Leap microscopes look at TiAl alloys

The role of oxygen in the formation of nanoscale features was studied in TiAl alloy using LEAP microscopy. The alloy was annealed at 1250°C (2280°F), followed by quenching and aging at 800°C (1470°F) for 24 hours, to capture the initial stages of carbide growth. LEAP mapping revealed that the oxygen concentration within the carbide precipitate is similar to that of carbon, such that its stoichiometry is Ti48Al4W1C23O24. Oxycarbides were also found to exist for the perovskite Ti 3AlC and hexagonal Ti2AlC type carbides. Oxygen concentrations were measured to be between 8 and 14 at.%, revealing Ti3(Al,C,O) and Ti2Al(C,O) oxycarbides, respectively. These results are consistent with previous findings which show that oxygen partitions strongly to ceramic-type strengthening precipitates.