Heat treatment method of high-strength and high-flexibility 7055 aluminum alloy

Abstract

The invention discloses a heat treatment method of a high-strength and high-flexibility 7055 aluminum alloy. The heat treatment method comprises the steps of double-stage solid solution and T6 manual aging in sequence; after the T6 manual aging step is finished, the high-temperature destressed aging is performed, that is, the insulation is performed by 8-10 hours at 140-150 DEG C; the double-stage solid solution step is to heat a product from the room temperature to 445-455 DEG C along with a furnace for insulation by 0.5-4 hours, to heat the product to 465-480 DEG C by 0.5 hour for insulation 0.5-4 hours and to quench the product at a water temperature of 40-50 DEG C; and the T6 manual aging step is to heat the product from the room temperature to 115-125 DEG C along with the furnace for insulation by 20-26 hours. The heat treatmeetn method maintains higher material strength level, can efficiently reduce residual stress of a sprayed 7055 aluminum alloy product, and meanwhile, improves comprehensive performances of the product. The heat treatment method solves the cracking problem of the product in subsequent machining process, reduces the machining deformation of the product, and improves the size precision.

Description

technical field [0001] The invention belongs to the technical field of heat treatment of nonferrous metals, and in particular relates to a heat treatment method of high-strength and high-flexibility 7055 aluminum alloy. Background technique [0002] The 7055 aluminum alloy has the characteristics of high strength and high flexibility. It is a 7XXX series (Al-Zn-Mg-Cu) aluminum alloy with Zn, Mg, and Cu as the main strengthening alloy elements. It has the highest Zn content and has low density. The advantages of high strength and good plasticity are the high-strength and high-toughness aluminum alloys widely used at present; the 7055 aluminum alloy produced by the spray forming process has the advantages of fine grain, uniform and dense structure, and no macro segregation. [0003] 7055 belongs to the heat-treatable aluminum alloy. The strength of 7055 can be greatly improved through various heat treatment systems. For example, the tensile strength of spray-formed 7055-T6 sta...

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Problems solved by technology

[0003] 7055 belongs to the heat-treatable aluminum alloy. The strength of 7055 can be greatly improved through various heat treatment systems. For example, the tensile strength of spray-formed 7055-T6 state can reach 720MPa, which is 227% higher than that of 220MPa in O state. But at the same time, heat treatment After the residual stress of the material is greatly increased, it is not suitable for use under complex working conditions such as stress corrosion and alternating loads; in order to reduce residual stress, improve toughness, stress corrosion resistance and other comprehensive properties, many heat treatment systems such as T76, T74, T73, T77 and T79 have been developed successively. In these heat treatment systems, T76, T74, and T73 are secondary overaging and the aging time of the second aging is gradually extended. With the prolongation of aging time, the residual stress of aluminum alloy products gradually increases. Reduced, stress corrosion resistance, fracture toughness, reduction of area, electrical conductivity and other indicators gradually increased, but at the same time the strength was gradually reduced

[0005] High residual stress aluminum alloy components are severely deformed or even cracked and scrapped during subsequent machining

[0006] ②In order to avoid component cracking caused by residual stress during processing, the machining process of high residual stress components is strictly restricted: for example, wire cutting cannot be used in processing methods, and the requirements for machining tool selection and feed control are more stringent than ordinary aluminum alloy components. Harsh, and the machining process is often accompanied by multi-pass low-temperature aging stress relief or shape correction, these factors reduce the production efficiency of components and increase their production costs

[0007] ③ High residual stress reduces the comprehensive performance of components. Studies have shown that high residual stress increases the crack sensitivity of components, reduces stress corrosion resistance and fatigue performance

[0008] The traditional residual stress reduction technology mainly focuses on the following aspects: mechanical stretching / compression method, low temperature aging method, and vibration aging method; among these methods, the mechanical stretching / compression method has high requirements on equipment and is difficult to control the amount of deformation. The low-temperature aging method has low efficiency and poor effect, and the technology related to the vibration aging method is not mature enough, and the mechanism research is insufficient. At present, there is no technology in the aluminum alloy residual stress reduction technology that is simultaneously efficient, practical, and easy to promote.

[0009] For 7055 aluminum alloy, if two-stage aging is adopted, that is, T76 / T74 / T73, the temperature of the first-stage aging is 120°C, and the temperature of the second-stage aging is 160°C; if artificial aging is continued after T6 peak aging, then As the artificial aging time prolongs or the temperature rises, the stress level of the alloy gradually decreases, but the traditional low temperature aging (less than 120°C) has low efficiency and poor effect, reaching or exceeding the primary aging temperature (120°C) will lead to a rapid decline in mechanical properties ; For the spray-formed 7055 aluminum alloy, there is a certain temperature range between the first-stage aging (120°C) and the second-stage aging (160°C). The insulation strength of 7055 aluminum alloy produced by continuous casting will be greatly reduced in this temperature range; in view of this characteristic, a set of high temperature aging stress relief process scheme has been developed to replace the traditional process, which can greatly improve work efficiency and stress relief effect

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