Phase transformation damage in plutonium

Abstract

Plutonium may contain a large volume of microcracks which form during the β → α transformation. The volume of microcracks increases with increasing transformation temperature, metal purity, specimen size and applied uniaxial tensile stress. Transformation cycling causes additional microcracking, with concomitant swelling in all directions and extensive surface rumpling. For a given β → α transformation temperature, more damage occurs if the parent beta was formed from alpha rather than gamma. Alpha plutonium containing no microcracks can be produced by quenching the beta phase to −75° C during casting. No physical damage occurs during γ ⇆ β, δ ⇆ γ, or δ ⇆ β transformation cycling if the metal initially contains no microcracks.