  Imaging individual vacancies in solids and revealing their interactions with
solute atoms remains one of the frontiers in microscopy and microanalysis. Here
we study a creep-deformed binary Ni-2 at.% Ta alloy. Atom probe tomography
reveals a random distribution of Ta. Field ion microscopy, with contrast
interpretation supported by density-functional theory and time-of-flight mass
spectrometry, evidences a positive correlation of tantalum with vacancies. Our
results support solute-vacancy binding, which explains improvement in creep
resistance of Ta-containing Ni-based superalloys and helps guide future
material design strategies.
