Effect of stress on precipitation behaviour of 7xxx alloy during age forming process

Abstract

In the present paper, the effect of stress on precipitation behaviour, which decides the strength of 7xxx alloy, has been investigated through a comparative analysis of the difference in precipitation behaviour in 7050 alloy treated by age forming and traditional aging. The results suggest that the stress can enhance precipitate nucleation and growth in age forming, which mainly attributes to two reasons. First, the increased diffusion coefficient caused by applied stress field in age forming induces precipitates to growth. Second, in age forming, obvious dislocation movement caused by initial stress supplied short circuit diffusion passway and nucleation interface is of benefit to the precipitate nucleation and growth. Besides, the promoting precipitation effect decays gradually with stress relaxation during the age forming process.