Lithium mapping in a Mg-9Li-4Al-1Zn alloy using electron energy-loss spectroscopy

Magnesium-lithium alloys with high lithium content have been attracting significant attention because of their low density, high formability and corrosion resistance. These properties are dependent on the distribution of lithium, which is difficult to map in the presence of magnesium. In this work, a ratio spectrum-imaging method with electron energy-loss spectroscopy (EELS) is demonstrated, which enables the mapping of lithium. In application to LAZ941 (Mg-9Li-4Al-1Zn in wt.%), this technique revealed that a key precipitate in the microstructure, previously thought by some to be Mg₁₇Al₁₂, is in fact rich in lithium. This result was corroborated with a structural investigation by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), showing this phase to be Al_1-xZn_xLi, with x<<1. This work indicates the potential offered by this technique for mapping lithium in materials.