Stress Aging Research Of 7075 Aluminum Alloy

The hardness and microstructure characteristics of 7075 aluminum alloy was studied under different aging condition.Compressive stress aging, T6 aging and double aging was carried out to 7075 aluminum alloy. After that samples were researched with hardness test and transmission electron microscope and the stress aging mechanism was studied according to the solutes non-equilibrium grain boundary segregation theory. The results showed that:The hardness of samples after T6 aging was higher than that of double aging.Dispersedη' phase precipitated in the matrix with small size, grain boundary precipitates distributed continuously. After double aging, the size of precipitated phase grow bigger with PFZs of certain size.The hardness values of samples aged under 0.3σs compressive stress for different time were of little difference. Hardness values of samples aged at different compressive stress for 1 hour were varied. The sample possed the maxium hardness value and the preferable microstructure characteristics when the stress was 0.5σs. PFZs are not found in all the samples.The hardness value of sample aged for 60 min of 120℃under elastic stress fields was higher than that of T6 aging treatment. TEM microstructure showed that stress aging eliminate PFZ and inhibited GBP which was due to the non-equilibrium grain boundary segregation of solutes.