Crystallography of the δ → α phase transformation in a Pu-Ga alloy

The crystallography of the δ → α phase transformation in a Pu nominally 1.0 wt% Ga alloy was examined through the application of transmission electron microscopy (TEM), giving new insight into the martensitic nature of the transformation. This transformation is of particular interest because of its unusually large volume change of ∼ 20%. A survey of twinning in α-Pu has shown that the compound twinning system requires the lowest shear and no lattice shuffling in a pseudo-structure closely related to α-Pu. Upon application of these experimentally determined parameters to established martensite crystallographic theory, it has been shown that a reasonable solution is obtained. Results strongly suggest transformation occurs via a martensitic mechanism despite the large volume change