Al-Zn-Mg-Cu series ultrahigh-strength aluminum alloy as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of aluminum alloy heat treatment, and particularly relates to an Al-Zn-Mg-Cu series ultrahigh-strength aluminum alloy and a preparation method and application thereof. Through multi-stage aging treatment, precipitated phases in the prepared aluminum alloy are uniformly and finely distributed, so that the strength and toughness of the alloy are improved. Particularly, the tensile strength and the yield strength are remarkably improved, and meanwhile, the ductility is also kept at a relatively high level. According to the Al-Zn-Mg-Cu series ultrahigh-strength aluminum alloy prepared through the method, on the premise that the strength performance is not reduced, the plasticity, toughness and corrosion resistance are improved. The L-direction tensile strength of an extruded material prepared from the ultrahigh-strength aluminum alloy reaches 800 MPa or above, the yield strength reaches 770 MPa or above, and the ductility is higher than 8%; the exfoliation corrosion performance reaches EB level, and the conductivity reaches 29.0% IACS or above.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy heat treatment, and specifically relates to an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy and a preparation method and application thereof. Background Art

[0002] Al-Zn-Mg-Cu ultra-high strength aluminum alloys have high strength, low density, good plasticity, toughness and processing performance, and are widely used in aerospace, weapons, nuclear industry, rail transportation and other fields. With the requirements for lightweight structures in the future equipment development, there is a strong demand for ultra-high strength aluminum alloy materials with excellent comprehensive performance. It is urgent to prepare aluminum alloy materials with ultra-high strength, good plasticity and toughness and corrosion resistance through alloy composition design and heat treatment process optimization.

[0003] Al-Zn-Mg-Cu alloy is a heat-treatable strengthening alloy. The strength of aluminum alloy can be significantly improved by uniformly precipitating fine and dispersed strengthening phases from the supersaturated solid solution during the aging process. The aging methods of Al-Zn-Mg-Cu aluminum alloy mainly include single-stage aging, double-stage aging, and regression re-aging processes.

[0004] Regression re-aging is to add a higher temperature regression aging treatment between two lower temperature T6 peak aging treatments. Keeping the alloy in the peak aging state at a higher temperature for a short time can dissolve the precipitated phase in the grain, and the precipitated phase at the grain boundary will coarsen and be discontinuously distributed. Then, another T6 peak aging treatment can make the dissolved solute atoms re-precipitate, and the alloy will restore the T6 peak aging strength. At the same time, the precipitated phase at the grain boundary will be further coarsened, so that the alloy can obtain the strength equivalent to the T6 state and the corrosion performance of the T7x state.

[0005] In order to maintain high strength while obtaining good plasticity, toughness and corrosion resistance, Al-Zn-Mg-Cu ultra-high strength aluminum alloy extrusions need to be regressed and aged. However, the second-stage regression aging process in the prior art has defects, and the regression aging effect is poor, which cannot meet the needs of industrial production and application. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy and a preparation method and application thereof. The present invention specifically includes the following contents:

[0007] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, wherein the solid solution Al-Zn-Mg-Cu series aluminum alloy is subjected to a multi-stage aging treatment according to the following process:

[0008] The solid solution Al-Zn-Mg-Cu super aluminum alloy is kept at 110-120°C for 15-35h for the first stage aging treatment;

[0009] The aluminum alloy after the first stage aging treatment is heated from 110-120°C to 171-190°C at a heating rate of 2-8°C / min, kept at this temperature for 5-100 minutes, and then subjected to the second stage aging treatment;

[0010] The aluminum alloy after the second aging treatment is kept at 110-120°C for 15-35h and then subjected to the third aging treatment.

[0011] Furthermore, the second stage aging treatment: the heating rate is 3-6°C / min, and / or the holding temperature is 171-185°C, and / or the holding time is 10-90min.

[0012] Furthermore, the third stage aging insulation time is 20-30h.

[0013] Furthermore, after the second stage aging treatment is completed, the aluminum alloy is rapidly cooled; after the third stage aging treatment is completed, the aluminum alloy is air-cooled, and finally the Al-Zn-Mg-Cu series ultra-high strength aluminum alloy is obtained.

[0014] Furthermore, the composition of the Al-Zn-Mg-Cu ultra-high strength aluminum alloy includes: Zn 10.0-11.5wt%, Mg 2.5-3.3wt%, Cu 1.0-2.5wt%, Zr 0.08-0.15wt%, Sc 0-0.20wt%, Fe≤0.15wt%, Si≤0.10wt%, other impurities individually ≤0.05wt%, total impurities ≤0.15wt%; the balance is Al.

[0015] Furthermore, the solid solution Al-Zn-Mg-Cu aluminum alloy is obtained by subjecting the Al-Zn-Mg-Cu aluminum alloy to solid solution treatment and pre-stretching treatment.

[0016] Furthermore, the temperature of the solution treatment is 470-477° C., and the solution treatment time is 2-8 hours; and / or, after the solution treatment, the aluminum alloy is water quenched and pre-stretched, and the pre-stretching amount is controlled to be 1.0-3.0%.

[0017] An Al-Zn-Mg-Cu series ultra-high strength aluminum alloy prepared by the method.

[0018] The Al-Zn-Mg-Cu series ultra-high strength aluminum alloy is used in the fields of aerospace, weapons, etc.

[0019] Beneficial effects of the present invention:

[0020] Aging is the process of placing the aluminum alloy after solid solution treatment at room temperature (natural aging) or artificial heating conditions to decompose the supersaturated matrix and precipitate the solute atom aggregation zone (GP zone) and precipitation phase (precipitation phase). In Al-Zn-Mg-Cu alloy, the precipitation sequence of precipitation phase is generally: supersaturated solid solution (SSSS) → GP zone → transition phase (such as η') → ​​equilibrium phase (such as η). Through aging treatment, the microstructure of the alloy can be optimized, thereby improving its mechanical properties. The method described in the present invention adopts a multi-stage aging treatment process, and the process of each stage is designed and improved: wherein, the first stage aging treatment (110-120℃, 15-35h) promotes the initial precipitation of some strengthening phases, such as GP zone, and these precipitation phases can improve the strength and hardness of the alloy. At the same time, the first stage aging also provides a good organizational basis for subsequent regression aging. The second aging treatment (heating rate of 2-8℃ / min, heating from 110-120℃ to 171-190℃, and heat preservation for 5-100min) is a key step. By controlling the heating rate and heat preservation conditions, the grain boundary precipitation phase precipitated in the first aging is coarsened and the intragranular precipitation phase is partially dissolved. Regression aging helps to adjust the microstructure of the alloy, such as reducing the continuity of the grain boundary precipitation phase, thereby reducing the sensitivity of the alloy to stress corrosion cracking. The third aging treatment (110-120℃, 15-35h) promotes further precipitation of the intragranular precipitation phase, while the grain boundary precipitation phase remains discontinuously distributed, improving the strength and corrosion resistance of the alloy. At the same time, the third aging also helps to eliminate the thermal stress that may be generated during the cooling process of the second aging, thereby maintaining the good toughness of the alloy. The preparation method of the aluminum alloy disclosed in the present invention is suitable for Al-Zn-Mg-Cu series ultra-high strength aluminum alloys. The regression aging process of the present invention adopts furnace heating, lower regression temperature and longer insulation time, which can achieve good regression aging effect of the alloy.

[0021] The method of the present invention uses multi-stage aging treatment to evenly and finely distribute the precipitated phase in the aluminum alloy prepared by the method, thereby improving the strength and toughness of the alloy. In particular, the tensile strength and yield strength are significantly improved, while the elongation is also maintained at a high level. Moreover, the multi-stage aging treatment helps to reduce the continuity of the grain boundary precipitated phase, thereby reducing the sensitivity of the alloy to stress corrosion cracking and exfoliation corrosion. Therefore, the corrosion resistance of the alloy is significantly improved. In addition, the formation and evolution of the precipitated phase during the aging treatment also have a certain effect on the electrical conductivity of the alloy. The multi-stage aging treatment optimizes the distribution and morphology of the precipitated phase, so that the electrical conductivity of the alloy is maintained at a high level. The Al-Zn-Mg-Cu ultra-high strength aluminum alloy prepared by the method of the present invention has improved plasticity, toughness and corrosion resistance while maintaining the strength performance. The extruded material prepared by using the ultra-high strength aluminum alloy of the present invention has an L-direction tensile strength of more than 800 MPa, a yield strength of more than 770 MPa, and an elongation of more than 8%; the exfoliation corrosion performance reaches EB level, and the electrical conductivity reaches more than 29.0% IACS. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process schematic diagram of the method of the present invention;

[0023] Figure 2 This is a microstructure diagram of the Al-Zn-Mg-Cu aluminum alloy after solid solution according to the present invention;

[0024] Figure 3 This is a morphology diagram of the precipitation phase of the Al-Zn-Mg-Cu aluminum alloy after aging according to the present invention;

[0025] Figure 4 This is the morphology of the precipitation phase after aging of the alloy described in Comparative Example 2;

[0026] Figure 5 This is a morphology of the alloy in Comparative Example 3 after solution treatment at 480°C and the structure is over-burned;

[0027] Figure 6 This is a morphology diagram of the precipitation phase in the alloy described in Comparative Example 5. DETAILED DESCRIPTION

[0028] The following is combined with Figure 1-6 The present invention is described in detail with specific embodiments. The embodiments shown below do not limit the invention described in the claims. In addition, the entire contents of the configurations shown in the following embodiments are not limited to the solutions required as the invention described in the claims.

[0029] Reference Figure 1, a method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, wherein the Al-Zn-Mg-Cu series aluminum alloy comprises: Zn 10.0-11.5wt%, Mg 2.5-3.3wt%, Cu1.0-2.5wt%, Zr 0.08-0.15wt%, Sc 0-0.20wt%, Fe≤0.15wt%, Si≤0.10wt%, other impurities individually ≤0.05wt%, total impurities ≤0.15wt%; the balance is Al; the method comprises the following steps:

[0030] (1) Solution treatment: The Al-Zn-Mg-Cu aluminum alloy is subjected to solution treatment at a temperature of 470-477°C and a solution treatment time of 2-8 hours;

[0031] (2) Pre-stretching: The aluminum alloy after solution treatment is water quenched and pre-stretched, and the pre-stretching amount is controlled to be 1.0-3.0%;

[0032] (3) Multi-stage aging treatment: The pre-stretched solid solution Al-Zn-Mg-Cu super aluminum alloy is kept at 110-120°C for 20-30 hours for the first stage aging treatment; the aluminum alloy after the first stage aging treatment is heated from 110-120°C to 171-190°C at a heating rate of 2-8°C / min, kept for 5-100 minutes, and then subjected to the second stage aging treatment; the aluminum alloy after the second stage aging treatment is rapidly cooled to 110-120°C and kept for 15-35 hours, and then subjected to the third stage aging treatment. After air cooling, the Al-Zn-Mg-Cu super high strength aluminum alloy is obtained.

[0033] The second-stage aging treatment: the heating rate is 3-6°C / min, the insulation temperature is 171-185°C, and the insulation time is 10-90min; the insulation time of the third-stage aging is 20-30h.

[0034] Experimental verification shows that the extruded material prepared by the ultra-high strength aluminum alloy of the present invention has an L-direction tensile strength of more than 800 MPa, a yield strength of more than 770 MPa, and an elongation of more than 8%; the exfoliation corrosion performance reaches EB level, and the electrical conductivity reaches more than 29.0% IACS.

[0035] Example 1

[0036] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0037] The alloy mass ratio (the same below) is Zn: 10.0%, Mg: 2.5%, Cu: 1.5%, Zr: 0.08%, Fe: 0.08%, Si: 0.06%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0038] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0039] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0040] The extruded material was subjected to solution treatment at a solution temperature of 470°C, a holding time of 8h, and water quenching;

[0041] After quenching, pre-stretching is performed with a stretching amount of 1.5%;

[0042] The extruded materials were subjected to multi-stage aging treatment. The extruded materials were kept at 110°C for 30 hours, then raised to 171°C at a rate of 2°C / min, kept for 100 minutes, and quickly cooled; the extruded materials were kept at 110°C for 35 hours as the furnace was heated, and then air-cooled.

[0043] After aging treatment, the tensile strength of the extruded material in the L direction is 805MPa, the yield strength is 772MPa, the elongation is 9.5%, the electrical conductivity is 29.5%IACS, and the exfoliation corrosion is EB grade.

[0044] Example 2

[0045] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0046] The alloy ratio is Zn: 10.5%, Mg: 2.7%, Cu: 1.8%, Zr: 0.10%, Fe: 0.10%, Si: 0.07%, Sc: 0.05%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0047] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0048] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0049] The extruded material was subjected to solution treatment at a solution temperature of 473°C, a holding time of 6 h, and water quenching;

[0050] After quenching, pre-stretching is performed with a stretching amount of 1.7%;

[0051] The extruded materials were subjected to multi-stage aging treatment. The extruded materials were kept at 115°C for 24 hours, then raised to 173°C at a rate of 4°C / min, kept for 80 minutes, and quickly cooled; the extruded materials were kept at 115°C for 30 hours as the furnace was heated, and then air-cooled.

[0052] After aging treatment, the tensile strength of the extruded material in the L direction is 810MPa, the yield strength is 780MPa, the elongation is 9.0%, the electrical conductivity is 29.8%IACS, and the exfoliation corrosion is EB grade.

[0053] Example 3

[0054] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0055] The alloy ratio is Zn: 11.0%, Mg: 3.0%, Cu: 2.0%, Zr: 0.12%, Fe: 0.08%, Si: 0.06%, Sc: 0.10%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0056] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0057] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0058] The extruded material was subjected to solution treatment at a solution temperature of 475°C, a holding time of 4h, and water quenching;

[0059] After quenching, pre-stretching is performed with a stretching amount of 2.0%;

[0060] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 120°C for 20 hours; then the temperature was raised to 175°C at a rate of 6°C / min, kept for 50 minutes, and quickly cooled; the extruded material was kept at 120°C for 20 hours and air-cooled.

[0061] After aging treatment, the tensile strength of the extruded material in the L direction is 815MPa, the yield strength is 786MPa, the elongation is 8.8%, the electrical conductivity is 30.2%IACS, and the exfoliation corrosion is EB grade.

[0062] Example 4

[0063] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0064] The alloy ratio is Zn: 11.5%, Mg: 3.2%, Cu: 1.2%, Zr: 0.10%, Fe: 0.09%, Si: 0.05%, Sc: 0.15%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0065] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0066] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0067] The extruded material was subjected to solution treatment at a solution temperature of 477°C, a holding time of 4h, and water quenching;

[0068] After quenching, pre-stretching is performed with a stretching amount of 2.2%;

[0069] The extruded material is subjected to multi-stage aging treatment. The extruded material is kept at 120°C for 24 hours; then the temperature is raised to 180°C at a rate of 5°C / min, kept for 30 minutes, and quickly cooled; the extruded material is kept at 120°C for 24 hours and air-cooled.

[0070] After aging treatment, the tensile strength of the extruded material in the L direction is 820MPa, the yield strength is 799MPa, the elongation is 8.5%, the electrical conductivity is 30.7%IACS, and the exfoliation corrosion is EB grade.

[0071] Example 5

[0072] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0073] The alloy ratio is Zn: 11.0%, Mg: 3.0%, Cu: 2.2%, Zr: 0.10%, Fe: 0.08%, Si: 0.06%, Sc: 0.20%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0074] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0075] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0076] The extruded material was subjected to solution treatment at a solution temperature of 475°C, a holding time of 6 h, and water quenching;

[0077] After quenching, pre-stretching is performed with a stretching amount of 2.5%;

[0078] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 110°C for 28 hours; then the temperature was raised to 185°C at a rate of 6°C / min, kept for 15 minutes, and quickly cooled; the extruded material was kept at 110°C for 28 hours and air-cooled.

[0079] After aging treatment, the tensile strength of the extruded material in L direction is 815MPa, the yield strength is 795MPa, the elongation is 9.0%, the electrical conductivity is 31.5%IACS, and the exfoliation corrosion is EB grade.

[0080] Example 6

[0081] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0082] The alloy ratio is Zn: 10.7%, Mg: 2.9%, Cu: 1.4%, Zr: 0.10%, Fe: 0.10%, Si: 0.08%, Sc: 0.07%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0083] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0084] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0085] The extruded material was subjected to solution treatment at a solution temperature of 473°C, a holding time of 8h, and water quenching;

[0086] After quenching, pre-stretching is performed with a stretching amount of 2.3%;

[0087] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 120°C for 30 hours; then the temperature was raised to 190°C at a rate of 8°C / min, kept for 5 minutes, and quickly cooled; the extruded material was kept at 120°C for 15 hours and air-cooled.

[0088] After aging treatment, the tensile strength of the extruded material in the L direction is 810MPa, the yield strength is 785MPa, the elongation is 9.5%, the electrical conductivity is 30.8%IACS, and the exfoliation corrosion is EB grade.

[0089] Example 7

[0090] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0091] The alloy ratio is Zn: 10.8%, Mg: 2.8%, Cu: 1.7%, Zr: 0.10%, Fe: 0.10%, Si: 0.08%, Sc: 0.12%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0092] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0093] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0094] The extruded material was subjected to solution treatment at a solution temperature of 474°C, a holding time of 6 h, and water quenching;

[0095] After quenching, pre-stretching is performed with a stretching amount of 2.0%;

[0096] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 110°C for 30 hours; then the temperature was raised to 175°C at a rate of 4°C / min, kept for 40 minutes, and quickly cooled; the extruded material was kept at 115°C for 24 hours and air-cooled.

[0097] After aging treatment, the tensile strength of the extruded material in the L direction is 808MPa, the yield strength is 780MPa, the elongation is 9.0%, the electrical conductivity is 30.5%IACS, and the exfoliation corrosion is EB grade.

[0098] Example 8

[0099] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0100] The alloy ratio is Zn: 11.2%, Mg: 2.6%, Cu: 2.0%, Zr: 0.12%, Fe: 0.09%, Si: 0.07%, Sc: 0.08%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0101] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0102] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0103] The extruded material was subjected to solution treatment at a solution temperature of 476°C, a holding time of 4h, and water quenching;

[0104] After quenching, pre-stretching is performed with a stretching amount of 2.0%;

[0105] The extruded materials were subjected to multi-stage aging treatment. The extruded materials were kept at 115°C for 30 hours; then the temperature was raised to 180°C at a rate of 6°C / min, kept for 20 minutes, and quickly cooled; the extruded materials were kept at 120°C for 20 hours and air-cooled.

[0106] After aging treatment, the tensile strength of the extruded material in the L direction is 805MPa, the yield strength is 775MPa, the elongation is 9.5%, the electrical conductivity is 29.8%IACS, and the exfoliation corrosion is EB grade.

[0107] Example 9

[0108] A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, the process steps are as follows:

[0109] The alloy ratio is Zn: 10.0%, Mg: 2.9%, Cu: 1.6%, Zr: 0.10%, Fe: 0.10%, Si: 0.08%, Sc: 0.10%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy, Al-Sc master alloy are used;

[0110] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0111] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0112] The extruded material was subjected to solution treatment at a solution temperature of 475°C, a holding time of 5 h, and water quenching;

[0113] After quenching, pre-stretching is performed with a stretching amount of 1.8%;

[0114] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 118°C for 24 hours; then the temperature was raised to 185°C at a rate of 5°C / min, kept for 10 minutes, and quickly cooled; the extruded material was kept at 115°C for 24 hours and air-cooled.

[0115] After aging treatment, the tensile strength of the extruded material in L direction is 812MPa, the yield strength is 784MPa, the elongation is 9.0%, the electrical conductivity is 30.2%IACS, and the exfoliation corrosion is EB grade.

[0116] After the alloy extrusion material described in this article has been subjected to solution and aging treatment, the coarse second phase in the structure is fully dissolved without over-burning, the precipitation phase in the crystal is fine and dispersed, and the precipitation phase at the grain boundary is discontinuously distributed. Therefore, the alloy extrusion material has high strength and good corrosion resistance.

[0117] Comparative Example 1

[0118] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0119] The alloy ratio is Zn: 9.5%, Mg: 2.4%, Cu: 1.2%, Zr: 0.08%, Fe: 0.08%, Si: 0.06%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0120] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0121] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0122] The extruded material was subjected to solution treatment at a solution temperature of 468°C, a holding time of 4h, and water quenching;

[0123] After quenching, pre-stretching is performed with a stretching amount of 2.0%;

[0124] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 110°C for 20 hours; the temperature was raised to 165°C at a rate of 3°C / min, kept for 130 minutes, and quickly cooled; the extruded material was kept at 110°C for 20 hours and air-cooled.

[0125] After aging treatment, the tensile strength of the extruded material in the L direction is 780MPa, the yield strength is 765MPa, the elongation is 10.0%, the electrical conductivity is 33.0%IACS, and the exfoliation corrosion is EB grade.

[0126] Comparative Example 2

[0127] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0128] The alloy ratio is Zn: 9.0%, Mg: 2.6%, Cu: 0.9%, Zr: 0.10%, Fe: 0.07%, Si: 0.05%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0129] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0130] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0131] The extruded material was subjected to solution treatment at a solution temperature of 470°C, a holding time of 4h, and water quenching;

[0132] After quenching, pre-stretching is performed with a stretching amount of 1.7%;

[0133] The extruded material was subjected to multi-stage aging treatment: the extruded material was kept at 130°C for 20 hours; the temperature was raised to 175°C at a rate of 1°C / min, kept for 110 minutes, and quickly cooled; the extruded material was kept at 130°C for 20 hours and air-cooled.

[0134] After aging treatment, the tensile strength of the extruded material in the L direction is 770MPa, the yield strength is 750MPa, the elongation is 10.5%, the electrical conductivity is 35.0%IACS, and the exfoliation corrosion is EB grade.

[0135] Comparative Example 3

[0136] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0137] The alloy ratio is Zn: 11.5%, Mg: 3.5%, Cu: 2.5%, Zr: 0.10%, Fe: 0.07%, Si: 0.05%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0138] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0139] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0140] The extruded material was subjected to solution treatment at a solution temperature of 480°C, a holding time of 4h, and water quenching;

[0141] After quenching, pre-stretching is performed with a stretching amount of 1.5%;

[0142] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 120°C for 20 hours; the temperature was raised to 180°C at a rate of 5°C / min, kept for 80 minutes, and quickly cooled; the extruded material was kept at 120°C for 20 hours and air-cooled.

[0143] After aging treatment, the tensile strength of the extruded material in the L direction is 790MPa, the yield strength is 768MPa, the elongation is 5.5%, the conductivity is 35.6%IACS, and the exfoliation corrosion is EB grade. The extruded material structure is over-burned.

[0144] Comparative Example 4

[0145] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0146] The alloy ratio is Zn: 11.0%, Mg: 3.0%, Cu: 2.0%, Zr: 0.10%, Fe: 0.07%, Si: 0.05%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0147] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0148] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0149] The extruded material was subjected to solution treatment at a solution temperature of 475°C, a holding time of 6 h, and water quenching;

[0150] After quenching, pre-stretching is performed with a stretching amount of 1.8%;

[0151] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 120°C for 20 hours; then the temperature was raised to 185°C at a rate of 1°C / min, kept for 50 minutes, and quickly cooled; the extruded material was kept at 120°C for 20 hours and air-cooled.

[0152] After aging treatment, the tensile strength of the extruded material in the L direction is 750MPa, the yield strength is 732MPa, the elongation is 10.8%, the electrical conductivity is 36.5%IACS, and the exfoliation corrosion is EB grade.

[0153] Comparative Example 5

[0154] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0155] The alloy ratio is Zn: 11.0%, Mg: 2.8%, Cu: 1.5%, Zr: 0.10%, Fe: 0.07%, Si: 0.05%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0156] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0157] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0158] The extruded material was subjected to solution treatment at a solution temperature of 475°C, a holding time of 4h, and water quenching;

[0159] After quenching, pre-stretching is performed with a stretching amount of 1.3%;

[0160] The extruded materials were subjected to multi-stage aging treatment. The extruded materials were kept at 110°C for 30 hours; the temperature was raised to 175°C at a rate of 10°C / min, kept for 5 minutes, and quickly cooled; the extruded materials were kept at 120°C for 20 hours and air-cooled.

[0161] After aging treatment, the tensile strength of the extruded material in the L direction is 818MPa, the yield strength is 790MPa, the elongation is 7.2%, the electrical conductivity is 28.3%IACS, and the exfoliation corrosion is EC grade.

[0162] Comparative Example 6

[0163] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0164] The alloy ratio is Zn: 10.8%, Mg: 2.7%, Cu: 1.6%, Zr: 0.11%, Fe: 0.09%, Si: 0.06%, Sc: 0.08%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0165] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0166] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0167] The extruded material was subjected to solution treatment at a solution temperature of 475°C, a holding time of 4h, and water quenching;

[0168] After quenching, pre-stretching is performed with a stretching amount of 1.7%;

[0169] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 110°C for 24 hours; the temperature was raised to 168°C at a rate of 10°C / min, kept for 30 minutes, and quickly cooled; the extruded material was kept at 110°C for 30 hours and air-cooled.

[0170] After aging treatment, the tensile strength of the extruded material in L direction is 812MPa, the yield strength is 784MPa, the elongation is 7.5%, the electrical conductivity is 28.5%IACS, and the exfoliation corrosion is EC grade.

[0171] Comparative Example 7

[0172] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0173] The alloy ratio is Zn: 11.2%, Mg: 2.9%, Cu: 1.8%, Zr: 0.10%, Fe: 0.10%, Si: 0.07%, Sc: 0.07%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0174] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0175] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0176] The extruded material was subjected to solution treatment at a solution temperature of 477°C, a holding time of 4h, and water quenching;

[0177] After quenching, pre-stretching is performed with a stretching amount of 1.7%;

[0178] The extruded material was subjected to multi-stage aging treatment. The extruded material was kept at 120°C for 10 hours; the temperature was raised to 175°C at a rate of 10°C / min, kept for 40 minutes, and quickly cooled; the extruded material was kept at 110°C for 10 hours and air-cooled.

[0179] After aging treatment, the tensile strength of the extruded material in L direction is 796MPa, the yield strength is 768MPa, the elongation is 10.0%, the electrical conductivity is 28.5%IACS, and the exfoliation corrosion is EC grade.

[0180] Comparative Example 8

[0181] The preparation process steps of the aluminum alloy of this comparative example are as follows:

[0182] The alloy ratio is Zn: 10.8%, Mg: 2.6%, Cu: 1.7%, Zr: 0.12%, Fe: 0.08%, Si: 0.06%, Sc: 0.05%; according to the above weight percentage, 99.9% high-purity aluminum, pure zinc ingot, pure magnesium ingot, Al-Cu master alloy, Al-Zr master alloy are used;

[0183] The casting yields a semi-continuous ingot with an ingot size of φ200 mm;

[0184] The ingot is homogenized and extruded into rods with a diameter of 30 to 60 mm;

[0185] The extruded material was subjected to solution treatment at a solution temperature of 475°C, a holding time of 4h, and water quenching;

[0186] After quenching, pre-stretching is performed with a stretching amount of 1.7%;

[0187] The extruded materials were subjected to multi-stage aging treatment. The extruded materials were kept at 120°C for 35 hours; the temperature was raised to 180°C at a rate of 10°C / min, kept for 30 minutes, and quickly cooled; the extruded materials were kept at 110°C for 40 hours and air-cooled.

[0188] After aging treatment, the tensile strength of the extruded material in the L direction is 799MPa, the yield strength is 774MPa, the elongation is 8.8%, the electrical conductivity is 30.3%IACS, and the exfoliation corrosion is EB grade.

[0189] After the extruded material in Example 1-9 is solution treated, the second phase in the structure is fully dissolved. Figure 2 As shown in the figure, the precipitated phase in the crystal is finely dispersed, and the grain boundary phase is discontinuously distributed, such as Figure 3 shown.

[0190] In Comparative Example 1, the Mg content is lower than the required 2.5%, the solution temperature is lower than the required range, and the second aging time exceeds the specified range. The second phase in the final microstructure of the extruded material is not completely dissolved, and a certain degree of overaging occurs, and the tensile strength of the profile is lower than 800 MPa.

[0191] In Comparative Example 2, the Zn content is lower than the required 10.0%, and the Cu content is also lower than the required 1.0%. The second-stage aging holding time is too long, over-aging occurs, and the precipitate phase is obviously coarsened. Figure 4 As shown in the figure, the strength of the profile is less than 800MPa.

[0192] In Comparative Example 3, the alloy composition is within the specified range, but the solution temperature is too high at 480°C, exceeding the specified range, and the structure will be over-burned. Figure 5 As shown; and the second-stage aging insulation time is too long, the strength of the extruded material is lower than 800MPa, and the elongation is also reduced due to over-burning.

[0193] In Comparative Example 4, the alloy composition and solution treatment process are within the required range, but the second-stage aging and heat preservation time is too long. The corrosion resistance of the extruded material is good, but the strength is significantly lower than 800 MPa.

[0194] In Comparative Examples 5 and 6, the alloy composition, solution quenching, and pre-stretching process are all within the required range, but the second-stage aging holding time is too short or the holding temperature is too low, the dissolution of the intragranular precipitate phase and the coarsening of the grain boundary precipitate phase are not obvious, and the peak aging state is basically maintained. Figure 6 Therefore, the alloy has higher strength after aging, but poorer corrosion resistance.

[0195] In Comparative Example 7, the alloy composition, solution quenching, and pre-stretching process are all within the required range, but the first and second aging holding times are too short, the intracrystalline precipitate phase cannot be fully precipitated, the peak aging state is not reached, and the alloy strength is low.

[0196] In Comparative Example 8, the alloy composition, solution quenching, and pre-stretching process are all within the required range, but the first and second aging holding times are too long, the intragranular precipitation phase coarsens, the alloy is over-aged, and the strength is low.

[0197] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy, characterized in that: The Al-Zn-Mg-Cu series ultra-high strength aluminum alloy comprises: Zn 10.0-11.5wt%, Mg 2.5-3.3wt%, Cu 1.0-2.5wt%, Zr0.08-0.15wt%, Sc 0-0.20wt%, Fe≤0.15wt%, Si≤0.10wt%, other impurities individually≤0.05wt%, total impurities≤0.15wt%; the balance is Al; The preparation method comprises subjecting the Al-Zn-Mg-Cu aluminum alloy in a solid solution state after solid solution treatment at a temperature of 470-477° C. to a multi-stage aging treatment according to the following process: The solid solution Al-Zn-Mg-Cu super aluminum alloy is kept at 110-120°C for 20-30 hours for the first stage aging treatment; The aluminum alloy after the first stage aging treatment is heated from 110-120°C to 171-190°C at a heating rate of 2-8°C / min, kept at this temperature for 5-100 minutes, and then subjected to the second stage aging treatment; The aluminum alloy after the second aging treatment is kept at 110-120°C for 15-35h and then subjected to the third aging treatment.

2. The method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy according to claim 1, characterized in that: The second stage aging treatment: the heating rate is 3-6°C / min, and / or the holding temperature is 171-185°C, and / or the holding time is 10-90min.

3. The method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy according to claim 2, characterized in that: The third-level aging insulation time is 20-30h.

4. The method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy according to claim 1, characterized in that: After the second stage aging treatment, the aluminum alloy is quickly cooled; after the third stage aging treatment, the aluminum alloy is air-cooled to finally obtain the Al-Zn-Mg-Cu series ultra-high strength aluminum alloy.

5. The method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy according to any one of claims 1 to 4, characterized in that: The solid solution Al-Zn-Mg-Cu aluminum alloy is obtained by subjecting the Al-Zn-Mg-Cu aluminum alloy to solid solution treatment and pre-stretching treatment.

6. The method for preparing an Al-Zn-Mg-Cu series ultra-high strength aluminum alloy according to claim 5, characterized in that: The solution treatment time is 2-8 hours; and / or, after the solution treatment, the aluminum alloy is water quenched and pre-stretched, and the pre-stretching amount is controlled to be 1.0-3.0%.

7. An Al-Zn-Mg-Cu series ultra-high strength aluminum alloy prepared by the method according to any one of claims 1 to 6.

8. Application of the Al-Zn-Mg-Cu ultra-high strength aluminum alloy according to claim 7 in the fields of aerospace and weapons.

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