A method of heat treatment of an Al-Zn-Mg-Cu alloy

Abstract

The application relates to a heat treatment method of an Al-Zn-Mg-Cu alloy and relates to the technical field of aluminum alloys and aluminum alloy heat treatment. The main technical scheme is as follows: the heat treatment method of the Al-Zn-Mg-Cu alloy comprises the following steps: solid solution treatment is conducted on the Al-Zn-Mg-Cu alloy to obtain the Al-Zn-Mg-Cu alloy after solid solution treatment; stress aging treatment is conducted on the Al-Zn-Mg-Cu alloy after the solid solution treatment under an external stress field and a thermal field to obtain the Al-Zn-Mg-Cu alloy after the stress aging treatment; artificial aging treatment is conducted on the Al-Zn-Mg-Cu alloy after the stress aging treatment to obtain the Al-Zn-Mg-Cu alloy after the heat treatment. The heat treatment technology can realize the synergistic promotion of the strength, plasticity and corrosion resistance of the Al-Zn-Mg-Cu alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy and aluminum alloy heat treatment, in particular to a heat treatment method of Al-Zn-Mg-Cu alloy. BACKGROUND

[0002] With the continuous development of high-end equipment for national defense, aviation and transportation, there is an urgent need for lightweight and high comprehensive performance components. Al-Zn-Mg-Cu alloy components are increasingly widely used in the above-mentioned fields due to their high mechanical properties. In particular, the tensile strength of Al-Zn-Mg-Cu alloy materials with high Zn content has gradually increased to more than 700 MPa. Increasing the Zn content to obtain ultra-high strength has become the mainstream direction of the development of this series of aluminum alloys. However, as equipment expands to diverse service environments, high humidity, warm conditions and other conditions require corrosion resistance of components.

[0003] For Al-Zn-Mg-Cu alloy with Zn content greater than 8wt%, a large number of fine and dispersed MgZn2 precipitates in the grain after T6 heat treatment, effectively improving the tensile strength and yield strength of the matrix. However, a large amount of Zn element will also lead to the formation of coarse continuous intergranular phase and form a non-precipitation zone around the grain boundary. This composite microstructure composed of large-size intergranular phase-non-precipitation zone-matrix shows large differences in electrochemical properties, resulting in poor corrosion resistance of the material. At the same time, the inhomogeneous grain boundary-grain microstructure affects the further improvement of the strength and plasticity of the matrix. Ultimately, the composition optimization effect is not fully reflected in the mechanical properties.

[0004] Therefore, how to optimize the heat treatment process and effectively control the intragranular and intergranular precipitate characteristics of high-Zn aluminum alloy is the key to achieving the synergistic improvement of the strength, plasticity and corrosion resistance of such components. Related researchers have proposed a T77 process of pre-aging, over-aging and re-aging around this problem. Although the T77 process can optimize the corrosion resistance, the process has poor effect on eliminating the non-precipitation zone and limited effect on improving the strength and plasticity of the matrix. At the same time, in batch production, it is difficult to accurately control the heating rate, time and other parameters of low-temperature pre-aging to high-temperature over-aging, and the application is limited.

[0005] In summary, there is an urgent need for a new heat treatment technology to achieve the synergistic improvement of the strength, plasticity and corrosion resistance of Al-Zn-Mg-Cu alloy. SUMMARY

[0006] In view of this, the present application provides a heat treatment method of Al-Zn-Mg-Cu alloy, mainly aiming to improve the strength, plasticity and corrosion resistance of Al-Zn-Mg-Cu alloy.

[0007] To achieve the above object, the present application mainly provides the following technical solutions:

[0008] In one aspect, the present application provides a heat treatment method of Al-Zn-Mg-Cu alloy, comprising the following steps:

[0009] solution treatment: solution treating the Al-Zn-Mg-Cu alloy to obtain the Al-Zn-Mg-Cu alloy after solution treatment;

[0010] stress aging treatment: stress aging treating the Al-Zn-Mg-Cu alloy after solution treatment under an applied stress field and a thermal field to obtain the Al-Zn-Mg-Cu alloy after stress aging treatment;

[0011] artificial aging treatment: artificial aging treating the Al-Zn-Mg-Cu alloy after stress aging treatment to obtain the Al-Zn-Mg-Cu alloy after heat treatment.

[0012] Preferably, the chemical composition of the Al-Zn-Mg-Cu alloy includes, in terms of weight percentage, Zn 9.5-10.5wt%, Mg 2.5-3.5wt%, Cu 1.5-2.5wt%, Zr 0.05-0.15wt%, Ti 0-0.01wt%, and the balance being Al.

[0013] Preferably, the chemical composition of the Al-Zn-Mg-Cu alloy further includes Fe element; wherein the content of Fe element is less than or equal to 0.01wt%.

[0014] Preferably, the chemical composition of the Al-Zn-Mg-Cu alloy further includes Si element; wherein the content of Si element is less than or equal to 0.01wt%.

[0015] Preferably, the Al-Zn-Mg-Cu alloy is Al-Zn-Mg-Cu alloy profile;

[0016] Preferably, before the solution treatment step, the method further comprises:

[0017] Preparation step of Al-Zn-Mg-Cu alloy profile: hot extruding the Al-Zn-Mg-Cu alloy bar; wherein the extruding temperature is 455-465℃, the extruding speed is ≤10m / min, and the extruding ratio is 15-17.

[0018] Preferably, in the solution treatment step, the method further comprises:

[0019] solid-solution treating the Al-Zn-Mg-Cu alloy at a temperature of 465-475 ℃ for 3-4 h, and cooling to obtain a solid-solution treated Al-Zn-Mg-Cu alloy;

[0020] Preferably, the cooling mode is water quenching.

[0021] Preferably, in the step of stress aging treatment, the applied tensile stress value is 135-450 MPa, the stress aging treatment temperature is 100-130 ℃, and the stress aging treatment time is 12-24 h.

[0022] Preferably, in the microstructure of the Al-Zn-Mg-Cu alloy after stress aging treatment, the grain boundary precipitates are discontinuously distributed, the size of the grain boundary precipitates is 20-35 nm, the grain boundary precipitates include long rod-shaped MgZn2 phase, the intragranular precipitates have a size of 5-10 nm, the intragranular precipitates include short rod-shaped MgZn2 phase, and there is no intergranular precipitate-free zone (i.e., the precipitates are distributed on both sides of the grain boundary).

[0023] The grain boundary precipitates are discontinuously distributed, the size of the grain boundary precipitates is 20-35 nm, the grain boundary precipitates include long rod-shaped MgZn2 phase, the intragranular precipitates have a size of 5-10 nm, the intragranular precipitates include short rod-shaped MgZn2 phase, and there is no intergranular precipitate-free zone.

[0024] Preferably, in the step of artificial aging treatment, the artificial aging treatment temperature is 140-160 ℃, and the artificial aging treatment time is 5-10 h.

[0025] In another aspect, the embodiment of the present application provides a heat-treated Al-Zn-Mg-Cu alloy, which is obtained by heat treating an Al-Zn-Mg-Cu alloy by using the heat treatment method of the Al-Zn-Mg-Cu alloy according to any one of the above-mentioned embodiments.

[0026] Preferably, in the microstructure of the heat-treated Al-Zn-Mg-Cu alloy, the grain boundary precipitates are discontinuously distributed, the size of the intergranular precipitates is 20-35 nm, the grain boundary precipitates include long rod-shaped MgZn2 phase, the size of the intragranular precipitates does not exceed 10 nm, the intragranular precipitates include short rod-shaped MgZn2 phase, there is no intergranular precipitate-free zone, and precipitate twin boundary morphology is formed in the matrix.

[0027] Compared with the prior art, the heat treatment method of the Al-Zn-Mg-Cu alloy has at least the following beneficial effects:

[0028] The embodiment of the present application provides a heat treatment method of Al-Zn-Mg-Cu alloy, which comprises the following steps: solid solution treatment is performed on the Al-Zn-Mg-Cu alloy to obtain the Al-Zn-Mg-Cu alloy after solid solution treatment; stress aging treatment is performed on the Al-Zn-Mg-Cu alloy after solid solution treatment under an applied stress field and a thermal field to obtain the Al-Zn-Mg-Cu alloy after stress aging treatment; artificial aging treatment is performed on the Al-Zn-Mg-Cu alloy after stress aging treatment to obtain the Al-Zn-Mg-Cu alloy after heat treatment. It should be noted that in the stress aging treatment stage, the applied stress field and the thermal field jointly act on the supersaturated solid solution, the lattice distortion introduced by the stress field increases the vacancy constraint force of the matrix, so that the migration rate of the matrix in the crystal and the grain boundary is slowed down, at the same time, the lattice distortion and the dislocation defect increase the nucleation sites of the solute atoms, reduce the precipitation ability barrier, promote the dispersed distribution of the intracrystalline precipitates, and synchronously inhibit the intergranular precipitate-free zone. A large number of supersaturated solute atoms are precipitated in the crystal, so that the size and quantity of the grain boundary precipitates can be effectively controlled, and finally the synergistic regulation of the intracrystalline-grain boundary precipitates is realized. When the artificial aging treatment is performed subsequently, the small precipitates formed in the grain boundary are further grown and spheroidized, and the corrosion resistance of the matrix is effectively improved. More importantly, when the artificial aging treatment is performed at a temperature higher than the stress aging temperature, the intracrystalline precipitates grow, and due to the phase orientation relationship characteristics, the intracrystalline precipitates intersect during the growth process, form the precipitate interface twin morphology, effectively store dislocations during the plastic deformation process, and realize the purpose of coordinating the dislocation movement by means of the deformation of the intracrystalline precipitates, so that the strength and plasticity of the matrix are finally improved.

[0029] Compared with the traditional T77 process, the heat treatment technology of the present application can further improve the strength and plasticity, and simultaneously optimize the corrosion resistance. In addition, the process of the present application is simple, the process parameters have a wide feasible range, and the industrial production is facilitated.

[0030] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, and the content of the specification can be implemented. The following describes the preferred embodiments of the present application in detail with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a transmission organization diagram of the Al-Zn-Mg-Cu alloy after heat treatment; wherein, Figure 1 The (a) diagram in the above formula is a transmission organization diagram of the Al-Zn-Mg-Cu alloy after T77 aging treatment in the comparative example 1;

[0032] Figure 1 The (b) diagram in the above formula is a transmission organization diagram of the Al-Zn-Mg-Cu alloy after stress aging treatment in the comparative example 3; Figure 1(c1) of FIG. 1 is a grain boundary precipitate distribution morphology diagram of the Al-Zn-Mg-Cu alloy after heat treatment in Example 5, Figure 1 (c2) of FIG. 1 is a precipitate interface twin microstructure morphology characterization diagram of the Al-Zn-Mg-Cu alloy after heat treatment in Example 5.

[0033] Figure 2 is an intergranular corrosion depth diagram of the Al-Zn-Mg-Cu alloy after heat treatment; wherein, Figure 2 (a) of FIG. 1 is an intergranular corrosion depth diagram of the Al-Zn-Mg-Cu alloy after heat treatment in Example 5; Figure 2 (b) of FIG. 1 is an intergranular corrosion depth diagram of the Al-Zn-Mg-Cu alloy after T77 aging treatment in Comparative Example 1. DETAILED DESCRIPTION

[0034] To further clarify the technical means and effects taken by the present application to achieve the predetermined object of the application, the following describes the specific embodiments, structures, features and effects according to the present application in detail in combination with the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0035] The present application provides a heat treatment method of Al-Zn-Mg-Cu alloy. The Al-Zn-Mg-Cu alloy profile is obtained after solid solution treatment to obtain a supersaturated solid solution. First, stress aging treatment is performed under an applied stress field and a thermal field, and then artificial aging treatment is performed. The principle of the present application is described as follows:

[0036] In the stress aging stage, the applied stress field and the thermal field act on the supersaturated solid solution together. The lattice distortion introduced by the stress field increases the vacancy constraint force of the matrix, which slows down the migration rate of vacancies in the crystal and at the grain boundary. At the same time, the lattice distortion and dislocation defects increase the nucleation sites of solute atoms, reduce the precipitation ability barrier, promote the dispersion distribution of intracrystalline precipitates, and simultaneously inhibit the intergranular precipitate-free zone. A large number of supersaturated solute atoms are precipitated in the crystal, so that the size and quantity of the grain boundary precipitates can be effectively controlled, and finally the synergistic regulation of intracrystalline-grain boundary precipitates is realized.

[0037] The inventor of the present application finds that stress field couples with thermal field, and the dispersion of intracrystalline precipitated phase and the control of intercrystalline precipitate-free zone are comprehensively solved, which is beneficial to the improvement of strength and plasticity of the material. Meanwhile, the material after stress aging is subjected to artificial aging treatment, the small precipitated phase originally formed at the grain boundary is further grown and spheroidized, and the corrosion resistance of the matrix is effectively improved. More importantly, the intracrystalline precipitated phase is grown at a temperature higher than the stress aging temperature, and due to the phase orientation relationship characteristics, the intracrystalline precipitated phase intersects during the growth process, and the intersection orientation is The interface is taken as an axis, and the precipitated phase presents a symmetrical relationship on both sides to form a twin interface, and the key factor is that, during the stress aging process, the introduction of lattice defects reduces the η' phase precipitated energy barrier, improves the precipitation rate, and provides more nucleation sites for the precipitated phase, thereby increasing the precipitated phase density. Under the joint action, the docking probability of the precipitated phase is promoted, and the precipitated phase morphology is changed, thereby promoting the formation of the precipitated phase twin interface microstructure. Further research finds that, during the room temperature stretching process, the precipitated phase twin interface structure is increased from 109.5° to 112.7° (the force axis is parallel to the twin interface) and 121.5° (the force axis is perpendicular to the twin interface), respectively. Compared with the dislocation bypass mechanism as the main deformation mode of the conventional η' / η phase, the change of the structure of the precipitated phase twin interface itself improves the constraint and storage capacity of the dislocation. Therefore, the precipitated phase twin interface microstructure can effectively store dislocations during plastic deformation, and realizes the purpose of coordinating dislocation movement by means of its own deformation, and finally realizes the improvement of the strength and plasticity of the matrix.

[0038] The specific scheme of the present application is as follows:

[0039] The present application provides a heat treatment method of Al-Zn-Mg-Cu alloy, which comprises the following steps:

[0040] Solution treatment: the Al-Zn-Mg-Cu alloy (i.e. Al-Zn-Mg-Cu alloy profile) is subjected to solution treatment to obtain the Al-Zn-Mg-Cu alloy after solution treatment.

[0041] Preferably, the chemical composition of the Al-Zn-Mg-Cu alloy further comprises Fe element; and the content of the Fe element is less than or equal to 0.01wt%. Preferably, the chemical composition of the Al-Zn-Mg-Cu alloy further comprises Si element; and the content of the Si element is less than or equal to 0.01wt%.

[0042] Preferably, the chemical composition of the Al-Zn-Mg-Cu alloy further comprises Fe element; and the content of the Fe element is less than or equal to 0.01wt%. Preferably, the chemical composition of the Al-Zn-Mg-Cu alloy further comprises Si element; and the content of the Si element is less than or equal to 0.01wt%.

[0043] Preferably, the Al-Zn-Mg-Cu alloy is solution treated at a temperature of 465-475℃ for 3-4h, and after cooling, the solution treated Al-Zn-Mg-Cu alloy is obtained; preferably, the cooling method is selected from water quenching.

[0044] It should be further noted that the preparation steps of the Al-Zn-Mg-Cu alloy profile include: heat extruding the Al-Zn-Mg-Cu alloy bar; wherein the extruding temperature is 455-465℃, the extruding speed is ≤10m / min, and the extruding ratio is 15-17.

[0045] Stress aging treatment: the solution treated Al-Zn-Mg-Cu alloy is subjected to stress aging treatment under an applied stress field and a thermal field, and the stress aged Al-Zn-Mg-Cu alloy is obtained.

[0046] In this step, the applied tensile stress value is 135-450MPa, the stress aging treatment temperature is 100-130℃, and the stress aging treatment time is 12-24h.

[0047] Artificial aging treatment: the stress aged Al-Zn-Mg-Cu alloy is subjected to artificial aging treatment, and the heat treated Al-Zn-Mg-Cu alloy is obtained.

[0048] In this step, the artificial aging treatment temperature is 140-160℃, and the artificial aging treatment time is 5-10h.

[0049] The present application is further illustrated by the following specific examples:

[0050] Comparative Example 1

[0051] Comparative Example 1

[0052] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is solution treated at a temperature of 470℃ for 3h, and then subjected to cold water quenching, and the solution treated Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is obtained.

[0053] T77 aging treatment: the solution treated Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to T77 aging treatment, and the heat treated Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is obtained.

[0054] The process parameters of the T77 aging treatment are 120℃ / 24h+180℃ / 1h+120℃ / 24h. After the above aging process, the tensile strength, yield strength, elongation, and intergranular corrosion of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment are tested, and the results are shown in Table 1.

[0055] Example 1

[0056] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is heat treated, mainly including the following steps:

[0057] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to solution treatment at a temperature of 470℃ for 3h, and then cold water quenching is performed to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0058] Stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment is subjected to stress aging treatment at an external tensile stress value of 135MPa and a temperature of 120℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment;

[0059] Artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment is subjected to artificial aging treatment at a temperature of 150℃ for 7h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment.

[0060] The tensile strength, yield strength, elongation, and intergranular corrosion of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment of this embodiment are tested, and the results are shown in Table 1.

[0061] Example 2

[0062] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is heat treated, mainly including the following steps:

[0063] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to solution treatment at a temperature of 470℃ for 3h, and then cold water quenching is performed to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0064] stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the solid solution treatment is subjected to the stress aging treatment at 270 MPa of the applied tensile stress value and 120℃ for 24h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the stress aging treatment;

[0065] artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the stress aging treatment is subjected to the artificial aging treatment at 150℃ for 7h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the heat treatment.

[0066] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the heat treatment is tested for the tensile strength, the yield strength, the elongation, and the intergranular corrosion, and the results are shown in Table 1.

[0067] Example 3

[0068] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to the heat treatment, mainly including the following steps:

[0069] solid solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to the solid solution treatment at 470℃ for 3h, and then subjected to the cold water quenching, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the solid solution treatment;

[0070] stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the solid solution treatment is subjected to the stress aging treatment at 450 MPa of the applied tensile stress value and 120℃ for 24h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the stress aging treatment;

[0071] artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the stress aging treatment is subjected to the artificial aging treatment at 150℃ for 7h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the heat treatment.

[0072] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after the heat treatment is tested for the tensile strength, the yield strength, the elongation, and the intergranular corrosion, and the results are shown in Table 1.

[0073] Comparative Example 2

[0074] A comparative example 2 Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile was heat treated, mainly including the following steps:

[0075] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile was solution treated at a temperature of 470℃ for 3h, and then cold water quenched to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0076] Stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment was stress aged at an external tensile stress value of 135MPa and a condition of 120℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment.

[0077] Wherein, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment of the comparative example 2 was tested for tensile strength, yield strength, elongation, intergranular corrosion, and the results are shown in Table 1.

[0078] Example 4

[0079] The Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile of this example was heat treated, mainly including the following steps:

[0080] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile was solution treated at a temperature of 470℃ for 3h, and then cold water quenched to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0081] Stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment was stress aged at an external tensile stress value of 135MPa and a condition of 120℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment.

[0082] Artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment was artificially aged at a condition of 160℃ for 10h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment.

[0083] The tensile strength, yield strength, elongation, intergranular corrosion of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment of the present embodiment were tested, and the results are shown in Table 1.

[0084] Comparative Example 3

[0085] Comparative Example 3

[0086] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile was solution treated at a temperature of 470℃ for 3h, and then cold water quenched to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0087] Stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment was subjected to stress aging treatment at an external tensile stress value of 270MPa and a condition of 120℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment.

[0088] The tensile strength, yield strength, elongation, intergranular corrosion of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment of Comparative Example 3 were tested, and the results are shown in Table 1.

[0089] Example 5

[0090] The Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile was heat treated, mainly including the following steps:

[0091] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile was solution treated at a temperature of 470℃ for 3h, and then cold water quenched to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0092] Stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment was subjected to stress aging treatment at an external tensile stress value of 270MPa and a condition of 120℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment.

[0093] artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment is subjected to artificial aging treatment at 160℃ for 10h to obtain the heat-treated Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile.

[0094] Wherein, the tensile strength, yield strength, elongation, intergranular corrosion of the heat-treated Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile of the present embodiment are tested, and the results are shown in Table 1.

[0095] Comparative Example 4

[0096] Comparative Example 4

[0097] solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to solution treatment at a temperature of 470℃ for 3h, and then cold water quenching is performed to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0098] stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment is subjected to stress aging treatment at an external tensile stress value of 450MPa and a temperature of 120℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment.

[0099] Wherein, the tensile strength, yield strength, elongation, intergranular corrosion of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment of Comparative Example 4 are tested, and the results are shown in Table 1.

[0100] Example 6

[0101] The Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to heat treatment, mainly including the following steps:

[0102] solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to solution treatment at a temperature of 470℃ for 3h, and then cold water quenching is performed to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0103] stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solid solution treatment is subjected to stress aging treatment at an applied tensile stress value of 450 MPa and a condition of 120 °C for 24 h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment;

[0104] artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment is subjected to artificial aging treatment at 140 °C for 10 h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment.

[0105] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment is tested for tensile strength, yield strength, elongation, and intergranular corrosion, and the results are shown in Table 1.

[0106] Example 7

[0107] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to heat treatment, which mainly includes the following steps:

[0108] solid solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to solid solution treatment at a temperature of 470 °C for 3 h, and then cold water quenching, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solid solution treatment;

[0109] stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solid solution treatment is subjected to stress aging treatment at an applied tensile stress value of 450 MPa and a condition of 100 °C for 24 h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment;

[0110] artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment is subjected to artificial aging treatment at 140 °C for 10 h, to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment.

[0111] In this embodiment, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment is tested for tensile strength, yield strength, elongation, and intergranular corrosion, and the results are shown in Table 1.

[0112] Example 8

[0113] The Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile of this example was heat treated, and the difference from example 6 is that the time of stress aging treatment was 12h.

[0114] Other aspects are consistent with example 6.

[0115] Wherein, the tensile strength, yield strength, elongation, intergranular corrosion of the heat treated Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile of this example were tested, and the results are shown in Table 1.

[0116] Comparative example 5

[0117] Comparative example 5 heat treated the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile, mainly including the following steps:

[0118] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile was solution treated at a temperature of 470℃ for 3h, and then cold water quenched to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0119] Stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment was stress aged at an external tensile stress value of 85MPa and a temperature of 90℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment;

[0120] Artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment was artificially aged at a temperature of 150℃ for 7h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment.

[0121] Wherein, the tensile strength, yield strength, elongation, intergranular corrosion of the heat treated Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile of this example were tested, and the results are shown in Table 1.

[0122] Comparative example 6

[0123] Comparative example 6 heat treated the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile, mainly including the following steps:

[0124] Solution treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile is subjected to solution treatment at a temperature of 470℃ for 3h, and then subjected to cold water quenching to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment;

[0125] Stress aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after solution treatment is subjected to stress aging treatment at an external tensile stress value of 135MPa and a condition of 120℃ for 24h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment;

[0126] Artificial aging treatment: the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after stress aging treatment is subjected to artificial aging treatment at a condition of 120℃ for 12h to obtain the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment.

[0127] Wherein, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy profile after heat treatment of the comparative example is subjected to tensile strength, yield strength, elongation, intergranular corrosion tests, and the results are shown in Table 1.

[0128] Table 1

[0129]

[0130] As can be seen from Table 1, compared with the comparative example, the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy prepared in the embodiment of the application has excellent strength and plasticity and corrosion resistance.

[0131] Figure 1 is a transmission microstructure diagram of the Al-Zn-Mg-Cu alloy after heat treatment; wherein, Figure 1 the (a) diagram in is a transmission microstructure diagram of the Al-Zn-Mg-Cu alloy after T77 aging treatment in the comparative example 1;

[0132] Figure 1 the (b) diagram in is a transmission microstructure diagram of the Al-Zn-Mg-Cu alloy after stress aging treatment in the comparative example 3; Figure 1 the (c1) diagram in is a grain boundary precipitated phase distribution pattern diagram of the Al-Zn-Mg-Cu alloy after heat treatment in the embodiment 5, Figure 1 the (c2) diagram in is a precipitated phase interface twin microstructure pattern characterization diagram of the Al-Zn-Mg-Cu alloy after heat treatment in the embodiment 5.

[0133] Wherein, from Figure 1From the (a) figure in the figure, it can be seen that in the comparative example 1, after the solid solution treatment of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy, after T77 treatment, the intergranular precipitated phase of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy presents intermittent distribution, the size is about 70-90nm, the intergranular precipitate-free zone is wide, about 145nm, and the intragranular precipitated phase size is about 15-25nm. The precipitate-free zone as a soft zone, in the uniaxial stretching process, is easy to form a stress concentration zone, which leads to premature fracture of the material, restricts the further improvement of the strength and plasticity, and the electrochemical properties of the zone are different from the matrix and grain boundary, so the intergranular corrosion performance improvement effect is limited.

[0134] wherein, from Figure 1 From the (b) figure in the figure, it can be seen that in the comparative example 3, after the solid solution treatment of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy, after 270MPa-120℃ / 24h stress aging treatment, the intergranular precipitated phase of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy presents intermittent distribution, the size is about 20-35nm, there is no intergranular precipitate-free zone, and the intragranular precipitated phase size is about 5-10nm. The microstructure is beneficial to the synergistic improvement of the matrix strength and corrosion resistance, but based on the strength-plasticity constraint relationship, the matrix plasticity is low.

[0135] wherein, from Figure 1 From the (c1) and (c2) figures in the figure, it can be seen that after 270MPa-120℃ / 24h stress aging treatment, and then 160℃ / 10h artificial aging treatment, the intergranular precipitated phase of the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy presents intermittent distribution, the size is about 5-25nm, there is no intergranular precipitate-free zone, and the intragranular precipitated phase size is not more than 10nm. At the same time, the precipitated phase twin boundary microstructure is formed in the matrix, and the new microstructure has good dislocation storage effect in the uniaxial stretching process, and the matrix plasticity improvement effect is remarkable.

[0136] The intergranular corrosion test was carried out on the alloy after heat treatment of the comparative example 5 and the comparative example 1; wherein, Figure 2 is the intergranular corrosion depth figure of the Al-Zn-Mg-Cu alloy after heat treatment; wherein, Figure 2 The (a) figure in the figure is the intergranular corrosion depth figure of the Al-Zn-Mg-Cu alloy after heat treatment in the example 5; Figure 2 The (b) figure in the figure is the intergranular corrosion depth figure of the Al-Zn-Mg-Cu alloy after T77 aging treatment in the comparative example 1.

[0137] From Figure 2It can be seen that: after the Al-10Zn-3Mg-2.5Cu-0.15Zr alloy after solid solution treatment, after 270MPa-120℃ / 24h stress aging treatment, continue to complete 160℃ / 10h artificial aging, the intergranular corrosion depth (see (a) in 2) is shallower than the corrosion depth after T77 treatment (see (b) in 2), and the grain boundary corrosion width is small, which shows that by eliminating the grain boundary non-precipitation zone, the difference between intracrystalline-grain boundary precipitation is effectively reduced, the formation and expansion of anode corrosion channel are inhibited, and the corrosion resistance of the alloy is improved. Figure 1

[0138] In addition, from the comparison of examples and comparative examples 5 and 6, it can be seen that the control of the parameters (applied tensile stress value, temperature) of stress aging and artificial aging is very important, otherwise it is difficult to realize the synergistic improvement of strength and plasticity.

[0139] In summary, compared with the traditional regression re-aging (pre-aging-over-aging-re-aging), the strength and plasticity of the alloy after the process treatment of the present application are improved, and the corrosion resistance is also significantly improved. In the aging process of the present application, a stress field is added synchronously, which introduces lattice distortion and dislocation defects in the grain interior, promotes the dispersion precipitation of intracrystalline MgZn2 phase, at the same time, the lattice distortion strengthens the constraint force of vacancies in the matrix, slows down the migration of solute atoms to the grain boundary, and effectively inhibits the formation of intergranular non-precipitation zone, so that the intergranular precipitates are small and intermittent, so that the strength, plasticity and corrosion resistance of the alloy are improved synchronously. In addition, the process of the present application is simple, the parameter domain is wide, and it is easy for industrial production.

[0140] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application still belongs to the scope of the technical solution of the present application.​

Claims

1. A method of heat treatment of an Al-Zn-Mg-Cu alloy, characterized in that, It comprises the following steps: Solution treatment: the Al-Zn-Mg-Cu alloy is subjected to solution treatment to obtain the Al-Zn-Mg-Cu alloy after solution treatment; wherein the chemical composition of the Al-Zn-Mg-Cu alloy includes, in terms of weight percentage: Zn 9.5-10.5wt%, Mg 2.5-3.5wt%, Cu 1.5-2.5wt%, Zr 0.05~0.15wt%, Ti 0~0.01wt%, and the balance being Al; Stress aging treatment: the Al-Zn-Mg-Cu alloy after solution treatment is subjected to stress aging treatment under an applied stress field and a thermal field to obtain the Al-Zn-Mg-Cu alloy after stress aging treatment; wherein the applied tensile stress value is 135-450MPa, the stress aging treatment temperature is 100-130℃, and the stress aging treatment time is 12-24h; Artificial aging treatment: the Al-Zn-Mg-Cu alloy after stress aging treatment is subjected to artificial aging treatment to obtain the Al-Zn-Mg-Cu alloy after heat treatment; wherein the artificial aging treatment temperature is 140-160℃, and the artificial aging treatment time is 5-10h; Wherein, in the microstructure of the Al-Zn-Mg-Cu alloy after heat treatment: the grain boundary precipitates present intermittent distribution, the size of the intergranular precipitates is 20-35nm, the grain boundary precipitates include long rod-shaped MgZn2 phase, the size of the intragranular precipitates is not more than 10nm, the intragranular precipitates include short rod-shaped MgZn2 phase; there is no intergranular precipitate-free zone; the precipitate twin boundary morphology is formed in the matrix.

2. The method of heat treatment of an Al-Zn-Mg-Cu alloy according to claim 1, characterized in that, The chemical composition of the Al-Zn-Mg-Cu alloy further includes Fe element; wherein the content of Fe element is less than or equal to 0.01wt%; and / or The chemical composition of the Al-Zn-Mg-Cu alloy further includes Si element; wherein the content of Si element is less than or equal to 0.01wt%.

3. The method of heat treatment of an Al-Zn-Mg-Cu alloy according to claim 1, characterized in that, The Al-Zn-Mg-Cu alloy is an Al-Zn-Mg-Cu alloy profile.

4. The method of heat treatment of an Al-Zn-Mg-Cu alloy according to claim 3, characterized in that Before the solution treatment step, further comprising: Preparation step of Al-Zn-Mg-Cu alloy profile: the Al-Zn-Mg-Cu alloy bar is subjected to hot extrusion treatment; wherein the extrusion treatment temperature is 455~465℃, the extrusion treatment speed is ≤10m / min, and the extrusion ratio is 15~17.

5. The method of heat treatment of an Al-Zn-Mg-Cu alloy according to claim 1, characterized in that, In the solution treatment step: The Al-Zn-Mg-Cu alloy is subjected to solution treatment at a temperature of 465-475℃ for 3-4h, and after cooling, the Al-Zn-Mg-Cu alloy after solution treatment is obtained.

6. The method of heat treatment of an Al-Zn-Mg-Cu alloy according to claim 5, characterized in that The cooling method is selected to be water quenching.

7. The method of heat treatment of an Al-Zn-Mg-Cu alloy according to any one of claims 1 to 6, characterized in that, In the microstructure of the Al-Zn-Mg-Cu alloy after stress aging treatment: The grain boundary precipitates are discontinuously distributed, the grain boundary precipitates have a size of 20-35 nm, the grain boundary precipitates comprise long rod-shaped MgZn2 phases; the intragranular precipitates have a size of 5-10 nm, the intragranular precipitates comprise short rod-shaped MgZn2 phases; and there is no intergranular precipitate-free zone.

8. An Al-Zn-Mg-Cu alloy after heat treatment, characterized in that, The heat-treated Al-Zn-Mg-Cu alloy is obtained by heat treating the Al-Zn-Mg-Cu alloy according to the heat treatment method of any one of claims 1-7.

9. The heat treated Al-Zn-Mg-Cu alloy according to claim 8, characterized in that In the microstructure of the heat-treated Al-Zn-Mg-Cu alloy: The grain boundary precipitates are discontinuously distributed, the grain boundary precipitates have a size of 20-35 nm, the grain boundary precipitates comprise long rod-shaped MgZn2 phases, the intragranular precipitates have a size of not more than 10 nm, the intragranular precipitates comprise short rod-shaped MgZn2 phases; there is no intergranular precipitate-free zone; and a precipitate twin boundary interface morphology is formed in the matrix.

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