Phase transformations in ion irradiated Ti-6242s alloys

Neutron irradiation of Ti-6Al-2Sn-4Zr-2Mo-0.08Si (Ti-6242s) indicated that the microstructure of this alloy may be stable under irradiation, in contrast to Ti-6A1-4V (Ti-64) which showed radiation-induced phase instabilities. However, the present study showed that after 2 dpa of 9 MeV aluminum ion irradiation within the temperature range 450–700°C, Ti-6242s displayed extensive precipitation. The precipitate was identified as a bcc phase similar to that observed in Ti-64. The morphology of the precipitation response for 450–600°C was highly unusual. It consisted of the apparent agglomeration of small (~ 20 nm) precipitates into some form of array or cluster. The high temperature precipitate response (650–700°C) was normal in that the precipitate morphology was that of an elongated platelet. The unusual precipitate morphology is attributed to the observed segregation of Al and Mo to sinks. A low void density was observed between 550–650°C with the voids preferentially located near grain boundaries.