Spallation　of　thermal　oxidation-induced　cavities　is　the　main　failure　mode　in　CoAl-based　alloys,　and　the　gamma/gamma＇　phase　structure　in　Co-Al-W-Ti-Ta　alloys　has　a　propensity　to　form　oxide　cavities.　Multidimensional　investigations　were　carried　out　herein　on　irregular　oxide　cavities　by　analytical　microscopy,　including　electron　tomography　and　energy　dispersive　X-ray　spectroscopy　techniques,　to　disclose　the　time-resolved　three-dimensional　morphological　structure　and　elemental　distributions.　The　alloy　nanotip　was　exposed　isothermally　in　air　at　350　degrees　C,　and　its　oxidation　evolution　was　characterized　and　analysed.　The　size　and　quantities　of　cavities　in　the　gamma　phase　were　larger　than　those　in　the　gamma＇　phase,　which　was　attributed　to　the　higher　content　of　cobalt　in　the　gamma　phase　than　in　the　gamma＇　phase.　Different　migration　rates　between　cobalt　outward　and　aluminium　inward　prompted　the　formation　of　cavities　between　the　outer　and　inner　layers.　(C)　2020　Elsevier　B.V.　All　rights　reserved.