Ambient-temperature Conditioning as a Probe of Double-C Transformation Mechanisms in Pu-2.0 at. {\%} Ga.*

The gallium-stabilized Pu-2.0 at. {\%} Ga alloy undergoes a partial or incomplete low-temperature martensitic transformation from the metastable delta phase to the monoclinic alpha-prime phase near -120 $^{\circ}$C. This transformation has been shown to occur isothermally and it displays anomalous double-C kinetics in a time-temperature-transformation diagram. While the underlying mechanisms responsible for the double-C behavior are currently unresolved, recent experiments suggest that a conditioning treatment influences the upper-C. As such, the effects of the conditioning treatment can provide valuable insight into the mechanisms dominating the phase transition. A differential scanning calorimeter (DSC) is used to investigate the effects of conditioning temperature and time upon the delta/alpha-prime transition. The results will be discussed as they pertain to radiation damage, nucleation, embryo formation, or phase-field stability.