The distribution of T 1 precipitates at the subgrain boundaries and the nucleation of secondary precipitates in the alloy aluminum lithium 2090 have been studied using TEM. The results show that the aspect ratios of the T 1 phase particles which precipitate at the subgrain boundaries is similar to or even smaller than those of nearby T 1 phases, indicating limited coarsening of the T 1 phase. It is calculated that this result conforms to the Perovic criterion, i.e. that it is necessary to balance the elastic interaction energy among the T 1 precipitates in order to stabilize the distribution of the T 1 precipitates. Small T 1 precipitates always appear at the intersection between existing T 1 phases where the nucleation energy of the T 1 phase is lower