloy; (3) The mass percentage content of Zn is 0.01 - 2.5%. Zn can dissolve in the aluminum matrix and significantly improve the strength of aluminum alloy through solid solution strengthening. After aging treatment, the precipitated elemental Zn can further improve the strength of aluminum alloy; moreover, elemental Zn is a non-brittle phase between grain boundaries, which can improve the elongation rate of aluminum alloy; Zn can increase the eutectic structure of aluminum alloy and enhance the fluidity of 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 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 the second phase to avoid adverse effects of Zn dissolved in the aluminum matrix on the elongation rate of aluminum alloy. Specifically, Zn can react with Al, Mg, Cu, and Si, etc. to form second phases such as MgZn2, Mg2SiZn, Al2CuZn, etc.; (4) The mass percentage content of Fe is 0.01 - 0.4%. On the one hand, Fe can reduce the tendency of aluminum alloy castings to stick to the mold and improve the mechanical properties of aluminum alloy. On the other hand, Fe can react with other elements to form the second phase as much as possible to avoid adverse effects of Fe dissolved in the aluminum matrix on the elongation rate of aluminum alloy. 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 and second phases such as 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, convert the β-Fe phase into the α-Fe phase, and reduce the splitting effect of the β-Fe phase on the aluminum matrix when it cannot be dissolved, so as to improve the elongation of the aluminum alloy; An appropriate amount of Cr forms a variety of fine chromium-containing compounds in the as-cast aluminum alloy, which can dissolve in the α phase during the die-casting stage and can precipitate a variety of 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 precipitated at the grain boundaries, so as to improve the elongation of the aluminum alloy; Cr can also significantly improve the microstructure morphology and phase distribution of the original alloy, forming some Cr-rich multi-phases. The changes and distribution changes 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, refine the grains, second phases and precipitation phases, so as to improve the strength and elongation of aluminum alloys; (7)The mass percentage content of Sr is 0-0.05%. Sr can be modified by the heterogeneous nucleation theory or the twin valley mechanism to refine second phases such as eutectic silicon and improve the strength and elongation of aluminum alloys; Sr can also convert the β-Fe phase in the ingot into the α-Fe phase to reduce the splitting effect of the β-Fe phase on the aluminum matrix when it cannot be dissolved, so as to improve 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; (8)The mass percentage content of Mn is 0-0.3%, and the mass percentage content of Mn is 0.001-0.3%. Mn reacts with Fe to form fine and dispersed α-Al(FeMn)Si phases, which can improve and regulate the β-Fe-rich phase; Mn can significantly refine the recrystallized grains and second phases, effectively convert the coarse needle-shaped or plate-shaped β-AlFeSi phase into small granular α-Al(FeMn)Si dispersed particles to improve the Fe morphology, so as to improve the strength and elongation of aluminum alloys; The mass percentage content of Zr is 0 - 0.3%. Zr can improve the strength of aluminum alloy; Zr can also form Al3Zr phase in aluminum alloy. The Al3Zr phase can refine grains, secondary phases and precipitation phases to improve the elongation of aluminum alloy; Mn can form independent Mn-rich hardening phases of Al6Mn and Al6FeMn in aluminum alloy. The Mn-rich phases are distributed at or near grain boundaries to pin grain boundaries. Although the coherence between the Mn-rich phase and the Al matrix is low and its size is large, and the ability to pin dislocations is weak, the combined addition of Mn and Zr can not only reduce the usage amount of each alloying element, but also promote mutual precipitation to form more amounts of Al6(Mn,Zr) phase, Al 3( Zr,Mn) phase and Al6(FeMnZr) phase, and the strengthening effect is far greater than that when Mn or Zr is added alone; (10)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 aluminum alloy; and increase the fraction of the aging precipitation 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, Zr, etc. 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 plate-like T1 phase (Al2CuLi); vacancies or vacancy clusters can provide nucleation sites, with dispersed particles as nucleation cores, to form phases such as Mg2Si to pin grain boundaries and improve the strength and elongation of aluminum alloy; (11)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 aluminum alloy; when the mass percentage content of Cu is not more than 0.1%, the elongation of aluminum alloy can be significantly improved; trace Cu can also reduce the natural aging rate, thereby reducing the adverse effects of the parking effect on the alloy.

[0030] 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 increase 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 0.5-2%), and the mass percentage content of Li to 0-0.5% (preferably 0.1-0.5%). The strength of the aluminum alloy is significantly increased by Mg, Zn, and Li. However, Mg with a mass percentage content of 1.2-1.8% will significantly reduce the elongation rate of the aluminum alloy. Zn and Li can reduce the reduction of 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 to relatively low values, which are 0.01-0.4% (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%) and Mn with a mass percentage content of 0-0.3% (preferably 0.01-0.2%) to compensate for the influence on the demolding performance when the Fe content is not high, so as to ensure the demolding performance of the aluminum alloy. The combination of Cr, Mn, and Li can also improve the strength and elongation rate of the aluminum alloy at the same time. The present invention also adds Zr with a mass percentage content of 0-0.3% (preferably 0.01-0.2%). The combined addition of Mn and Zr can not only reduce the usage amount of each alloy element, but also promote mutual precipitation, further enhancing the strengthening effect. The present invention also adds Ti with a mass percentage content of 0.001-0.15% (preferably 0.01-0.1%) and Sr with a mass percentage content of 0-0.05% (preferably 0.01-0.05%), which can refine the grains, the second phase, and the precipitated phase to improve the strength and elongation rate of the aluminum alloy. Sr and Zr can also promote the precipitation of 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 a second phase, avoiding dissolving in the aluminum matrix and affecting the elongation rate of the aluminum alloy. In this way, Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, and Cu within the above content ranges interact with 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 rate of the aluminum alloy can be eliminated as much as possible. The second phase (such as Al3Fe, Mg2Si, Al2Cu, MgZn2, AlMnSi, etc.) can also be refined within the aluminum matrix and at the grain boundaries or within the grain boundaries, greatly improving the strength and elongation rate of the aluminum alloy.

[0031] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Sb with a mass percentage content of 0.01 - 0.3%, Sn with a mass percentage content of 0.01 - 0.3%, Ni with a mass percentage content of 0.01 - 0.5%, and Bi with a mass percentage content of 0.01 - 0.3%.

[0032] The specific mass percentage content of Sb, Sn, and Bi can 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%.

[0033] The specific mass percentage content of Ni can 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%.

[0034] The sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi is 0.05 - 1%. Specifically, the sum of the mass percentage contents of Sn, Sb, Fe and Bi can 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%, or 1%.

[0035] 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 0.05 - 1:1. Specifically, the mass ratio of the sum of the mass percentage contents of Sn, Sb, Fe and Bi to the mass percentage content of Mg can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 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.

[0036] Sn, Sb, Fe and Bi can all react with Mg to form a second phase. Mg preferentially reacts with Si to form the Mg2Si phase, and then reacts with Sn, Sb, Fe and Bi to form second phases such as Mg2Sn, AlFeMgSiNi, Mg3Sb2, Mg3Bi2, etc., which can avoid the adverse effect of Mg dissolved in the aluminum matrix on the elongation rate of the aluminum alloy. When the sum of the mass percentage contents of Sn, Sb, Ni, Fe and Bi is 0.05 - 1%, 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 0.05 - 1:1, it can ensure that all or nearly all of Mg reacts with other alloying elements to form a second phase, avoiding the existence of Mg dissolved in the aluminum matrix, and at the same time avoiding the influence of adding too many elements on the elongation rate of the aluminum alloy. Specifically: Fe can react with other elements as much as possible to form a second phase to avoid the adverse effect of Fe dissolved in the aluminum matrix on the elongation rate of the aluminum alloy. 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.

[0037] 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 second phase Mg3Sb2 to improve 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.

[0038] 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 the second phase, thereby improving the mechanical properties of aluminum alloys. Specifically, Sn can react with Al to form various high-temperature strengthening phases such as Al9Sn7, Al6Sn5, Al5Sn2, and Al3Sn4.

[0039] Bi expands during solidification, which is beneficial for feeding. It can form strengthening phases such as Mg3Bi2 and Mg3(BiCd)2 with Mg and Cd, etc., to improve the mechanical properties of the alloy.

[0040] Ni can improve the mechanical properties of aluminum alloys. Ni can also react with other elements to form the second phase to avoid the adverse effect of Ni dissolved in the aluminum matrix on the elongation of aluminum alloys. Specifically, Ni can react with Al, Fe, Mg, Si, etc. to form second phases such as Al3Ni, AlFeSiNi, AlFeMgSiNi, and FeNiAl9, promoting the precipitation of elements such as Cu, Mg, Zn, Si, and Fe dissolved in the alloy; Ni can also refine grains, promote the precipitation of strengthening phases such as CuAl2, (CuMg)Al2, and Mg2Si, 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 of aluminum alloys.

[0041] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains RE with a mass percentage content of 0-0.2%, Mo with a mass percentage content of 0-0.2%, Co with a mass percentage content of 0-0.3%, and Be with a mass percentage content of 0-0.2%. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, and Gd.

[0042] The mass percentage contents of RE, Mo and Be 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%.

[0043] Co can react with other elements to form a second phase to improve the mechanical properties of the aluminum alloy. Specifically, Co can react with Al, Fe, Si, etc. to form second phases such as Al 15 (Fe,Co)3Si2, Al3(Fe,Co), etc.; Co can refine the grains and can also refine the Al3Fe phase, transforming the coarse needle-like and flaky β-Al3Fe phase into small flower-like and fine strip-like α-Al 15 (Fe,Co)3Si2 phase, and Co can also promote the precipitation of α-Al 15 (Fe,Co)3Si2 phase, further improving the strength and elongation of the aluminum alloy.

[0044] In order to avoid the influence of Fe on the elongation of the aluminum alloy, the mass percentage content of Fe can be set relatively low. In order to ensure the demolding performance of the aluminum alloy, the sum of the mass percentage contents of Fe, Cr, Co and Mn is 0.04 - 1%, specifically it can be 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%. When the mold is surface-treated to form a boron carbide layer 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 it can be 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%; the sum of the mass percentage contents of Fe, Cr, and Mn can be 0.04 - 0.1%, specifically it can be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%; 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 demolding performance can be achieved, and the influence of excessive element addition on the elongation can be avoided.

[0045] The combined action of Mn, Cr, RE, Mo, Co, Be, and Sr elements can not only reduce their maximum solid solubility 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 in the second phase, making the Fe-containing phase more dispersed and finer, and enhancing the effect of modifying Fe. Between Mn, Cr, RE, Mo, Co, Be, and Sr elements, a fine and dispersed ɑ-Al(MnFeX)Si phase (where X is at least one of Cr, RE, Mo, Co, Be, and Sr) can also be formed to improve the elongation rate of the aluminum alloy.

[0046] The combined 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 the aluminum alloy. 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 - 0.3% can significantly improve the dispersion degree of Mg2Si, and at the same time prevent the formation of coarse phases such as AlSiFe, Mg3Sb2, 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.

[0047] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Ca with a mass percentage content of 0 - 0.2%. The specific mass percentage content of Ca 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%, 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 such as Al4Ca, Al2Ca3, AlCa2, and AlCaCu with Cu and Al, significantly improving the strength, heat resistance, and fatigue resistance of the aluminum alloy.

[0048] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also 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, secondary phases, and precipitation phases to reduce the grain boundary area and lower the corrosion sensitivity at grain boundaries, thereby improving the corrosion resistance and elongation of the aluminum alloy.

[0049] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also 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 increase the strength of the aluminum alloy; In can also refine grains, secondary phases, and precipitation phases to improve the elongation of the aluminum alloy.

[0050] The high-strength and 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, Ge can also replace some Si atoms in the metastable precipitated phases, and the Si-Ge phase precipitated in the initial stage of aging provides nucleation sites for the main precipitated phases β", θ", etc., increasing the density of phases such as β" and θ", to further improve the mechanical properties of the aluminum alloy.

[0051] The high-strength and 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-strength and 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, which can significantly improve the strength of the aluminum alloy.

[0052] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also 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 to further improve the strength and elongation of the aluminum alloy.

[0053] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also 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.

[0054] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains Cd with a mass percentage content of 0 - 0.2%. 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%, or 0.2%. Cd can improve the strength of the aluminum alloy; Cd can also refine grains, secondary phases and precipitation phases to improve the elongation of the aluminum alloy. Cd can refine α-Al, and can also form strengthening phases such as REAl2Cd3, Al3Cd, Al2Cd3, (CuCd)Al2, Mg2(SiCdREFe), Mg3(BiCd)2 with Al, RE, Cu, Mg, Si, Fe, Bi, etc., to reduce their solid solubility in the aluminum matrix and increase the volume fraction of the precipitation phase, thereby improving the strength of the aluminum alloy. In addition, a large number of Cd-vacancy clusters will be formed during the aging stage of Cd, promoting and accelerating the precipitation of phases such as CuAl2 and Mg2Si, reducing the solid solubility of the above elements in the aluminum matrix, and further improving the strength of the aluminum alloy.

[0055] The high-strength Al-Si-Mg series die-casting aluminum alloy also contains B with a mass percentage content of 0 - 0.1%. The specific mass percentage content of B 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%, or 0.1%. B can refine grains, secondary phases and precipitation phases to improve the elongation of the aluminum alloy; B can react with Al, Fe, Si, Mg, Cu, etc. to generate secondary 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 the above elements on the elongation and thermal conductivity; in addition, B can also refine grains, modify and refine elemental Si to reduce the adverse effects of coarse elemental Si on the properties of the aluminum alloy, and can also transform the β-AlFeSi phase into the Chinese character-shaped α-AlFeSi phase to eliminate the adverse effects of the iron-rich phase on the properties of the aluminum alloy, and can inhibit the segregation of TiAl3. 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.

[0056] The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also 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%.

[0057] The mass percentage contents 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%.

[0058] 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%.

[0059] When AlTiB and SiC are used in combination, the mass percentage content of SiC can be reduced to 4-10%, thereby 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.

[0060] AlTiB, SiC, AlTiC, and BN all have good refinement effects. When used in combination, the respective contents can be reduced to achieve good refinement effects. When SiC is used in combination with Ti and B, C-TiB2 particle complexes are 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, avoiding the enrichment and growth of TiAl3, and greatly enhancing the combined refinement effect. BN dispersedly distributes AlB2 and AlN nano-nucleation at the aluminum matrix interface and grain boundaries, which can refine grains and promote uniform grain nucleation to improve the elongation of aluminum alloys. Under the action of SiC, Ti, B, and BN, AlTiC is not prone to aggregation and has a good effect of fine grain strengthening.

[0061] The present invention also provides a method for preparing a high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Providing Si source, Mg source, Zn source, Fe source, Cr source, Ti source, Sr source, Mn source, Li source, Zr 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, Zn source, Fe source, Cr source, Ti source, Sr source, Mn source, Li source, Zr source, and Cu source to the first mixed solution to obtain a second mixed solution; Performing degassing treatment, refining treatment, and die-casting treatment on the second mixed solution to obtain an aluminum alloy part; and Performing aging treatment on the aluminum alloy part to obtain the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, wherein the high-strength and 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%, Zn with a mass percentage content of 0.001 - 2.5%, Fe with a mass percentage content of 0.01 - 0.4%, Cr with a mass percentage content of 0.001 - 0.5%, Ti with a mass percentage content of 0.001 - 0.15%, Sr with a mass percentage content of 0 - 0.05%, Mn with a mass percentage content of 0 - 0.3%, Zr with a mass percentage content of 0 - 0.3%, Li with a mass percentage content of 0 - 0.3%, and Cu with a mass percentage content of 0 - 0.1%.

[0062] The Si source, Mg source, Zn source, Fe source, Cr source, Ti source, Sr source, Mn source, Li source, Zr source, and Cu source can be aluminum master alloys.

[0063] 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 die-casting process for existing die-cast aluminum alloys is approximately 680 °C, which is relatively high. When the mixture is placed into 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 melting point of the Al-Si-Mg series die-cast aluminum alloy of the present invention is relatively low, enabling the temperature of the die-casting process of the present invention to be set relatively low, with less erosion of the mold, and thus improving the service life of the mold.

[0064] In another embodiment, the die-casting process may be a semi-solid die-casting process to produce semi-solid die-cast 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 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.

[0065] When the die-casting process is a semi-solid die-casting process, the refining process may be: mixing potassium titanate whiskers and aluminum powder to obtain a mixture; performing a pulverization process on the mixture using a low-energy ball mill under an argon protective atmosphere; when mechanically stirring or electromagnetically stirring the second mixture, adding the mixture of potassium titanate whiskers and aluminum powder to the second mixture. The addition of aluminum powder can improve the wettability between the mixture and the aluminum melt and avoid agglomeration. During the pulverization 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, it may be 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 the potassium titanate whiskers, reducing the interfacial mismatch degree and enhancing the heterogeneous nucleation ability. Potassium titanate whiskers, as heterogeneous nucleation substrates, 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, and it is suitable for making precision components such as engine cylinder liners and bearings.

[0066] In the high-pressure die casting or semi-solid die casting process, the mold used includes a moving mold and a fixed mold. Both the moving mold and the fixed mold are formed with parting surfaces, and the two parting surfaces together form a cavity for accommodating the molten mixture to mold 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 enhance the wear resistance of the mold, and further resist the erosion of chemical substances such as acids, alkalis, and salts and the thermal erosion of aluminum alloy, so as to extend the service life of the mold. 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 mass percentage content of Fe, or the sum of the mass percentage contents of Fe and Cr, or the sum of the mass percentage contents of Fe, Cr, and Mn, or the sum of the mass percentage contents of Fe, Cr, Co, and Mn can be set to be relatively low.

[0067] 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 chemically react and deposit on the parting surface to form 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 molten mixture to the mold surface, improve the demolding performance of aluminum alloy, and can be smoothly demolded even with a low content of Fe, Cr, Co, or Mn, greatly improving the elongation of aluminum alloy; the boron carbide layer can resist the erosion of chemical substances such as acids, alkalis, and salts, and can improve the corrosion resistance of aluminum alloy; the boron carbide layer can still maintain good physical and chemical properties in a high-temperature environment, and can improve the thermal stability of aluminum alloy; the boron carbide layer has an extremely low friction coefficient, improves the surface smoothness of aluminum alloy, and can significantly reduce the wear and energy consumption caused by mechanical friction of aluminum alloy products; the boron carbide layer also has high heat transfer performance. At the moment when the aluminum alloy is molded, the boron carbide layer can quickly conduct away the heat, improve the heat transfer speed of the mold, and the heat transfer speed is 2-4 times that of an ordinary mold, enabling the molded aluminum alloy to cool faster and the structure to be more refined, so as to improve the strength and elongation of aluminum alloy.

[0068] The degassing treatment is as follows: adjust the temperature of the second mixture to 700 - 740 °C, and introduce an inert gas such as argon into the second mixture using a degassing machine. The temperature of the degassing treatment can specifically be 700 °C, 710 °C, 720 °C, 730 °C, or 740 °C. The time of the degassing treatment is 10 - 30 min, and can specifically be 10 min, 15 min, 20 min, 25 min, or 30 min.

[0069] In another embodiment, the refining treatment is as follows: when introducing an inert gas such as argon into the second mixture using a degassing machine, a grain refiner can be added simultaneously. The eddy current formed by the rotating disk of the degassing machine in the second mixture can evenly disperse the grain refiner and mix it into the second mixture. 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 treatment is 10 - 30 min, and can specifically be 10 min, 15 min, 20 min, 25 min, or 30 min. The temperature of the refining treatment is 700 - 740 °C, and can specifically 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 treatment is applicable to semi-solid die casting and high-pressure casting.

[0070] 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.

[0071] 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~-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, 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, 25 h, or 30 h. The temperature of the first-stage aging treatment is relatively low. In the first-stage aging treatment, the solute atoms in the die-cast aluminum alloy parts are stabilized, and a dense GP zone aluminum alloy part is formed while avoiding the rapid precipitation of unsaturated Zn. Thus, the Zn content can be set relatively high.In the second-stage aging treatment, the volume shrinks sharply, 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, 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 in this second-stage aging treatment can further promote the segregation of solute atoms such as Si, Mg, Zn, Fe, Cr, Li, Ti, Sr, Mn, and Zr, significantly increasing the range of GP zones, increasing the nucleation rate during the third-stage aging treatment, and promoting 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 Si, Mg, Zn, Fe, Cr, Li, Ti, Sr, Mn, and Zr enables the alloy to disperse and precipitate a variety of dispersion phases containing Si, Mg, Zn, Fe, Cr, Li, Ti, Sr, Mn, and Zr during the aging stage. These dispersion phases themselves can refine the grains, increasing the alloy strength and elongation; they can also serve as the core for the heterogeneous nucleation of the β" phase, thereby accelerating the formation of the β" phase, 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. 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, the temperature of the aluminum alloy parts will drop rapidly, and fine strengthening phases will 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, the temperature of the aluminum alloy parts will drop even more rapidly, and fine strengthening phases will 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.

[0072] 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 strength 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 strength 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 Si, Mg, Zn, Fe, Cr, Li, Ti, Sr, Mn, Zr, etc., and at the same time make the alloy generate a greater degree of supercooling, significantly increasing the range of GP zones, facilitating the increase of 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 strength 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 strength 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.

[0073] In the technical solution of the present invention, the high-strength and 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5%, 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-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy has better yield strength, tensile strength and elongation rate.

[0074] 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 in the present invention 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 in the present invention 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 0.5-2%), and the mass percentage content of Li is set to 0-0.5% (preferably 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 reduce the reduction of the elongation rate of the aluminum alloy caused by high-content Mg. In order to improve the elongation rate of the aluminum alloy, the mass percentage contents of Fe and Cu in the present invention are set relatively low, which are 0.01-0.4% (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%) and Mn with a mass percentage content of 0-0.3% (preferably 0.01-0.2%) to make up for the influence on the demolding performance when the Fe content is not high, so as to ensure the demolding performance of the aluminum alloy. The combination of Cr, Mn and Li can also improve the strength and elongation rate of the aluminum alloy at the same time. The present invention also adds Zr with a mass percentage content of 0-0.3% (preferably 0.01-0.2%). The combined addition of Mn and Zr can not only reduce the usage amount of each alloy element, but also promote the mutual precipitation, further enhancing the strengthening effect. The present invention also adds Ti with a mass percentage content of 0.001-0.15% (preferably 0.01-0.1%) and Sr with a mass percentage content of 0-0.05% (preferably 0.01-0.05%), which can refine the grains, the second phase and the precipitation phase to improve the strength and elongation rate of the aluminum alloy. Sr and Zr can also promote the precipitation of 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 a second phase, avoiding dissolving in the aluminum matrix and affecting the elongation rate of the aluminum alloy. Thus, Si, Mg, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr 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, Zn, Fe, Cr, Ti, Sr, Mn, Li, Zr, 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 aluminum alloy as much as possible, and the second phase (such as Al3Fe, Mg2Si, Al2Cu, MgZn2, 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.

[0075] The method for preparing the high-strength and high-elongation Al-Si-Mg die-casting aluminum alloy also includes the step of adding at least one of a Sb source, a Sn source, a Bi source, a Ni source, a RE source, a Mo source, a Be source, a Ca source, a V source, an In source, a Ge source, a Nb source, a Te source, an Ag source, a Co source, a Cd source, a B 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-strength and 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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%.

[0080] The above are only the preferred embodiments of the present invention, and do not thereby limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy contains Al, characterized in that, The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5%, and Cu with a mass percentage content of 0-0.1%.

2. The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains Si with a mass percentage content of 6-8%, Mg with a mass percentage content of 1.2-1.8%, Zn with a mass percentage content of 0.001-2%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0.001-0.05%, Mn with a mass percentage content of 0.001-0.3%, Zr with a mass percentage content of 0.001-0.3%, Li with a mass percentage content of 0.001-0.5%, and Cu with a mass percentage content of 0.001-0.1%.

3. The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The mass ratio of Mg to Zn is 0.1-10:

1.

4. The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy according to claim 1, characterized in that, The high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy also contains at least one of Sb, Sn, Co, Bi, Ca, Be, V, Ge, Mo, Nb, Te, Ag, In, AlTiB, SiC, BN, and AlTiC. Among them, the mass percentage content of Sb is 0-0.3%, the mass percentage content of Sn is 0-0.3%, the mass percentage content of Co is 0-0.3%, the mass percentage content of Bi is 0-0.3%, 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 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%.

5. A preparation method of a high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy, comprising the following steps: Provide a Si source, a Mg source, a Zn source, an Fe source, a Cr source, a Ti source, a Sr source, a Mn source, a Li source, a Zr source, a Cu source, and an Al source; Heat-treat the Al source to obtain molten aluminum; Add the Si source, the Mg source, the Zn source, the Fe source, the Cr source, the Ti source, the Sr source, the Mn source, the Li source, the Zr source, and the 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-strength and high-elongation Al-Si-Mg series die-cast aluminum alloy. Among them, the high-strength and 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%, Zn with a mass percentage content of 0.001-2.5%, Fe with a mass percentage content of 0.01-0.4%, Cr with a mass percentage content of 0.001-0.5%, Ti with a mass percentage content of 0.001-0.15%, Sr with a mass percentage content of 0-0.05%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.3%, Li with a mass percentage content of 0-0.5%, and Cu with a mass percentage content of 0-0.1%.

6. The preparation method of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy according to claim 5, characterized in that, The preparation method of the high-strength and high-elongation Al-Si-Mg series die-cast aluminum alloy further includes a step of surface-treating the mold, and the surface treatment is to form a boron carbide layer on the parting surface of the mold.

7. The preparation method of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy according to claim 5, 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 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.

8. The preparation method of the high-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy according to claim 5, 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~-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-strength and high-elongation Al-Si-Mg series die-casting aluminum alloy according to claim 5, characterized in that, The method for preparing the high-strength and high-elongation Al-Si-Mg series die-cast aluminum alloy further includes the step of adding at least one of an Sb source, an Sn source, a Co 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, an AlTiB source, an SiC source, a BN source, and an AlTiC source to the aluminum liquid. Among them, the mass percentage content of Sb is 0 - 0.3%, the mass percentage content of Sn is 0 - 0.3%, the mass percentage content of Co is 0 - 0.3%, the mass percentage content of Bi is 0 - 0.3%, 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 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-strength and high-elongation Al-Si-Mg series die-cast aluminum alloy according to any one of claims 1 - 4, or the high-strength and high-elongation Al-Si-Mg series die-cast aluminum alloy prepared by the method for preparing the high-strength and high-elongation Al-Si-Mg series die-cast aluminum alloy according to any one of claims 5 - 9.

Images