A Reference Hydride Ratio Method for the Resolution of Al/Fe Peak Overlapping in Atom Probe Tomography Experiments

Precise Fe concentration measurements are essential to understand the kinetics of precipitation and evolution of mechanical properties in Al-Fe alloys. Moreover, with the increasing proportion of recycled metals, it is mandatory to rely on techniques capable of tracking impurities in Al-alloys to elucidate their effects on microstructure and properties. Atom Probe Tomography (APT) is a powerful material analysis tool capable of precise composition measurements. As it relies on time-of-flight mass spectrometry, the quality of the composition measurements is highly dependent on the proper peak identification and solving peak overlapping. The complexity of peak decomposition multiplies if molecular ions such as hydrides or oxides are present in the mass spectrum. Al-Fe is one of these systems, where three out of four peaks of Fe isotopes are overlapping with Al, AlH, and AlH2 mass intervals. To solve this complex peak overlapping case, an approach has been developed here. It is based on acquiring the Al-hydride formation ratio from APT analyses of standard materials, where no overlap with Fe peaks is observed. This simple method aims to improve the precision of Fe concentration measurements in Al-Fe system.