Effect of ultrasonic casting on microstructure and its genetic effects on corrosion performance of 7085 aluminum alloy

Abstract

The effect of ultrasonic casting on microstructure and its genetic effects on strength, exfoliating corrosion, stress corrosion and electrochemical behavior of 7085 aluminum alloy have been investigated by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM), together with tensile testing, exfoliation corrosion testing, electrical conductivity testing and polarization curve. The results indicate that ultrasonic casting could refine the grain, alleviate segregation and inhibit the formation of coarse nonequilibrium phase in as-cast state; in addition, the dissolution of nonequilibrium phase in the ultrasonic ingot during homogenization turns out to be more thorough. What is more, the plate processed from ultrasonic ingot holds a lower ratio of recrystallization after solid solution, and the corrosion performance of the alloy was improved under T6 temper, without sacrifice of strength, owing to the dispersive distribution of strengthening phase in the matrix and the coarse, sparse GBPs.