Nucleation and evolution of β phase and corresponding intergranular corrosion transition at 100–230 °C in 5083 alloy containing Er and Zr

Abstract

Abstract The intergranular corrosion and β phase evolution of 5083 aluminum alloy containing Er and Zr during annealing at 100–230\u202f°C were studied using mass loss tests and transmission electron microscopy. The mass loss curves showed that when annealing temperature changed from 200 to 220\u202f°C, the alloy was subjected to a transition from sensitized state to stabilized state, corresponding to the change of nucleation position of β precipitates from grain boundaries to triple junctions. Particularly, when the annealing temperature was at 210\u202f°C, this transition could also happen when the annealing time was increased from 0.5-10\u202fh to 15-24\u202fh, associated with the change in the shape of β precipitates. The classical nucleation analysis with the consideration of Mg segregation showed the nucleation rates at grain boundary and triple junction were 1013 and 1011\u202fm−3\u202fs−1 at sensitization temperature 150\u202f°C, but 109 and 1010\u202fm−3\u202fs−1 at stabilization temperature 220\u202f°C, suggesting the change of nucleation site with increasing temperature. The analysis of diffusion flux of Mg around β precipitate suggested that the shape change of β precipitates from elongate to spheroidal at 210\u202f°C was attributed to the dominant interface diffusion over the grain boundary diffusion with the increase of time.