High-strength al-zn-cu series die-casting aluminum alloy and preparation method and structural member thereof

Abstract

The application provides a high-strength Al-Zn-Cu series die-casting aluminum alloy and a preparation method and a structural member thereof. The high-strength Al-Zn-Cu series die-casting aluminum alloy contains Al, and further contains Zn with a mass percentage of 35-55%, Si with a mass percentage of 0.05-1.5%, Cu with a mass percentage of 0.01-3.5%, Mn with a mass percentage of 0-0.3%, Zr with a mass percentage of 0-0.2%, Sr with a mass percentage of 0-0.1%, and SiC with a mass percentage of 0-35%. The high-strength Al-Zn-Cu series die-casting aluminum alloy has better demolding performance and mechanical properties, and is suitable for manufacturing thin-wall structural members.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and in particular to a high-strength Al-Zn-Cu die-cast aluminum alloy, its preparation method, and structural components. Background Technology

[0002] High-strength Al-Zn die-cast aluminum alloys are a relatively inexpensive casting alloy. The main grades of high-strength Al-Zn die-cast aluminum alloys include ZL401 and ZL402. ZL401 is a quaternary alloy of aluminum, zinc, silicon, and magnesium; ZL402 does not contain silicon and is a ternary alloy of aluminum, zinc, and magnesium. Both grades of high-strength Al-Zn die-cast aluminum alloys increase strength by adding magnesium (Mg). However, the addition of Mg affects the demolding performance of high-strength Al-Zn die-cast aluminum alloys. Specifically, when the Zn content in the aluminum alloy is high, such as 40-55 wt%, Mg easily reacts with Zn to form the MgZn2 phase. The MgZn2 phase actively reacts with the mold steel, leading to sticking to the mold; even the addition of Fe and / or Mn cannot alleviate the sticking caused by the MgZn2 phase. Furthermore, when using Al-Zn die-cast aluminum alloys to manufacture thin-walled structural parts, the mechanical properties decrease sharply.

[0003] Therefore, the market urgently needs an Al-Zn-Cu die-cast aluminum alloy with excellent demolding performance and mechanical properties, which is suitable for manufacturing thin-walled structural parts. Summary of the Invention

[0004] In view of the above-mentioned defects in the prior art, the present invention provides a high-strength Al-Zn-Cu die-cast aluminum alloy, which has excellent mechanical properties and demolding performance, and is suitable for manufacturing thin-walled structural parts.

[0005] This invention provides a high-strength Al-Zn-Cu die-cast aluminum alloy containing Al, and also containing 35-55% Zn, 0.05-1.5% Si, 0.01-3.5% Cu, 0-0.3% Mn, 0-0.2% Zr, 0-0.1% Sr, and 0-35% SiC by mass.

[0006] Furthermore, the high-strength Al-Zn-Cu die-cast aluminum alloy also contains 0.1-1% AlTiB by mass, and at this time, the mass percentage content of SiC is 4-10%.

[0007] Furthermore, at least one of the following conditions must be met:

[0008] The high-strength Al-Zn-Cu series die-casting aluminum alloy further contains Mg, and the mass percentage content of Mg is not more than 0.1%.

[0009] The high-strength Al-Zn-Cu series die-casting aluminum alloy further contains Fe, and the mass percentage content of Fe is 0.001-0.5%.

[0010] Further, the high-strength Al-Zn-Cu series die-casting aluminum alloy further contains at least one of RE, B, Ti, Be, Bi, Cd, Ge, Mo, Nb, Ni, Sb, Te, Sn, In, and AlTiC, wherein the mass percentage content of RE is 0-0.5%, the mass percentage content of B is 0-0.08%, the mass percentage content of Ti is 0-0.3%, 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 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 Sb is 0-0.2%, 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%, and the mass percentage content of AlTiC is 0-0.5%.

[0011] The application further provides a preparation method of the high-strength Al-Zn-Cu series die-casting aluminum alloy, comprising the following steps:

[0012] providing Zn source, Si source, Cu source, Zr source, Sr source, SiC source, and Al source;

[0013] heating the Al source to obtain aluminum liquid;

[0014] adding Zn source, Si source, Cu source, Zr source, Sr source, and SiC source into the aluminum liquid to obtain mixed liquid; and

[0015] performing die-casting treatment and aging treatment on the mixed liquid to obtain the high-strength Al-Zn-Cu series die-casting aluminum alloy, wherein the high-strength Al-Zn-Cu series die-casting aluminum alloy contains Zn with a mass percentage content of 35-55%, Si with a mass percentage content of 0.05-1.5%, Cu with a mass percentage content of 0.01-3.5%, Mn with a mass percentage content of 0-0.3%, Zr with a mass percentage content of 0-0.2%, Sr with a mass percentage content of 0-0.1%, and SiC with a mass percentage content of 0-35%.

[0016] Further, the preparation method of the high-strength Al-Zn-Cu series die-casting aluminum alloy further comprises the step of adding a Mn source into the aluminum liquid, and the mass percentage of Mn is 0.001-0.3%.

[0017] Further, the temperature of the aging treatment is 80-150°C, and the time is 0.05-30h; or

[0018] The aging treatment comprises first-stage aging treatment, second-stage aging treatment, third-stage aging treatment and 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 100-130°C, and the time is 0.5-5h, and the temperature is adjusted to 100-130°C within 1-5min after the second-stage aging treatment; the fourth-stage aging treatment is natural aging treatment or water-cooling aging treatment.

[0019] Further, the preparation method of the high-strength Al-Zn-Cu series die-casting aluminum alloy further comprises the step of adding at least one of AlTiB, RE, B, Ti, Be, Bi, Cd, Ge, Mo, Nb, Ni, Sb, Te, Sn, In and AlTiC into the aluminum liquid, wherein the mass percentage of AlTiB is 0.1-1%, the mass percentage of RE is 0-0.5%, the mass percentage of B is 0-0.08%, the mass percentage of Ti is 0-0.3%, the mass percentage of Be is 0-0.1%, the mass percentage of Bi is 0-0.1%, the mass percentage of Cd is 0-0.2%, the mass percentage of Ge is 0-0.1%, the mass percentage of Mo is 0-0.1%, the mass percentage of Nb is 0-0.1%, the mass percentage of Ni is 0-0.3%, the mass percentage of Sb is 0-0.2%, the mass percentage of Te is 0-0.1%, the mass percentage of Sn is 0-0.1%, the mass percentage of In is 0-0.1%, and the mass percentage of AlTiC is 0-0.5%.

[0020] The application further provides a structural member made of the high-strength Al-Zn-Cu series die-casting aluminum alloy or prepared by the preparation method of the high-strength Al-Zn-Cu series die-casting aluminum alloy.

[0021] Further, the thickness of the structural member is 1.5-15mm.

[0022] The high-strength Al-Zn-Cu series die-casting aluminum alloy contains Zn with a mass percentage of 35-55%, Si with a mass percentage of 0.05-1.5%, Cu with a mass percentage of 0.01-3.5%, Mn with a mass percentage of 0-0.3%, Zr with a mass percentage of 0-0.2%, Sr with a mass percentage of 0-0.1%, and SiC with a mass percentage of 0-35%. The elements with the above contents interact and influence each other, so that the high-strength Al-Zn-Cu series die-casting aluminum alloy has better demolding performance and mechanical properties, and is suitable for manufacturing thin-walled structural parts. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0024] An embodiment of the present application provides a high-strength Al-Zn-Cu series die-casting aluminum alloy, which can be a high-zinc aluminum alloy. The high-strength Al-Zn-Cu series die-casting aluminum alloy has better demolding performance and mechanical properties, and is also suitable for manufacturing thin-walled structural parts, which has better strength, smooth surface and no cracking.

[0025] The thickness of the structural part can 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.

[0026] The high-strength Al-Zn-Cu series die-casting aluminum alloy contains Al, and also contains Zn with a mass percentage of 35-55%, Si with a mass percentage of 0.05-1.5%, Cu with a mass percentage of 0.01-3.5%, Mn with a mass percentage of 0-0.3%, Zr with a mass percentage of 0-0.2%, Sr with a mass percentage of 0-0.1%, and SiC with a mass percentage of 0-35%.

[0027] The mass percentage of Zn can be 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%.

[0028] The mass percent content of Si can specifically be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%.

[0029] The mass percent content of Cu can specifically be 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%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, or 3.5%.

[0030] The mass percent content of Zr can 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%, or 0.2%.

[0031] The mass percent content of Sr can 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%.

[0032] The SiC can be present in an amount of 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%.

[0033] The high-strength Al-Zn-Cu-based die-casting aluminum alloy also contains impurities in a total amount of less than 1%, preferably less than 0.6%, and more preferably less than 0.3%. The aluminum source can be electrolytic aluminum, and can also be other types. The bauxite contains Fe impurities, and when the bauxite is used as a raw material to obtain electrolytic aluminum through electrolysis, the high-strength Al-Zn-Cu-based die-casting aluminum alloy inevitably contains Fe impurities. The Fe impurities can be present in an amount of 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 recycled aluminum is used as the aluminum source, the Fe impurities can be present in an amount of 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%.

[0034] The impurities brought by raw materials or preparation process, especially the impurities brought by the recycled aluminum as raw material, further include Mn and / or Cr. The mass percentage of Mn and Cr can be 0.001-0.3%, and specifically 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%, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%.

[0035] In the die-casting aluminum alloy industry, it is generally believed that the sum of the mass percentages of Fe and Mn, or the sum of the mass percentages of Fe, Mn and Cr is greater than 0.7% to achieve the die-casting aluminum alloy demolding. In the high-strength Al-Zn-Cu series die-casting aluminum alloy of the present application, the addition of ferrous metals (such as Fe, Mn, and Cr) is not required to achieve better demolding performance, wherein Fe, Mn, and Cr come from raw materials. It has been verified by experiments that the combination of Zn and Si within the above content range of the present application can achieve better demolding performance, and the affinity and hot corrosion degree of the steel mold are greatly reduced. In this way, the present application does not need to add at least one of Fe, Mn, and Cr to the aluminum liquid to achieve better demolding performance. Of course, the present application can add a certain amount of Mn to improve the demolding performance.

[0036] The elements and contents in the aluminum alloy can be detected to obtain the Mn content. When the Mn content is too high, the Mn content can be adjusted to 0.001-0.3% by boronizing treatment, or the Mn content can be adjusted to 0.001-0.3% by adding aluminum ingots (such as pure aluminum ingots). When the Mn content is too low, the content can also be adjusted to 0.001-0.3% by adding a Mn source. Of course, the Mn source can also not be added, and the Mn content can be maintained at a lower level.

[0037] In an embodiment, when no Mn raw material is added to the aluminum alloy, the sum of the mass percentages of Fe and Mn in the aluminum alloy of the present application can be less than 0.5%, preferably less than 0.4%, and further preferably 0.3%. In another embodiment, the sum of the mass percentages of Fe, Mn and Cr in the aluminum alloy of the present application can be less than 0.5%, preferably less than 0.4%, and further preferably 0.3%. The mass percentages of Fe, Mn, and Cr in the aluminum alloy can be adjusted by boronizing treatment to make the mass percentages of Fe, Mn, and Cr within an appropriate range.

[0038] In another embodiment, the aluminum alloy can be added with Mn raw material, and the mass percentage of Mn can be 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%, 0.12%, 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%. At this time, the sum of the mass percentages of Fe and Mn can be less than 0.5% or greater than 0.5%. That is, the source of Mn can be Mn impurities in the aluminum source or a Mn source (such as an Al-Mn alloy).

[0039] In the high-strength Al-Zn-Cu series die-casting aluminum alloy of the present application, Mg can not be added, and the alloying element raw material itself contains Mg, and the mass percentage of Mg is not greater than 0.1%, and can be specifically 0.0001%, 0.0002%, 0.0004%, 0.0006%, 0.0008%, 0.001%, 0.002%, 0.004%, 0.006%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. The mass percentage of Mg is low, and even if the content of Zn is high, there is not enough Mg to react with Zn to form enough MgZn2 phase that can affect demolding, so that mold sticking can be avoided. The content of Mg is preferably not greater than 0.01%, and is further preferably not greater than 0.001%, so as to avoid the formation of MgZn2 phase.

[0040] It can be understood that when the high-strength Al-Zn-Cu series die-casting aluminum alloy does not contain Mg or the content of Mg is very low (not greater than 0.1wt%), the ferrous metals Fe, Mn, and Cr can be taken as impurities, and Fe, Mn, or Cr is not added to the aluminum liquid to increase the demolding performance. This is because when the content of Mg is very low, only a small amount of MgZn2 phase is formed, and the small amount of MgZn2 phase does not have obvious adverse effects on demolding. Moreover, it has been verified by experiments that 35-55wt% of Zn and 0.05-1.5wt% of Si can cooperate with each other to bring better demolding performance, and 0-0.1wt% of Mg does not obviously affect the demolding performance of the aluminum alloy, and at least one of Fe, Mn, and Cr does not need to be added to improve the demolding performance.

[0041] The high-strength Al-Zn-Cu series die-casting aluminum alloy contains Zn with a mass percentage of 35-55%, Si with a mass percentage of 0.05-1.5%, Cu with a mass percentage of 0.01-3.5%, Mn with a mass percentage of 0-0.3%, Zr with a mass percentage of 0-0.2%, Sr with a mass percentage of 0-0.1%, and SiC with a mass percentage of 0-35%. The elements with the above contents interact with and affect each other, so that the high-strength Al-Zn-Cu series die-casting aluminum alloy has better demolding performance and mechanical properties, and the thin-walled structural part made of the high-strength Al-Zn-Cu series die-casting aluminum alloy has better surface smoothness and strength. Specifically:

[0042] (1) The mass percentage of Zn is 35-55%, a high content of Zn can be dissolved in the aluminum matrix to greatly improve the strength of the aluminum alloy through solid solution strengthening, and after aging treatment, the precipitated elemental Zn can further improve the strength of the aluminum alloy, so that the Zn content can be increased to avoid the addition of Mg to improve the strength of the aluminum alloy; and the elemental Zn is a non-brittle phase between grain boundaries, which can make the aluminum alloy also have a higher elongation; the Zn in the above content range can improve the fluidity of the aluminum alloy, so that the aluminum alloy is suitable for die casting; the Zn in the above content range can also reduce the solidification temperature of the aluminum alloy, greatly reducing the affinity and thermal corrosion of the aluminum alloy to the mold steel (such as H13 steel), which can improve the service life of the mold; the Zn in the above content range can also increase the eutectic structure of the aluminum alloy, improve the fluidity of the aluminum alloy, and the combined effect of the Zn and SiC refiner can further reduce the solidification interval of the high-zinc aluminum alloy, ensuring that there is no cracking in the thick-thin uneven area of the die casting;

[0043] (2) The mass percentage of Si is 0.05-1.5%, and too high Si content will sharply reduce the elongation of the aluminum alloy, and the Si in the above content range will not significantly reduce the elongation of the aluminum alloy; the Si in the above content range can improve the fluidity of the aluminum alloy and further improve the forming performance of the aluminum alloy; the Si in the above content range can also reduce the deformation amount of the aluminum alloy due to natural aging, thereby increasing the dimensional stability of the aluminum alloy product;

[0044] (3) The mass percentage content of Cu is 0.01-3.5%. The solid solution strengthening of Cu in the aluminum matrix can improve the strength of aluminum alloy; however, when the mass percentage content of Cu is too high, such as greater than 3%, the elongation of aluminum alloy will be drastically reduced. This is because the coarsened Al2Cu phase can weaken the strength between dendrites of the alloy and increase the tendency for cracks to form between dendrites; SiC can refine the grains and inhibit the growth of the second phase, thereby improving the strength of aluminum alloy and the elongation of aluminum alloy. This is also the reason why the Cu content of the present invention can reach 3.5%.

[0045] (4) The mass percentage content of SiC is not greater than 35%. SiC can form a dispersed phase in aluminum alloys and form a strong interfacial bond with the aluminum matrix, thereby effectively improving the strength, elongation, wear resistance, corrosion resistance and thermal stability of the alloy.

[0046] (5) The mass percentage content of Zr is not greater than 0.2%. Zr can improve the strength of aluminum alloys. Zr can also form Al3Zr phase in aluminum alloys. Al3Zr phase can refine grains, second phase and precipitated phase to improve the elongation of aluminum alloys.

[0047] (6) The mass percentage content of Sr is not greater than 0.1%. As a modifier, Sr can change the behavior of intermetallic compound phases in crystallography. It can refine the grains, second phase and precipitated phase by modifying aluminum alloy through heterogeneous nucleation theory or twin valley mechanism, thereby improving the elongation of aluminum alloy. For example, it can refine Al2Cu phase, Mg2Si phase, etc. to reduce the adverse effects when Cu content is high.

[0048] (7) The mass percentage content of Mn is not greater than 0.3%. Mn can form independent Al6Mn and Al6FeMn manganese-rich hardening phases in high-zinc aluminum alloys. The Mn-rich phase is distributed at or near grain boundaries and pins grain boundaries. Although the Mn-rich phase has low coherence with the Al matrix and its size is large, its ability to pin dislocations is weak, the combined addition of Mn and Zr can not only reduce the amount of each alloying element used, but also promote mutual precipitation and form more Al6(Mn,Zr) phase and Al 3( The strengthening effect of Zr,Mn) phase and Al6(FeMnZr) phase is much greater than the strengthening effect of adding Mn or Zr alone.

[0049] The Zn, Si, Cu, Zr, Mn, Sr and SiC in the above content range can cooperate with each other to make the high-strength Al-Zn-Cu series die-casting aluminum alloy of the application have better strength and forming performance, and also have better wear resistance, corrosion resistance, thermal stability and dimensional stability. The strength of the aluminum alloy can be improved without adding too much Mg or without adding Mg, avoiding the demolding difficulty caused by MgZn2 phase. The Zn in the above content range can improve the fluidity of the aluminum alloy, and has low affinity and thermal corrosion degree to mold steel (such as H13 steel), so that the high-strength Al-Zn-Cu series die-casting aluminum alloy of the application is suitable for being made into a thin-walled structural part. The thin-walled structural part made of the high-strength Al-Zn-Cu series die-casting aluminum alloy of the application has better surface smoothness and does not crack.

[0050] The high-strength Al-Zn-Cu series die-casting aluminum alloy also contains 0.1-1% of AlTiB in terms of mass percentage, specifically 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%. When AlTiB and SiC are used in combination, the mass percentage of SiC can be reduced to 4-10%, which can reduce the cost. In a preferred embodiment, the mass percentage of AlTiB is 0.1-0.8% of AlTiB, and the mass percentage of SiC is 5-8%.

[0051] 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 have a tendency to enhance the adhesion energy of the C-TiB2 / Al interface, so that the originally long TiAl3 is broken and shortened, to avoid the enrichment and growth of TiAl3, greatly enhancing the composite refining effect. And through repeated experiments, it has been verified that when the mass percentage of AlTiB is 0.1-0.8% and the mass percentage of SiC is 4-10%, the strength, elongation, wear resistance, corrosion resistance and thermal stability of the aluminum alloy can be greatly improved.

[0052] The high-strength Al-Zn-Cu series die-casting aluminum alloy can further contain RE in a mass percentage of 0-0.5%, 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%. The RE is at least one of La, Ce, Pr, Nd, Er, Sm, Y, Sc, and Gd. The RE can refine the grains, the second phase, and the precipitated phase to improve the elongation of the aluminum alloy; the RE can also promote the precipitation of the strengthening phase and the dispersion phase to further improve the strength of the aluminum alloy; the RE in the above content range can refine the grains, the second phase, and the precipitated phase to improve the strength and elongation of the aluminum alloy.

[0053] The high-strength Al-Zn-Cu series die-casting aluminum alloy can further contain B in a mass percentage of 0-0.08% and Ti in a mass percentage of 0-0.3%. The mass percentage of B can be 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%, or 0.08%. The mass percentage of Ti can be 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%, or 0.3%. B can refine the grains, the second phase, and the precipitated phase to improve the elongation of the aluminum alloy. The boronization of B can also purify the aluminum alloy liquid to further improve the strength and elongation of the aluminum alloy. The mass percentage of Ti is not more than 0.5%, and Ti can refine the grains, the second phase, and the precipitated phase to improve the elongation of the aluminum alloy. B can inhibit the segregation of Ti3Al, and therefore, Ti and B are better when used together.

[0054] The high-strength Al-Zn-Cu series die-casting aluminum alloy can further contain Be in a mass percentage of 0-0.1%. The mass percentage of Be can be 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%. Be can refine Si phase to reduce or eliminate the adverse effect of Si on the performance of the aluminum alloy, thereby improving the strength and elongation of the aluminum alloy.

[0055] The high-strength Al-Zn-Cu series die-casting aluminum alloy further contains Bi in a mass percentage of 0-0.1%. The mass percentage of Bi can be 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%. Bi can reduce the surface tension of the aluminum melt, reduce the contact angle between Al and Si, make it easier for the Si growth front to be inhibited by Al, thereby reducing the size of the eutectic silicon, so that the elongation of the aluminum alloy can be improved.

[0056] The high-strength Al-Zn-Cu series die-casting aluminum alloy can further contain Cd in a mass percentage of 0-0.2%. The mass percentage of Cd can be 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%, or 0.2%. Cd can improve the strength of the aluminum alloy; Cd can also refine grains, second phases, and precipitates to improve the elongation of the aluminum alloy.

[0057] The high-strength Al-Zn-Cu series die-casting aluminum alloy can also contain Ge in a mass percentage of 0-0.1%. The mass percentage of Ge 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%. Ge can react with Al and Si to form second phases such as Al9Ge7, Al6Ge5, Al5Ge2, Al3Ge4, SiGe, etc., to improve the strength of the aluminum alloy; Ge can also refine the grains, second phases, and precipitated phases to improve the elongation of the aluminum alloy; when the high-strength Al-Zn-Cu series die-casting aluminum alloy contains both Ge and RE, the mutual cooperation of Ge and RE can significantly refine the grains, second phases, and precipitated phases, further improving the elongation of the aluminum alloy.

[0058] The high-strength Al-Zn-Cu series die-casting aluminum alloy can also contain Mo in a mass percentage of 0-0.1%. The mass percentage of Mo 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%. Mo can improve the strength of the aluminum alloy; Mo can also refine the grains to improve the elongation of the aluminum alloy.

[0059] The high-strength Al-Zn-Cu series die-casting aluminum alloy can also contain Nb in a mass percentage of 0-0.1%. The mass percentage of Nb 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%. Nb can improve the strength of the aluminum alloy; Nb can also refine the grains, second phases, and precipitated phases to improve the elongation of the aluminum alloy. When the high-strength Al-Zn-Cu series die-casting aluminum alloy contains both Nb and B, strengthening metal compounds such as AlNb3, AlNb, Al3Nb, NbB2, etc. can be formed, significantly improving the strength of the aluminum alloy.

[0060] The high-strength Al-Zn-Cu series die-casting aluminum alloy can also contain Ni in a mass percentage of 0-0.3%. The mass percentage of Ni can be 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%, 0.2%, 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 strength of the aluminum alloy; Ni can also refine the grains, the second phase and the precipitated phase, to improve the elongation of the aluminum alloy.

[0061] The high-strength Al-Zn-Cu series die-casting aluminum alloy can also contain Sb in a mass percentage of 0-0.2%. The mass percentage of Sb can be 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%, or 0.2%. Sb can improve the strength of the aluminum alloy; Sb can also improve the precipitation of Cu, Zn, Ni and other elements in the aluminum alloy matrix, to further improve the strength of the aluminum alloy; Sb can also act as a modifier, which can effectively reduce the size of the eutectic silicon flakes, greatly reducing the possibility of the eutectic silicon flakes cutting the aluminum matrix, to improve the strength and elongation of the aluminum alloy.

[0062] The high-strength Al-Zn-Cu series die-casting aluminum alloy can further contain Te in a mass percentage of 0-0.1%. The mass percentage of Te 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%. Te can modify the eutectic silicon, shorten the length of the eutectic silicon, and improve the elongation of the aluminum alloy; when the high-strength Al-Zn-Cu series die-casting aluminum alloy contains both Sb and Te, fine petal-shaped primary crystals can be formed, further improving the strength and elongation of the aluminum alloy.

[0063] The high-strength Al-Zn-Cu series die-casting aluminum alloy can further contain Sn in a mass percentage of 0-0.1%. The mass percentage of Sn 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%. Sn can improve the strength of the aluminum alloy; Sn can also effectively inhibit the growth of the second phase, promote the dispersion of the second phase, and improve the elongation of the aluminum alloy.

[0064] The high-strength Al-Zn-Cu series die-casting aluminum alloy can further contain In in a mass percentage of 0-0.1%. The mass percentage of In 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%. In can improve the strength of the aluminum alloy; In can also refine the grains, the second phase, and the precipitated phase, and improve the elongation of the aluminum alloy.

[0065] The high-strength Al-Zn-Cu series die-casting aluminum alloy further contains AlTiC in a mass percentage of 0-0.5%, 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%. AlTiC, as a grain refiner, has a particle size of several microns and is not easy to aggregate, and has a better effect of fine-grain strengthening. When AlTiC is combined with RE, the refining effect can be improved, and the elongation of the aluminum alloy can be significantly improved.

[0066] The application further provides a preparation method of the high-strength Al-Zn-Cu series die-casting aluminum alloy.

[0067] The Zn source, the Si source, the Cu source, the Zr source, the Sr source, the SiC source, and the Al source are provided.

[0068] The Al source is subjected to a heating treatment to obtain aluminum liquid.

[0069] The temperature of the aluminum liquid is adjusted to 750-820°C, the Si source is added to the aluminum liquid to obtain a first mixed liquid.

[0070] The temperature of the first mixed liquid is adjusted to 720-740°C, the Zn source, the Cu source, the Zr source, the Sr source, and the SiC source are added to the first mixed liquid to obtain a second mixed liquid.

[0071] The second mixed liquid is subjected to a die-casting treatment to obtain an aluminum alloy roughcast; and

[0072] The aluminum alloy roughcast is subjected to an aging treatment to obtain the high-strength Al-Zn-Cu series die-casting aluminum alloy, wherein the high-strength Al-Zn-Cu series die-casting aluminum alloy contains Zn in a mass percentage of 35-55%, Si in a mass percentage of 0.05-1.5%, Cu in a mass percentage of 0.01-3.5%, Mn in a mass percentage of 0-0.3%, Zr in a mass percentage of 0-0.2%, Sr in a mass percentage of 0-0.1%, and SiC in a mass percentage of 0-35%.

[0073] The Zn source, the Si source, the Cu source, the Zr source, and the Sr source can be aluminum intermediate alloy, and the SiC source can be SiCp / Al-based composite material or intermediate alloy seed.

[0074] Of course, the Mg source can be added to the first mixed solution, or the Mg source can not be added. The elements and contents in the second mixed solution can be tested to determine that the mass percentage of Mg is not greater than 0.1%.

[0075] The elements and contents in the aluminum alloy can be detected to obtain the contents of the elements. When the content of Mn is too high, the content of Mn can be adjusted to 0.001-0.3% by boronizing treatment, or the content of Mn can be adjusted to 0.001-0.3% by adding aluminum ingots (such as pure aluminum ingots). When the content of Mn is too low, the content of Mn can also be adjusted to 0.001-0.3% by adding a Mn source. Of course, the content of Mn can also be maintained at a lower level without adding a Mn source.

[0076] The die casting treatment can be high-pressure casting, the temperature is 590-650ºC, preferably 590-610ºC, the low-speed injection speed is 0.23-0.3m / s, and the high-speed injection speed is 2-2.5m / s. The temperature of the existing die casting aluminum alloy die casting treatment is about 680ºC, which is relatively high. When the mixed solution is placed in the mold at this temperature, the erosion of the mixed solution to the mold is great, which can cause the service life of the mold to be relatively short. The melting point of the Al-Zn-Cu series die casting aluminum alloy of the present application is relatively low, about 590-650ºC, so that the temperature of the die casting treatment of the present application can be set relatively low, the erosion to the mold is relatively small, and the service life of the mold can be improved. The solidification temperature range of the Al-Zn-Cu series die casting aluminum alloy of the present application is very wide, which has excellent die casting performance and is suitable for being made into thin-walled structural parts with complex structure. The η-Zn phase in the Al-Zn-Cu series die casting aluminum alloy of the present application has a close-packed hexagonal lattice structure and has good smearing performance, so that the Al-Zn-Cu series die casting aluminum alloy of the present application has self-lubricating characteristics. Therefore, the Al-Zn-Cu series die casting aluminum alloy of the present application has better forming performance and demolding performance (35-55wt% of Zn and 0.01-1.5wt% of Si phase cooperate), which can be suitable for high-pressure casting forming. The preparation method of the Al-Zn-Cu series die casting aluminum alloy has the advantages of low cost and being suitable for large-scale production. Among them, the mold used in the die casting treatment can be a die casting test mold conforming to the aluminum alloy standard (GB / T13822-2017), and a B-type thin-walled sheet-shaped test sample with a thickness of 1.5-15mm can be made. The surface of the B-type thin-walled sheet-shaped test sample is smooth, and no cracking occurs.

[0077] In an embodiment, the temperature of the aging treatment is 80-150ºC, and the time is 0.05-30h. The temperature of the aging treatment can be specifically 80ºC, 90ºC, 100ºC, 110ºC, 120ºC, 130ºC, 140ºC, or 150ºC, and the time can be specifically 0.05h, 1h, 5h, 10h, 15h, 20h, 25h, or 30h.

[0078] In yet another embodiment, the aging treatment comprises a first stage aging treatment, a second stage aging treatment, a third stage aging treatment, and a fourth stage aging treatment. The first stage aging treatment has a temperature of 40-90°C, specifically 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, or 90°C, and a time of 3-20h, specifically 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, or 20h. The second stage aging treatment has a temperature of -200--100°C, specifically -200°C, -190°C, -180°C, -170°C, -160°C, -150°C, -140°C, -130°C, -120°C, -110°C, or -100°C, and a time of 0.5-10h, specifically 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, or 10h. The third stage aging treatment has a temperature of 100-130°C, specifically 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, or 130°C, and a time of 0.5-5h, specifically 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, or 5h. The first stage aging treatment has a lower temperature, and in the first stage aging treatment, the atoms in the aluminum alloy ingot obtained by die casting are stabilized to stabilize the morphology of the aluminum alloy ingot, while avoiding rapid precipitation of unsaturated Zn. In the second stage aging treatment, the volume rapidly contracts to generate considerable stress, and in turn, a large number of dislocations are generated, which interact with the stress in the alloy, the crystal boundary, and themselves to entangle to improve the strength and plasticity of the alloy. In the process of the second stage aging treatment, the crystal structure of the material changes, and in the process of deep cold recovery, recovery recrystallization occurs to cause the grains to rotate, form a recrystallization texture, and improve the strength of the aluminum alloy. A large number of supersaturated point defects (such as vacancies) and dislocations obtained by the aluminum alloy in the second stage aging treatment can further promote the segregation of solute atoms such as Zn, Mg, Cu, Ni, and Si, significantly improve the GP zone range, increase the nucleation rate in the third stage aging treatment process, and promote the alloy elements to be more fully precipitated. After the second stage aging treatment is completed, the temperature is adjusted to 100-130°C within 1-5min, at which time, the large number of supersaturated point defects (such as vacancies) and dislocations obtained by the aluminum alloy at low temperature are retained, participate in the third stage high-temperature aging under the action of stress and point defects (such as vacancies) and dislocations, and interact with solute atoms to significantly improve the nucleation rate and nucleation speed, refine the precipitated phase, and increase the volume fraction of the precipitated phase, thereby further improving the strength and elongation of the aluminum alloy.

[0079] The aging treatment can further include a fourth stage aging treatment, which can be a natural aging treatment or a water cooling aging treatment. After the fourth stage aging treatment, the elongation of the aluminum alloy is further improved, but the strength is decreased. The natural aging treatment is to place the aluminum alloy billet after the third stage aging treatment at room temperature for 0.5-5h, specifically, 0.5h, 1h, 2h, 3h, 4h, or 5h. The water cooling aging treatment is to place the aluminum alloy billet after the third stage aging treatment in normal temperature water for 0.5-5h, specifically, 0.5h, 1h, 2h, 3h, 4h, or 5h. During the natural aging treatment, the temperature of the aluminum alloy billet decreases rapidly, the fine strengthening phase continues to precipitate but the precipitation rate is also reduced, and the strength and elongation of the aluminum alloy are further improved. During the water cooling aging treatment, the temperature of the aluminum alloy billet decreases more rapidly, the fine strengthening phase continues to precipitate but the precipitation rate is also reduced more rapidly, and the strength and elongation of the aluminum alloy are further improved. The strength and elongation of the aluminum alloy after the water cooling aging treatment are greater than those of the aluminum alloy after the natural aging treatment.

[0080] The aging treatment can further include a fourth stage aging treatment and a fifth stage aging treatment, the fourth stage aging treatment can be a natural aging treatment, and the fifth stage aging treatment can be a water cooling aging treatment. The natural aging treatment is to place the aluminum alloy billet after the third stage aging treatment at room temperature for 0.5-5h, specifically, 0.5h, 1h, 2h, 3h, 4h, or 5h. The water cooling aging treatment is to place the aluminum alloy billet after the natural aging treatment in normal temperature water for 0.5-5h, specifically, 0.5h, 1h, 2h, 3h, 4h, or 5h. During the natural aging treatment, the temperature of the aluminum alloy billet decreases rapidly, the fine strengthening phase continues to precipitate but the precipitation rate is also reduced, and the strength and elongation of the aluminum alloy are further improved. During the water cooling aging treatment, the temperature of the aluminum alloy billet is further decreased, the fine strengthening phase continues to precipitate but the precipitation rate is also further reduced and reduced more rapidly, and the strength and elongation of the aluminum alloy are further improved.

[0081] The Zn, Si, Cu, Zr, Mn, Sr and SiC in the content range above can cooperate with each other to make the high-strength Al-Zn-Cu series die-casting aluminum alloy of the application have better strength and forming performance, and also have better wear resistance, corrosion resistance, thermal stability and dimensional stability. The strength of the aluminum alloy can be improved without adding too much Mg or without adding Mg, thereby avoiding the demolding difficulty caused by MgZn2 phase. The Zn in the content range above can improve the fluidity of the aluminum alloy, and the affinity and thermal corrosion degree of the aluminum alloy to the die steel (such as H13 steel) are low, so that the high-strength Al-Zn-Cu series die-casting aluminum alloy of the application is suitable for being made into a thin-walled structural part. The thin-walled structural part made of the high-strength Al-Zn-Cu series die-casting aluminum alloy of the application has better surface smoothness and does not crack.

[0082] The preparation method of the high-strength Al-Zn-Cu series die-casting aluminum alloy further includes the step of adding at least one of AlTiB source, RE source, B source, Ti source, Ni source, Sb source, Be source, Bi source, Cd source, Ge source, Mo source, Nb source, In source, Te source, Sn source and TiC source to the first mixed solution. The above elements can at least be used to improve the strength and / or elongation of the aluminum alloy, so as to obtain a high-strength Al-Zn-Cu series die-casting aluminum alloy with more excellent performance. The raw materials of the alloying elements can be aluminum intermediate alloy. For example, the TiC source can be AlTiC, and the RE source can be Al-RE alloy.

[0083] Embodiment

[0084] The components and contents of the aluminum alloys of Examples 1 to 10 are shown in Table 1, and the performance test results are shown in Table 2.

[0085] Table 1 Components and contents of the aluminum alloys of Examples 1 to 10 and Comparative Examples 1 to 3

[0086]

[0087] For simplicity, all impurity elements and contents are not shown.

[0088] Table 2 Performance test results of the aluminum alloys of Examples 1 to 10

[0089]

[0090] When the aluminum alloys of Examples 1 to 10 are made into thin-walled structural parts with a thickness of 2 mm, the surface of the structural parts is smooth and no cracking occurs. The tensile strength, yield strength, elongation and fluidity of the thin-walled structural parts are tested. The test results are shown in Table 2.

[0091] Table 2 shows that the aluminum alloys of Examples 1-10 have better tensile strength, yield strength, elongation, and flowability. Specifically, the tensile strength of the aluminum alloys of Examples 1-10 is not less than 460 MPa, the yield strength is not less than 370 MPa, the elongation is not less than 10.3%, and the flowability sample length is not less than 2312 mm.

[0092] The above merely provides the preferred embodiments of the present application, but does not limit the patent scope of the present application. Any equivalent structure transformation based on the content of the present application, or direct / indirect application in other related technical fields, all fall within the patent protection scope of the present application.

Claims

1. A high-strength Al-Zn-Cu-based die-cast aluminum alloy, characterized by, The high-strength Al-Zn-Cu series die-casting aluminum alloy is composed of Zn with a mass percentage of 36-55%, Si with a mass percentage of 0.05-1.5%, Cu with a mass percentage of 0.01-3.5%, Mn with a mass percentage of 0.001-0.15%, Zr with a mass percentage of 0.001-0.2%, Sr with a mass percentage of 0.001-0.1%, Mg with a mass percentage of 0-0.09%, Fe with a mass percentage of 0.001-0.15%, and SiC with a mass percentage of 0-35%, and the balance of Al and other inevitable impurities; wherein the sum of the mass percentages of Fe and Mn is less than 0.3%; the high-strength Al-Zn-Cu series die-casting aluminum alloy is subjected to aging treatment after die-casting treatment, the aging treatment includes first-stage aging treatment, second-stage aging treatment, and third-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 100-130°C, and the time is 0.5-5h, and the temperature is adjusted to 100-130°C within 1-5min after the second-stage aging treatment is completed.

2. The high-strength Al-Zn-Cu-based die-cast aluminum alloy according to claim 1, characterized by, The high-strength Al-Zn-Cu series die-casting aluminum alloy further contains AlTiB with a mass percentage of 0.1-1%, and in this case, the mass percentage of SiC is 4-10%.

3. The high-strength Al-Zn-Cu-based die-cast aluminum alloy according to claim 1, characterized by, The mass percentage of Mg is 0.0001-0.09%.

4. The high-strength Al-Zn-Cu-based die-cast aluminum alloy according to claim 1, characterized by, The high-strength Al-Zn-Cu series die-casting aluminum alloy further contains at least one of RE, B, Ti, Be, Bi, Cd, Ge, Mo, Nb, Ni, Sb, Te, Sn, In, and AlTiC, wherein the mass percentage of RE is 0.001-0.5%, the mass percentage of B is 0.001-0.08%, the mass percentage of Ti is 0.001-0.3%, the mass percentage of Be is 0.001-0.1%, the mass percentage of Bi is 0.001-0.1%, the mass percentage of Cd is 0.001-0.2%, the mass percentage of Ge is 0.001-0.1%, the mass percentage of Mo is 0.001-0.1%, the mass percentage of Nb is 0.001-0.1%, the mass percentage of Ni is 0.001-0.3%, the mass percentage of Sb is 0.001-0.2%, the mass percentage of Te is 0.001-0.1%, the mass percentage of Sn is 0.001-0.1%, the mass percentage of In is 0.001-0.1%, and the mass percentage of AlTiC is 0.001-0.5%.

5. A method for preparing a high-strength Al-Zn-Cu series die-casting aluminum alloy, comprising the following steps: a Zn source, a Si source, a Cu source, a Zr source, a Sr source, and an Al source are provided; the Al source is subjected to a heating treatment to obtain an aluminum liquid; the Zn source, the Si source, the Cu source, the Zr source, and the Sr source are added to the aluminum liquid to obtain a mixed liquid; and the mixed liquid is subjected to a die casting treatment and an aging treatment to obtain the high-strength Al-Zn-Cu series die casting aluminum alloy, wherein the high-strength Al-Zn-Cu series die casting aluminum alloy is composed of Zn with a mass percentage content of 36-55%, Si with a mass percentage content of 0.05-1.5%, Cu with a mass percentage content of 0.01-3.5%, Mn with a mass percentage content of 0.001-0.15%, Zr with a mass percentage content of 0.001-0.2%, Sr with a mass percentage content of 0.001-0.1%, Mg with a mass percentage content of 0-0.09%, and Fe with a mass percentage content of 0.001-0.15%, the balance being Al and other unavoidable impurities; wherein the sum of the mass percentage contents of Fe and Mn is less than 0.3%; 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, 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 100-130°C, and the time is 0.5-5h, and the temperature is adjusted to 100-130°C within 1-5min after the second-stage aging treatment is completed.

6. The production method of the high-strength Al-Zn-Cu-based die-cast aluminum alloy according to claim 5, characterized by, The preparation method of the high-strength Al-Zn-Cu series die casting aluminum alloy further includes a step of adding a SiC source to the aluminum liquid, wherein the mass percentage content of SiC is 0.01-35%.

7. The method of producing a high-strength Al-Zn-Cu-based die-cast aluminum alloy according to claim 5, characterized by, The mass percentage content of Mg is 0.0001-0.09%.

8. The preparation method of the high-strength Al-Zn-Cu series die casting aluminum alloy according to claim 5, characterized in that, the aging treatment further includes a fourth-stage aging treatment, and the fourth-stage aging treatment is a natural aging treatment.

9. The method of producing a high-strength Al-Zn-Cu-based die-cast aluminum alloy according to claim 5, characterized in that, The preparation method of the high-strength Al-Zn-Cu series die-casting aluminum alloy further comprises the step of adding at least one of AlTiB, RE, B, Ti, Be, Bi, Cd, Ge, Mo, Nb, Ni, Sb, Te, Sn, In, and AlTiC into the aluminum liquid, wherein the mass percentage content of AlTiB is 0.1-1%, the mass percentage content of RE is 0.001-0.5%, the mass percentage content of B is 0-0.08%, the mass percentage content of Ti is 0.001-0.3%, the mass percentage content of Be is 0.001-0.1%, the mass percentage content of Bi is 0.001-0.1%, the mass percentage content of Cd is 0.001-0.2%, the mass percentage content of Ge is 0.001-0.1%, the mass percentage content of Mo is 0.001-0.1%, the mass percentage content of Nb is 0.001-0.1%, the mass percentage content of Ni is 0-0.3%, the mass percentage content of Sb is 0.001-0.2%, the mass percentage content of Te is 0.001-0.1%, the mass percentage content of Sn is 0.001-0.1%, the mass percentage content of In is 0.001-0.1%, and the mass percentage content of AlTiC is 0.001-0.5%.

10. A structural member, characterized by The structural member is made of the high-strength Al-Zn-Cu series die-casting aluminum alloy according to any one of claims 1-4, or is made of the high-strength Al-Zn-Cu series die-casting aluminum alloy prepared by the preparation method according to any one of claims 5-9.

11. The structural member of claim 10, wherein The thickness of the structural member is 1.5-15 mm.

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