Two-step Aging Treatment in Ultra-High-Strength Al-Zn-Mg-Cu Aluminum Alloy

Abstract

The parameters of duplex aging treatment of pre-stretched plates including both the temperature and the holding time of two aging stages have been systematically investigated by using electric conductivity and tensile properties tests, exfoliation corrosion experiments and TEM observations. The results show that both the first and the second age have effect on properties of plates after having been performed by different duplex aging treatments and the effect of the second age is much greater. It is found that such a duplex aging treatment is appropriate in which the temperature of the second age is 155°C and the holding time of the first and the second age is 4-6 and 28-32 hours, respectively. The ultimate strength of specimens treated with the duplex aging treatment given above can achieve 540MPa while electric conductivity is 40.5-42 %IACS.