CN112322947B - High-strength plastic Al-Mg-Si-Zn alloy for automobile and preparation method thereof - Google Patents
High-strength plastic Al-Mg-Si-Zn alloy for automobile and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-strength plastic Al-Mg-Si-Zn alloy for an automobile and a preparation method thereof, belonging to the field of aluminum alloys for automobiles. The high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises, by mass, 0.52-2.25% of Mg, 0.42-2.75% of Si, 2.15-3.53% of Zn and the balance of Al; the mass relation between Mg and Si satisfies the following condition that Mg: si is 0.85 to 1.25. Experimental results show that the yield strength of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile can reach 323-332 MPa, the tensile strength can reach 364-370 MPa, the Vickers hardness can reach 125-135 HV, and the elongation can reach 20.4-22.1%.
Description
Technical Field
The invention relates to the field of aluminum alloy for automobiles, in particular to a high-strength plastic Al-Mg-Si-Zn alloy for automobiles and a preparation method thereof.
Background
With the increasing awareness of energy conservation and environmental protection, the light weight of automobiles becomes the leading edge and hot spot of the automobile industry technology in the 21 st century. The Al-Mg-Si series aluminum alloy strengthened by heat treatment is a key material of aluminum alloy for automobile bodies because of excellent welding performance and corrosion resistance, no stress corrosion cracking tendency, good formability and the like. However, compared with the conventional automobile steel plate, the Al-Mg-Si series aluminum alloy for the automobile body has lower strength and plasticity, and is difficult to meet the requirement of the mechanical property of the aluminum alloy for the automobile body.
At present, although some researchers improve the strength and hardness of Al-Mg-Si aluminum alloy by adding Zn element to improve the precipitation phase, the Al-Mg-Si aluminum alloy added with Zn has more precipitation phase types and complex distribution, and the plasticity is difficult to reach a higher level. However, the outer cover sheet material for automobiles must have good press formability, i.e., high plasticity is required for the aluminum alloy sheet material to achieve good press forming effect. Therefore, there is a need for a Zn-containing Al — Mg — Si-based aluminum alloy having high strength, high hardness, and high plasticity.
Disclosure of Invention
The invention aims to provide a high-strength plastic Al-Mg-Si-Zn alloy for automobiles, which can simultaneously have high strength, high hardness and high plasticity.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a high-strength plastic Al-Mg-Si-Zn alloy for automobiles, which comprises, by mass, 0.52-2.25% of Mg, 0.42-2.75% of Si, 2.15-3.53% of Zn and the balance of Al; the mass relation between Mg and Si satisfies the following condition that Mg: si = 0.85-1.25.
Preferably, the high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises, by mass, 0.58% -2.15% of Mg, 0.48% -2.55% of Si, 2.25% -3.45% of Zn and the balance of Al; the mass relation between Mg and Si satisfies the following condition that Mg: si = 0.95-1.15.
The invention also provides a preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile, which comprises the following steps:
(1) smelting alloy raw materials and then casting to obtain a cast ingot;
(2) sequentially carrying out primary homogenization heat treatment and secondary homogenization heat treatment on the cast ingot obtained in the step (1) to obtain a homogenized alloy;
(3) sequentially carrying out hot rolling and cold rolling on the homogenized alloy obtained in the step (2) to obtain an aluminum alloy blank;
(4) sequentially carrying out primary solution treatment and secondary solution treatment on the aluminum alloy blank obtained in the step (3) to obtain a solid solution aluminum alloy;
(5) and (3) sequentially carrying out primary aging treatment and secondary aging treatment on the solid-solution aluminum alloy obtained in the step (4) to obtain the high-strength plastic Al-Mg-Si-Zn alloy for the automobile.
Preferably, the heat preservation temperature of the primary homogenization heat treatment in the step (2) is 450-500 ℃, and the heat preservation time of the primary homogenization heat treatment is 7-9 hours.
Preferably, the heat preservation temperature of the secondary homogenization heat treatment in the step (2) is 550-600 ℃, and the heat preservation time of the secondary homogenization heat treatment is 15-17 hours.
Preferably, the step (3) further comprises heat preservation before hot rolling, wherein the heat preservation temperature is 400-450 ℃, and the heat preservation time is 1.5-2 hours.
Preferably, the heat preservation temperature of the primary solution treatment in the step (4) is 460-500 ℃, and the heat preservation time of the primary solution treatment is 0.5-1 h.
Preferably, the heat preservation temperature of the secondary solution treatment in the step (4) is 550-600 ℃, and the heat preservation time of the secondary solution treatment is 0.5-1 h.
Preferably, the heat preservation temperature of the primary aging treatment in the step (5) is 150-180 ℃, and the heat preservation time of the primary aging treatment is 1-2.5 h.
Preferably, the heat preservation temperature of the secondary aging treatment in the step (5) is 100-130 ℃, and the heat preservation time of the secondary aging treatment is 70-80 h.
The invention provides a high-strength plastic Al-Mg-Si-Zn alloy for automobiles, which comprises, by mass, 0.52-2.25% of Mg, 0.42-2.75% of Si, 2.15-3.53% of Zn and the balance of Al; the mass relation between Mg and Si satisfies the following condition that Mg: si = 0.85-1.25. The high-strength plastic Al-Mg-Si-Zn alloy for the automobile, provided by the invention, can form a lath-shaped metastable eta' precipitated phase, namely MgZn, in an aluminum alloy matrix by adding Zn element as a trace strengthening element2While adjusting the relative contents of Mg and Si elements to obtain a uniform and fine beta' phase as the main strengthening phase, i.e. Mg2The Si phase effectively regulates and controls the structure appearance of the aluminum alloy and the precipitation behavior of the precipitated phase, so that the synergistic strengthening effect is achieved among the precipitated phases, the strength of the aluminum alloy is effectively improved, and the high plasticity of the aluminum alloy is ensured. The experimental results show that the high-temperature-resistant steel,the yield strength of the sample in the embodiment of the invention can reach 323-332 MPa, the tensile strength can reach 364-370 MPa, the Vickers hardness can reach 125-135 HV, and the elongation can reach 20.4-22.1%.
Drawings
FIG. 1 is a plot of the peak age state engineering stress strain for the aged process alloy of the example 6 sample of the invention;
FIG. 2 is a TEM image of a sample of example 6 of the present invention observed under a transmission electron microscope.
Detailed Description
The invention provides a high-strength plastic Al-Mg-Si-Zn alloy for automobiles, which comprises, by mass, 0.52-2.25% of Mg, 0.42-2.75% of Si, 2.15-3.53% of Zn and the balance of Al; the mass relation between Mg and Si satisfies the following condition that Mg: si = 0.85-1.25.
According to the mass percentage, the high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises 0.52-2.25% of Mg, preferably 0.58-2.15%, and more preferably 0.65-1.95%. In the invention, the Mg is an element which is firstly precipitated in the aluminum alloy matrix and forms a micro-area Mg-rich cluster which is used as a basis for forming a strengthening phase by being combined with other elements subsequently.
According to the mass percentage, the high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises 0.42% -2.75% of Si, preferably 0.48% -2.55% of Si, and more preferably 0.55% -2.35% of Si. In the invention, the order of Si precipitation in the aluminum alloy matrix is an element next to Mg precipitation, because Si atoms have smaller atomic radius than the aluminum matrix, the formed Si-rich clusters cause tensile stress of the peripheral lattices of the clusters, and the micro-area Mg-rich clusters formed by Mg atoms with larger atomic radius than the aluminum matrix cause compressive stress of the peripheral lattices, so that lattice distortion is reduced, elastic strain energy is reduced, Si atoms can diffuse to Mg clusters to form strong interaction with the Mg clusters to form Mg-Si co-clusters, and a beta' phase, namely a main strengthening phase Mg-rich cluster, is firstly formed in the heat treatment process2A Si phase.
In the invention, the mass relationship between Mg and Si satisfies the following condition: si = 0.85-1.25, preferably 1.05-1.10, and more preferably 1.05-1.07. According to the invention, the texture morphology and the precipitation behavior of precipitated phases of the aluminum alloy are effectively regulated and controlled by controlling the mass relationship between Mg and Si, the precipitation power and the precipitation quantity of beta '' phases and eta '' phases are improved, the synergistic strengthening effect between the precipitated phases is achieved, and the high plasticity of the aluminum alloy can be ensured while the strength of the aluminum alloy is effectively improved.
The high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises, by mass, 2.15% -3.53% of Zn, preferably 2.55% -3.35% of Zn, and more preferably 2.85% -3.35% of Zn. In the invention, the Zn is dissolved in the aluminum alloy matrix in a large amount, can promote the precipitation of other atoms, improve the cluster number of aging of the aluminum alloy, refine the cluster size, and can be combined with Mg atoms to form an eta' precipitation phase, namely MgZn, along with the improvement of the precipitation power2Phase with the primary strengthening phase Mg precipitated first2The Si phase plays a role in synergistic reinforcement, and the mechanical property of the aluminum alloy is effectively improved.
According to the mass percentage, the high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises the balance of Al except the alloy elements.
In the embodiment of the invention, the high-strength plastic Al-Mg-Si-Zn alloy for the automobile can be specifically Al-0.52Mg-0.59Si-3.5Zn aluminum alloy, Al-2.2Mg-2.45Si-3.3Zn aluminum alloy or Al-1.95Mg-1.65Si-2.75Zn aluminum alloy.
The high-strength plastic Al-Mg-Si-Zn alloy for the automobile provided by the invention has the advantages that the structure is uniform, the composition segregation and the casting defect are avoided, the precipitated strengthening phases are dispersed in the matrix, the crystal grains are fine, the structure is compact, and the high-strength plastic Al-Mg-Si-Zn alloy has high strength and high plasticity.
The invention also provides a preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile, which comprises the following steps:
(1) smelting alloy raw materials and then casting to obtain a cast ingot;
(2) sequentially carrying out primary homogenization heat treatment and secondary homogenization heat treatment on the cast ingot obtained in the step (1) to obtain a homogenized alloy;
(3) sequentially carrying out hot rolling and cold rolling on the homogenized alloy obtained in the step (2) to obtain an aluminum alloy blank;
(4) sequentially carrying out primary solution treatment and secondary solution treatment on the aluminum alloy blank obtained in the step (3) to obtain a solid solution aluminum alloy;
(5) and (3) sequentially carrying out primary aging treatment and secondary aging treatment on the solid-solution aluminum alloy obtained in the step (4) to obtain the high-strength plastic Al-Mg-Si-Zn alloy for the automobile.
The alloy raw materials are smelted and then cast to obtain the cast ingot.
In the present invention, the alloy raw material preferably includes high purity aluminum, high purity magnesium, aluminum-silicon master alloy, and aluminum-zinc master alloy. According to the invention, high-purity aluminum and high-purity magnesium are selected as raw materials, so that impurity element impurities in the raw materials can be reduced, and meanwhile, Si and Zn elements are introduced in the form of aluminum-silicon intermediate alloy and aluminum-zinc intermediate alloy, so that the Si and Zn elements can be more fully and uniformly melted in an aluminum alloy melt at a lower content, so that the components of an alloy ingot are uniform, and the high-strength and high-plasticity aluminum alloy can be more favorably obtained.
In the invention, the smelting temperature is preferably 550-800 ℃, and more preferably 600-800 ℃; the smelting time is preferably 0.5-1 h, and more preferably 0.5-0.8 h. By controlling the proper smelting temperature and smelting time, the invention can ensure that all alloy raw materials form fully-molten alloy liquid in a low-burning loss and high-uniformity mixing state, reduce the volatilization of low-melting-point elements, reduce the formation probability of internal pores of the ingot, ensure that all alloy elements can be cooled and formed within a proportioning range, and is more favorable for obtaining the ingot with uniform components.
In the present invention, the melting apparatus is preferably a vacuum induction furnace.
In the present invention, the casting preferably uses a metal mold. The invention can obtain more proper cooling rate of the alloy melt by using the metal mold for casting, reduce casting defects and be more beneficial to obtaining the aluminum alloy with high strength and high plasticity.
After the ingot is obtained, the ingot is sequentially subjected to primary homogenization heat treatment and secondary homogenization heat treatment to obtain the homogenized alloy.
The device for the primary and secondary homogenization heat treatments is not particularly limited in the present invention, and a heating device well known to those skilled in the art may be used.
In the invention, the heating rates of the primary homogenization heat treatment and the secondary homogenization heat treatment are preferably 4-6 ℃/min, and more preferably 5 ℃/min. The heating rate of the homogenization heat treatment can ensure that the internal and external tissues of the ingot can reach the same heating and heat-preserving temperature in a short time, so that the condition that the external tissues of the ingot are heated for a long time and the internal tissues of the ingot are heated for a short time is avoided, and the alloy ingot with homogenized tissues can be obtained more favorably.
In the invention, the heat preservation temperature of the primary homogenization heat treatment is preferably 450-500 ℃, and more preferably 460-490 ℃; the heat preservation time of the primary homogenization heat treatment is preferably 7-9 hours, and more preferably 7.5-8.5 hours. In the primary homogenization heat treatment process, casting stress and segregation in the crystal can be eliminated at a lower temperature, and the risk of cracking caused by overlarge internal stress and uneven components in the subsequent rolling deformation treatment process is reduced.
In the present invention, it is preferable that the secondary homogenization heat treatment is performed by directly raising the temperature after the completion of the heat retention of the primary homogenization heat treatment. In the invention, the heat preservation temperature of the secondary homogenization heat treatment is preferably 550-600 ℃, and more preferably 560-590 ℃; the heat preservation time of the secondary homogenization treatment is preferably 15-17 hours, and more preferably 15.5-16.5 hours. The secondary homogenization treatment can fully carry out solid diffusion on each alloy element in the ingot at a higher temperature, further improves the structure homogenization degree of the alloy, and is more beneficial to the improvement of the plasticity of the aluminum alloy.
In the present invention, the cooling method of the secondary homogenization treatment is preferably furnace cooling to room temperature.
After the homogenized alloy is obtained, the homogenized alloy is sequentially subjected to hot rolling and cold rolling to obtain an aluminum alloy blank.
In the invention, the method also comprises heat preservation before hot rolling, wherein the heat preservation temperature is preferably 400-450 ℃, and more preferably 410-440 ℃; the heat preservation time is preferably 1.5-2 hours, and more preferably 1.5-1.6 hours. In the present invention, the means for keeping the temperature is not particularly limited, and a heating means known to those skilled in the art may be used.
In the invention, the total pass of the hot rolling is preferably 2-4, more preferably 2-3, and the deformation amount of each pass is preferably 18-22%, more preferably 19-21%. In the invention, in the hot rolling process, preferably, after each pass of rolling is finished, the temperature is preserved for 3-5 min at the temperature of 400-450 ℃, and then the rolling direction of the blank is changed to perform the next pass of rolling; the rolling direction is preferably turned 45 to 90 degrees in the counter-clockwise direction. According to the invention, the heat preservation temperature before hot rolling is controlled to be higher than the recrystallization temperature, so that the cast ingot can obtain higher plasticity during plastic deformation, and deformation cracking caused by overhigh deformation resistance of the cast ingot can be effectively avoided; meanwhile, the deformation of each pass of hot rolling can be controlled, so that coarse grains in a casting state can be crushed, casting cracks can be healed, casting defects are reduced and even eliminated, and the mechanical property of the aluminum alloy is obviously improved.
In the present invention, it is preferable to air-cool the aluminum alloy blank after hot rolling to a temperature for cold rolling and cold rolling. In the present invention, the temperature of the cold rolling is preferably not more than the recrystallization temperature, and more preferably 150 to 238 ℃. The deformation amount of each pass of the cold rolling is preferably 10-15%, and more preferably 11-14%. In the invention, in the cold rolling process, after each pass of rolling is preferably carried out, the rolling direction of the blank is changed to carry out the next pass of rolling; the rolling direction is preferably turned 45 to 90 degrees in the counter-clockwise direction.
In the invention, the thickness of the aluminum alloy blank obtained after cold rolling is preferably 1.2-1.5 mm. The cold rolling is carried out after the aluminum alloy blank after hot rolling is cooled to below the recrystallization temperature, so that the resistance in plastic deformation can be reduced under the condition of hot rolling residual heat, and the reduction of plasticity caused by overhigh age hardening degree can be avoided; meanwhile, by controlling the total cold rolling pass and the deformation of each pass, the aluminum alloy blank can be subjected to work hardening to a proper degree in the cold rolling deformation process, so that the hardness of the aluminum alloy is improved, and the high plasticity of the aluminum alloy is ensured.
After the aluminum alloy blank is obtained, the invention sequentially carries out primary solution treatment and secondary solution treatment on the aluminum alloy blank to obtain the solid solution aluminum alloy.
In the present invention, the apparatus for the primary solution treatment and the secondary solution treatment is not particularly limited, and a heating apparatus known to those skilled in the art may be used.
In the invention, the heat preservation temperature of the primary solution treatment is preferably 460-500 ℃, and more preferably 470-480 ℃; the heat preservation time of the primary solution treatment is preferably 0.5-1 h, and more preferably 0.6-0.9 h. In the first-stage solution treatment process, the excessive precipitated phase can be dissolved into the aluminum alloy matrix to initially form a solid solution structure by performing the pre-solution treatment at a lower temperature.
In the present invention, it is preferable that the secondary solution treatment is performed by directly raising the temperature after the completion of the heat preservation of the primary solution treatment. In the invention, the heat preservation temperature of the secondary solution treatment is preferably 550-600 ℃, and more preferably 560-590 ℃; the heat preservation time of the secondary solution treatment is 0.5-1 h, and more preferably 0.6-0.9 h. In the secondary solution treatment process, the coarse precipitated phase in the aluminum alloy blank can be more fully dissolved into the matrix at a higher temperature, so that the solid solution effect is enhanced, the aluminum alloy blank fully forms a uniform solid solution structure, the work hardening in the rolling deformation process is effectively improved, the plasticity reduction caused by the increase of the hardness of the aluminum alloy again due to the subsequent age hardening is avoided, and the strengthening phase with fine particles and uniform distribution is conveniently re-precipitated during the aging, so that the aluminum alloy has high strength, high hardness and high plasticity.
In the present invention, the cooling method of the secondary solution treatment is preferably furnace cooling; the final temperature of the cooling of the secondary solution treatment is preferably the heat preservation temperature of the primary aging treatment.
After the solid solution aluminum alloy is obtained, the invention sequentially carries out primary aging treatment and secondary aging treatment on the solid solution aluminum alloy to obtain the high-strength plastic Al-Mg-Si-Zn alloy for the automobile.
In the present invention, the primary aging treatment and the secondary aging treatment are not particularly limited, and a heating device known to those skilled in the art may be used.
In the invention, the heat preservation temperature of the primary aging treatment is preferably 150-180 ℃, and more preferably 160-170 ℃; the heat preservation time of the primary aging treatment is preferably 1-2.5 h, and more preferably 1.5-2 h. The method can ensure that the strengthening phase in the aluminum alloy after the solution treatment is uniformly nucleated by performing the pre-aging at the higher temperature of the primary aging treatment, and can become the core of the subsequent precipitated phase when the strengthening phase reaches a certain size, thereby improving the uniformity of the structure.
In the invention, the heat preservation temperature of the secondary aging treatment is preferably 100-130 ℃, and more preferably 110-120 ℃; the heat preservation time of the secondary aging treatment is preferably 70-80 h, and more preferably 72-78 h. In the secondary aging treatment process, the final aging is carried out in a mode of keeping at a lower temperature for a longer time, so that all precipitated phases can be uniformly precipitated to form fine strengthening phases which are distributed in a dispersed mode, and all strengthening phases have a synergistic effect, so that the hardness and the strength of the aluminum alloy are obviously improved.
In the present invention, the cooling method of the secondary aging treatment is preferably tapping air cooling to room temperature.
The preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile is more favorable for forming fine and dispersed precipitated phases, improves the precipitation power and the precipitation quantity of beta 'phase and eta' phase, enables the precipitated phases to have synergistic effect, can obviously improve the hardness and the strength of the aluminum alloy, can also enable the aluminum alloy to keep higher plasticity, can meet the requirements of the aluminum alloy for the automobile, and has simple process and low cost.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises, by mass, 0.52% of Mg, 0.59% of Si, 3.5% of Zn and the balance of Al; the mass relation of Mg and Si satisfies Mg: si = 0.88. The preparation method comprises the following specific steps:
(1) smelting high-purity aluminum, high-purity magnesium, aluminum-silicon intermediate alloy and aluminum-zinc intermediate alloy in a vacuum smelting furnace at 680 ℃ for 0.5h, and then casting in a metal copper mold to obtain an ingot;
(2) heating the ingot obtained in the step (1) to 455 ℃ at a heating rate of 5 ℃/min, preserving heat for 8 hours, and then cooling to room temperature along with the furnace to complete primary homogenization heat treatment; then heating to 555 ℃ at the heating rate of 5 ℃/min, preserving the heat for 16h, cooling to room temperature along with the furnace, and finishing secondary homogenization heat treatment to obtain a homogenized alloy;
(3) preserving the heat of the homogenized alloy obtained in the step (2) at the temperature of 420 ℃ for 1.5h, then carrying out first-pass hot rolling at the temperature, wherein the deformation is 20%, then preserving the heat at the temperature of 420 ℃ for 4min, carrying out second-pass hot rolling along anticlockwise rotation of 60 degrees, wherein the deformation is 18%, then carrying out first-pass cold rolling after air cooling to 200 ℃, wherein the deformation is 13%, carrying out second-pass cold rolling along anticlockwise rotation of 60 degrees, and the deformation is 12%, thus obtaining an aluminum alloy blank with the thickness of 1.3 mm;
(4) and (3) preserving the heat of the aluminum alloy blank obtained in the step (3) for 0.5h at 465 ℃ for primary solution treatment, then directly heating to 555 ℃ for 0.5h for secondary solution treatment, cooling to 160 ℃ along with the furnace, preserving the heat for 1.5h, completing primary aging treatment, cooling to 120 ℃ along with the furnace again, preserving the heat for 77h, discharging from the furnace, air cooling to room temperature, and completing secondary aging treatment to obtain the Al-0.52Mg-0.59Si-3.5Zn alloy.
Example 2
The high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises, by mass, 2.20% of Mg, 2.45% of Si, 2.30% of Zn and the balance of Al; the mass relation of Mg and Si satisfies Mg: si = 0.90. The specific preparation steps and parameters are the same as those of example 1, and the Al-2.2Mg-2.45Si-3.3Zn alloy is prepared.
Example 3
The high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises, by mass, 1.95% of Mg, 1.65% of Si, 2.75% of Zn and the balance of Al; the mass relation of Mg and Si satisfies Mg: si = 1.18. The specific preparation steps and parameters are the same as those of example 1, and the Al-1.95Mg-1.65Si-2.75Zn alloy is prepared.
Example 4
The chemical composition and the proportion of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile in the embodiment are the same as those in the embodiment 1. The preparation method comprises the following specific steps:
(1) smelting high-purity aluminum, high-purity magnesium, aluminum-silicon intermediate alloy and aluminum-zinc intermediate alloy in a vacuum smelting furnace at 680 ℃ for 0.5h, and then casting in a metal copper mold to obtain an ingot;
(2) heating the ingot obtained in the step (1) to 455 ℃ at a heating rate of 5 ℃/min, preserving heat for 8 hours, and then cooling to room temperature along with the furnace to complete primary homogenization heat treatment; then heating to 555 ℃ at the heating rate of 5 ℃/min, preserving the heat for 16h, cooling to room temperature along with the furnace, and finishing secondary homogenization heat treatment to obtain a homogenized alloy;
(3) preserving the heat of the homogenized alloy obtained in the step (2) at the temperature of 420 ℃ for 1.5h, then carrying out first-pass hot rolling at the temperature, wherein the deformation is 20%, then preserving the heat at the temperature of 420 ℃ for 4min, carrying out second-pass hot rolling along anticlockwise rotation of 60 degrees, wherein the deformation is 18%, then carrying out first-pass cold rolling after air cooling to 200 ℃, wherein the deformation is 13%, carrying out second-pass cold rolling along anticlockwise rotation of 60 degrees, and the deformation is 12%, thus obtaining an aluminum alloy blank with the thickness of 1.3 mm;
(4) and (3) preserving the heat of the aluminum alloy blank obtained in the step (3) for 0.5h at 465 ℃ for primary solution treatment, then directly heating to 555 ℃ for 0.5h for secondary solution treatment, cooling to 160 ℃ along with the furnace, preserving the heat for 1.8h, completing primary aging treatment, cooling to 130 ℃ along with the furnace again, preserving the heat for 75h, discharging from the furnace, air cooling to room temperature, and completing secondary aging treatment to obtain the Al-0.52Mg-0.59Si-3.5Zn alloy.
Example 5
The chemical composition and the proportion of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile in the embodiment are the same as those in the embodiment 1. The preparation method comprises the following specific steps:
(1) smelting high-purity aluminum, high-purity magnesium, aluminum-silicon intermediate alloy and aluminum-zinc intermediate alloy in a vacuum smelting furnace at 680 ℃ for 0.5h, and then casting in a metal copper mold to obtain an ingot;
(2) heating the ingot obtained in the step (1) to 470 ℃ at a heating rate of 6 ℃/min, preserving heat for 7.5h, and then cooling to room temperature along with the furnace to complete primary homogenization heat treatment; heating to 570 ℃ at the heating rate of 6 ℃/min, preserving the heat for 15.5 hours, cooling to room temperature along with the furnace, and finishing secondary homogenization heat treatment to obtain a homogenized alloy;
(3) preserving the heat of the homogenized alloy obtained in the step (2) at the temperature of 430 ℃ for 1.8h, then carrying out first-pass hot rolling at the temperature, wherein the deformation is 21%, then preserving the heat at the temperature of 420 ℃ for 4min, carrying out second-pass hot rolling by rotating 90 degrees anticlockwise, wherein the deformation is 19%, then carrying out first-pass cold rolling by air cooling to 230 ℃, wherein the deformation is 14%, carrying out second-pass cold rolling by rotating 70 degrees anticlockwise, and the deformation is 13%, thus obtaining an aluminum alloy blank with the thickness of 1.4 mm;
(4) and (3) preserving the heat of the aluminum alloy blank obtained in the step (3) at 475 ℃ for 0.5h to carry out primary solution treatment, then directly heating to 575 ℃ to preserve heat for 0.5h to carry out secondary solution treatment, cooling to 170 ℃ along with the furnace, preserving the heat for 1.8h to finish primary aging treatment, cooling to 110 ℃ along with the furnace again, preserving the heat for 78h, discharging from the furnace, air cooling to room temperature to finish secondary aging treatment, and obtaining the Al-0.52Mg-0.59Si-3.5Zn alloy.
Example 6
The chemical composition and the proportion of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile in the embodiment are the same as those in the embodiment 1. The preparation method comprises the following specific steps:
(1) smelting high-purity aluminum, high-purity magnesium, aluminum-silicon intermediate alloy and aluminum-zinc intermediate alloy in a vacuum smelting furnace at 680 ℃ for 0.5h, and then casting in a metal copper mold to obtain an ingot;
(2) heating the ingot obtained in the step (1) to 455 ℃ at a heating rate of 5 ℃/min, preserving heat for 8 hours, and then cooling to room temperature along with the furnace to complete primary homogenization heat treatment; then heating to 555 ℃ at the heating rate of 5 ℃/min, preserving the heat for 16h, cooling to room temperature along with the furnace, and finishing secondary homogenization heat treatment to obtain a homogenized alloy;
(3) preserving the heat of the homogenized alloy obtained in the step (2) at the temperature of 420 ℃ for 1.5h, then carrying out first-pass hot rolling at the temperature, wherein the deformation is 20%, then preserving the heat at the temperature of 420 ℃ for 4min, carrying out second-pass hot rolling along anticlockwise rotation of 60 degrees, wherein the deformation is 18%, then carrying out first-pass cold rolling after air cooling to 200 ℃, wherein the deformation is 13%, carrying out second-pass cold rolling along anticlockwise rotation of 60 degrees, and the deformation is 12%, thus obtaining an aluminum alloy blank with the thickness of 1.3 mm;
(4) and (3) preserving the heat of the aluminum alloy blank obtained in the step (3) for 0.5h at 465 ℃ for primary solution treatment, then directly heating to 555 ℃ for 0.5h for secondary solution treatment, cooling to 160 ℃ along with the furnace, preserving the heat for 2.1h, completing primary aging treatment, cooling to 100 ℃ along with the furnace again, preserving the heat for 80h, discharging from the furnace, air cooling to room temperature, and completing secondary aging treatment to obtain the Al-0.52Mg-0.59Si-3.5Zn alloy.
Comparative example 1
The chemical composition and the proportion of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile in the embodiment are the same as those in the embodiment 1. The preparation method comprises the following specific steps:
(1) smelting high-purity aluminum, high-purity magnesium, aluminum-silicon intermediate alloy and aluminum-zinc intermediate alloy in a vacuum smelting furnace at 680 ℃ for 0.5h, and then casting in a metal copper mold to obtain an ingot;
(2) heating the ingot obtained in the step (1) to 455 ℃ at a heating rate of 5 ℃/min, preserving heat for 8 hours, and then cooling to room temperature along with the furnace to complete primary homogenization heat treatment; then heating to 555 ℃ at the heating rate of 5 ℃/min, preserving the heat for 16h, cooling to room temperature along with the furnace, and finishing secondary homogenization heat treatment to obtain a homogenized alloy;
(3) and (3) preserving the heat of the homogenized alloy obtained in the step (2) at the temperature of 420 ℃ for 1.5h, then carrying out first hot rolling at the temperature with the deformation of 20%, then preserving the heat at the temperature of 420 ℃ for 4min, carrying out second hot rolling along anticlockwise rotation of 60 ℃ with the deformation of 18%, then carrying out first cold rolling in an air cooling mode to 200 ℃ with the deformation of 13%, carrying out second cold rolling along anticlockwise rotation of 60 ℃ with the deformation of 12%, and obtaining an Al-0.52Mg-0.59Si-3.5Zn alloy billet with the thickness of 1.3 mm.
The above samples are all detected under the same conditions according to GB/T228-2010 Metal Material tensile test method at Room temperature, GB/T4340-2009 Metal Material Vickers hardness test, and the experimental results of each sample are shown in Table 1.
The Al-0.52Mg-0.59Si-3.5Zn alloy obtained in example 6 of the invention was subjected to tensile property test to obtain an alloy peak aged state engineering stress-strain curve as shown in FIG. 1. As can be seen from fig. 1, the aluminum alloy sample of example 6 can withstand a stress of 300MPa or more in the elastic stage, and a maximum stress of 350MPa or more in the yield stage.
TABLE 1 mechanical Properties of the inventive and comparative examples
| Numbering | Alloy name | Yield strength (MPa) | Tensile Strength (MPa) | Hardness (HV) | Elongation (%) |
| Example 1 | Al-0.52Mg-0.59Si-3.5Zn | 320 | 339 | 127 | 16.1 |
| Example 2 | Al-2.2Mg-2.45Si-3.3Zn | 317 | 342 | 116 | 16.3 |
| Example 3 | Al-1.95Mg-1.65Si-2.75Zn | 318 | 338 | 118 | 16.5 |
| Example 4 | Al-0.52Mg-0.59Si-3.5Zn | 321 | 341 | 121 | 16.7 |
| Example 5 | Al-0.52Mg-0.59Si-3.5Zn | 325 | 355 | 119 | 15.7 |
| Example 6 | Al-0.52Mg-0.59Si-3.5Zn | 324 | 350 | 121 | 15.3 |
| Comparative example 1 | Al-0.52Mg-0.59Si-3.5Zn | 299 | 316 | 102 | 13.9 |
The detection results shown in Table 1 show that the aluminum alloy has high strength, high hardness and high plasticity by adding Zn element and adjusting the proportion of Mg and Si elements; meanwhile, by designing a preparation process matched with chemical components, each precipitated phase in the aluminum alloy matrix can realize the effect of synergistically strengthening the aluminum alloy matrix, and the mechanical property of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile is further improved.
The Al-0.52Mg-0.59Si-3.5Zn alloy obtained in the embodiment 6 of the invention is polished, corroded, washed and dried to obtain a sample to be observed in a metallographic microscope, and a TEM image obtained by observation under a transmission electron microscope is shown in FIG. 2. As can be seen from FIG. 2, the structure of the sample of example 6 of the present application is uniform and dense, and the strengthening phases are uniformly distributed in the aluminum alloy matrix in the form of dispersed particles.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. A high-strength plastic Al-Mg-Si-Zn alloy for automobiles comprises, by mass, 0.52-2.25% of Mg, 0.42-2.75% of Si, 3.35-3.53% of Zn and the balance of Al; the mass relation between Mg and Si satisfies the following condition that Mg: si is 0.85-1.25;
the preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile comprises the following steps:
(1) smelting alloy raw materials and then casting to obtain a cast ingot;
(2) sequentially carrying out primary homogenization heat treatment and secondary homogenization heat treatment on the cast ingot obtained in the step (1) to obtain a homogenized alloy;
(3) sequentially carrying out hot rolling and cold rolling on the homogenized alloy obtained in the step (2) to obtain an aluminum alloy blank;
(4) sequentially carrying out primary solution treatment and secondary solution treatment on the aluminum alloy blank obtained in the step (3) to obtain a solid solution aluminum alloy;
(5) sequentially carrying out primary aging treatment and secondary aging treatment on the solid-solution aluminum alloy obtained in the step (4) to obtain high-strength plastic Al-Mg-Si-Zn alloy for automobiles;
the heat preservation temperature of the primary aging treatment in the step (5) is 150-180 ℃, and the heat preservation time of the primary aging treatment is 1-2.5 h; the heat preservation temperature of the secondary aging treatment is 100-130 ℃, and the heat preservation time of the secondary aging treatment is 70-80 h.
2. The method for preparing a high-strength plastic Al-Mg-Si-Zn alloy for automobiles according to claim 1, comprising the steps of:
(1) smelting alloy raw materials and then casting to obtain a cast ingot;
(2) sequentially carrying out primary homogenization heat treatment and secondary homogenization heat treatment on the cast ingot obtained in the step (1) to obtain a homogenized alloy;
(3) sequentially carrying out hot rolling and cold rolling on the homogenized alloy obtained in the step (2) to obtain an aluminum alloy blank;
(4) sequentially carrying out primary solution treatment and secondary solution treatment on the aluminum alloy blank obtained in the step (3) to obtain a solid solution aluminum alloy;
(5) sequentially carrying out primary aging treatment and secondary aging treatment on the solid-solution aluminum alloy obtained in the step (4) to obtain high-strength plastic Al-Mg-Si-Zn alloy for automobiles;
the heat preservation temperature of the primary aging treatment in the step (5) is 150-180 ℃, and the heat preservation time of the primary aging treatment is 1-2.5 h; the heat preservation temperature of the secondary aging treatment is 100-130 ℃, and the heat preservation time of the secondary aging treatment is 70-80 h.
3. The preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile according to claim 2, wherein the temperature of the primary homogenizing heat treatment in the step (2) is 450-500 ℃, and the temperature of the primary homogenizing heat treatment is 7-9 hours.
4. The preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile according to claim 2, wherein the heat preservation temperature of the secondary homogenization heat treatment in the step (2) is 550-600 ℃, and the heat preservation time of the secondary homogenization heat treatment is 15-17 hours.
5. The preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile according to claim 2, wherein the step (3) further comprises heat preservation before hot rolling, the heat preservation temperature is 400-450 ℃, and the heat preservation time is 1.5-2 h.
6. The preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile according to claim 2, wherein the temperature of the primary solution treatment in the step (4) is 460-500 ℃, and the time of the primary solution treatment is 0.5-1 h.
7. The preparation method of the high-strength plastic Al-Mg-Si-Zn alloy for the automobile according to claim 2, wherein the temperature of the secondary solution treatment in the step (4) is 550-600 ℃, and the time of the secondary solution treatment is 0.5-1 h.
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