Unconventional δ-phase stabilization in Pu-Ga alloys

Face-centered cubic δ-phase Pu stabilized with less than 3 at.% Ga will partially transform martensitically to monoclinic α'-phase at cryogenic temperatures. Thermal cycling of young alloys in a dilatometer tends to stabilize δ Pu by shifting the transformation to lower temperatures and reducing the amount of transformation. Similar experiments using samples aged naturally or by doping with 238Pu will stabilize δ Pu such that annealing at or above 150 deg. C is required before normal transformation behavior occurs. We discuss the role that radiation damage and recovery play in this unconventional stabilization of δ-phase Pu