Ga-induced delithiation of grain boundaries in a Li containing Al-based alloy

The investigation of Li containing materials is of crucial importance for a number of material applications, including aerospace engineering. The aluminum alloy (AA) 2050, containing 2.7-5.0 at.% of Li, exhibits a lower density as well as excellent mechanical properties, due to the variety of phases that can form, including metastable ones. The high chemical composition sensitivity and near-atomic spatial resolution in three-dimensions of atom probe tomography make it a powerful technique to accurately assess solute partitioning and phase composition in particular at structural defects such as dislocations and grain boundaries. However, Li quantification is not straightforward due to its fast diffusion. Here, specimen preparation and Li electric field driven migration during atom probe analysis are investigated separately to better address the challenges associated with the experimental investigation of Li content in Li containing Al-alloys. We demonstrate a striking effect of Ga on Li distribution, which turns out to be significantly more critical than the electric field induced migration of Li during the atom probe tomography analysis.