Determining the distribution of alloying elements, particularly lithium, is crucial for a holistic understanding of magnesium-lithium-based alloys. In this work, a bespoke ratio spectrum-imaging method based on electron energy-loss spectroscopy, in combination with time-of-flight secondary ion mass spectrometry, energy-dispersive X-ray spectroscopy and Z-contrast imaging, was applied to an as-rolled LAZ941 alloy (Mg-9Li-4Al-1Zn in wt.%). This was done to characterize the distribution of alloying elements, including the distribution of solute in the magnesium matrix. The applications of different mapping techniques revealed that precipitates with two different morphologies are rich in Li, Al and Zn, compared to their surrounding matrix. Additionally, it was confirmed that the β-phase of the alloy contains higher Li and lower Mg concentrations when compared to the α-phase. This study demonstrated the effectiveness and accuracy of the ratio spectrum-imaging method for mapping the elemental distribution (including lithium) in a range of Li-containing materials.

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.