On the fcc → monoclinic martensite transformation in a Pu-1.7 at.% Ga alloy

The face-centered cubic δ → monoclinic α′ martensite transformation in a Pu-1.7 at.% Ga alloy is analyzed in terms of the defect-based topological model. Disconnections and terrace planes for the transformation are deduced. The predicted habit plane is in good agreement with experimental results. Observed twinning is associated directly with the transformation strain. The lattice invariant deformation is connected with slip in the α′ plates. Implications for hysteresis in the transformation as observed by dilatometry and calorimetry are discussed.