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

The intergranular corrosion and phase evolution of 5083 aluminum alloy containing Er and Zr during annealing at 100-230 degrees 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 degrees C, the alloy was subjected to a transition from sensitized state to stabilized state, corresponding to the change of nucleation position of beta precipitates from grain boundaries to triple junctions. Particularly, when the annealing temperature was at 210 degrees C, this transition could also happen when the annealing time was increased from 0.5-10 h to 15-24 h, associated with the change in the shape of beta precipitates. The classical nucleation analysis with the consideration of Mg segregation showed the nudeation rates at grain boundary and triple junction were 10(13 )and 10(11 )m(-3) s(-1) at sensitization temperature 150 degrees C, but 10(9) and 10(10) m(-3) s(-1) at stabilization temperature 220 degrees C, suggesting the change of nucleation site with increasing temperature. The analysis of diffusion flux of Mg around beta precipitate suggested that the shape change of beta precipitates from elongate to spheroidal at 210 degrees C was attributed to the dominant interface diffusion over the grain boundary diffusion with the increase of time. (C) 2019 The Authors. Published by Elsevier Ltd.