Al-Zn series die-casting aluminum alloy, preparation method thereof and structural part

Abstract

The invention provides an Al-Zn series die-casting aluminum alloy, a preparation method thereof and a structural part. The Al-Zn series die casting aluminum alloy contains Al, the high-strength aluminum alloy material comprises the following components in percentage by mass: 6 to 15 percent of Zn, 4 to 12 percent of Si, 0.01 to 0.8 percent of Fe, 0.1 to 2 percent of Mg, 0.001 to 0.3 percent of Mn, 0 to 0.3 percent of Sb, 0 to 0.1 percent of Sr, 0 to 0.3 percent of Ti and 0 to 0.3 percent of V. The Al-Zn series die-casting aluminum alloy has better tensile strength, yield strength and elongation. Wherein the tensile strength is not lower than 350 MPa, the yield strength is not lower than 250 MPa, and the elongation is not lower than 7%.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to an Al-Zn series die-casting aluminum alloy, a preparation method thereof, and a structural member. Background Art

[0002] Al-Zn series die-casting aluminum alloys have obvious age hardening ability, so they are called self-strengthening alloys. Al-Zn series die-casting aluminum alloys also have good casting performance, cutting performance, welding performance and dimensional stability, and can avoid deformation and dimensional changes caused by the quenching process. However, the yield strength and tensile strength of existing Al-Zn series die-casting aluminum alloys need to be improved. When strengthening alloy elements are added to the aluminum alloy to improve the yield strength and tensile strength, the addition of the strengthening alloy elements will cause a decrease in elongation.

[0003] Therefore, there is an urgent need in the market for an Al-Zn series die-casting aluminum alloy with excellent yield strength, tensile strength, and elongation. Summary of the Invention

[0004] In view of the above defects of the prior art, the present invention provides an Al-Zn series die-casting aluminum alloy with better yield strength, tensile strength, and elongation.

[0005] The present invention provides an Al-Zn series die-casting aluminum alloy, which contains Al, and also contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 4-12%, Fe with a mass percentage content of 0.01-0.8%, Mg with a mass percentage content of 0.1-2%, Mn with a mass percentage content of 0.001-0.3%, Sb with a mass percentage content of 0-0.3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, and V with a mass percentage content of 0-0.3%.

[0006] Further, the Al-Zn series die-casting aluminum alloy contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 5-11%, Fe with a mass percentage content of 0.2-0.5%, Mg with a mass percentage content of 0.2-1.5%, Mn with a mass percentage content of 0.01-0.2%, Sb with a mass percentage content of 0.01-0.2%, Sr with a mass percentage content of 0.01-0.1%, Ti with a mass percentage content of 0.001-0.1%, and V with a mass percentage content of 0.001-0.1%.

[0007] Further, the sum of the mass percentage contents of Zn, Si, Fe, Mg, Mn, Sb, Sr, Ti, and V is 16-30%.

[0008] Furthermore, the Al-Zn series die-casting aluminum alloy further contains at least one of Be, Bi, Cd, Cu, Cr, Ge, Mo, Nb, Ni, Te, Sn, In, Zr, AlTiB, BN, and AlTiC. Among them, the mass percentage content of Be is 0-0.1%, the mass percentage content of Bi is 0-0.1%, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Cu is 0-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.1%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Ni is 0-0.3%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Sn is 0-0.1%, the mass percentage content of In is 0-0.1%, the mass percentage content of Zr is 0-0.2%, the mass percentage content of AlTiB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-0.5%.

[0009] The present invention also provides a preparation method of the Al-Zn series die-casting aluminum alloy, comprising the following steps: Providing a Zn source, an Si source, a Mg source, an Sb source, an Sr source, a Ti source, a V source, and an Al source; Performing a heat treatment on the Al source to obtain molten aluminum; Adding the Zn source, the Si source, the Mg source, the Sb source, the Sr source, the Ti source, and the V source to the molten aluminum to obtain a mixed liquid; and Performing die-casting treatment and aging treatment on the mixed liquid to obtain the Al-Zn series die-casting aluminum alloy, wherein the Al-Zn series die-casting aluminum alloy contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 4-12%, Fe with a mass percentage content of 0.01-0.8%, Mg with a mass percentage content of 0.1-2%, Mn with a mass percentage content of 0.001-0.3%, Sb with a mass percentage content of 0-0.3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, and V with a mass percentage content of 0-0.3%.

[0010] Furthermore, the preparation method of the Al-Zn series die-casting aluminum alloy further comprises the step of adding an Fe source and / or an Mn source to the molten aluminum.

[0011] Further, 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 40-90°C, and the time is 3-20h; the temperature of the second-stage aging treatment is -200~-100°C, and the time is 0.5~10h; the temperature of the third-stage aging treatment is 170-250°C, and the time is 5-200min. After the second-stage aging treatment, the temperature is adjusted to 170-250°C within 1-5min; the fourth-stage aging treatment is natural aging treatment or water-cooling aging treatment.

[0012] Further, the preparation method of the Al-Zn series die-casting aluminum alloy further includes adding at least one of a Be source, a Bi source, a Cd source, a Cu source, a Cr source, a Ge source, a Mo source, a Nb source, a Ni source, a Te source, a Sn source, an In source, a Zr source, AlTiB, a BN source, and AlTiC to the aluminum liquid. Among them, the mass percentage content of Be is 0-0.1%, the mass percentage content of Bi is 0-0.1%, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Cu is 0-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.1%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Ni is 0-0.3%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Sn is 0-0.1%, the mass percentage content of In is 0-0.1%, the mass percentage content of Zr is 0-0.2%, the mass percentage content of AlTiB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-0.5%.

[0013] The present invention also provides a structural member, the material of which is the above-mentioned Al-Zn series die-casting aluminum alloy, or the Al-Zn series die-casting aluminum alloy prepared by the preparation method of the above-mentioned Al-Zn series die-casting aluminum alloy.

[0014] Further, the thickness of the structural member is 1.5-15mm.

[0015] In the technical solution of the present invention, the Al-Zn series die-casting aluminum alloy contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 4-12%, Fe with a mass percentage content of 0.01-0.8%, Mg with a mass percentage content of 0.1-2%, Mn with a mass percentage content of 0.001-0.3%, Sb with a mass percentage content of 0-0.3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, and V with a mass percentage content of 0-0.3%. The elements with the above contents interact with each other and affect each other, so that the Al-Zn series die-casting aluminum alloy has better yield strength, tensile strength, and elongation rate. Detailed implementation mode

[0016] 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.

[0017] An embodiment of the present invention provides an Al-Zn series die-casting aluminum alloy, which has better yield strength, tensile strength, and elongation rate. The Al-Zn series die-casting aluminum alloy is suitable for making structural parts, especially thin-walled structural parts. The thin-walled structural part has better strength and a smooth surface. When the thickness of the thin-walled structural part is 1.5-15 mm, cracking will not occur.

[0018] The thickness of the thin-walled structural part can specifically be 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.

[0019] The Al-Zn series die-casting aluminum alloy contains Al, and also contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 4-12%, Fe with a mass percentage content of 0.01-0.8%, Mg with a mass percentage content of 0.1-2%, Mn with a mass percentage content of 0.001-0.3%, Sb with a mass percentage content of 0-0.3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, and V with a mass percentage content of 0-0.3%.

[0020] In one embodiment, the Al-Zn series die-casting aluminum alloy contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 5-11%, Fe with a mass percentage content of 0.2-0.5%, Mg with a mass percentage content of 0.2-1.5%, Mn with a mass percentage content of 0.01-0.2%, Sb with a mass percentage content of 0.01-0.2%, Sr with a mass percentage content of 0.01-0.1%, Ti with a mass percentage content of 0.001-0.1%, and V with a mass percentage content of 0.001-0.1%.

[0021] The mass percentage content of Zn can specifically be 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%, or 15%.

[0022] The mass percentage content of Si can specifically be 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, or 12%.

[0023] 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%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, or 0.8%.

[0024] The mass percentage content of Mg 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%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0025] The mass percentage content of Sr may specifically be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%.

[0026] The mass percentage content of Sb, Ti, Mn, and V may specifically be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 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%.

[0027] The sum of the mass percentage contents of Zn, Si, Fe, Mg, Mn, Sb, Sr, Ti, and V is 16 - 30%, and may specifically be 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%, or 30%. With such settings, while ensuring excellent mechanical properties (including strength and elongation) and die-casting properties of the aluminum alloy, the addition of excessive elements is avoided, which may cause the density of the aluminum alloy to be too high.

[0028] The sum of the mass percentage contents of Zn, Si, and Mg is 11.1 - 28%, and may specifically be 11.1%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 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%, or 28%. Within this range, the Al-Zn series die-casting aluminum alloy can ensure better strength and forming properties.

[0029] The high-strength Al-Zn series die-casting aluminum alloy also contains impurities with a total mass percentage content of less than 1%, preferably less than 0.6% impurities, and more preferably less than 0.3% impurities. The aluminum source of the present invention can be electrolytic aluminum, and of course, it can also be of other types. Bauxite contains Fe impurities. When electrolytic aluminum is obtained by electrolytic treatment using bauxite as a raw material, the high-strength Al-Zn series die-casting aluminum alloy will inevitably contain Fe impurities. The mass percentage content of Fe impurities can be 0.001-0.1%, specifically 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. When using recycled aluminum as the aluminum source, the mass percentage content of Fe impurities can be 0.001-0.5%, specifically 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%.

[0030] Impurities brought by raw materials or during the preparation process, especially when using recycled aluminum as a raw material, also include Mn and / or Cr. The mass percentage content of Mn and Cr can be 0.001-0.3%, specifically 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%. Cr can transform the acicular β-Fe phase into the α-Fe phase to improve the Fe morphology and eliminate the harmful effects of Fe. Cr also easily forms a dispersion phase with Fe to reduce the Fe content and minimize the harmful effects of Fe; (CrFe)Al7 and (CrMn)Al formed by Cr in the recycled aluminum liquid 12Intermetallic compounds such as can hinder the nucleation and growth processes of recrystallization, improve the tensile strength, yield strength, elongation rate of aluminum alloys, and reduce the stress corrosion cracking sensitivity; various chromium-containing fine compounds formed by Cr in aluminum alloys can be redissolved in the α phase during the solution stage and precipitate dispersedly during the aging stage to form various Cr-containing phases, such as α-AlCrSi dispersed phases, etc. These Cr-containing phases can serve as the cores for the heterogeneous nucleation of β" and θ" phases, accelerate the formation of β" and θ" phases, and thus improve the tensile strength and yield strength of aluminum alloys. At the same time, the dispersed precipitation of Cr-containing phases in the matrix will inevitably have a certain delaying effect on the formation of θ′ phases precipitated at grain boundaries; Mn and Cr can form dispersed α-Al(FeMnCr)Si phases with Fe and Si. The α-Al(FeMnCr)Si phase has a high bulk density and strong thermal stability, and pinning the grain boundaries can effectively control the grain growth process of recycled aluminum grains, thereby controlling the grain size; during the die-casting process, the temperature cooling rate is relatively large (10 - 60 K / S), and the metastable phase Al3V obtained by the rapid cooling method will form a large number of fine and dispersed ellipsoidal Al(VCrTi)Si phases with Cr, Si, and Ti in the aluminum alloy, which can prevent dislocation movement and the nucleation and growth of recrystallization, and significantly improve the tensile strength and yield strength of aluminum alloys.

[0031] In the die-cast aluminum alloy industry, it is generally believed that when the sum of the mass percentage contents of Fe and Mn, or the sum of the mass percentage contents of Fe, Mn, and Cr is greater than 0.7%, the demolding of die-cast aluminum alloys can be achieved. In the high-strength Al-Zn series die-cast aluminum alloy of the present invention, good demolding performance can be achieved without adding ferrous metals (such as Fe, Mn, and Cr), wherein Fe, Mn, and Cr come from raw materials. Through experimental verification, when Zn and Si are combined within the above content range of the present invention, better demolding performance can be achieved, and the affinity and thermal corrosion degree for steel molds are greatly reduced. Thus, the present invention can achieve good demolding performance without adding at least one of Fe, Mn, and Cr to the aluminum liquid. Of course, a certain content of Fe and / or Mn can be added to the present invention to improve the demolding performance.

[0032] The elements and their contents in the aluminum alloy can be detected to obtain the Fe and / or Mn content. When the Fe and / or Mn content is too high, the Fe and / or Mn content can be adjusted to an appropriate level through boronization treatment, or the Fe and / or Mn content can be adjusted to an appropriate level by adding aluminum ingots (such as pure aluminum ingots); when the Fe and / or Mn content is too low, an Fe source and / or an Mn source can also be added to adjust their content to an appropriate level. Of course, an Fe source and / or an Mn source can also not be added, and the Fe and Mn content can be maintained at a relatively low level.

[0033] In the technical solution of the present invention, the Al-Zn series die-casting aluminum alloy contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 4-12%, Fe with a mass percentage content of 0.01-0.8%, Mg with a mass percentage content of 0.1-2%, Mn with a mass percentage content of 0.001-0.3%, Sb with a mass percentage content of 0-0.3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, and V with a mass percentage content of 0-0.3%. The elements with the above contents interact with each other, making the Al-Zn series die-casting aluminum alloy have better tensile strength, yield strength, elongation, and forming performance. The structural parts made of the Al-Zn series die-casting aluminum alloy have better surface smoothness and will not crack even when the thickness is 1.5-15 mm. Specifically: (1) The mass percentage content of Zn is 6-15%. Zn can be dissolved in the aluminum matrix to improve the tensile strength and yield strength of the aluminum alloy through solid solution strengthening. There is a complex network grain boundary structure composed of fine lamellar α+η phase and η phase at the grain boundaries of the aluminum alloy. The complex network grain boundary structure can hinder the dislocation movement of the aluminum alloy, improving the tensile strength, yield strength, and hardness of the aluminum alloy; after aging treatment, the precipitated elemental Zn can further improve the tensile strength and yield strength of the aluminum alloy; moreover, elemental Zn is a non-brittle phase between the grain boundaries, which can increase the eutectic structure of the aluminum alloy to improve the fluidity of the aluminum alloy, making the aluminum alloy suitable for die-casting; Zn within this content range can also reduce the solidification temperature of the aluminum alloy, greatly reducing the affinity and thermal corrosion degree of the aluminum alloy to die steel (such as H13 steel), and improving the service life of the die; as the Zn content increases, the solidus temperature of the aluminum alloy decreases, causing melt superheat, and the melt supercooling degree increases with the increase of the melt superheat degree, which can accelerate the nucleation rate and reduce the grain size; (2) The mass percentage content of Si is 4-12%. Si can improve the fluidity and density of the aluminum alloy, thereby improving the tensile strength, yield strength, and forming performance of the aluminum alloy; Si can also react with other elements to form the second phase, further improving the tensile strength and yield strength of the aluminum alloy. Specifically, Si can react with Al, Fe, Mg, Mn, B, etc. to form second phases such as Mg2Si, AlFeSi, AlMnSi, AlFeMgSi, AlFeMnSi, AlFeSiNi, AlFeMgSiNi, AlFeSiB; (3)The mass percentage content of Fe is 0.01 - 0.8%. Fe can reduce the tendency of sticking to the mold of aluminum alloy castings and improve the demolding performance of aluminum alloys. Fe can react with other elements to form the second phase to improve the tensile strength and yield strength of aluminum alloys. Specifically, Fe can react with Al, Si, Mg, Mn, Ni, B, etc. to form the second phases such as Al3Fe, AlFeSi, AlFeMgSi, AlFeSiNi, AlFeMgSiNi, AlFeMnSi, FeNiAl9, AlFeSiB, etc. However, the presence of β-Fe-rich phase in the aluminum matrix will reduce the elongation of aluminum alloys. (4)The mass percentage content of Mg is 0.1 - 2%. The solid solution strengthening of Mg in the aluminum matrix can improve the tensile strength and yield strength of aluminum alloys. Mg can react with other elements to form the second phase to improve the tensile strength and yield strength of aluminum alloys. Specifically, Mg can react with Al, Fe, Si, Zn, Ni, etc. to form the second phases such as Mg2Si, Mg2Zn, Mg2SiZn, AlFeMgSi, AlFeMgSiNi, etc. In addition, Mg can also promote the precipitation of the second phases such as AlFeSi, AlFeMnSi, AlFeSiB, etc., improve their volume fraction and dispersion degree, and reduce the solid solubility of the above elements in the aluminum matrix. (5)The mass percentage content of Mn is 0.001 - 0.3%. Mn can form independent Mn-rich hardening phases of Al6Mn and Al6FeMn in zinc aluminum alloys to improve the tensile strength and yield strength of aluminum alloys. Mn reacts with Fe to form fine and dispersed α-Al(FeMn)Si phase, which can improve and regulate the β-Fe-rich phase. Mn can significantly refine the recrystallized grains and the second phase, effectively transform the coarse needle-shaped or lamellar α-AlFeSi phase into small granular α-Al(FeMn)Si dispersed particles to improve the morphology of Fe, and then improve the tensile strength, yield strength and elongation of aluminum alloys. (6)The mass percentage content of Sb is not more than 0.3%. Sb can react with Mg, Cd, etc. to form strengthening phases such as Mg3(SbCd)2, Mg3Sb2, which can improve the tensile strength and yield strength of aluminum alloys. Sb can also improve the precipitation of elements such as Zn, Ni, etc. in the aluminum alloy matrix, which can improve the tensile strength and yield strength of aluminum alloys. Sb can also be used as a modifier, which can effectively reduce the size of eutectic silicon lamellae, greatly reduce the possibility of eutectic silicon lamellae cutting the aluminum matrix, and further improve the tensile strength, yield strength and elongation of aluminum alloys. (7) The mass percentage content of Sr is not more than 0.1%. As a modifier, Sr can change the behavior of intermetallic compound phases crystallographically. By means of heterogeneous nucleation theory or twin trough mechanism, the aluminum alloy is modified to refine grains, secondary phases and precipitated phases, so as to improve the elongation of the aluminum alloy. For example, it can refine phases such as Al2Cu, Mg2Zn, and Mg2Si to reduce the adverse effects when the Mg content is relatively high. Also, Sr can transform the coarse needle-like β-AlFeSi and β-AlFeMnSi phases in the ingot into small granular Chinese character-shaped α-AlFeSi and α-Al(FeMn)Si phases, reducing the homogenization time of the ingot and improving the yield strength, tensile strength and elongation of the aluminum alloy; Sr preferentially combines with Fe to form dispersion strengthening, reducing the solid solubility of Fe, so as to improve the yield strength and tensile strength of the aluminum alloy; (8) The mass percentage content of Ti is not more than 0.3%. The TiAl2 phase formed by the reaction of Ti and Al can be used as a non-spontaneous core during crystallization to refine grains, secondary phases and precipitated phases, thereby improving the tensile strength, yield strength and elongation of the aluminum alloy; (9) The mass percentage content of V is not more than 0.3%. V forms refractory compounds such as Al3V, Al 10 V, VAl 11 , and Al(VMnTi)Si in the aluminum alloy, which can play the role of refining grains and dispersion strengthening, thereby improving the tensile strength, yield strength and elongation of the aluminum alloy; V can also refine the recrystallized structure and increase the recrystallization temperature to improve the tensile strength, yield strength and elongation of the aluminum alloy; during the die-casting process, the temperature cooling rate is relatively large, and the metastable phase Al3V obtained by the rapid cooling method will form a large number of fine and dispersed ellipsoidal Al(VCrTi)Si phases with Cr, Si, and Ti in the aluminum alloy, which can prevent dislocation movement and recrystallization nucleation and growth, significantly improving the tensile strength and yield strength of the aluminum alloy.

[0034] In summary, Zn, Si, Fe, Mg, Mn, Sb, Sr, Ti, and V within the above content ranges cooperate with each other as a whole, enabling the invented Al-Zn series die-casting aluminum alloy to have better strength, yield strength, elongation, and forming performance. Among them, the tensile strength of the Al-Zn series die-casting aluminum alloy of the present invention is not less than 350 MPa, the yield strength is not less than 250 MPa, the elongation is not less than 7%, and the length of the fluidity sample is not less than 2320 mm. And the density of the Al-Zn series die-casting aluminum alloy is relatively low, not higher than 2.8 g / cm 3 , making the Al-Zn series die-casting aluminum alloy suitable for making lightweight thin-walled aluminum alloy structural parts.

[0035] The Al-Zn series die-casting aluminum alloy further contains AlTiB with a mass percentage content of 0-1% and SiC with a mass percentage content of 0-35%. The mass percentage content of AlTiB 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%. 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%.

[0036] 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%.

[0037] When AlTiB and SiC are used in combination, C-TiB2 particle complexes are formed at the SiC-Al interface. The C atoms in SiC can 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 0.3-0.8% and SiC with a mass percentage content of 4-10% are combined with each other, the tensile strength, yield strength, elongation, wear resistance, corrosion resistance, and thermal stability of the aluminum alloy can be greatly improved.

[0038] The Al-Zn series die-casting aluminum alloy also contains AlTiC with a mass percentage content of 0-0.5%, specifically, it can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. As a grain refiner, the particle size of AlTiC is about several microns, and it is not easy to aggregate, having a better effect of fine grain strengthening. When AlTiC acts in combination with RE, the refining effect can be enhanced, and the elongation rate of the aluminum alloy can be significantly improved.

[0039] The Al-Zn series die-casting aluminum alloy also contains BN with a mass percentage content of 0-1%. The mass percentage content of BN 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%. BN has good wettability with Al and can form a strong interfacial bond with the Al matrix. Al atoms and B atoms are stably bonded to each other through covalent bonds to form a protective layer (i.e., the AlB2 and AlN nanonucleation layer) that is not easy to react with water and air, so as to improve the yield strength and tensile strength of the Al-Zn aluminum alloy. Specifically, AlB2 and AlN in the protective layer are nanodispersed at the interface and grain boundaries of the aluminum matrix, which can refine the grains and promote the uniform nucleation of the grains, so as to improve the yield strength and tensile strength of the aluminum alloy; the size of BN is nanoscale, and its fiber strength and elastic modulus are about 2-4 times that of carbon fiber, which can significantly improve the dimensional stability of aluminum alloy structural parts.

[0040] The Al-Zn series die-casting aluminum alloy may further contain RE with a mass percentage content of 0-0.3%, specifically, it may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%. RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Sc, and Gd. RE can also promote the precipitation of strengthening phases and dispersion phases, further improving the yield strength and tensile strength of the aluminum alloy; RE within the above content range can refine grains, secondary phases, and precipitation phases to improve the yield strength, tensile strength, and elongation rate of the aluminum alloy.

[0041] The Al-Zn series die-casting aluminum alloy may further contain B with a mass percentage content of 0-0.08%. The mass percentage content of B may specifically be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, or 0.08%. B can refine grains, secondary phases, and precipitation phases to improve the elongation rate of the aluminum alloy; the boriding effect of B can also purify the aluminum alloy liquid, further improving the yield strength, tensile strength, and elongation rate of the aluminum alloy; B can inhibit the segregation of Ti3Al. Therefore, the effect is better when Ti and B are used together.

[0042] The Al-Zn series die-casting aluminum alloy may further contain Be with a mass percentage content of 0-0.1%. The mass percentage content of Be may specifically be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. Be can refine the Si phase to reduce or eliminate the adverse effects of Si on the properties of the aluminum alloy, thereby improving the yield strength, tensile strength, and elongation rate of the aluminum alloy.

[0043] The Al-Zn series die-casting aluminum alloy further contains Bi with a mass percentage content of 0-0.1%. The specific mass percentage content of Bi can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. Bi can reduce the surface tension of the aluminum melt and decrease the contact angle between Al and Si, making it easier for the Si growth front to be inhibited by Al, thereby reducing the size of the eutectic silicon. In this way, the elongation rate of the aluminum alloy can be improved.

[0044] The Al-Zn series die-casting aluminum alloy may further contain Cd with a mass percentage content of 0-0.2%. The specific mass percentage content of Cd can be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 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 react with Al, RE, Mg, Si, Fe, Sb, Bi, etc. to form strengthening phases such as REAl2Cd3, Al3Cd, Al2Cd3, Mg2(SiCdREFe), Mg3(SbCd)2, Mg3(BiCd)2, etc., to improve the tensile strength and yield strength of the aluminum alloy; Cd will form a large number of Cd-vacancy clusters during the aging stage, promoting and accelerating the precipitation of phases such as AlFeSi, AlFeMnSi, AlFeSiB, etc., to reduce the solid solubility of the above elements in the aluminum matrix; Cd can also refine grains, second phases, and precipitation phases to improve the elongation rate of the aluminum alloy.

[0045] The Al-Zn series die-casting aluminum alloy may also contain Cu with a mass percentage content of 0-0.2%. The specific mass percentage content of Cu may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. 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 does not exceed 0.2%, the elongation rate of the aluminum alloy will not decrease sharply.

[0046] It can be understood that when the Al-Zn series die-casting aluminum alloy of the present invention contains 0.1-2% of Mg, good yield strength and tensile strength can be obtained without adding Cu to the aluminum alloy.

[0047] The Al-Zn series die-casting aluminum alloy may also contain Ge with a mass percentage content of 0-0.1%. The specific mass percentage content of Ge may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. Ge can react with Al, Si, etc. to generate second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe, etc. to improve the tensile strength and yield strength of the aluminum alloy; Ge can also refine grains, second phases and precipitation phases to improve the elongation rate of the aluminum alloy; when the Al-Zn series die-casting aluminum alloy contains Ge and RE at the same time, the cooperation between Ge and RE can significantly refine grains, second phases and precipitation phases, and further improve the elongation rate of the aluminum alloy.

[0048] The Al-Zn series die-casting aluminum alloy may further contain Mo with a mass percentage content of 0 - 0.1%. The specific mass percentage content of Mo may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. Mo can improve the tensile strength and yield strength of the aluminum alloy; Mo can also refine the grains to improve the elongation rate of the aluminum alloy. When Cr and Mo are added in combination, multi-element phases rich in Cr and Mo can be formed, significantly improving the tensile strength of the aluminum alloy.

[0049] The Al-Zn series die-casting aluminum alloy may further contain Nb with a mass percentage content of 0 - 0.1%. The specific mass percentage content of Nb may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. Nb can improve the tensile strength and yield strength of the aluminum alloy; Nb can also refine the grains, second phases, and precipitated phases to improve the elongation rate of the aluminum alloy. When the Al-Zn 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 tensile strength and yield strength of the aluminum alloy.

[0050] The Al-Zn series die-casting aluminum alloy may further contain Ni with a mass percentage content of 0 - 0.3%. The specific mass percentage content of Ni may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 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%. Ni can improve the tensile strength and yield strength of the aluminum alloy; Ni can also refine the grains, second phases, and precipitated phases to improve the elongation rate of the aluminum alloy.

[0051] The Al-Zn series die-casting aluminum alloy may also contain Te with a mass percentage content of 0-0.1%. The mass percentage content of Te may specifically be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. Te can modify eutectic silicon, shortening the eutectic silicon along the length direction to improve the elongation rate of the aluminum alloy; when the Al-Zn series die-casting aluminum alloy contains Sb and Te simultaneously, fine petal-shaped primary crystals can be formed, further improving the yield strength, tensile strength, and elongation rate of the aluminum alloy.

[0052] The Al-Zn series die-casting aluminum alloy may also contain Sn with a mass percentage content of 0-0.1%. The mass percentage content of Sn may specifically be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. Sn can improve the tensile strength and yield strength of the aluminum alloy; Sn can also effectively inhibit the growth of the second phase and promote the dispersed distribution of the second phase to improve the elongation rate of the aluminum alloy.

[0053] The Al-Zn series die-casting aluminum alloy may also contain In with a mass percentage content of 0-0.1%. The mass percentage content of In may specifically be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, or 0.1%. In can improve the tensile strength and yield strength of the aluminum alloy; In can also refine grains, the second phase, and precipitated phases to improve the elongation rate of the aluminum alloy.

[0054] The Al-Zn series die-casting aluminum alloy may further contain Zr with a mass percentage content of 0-0.2%. The specific mass percentage content of Zr may be 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.2%. Zr can improve the yield strength and tensile strength of the aluminum alloy; Zr can also form Al3Zr phase in the aluminum alloy, and the Al3Zr phase can refine grains, second phases and precipitation phases to improve the elongation of the aluminum alloy; Mn can form independent Al6Mn and Al6FeMn manganese-rich hardening phases in high-zinc aluminum alloys. The Mn-rich phases are distributed at or near the grain boundaries to pin the 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 action 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, Al3(Zr,Mn) phase and Al6(FeMnZr) phase, and the strengthening effect is much greater than the strengthening effect when Mn or Zr is added alone.

[0055] In one embodiment, the mass percentage content ratio of Zr to Mn is 0.1-1:1, and specifically may 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.

[0056] The present invention also provides a preparation method of an Al-Zn series die-casting aluminum alloy, including the following steps: Providing a Zn source, a Si source, a Mg source, an Sb source, a Sr source, a Ti source, a V source, and an 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 Zn source, the Mg source, the Sb source, the Sr source, the Ti source, and the V 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 a rough aluminum alloy blank; and The rough aluminum alloy blank is subjected to aging treatment to obtain the Al-Zn series die-casting aluminum alloy. Among them, the Al-Zn series die-casting aluminum alloy contains 6-15% by mass of Zn, 4-12% by mass of Si, 0.01-0.8% by mass of Fe, 0.1-2% by mass of Mg, 0.001-0.3% by mass of Mn, 0-0.3% by mass of Sb, 0-0.1% by mass of Sr, 0-0.3% by mass of Ti, and 0-0.3% by mass of V.

[0057] The Zn source, Si source, Mg source, Sb source, Sr source, Ti source, and V source can be aluminum master alloys.

[0058] In one embodiment, the die-casting treatment can be high-pressure casting, the temperature is 590-650 °C, preferably 590-610 °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. The temperature of the die-casting treatment of the existing die-casting aluminum alloy is about 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 melting point of the Al-Zn series die-casting aluminum alloy of the present invention is relatively low, about 590-650 °C, so that the temperature of the die-casting treatment of the present invention can be set relatively low, with less erosion of the mold, and the service life of the mold can be improved; the solidification temperature range of the Al-Zn series die-casting aluminum alloy of the present invention is very wide, with excellent die-casting performance, and is suitable for making thin-walled structural parts with complex structures; the η-Zn phase in the Al-Zn series die-casting aluminum alloy of the present invention has a close-packed hexagonal lattice structure and has good smearing performance, so that the Al-Zn series die-casting aluminum alloy of the present invention has self-lubricating characteristics. Therefore, the Al-Zn series die-casting aluminum alloy of the present invention has better forming performance and demolding performance (the cooperation of 6-15 wt% of Zn and 4-12 wt% of Si), and is suitable for high-pressure die-casting forming. The preparation method of the Al-Zn series die-casting aluminum alloy has the advantages of low cost and suitability for large-scale mass production. Among them, the mold used in the die-casting treatment can be a die-casting specimen mold that meets the aluminum alloy standard (GB / T 13822-2017), and a B-type thin-walled sheet specimen with a thickness of 1.5-15 mm is made. The surface of the B-type thin-walled sheet specimen is smooth and no cracking occurs.

[0059] In another embodiment, the die-casting process may be a semi-solid die-casting process. In the semi-solid die-casting process, a device that can increase "flow + stirring" is used to improve the uniformity of the second mixed liquid to obtain a semi-solid slurry. Combining with the 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 mixed liquid 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.

[0060] 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; pulverizing the mixture using a low-energy ball mill under an argon protective atmosphere; when mechanically stirring or electromagnetically stirring the second mixed liquid, adding the mixture of potassium titanate whiskers and aluminum powder to the second mixed liquid. The addition of aluminum powder can improve the wettability between the mixture and the aluminum melt and avoid agglomeration. During the pulverizing 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 proportion of the mixture is 3 - 10% of the mass of the second mixed liquid, specifically it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%. Utilizing the crystallographic orientation relationship between potassium titanate whiskers and α-Al, by controlling the temperature and holding time of the second mixed liquid, 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 an inhomogeneous 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 microstructure. 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.

[0061] 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 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, specifically it can be 10 min, 15 min, 20 min, 25 min, or 30 min.

[0062] In another embodiment, the refining treatment is as follows: when an inert gas such as argon is introduced into the second mixed liquid 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 liquid can evenly disperse the grain refiner and mix it into the second mixed liquid. The grain refiner can refine the alloy structure to improve the strength and elongation rate of the aluminum alloy, and has the advantages of good dispersibility and low cost. The time of the refining treatment is 10 - 30 min, specifically it can be 10 min, 15 min, 20 min, 25 min, or 30 min. The temperature of the refining treatment 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 treatment is applicable to semi-solid die casting and high-pressure casting.

[0063] 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 40 - 90°C, specifically it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°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 5 - 200 min, specifically it can be 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, 180 min, 190 min, or 200 min. The temperature of the first-stage aging treatment is relatively low. During the first-stage aging treatment, the atoms in the die-cast aluminum alloy blank are stabilized to stabilize the form of the aluminum alloy blank, and at the same time, the rapid precipitation of unsaturated Zn is avoided.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, which improves 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 Zn, Mg, Cu, Ni, and Si, significantly increasing the GP zone range, and can increase the nucleation rate during the third-stage aging treatment, 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 zone gradually transforms into a precipitate phase with a smaller size but a larger volume fraction, 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.

[0064] The aging treatment may further include a fourth-stage aging treatment, and the fourth-stage aging treatment can be natural aging treatment or water-cooled aging treatment. After the fourth-stage aging treatment, the elongation of the aluminum alloy is further improved, but the strength decreases. The natural aging treatment is to place the aluminum alloy blank 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 blank 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 blank will drop rapidly, and the fine strengthening phases continue to precipitate but the precipitation rate will also decrease, further improving the yield strength, tensile strength, and elongation of the aluminum alloy. During the water-cooled aging treatment process, the temperature of the aluminum alloy blank will drop even more rapidly, and the fine strengthening phases continue to precipitate but the precipitation rate will decrease even faster, further improving the yield strength, tensile strength, and elongation of the aluminum alloy. The yield strength, tensile 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.

[0065] The aging treatment may further include a fourth-stage aging treatment and a fifth-stage aging treatment. The fourth-stage aging treatment may be natural aging treatment, and the fifth-stage aging treatment may be water-cooled aging treatment. The natural aging treatment is to place the aluminum alloy blank after the third-stage aging treatment at room temperature for 0.5 - 5 h, specifically it can be 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 blank after the natural aging treatment in normal-temperature water for 0.5 - 5 h, specifically it can be 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 blank will drop rapidly, and fine strengthening phases will continue to precipitate but the precipitation rate will also decrease, and the yield strength, tensile strength, and elongation rate of the aluminum alloy will be further improved. During the water-cooled aging treatment process, the temperature of the aluminum alloy blank will drop further, and fine strengthening phases will continue to precipitate but the precipitation rate will also decrease further and decrease faster, and the yield strength, tensile strength, and elongation rate of the aluminum alloy will be further improved.

[0066] In the technical solution of the present invention, the cooperation of Zn, Si, Fe, Mg, Mn, Sb, Sr, Ti, and V within the above content ranges can make the Al-Zn series die-casting aluminum alloy of the invention have better yield strength, tensile strength, elongation rate, and forming performance. Among them, the tensile strength of the Al-Zn series die-casting aluminum alloy of the present invention is not less than 350 MPa, the yield strength is not less than 250 MPa, the elongation rate is not less than 7%, the length of the fluidity specimen is not less than 2320 mm, and the density is not higher than 2.8 g / cm 3 . Specifically: The cooperation of Zn, Si, Fe, Mg, Mn, Sb, Sr, Ti, and V within the above content ranges can make the Al-Zn series die-casting aluminum alloy of the invention have better strength, yield strength, elongation rate, and forming performance; by adjusting the sum of the mass percentage contents of Zn, Si, and Mg, the Al-Zn series die-casting aluminum alloy can have better strength, yield strength, and elongation rate; by adjusting the sum of the mass percentage contents of Zn, Si, Fe, Mg, Mn, Sb, Sr, Ti, and V, the Al-Zn series die-casting aluminum alloy can be controlled to have a lower density; combined with refining treatment and aging treatment, the strength and elongation rate of the Al-Zn series die-casting aluminum alloy can be further improved.

[0067] The preparation method of the Al-Zn series die-casting aluminum alloy further includes the step of adding at least one of an RE source, a B source, a Be source, a Bi source, a Cd source, a Cu source, a Ge source, a Mo source, a Nb source, a Ni source, a Te source, a Sn source, an In source, an AlTiB source, a BN source, and an AlTiC source to the first mixed solution. The above elements can at least be used to improve the tensile strength, yield strength, and / or elongation rate of the aluminum alloy, and obtain an Al-Zn series die-casting aluminum alloy with more excellent properties. The raw materials of the alloying elements can be aluminum master alloys.

[0068] Examples For the components and contents of the aluminum alloys in Examples 1 to 10, please refer to Table 1, and for the performance test results, please refer to Table 2.

[0069] Table 1 Components and Contents of Aluminum Alloys in Examples 1 to 10 For simplicity of expression, all impurity elements and contents are not shown.

[0070] Table 2 Performance Test Results of Aluminum Alloys in Examples 1 to 10 When the aluminum alloys in Examples 1 to 10 are made into thin-walled structural parts with a thickness of 2 mm, the surfaces of the structural parts are smooth and no cracking occurs. The tensile strength, yield strength, elongation rate, fluidity, and density of the thin-walled structural parts are tested. The test results are shown in Table 2.

[0071] Table 2 shows that: the aluminum alloys in Examples 1 to 10 of the present invention have better tensile strength, yield strength, elongation rate, and fluidity. Specifically, the tensile strength of the aluminum alloys in Examples 1 to 10 of the present invention is not less than 350 MPa, the yield strength is not less than 250 MPa, the elongation rate is not less than 7%, the length of the fluidity sample is not less than 2320 mm, and the density is not higher than 2.8 g / cm 3 .

[0072] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept 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. An Al-Zn series die-casting aluminum alloy contains Al, and is characterized in that, The Al-Zn series die-casting aluminum alloy further contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 4-12%, Fe with a mass percentage content of 0.01-0.8%, Mg with a mass percentage content of 0.1-2%, Mn with a mass percentage content of 0.001-0.3%, Sb with a mass percentage content of 0-0.3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, and V with a mass percentage content of 0-0.3%.

2. The Al-Zn series die-casting aluminum alloy according to claim 1, characterized in that, The Al-Zn series die-casting aluminum alloy contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 5-11%, Fe with a mass percentage content of 0.2-0.5%, Mg with a mass percentage content of 0.2-1.5%, Mn with a mass percentage content of 0.01-0.2%, Sb with a mass percentage content of 0.01-0.2%, Sr with a mass percentage content of 0.01-0.1%, Ti with a mass percentage content of 0.001-0.1%, and V with a mass percentage content of 0.001-0.1%.

3. The Al-Zn series die-casting aluminum alloy according to claim 1, wherein The sum of the mass percentage contents of Zn, Si, Fe, Mg, Mn, Sb, Sr, Ti, and V is 16-30%.

4. The Al-Zn series die-casting aluminum alloy according to claim 1, characterized in that, The Al-Zn series die-casting aluminum alloy further contains at least one of Be, Bi, Cd, Cu, Cr, Ge, Mo, Nb, Ni, Te, Sn, In, Zr, AlTiB, BN, and AlTiC. Among them, the mass percentage content of Be is 0-0.1%, the mass percentage content of Bi is 0-0.1%, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Cu is 0-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.1%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Ni is 0-0.3%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Sn is 0-0.1%, the mass percentage content of In is 0-0.1%, the mass percentage content of Zr is 0-0.2%, the mass percentage content of AlTiB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-0.5%.

5. A preparation method of an Al-Zn series die-casting aluminum alloy, comprising the following steps: Providing a Zn source, a Si source, a Mg source, an Sb source, an Sr source, a Ti source, a V source, and an Al source; Performing a heat treatment on the Al source to obtain molten aluminum; Adding the Zn source, the Si source, the Mg source, the Sb source, the Sr source, the Ti source, and the V source to the molten aluminum to obtain a mixed liquid; And The mixed liquid is subjected to die-casting treatment and aging treatment to obtain the Al-Zn series die-casting aluminum alloy. Among them, the Al-Zn series die-casting aluminum alloy contains Zn with a mass percentage content of 6-15%, Si with a mass percentage content of 4-12%, Fe with a mass percentage content of 0.01-0.8%, Mg with a mass percentage content of 0.1-2%, Mn with a mass percentage content of 0.001-0.3%, Sb with a mass percentage content of 0-0.3%, Sr with a mass percentage content of 0-0.1%, Ti with a mass percentage content of 0-0.3%, and V with a mass percentage content of 0-0.3%.

6. The preparation method of the Al-Zn series die-casting aluminum alloy according to claim 5, characterized in that, The preparation method of the Al-Zn series die-casting aluminum alloy further includes the step of adding an Fe source and / or an Mn source to the aluminum liquid.

7. The preparation method of the Al-Zn series die-casting aluminum alloy according to claim 5, characterized in that, 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 40-90°C, and the time is 3-20h; the temperature of the second-stage aging treatment is -200~-100°C, and the time is 0.5~10h; the temperature of the third-stage aging treatment is 170-250°C, and the time is 5-200min. After the second-stage aging treatment, the temperature is adjusted to 170-250°C within 1-5min; the fourth-stage aging treatment is natural aging treatment or water-cooled aging treatment.

8. The preparation method of the Al-Zn series die-casting aluminum alloy according to claim 5, characterized in that, The preparation method of the Al-Zn series die-casting aluminum alloy further includes adding at least one of a Be source, a Bi source, a Cd source, a Cu source, a Cr source, a Ge source, a Mo source, a Nb source, a Ni source, a Te source, a Sn source, an In source, a Zr source, AlTiB, a BN source, and an AlTiC to the aluminum liquid. Among them, the mass percentage content of Be is 0-0.1%, the mass percentage content of Bi is 0-0.1%, the mass percentage content of Cd is 0-0.2%, the mass percentage content of Cu is 0-0.2%, the mass percentage content of Cr is 0.001-0.3%, the mass percentage content of Ge is 0-0.1%, the mass percentage content of Mo is 0-0.1%, the mass percentage content of Nb is 0-0.1%, the mass percentage content of Ni is 0-0.3%, the mass percentage content of Te is 0-0.1%, the mass percentage content of Sn is 0-0.1%, the mass percentage content of In is 0-0.1%, the mass percentage content of Zr is 0-0.2%, the mass percentage content of AlTiB is 0-1%, the mass percentage content of BN is 0-1%, and the mass percentage content of AlTiC is 0-0.5%.

9. A structural member, characterized in that, The material of the structural member is the Al-Zn series die-casting aluminum alloy described in any one of claims 1-4, or the Al-Zn series die-casting aluminum alloy prepared by the preparation method of the Al-Zn series die-casting aluminum alloy described in any one of claims 5-8.

10. The structural member according to claim 9, characterized in that, The thickness of the structural member is 1.5-15mm.

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