The Effect Of High Temperature Pre-precipitation On The Microstructure And Properties Of 7055 Aluminum Alloy

The development of Al-Zn-Mg-Cu series high-strength aluminum alloys tends to improve stress corrosion endurance with high strength. So far, high-strength aluminum alloy has fairly high strength, but its stress corrosion cracking resistance needs to be further enhanced.Near-solution-temperature pre-precipitation was explored to improve synthetic properties of 7055 aluminum alloy, especially stress corrosion cracking resistance, since the high temperature pre-precipitation can be supposed to incur local grain boundary pre-precipitation under small driving force. The effects of high temperature pre-precipitation near solution treatment temperature on the microstructure and properties of 7055 high strength aluminum alloy have been investigated by means of optical microscopy, TEM analysis and the measurement of mechanical properties, -electrical conductivity and corrosion properties.The precipitation microstructure of 7055 aluminum alloy could be changed by high temperature pre-precipitation. The near-solution- temperature pre-precipitation mainly limited to grain boundary without pre-precipitating in grain, and increased the disconnection and particle size of grain boundary precipitates in subsequent ageing process.The dependences of the properties of 7055 aluminum alloy on high temperature pre-precipitation have been investigated. Contrasted to normal processing, the addition of high temperature pre-precipitation could enhance the electrical conductivity of 7055 alloy with the same high hardness, and enhance the stress corrosion cracking resistance of 7055 alloy with the same high strength.