Microstructure and mechanical properties of a new type Al-Zn-Mg-Cu alloy profile after secondary aging treatment

Effects of different secondary aging treatments on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy profile were studied.The results show that after 135 ℃×6 h+85 ℃×120 h treatment,the tensile strength,yield strength,elongation and electrical conductivity of the alloy profile are 614.5 MPa,561.5M Pa,14.3% and 34.2%IACS respectively.Compared to T6 state,the yield strength and elongation are increased obviously.The major precipitates in the alloy profile are η′ phase and a little big size GP zone.After 135 ℃×6 h+85 ℃×120 h+135 ℃×20 h treatment,the tensile strength,yield strength,elongation and electrical conductivity of alloy profile are 616 MPa,586 MPa,12.8% and 36.7%IACS respectively.Compared to T6 state,the yield strength and the stress corrosion cracking resistance of the alloy are increased obviously.The major precipitates in the alloy profile are η′ phase and a little η phase.