These data relate to the figures within the associated manuscript. Data are provided for the four alloys studied, with varying Al:Nb ratio across the alloy series. These data include scanning electron microscopy images (.tiff files) obtained from the four alloys after two different thermal exposures, in addition to X-ray diffraction data (.txt files). Energy dispersive X-ray spectroscopy data is included as a .oip file, which can be opened using the proprietary Oxford Instruments AZtec software. The associated data necessary for AZtec to read this file is contained in the corresponding .dat files. The normalised mass gain data used to produce the discontinuous mass gain graphs are also provided in the form of a spreadsheet (.xlsx file).