ON THE LATTICE CORRESPONDENCE OF THE delta yields alpha DISPLACIVE TRANSFORMATION IN PLUTONIUM ALLOYS.

Although the low temperature delta yields alpha transformation which occurs on cooling or deformation of plutonium alloys exhibits many of the characteristics of a martensitic transformation, classification of the transformation according to recent taxonomy and elucidation of its crystallographic characteristics have been hampered by the lack of a clear correspondence and lattice deformation relating the fcc delta and monoclinic alpha structures. The transformation represents an interesting test case of crystallographic concepts because of its unusually large volume concentration of about 20%. We explore here possible lattice correspondences consistent with this contraction, and examine the classification of this displacive transformation based on the characteristics of the associated lattice deformations.