Aging heat treatment method for Al-Mg-Zn alloy

Abstract

The invention discloses a retrogression re-aging heat treatment technique suitable for Al-Mg-Zn alloy. The retrogression re-aging heat treatment technique suitable for the Al-Mg-Zn alloy comprises the steps that according to a pre-aging rule, heat preservation is conducted at the temperature of 80-220 DEG C for 15-50 h for one-stage or two-stage aging treatment, and cooling is conducted till the room temperature is reached, or furnace heating is conducted for retrogression aging; according to a retrogression aging rule, heat preservation is conducted at the temperature of 380-460 DEG C for 10 min-6 h, cooling is conducted till the room temperature is reached, and re-aging is conducted immediately; and re-aging is achieved through two sub-steps, heat preservation is conducted on the alloy at the temperature of 50-100 DEG C for 10-80 h in the first sub-step, heat preservation is conducted on the alloy at the temperature of 110-180 DEG C for 10-50 h in the second sub-step, and the alloy is cooled to the room temperature. According to the retrogression re-aging heat treatment technique suitable for the Al-Mg-Zn alloy, through the heat treatment way including pre-aging, high-temperature short-time retrogression and re-aging, the microstructure of the Al-Mg-Zn alloy can be obviously improved, a dispersing T-Mg32(AlZn)49 phase can be evenly separated out from the crystal of the alloy, the T-Mg32(AlZn)49 phase on the crystal boundary is distributed in an interrupted mode, and thus high strength is maintained; meanwhile, the intercrystalline corrosion resistance of the alloy is greatly improved, and the retrogression re-aging heat treatment technique has important reference value for developing novel high-strength and corrosion-resistant alloy for ships and armors.

Description

technical field [0001] The invention belongs to the technical field of aluminum alloy heat treatment, and in particular relates to an aging heat treatment method for improving the corrosion resistance of aluminum alloy and maintaining its strength. Background technique [0002] 5xxx series aluminum alloys are aluminum alloys with magnesium as the main alloying element. This series of alloys is an anti-rust aluminum alloy and cannot be strengthened by heat treatment. The alloy can only be strengthened by solid solution strengthening of Mg element and cold work hardening. This series of aluminum alloys belongs to medium and high-strength aluminum alloys, with good fatigue resistance and welding performance, and good corrosion resistance in marine atmospheres; they are mainly used as armor plates, structural materials for ships and automotive interior materials, and are widely used. However, when the Mg content exceeds 3%, Mg atoms will preferentially precipitate at the grain b...

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Problems solved by technology

[0003] For 7xxx series aluminum alloys, the early alloys used peak aging (T6) heat treatment, but their corrosion resistance was not good, so material workers developed an overaging (T7X) heat treatment process in the 1960s, which greatly improved the performance of aluminum alloys. The resistance to stress corrosion and exfoliation corrosion, but compared with the T6 state alloy, its strength is reduced by 10%-15%

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